Shopsmith Forums

Help me please.

I am working on a Mark V after having it totally disassembled.

It was in terrible condition due to negligence of a previous owner.

My problem is with the pulley settings.

IIUC when the pulley rotation speed is equal to the motor speed (3450) the pulleys should equal in size and rotating at the same speed.

If I get that condition to exist - at what speed should the saw blade be rotating.

How deep into the pullets should the belt be riding.

With the pulleys at the same diameter they and the idler shaft will be running at motor speed. However, the main spindle does not run at the same speed as the idler shaft. There is 1.6:1 ratio between idler shaft speed and main spindle speed. So the blade should be running somewhere around 2160RPM. Remember that the speed of the motor will not be 3450RPM, it typically is something under that, somewhere between 3000 and 3450RPM depending on load conditions.

That is good news. I knew there was a spindle difference but was not taking it into consideration.

Until I understand better, I will use only the pulley speeds for my calculations.

My confusion comes when I try to track the differences in pulley size. It seems that if one pulley gets 1/4" larger the other should get the same only smaller. That does not seem to be the case.

edma194 wrote: ↑Wed Jul 13, 2022 2:40 pm With the pulleys at the same diameter they and the idler shaft will be running at motor speed. However, the main spindle does not run at the same speed as the idler shaft. There is 1.6:1 ratio between idler shaft speed and main spindle speed. So the blade should be running somewhere around 2160RPM. Remember that the speed of the motor will not be 3450RPM, it typically is something under that, somewhere between 3000 and 3450RPM depending on load conditions.

I don't want to derail the conversation, but I think the motor will run between 3450 at max rated load and higher RPM at reduced load. Up to 3600 RPM theoretical, but never realized. This, in fact, is the great think about induction motors, they have excellent speed control independent of load without an external speed controller.

- David

Yes, that makes sense. 6000RPM should be the no load speed based on the number of poles.

BigSky wrote: ↑Wed Jul 13, 2022 3:21 pm Until I understand better, I will use only the pulley speeds for my calculations.

What are you calculating?

edma194 wrote: ↑Wed Jul 13, 2022 5:31 pm Yes, that makes sense. 6000RPM should be the no load speed based on the number of poles.

3600 makes more sense!

Where did 6000 come from? Yes, 3600 does make sense. I got no idea how I ended up writing 6000.

Thanks for the input. Yes, I do believe that I have confirmed mathematically that the two pulley sets change in equal and opposite direction.

BigSky wrote: ↑Thu Jul 14, 2022 2:14 pm Thanks for the input. Yes, I do believe that I have confirmed mathematically that the two pulley sets change in equal and opposite direction.

There are some good drawings of the mechanism somewhere on the forum that show the range of movement of the split sheaves and some measurements. They move in concert like that because the lower sheave is moved by a spring that will equalize the diameters of the pulleys.