Advice on Belt Tensioners

I find myself wondering why the OP wants a variable speed drive on a grinder. I understand that grinding wheels are best driven at their optimum speed. Too slow and they run soft and wear quickly. Too fast is dangerous. If the speed variation is to allow for different sized wheels then great care is needed to avoid mistakes and over-speeding.

Good question. My application is a flat belt, with only a bit over a foot between spindle and the cone drive. Having a devil of a time figuring out a tensioning system that I can mount on the table between the lathe and the drive.

That would be a monumentally great idea but for the fact that the driven pully is on a Schaublin mount; two legs with the pulley running in between. There's no stable part of the back pulley mount that allows for any kind of tension between the lathe two.

I'm having a devil of a time figuring out a way to mount a tensioning system that pulls down onto the table real estate between the lathe and the driven spindle. there's no place other than the workbench top to mount it that has the required stability, and I'm further handicapped by a "no fire or welding" agreement with She Who Must Be Obeyed.

Any ideas?

I once build a minature vehicle with 4x castor pump up wheels(with tubes) that look like normal tyres. Long story short it was strong enough to pull a car, and one person could not hold it back, speed 0 up to 25Km/h, it used a suzuki waterpumpump overhead valve engine with a centrificle clutch of old brittish green lawnmover, then a V-belt to a 50cc motorcycle gearbox(tuff)(Piston removed), I could change gears back and forth on the fly towing trailors. From the gearbox it was chain driven to the rear wheels to a shaft with a V-Pully on each end then a short V-belt to eack wheen with machined V-Pulley. Now here it slow turning high torgue. No diff, I however played around with where to tention the belts with a jocky pully. The belts were cheap, the tyres expensive. Now out of this spring tentioning I manage to get like a slip effect going around a corner slipping the belt on one wheel to save the tyres.

Initially I bought a bag full of various belts. Now the interesting part started. I tested this on a friens farm, and soon one belt failed after 15 minutes of use, it just stretched from heat called manufacturer-X. Now it took me some two days then to put 2 & 2 together and figured it was only this one make of belt. The belts I settled for was then called Gates-High Power.. It was unbelievable how long they lasted=They looses some of rubber on the inside after many trips but never stretched or broke.

The next interesting part was at work. Our airconditioner(Huge motor using 4x belts} never gave problems in this regard, belts always lasted full service life. Then we start getting failures of belts lasting not longer than 3 months here, they stretch and fell apart literally. On inspection, guess what, it was the same manufacurer I used and discarded... I notified the aircon staff, and they stop buying these, problem solved.

So there can be huge differences between V-Belt qualities when varying speed and high torgue is involved
My experience with V-Belts.