CVT going to a 5 or 6 speed....For high speed tractors: Vario drive clutch, going to MST205 or 206

I've been thinking, and you all ought to know that's never good... heh. This thought comes from a complex thought so here's the Stephen King novel.

Anyways today we had a '98 craftsman 42" tractor come in for service. Guy just bought it as a new grasscutter, wanted some bugs worked out [missing engine mount bolt, no headlights, oil and fuel change [bad gas] attest n tune, general pressure wash cleanup] He also noticed that it had a burned drive belt and it slipped in high ["7th"] gear.

Got all his problems fixed, lights were a pinched wire in the hinge, mount bolt was loose and sheared off in the block, removed with pliers and replaced, blew out carb, then onto the drivetrain.

This tractor had MTD's variable pulley setup that you can shift on the go [upshifting only]. Has a gear shifter on one side, marked R, N, F. Newer MTDs with this have what I call a lightswitch shift lever on the dash. The burned belt was because it was on the wrong side of a retainer loop, and it slipped in 7th because the belt overheated, stretched, and wouldn't seat properly on the variable pulley: changed belt and rode around for a bit - no problem.


So what I have in mind is this:
A high speed tractor with an MST-205 or 206, but with the variable pulley and double belt system in place of the usual 1 belt, two pulleys+clutch idler setup. Think about it, infinitely variable range in every gear. It would make it easier for you to start in each gear, even at speed, and have a higher final output rpm at the axles at the same engine rpm. Like a manual CVT setup with a gearbox on the output end. So in this case, I'd have a "7" speed inputting to a 5 or 6 speed. That would make for one seriously fast tractor I think, especially with a newer OHV Briggs, like a 19.5hp model 31, 500cc single, they're powerhouses.

On the operator side of the machine, you'd have your usual gas pedal on the right, clutch on the left, and gearshifter at the seat [or center console on some]. To shift it, you'd put it in first gear, let the clutch out till it catches in its lowest "range", hammer down on the gas pedal and slowly let out the clutch till its in it's highest range. push in clutch, shift, accelerate till your rpms are high, let out clutch for more speed in the same gear.

Some of you might be thinking "But jack, on my sh!t on the go trans, clutch in make the brakes go on full" that's because the brakes are in the 1 speed forward/reverse trannys they put in stock variable drive tractors. if the double belt system is implemented on a 5 or 6 spd gearbox, it wont brake when you clutch in to shift, just spring return to low range pulley position, and disengage.

Just a very on-the-spot overcomplicated thought, I'll try it the first chance I get though, I've found stock vario-drive mowers to be the fastest stock ones around, that '98 craftsman had 7spds forward and reverse!

I did it just like you said, but I can't post pics, but it works good and it goes 15 mph with the stock pulleys.

We're you thinking on keeping the speeds for the vari drive?  Because I was going to make a 35speed mower out of a seven speed vari drive and a mst 205.  Check the link in my Sig labeled the beast for more info.

I believe it's been done. Pretty sure I've heard of it.

I hesistate to call the vari-drive a CVT. It is, and it isn't. In it's base configuration, you set the ratio manually, via a lever. A CVT operates automatically, and continuously. (Hence the "C" in "CVT")

Now- for a confirmed CVT/tranny combination- watch my MULEII build. Comet 40 CVT, driving Peerless700. True automatic operation, the 700 will be a "range control".

The Vari drive is used in conjunction with the gearbox. So I'll just run you all through the operation of my hypothetical MVT/206.

Fire up your tractor, regular tranny is in neutral, and clutch pedal is locked down [non braking park]. push clutch in, place trans in 1st, let clutch out till it grabs the variable pulley's innermost surface [when it feels like you've let a typical clutch out], hit the gas pedal, as engine rpms increase, let the clutch pedal out more and more. press clutch in all the way as you release the gas pedal. upshift to 2nd. release clutch pulley slowly while building rpms, upshift to third and so forth. slowing down with the variable pulley is easy, just push the pedal in slowly and you're effectively downshifting the MVT while keeping the trans in the same gear.

You all know that the variable pulley's ratio or "gear" is determined by clutch position, so setting one up on a tractor should be easy really, especially in a tractor that already has a manual "automatic". Just slap in a peerless and hook up your belts as normal.

seems like it would work.