VanDeGraaffGenerator : Messages : 1665-1694 of 3058

I have been tossing around the idea that it may be better to make the
base of a VDG out of a conductive enclosure similar to the upper
terminal.

It just seems that this would ensure maximum charge transfer of the
lower brush in the same way that the upper enclosure ensures maximum
charge transfer on the upper brush.  I have only seen a few units
(mostly commercial) that have a conductive base, but it seems like it
would make a worthwhile experiment.  I have a suspicion that this
would have little effect on a unit that has a HVDC supply.

I think I may experiment with my machine by just placing the whole
thing in some kind of grounded metal box (decent gauge aluminum) with
a hole in it for the column.  Who knows, it may work.

#1666

From: "Richard R. Linder" <linder@...>
Date: Thu Nov 2, 2006 10:30 pm
Subject: Re: A question about the base material of a VDG

tibia32

Craig:

There are some commercial VDGs on the web that go both ways. I would suggest that the shape of a conductive shroud would be optimum if it were a mirror image of the bottom half of the top terminal, namely a hemisphere with an involute hole for the column. I would not spend any time or money on any kind of a conductive lower shroud that had any surface feature that even resembled an edge or corner facing in the upward direction.

You can get more bang for the buck by increasing the conveyance of electrons up to the top terminal. This would include incorporating a higher belt speed, belt width and optimizing the belt material to be complementary with the roller material. At 60 mph and a belt width of 6" I can easily generate over 100 microamps of charging current.

Dick Linder

#1667

From: "jthandbook" <jthandbook@...>
Date: Fri Nov 3, 2006 11:51 am
Subject: Is longer better for belt length?

jthandbook

Does anyone have any information on optimal belt length?
I understand the desire for wide and fast belts (expressed as square inches per
minute
contact between belt and roller) but beyond the minimum distance to avoid spark
over
between pos and neg terminals is longer better?
If so to what upper limit? And why?
For example I've never seen a belt running over six rollers in a Z pattern which
would allow a
tripling of belt length over a given column height.
Wouldn't a shorter belt allow for less belt leakage?
Thanks for your ideas and best, JT

#1668

From: Elmer Wiersma <elmer.wiersma@...>
Date: Fri Nov 3, 2006 12:28 pm
Subject: Re: Is longer better for belt length?

elmerwiersma

I think that our homemade VDG are not really usefull with that six roller design, first off there is the problem of the belts touching each other and the huge hole you got to have in your terminal and then setting up all 6 rollers to let the belt run correctly has some huge adjusting difficulties as it can be tricky just to set up for 2 rollers let alone 6

the belt length helps in seperating the distance between the bottom and upper brush and terminal, but there is the problem with the longer the belt gets the more belt tension you got to have to stop the up going and down going parts of the belt touching each other and if the belt is very stretchy it will need a lot of tension, a longer belt would allow you I think to run the machine at a lower speed since there is more belt to go over the roller at 1 whole revolution and so more charge.

Elmer

----- Original Message -----

From: jthandbook

To: VanDeGraaffGenerator@yahoogroups.com

Sent: Friday, November 03, 2006 12:51 PM

Subject: [VanDeGraaffGenerator] Is longer better for belt length?

Does anyone have any information on optimal belt length?
I understand the desire for wide and fast belts (expressed as square inches per minute
contact between belt and roller) but beyond the minimum distance to avoid spark over
between pos and neg terminals is longer better?
If so to what upper limit? And why?
For example I've never seen a belt running over six rollers in a Z pattern which would allow a
tripling of belt length over a given column height.
Wouldn't a shorter belt allow for less belt leakage?
Thanks for your ideas and best, JT

#1669

From: "Richard R. Linder" <linder@...>
Date: Fri Nov 3, 2006 6:59 pm
Subject: Re: Is longer better for belt length?

tibia32

Re: Belt length.

Belt length would typically be determined by column height which must accommodate the desired terminal voltage.

The problem of opposite sides touching involves at least three parameters: 1. The stretchiness of the belt material, 2. The distance between the top and bottom rollers and 3. the diameters of the rollers. I did a lot of experimenting with these three parameters and, for my two VDGs, found belt material that would not stretch more than a few tenths of one percent (that's almost imperceptable) is ideal. The only problem is that the rollers must have only a slight crown because the materal will not wrap around a typical crowned roller and therefore will not track properly. I crowned my rollers in the lathe using a flat file. The roller dimensions on my small and large VDG are 2" x 4" and 3" x 6" respectively.

Frankly, I had an awful time with belts made of latex, leather, vinyl etc. Even when I increaed the material significantly, hoping to get rid of the belt sides touching, I ran into tracking issues because the heavier belts tended to lift off the rollers due to centrifugal force, not to mention the additional horsepower required.

In the context of JT's post I don't think there is any limit to the length of the column/belt as long as the sides do not touch. Having said that, obviously there is no sense in making a 10' tall VDG if you're only going to have a 15" sphere at the top.

I think if you start a design by determining the desired terminal voltage, you will then know the HV terminal diameter and the approximate height of the column. For reference my small VDG has a 4" diameter column and the big VDG and equivalent of an 8" diameter column. However, in fact, there is no column. The HV terminal is supported on four fiberglass posts.

See my pictures

Hope some of this chatter helps.

Dick Linder

#1670

From: "jthandbook" <jthandbook@...>
Date: Sat Nov 4, 2006 1:54 pm
Subject: More Belt Length and a roller question

jthandbook

Thank you Elmer and Dick for your info. I wasn't suggesting a six roller design
(I think you
are right Elmer, way too many complications!) rather I was using it as a demo
for why I didn't
think longer belts were always better or they would be configured for use.
Dick, do I understand you to mean that column height should be great enough to
avoid spark
over (your reference to terminal voltage) and that is the determining factor?
I did find a reference on the website of the estimable Antonio Carlos M. de
Queiroz   http://
www.coe.ufrj.br/~acmq/myvdg.html   where he writes:
"The length of the belt, or the height of the terminal, have no influence if the
motor speed is
constant (except for insulation, and a small effect on the output voltage, not
considered). The
length L appears in the formula for the current in the form I = e0EmaxWLn, where
n is the
number of belt turns per second. The power is then P = e0Emax2rWLn "
The full article expands on theory and the math behind.
Now to my roller question. My VDG has rollers 3.5 long x 1.5 in diameter at the
thickest.
Diameter is determined by what I can reasonably turn on my Unimat lathe (and
this relatively
small diameter is what motivated my question about belt length, my wanting to
avoid the belt
attracting itself midcolumn).
To date I've aluminum, teflon, and delrin rollers and I am planning a nylon.
However I came
across a reference which noted that nylon is prone to extremely high voltage
leakage.
Has anyone any information on this?
Thanks and best, JT

#1671

From: "Richard R. Linder" <linder@...>
Date: Sat Nov 4, 2006 4:30 pm
Subject: Re: More Belt Length and a roller question

tibia32

JT:

I am using Nylon for my bottom rollers and Teflon for the upper in the small VDG and white PVC (plumbing style) for the top in the big VDG. The big one's charging current is in excess of 100uA so I have no complaints. Of course there are many chemical variants of nylon and they probably have different electrical characteristics.

Cosindering all the obscure variables that are involved in these beasts I often wonder if any of us have ever yet achieved the perfect combination of materials, not to mention that elusive issue of the re-entrant anti-corona involute aka hole in the HV sphere!

