Lawn Tractor Transmission

A quick ebay search revealed a lot of single-speed transmissions for self-propelled push mowers, a lot of heavy-duty transmissions for $100+, and not much in between. No luck on my local craigslist either. Any other suggestions? The original 3-speed is looking like a pretty good option right now.
 
I did a search and found that trans is for a commercial duty walk behing mower, it also fits Snapper #7026231 I think. I doubt the "Clutch" is very robust and the other weak link would be the bushings on the output shaft, although a lot of cheap riding tractors use plain bearings on the axle output shafts (3/4 rather than 1/2) -they sometimes wallow out but the ones I have seen are old.
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But it does have real bearings on the input shaft.

Online these babys go for 190 bucks new.
I suppose the clutch could be left engaged and the clutching done elsewhere.
Kind of interesting to me too.
Cut one output shaft off. Adapt a drive pulley, get a 1/2 inch bore out put sprocket and mount it. From what I recall these take a special grease. I think it is called Betonite- real gooey black stuff.
Need to make sure it has a lot of grease in it and they are trickey to get back together once apart.
 
BaB- it'll be quite a while before I get another bike together to do it.
I had one of these gearboxes (single speed) in the garage after I stripped a mower and thought about using it and never thought about turning the engine to mate - great idea.
 
So here's what I think I'd need:

-3-speed lawnmower transmission: $20 + $11.54 S&H from Surplus Center

-7 tooth #41 sprocket with 3/8" or 10mm bore (think I can bore out a 3/8" sprocket to 10mm?) for the input side of the transmission: $6.41 from McMaster-Carr

-15 tooth #41 sprocket with 1/2" bore for the output side of the transmission: $12.18 from McMaster-Carr

-41 tooth sprocket for back wheel: $13 from ThatsDax

-6mm rag joint: $8 from ThatsDax

-55" of 415 chain: $12 from ThatsDax

+ $9 S&H

Total: $92.13 (aka outside my current budget)

Pretty much everything else I already have or can make myself (motor mounts, throttle, chain tensioner, gas tank etc.). But I'm wondering whether it might be better to get a two-stroke bike kit from ThatsDax or somewhere similar, and then sell what I don't need, rather than buying each individual part. Because I'd like to have a real metal tank rather than the plastic one I've got, and I'd rather have a real twist throttle than an old bike brake lever. I might also need wider cranks (haven't measured that).

Does anyone have a cheaper source of parts that I've missed? Maybe I'll put a "wanted ad" in the "Swap and Shop" section. If anyone is in the Denver area I wouldn't mind trading bicycle parts or Briggs & Stratton parts towards what I need.
 
discontinuuity said:
So here's what I think I'd need:

-3-speed lawnmower transmission: $20 + $11.54 S&H from Surplus Center

-7 tooth #41 sprocket with 3/8" or 10mm bore (think I can bore out a 3/8" sprocket to 10mm?) for the input side of the transmission: $6.41 from McMaster-Carr

I'm considering experimenting with one of these too.

I think you may need a much larger sprocket on the input side of the tranny and a smaller one on the engine.
If you can add a pillow or flange bearing to the output shaft, outboard of the drive sprocket, the stress on the axle bushing would be greatly reduced

What about a clutch? This tranny's clutch, I think, is just in or out, no friction to soften engagement.

I would use a v-belt primary drive with a manualy controled idler for a clutch. Easy to change ratios too. A cent. clutch would work also but may require different method of shifting on the fly.
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I've already got a go-kart style centrifugal clutch on the motor, with a 10-tooth sprocket. I figure a 7/10 torque reduction should be enough.
 
How easy would it be to drill a 3/8" sprocket out to 10mm? Would I need a drill press or lathe, or could I just use a hand drill with a 10mm bit?
 
If the sprocket has no keyway, a drill press will do it. A keyway will cause the bit to wander towards it and the hole will end up way off center. I know this from experience.
A lathe and a small boring tool will work, and also a better fit can be had. Standard drilled holes are usualy kinda loose for a snug shaft/pulley fit.

Is there any chance that you could buy a sprocket with the bore size that you need?

I'm very interested in how this tranny performs, please keep us posted.

Wayne Z
 
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From the store's description it looks like the input shaft is 10 mm and the output is 1/2". I don't know why they would mix metric and standard like that, but that's the way it is. My engine and clutch are all in inches, with 415-type chain. Unless it would work to use a metric sprocket with 415 chain, I'll try adapting the 3/8" sprocket. I might be able to get access to a lathe and milling machine.
 
I have had zero success drilling pulleys bigger on a drill press- bad runout. But if it was chucked up in a lathe and drilled - it would be fine.
 
professor said:
I have had zero success drilling pulleys bigger on a drill press- bad runout. But if it was chucked up in a lathe and drilled - it would be fine.
Click to expand...

If you try to drill a pulley that has a keyway,in a lathe, with a standard bit, you may still have lots of runout. The bit will flex annd drift towards the keyway. It would have to be bored with a small boring bit, taking off a small amount in each of more than several passes, to get a true centered bore.
I have done this with short stubby bits and or center drills, with fair results though

No keyway makes the job way easier, unless you need to have a keway for the tranny. Then you might as well take it to a machine shop to have it fitted.
 
Well it doesn't look like the transmission has keyways on either the input or output shafts. I was thinking about cutting keyways, but I'm not sure if that would work. I guess I could always weld the sprockets on, or drill holes through perpendicular and bolt 'em.

I think I can get sprockets with or without keyways.
 
Welding could work possibly, if you are any good at it it is definitely a good option. DO NOT drill through the shafts. This will greatly compromise their strength. I'll put it this way, if it was the strongest way of attaching things to shafts, the manufacturers would have already done it. Hope that helps. It is also possible to machine keyways but I've never done it so I don't know what it takes.
 
If your careful and have good dexterity, you should be able to grind a keyway with a dremel, thick or stacked cutoff wheels, and a wheel dresser to keep them square edged. Might finish up with a file of the same dia. as the key.
 
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I don't have a dremel or much in the way of power tools at my house, but I might be able to use a milling machine to cut a keyway. I'll have to ask my friend if he can help.
 
I have just locked the set screw down to leave a mark on the shaft- remove the pulley and grind a small flat where the screw goes. Works fine on my HF powered bike.
 
Im buying a new peerless 700 trans and a 90 degree gearbox for my board tracker tomorrow will take a two weeks probable to get here Medellin, Colombia.
 
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