Food for thought on Variable speed...for the mechanically inclined

[Rob Frink]

I found this in my archives....it is my original KMG prototype that I fitted with a Vari-speed system. Yep, same concept as the Variable speed Bridgeport Milling heads.

Boy....time flies! I think this is about 4 years old and I don't remeber all the details. I think it had a speed range of about 3:1.

Or about 3000-1000ft/min.

I made a .mpg movie of the concept and used it in my shop for about a year or so...


Here is the link to the movie...I hope it works.

http://beaumontmetalworks.com/grinder/varispeed.mpg

http://beaumontmetalworks.com/grinder/varispeed.mpg

Just food for thought...hopefully to inspire the homemade shop guys.

Sincerely,
Rob

[whv]

the movie works fine, rob. but i'll have to stay with pulleys.
thanx

[Tom Militano]

Rob, that's pretty neat. How does it work exactly?

[Geno]

That's neat Rob.
You made it look easy.

[Jamey Saunders]

John Deere uses something similar for the CVT (continuously variable transmission) on the "Gator" utility vehicle. Polaris also uses the idea for the CVT in their ATVs, and I think they are also used in snowmobiles.

Basically, it's two variable pulleys. I'll try to draw some pics and get them up.

[Bob Warner]

That is great.

My little brother is a great fabricator and he built a grinder and used the five speed transmission out of a lawn tractor to get variable speed out of a grinder. It was ugly but it sure did work great.

It even had reverse.

[Rob Frink]

Jamey...you got it! The VARI-pulley came from a lawn tractor...I think it was a MTD product with 10hp.

[Jamey Saunders]

The following is a little different than the CVT ideas, because they rely on the load to determine the ratio (the more load, the lower the "gear"). But here goes.



The above picture is of the double pulley in overdrive. The pulley on the left is the one connected to the grinder, the one on the right connected to the motor. The black squares are the belt, and the center part is the moveable part of the pulley. It can move left or right, and as it does so, it makes one pulley larger and the other smaller.



This picture is of the variable speed in middle speed. The moveable part is in the middle, and the two pulleys are the same size. Basically 1:1 "gear" ratio.



This picture is of the transmission in underdrive. The variable part is moved all the way to the left, making the motor pulley large and the grinder pulley small.

Basically, this allows you to vary the size of the pulley on your motor. Works pretty well, but I believe you need a special belt. As the pulley gets "larger", there is a larger gap that needs to be covered, and you need a wide belt to accomplish that.

Maybe Rob will comment some more on the specific construction of his CVT for the grinder. If it is inexpensive enough, I think it would be a popular addition for folks who don't want to spend the money on electronically variable speed.

[Jamey Saunders]

...and here's a manufacturer for CV pulleys:

http://www.hi-lo.com/pages/prod_AandMA.html

[Gary Riner]

Rob
I heard that you were working on a new horizontal edge finishing grinder. How about posting a picture?
Thanks
Gary

[Darren Ellis]

Hi Gary,

Check out Rob's web site:

http://www.beaumontmetalworks.com

Alternatively, you can just come over to my shop after the Batson Symposium and check one out in person! Yep, bringing one of those nice baby's home with me! Although, if you do come over, you'll have to promise not to laugh, my shop pales in comparison to your shop/machine shop/aircraft hanger!

-Darren

[PaulD]

Rob,

I have seen this type of drive on machines over the years, if the moving parts are kept lubricated and clean, belt life can get close to that of a stationary setup. With a 2" wide belt, you can get about the same ratios with only one belt and one moving pully, but the adjustment mechinism has to be coaxial with one of the rotating shafts.

OK, but can you build and sell it at a cost advantage compared to an electronic VS drive?

How about as a stand alone "adaptor" that could be used for various machines or the DIY crowd.

Just looked at the link Jamey put up, I have seen set ups with a crank (screw) adjuster push/pull on the sliding sheave. bulky but simplier to build, your two pully set up (spring loaded I assume) solves some of the issues, just takes up more space. The more I think about it, the more I like your set up for cost and service conciderations.