DIck

----- Original Message -----

From: jthandbook

To: VanDeGraaffGenerator@yahoogroups.com

Sent: Saturday, November 04, 2006 8:54 AM

Subject: [VanDeGraaffGenerator] More Belt Length and a roller question

Thank you Elmer and Dick for your info. I wasn't suggesting a six roller design (I think you
are right Elmer, way too many complications!) rather I was using it as a demo for why I didn't
think longer belts were always better or they would be configured for use.
Dick, do I understand you to mean that column height should be great enough to avoid spark
over (your reference to terminal voltage) and that is the determining factor?
I did find a reference on the website of the estimable Antonio Carlos M. de Queiroz http://
www.coe.ufrj.br/~acmq/myvdg.html where he writes:
"The length of the belt, or the height of the terminal, have no influence if the motor speed is
constant (except for insulation, and a small effect on the output voltage, not considered). The
length L appears in the formula for the current in the form I = e0EmaxWLn, where n is the
number of belt turns per second. The power is then P = e0Emax2rWLn "
The full article expands on theory and the math behind.
Now to my roller question. My VDG has rollers 3.5 long x 1.5 in diameter at the thickest.
Diameter is determined by what I can reasonably turn on my Unimat lathe (and this relatively
small diameter is what motivated my question about belt length, my wanting to avoid the belt
attracting itself midcolumn).
To date I've aluminum, teflon, and delrin rollers and I am planning a nylon. However I came
across a reference which noted that nylon is prone to extremely high voltage leakage.
Has anyone any information on this?
Thanks and best, JT

#1672

From: Elmer Wiersma <elmer.wiersma@...>
Date: Sun Nov 5, 2006 4:26 pm
Subject: Re: More Belt Length and a roller question

elmerwiersma

for rollers I heard you can also use plexiglas, I am planning to make mine from plexiglas and siliconerubber, I now plexiglas is a bit strange in the triboelectric series, some say it is the most positive stuff around and some just half way between neutral and most negative. But the handy thing is that you do not got to work it with a lath, because you can buy "acrylic plastic casting" from EMS ( http://www.emsdiasum.com/microscopy/products/chemicals/acetate.aspx#24210 ), this stuff is liquid plexiglas monomer and when you ad a hardener and you get solid plexiglas in any shape, and siliconerubber is also available in liquid form so when you have made a mould from a master form you can cast as many roller as you want/need.

Elmer

----- Original Message -----

From: Richard R. Linder

To: VanDeGraaffGenerator@yahoogroups.com

Sent: Saturday, November 04, 2006 5:30 PM

Subject: Re: [VanDeGraaffGenerator] More Belt Length and a roller question

JT:

I am using Nylon for my bottom rollers and Teflon for the upper in the small VDG and white PVC (plumbing style) for the top in the big VDG. The big one's charging current is in excess of 100uA so I have no complaints. Of course there are many chemical variants of nylon and they probably have different electrical characteristics.

Cosindering all the obscure variables that are involved in these beasts I often wonder if any of us have ever yet achieved the perfect combination of materials, not to mention that elusive issue of the re-entrant anti-corona involute aka hole in the HV sphere!

DIck

----- Original Message -----

From: jthandbook

To: VanDeGraaffGenerator@yahoogroups.com

Sent: Saturday, November 04, 2006 8:54 AM

Subject: [VanDeGraaffGenerator] More Belt Length and a roller question

Thank you Elmer and Dick for your info. I wasn't suggesting a six roller design (I think you
are right Elmer, way too many complications!) rather I was using it as a demo for why I didn't
think longer belts were always better or they would be configured for use.
Dick, do I understand you to mean that column height should be great enough to avoid spark
over (your reference to terminal voltage) and that is the determining factor?
I did find a reference on the website of the estimable Antonio Carlos M. de Queiroz http://
www.coe.ufrj.br/~acmq/myvdg.html where he writes:
"The length of the belt, or the height of the terminal, have no influence if the motor speed is
constant (except for insulation, and a small effect on the output voltage, not considered). The
length L appears in the formula for the current in the form I = e0EmaxWLn, where n is the
number of belt turns per second. The power is then P = e0Emax2rWLn "
The full article expands on theory and the math behind.
Now to my roller question. My VDG has rollers 3.5 long x 1.5 in diameter at the thickest.
Diameter is determined by what I can reasonably turn on my Unimat lathe (and this relatively
small diameter is what motivated my question about belt length, my wanting to avoid the belt
attracting itself midcolumn).
To date I've aluminum, teflon, and delrin rollers and I am planning a nylon. However I came
across a reference which noted that nylon is prone to extremely high voltage leakage.
Has anyone any information on this?
Thanks and best, JT

#1673

From: "Richard R. Linder" <linder@...>
Date: Sun Nov 5, 2006 8:00 pm
Subject: Re: More Belt Length and a roller question

tibia32

Elmer:

If you are planning to run a high speed belt, I am not sure you can easily cast a solid cylinder and then drill a hole for a shaft AND wind up with a dynamically balanced assembly.

I found it necessary to take the roller/shaft assembly and chuck it in a lathe by the shaft and turn the O.D. concentric with the shaft.

Watch out for the shaft heating up due to bearing friction. It will soften the plexi.

Dick

----- Original Message -----

From: Elmer Wiersma

To: VanDeGraaffGenerator@yahoogroups.com

Sent: Sunday, November 05, 2006 11:26 AM

Subject: Re: [VanDeGraaffGenerator] More Belt Length and a roller question

for rollers I heard you can also use plexiglas, I am planning to make mine from plexiglas and siliconerubber, I now plexiglas is a bit strange in the triboelectric series, some say it is the most positive stuff around and some just half way between neutral and most negative. But the handy thing is that you do not got to work it with a lath, because you can buy "acrylic plastic casting" from EMS ( http://www.emsdiasum.com/microscopy/products/chemicals/acetate.aspx#24210 ), this stuff is liquid plexiglas monomer and when you ad a hardener and you get solid plexiglas in any shape, and siliconerubber is also available in liquid form so when you have made a mould from a master form you can cast as many roller as you want/need.

Elmer

----- Original Message -----

From: Richard R. Linder

To: VanDeGraaffGenerator@yahoogroups.com

Sent: Saturday, November 04, 2006 5:30 PM

Subject: Re: [VanDeGraaffGenerator] More Belt Length and a roller question

JT:

I am using Nylon for my bottom rollers and Teflon for the upper in the small VDG and white PVC (plumbing style) for the top in the big VDG. The big one's charging current is in excess of 100uA so I have no complaints. Of course there are many chemical variants of nylon and they probably have different electrical characteristics.

Cosindering all the obscure variables that are involved in these beasts I often wonder if any of us have ever yet achieved the perfect combination of materials, not to mention that elusive issue of the re-entrant anti-corona involute aka hole in the HV sphere!

