Lawn Tractor Transmission

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discontinuuity

New Member
May 24, 2010
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Colorado, USA
I saw this transmission for cheap while looking for some sprockets:

Surplus Center - 3 SPEED TUFFTORQ TRANSMISSION

What do you think? Could you use one of these on a motorbike, maybe with a Briggs engine? Would the clutch and gears hold up to the power?

I seem to remember seeing a motorbike with a horizontal-shaft Briggs engine and one of these. They had turned the motor sideways, so the crankshaft pointed front-to-back, and put a sprocket on the cut-down axle.
 

cannonball2

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Oct 28, 2010
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The older riders used a small box type 3-5 speed trans. that was pretty tough. Was chain drive on the final(usually #40/41) with a belt input. The input was on the bottom however. If you could figure how to mount it you could use a mower engine which are about as cheap as it gets. Check ebay.
 

cannonball2

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Oct 28, 2010
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Definately not syncro, they shift by sliding shift keys. They can be shifted on the fly if done properly. I would think in conjuction with a centrifugal clutch it might be feasible. If the bike were geared to be able to pull from start in the top gear then all the lower gears would be suitable for hill climbing/ trailer towing. If the 2nd highest gear was the pull away gear then you would have an overdrive which could be shifted into once top speed was obtained in the pull away gear.
 

discontinuuity

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May 24, 2010
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Colorado, USA
I found a few on Ebay but they were a little expensive and most look like they'd be hard to mount on a motorbike.

I wonder if the small one above might work with a smaller two-stroke engine. Either way it would probably have less torque going through it in a motorbike than on a lawnmower, since it would be spinning faster. Or maybe I'm thinking about it wrong.

I thought about the synchromesh thing too. Mostly I'd just like to have a right angle gear box with a built in reduction (so I can fit the engine in a narrower space) and clutch. Being able to shift is a bonus, and I think I could learn to double-clutch if need be.

If anyone knows about the motorbike I first mentioned, please let me know. I haven't been able to find it.
 

wayne z

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Dec 5, 2010
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I think that transmisson is for a larger, commercial walk behind mower. Most of the cheaper self propelled mowers don't have different gears. This may be a constant mesh tranny, If so, shifting on the fly can be done with proper throttle control, just like a motorcycle

I also have considered experimenting with one of these. The Briggs engine is about 2 inches narrower in a mb frame with the crankshaft fore and aft versus sideways. Thwy're cheap enough. I may still try one.

Other 90deg gearbox I've contemplated is one from an angle grinder. Most have around 4.5-1 reduction.
 
Last edited:
Dec 18, 2009
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new jersey
cannonball2 knows of the legends. i saw a bike with one on youtube, the bike was green, and stretched to accommodate the 5-speed, was that the bike you saw, discontinuuity? i think there was an old man with a red stretched bike that used the same unit....or it might be the same bike w/ different paint. i dont know because i can't find the video anymore. great units, in my opinion....the gearbox w/ chain drive is 7 inches wide...it should be 6 inches if there is only one output shaft
 

discontinuuity

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May 24, 2010
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Colorado, USA
Yeah, I think the one I saw was red, maybe with an American flag on it?

I don't think this transmission has a differential, since it says "solid axle" in the description. After a little bit of research, it looks like the transmission is probably a Tuff Torq model TL3C, with a rated torque input of 3.6 ft.-lb.

Three-speed transmission - Tuff Torq Corp.'s new TL3c - Brief Article | Diesel Progress North American Edition | Find Articles at BNET

Since my own Briggs engine makes about 5 ft.-lb. I doubt this transmission would hold up, unless maybe I geared up the primary drive and geared down the secondary (so that the transmission was turning faster but with less torque). Or if the transmission has a huge safety factor designed into it.

A 50cc four-stroke or a small weed-whacker engine would probably work fine, since those aren't very torquey.
 

cannonball2

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Oct 28, 2010
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The biggest issue with most mower transmissions is the input and output are at 90 degrees. Since most mowers use a vertical engine its not a problem. In a bike the best suited trans has the input/output in the same plane. Not to say it is not possible, but if you flip the above mentioned tranny to accomadate the engine, then the output is vertical, a real issue.
 

discontinuuity

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May 24, 2010
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Colorado, USA
The idea would be to flip the engine 90 degrees, not the transmission. This is because the engine is wider than it is long, so it would fit better sideways in a bike frame. So the output would be in the same plane as the back wheel.

