Shopsmith Forums

My new car is a Subaru Outback with a Continuous Variable Transmission (CVT). As best I can tell (I'm no gear head), the heart of the CVT is two conical pulleys connected by a belt. Sound like a Reeves pulley system by any other name.

Yep!
My wife drove a Jeep Compass for nearly 10 years, having the CVT. I thought the same! No problems ever with that powertrain.

Chris

I assume the ratio control[control sheave] is output load determined[quill shaft torque]?

I've heard that some CVT's can run the belt in compression. That's a pretty neat trick. But per this article, the Subaru CVT does indeed look like a Reeves drive. The belt is steel, so perhaps it can transmit power on the compression side?

I test-drove some Subaru's when I was new-car shopping back in 2015. I knew they had CVT's, and was surprised to find that they rev & shift pretty much like a conventional automatic transmission. So I asked the salesman about that. He told me that the initial versions of the transmission did keep the torque and RPM optimized as you would expect, with no discrete ratio shifting. But customers didn't like that, as it felt and sounded odd to them. So Subaru wound up programming the transmission controller to emulate a conventional transmission, so that it felt "normal" to people.

Two variable pulleys equals Reeves Drive. If you do a search for CVT Transmissions you will see the system and one of the narrators refers to it as a Reeves Drive. The belt in the system is very unique in that it is an assembled steel belt and is also directional. The system varies the pulleys using hydraulic pressure. U Tube has a bunch of informative videos about CVT's. I just got a Kia Soul S with Kia's intelligent CVT which is said to have a chain instead of a belt. Most CVT failures seem to involve belt failure. picked up my new baby on July 31(my birthday) so I have only had a couple of days but I really like it so far.
Bill V

wa2crk wrote:I just got a Kia Soul S with Kia's intelligent CVT which is said to have a chain instead of a belt.

They call it a chain belt, apparently to differentiate it from a 'push belt', but it is still just simulating a flat belt. It resembles a chain in the sense of a set of links connected with rollers rather than the segment and ring construction of the push belts, although it's still quite different from a conventional chain.

The sheave concept is also used in lower tech forms in a lot of lawn tractors with pulleys like this: https://www.amazon.com/MTD-956-04015B-V ... B0017OPOBI

It's very much like the spring loaded lower sheave on a Shopsmith, but these are used as a intermediary between two other fixed pulleys.

edma194 wrote:

wa2crk wrote: . . .

It's very much like the spring loaded lower sheave on a Shopsmith, but these are used as a intermediary between two other fixed pulleys.

ala Power Station.

dusty wrote:

dusty wrote:

JPG wrote:

ala Power Station.

Where are the two fixed pulleys in a Power Station?

That diagram is great to see. Never seen a Power Station but wondered about using a pulley like that to make my own variable speed control. Considered that for my Delta bandsaw but it was easier to buy an old Shopsmith. The linear inline pattern of pulleys seemed to make sense, so that confirms it for me. Lawn tractors tend to have the variable pulley at the end of big swinging arm for some reason. I am impressed that pulley works with much higher HP than we'll see in shop machines.

I did get what I think is a Power Stand with a SS bandsaw I got for parts. No speed changer in the box, just a couple of stacked pulleys. Did they sell those directly or was that just for 3rd party sales?

The Power Station and the Power Stand are two different animals. The Power Station has a variable speed power unit similar to the Shopsmith although the innards are a bit different. The Power Stand is only a stand with the cast metal mounting foot and it comes with stepped pulleys and the ratios are selected for the application. Bandsaw, belt sander, jointer etc.
Bill V