DIck

----- Original Message -----

From: jthandbook

To: VanDeGraaffGenerator@yahoogroups.com

Sent: Saturday, November 04, 2006 8:54 AM

Subject: [VanDeGraaffGenerator] More Belt Length and a roller question

Thank you Elmer and Dick for your info. I wasn't suggesting a six roller design (I think you
are right Elmer, way too many complications!) rather I was using it as a demo for why I didn't
think longer belts were always better or they would be configured for use.
Dick, do I understand you to mean that column height should be great enough to avoid spark
over (your reference to terminal voltage) and that is the determining factor?
I did find a reference on the website of the estimable Antonio Carlos M. de Queiroz http://
www.coe.ufrj.br/~acmq/myvdg.html where he writes:
"The length of the belt, or the height of the terminal, have no influence if the motor speed is
constant (except for insulation, and a small effect on the output voltage, not considered). The
length L appears in the formula for the current in the form I = e0EmaxWLn, where n is the
number of belt turns per second. The power is then P = e0Emax2rWLn "
The full article expands on theory and the math behind.
Now to my roller question. My VDG has rollers 3.5 long x 1.5 in diameter at the thickest.
Diameter is determined by what I can reasonably turn on my Unimat lathe (and this relatively
small diameter is what motivated my question about belt length, my wanting to avoid the belt
attracting itself midcolumn).
To date I've aluminum, teflon, and delrin rollers and I am planning a nylon. However I came
across a reference which noted that nylon is prone to extremely high voltage leakage.
Has anyone any information on this?
Thanks and best, JT

#1674

From: Elmer Wiersma <elmer.wiersma@...>
Date: Sun Nov 5, 2006 9:45 pm
Subject: rollers

elmerwiersma

Dick

the stuff from EMS here is pretty expensive so i am searching a lot for the right materials to make my rollers, since my father has a lathe but it is very old and is hard to work on it is difficult to lathe something, I was searching for something to cast it, you are right though that the shaft has to be dead centre for the whole thing to be stable and that can be pretty difficult. Maybe the acrylic plastic casting is probably even more expensive, I can make 2 rollers for the same price of 10 rollers of nylon, but I thought it would be eassier to cast then to machine

how did you lathe your rollers, I know you used a file but did you have to use any thing else to smooth the scratches out or were you carefull enough to have no scratches.

Elmer

----- Original Message -----

From: Richard R. Linder

To: VanDeGraaffGenerator@yahoogroups.com

Sent: Sunday, November 05, 2006 9:00 PM

Subject: Re: [VanDeGraaffGenerator] More Belt Length and a roller question

Elmer:

If you are planning to run a high speed belt, I am not sure you can easily cast a solid cylinder and then drill a hole for a shaft AND wind up with a dynamically balanced assembly.

I found it necessary to take the roller/shaft assembly and chuck it in a lathe by the shaft and turn the O.D. concentric with the shaft.

Watch out for the shaft heating up due to bearing friction. It will soften the plexi.

Dick

.

#1675

From: "Richard R. Linder" <linder@...>
Date: Sun Nov 5, 2006 10:02 pm
Subject: Re: rollers

tibia32

Elmer:

I have an old Sears Roebuck lathe and used common lathe tools to turn the roller concentric with the shaft. I used a series of files (medium to fine) only to create the slight crown needed for my non-stretch vinyl impregnated nylon belt.

Dick

----- Original Message -----

From: Elmer Wiersma

To: VanDeGraaffGenerator@yahoogroups.com

Sent: Sunday, November 05, 2006 4:45 PM

Subject: [VanDeGraaffGenerator] rollers

Dick

the stuff from EMS here is pretty expensive so i am searching a lot for the right materials to make my rollers, since my father has a lathe but it is very old and is hard to work on it is difficult to lathe something, I was searching for something to cast it, you are right though that the shaft has to be dead centre for the whole thing to be stable and that can be pretty difficult. Maybe the acrylic plastic casting is probably even more expensive, I can make 2 rollers for the same price of 10 rollers of nylon, but I thought it would be eassier to cast then to machine

how did you lathe your rollers, I know you used a file but did you have to use any thing else to smooth the scratches out or were you carefull enough to have no scratches.

Elmer

----- Original Message -----

From: Richard R. Linder

To: VanDeGraaffGenerator@yahoogroups.com

Sent: Sunday, November 05, 2006 9:00 PM

Subject: Re: [VanDeGraaffGenerator] More Belt Length and a roller question

Elmer:

If you are planning to run a high speed belt, I am not sure you can easily cast a solid cylinder and then drill a hole for a shaft AND wind up with a dynamically balanced assembly.

I found it necessary to take the roller/shaft assembly and chuck it in a lathe by the shaft and turn the O.D. concentric with the shaft.

Watch out for the shaft heating up due to bearing friction. It will soften the plexi.

Dick

.

#1676

From: Dan Robinson <dan@...>
Date: Sun Nov 5, 2006 11:00 pm
Subject: Bearings and big motor safety

dan831wv

I'm curious to hear what those of you with large generators and high-speed belts
are using for bearings.   I once tried using a bicycle wheel bearing on the
lower roller, but it failed rather quickly once I began operating it under belt
tension.  Without the belt it worked fine.

That brings up another safety issue with high-speed belts and these heavy-duty
motors.  A lot of these big motors will not stop for anything.  Instead of them
bogging down upon encountering resistance, they will just keep going full-speed
and destroy whatever item is resisting it.  When the said bearing above failed,
it nearly destroyed my entire lower assembly because the motor never missed a
beat.  Any individual VDG component failure with these motors can result in some
catastrophic results especially if the belt holds together and gets wrapped
around the shaft.  Fingers and hands that get caught in such an event would not
fare well.

Dan
--------------------------------------------------------
wvlightning.com | stormscenes.com | appalachianskies.com

Phone: 304-610-1374     |     Email: video@...

"We have this treasure in earthen vessels, to show that
this power is from God, and not from us"
- 2 Corinthians 4:7
--------------------------------------------------------



--
No virus found in this outgoing message.
Checked by AVG Free Edition.
Version: 7.1.409 / Virus Database: 268.13.28/518 - Release Date: 11/4/2006

#1677

From: Elmer Wiersma <elmer.wiersma@...>
Date: Mon Nov 6, 2006 1:56 pm
Subject: Re: rollers

elmerwiersma

Dick

Did you have some sort of clamp on both sides to hold the axis in place, because most lathes I see have a big clamp on one side (3 or 4 clamps, clawplate) and a pointed centre on the other end, I did try to lathe something on my dad's machine but because it was so difficult to get the centre right in the middle it was not a great success.

Did you also had a centre on 1 end and if so how did you made sure that the centre was truly centre with the shaft, in my first attempt I drilled a whole in the axis where the point of the centre would push in but it was not centred enough. I just thought of something to make a bearing which holds the shaft so I do not have to use the centre only problem is then to get bearing hole exactly in the centre of the shaft.

Elmer

#1678

From: "Richard R. Linder" <linder@...>
Date: Mon Nov 6, 2006 8:32 pm
Subject: Re: rollers

tibia32

Elmer:

I am having images of Deja-Vous...I have screwed so much up learning the hard way re: bearings, rollers etc. When I inherited this lathe it had a 4 jaw chuck which means you need a dial indicator in order to mount a round item (shaft) anywhere near center So.. I bought three things on e-Bay: A 3 jaw headstock chuck, a 1/2" capacity Jacobs headstock chuck and another Jacobs chuck with a taper for the tailstock.

The practical approach was to buy some hardened steel 1/4" diameter ground rod. Much better than to try to turn your own stock on the lathe and not all that expensive. The next step is to drill a hole in the roller blank to accept the shaft. This is not easy on a big roller. I drilled my hole using the lathe and drilling from both ends. This necessitates unmounting the roller blank and flipping it end for end. Not a good practice but my only choice. The difficulty is to make the drill enter the roller on axis and stay on axis. A little bit of drift can be negated when you do the final finishing on the lathe. The shaft should be a press fit into the roller material. If this fails and the shaft is not tight enough you can use a couple of shaft collars and pin the collars to the ends of the roller using something like #16 brass escutcheon pins trimmed to length.

Once the rough roller blank is properly mounted on the shaft, it is chucked into the lathe for final machining. I used the jacobs chucks on both ends. I chucked a 1/4" ID oilite bearing in the tailstock to support one end of the shaft and the other end is chucked into the Jacobs tailstock chuck.