If I had a 1.5:1 gear-up between the engine and the transmission it would probably fix any reliability problems (unless the bearings in the transmission have a low RPM limit).
 

cannonball2

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Oct 28, 2010
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These transmissions routinely run 5+ hp so thats not an issue. Most walk mowers operate in the 3300rpm range to meet blade speed requirements. I have never really paid attention to pulley ratio from crank to trans, just assumed a 1:1. Briggs engines will easily spin in the 5k range ungoverned. assuming 5k@ 1.5:1 the trans is subject to 7.5k input. I have never torn one of these down, just replaced them as a unit under warranty. Generally this type of trans has a Torrington bearing on the input and the axles either run in bushings or directly in the case. Keeping the trans well lubed would be paramount. 00 grease or Bentonite would do it. There is generally percious little from the factory. Seems feasible from an rpm stand point, but there is a great deal of loading difference from a 65lb walk mower to a 200lb+ bike and rider.
 
Dec 18, 2009
97
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new jersey
the trans on both those bikes(green john deere theme bike, old man with red bike and flag) is the peerless 700. they are the only ones to run them on a bike and put them on the internet.(to the best of my knowledge) my mistake, their 7 inches wide, and each output shaft adds an inch...there isn't a differential on a 700, just a sprocket coming out one side, but certain parts from trans-axle models are interchangeable (gear-sets/shift keys/counter shafts/shift collars etc) i could go on all day, because like everyone else, i want more then one speed.
 

discontinuuity

New Member
May 24, 2010
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Colorado, USA
http://www.sears.com/shc/s/p_10153_...9x00001a&ci_src=14110944&ci_sku=SPM1722674001

Well, $188 is outside my budget, but that transmission would definitely take the torque. And of course it's always good to have reverse on your motorbike ;)

Do you have a link for either one of those bikes with the 700 transmission?

I wonder if the 3-speed would work better if I put ball bearings in it. It wouldn't be too hard to bore out the bushings and press-fit some bearings in. I might need to weld the differential if it has one too.

I'll have to do some math on the gear ratios etc. but from what you've told me it would probably work on a motorbike. The max torque I'll be getting out of the engine will be 5.25 ft-lb (and that's optimistic, since the engine is old and I'm at high altitude), and I don't think it matters how much the bike weights. If I remember my physics correctly, force = mass x acceleration. The force (or torque in this situation) should stay the same, but since the mass (the bike's weight) is more than that of the mower, it just won't accelerate as fast as the mower.
 
Dec 18, 2009
97
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0
new jersey
thats why you remove the reverse chain....if you have a trike like mine(or go-kart)....you'd keep it. 188 is way out of my budget to, the units i have were free or cheap because i frequent junkyards. i can't find the video anymore either, but you remember the trans was turned on it's side so it looked taller then it was wide, from the side it looks like the shape of a nascar track(oval with straight sides)and a chain went directly from the trans to the back wheel.i think he painted it black to go with the engine to, which faced front to back, and would definitely baffle someone at first glance.(i thought it made a shrouded engine look good on a bike) the 700 can send lawn tractors barreling around a track at 25 mph in 3rd gear with live axle setups, kickin dirt and the whole nine yards. so i also think they would hold up. its worth searching the peerless 700 on google. i'm trying to find something more bulletproof though, and narrower. the internals from a small dirtbike trans in a billet case (roar)....gonna have to wait for the junkyard to thaw though.
 

cannonball2

Well-Known Member
Oct 28, 2010
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Colonial Coast USA.
This tranny has a clutch, notice the 2 levers. The 700 tranny is used primarily for commercial walk behind mowers where 15+hp is the rule. These units also pull a stand on sulky, so it would be way over rated for bike use. What I was referring to earlier as a "box" tranny was the very small 3-4sp+reverse units used on the cheaper rear engine rider mowers from years back. You can still find em if you scrounge(cheap too, $10-20 range). They would mount like the 700, but are much more compact.