With the slide working well I did a search for parts and after a few modifications did a mock up assembly of how the clutch and tension assembly will work. Here are a few pictures.
First one is the slide, tapped to accept the tension screw, and on top, the 4 motor mounting holes.
Here the motor base slider is complete and I set up a mock-up of the clutch and tension assembly. I am using two heavy toggle clamps with a 2" stroke. In this position the toggle clamps are retracted and locked. This will be the operating position.
Here the toggle clamps have been released and extended 2", this pushes the motor slide 2" which loosens the belt and stops power transmission to the saw. No springs needed here, the toggle clamps positively and quickly loosen the belts to stop power transmission.
OK so I have retracted the toggle clamps to run the saw but the belt is not tight enough and it's slipping. Thats where this screw, connecting the toggle clamps to the slide comes in. This screw is threaded right on one side and left on the other, I salvaged it from a scrap yard over 30 years ago (just waiting for this project, ha, ha). So to tighten the belt turn the big nut I tacked to the shaft right, to loosen left.
Should be a quick job to finish this assembly tomorrow.