Drive belt rides low on pulley - Printable Version
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+--- Thread: Drive belt rides low on pulley (/showthread.php?tid=19647)
Drive belt rides low on pulley - ODPILOT - 02-10-2019
[attachment=18473]
2/10/19
Hey Folks . I am restoring a Philco 53-1750 Radio/Phonograph with an M-24A record changer. This is the 3rd one I'm restoring. On the first two, I replaced the drive belts in the record changer and had no problems.
On this 3rd one now, the belt wants to ride low on the pulley and then the bottom edge of the belt contacts the base metal and squeals. If I gently force the belt up to the middle of the pulley with my finger nail as it's spinning, the squealing stops but then wants to go back low when I let go. Are these supposed to position themselves on the middle of the pulley or are they supposed to ride somewhat low?
This particular belt I purchased from thevoiceofmusic.com on on 5/8/2013 so maybe it's just old rubber now and deteriorated and has stretched out when I started using it? Maybe I just need a new one?
The original belt which is dried out, does work and rides only slightly below the center of the pulley.
I tried spraying non squeal spray on the "new" belt (like you would use for for an alternator belt on a car) and it ruined the belt ! Live and learn !
So what's the issue here, do I just need a new one? I also tried 2 other spare pulleys from M-24A record changers I bought for spare parts, the same thing - low riding belt - occurs just the same with all pulleys.
Thanks.
RE: Drive belt rides low on pulley - Arran - 02-10-2019
Have you noticed if there is any runout on the motor shaft, meaning that it is bent or no longer at 90 degrees to the rest of the mechanism? This may cause the belt to work it's way down. Bad bearings in the motor could also cause this, is there any play in the motor shaft?
Regards
Arran
RE: Drive belt rides low on pulley - ODPILOT - 02-11-2019
I rebuilt the motor, cleaning it and re-lubricated it. It runs quiet and smooth and it spins perfectly (no wobble as you might see with a bent shaft) . I tried wiggling the motor shaft side to side and it is tight, there is no play horizontally. When pulling on it vertically, I can move the motor shaft up and down about 1/8", I'm thinking maybe this is normal play. I tried that on another motor I have and it seems to have the same vertical play. As far as being bent, as best as I can tell, the motor shaft and the shaft for the pulley are not bent. If they are not perfectly vertical, it's hard to tell, but just eyeballing it - they seem to be straight. Thnx.
RE: Drive belt rides low on pulley - ODPILOT - 02-11-2019
[attachment=18488][attachment=18489]
I think I found out the problem. I looked at a spare motor assembly and found that there is a tiny "C" ring which fits into a groove near the bottom of the pulley shaft. The "C" ring acts as a stop for the pulley so it doesn't ride too low on the pulley shaft. On the spare one I have, the C ring is in good condition and stops the pulley from riding too low. On the motor assembly I already have installed, the C ring is worn out and compressed into the groove on the pulley shaft and does not stop the pulley from going all the way to the bottom of the shaft, thereby taking the belt down with it and allowing everything to ride low. I think all I have to do is remove the old C ring and replace it with the better one and I think the problem is then solved.
RE: Drive belt rides low on pulley - mikethedruid - 02-11-2019
You might try an auto parts store and see if they have a C ring that is a good match; that way you wouldn't have to remove the one on the good motor. Auto parts stores usually carry a good selection of C rings.
RE: Drive belt rides low on pulley - ODPILOT - 02-11-2019
Good idea - I should find a new C ring - the old used one may be worn out somewhat as well anyway and a matter of time before the same issue pops up again. Thanks for your help. !