Blue Smoke
New Member
I have long been on the search for a small multi-speed transmission more rugged than a 3 speed bicycle hub, yet affordable. Wading through all the Chinese junk and bad reviews led me nowhere. Seeing terribly misaligned, undersized, poorly machined, or poorly designed gearboxes made it seem hopeless. The only thing I could think of that I could afford was a well used transmission out of a riding lawnmower, but needless to say, was far too big.
Then, I just so happened to get a job at a lawnmower repair shop. All of the self propelled ones had a common theme, that of a reduction drive that needed to be opened up and packed with grease at every service. Before too long, it came to me that these would make excellent reductions for bicycles. My only problem was that they were right angle drives using straight cut bevel gears and the output was perpendicular to the input. I would just about have to use a lawnmower engine with a vertical shaft to match it, and those were huge.
Then came another great idea, that of mounting the engine transversely (a 2 stroke Tecumseh) and having the reduction bolted beneath it, with the output running to the back wheel via belt.
That all sounded fine and dandy, until one day I came across one of the better Lawnboy mowers. It had a 3 speed transmission! Not only did it have 3 speeds at a fairly wide ratio, but it contained a reduction of 6:1 or so in the highest speed. It was self indexing inside of the transmission, so about anything push/pull would work for a shifter. The gears inside are about half an inch wide and are ALL made of steel. They have a steel pan that can have mounting lugs brazed on to it. On top of all that, they are fully rebuildable. All parts can be found for them new, so if you manage to find one and it doesn't work up to par the parts could be bought at the local Lawnboy dealer.
These have to be fairly rugged. I have never seen one broken down. They run in the dirt for years on a vibrating lawn mower and don't show hardly any signs of wear when the rest of the mower is totally shot. The only common problems are that of the indexing cam getting worn and it won't shift well, but this isn't even all that common, and that part can be had fairly cheaply and is replaced easily. The other is that of the powder metal bearings on the mainshaft getting worn from dirt exposure, but they are also fairly cheap and easy to replace.
My boss was nice enough to give me one out of a junker to experiment with. I have just started on a bike with the Tecumseh 3 horse and the Lawnboy transmission doing its job. I will report back as soon as I am done.
So, stop by your local shop and see what you can find! It doesn't sound like it has been tried before, so we may have come by a gold mine here...
-Brian
Then, I just so happened to get a job at a lawnmower repair shop. All of the self propelled ones had a common theme, that of a reduction drive that needed to be opened up and packed with grease at every service. Before too long, it came to me that these would make excellent reductions for bicycles. My only problem was that they were right angle drives using straight cut bevel gears and the output was perpendicular to the input. I would just about have to use a lawnmower engine with a vertical shaft to match it, and those were huge.
Then came another great idea, that of mounting the engine transversely (a 2 stroke Tecumseh) and having the reduction bolted beneath it, with the output running to the back wheel via belt.
That all sounded fine and dandy, until one day I came across one of the better Lawnboy mowers. It had a 3 speed transmission! Not only did it have 3 speeds at a fairly wide ratio, but it contained a reduction of 6:1 or so in the highest speed. It was self indexing inside of the transmission, so about anything push/pull would work for a shifter. The gears inside are about half an inch wide and are ALL made of steel. They have a steel pan that can have mounting lugs brazed on to it. On top of all that, they are fully rebuildable. All parts can be found for them new, so if you manage to find one and it doesn't work up to par the parts could be bought at the local Lawnboy dealer.
These have to be fairly rugged. I have never seen one broken down. They run in the dirt for years on a vibrating lawn mower and don't show hardly any signs of wear when the rest of the mower is totally shot. The only common problems are that of the indexing cam getting worn and it won't shift well, but this isn't even all that common, and that part can be had fairly cheaply and is replaced easily. The other is that of the powder metal bearings on the mainshaft getting worn from dirt exposure, but they are also fairly cheap and easy to replace.
My boss was nice enough to give me one out of a junker to experiment with. I have just started on a bike with the Tecumseh 3 horse and the Lawnboy transmission doing its job. I will report back as soon as I am done.
So, stop by your local shop and see what you can find! It doesn't sound like it has been tried before, so we may have come by a gold mine here...
-Brian
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