I appreciate the problems you are having turning things on the lathe. At the very least I would think you need a self centering 3-jaw headstock chuck. Then you can easily drill the hole in the shaft for the tailstock center and you will be able to mount the piece concentrically.

Dick

----- Original Message -----

From: Elmer Wiersma

To: VanDeGraaffGenerator@yahoogroups.com

Sent: Monday, November 06, 2006 8:56 AM

Subject: Re: [VanDeGraaffGenerator] rollers

Dick

Did you have some sort of clamp on both sides to hold the axis in place, because most lathes I see have a big clamp on one side (3 or 4 clamps, clawplate) and a pointed centre on the other end, I did try to lathe something on my dad's machine but because it was so difficult to get the centre right in the middle it was not a great success.

Did you also had a centre on 1 end and if so how did you made sure that the centre was truly centre with the shaft, in my first attempt I drilled a whole in the axis where the point of the centre would push in but it was not centred enough. I just thought of something to make a bearing which holds the shaft so I do not have to use the centre only problem is then to get bearing hole exactly in the centre of the shaft.

Elmer

#1679

From: "Richard R. Linder" <linder@...>
Date: Mon Nov 6, 2006 8:52 pm
Subject: Re: Bearings and big motor safety

tibia32

Dan:

Bicycle wheel bearings are rated for more radial load that you will ever apply in VDG service. Can't imagine why it failed unless the high RPM, which is not the case in a bicycle, was a factor

In my small VDG I am using flanged oilite bearings pressed fit into the plexi bearing supports. I was concerned that the bearing temperature might soften the plexi but that did not happen. I think the fact I used polished hardened steel shaft material resulted in minimal friction. The big VDG uses flange mounted miniature roller bearings. You can see them in some of the pictures I have posted.

Re: motors. I found that if you use roller bearings, even under high belt tension, you do not need high horsepower. Having said that, am using a 1/2 hp universal type motor. As you probably know, that HP rating only applies at full speed which, for this motor is 10,000 rpm. I control the motor speed with a "Variac" and generally run about 4000 rpm. which de-rates the motor to around 1/4 hp. At 60 mph using low friction roller bearings you can experience some spectacular destruction if you have a component failure, even with a low hp motor.

What you say is correct. spray and collector points can be trashed in the event of a belt failure. As far as fingers are concerned...... a big VDG is no toy, especially an open frame design like mine. It is electrically and mechanically a hazard to say the least.

DIck

----- Original Message -----

From: Dan Robinson

To: VanDeGraaffGenerator@yahoogroups.com

Sent: Sunday, November 05, 2006 6:00 PM

Subject: [VanDeGraaffGenerator] Bearings and big motor safety

I'm curious to hear what those of you with large generators and high-speed belts are using for bearings. I once tried using a bicycle wheel bearing on the lower roller, but it failed rather quickly once I began operating it under belt tension. Without the belt it worked fine.

That brings up another safety issue with high-speed belts and these heavy-duty motors. A lot of these big motors will not stop for anything. Instead of them bogging down upon encountering resistance, they will just keep going full-speed and destroy whatever item is resisting it. When the said bearing above failed, it nearly destroyed my entire lower assembly because the motor never missed a beat. Any individual VDG component failure with these motors can result in some catastrophic results especially if the belt holds together and gets wrapped around the shaft. Fingers and hands that get caught in such an event would not fare well.

Dan
--------------------------------------------------------
wvlightning.com | stormscenes.com | appalachianskies.com

Phone: 304-610-1374 | Email: video@stormscenes.com

"We have this treasure in earthen vessels, to show that
this power is from God, and not from us"
- 2 Corinthians 4:7
--------------------------------------------------------

--
No virus found in this outgoing message.
Checked by AVG Free Edition.
Version: 7.1.409 / Virus Database: 268.13.28/518 - Release Date: 11/4/2006

#1680

From: Elmer Wiersma <elmer.wiersma@...>
Date: Tue Nov 7, 2006 3:00 pm
Subject: Re: rollers

elmerwiersma

Dick

Thanks a lot, I had some sort of idea how to do it but that makes everything really clear on how I should do it. the headchuck my dad's lathe has is a selfcentering 3 jaw chuck, now I only need to find a jacobs chuck for the tailstock and then finally I can begin making the rollers cause with out those my machine will never run.

Elmer

----- Original Message -----

From: Richard R. Linder

To: VanDeGraaffGenerator@yahoogroups.com

Sent: Monday, November 06, 2006 9:32 PM

Subject: Re: [VanDeGraaffGenerator] rollers

Elmer:

I am having images of Deja-Vous...I have screwed so much up learning the hard way re: bearings, rollers etc. When I inherited this lathe it had a 4 jaw chuck which means you need a dial indicator in order to mount a round item (shaft) anywhere near center So.. I bought three things on e-Bay:  A 3 jaw headstock chuck,  a 1/2" capacity Jacobs headstock chuck and another Jacobs chuck with a taper for the tailstock.

The practical approach was to buy some hardened steel 1/4" diameter ground rod. Much better than to try to turn your own stock on the lathe and not all that expensive.   The next step is to drill a hole in the roller blank to accept the shaft. This is not easy on a big roller. I drilled my hole using the lathe and drilling from both ends. This necessitates unmounting the roller blank and flipping it end for end. Not a good practice but my only choice. The difficulty is to make the drill enter the roller on axis and stay on axis. A little bit of drift can be negated when you do the final finishing on the lathe. The shaft should be a press fit into the roller material. If this fails and the shaft is not tight enough you can use a couple of shaft collars and pin the collars to the ends of the roller using something like #16 brass escutcheon pins trimmed to length.

Once the rough roller blank is properly mounted on the shaft, it is chucked into the lathe for final machining. I used the jacobs chucks on both ends. I chucked a 1/4" ID oilite bearing in the tailstock to support one end of the shaft and the other end is chucked into the Jacobs tailstock chuck.

I appreciate the problems you are having turning things on the lathe. At the very least I would think you need a self centering 3-jaw headstock chuck. Then you can easily drill the hole in the shaft for the tailstock center and you will be able to mount the piece concentrically.

Dick



----- Original Message -----

From: Elmer Wiersma

To: VanDeGraaffGenerator@yahoogroups.com

Sent: Monday, November 06, 2006 8:56 AM

Subject: Re: [VanDeGraaffGenerator] rollers

Dick

Did you have some sort of clamp on both sides to hold the axis in place, because most lathes I see have a big clamp on one side (3 or 4 clamps, clawplate) and a pointed centre on the other end, I did try to lathe something on my dad's machine but because it was so difficult to get the centre right in the middle it was not a great success.

Did you also had a centre on 1 end and if so how did you made sure that the centre was truly centre with the shaft, in my first attempt I drilled a whole in the axis where the point of the centre would push in but it was not centred enough. I just thought of something to make a bearing which holds the shaft so I do not have to use the centre only problem is then to get bearing hole exactly in the centre of the shaft.

Elmer

#1681

From: Elmer Wiersma <elmer.wiersma@...>
Date: Tue Nov 7, 2006 6:13 pm
Subject: electric motor

elmerwiersma

Dick

Where did you get your electric motor from because 10,000 rpm is very fast, and I have been looking for another motor because the one I have now is 1.5 hp (1250 Watts) from a vacuum cleaner and I think that is way to powerful but I can not find any motor that goes to 10000 rpm.

