Shopsmith Forums

RobertTaylor wrote:Look closer JPG. Do you see the shaft touching he coupler? Think mechanical, not digital.

I did look close, but, was unsure of what I was seeing.

If that 'black' thing is a shaft of the tach, then it needs to be at the rotational axis, not off to the side as shown in the pix.

If the tach shaft is rotating at the circumferential speed, the tach shaft will rotate at a higher rpm than the shaft speed being measured by the ratio of the tach shaft od vs the off center distance(x2).

Paper work says non contact

Ed

reible wrote:Paper work says non contact

Ed

And it has a 'laser'.???

Some good reading material. Answers at least a couple questions.

http://www.instruments.nidec-shimpo.com ... LR_S12.pdf

Have you done a laser coupled speed test???

I'm betting on either sheaves and belt OR no real problem.

What is your upper spindle speed when the speed dial is between R & S? I think it should be about 4100 rpm.

Asked a different way: When does your upper spindle speed equal your motor speed? This is what I refer to as the cross over point for the Idler Sheave.

Hi Dusty,

Thanks for posting the link. That is the manual that came with the tach.

The tach uses a laser to measure reflections and calculate rpm, fpm, etc. There area variety of attachments for measuring shaft speed, linear belt speed or length. It works in contact and non contact mode but in either case it works the same way. It measures reflections and then calculates. In non contact mode you have to add a reflective strip to the thing being measured, shaft, pulley, etc. Then remove the cap and shoot the laser at the reflective patch so it can read the reflections. For contact mode the cap is on. Inside the cap there is a screen and reflective sections. I'll send a picture of the inside of the cap when I get home tonight.

Since I could easily access the shaft and it had a centered indent, I used the direct contact method. I used the conical rubber shaft center adapter and applied directly to the center indent on the shaft. There was no offset between axes of the shaft and tach.

I'll check the upper spindle speed when between R-S speed tonight.

Direct contact with the rubber tip in the center is what we had back in my high school machine shop class (1966) I thought that is what I was seeing. Also very few things were digital back then. Bob

I know the belt looks to be in good shape, however how wide is the belt across the flat side?

If it is less than 1/2", the ratio changes on the sheaves as the width of the belt decreases and it sinks deeper into the valley created at either end of the speed range.

A narrower belt will allow the belt to run deeper in the groove at both ends of the spectrum which will make the speed change off at either end.

There is a point of no return where it can jam, and doing that under power can cause some headaches.

Check the belt, then go through the speed dial setting process Shopsmith recommends.

Everett