Author Topic: Question about varidrive  (Read 392 times)

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Offline BuiltTough

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Question about varidrive
« on: April 08, 2018, 12:08:31 PM »
Hey guys, I’m just getting started on a build for our local mower race, and I know a lot of guys don’t recommend the varidrive but I still have some questions that I can’t seem to find the answer to.

1: I notice in a lot of rulesets centrifugal clutches and torque converters are prohibited. Why is that?

2: is a varidrive pulley considered a torque converter?

3: what I’d like to do, is utilize a varidrive pulley in my drivetrain, What I’m thinking is fix the varidrive pulley at a fixed location between my motor and my transaxle. I would use a spring loaded idler to take up the slack in the varidrive to trans belt when disengaged, and have my clutch provide the tension/take up the slack on the motor to varidrive belt when engaging the drive.

My thought is that this would give me control of my acceleration (provide the fast takeoff) with the clutch half released, and allow me to have the good top speed with the clutch fully released.  Would this theoretically work?

A little detail on the specs of the  build to help answer any questions. I will be running a 24HP b&s pro series vertical shaft, with ether a 7” or 8” pulley powering a 5speed transaxle (welded diff, and high performance gear oil) with a 2.5”-3” pulley on the trans.

The varidrive is a 6”x2.5” pulley I believe so in theory it would give me about a total 1:1.33 ratio starting and up to a 1:7 ratio fully engaged. (Not including transaxle gearing)

I will be custom building the front end and installing at minimum a rear disc brake. This is the towns first race ever so I really want to show them what’s possible “within their rules” to get the other gear heads motivated.

My last build was years ago and was a simple stock mower with a pulley swap (7”-3”) and 25” tires off my big old Honda big red. I want this one to be a little more bad





Offline cycloneracer

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Re: Question about varidrive
« Reply #1 on: April 08, 2018, 05:29:26 PM »
First welcome!

Second I modified your post as we don’t curse here.   No big deal.  Just don’t let it happen again.

Centrifugal clutches are allowed to run in certain classes.  Rule is there to retain the “mower” part.   And to keep cost down.  A belt clutch is far cheaper than a centrifugal clutch.

Scrap the vari drive.  Even fixed it won’t last long.   Get a pulley that the belt is designed for. The reason vari drives don’t work as the pulley can move so the belt doesn’t “fit” correctly.   It works for mowing the yard but not for speed. 

You won’t want to use the belt clutch while racing either.  Any time the belt is slipped it will build heat.  Enough heat and it will explode. 






Hey guys, I’m just getting started on a build for our local mower race, and I know a lot of guys don’t recommend the varidrive but I still have some questions that I can’t seem to find the answer to.

1: I notice in a lot of rulesets centrifugal clutches and torque converters are prohibited. Why is that?

2: is a varidrive pulley considered a torque converter?

3: what I’d like to do, is utilize a varidrive pulley in my drivetrain, What I’m thinking is fix the varidrive pulley at a fixed location between my motor and my transaxle. I would use a spring loaded idler to take up the slack in the varidrive to trans belt when disengaged, and have my clutch provide the tension/take up the slack on the motor to varidrive belt when engaging the drive.

My thought is that this would give me control of my acceleration (provide the fast takeoff) with the clutch half released, and allow me to have the good top speed with the clutch fully released.  Would this theoretically work?

A little detail on the specs of the  build to help answer any questions. I will be running a 24HP b&s pro series vertical shaft, with ether a 7” or 8” pulley powering a 5speed transaxle (welded diff, and high performance gear oil) with a 2.5”-3” pulley on the trans.

The varidrive is a 6”x2.5” pulley I believe so in theory it would give me about a total 1:1.33 ratio starting and up to a 1:7 ratio fully engaged. (Not including transaxle gearing)

I will be custom building the front end and installing at minimum a rear disc brake. This is the towns first race ever so I really want to show them what’s possible “within their rules” to get the other gear heads motivated.

My last build was years ago and was a simple stock mower with a pulley swap (7”-3”) and 25” tires off my big old Honda big red. I want this one to be a little more bad



Paul Krueger

****2017 USLMRA FXT points Champion****

#150 Worlds First "sidewinder" FX (now dismantled)

#150 FXT  Sponsored by Zach Kerber Machine. http://zkbrmachine.com/

Easy Parcheesy Racing

Offline BuiltTough

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Re: Question about varidrive
« Reply #2 on: April 08, 2018, 06:16:46 PM »
What else would you use as clutch? Everything I’ve seen in most of the builds is a 2 pulley clutch on the belt.

I’m aware of the reported issues with rapid belt deterioration on varidrives, and I have a backup plan just in case I can’t make it work. I don’t know what belts have been tried in the past, or if anyone has attempted modification on the pulleys, or what other things have been tried since searches only seem to say “they don’t work for racing” and “you’ll blow through belts”,and never what was tried to make it work. I have some ideas, and some theories that are solid on paper I want to try, and if it fails, then plan b will take effect.

I mainly wanted to determine if they were considered a torque converter. I also don’t plan on running standard garden variety belts (pun only half intended)  as most off the shelf belts are light duty belts not really intended for high rpm high heat applications. (Again I don’t know what others have tried)

I don’t have all the answers, only a dangerously basic understanding of engineering principles, so while I think I have a fairly solid grasp for the most part, I know I will have questions along the way. Nothing ever works as well in practice as it does on paper.


Offline cycloneracer

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Re: Question about varidrive
« Reply #3 on: April 08, 2018, 06:27:17 PM »
Vari drive works the same as a torque converter.   Only there is 1 movable shive.  Unlike a torque converter that has 2. 

I’ve raced mowers for over 15 years.  I’ve never seen a vari drive that worked.  Several have tried.   All failed.  The belt doesn’t sit in the pulley correctly and slips. 

The trans axle on the vari drive isn’t good either.  Only 1 gesr and they are very weak.

You will need some kind of clutch on your belt.  A 2 pully system works best as it provides more grip and a better release.

Best bet is to just buy a set of “A” pulleys and run a Kevlar/Amarid coarded belt. 

Paul Krueger

****2017 USLMRA FXT points Champion****

#150 Worlds First "sidewinder" FX (now dismantled)

#150 FXT  Sponsored by Zach Kerber Machine. http://zkbrmachine.com/

Easy Parcheesy Racing

Offline BuiltTough

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Re: Question about varidrive
« Reply #4 on: April 08, 2018, 07:25:52 PM »
I won’t be using a varidrive transaxle, the mower chassis I’m building on has a 5speed transaxle. The varidrive is going to be an add on.

Worst case scenario, the varidrive comes out, and I run a new belt from Motor to trans. But that’s my last resort plan if plan A, B, or C doesn’t work out.

One should never be dissuaded by the failed attempts of others, or innovation would never occur. Right?

There is nothing in this world that can’t be done! Only things that someone hasn’t figured out how to do yet.

Offline cycloneracer

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Re: Question about varidrive
« Reply #5 on: April 08, 2018, 07:56:43 PM »
Agreed.   

Good luck. 

Paul Krueger

****2017 USLMRA FXT points Champion****

#150 Worlds First "sidewinder" FX (now dismantled)

#150 FXT  Sponsored by Zach Kerber Machine. http://zkbrmachine.com/

Easy Parcheesy Racing

 

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