Request Help with Speed Control Issues

[oddie]

Two things.

I think I bought the OEM belt from Shopsmith back when they were selling belts that were smaller than spec. This belt measures less than 1/2” wide. I’ve been told this is too small and should be replaced. I bought the replacement belt from a third party who got them from Shopsmith. This new belt measures a little over 1/2”.

After my last post where I said I’d done another high speed adjustment using a tach and the belt on the motor sheaves was about 1/8” from the edge I ran the machine and my belt sander. Then I looked at the belt again and it was proud of the rim. So I did the adjustment again using the belt position as a guide. Now the “Fast” speed is 4720 RPM and the “Slow” is 1180 RPM.

The first four pics below were taken before this last adjustment and the second four were taken afterwards. The text in the pics gives the sequence, sheave and corresponding speed.

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[JPG]

Same belt in all 8 pix? Which belt?

[oddie]

It’s the same belt in all the pics in my last post. That belt is the new replacement belt that measures over 1/2”.

[dusty]

The last four images depict belt positions that I would accept as normal though they are slightly different than mine. But, my belts are all at least four years old. A new belt will give slightly different readings than one that has been broken and with which a high speed adjustment has been made.

The tachometer readings are, to say the least, unusual. Where are you measuring with the tach. One reading (4720) looks like you might be on the quill at high speed while the other (1180) looks like the idler shaft at low speed.

[JPG]

Yes the 'Mystery" is the resultant rpm figures. The overall range(1180 - 4720)[4:1] is less than 'typical'(700 - 5200)[7.4:1].

[garys]

One issue I had was when I broke the leaf spring on my quadrant assembly. I ordered a new quadrant and installed it using my old worm gear. Apparently the old gear was worn enough that I could not get them to mesh smoothly. Then, I ordered a new worm gear to try with the new quadrant gear and they now mesh and turn smoothly. Matched parts either new or worn seem to work, but not one worn side and one new side.

[jsburger]

Yes the 'Mystery" is the resultant rpm figures. The overall range(1180 - 4720)[4:1] is less than 'typical'(700 - 5200)[7.4:1].

The difference between the posters speed measurements and the SS stated speeds are (high-low) both 480 RPM. Maybe his tachometer is off?

[JPG]

Yes the 'Mystery" is the resultant rpm figures. The overall range(1180 - 4720)[4:1] is less than 'typical'(700 - 5200)[7.4:1].

The difference between the posters speed measurements and the SS stated speeds are (high-low) both 480 RPM. Maybe his tachometer is off?

Interesting observation! However 'Low' reading high by 480 while 'high' reading low by 480. Different directions.

I think we need to know more about the tach measuring procedure.(which shaft, what reflector . . .)

[jsburger]

Yes the 'Mystery" is the resultant rpm figures. The overall range(1180 - 4720)[4:1] is less than 'typical'(700 - 5200)[7.4:1].

The difference between the posters speed measurements and the SS stated speeds are (high-low) both 480 RPM. Maybe his tachometer is off?

Interesting observation! However 'Low' reading high by 480 while 'high' reading low by 480. Different directions.

I think we need to know more about the tach measuring procedure.(which shaft, what reflector . . .)

Yup. Didn't think about that.

[JPG]

Thinking back to earlier post where the range of the floating sheave was restricted by a dimension change to the (floating sheave 'snout'?) That adds up to a smaller range.