Elmer

Reply | Messages in this Topic (2)

#1682

From: "Richard R. Linder" <linder@...>
Date: Tue Nov 7, 2006 6:33 pm
Subject: Re: rollers

tibia32

Elmer:

Sounds like you will be in good shape once you get a tailstock chuck. As far as drilling the rollers: If you can get a piece of round stock, your 3 jaw headstock chuck should grab the piece symmerically enough for you to drill the shaft hole reasonably on axis. After that, final finiish machining will take out any eccentricity.

Here's another idea that I used to make a teflon roller. Teflon rod stock is very expensive so I managed to get a piece of 1/2" thick teflon flat stock for much les $$. Using a compass, draw circles on the flat stock and mark the center of each circle as accurately as possible. You do this by making a center punch dimple on the flat stock first and then placing the compass needle in the dimple. Make the circle diameters somewhat larger than the final diameter of the roller. Cut the circles out of the flat stock. It's easy cutting even by hand. As before drill a slightly undersized hole for the shaft for a comfortable press fit. For a 3" wide roller you press 6 of these discs onto the shaft and secure them with shaft collars on both sides. Since teflon is slippery you will probably have to pin the discs to each other as well as to at least one of the shaft collars. So as not to severly unbalance the roller use a piece of thin wire like #18 gauge steel. If you drill blind holes in the shaft collars the steel pin will be captive and not be able to drift during operation. Now, with all the discs securely mounted on the shaft, you can finish machine the roller O.D. to its final size. Be sure to use a sturdy pin because it will have to stand the torque of the O.D. machining operation.

This approach eliminates all the grief in trying to accurately drill a long hole through a one piece roller.

Dick

#1683

From: "Richard R. Linder" <linder@...>
Date: Tue Nov 7, 2006 6:45 pm
Subject: Re: electric motor

tibia32

Elmer:

First of all, 10,000 rpm was not my first choice but there are not many small 1/2 hp universal motors to choose from and I did want a variable speed AC motor. Your vacuum cleaner motor is probably a universal brush type which can be controlled with a variac. In fact, I bet if you put a 1200 watt device like an electric heater or other similar device in series with the motor the motor will probably run at 1/2 speed. My VDGs are pulley driven so I also have the option of changing pulley ratio however right now I am using a 1:1 pulley ratio on both machines and the Variac for speed control.

The motor was obtained from W.W. Grainger Co. I am sure they have the motor illustrated on their website. If you need it, I can probably find the catalog number for you.

You might hear a lot about brush motors generating carbon dust and screwing up the VDG. That's certainly possible but I have not run into such a problem yet.

Dick

Reply | Messages in this Topic (2)

#1684

From: "Craig Fuller" <craigbfuller@...>
Date: Fri Nov 3, 2006 1:45 pm
Subject: Re: A question about the base material of a VDG

craigbfuller

That's an excellent point.  I forgot how the base of the machine
tends to draw charge from the terminal.  Adding grounded points to
the base (like the corners of an enclosure) would just make it worse.

As it is now, my acrylic support column is attached to the base by
an acrylic flange that I solvent welded to the bottom (it's quite
strong!).  There are steel bolts holding this flange to the base,
and in the dark I can see faint corona streams coming from bottoms
of them.  I don't want to get close to the tops of the bolts to see
corona (although I know it must be there) because the zaps from the
machine feel like short but painful headaches, you may be familiar
with the sensation.  I am going to check McMaster and see if I can
replace those steel bolts with nylon.

While I am VERY happy with the performance of my machine, I wish
that I had made the base out of something other than particleboard.
A polycarbonate base might be nice!

Craig

--- In VanDeGraaffGenerator@yahoogroups.com, "Richard R. Linder"
<linder@...> wrote:
>
> Craig:
>
> There are some commercial VDGs on the web that go both ways.  I
would suggest that the shape of a conductive shroud would be optimum
if it were a mirror image of the bottom half of the top terminal,
namely a hemisphere with an involute hole for the column.  I would
not spend any time or money on any kind of a conductive lower shroud
that had any surface feature that even resembled an edge or corner
facing in the upward direction.
>
> You can get more bang for the buck by increasing the conveyance of
electrons up to the top terminal. This would include incorporating a
higher belt speed, belt width and optimizing the belt material to be
complementary with the roller material.  At 60 mph and a belt width
of 6" I can easily generate over 100 microamps of charging current.
>
> Dick Linder
>

#1685

From: "Craig Fuller" <craigbfuller@...>
Date: Mon Nov 6, 2006 7:04 pm
Subject: Re: More Belt Length and a roller question

craigbfuller

Dick,

What is your total belt length?

The reason I ask is that McMaster sells the neoprene coated nylon in
increments of 1, 5, 10, 20, and 50 feet.  My belt is 77.5" or 6ft
7.5in, which means I must buy the 10 foot length and have a lot left
over.  If you are still thinking about trying the neoprene, perhaps
we could arrange to buy the 20ft length and split it down the middle
between the two of us?  Or maybe others could tag on as well?

It's just a thought.  I know organized long distance shared
purchases can be a pain.

Craig


--- In VanDeGraaffGenerator@yahoogroups.com, "Richard R. Linder"
<linder@...> wrote:
>
> JT:
>
> I am using Nylon for my bottom rollers and Teflon for the upper in
the small VDG and white PVC (plumbing style) for the top in the big
VDG.  The big one's charging current is in excess of 100uA so I have
no complaints. Of course there are many chemical variants of nylon
and they probably have different electrical characteristics.
>
> Cosindering all the obscure variables that are involved in these
beasts I often wonder if any of us have ever yet achieved the
perfect combination of materials, not to mention that elusive issue
of the re-entrant anti-corona involute aka hole in the HV sphere!
>
> DIck
>
>
>   ----- Original Message -----
>   From: jthandbook
>   To: VanDeGraaffGenerator@yahoogroups.com
>   Sent: Saturday, November 04, 2006 8:54 AM
>   Subject: [VanDeGraaffGenerator] More Belt Length and a roller
question
>
>
>   Thank you Elmer and Dick for your info. I wasn't suggesting a
six roller design (I think you
>   are right Elmer, way too many complications!) rather I was using
it as a demo for why I didn't
>   think longer belts were always better or they would be
configured for use.
>   Dick, do I understand you to mean that column height should be
great enough to avoid spark
>   over (your reference to terminal voltage) and that is the
determining factor?
>   I did find a reference on the website of the estimable Antonio
Carlos M. de Queiroz http://
>   www.coe.ufrj.br/~acmq/myvdg.html where he writes:
>   "The length of the belt, or the height of the terminal, have no
influence if the motor speed is
>   constant (except for insulation, and a small effect on the
output voltage, not considered). The
>   length L appears in the formula for the current in the form I =
e0EmaxWLn, where n is the
>   number of belt turns per second. The power is then P =
e0Emax2rWLn "
>   The full article expands on theory and the math behind.
>   Now to my roller question. My VDG has rollers 3.5 long x 1.5 in
diameter at the thickest.
>   Diameter is determined by what I can reasonably turn on my
Unimat lathe (and this relatively
>   small diameter is what motivated my question about belt length,
my wanting to avoid the belt
>   attracting itself midcolumn).
>   To date I've aluminum, teflon, and delrin rollers and I am
planning a nylon. However I came
>   across a reference which noted that nylon is prone to extremely
high voltage leakage.
>   Has anyone any information on this?
>   Thanks and best, JT
>

#1686

From: "Richard R. Linder" <linder@...>
Date: Wed Nov 8, 2006 2:19 am
Subject: Re: Re: More Belt Length and a roller question

tibia32

Craig:

I am not experiencing any base originating corona problems with either VDG. Take a look at my pic27 in volume 1 of my picture posts. It is an open design with 1/2" threaded rod supporting the base assembly. Notice the big acorn nuts. The original open hex nuts permitted corona off the ends of the threaded rod. None with the acorns. This model is called "shorty". It is the big VDG with a temporary short column. It served as a test jig for roller and belt design, strictly to evaluate roller - belt combinations and resulting charging current.

