Help with Shugart SA801 8" floppy with 230v 50 cycle

dwight elvey dkelvey at
Thu Nov 27 00:03:22 CST 2008

> From: ard at
>> =20
>> Hi
>> When we ground the pulley down, we checked the rate as
>> we ground it down. What I'd like to know is how does one
>> pedict the effective diameter when the pulley is crowned,
>> as in the SA800?
> My guess is that, since the blet runs on the maximum diameter part of the 
> pulley (the point of crowning being to keep the belt on), then taking the 
> maximum diamaeter should be OK for this.
> Thinking about it, should the ratio of diamaters of the spindle flywheel 
> and the motor pulley be the same for all positions across the width of 
> the belt? In other words should the (larger diameter) flywheel have a 
> steeper crowing angle than the motor pulley? 
> -tony
 The flywheel is flat. Only the motor pulley is the only part that
has a crown. When the belt runs on the pulley, the center of the
crown stretches the belt a little. This is what makes the crown
keep the belt centered. The stetching means that the effective
diameter of the pulley is slightly less than the crown. I
would guess that one would need to know how much the belt
stretches at the crown in order to know how much to compensate
for the diameters.
 The belts on the SA800s are quite stiff so I suspect that using
the crown would get one close.

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