Belt drive motor pulley wobble

martyh · 19th June 2008, 11:52 PM

I’m just putting the finishing touches on my belt drive project and I noticed a slight wobble in the pulley. I measured it with a dial indicator at .009”. I was able to make an adjustment and have it down to .003”. I’m using a VPI hw-19 motor, pulley and belt so I’m wondering if the elastic belt will take up some of the slack. What say you, should I order a new set or will this one be okay?

Thanks in advance,
Marty

EC8010 · 20th June 2008, 02:54 PM

Eccentricity on a motor pulley will cause wow and flutter - changing the belt won't help.

YNWOAN · 20th June 2008, 09:29 PM

'order a new set' of what exactly? As stated above, changing the belts will not make any difference.

martyh · 21st June 2008, 12:12 AM

Thank you for the replies. I’m sorry if the original post was confusing. I meant to ask if I should order a new motor and pulley set. My hope was that the elastic nature of the belt would mitigate some of the variation.

Thinking about it further, I see that the wobble is effectively changing the radius of the drive pulley by .003” 20 times a second. As I see it now, the elasticity may lower the peak speed variation but never eliminate it.

EC8010 · 21st June 2008, 08:49 AM

Quote:

Originally posted by martyh
Thinking about it further, I see that the wobble is effectively changing the radius of the drive pulley by .003” 20 times a second. As I see it now, the elasticity may lower the peak speed variation but never eliminate it.

You have it exactly. My commiserations. Some members have said that they have been able to true pulleys by running them with a clamped Dremel (or similar) carrying a grindstone brushing lightly against them as they run. If you have a Dremel and you're going to buy a new motor and pulley anyway, you've nothing to lose.

AVWERK · 21st June 2008, 06:59 PM

Yeah, you would want to lock the body of the motor and the same with the Dremel in some way.

Think in terms of a lathe principle so the runout error is focused and ground down only.

Regards
David

martyh · 21st June 2008, 10:39 PM

Great idea, thanks. In the mean time I’ve pulled another set from my hw-19 to use.

19th June 2008, 11:52 PM	#1
martyh diyAudio Member Join Date: Feb 2004 Location: Wisconsin	Belt drive motor pulley wobble I’m just putting the finishing touches on my belt drive project and I noticed a slight wobble in the pulley. I measured it with a dial indicator at .009”. I was able to make an adjustment and have it down to .003”. I’m using a VPI hw-19 motor, pulley and belt so I’m wondering if the elastic belt will take up some of the slack. What say you, should I order a new set or will this one be okay? Thanks in advance, Marty

20th June 2008, 02:54 PM	#2
EC8010 diyAudio Moderator Join Date: Jan 2003 Location: Near London. UK	Eccentricity on a motor pulley will cause wow and flutter - changing the belt won't help. __________________ The loudspeaker: The only commercial Hi-Fi item where a disproportionate part of the budget isn't spent on the box. And the one where it would make a difference...

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20th June 2008, 09:29 PM	#3
YNWOAN diyAudio Member Join Date: Jan 2007	'order a new set' of what exactly? As stated above, changing the belts will not make any difference.

21st June 2008, 12:12 AM	#4
martyh diyAudio Member Join Date: Feb 2004 Location: Wisconsin	Thank you for the replies. I’m sorry if the original post was confusing. I meant to ask if I should order a new motor and pulley set. My hope was that the elastic nature of the belt would mitigate some of the variation. Thinking about it further, I see that the wobble is effectively changing the radius of the drive pulley by .003” 20 times a second. As I see it now, the elasticity may lower the peak speed variation but never eliminate it.

21st June 2008, 06:59 PM	#6
AVWERK diyAudio Member Join Date: Jan 2004 Location: OC,Calif.	Yeah, you would want to lock the body of the motor and the same with the Dremel in some way. Think in terms of a lathe principle so the runout error is focused and ground down only. Regards David

21st June 2008, 10:39 PM	#7
martyh diyAudio Member Join Date: Feb 2004 Location: Wisconsin	Great idea, thanks. In the mean time I’ve pulled another set from my hw-19 to use.

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