Since I have several spare belts for both VDGs I was not planning to do any more research in the immediate future. I am preparing to do my annual tour with my Town's science center to all the schools. Between that and being a Wurlitzer theater organ nut, time is tight.

Dick

----- Original Message -----

From: Craig Fuller

To: VanDeGraaffGenerator@yahoogroups.com

Sent: Monday, November 06, 2006 2:04 PM

Subject: [VanDeGraaffGenerator] Re: More Belt Length and a roller question

Dick,

What is your total belt length?

The reason I ask is that McMaster sells the neoprene coated nylon in
increments of 1, 5, 10, 20, and 50 feet. My belt is 77.5" or 6ft
7.5in, which means I must buy the 10 foot length and have a lot left
over. If you are still thinking about trying the neoprene, perhaps
we could arrange to buy the 20ft length and split it down the middle
between the two of us? Or maybe others could tag on as well?

It's just a thought. I know organized long distance shared
purchases can be a pain.

Craig

--- In VanDeGraaffGenerator@yahoogroups.com, "Richard R. Linder"
<linder@...> wrote:
>
> JT:
>
> I am using Nylon for my bottom rollers and Teflon for the upper in
the small VDG and white PVC (plumbing style) for the top in the big
VDG. The big one's charging current is in excess of 100uA so I have
no complaints. Of course there are many chemical variants of nylon
and they probably have different electrical characteristics.
>
> Cosindering all the obscure variables that are involved in these
beasts I often wonder if any of us have ever yet achieved the
perfect combination of materials, not to mention that elusive issue
of the re-entrant anti-corona involute aka hole in the HV sphere!
>
> DIck
>
>
> ----- Original Message -----
> From: jthandbook
> To: VanDeGraaffGenerator@yahoogroups.com
> Sent: Saturday, November 04, 2006 8:54 AM
> Subject: [VanDeGraaffGenerator] More Belt Length and a roller
question
>
>
> Thank you Elmer and Dick for your info. I wasn't suggesting a
six roller design (I think you
> are right Elmer, way too many complications!) rather I was using
it as a demo for why I didn't
> think longer belts were always better or they would be
configured for use.
> Dick, do I understand you to mean that column height should be
great enough to avoid spark
> over (your reference to terminal voltage) and that is the
determining factor?
> I did find a reference on the website of the estimable Antonio
Carlos M. de Queiroz http://
> www.coe.ufrj.br/~acmq/myvdg.html where he writes:
> "The length of the belt, or the height of the terminal, have no
influence if the motor speed is
> constant (except for insulation, and a small effect on the
output voltage, not considered). The
> length L appears in the formula for the current in the form I =
e0EmaxWLn, where n is the
> number of belt turns per second. The power is then P =
e0Emax2rWLn "
> The full article expands on theory and the math behind.
> Now to my roller question. My VDG has rollers 3.5 long x 1.5 in
diameter at the thickest.
> Diameter is determined by what I can reasonably turn on my
Unimat lathe (and this relatively
> small diameter is what motivated my question about belt length,
my wanting to avoid the belt
> attracting itself midcolumn).
> To date I've aluminum, teflon, and delrin rollers and I am
planning a nylon. However I came
> across a reference which noted that nylon is prone to extremely
high voltage leakage.
> Has anyone any information on this?
> Thanks and best, JT
>

#1687

From: Elmer Wiersma <elmer.wiersma@...>
Date: Wed Nov 8, 2006 1:38 pm
Subject: Re: rollers

elmerwiersma

Dick

Your idea of that teflon roller is good but I have searched hard but have not come across teflon flat stock here, I saw some teflon rod but it was 130 dollars for 20 inches, it even went up to 400 dollars for 40 inches, so pretty expensive, I looked up some pvc rod and it was much cheaper and I had some nylon here and I rubbed it with the pvc and the pvc got a big charge so that would also work good and that is what you have in one of your VDG.

Do you know if the nylon also creates a big charge or that it the negative charge that is most noticable because when I rub my belt material with the pvc, the pvc gets a charge which makes the hair of my arm stand up but when I rub my belt with the nylon nothing happens (no noticable feeling of static on both) and when I rub nylon with pvc the pvc gets a big charge.

for the overpowerfull motor I think I will buy a variac because searching for a new motor is such a hassel when electrical appliances here get recycled immediatly after use, so finding an motor is very hard and variacs are here plenty available, thank goodness and I think I will buy a new variac in stead of a second hand because I want mine to last long and I do not know what happened to the second hand variac, and the ones I saw were not in that good a shape. well the new variac will cost about 100 euro (130 dollars) but that's okay since I can use it more many other things than just the VDG

about the jacobs tailstock, apparently my father had one lying around somewhere for the lathe so when I have bought the nylon and the pvc I can start making rollers.

Elmer

----- Original Message -----

From: Richard R. Linder

To: VanDeGraaffGenerator@yahoogroups.com

Sent: Tuesday, November 07, 2006 7:33 PM

Subject: Re: [VanDeGraaffGenerator] rollers

Elmer:

Sounds like you will be in good shape once you get a tailstock chuck. As far as drilling the rollers: If you can get a piece of round stock, your 3 jaw headstock chuck should grab the piece symmerically enough for you to drill the shaft hole reasonably on axis. After that, final finiish machining will take out any eccentricity.

Here's another idea that I used to make a teflon roller. Teflon rod stock is very expensive so I managed to get a piece of 1/2" thick teflon flat stock for much les $$. Using a compass, draw circles on the flat stock and mark the center of each circle as accurately as possible. You do this by making a center punch dimple on the flat stock first and then placing the compass needle in the dimple. Make the circle diameters somewhat larger than the final diameter of the roller. Cut the circles out of the flat stock. It's easy cutting even by hand. As before drill a slightly undersized hole for the shaft for a comfortable press fit. For a 3" wide roller you press 6 of these discs onto the shaft and secure them with shaft collars on both sides. Since teflon is slippery you will probably have to pin the discs to each other as well as to at least one of the shaft collars. So as not to severly unbalance the roller use a piece of thin wire like #18 gauge steel. If you drill blind holes in the shaft collars the steel pin will be captive and not be able to drift during operation. Now, with all the discs securely mounted on the shaft, you can finish machine the roller O.D. to its final size. Be sure to use a sturdy pin because it will have to stand the torque of the O.D. machining operation.

This approach eliminates all the grief in trying to accurately drill a long hole through a one piece roller.

