This idea occurred to me this morning as I mentally rebuilt the recumbent tadpole in my mind in the shower this morning. Some homebuilt recumbents use the bottom crank to help route the chain from the boom crank. I was thinking of leaving the bottom crank and derailer intact and use it as a jack shaft shift kit, on a 18/21 speed chain ring that would give you three speeds. on the left side of the crank use a fixed gear to go to the engine, then but a freewheel gear on the end that would go to the boom crank. the only thing you would have to do different is turn your boom crank over so the chain rim is on the left. Just an idea for all you bent builders out there.
Jack shaft shift Idea for DIY Bents
- Thread starter ferball
- Start date
A good idea in many ways ferball, the only problem I can think of is mounting up another sprocket as most three piece cranksets have a square tapered shaft for the pedal arm... and I dunno if a sprocket for a tapered square shaft is readily available. SBP's shift kit relies on something similar - but their freewheel still mounts to the pedal arm (threaded) & the pedal arm mounts to the shaft...
However it's still a workable idea even if a square shaft sprocket isn't available, while not all bottom brackets are the same ofc - I noticed that if I simply dremeled the threads on mine down flush, the 1 3/8" OD sealed bearings fit perfectly & best yet, two sealed bearings & a chunk of 5/8" keyed shaft are only 'bout $10 or so;
Jackshaft Bearing 5/8" ID x 1 3/8" OD
5/8" Keyed shaft
However it's still a workable idea even if a square shaft sprocket isn't available, while not all bottom brackets are the same ofc - I noticed that if I simply dremeled the threads on mine down flush, the 1 3/8" OD sealed bearings fit perfectly & best yet, two sealed bearings & a chunk of 5/8" keyed shaft are only 'bout $10 or so;
Jackshaft Bearing 5/8" ID x 1 3/8" OD
5/8" Keyed shaft
Attachments
Just yesterday I posted my entire parts list for a jackshaft that I am going to install in a bottom bracket for my utility bike build. Total cost including the sprockets was $40 from OMB warehouse. The parts list is on page 3 or 4 of this thread:
http://motorbicycling.com/f36/hf-79cc-utility-bike-25584.html
http://motorbicycling.com/f36/hf-79cc-utility-bike-25584.html
Has anyone ever tried a Varydrive pully like they have on a garden tractor? Its a double pully were the center web moves back and forth. So nwhen you move it one belt drops and the other rises and changes ratio. A garden tractor has 6 or 7 speeds so there is quite a range. The only thing they are kinda big about 6 inches around. If someone could make a smaller one just for bikes I think it would be a real simple kit.....Curt
I'm not sure about your budget, but you can get the zoombicycles jackshaft for $ 100 off ebay and they finally have the right instructions up!
Yep You could use a centrifugel belt drive clutch, or even a tightner, and belt drive the rear with the Verydrive in between. The lawn tractor ones use a B belt(5/8") If one were to make it smaller,you could use a smaller A belt (1/2") Just move the verydrive back and forth to change speeds.........Curt
they make them for bikes and go-karts, snowmobiles, golf-karts, atvs, some 6-wheeled amphibians have a cvt, even cars. you dont shift them though, they move themselves according to speed and torque. you wont find them on garden tractors either. in ALL garden tractors, the transmission is built into the rear and is gear (or hydraulically) driven....all tractors are tensioner belt drive setups, the tension of the belt is the clutch. a CVT is different, the driver, or pulley thats put on the crankshaft, is its own automatic clutch, and engages at the rpm that it's springs are tensioned for.it engages by gripping each side of the v-belt, and depending on speed, moves in and out, along with the rear pulley, to change the gear ratio.going from small on the driver (crank pulley) to large diameter on the driven pulley when starting from a dead stop, to the opposite for speed.and yeah you can start from a dead stop,no bogging, and probably wheelie to. "comet clutches" "torq-a-verter"......."C ontinuously V ariable T ransmission" CVT. worship them, instead of running those shift kits....don't they eat up pawls?a question for someone who's put more then 50 miles on a shift kit.....i was replacing pawls regularly, but they were pawls inside a sturmey archer 3-speed. PS....the idea trike has a lawn tractor trans
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NOT THE SAME.
