jackshaft crankcase

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im stumped...
can you post a pic of what you mean? :D
 
Jackshaft is more of a slang term for a countershaft. What he wants to do is to replace the crank with a spindle that supports two chainrings that will synchronize the engine to the rear wheel.
 
In my line of work, the term "jackshaft" is often used to mean an intermediate shaft. Something that might be used to connect, say, a differential to an axle shaft. You see this a lot on FWD cars that have equal length CV joint shafts. Still not entirely clear how this relates to a bike. I do (now) have the impression that this relates to a motorized bike, which is not information that the original poster included in his posts.
 
I have seen jackshafts used on long, stretch bicycles. The chain is generally tighter and doesn't fall off as much when the jackshaft is used. Other than that, I have only seen them on bikes with engines or electric motors. Sickbikeparts,com sells jackshaft kits, but they are intended for use with China girl motors.
 
nawl that aint going to work, I gotta a big boy hood motor, my question is how do you put a jackshaft in a bottom bracket
 
can any one please tell me how to put a jackshaft in a bottom bracket, like Cleatus_Fathom's bike
 
jj256 said:
nawl that aint going to work, I gotta a big boy hood motor, my question is how do you put a jackshaft in a bottom bracket
Click to expand...
You have to install a free wheel bearing on your pedal chain ring so you can use the shaft as a jack shaft also. Hope that helps you somewhat.
 
I honestly have no idea what you guys are talking about, BUT, apparently somewhere in this thread on motorbicycling.com there's some info on how to do a jackshaft/pedal combo. I did a search for Cleatus_Fathom because I was dying to know what the heck a jackshaft was, and in one of his threads someone posted this for him:

http://motorbicycling.com/showthread.php?t=28747

Hope it helps.
 
cave12man said:
I honestly have no idea what you guys are talking about, BUT, apparently somewhere in this thread on motorbicycling.com there's some info on how to do a jackshaft/pedal combo. I did a search for Cleatus_Fathom because I was dying to know what the heck a jackshaft was, and in one of his threads someone posted this for him:

http://motorbicycling.com/showthread.php?t=28747

Hope it helps.
Click to expand...
Here is where it shows how it was done.

http://motorbicycling.com/showpost.php?p=311592&postcount=26
http://motorbicycling.com/showpost.php?p=315020&postcount=35
 
OK his drawing shows how it works---the jack-shaft is hollow for the pedal spindel to go through.Seems it would be a lot simpler to have put a bearing on the motor-sprockets and pushed it onto the crank spindel.
 
Got a another question I was looking at the jackshaft kits on mfg supply, and I was looking at the bearings and bearing hangers. So can I take a regular sealed bearing, a heavy duty washer, and some snap rings and build my jackshaft. Will the snap rings keep the bearings in place?
 
I.just came up with a idea. What if I were to take a old bike hub put some sealed bearings in it.and use a grade 8 bolt for the shaft.
 
jj256 said:
I.just came up with a idea. What if I were to take a old bike hub put some sealed bearings in it.and use a grade 8 bolt for the shaft.
Click to expand...
A keyed shaft doesn't cost much and it is made for what you want to do more than a bolt. Bolts are made for pressure put on them in a pulling direction not a twisting direction.

IE: When a bolt is tightened down the bolt gets stretched a little length wise. This is where they have their strength.
 

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