Dick

#1688

From: "jthandbook" <jthandbook@...>
Date: Wed Nov 8, 2006 2:49 pm
Subject: making rollers

jthandbook

Elmer...�I think you will find that your nylon rod, if rubbed with silk not
leather, will give
you a good charge.
If you ever want to try teflon another good but much cheaper choice is teflon
tube which
you can slip over a wooden dowel core.
You can even wrap any roller with teflon tape to make it "teflon" on the
tribolelectric scale
and by adding a few wrapped layers towards the middle of your roller you can
"crown" it.
By the same token you could wrap your other roller with plastic electrical tape
and with a
teflon wrapped roller have a great set.
Because the charge transfer is a function of contact/seperation between the
roller and belt
you only need a surface layer of your chosen material on the roller to make it
behave as if
the roller were uniform, say solid teflon.
Best, JT





--- In VanDeGraaffGenerator@yahoogroups.com, Elmer Wiersma <elmer.wiersma@...>
wrote:
>
> Dick
>
> Your idea of that teflon roller is good but I have searched hard but have not
come
across teflon flat stock here, I saw some teflon rod but it was 130 dollars for
20 inches, it
even went up to 400 dollars for 40 inches, so pretty expensive, I looked up some
pvc rod
and it was much cheaper and I had some nylon here and I rubbed it with the pvc
and the
pvc got a big charge so that would also work good and that is what you have in
one of
your VDG.
>
> Do you know if the nylon also creates a big charge or that it the negative
charge that is
most noticable because when I rub my belt material with the pvc, the pvc gets a
charge
which makes the hair of my arm stand up but when I rub my belt with the nylon
nothing
happens (no noticable feeling of static on both) and when I rub nylon with pvc
the pvc gets
a big charge.
>
> for the overpowerfull motor I think I will buy a variac because searching for
a new motor
is such a hassel when electrical appliances here get recycled immediatly after
use, so
finding an motor is very hard and variacs are here plenty available, thank
goodness and I
think I will buy a new variac in stead of a second hand because I want mine to
last long
and I do not know what happened to the second hand variac, and the ones I saw
were not
in that good a shape. well the new variac will cost about 100 euro (130 dollars)
but that's
okay since I can use it more many other things than just the VDG
>
> about the jacobs tailstock, apparently my father had one lying around
somewhere for
the lathe so when I have bought the nylon and the pvc I can start making
rollers.
>
> Elmer
>
>
>   ----- Original Message -----
>   From: Richard R. Linder
>   To: VanDeGraaffGenerator@yahoogroups.com
>   Sent: Tuesday, November 07, 2006 7:33 PM
>   Subject: Re: [VanDeGraaffGenerator] rollers
>
>
>
>   Elmer:
>
>   Sounds like you will be in good shape once you get a tailstock chuck.  As
far as drilling
the rollers: If you can get a piece of round stock, your 3 jaw headstock chuck
should grab
the piece symmerically enough for you to drill the shaft hole reasonably on
axis. After
that, final finiish machining will take out any eccentricity.
>
>   Here's another idea that I used to make a teflon roller.     Teflon rod
stock is very
expensive so I managed to get a piece of  1/2" thick teflon flat stock for much
les $$.
Using a compass, draw circles on the flat stock and mark the center of each
circle as
accurately as possible. You do this by making a center punch dimple on the flat
stock first
and then placing the compass needle in the dimple. Make the circle diameters
somewhat
larger than the final diameter of the roller. Cut the circles out of the flat
stock. It's easy
cutting even by hand. As before drill a slightly undersized hole for the shaft
for a
comfortable press fit. For a 3" wide roller you press 6 of these discs onto the
shaft and
secure them with shaft collars on both sides. Since teflon is slippery you will
probably have
to pin the discs to each other as well as to at least one of the shaft collars.
So as not to
severly unbalance the roller use a piece of thin wire like #18 gauge steel. If
you drill blind
holes in the shaft collars the steel pin will be captive and not be able to
drift during
operation. Now, with all the discs securely mounted on the shaft, you can finish
machine
the roller O.D. to its final size.  Be sure to use a sturdy pin because it will
have to stand the
torque of the O.D. machining operation.
>
>   This approach eliminates all the grief in trying to accurately drill a long
hole through a
one piece roller.
>
>
>   Dick
>

#1689

From: Elmer Wiersma <elmer.wiersma@...>
Date: Wed Nov 8, 2006 4:10 pm
Subject: Re: making rollers

elmerwiersma

Hi JT

thanks for your input, yeah I know that a tiny layer is good enough but for my machine I am aiming for the speed that dicks big VDG is doing and maybe then the PVC tape and teflon tape just will not hold at those speeds and forces, my belt is almost the same material that dick has, so vinyl impregnated polyester for me and dick has vinyl impregnated nylon and since the contact is vinyl it basically is the same. I can try the teflon if I have my machine up and running and working correctly since I then know that if it does not work anymore I know to look for the teflon as the problem. For the roller I would like something really solid and sturdy and solid nylon and pvc rod are as good as it gets.

Elmer

----- Original Message -----

From: jthandbook

To: VanDeGraaffGenerator@yahoogroups.com

Sent: Wednesday, November 08, 2006 3:49 PM

Subject: [VanDeGraaffGenerator] making rollers

Elmer... I think you will find that your nylon rod, if rubbed with silk not leather, will give
you a good charge.
If you ever want to try teflon another good but much cheaper choice is teflon tube which
you can slip over a wooden dowel core.
You can even wrap any roller with teflon tape to make it "teflon" on the tribolelectric scale
and by adding a few wrapped layers towards the middle of your roller you can "crown" it.
By the same token you could wrap your other roller with plastic electrical tape and with a
teflon wrapped roller have a great set.
Because the charge transfer is a function of contact/seperation between the roller and belt
you only need a surface layer of your chosen material on the roller to make it behave as if
the roller were uniform, say solid teflon.
Best, JT

--- In VanDeGraaffGenerator@yahoogroups.com, Elmer Wiersma <elmer.wiersma@...>
wrote:
>
> Dick
>
> Your idea of that teflon roller is good but I have searched hard but have not come
across teflon flat stock here, I saw some teflon rod but it was 130 dollars for 20 inches, it
even went up to 400 dollars for 40 inches, so pretty expensive, I looked up some pvc rod
and it was much cheaper and I had some nylon here and I rubbed it with the pvc and the
pvc got a big charge so that would also work good and that is what you have in one of
your VDG.
>
> Do you know if the nylon also creates a big charge or that it the negative charge that is
most noticable because when I rub my belt material with the pvc, the pvc gets a charge
which makes the hair of my arm stand up but when I rub my belt with the nylon nothing
happens (no noticable feeling of static on both) and when I rub nylon with pvc the pvc gets
a big charge.
>
> for the overpowerfull motor I think I will buy a variac because searching for a new motor
is such a hassel when electrical appliances here get recycled immediatly after use, so
finding an motor is very hard and variacs are here plenty available, thank goodness and I
think I will buy a new variac in stead of a second hand because I want mine to last long
and I do not know what happened to the second hand variac, and the ones I saw were not
in that good a shape. well the new variac will cost about 100 euro (130 dollars) but that's
okay since I can use it more many other things than just the VDG
>
> about the jacobs tailstock, apparently my father had one lying around somewhere for
the lathe so when I have bought the nylon and the pvc I can start making rollers.
>
> Elmer
>
>
> ----- Original Message -----
> From: Richard R. Linder
> To: VanDeGraaffGenerator@yahoogroups.com
> Sent: Tuesday, November 07, 2006 7:33 PM
> Subject: Re: [VanDeGraaffGenerator] rollers
>
>
>
> Elmer:
>
> Sounds like you will be in good shape once you get a tailstock chuck. As far as drilling
the rollers: If you can get a piece of round stock, your 3 jaw headstock chuck should grab
the piece symmerically enough for you to drill the shaft hole reasonably on axis. After
that, final finiish machining will take out any eccentricity.
>
> Here's another idea that I used to make a teflon roller. Teflon rod stock is very
expensive so I managed to get a piece of 1/2" thick teflon flat stock for much les $$.
Using a compass, draw circles on the flat stock and mark the center of each circle as
accurately as possible. You do this by making a center punch dimple on the flat stock first
and then placing the compass needle in the dimple. Make the circle diameters somewhat
larger than the final diameter of the roller. Cut the circles out of the flat stock. It's easy
cutting even by hand. As before drill a slightly undersized hole for the shaft for a
comfortable press fit. For a 3" wide roller you press 6 of these discs onto the shaft and
secure them with shaft collars on both sides. Since teflon is slippery you will probably have
to pin the discs to each other as well as to at least one of the shaft collars. So as not to
severly unbalance the roller use a piece of thin wire like #18 gauge steel. If you drill blind
holes in the shaft collars the steel pin will be captive and not be able to drift during
operation. Now, with all the discs securely mounted on the shaft, you can finish machine
the roller O.D. to its final size. Be sure to use a sturdy pin because it will have to stand the
torque of the O.D. machining operation.
>
> This approach eliminates all the grief in trying to accurately drill a long hole through a
one piece roller.
>
>
> Dick
>

