RCA MI-12701 78 Only Cutter - capstan dimensions?

[piaptk]

Hey everyone,
I bought a 78 onoy RCA cutter, but the rubber capstan was terribly warped (it's almost square!), and was wondering if anyone had one of these machines with a good one that could get me measurements of the capstan diameter.

Thanks!

[sameal]

Terry of terry's rubber rollers "may" have the original dimensions.

I say may because that's probably not something he see's everyday. But it's worth a try

[Bahndahn]

You may calculate it if you know the RPM of the motor, which may be listed on the motor or via the motor data sheet.

PullyRatio = RPMRoller ÷ RPMPlatter = DiameterPlatter ÷ DiameterRoller

Punch in what you have [platter diameter, desired platter speed, and roller speed] and simplify to obtain the diameter of the roller.

[Bahndahn]

In other words you can use the calculations found on the following link, just note that the only difference between a belt drive/pulley system and a direct contact roller system is that the direction of rotation is opposing for the two diameters in the latter.

http://www.cousesteel.com/AndysPlace/Pulleys.html

[markrob]

Hi,

I don't know the RCA lathe, but if its done like the the Presto 6N, the roller in question is a idler and does not influence the platter speed. In that case, the diameter is not so critical as long as it allows the power to be transmitted to the platter from the motor.

Mark

[piaptk]

This is an actual rubber capstan that directly turns the rim, so it definitely affects the speed.

Bahndahn, thanks for the formula!