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VPI motor - upgrade to 300 rpm?

I hsve a HW-19 mk 4 plus or something, with the Black knight platter and inverted bearing, along with the SDS, The SAMA is the Hurst 600 rpm. This has run, now, for five years. Recently I have had problems with pitch variation, not easy to locate. The problems have been somewhat solved by glueing the pulley to the shaft and by oiling the motor, helping a lot, but perhaps not fully. Should I order a 300 rpm motor and new pulley? Advice is appreaciated, especially, experiences going from the 600 to the 300 rpm motor.
o_holter
ptmconsulting
1,000 posts
 
If you have an SDS then there is one other thing I can highly recommend that you try. Get rid of that vibration prone VPI rubber belt and find some silk thread. Tie a basic knot in the ends and use that instead. You will definitely have to adjust the speed to compensate for the thread's smaller diameter sitting down in the pully groove. You will also definitely need to give the platter a push-start by hand.

The PRAT will increase dramatically, with more detain and better space and air. Not a small improvement and easily one of the best things I did for my VPI.
o_holter OP
541 posts
 

Thanks! I think PRAT is what I am looking for, and want to try the silk thread variant. What kind of basic knot do you use?
The question remains, what is the best motor, is there a sonic profit with 300 rpm? Since no-one here has answered, I have mailed VPI about this.
markd51
741 posts
 
Please keep in mind, that VPI is on vacation till Jan 11 I believe. Mark
ptmconsulting
1,000 posts
 
Here's a thread discussion thread (sorry, I couldn't resist) but there are others and some that have on-line sources quoted.

http://forum.audiogon.com/cgi-bin/fr.pl?eanlg&1264987921&openfrom&1&4#1
storyboy
80 posts
 
I have not made an unbiased comparison between the 300 and 600 rpm motors, but years ago when I looked up specs for the so-called upgrade, I noticed the 600 has twice the torque - that's quite a difference. Of course, there is probably a price to pay for that, likely vibration, but with all the talk years ago about the torquey idler drives, I kept the 600 and made myself a pulley stabilizer/flywheel which goes in front of the pulley and tensions the belt around the pulley 180 degrees - all without increasing the overall belt tension. I can just turn my motor on, no pushing, and the platter starts to spin at speed immediately, and that's how torquey the 600 motor really is. I have only 1/4" of belt on each side of the pulley/flywheel, which means it will have very little stretch - compare that to the stock 6" length and 40 degrees of contact.

And, of course, it sounds way better. Why VPI doesn't do this I don't understand.

Sorry, can't link a pic, but I'll try to figure something out.
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