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Converting Vari-speed.


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Mike, On my AC112 and Simp3212 with variable speed the idler pulley works just like on the three speed, pushes up. The variable speed tractors are longer between the 90 degree gear case and the transaxle. To use the three speed OEM belt you would need the shorter brackets of a three speed that connect the transaxle to the tractor, or just get a longer belt. If your getting a lot of belt slip when your pulling you may just need to do a by the book ajustment on the vari drive. Someone on the forum said they pulled with a vari drive and had no problem. Tim
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I am thinking about converting my vari-speed system on my pulling tractor (3314V) to straight pulleys. I would like to have full wrap on the drive pulley (like the standard 3-speed set up). On the vari-speed and shuttle drive the belt tightener pulley pushes down instead of pull up (thus not getting a full wrap on the drive pulley). Does anyone know if the tensioning (clutch) pully brackets from a standard 3 speed (or maybe the 6-speed) will work? Or do I have to fabricate something to get the clutch pulley to pull up instead of push down? Any suggestions will be appreciated. Thanks.
MS
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Mike/Tim,
I don't think the vari-speed tension pulley is supposed to push up. My own B-112, and all the literature I've seen (old and new operator manuals, service manual, parts manual) show it pushing down. This is only a guess, but I think the tension pulley pushes down because it would be too hard to contract the pulleys if the belt were wrapped more completely around them. You've probably already tried this, but would a stiffer return spring help? I realize this would increase pedal pressure. I can't remember off the top of my head if the tension pulley has it's own return spring, or if it relies on the brake return spring, but if it doesn't, how about adding one directly to it?

Greg
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Mike, I'm confused, I had a 3212V and it was the same as my AC B112. Both have the idler pulley mounted below the belt and the spring pulls the pulley up to tension the belt. I have never seen a tractor of that vintage that had a different clutch setup. A clutch setup to push the belt down would seem to be a bad design as less belt would be in contact with the drive pulleys. I remember the idler pulley on the 3212V very well as I had to replace the bushing that the bracket pivoted on. On your vari-drive is the idler pulley mounted between the upper and lower turns of the belt and pushes down on the lower or am I totally confused as usual. Tim
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Tim, Yes my idler pulley is mounted between the upper and lower turns of the belt and pushes down on the inside of the lower turn of the belt.
Greg, I have tried more tension and it seems to create more (at least on the jack stands with wheels in the air) belt slap. There is one tension spring.

Don't get me wrong. The V-drive does work for pulling and has the advantage of adjustment as you go. But a flopping belt is absorping horsepower and not transferring it to the wheels.
Last night I put the V-drive back on and adjusted it different than the book specs. This has potential! I have increased tire speed from a max. of 275 ft per minute to 426 fpm. in 2nd high. I never loaded the engine down before and now I should be able to. I'll keep you posted. And always looking for more ideas.
MS
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Tim, I am the one that is pulling with a vari drive without slipping, but I do get a lot of belt vibration (belt jumping up and down) I have installed and used straight pulleys (same tensioner pushing down) but I still ended up with belt slap. I helped convert a B212 puller with the tensioner pulling up and it eliminated the belt slap and improved the performance of the tractor. I was hoping the idler pulley bracket was adaptable to this tractor as the convertion to the B212 is very hard to clutch and would not work for my 8 yr old son.
I am very interested in a vari-drive with the idler pushing up instead of down. All of the vari-drive I've seen (B212, 3314V, 3212V) all push down. Did SIM have a shorter vari-drive belt that could be reversed tensioned? The belt I used is too long, and I wonder about "breaking the spine" of the belt bending it backwards.
Thanks Tim.
MS
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Greg, You forced me to go look at by B-112 and your right, the pulley does push down on the belt. I guess I just can't get the image of the clutch on the 3 speed transaxles out of my head. I think the pulley does have it's own return spring but since I didn't know what I was talking about before I should just shut up now. Tim
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Tim, that's too bad. I was hoping it had been changed in a later year or something. I'm sure full wrap would grip better. I was looking at mine this weekend too (since it's in about 100 pieces right now, these things are pretty easy to see). Mine only uses the big spring near the brake band assy. And since the pulley pushes down, there's really no frame to attach a linear spring to, unless an expansion spring was used on a shaft (like the PTO linkage). I was just wondering while writing this if a rotary spring on the idler bracket could be used (probably adapted). I guess anything can be fabricated if you have the right tools, materials and ideas.

Greg
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