Variable speed changer is differant. It is a double pully with a center web that move frome side to side, and is mounted on a pivet. So when moved back and forth one belt climes and the other falls changing speed. I think it is only found in garden tractors. I will try and post pictures as soon as I figure out how to down size them......Curt
Variable speed changer is differant. It is a double pully with a center web that move frome side to side, and is mounted on a pivet. So when moved back and forth one belt climes and the other falls changing speed. I think it is only found in garden tractors. I will try and post pictures as soon as I figure out how to down size them......Curt
use the "paint" feature to downsize them. drag the image to paint, hit "stretch/skew", put in 25 for width and height instead of 100, then "save as". i live in junkyards. my property is a junkyard. and i have worked on alot of crap with engines, its my life. and i have never seen such a thing...a "very-drive"...you have one to take a picture of?
This is off a 110 John deer. Heavy machined all steel. and there is others made that are stamped steel that are lighter. 6 inches in diamitor. Like I said it would be realy simple if they were smaller and more compact. The bearings are in the center of the pully on the shaft that is on the side arm....Curt
I actucually have three and a couple more coming. The transmison on these have just forward and reverse. I get them all from scrap tractors. They would also work good if you wanted to make a self propeled wheel barow or that type of thinng. They have been out for a few years. You have to watch the quality some are thin stamped steel and some are heavier........Curt
wow....i cant believe i've never seen one. mmm...to the scrap yard then. i could keep asking you stupid questions on it, or i can go get one and poke at it.im gonna go read about it on google. tomorrow i'll go on the hunt.
Ask away, or if you can't find one I can take some shot of a compleate one.
you shift by belt tension? tighter on the front engine-driven belt=faster?then slacked is neutral. its also it's own jackshaft when mounted? so far it looks like the most amazing/simple/economical thing ever. really i've been speechless for the past couple hours reading about these things.
here im thinking back forth meant the disk in the middle of it. the whole unit moves parallel with the belts. duh. well that just makes this thing even more appealing and simpler. have you presented this idea before? i mean who sells a kit that ain't one speed, or that isn't bootleggedly rubed through one of those front freewheel sprockets then back to a normal cassette with normal bike pawls. i would think engines, especially those gear-reducted chinese 2 strokes would destroy pawls pretty quickly. but these vari-drives would take anything you dish out, and give you awesome reliability. im starting to actually shun the comet clutch in the light of these things. these were probably even the predecessors of normal cvts.
I have talked about it but nobody seemed intrested. I will take a picture of a compleat one and post. I think like you hard to understand untill you see the consept. Also I think one would have to do a reduction (kind of like the 4G-t has on the new motors to get the right reduction ), then put the speed changer in between. If it were made to gurbbe size componuts it could fit. But if you were to run a small briggs and belt drive the rear wheel might not need a reduction. The lawn tractors have about a 4 inch pully on the engines. That could be reduced to smaller,take some planning,but so simple.........Curt
haha.nobody seems that interested in comets either, even though they sell bolt on kits that cost almost half as much as the bolt-on ezmotor kit (without motor)that only has one speed and a max-torque. i think you should do a thread devoted to varidrives and cvt systems in the DIY, i've gone thru some pages and don't remember coming across anything on them. scratch that....keep the idea for yourself. scratch that to...not many have the gumption to take on the endeavor of building this drive system from scratch.i would but i need to finish that trike.
NEET TIMES in the DIY has a CVT post. and also mororedbikes.com in th cvt full suspesion post Give a lot on CVT's But not the very drive. I know I will be building one later after I get some other things out of the way first. I been thinking if you use a A belt insted of B it could go down in farther and give a little more speed range