#1690

From: "jthandbook" <jthandbook@...>
Date: Wed Nov 8, 2006 7:38 pm
Subject: one more roller suggestion

jthandbook

I fully understand your want for solid rollers Elmer though of course a three
inch diameter
teflon or aluminum rod gets pretty heavy even over short lengths but nothing
that more
motor, better bearings, and HS steel axles won't solve
I found that Sundance Plastics and MRO Supply (they have a store on eBay) are a
great source
for large diameter teflon and all types of plastic rods in short sections and at
reasonable
prices. They welcome inquiries for anything not listed.
Best, JT

#1691

From: Elmer Wiersma <elmer.wiersma@...>
Date: Wed Nov 8, 2006 9:02 pm
Subject: Re: one more roller suggestion

elmerwiersma

that is a really nice shop certainly possible for me if I want to build a smaller VDG, and my rollers on this VDG will be 60 mm (2.36 inches) in diameter and I found some rod that is not very expensive in a corner of my country, if dick's 0.5 hp motor works fine than my 1.6 hp will be overkill I think but with a variac it will not be a problem and that vacuum cleaner motor is rated at 10,000 to 20,000 rpm under the load of the fan, now a VDG roller is not a fan but the rpm will not differ much or I just turn the voltage up, so my motor will have plenty of speed if not to much, I have to buy a variac because if I start up my VDG directly so no voltage control I think the motor will run so fast that it destroys everything.

Elmer

----- Original Message -----

From: jthandbook

To: VanDeGraaffGenerator@yahoogroups.com

Sent: Wednesday, November 08, 2006 8:38 PM

Subject: [VanDeGraaffGenerator] one more roller suggestion

I fully understand your want for solid rollers Elmer though of course a three inch diameter
teflon or aluminum rod gets pretty heavy even over short lengths but nothing that more
motor, better bearings, and HS steel axles won't solve
I found that Sundance Plastics and MRO Supply (they have a store on eBay) are a great source
for large diameter teflon and all types of plastic rods in short sections and at reasonable
prices. They welcome inquiries for anything not listed.
Best, JT

#1692

From: "Richard R. Linder" <linder@...>
Date: Wed Nov 8, 2006 9:50 pm
Subject: Re: rollers

tibia32

Elmer:

Regarding your experience with rubbing lower and upper roller with the belt material:

I never tried that experiment but I am not convinced that it is a good basis for accepting or rejecting roller and belt material.

I built a test jig to evaluate belt and roller material. This jig consistes of the top and bottom assemblies of my big VDG with a short support tube. This setup allows me to evaluate different materials by measuring the short circuit current. It also is a good tool to test different versions of spray and collector combs. You can see a picture (#27) of this on the VDG forum site.

I have also used hardwood cores for large diameter rollers. Check pictures #21 and #25. The outer shell of the roller should be pinned to the core. Several months after I made my first such roller the core had shrunk enough and/or the PVC had stretched enough to allow the shell to slip off!

As you have stated, if you are designing a high speed high belt tension system you must be very fussy about roller balance, the weight of the belt and the choice of bearings.

Dick

#1693

From: "Richard R. Linder" <linder@...>
Date: Thu Nov 9, 2006 8:31 pm
Subject: Re: one more roller suggestion

tibia32

Elmer:

My opinion: Speed control is a must if you are experimenting with large VDGs and high belt speeds. Adjustment of belt tracking and tension must be done at low speed otherwise, at full speed the belt could mistrack and self destruct. Also....if you are using "no stretch" belt material, it will take some run in time before tracking becomes predictable so don't get discouraged. At the start the belt will try to stay flat and therefore not conform to the crown, as subtle as it might be. After running a while at low speed, the belt tension can be increased to cause the belt to begin to conform with the pulley crown. As this process continues, tracking will improve.

I am still using the same belt (3 years old). Just for information, I tried a new belt and had to go through the whole break-in procedure again.

By the way, If you are going to use vinyl impregnated nylon, the WeldOn series of cements work very well. Ithink WeldOn #16 is the viscous version and has been available through McMaster-Carr. The WeldOn liquifies the vinyl and produces a fused and flexible joint. When the time is right we can swap some e-mails about belt fabrication. There are some techniques which will minimize scrap and frustration.

Dick

----- Original Message -----

From: Elmer Wiersma

To: VanDeGraaffGenerator@yahoogroups.com

Sent: Wednesday, November 08, 2006 4:02 PM

Subject: Re: [VanDeGraaffGenerator] one more roller suggestion

that is a really nice shop certainly possible for me if I want to build a smaller VDG, and my rollers on this VDG will be 60 mm (2.36 inches) in diameter and I found some rod that is not very expensive in a corner of my country, if dick's 0.5 hp motor works fine than my 1.6 hp will be overkill I think but with a variac it will not be a problem and that vacuum cleaner motor is rated at 10,000 to 20,000 rpm under the load of the fan, now a VDG roller is not a fan but the rpm will not differ much or I just turn the voltage up, so my motor will have plenty of speed if not to much, I have to buy a variac because if I start up my VDG directly so no voltage control I think the motor will run so fast that it destroys everything.

Elmer

----- Original Message -----

From: jthandbook

To: VanDeGraaffGenerator@yahoogroups.com

Sent: Wednesday, November 08, 2006 8:38 PM

Subject: [VanDeGraaffGenerator] one more roller suggestion

I fully understand your want for solid rollers Elmer though of course a three inch diameter
teflon or aluminum rod gets pretty heavy even over short lengths but nothing that more
motor, better bearings, and HS steel axles won't solve
I found that Sundance Plastics and MRO Supply (they have a store on eBay) are a great source
for large diameter teflon and all types of plastic rods in short sections and at reasonable
prices. They welcome inquiries for anything not listed.
Best, JT

#1694

From: Elmer Wiersma <elmer.wiersma@...>
Date: Fri Nov 10, 2006 9:35 am
Subject: Re: one more roller suggestion

elmerwiersma

Dick

Apparently my father wants also to work on a lathe to build a traction engine and because the lathe that we have is old and not in a good condition he found a better one which he has not bought yet but probably will, that one is much better then the one we have now so that will be a good thing, I will also buy a variac because of the belt speed control as you said.

We do not have WeldOn#16 here but the next best thing I could find here was called soft plastic glue, it is a glue especially for soft pvc (vinyl) and also liquifies the pvc and creates a pretty strong joint. I made some test pieces which I am still not able to pull apart.

When the new lathe is here I can start making the rollers, I will probably have to start making some phone calls next week to order the pvc and nylon rod and then pick them up at the end of next week.

Thanks

Elmer