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09-02-2007 #15-7HEAVEN Guest
Centrifugal clutch on jackshafts?
Hi. i'm involved in a twin-engined project for my next cruiser bike. i need to control both engines independently in starting/accelerating/idling/clutching/shutdown.first, i was gonna use 3 10-tooth sprockets(one-to-one ratio), backed by a 36-tooth rear sprocket. the clutch levers would control engine functions.
now i'm curious about COMET jackshafts with centrifugal clutches. in what little info i could find, it seems to be one to shift gears at speed.
not really what i need it for.
anyone know anything about these centrifugal clutches on jackshafts?
09-03-2007 #2Zomby Builder Guest
CVT on a Jack Shaft
(I Think) Dual engines could work on this setup. Left & right side drive motors? One side CVT & the other more direct chain drive Bigger displacement.....
JAX runs really well, pretty even throughout CVT range. No replacement for displacement... a 4 HP Tanaka could Rock this.
09-03-2007 #35-7HEAVEN Guest
Zomby, both engines drive through the left side 36-tooth sprocket.
actually, i'm having second thoughts about this jackshaft clutch idea. i've searched a lot for more information, but haven't found much. maybe i should stick to the simplest connection, which is one jackshaft and three 10-tooth sprockets. the ratio would remain the same as the chinese engine to rear sprocket. if i want to shift my power range, i can just replace the drivetrain sprocket to 8t, 9t or 11t for 4.5,4.0 or 3.27 gear ratio.
are your pictures of pocket bike engines in tandem? you would think that dual engines would outpower a 4HP TANAKA.
personally, i'm not worried if my twins don't produce much more power than one 80cc engine. they're mainly for eye candy and ear candy...sights and sounds.
Last edited by 5-7HEAVEN; 09-03-2007 at 04:14 AM.
09-12-2007 #45-7HEAVEN Guest
still looking for the correct centrifugal clutch to control my rear drive sprocket. if i can locate that part, i can fabricate a pullstart mechanism like SlicerDicer is working on (or install kickstart assembly on the left-side engine as a last resort). that way, my engines can be individually started and controlled, idle at the stoplight and pull away from a dead stop.the clutch levers can be relocated to the downtube, because they'll just be needed to separate the engines during startup, or when one engine needs to be disconnected from the drive for whatever reason.
i contacted COMET dealer, no response yet.
Last edited by 5-7HEAVEN; 09-12-2007 at 01:05 PM.
09-13-2007 #65-7HEAVEN Guest
nope, nothing i could use there.
i believe what i need will slide onto the shaft towards the middle.they're probably available with a belt pulley. i don't want to use that pulley, because i'd need a SECOND jackshaft to convert to gear sprocket.
maybe the last resort would be a one-direction sprocket, to use as #3 sprocket on the jackshaft.
09-16-2007 #7vintagebiker Guest
I tried to use a centrifugal clutch on a jackshaft.
It didn't work because I had the jackshaft spinning slower than the motor RPM (gear reduction) so the clutch would not hook up, not enough centrifugal force to engage the clutch properly. I even tried weaker springs but had to abandon the idea and put the clutch back on the motor.
I wanted to take the clutch off of the motor and move it to the jackshaft so the motor would be more narrow, not for a twin engines set up.
09-16-2007 #85-7HEAVEN Guest
Bernie, you are so correct!
Jesus H. Christ, Bernie!
you're absolutely correct!
since the engine has a 4.15:1 gear reduction and a centrifugal clutch generally opens at 2000rpm, the engine would have to rev to 8,300rpm to actuate the clutch on the jackshaft!
in other words, the rear wheel sprocket would NEVER ever spin!
THANKS! for your insight. it saved me time, $$ and effort. i was so close to buying two COMET jackshaft clutches on ebay.($100+)
okay, no centrifugal clutch for my twin engine project, but i need to work on my pullstart mechanism instead.
i WAS gonna relocate both clutch levers to the downpost if i could utilize the centrifugal clutches. now they need to stay on the handlebars.
09-17-2007 #9Alaskavan Guest
Hi 5-7. This is off topic and I'll try to keep it short. I've been studying gear ratios, jack shafts, torque converter's etc. I've read a bunch of your posts. I think the germ of an idea is starting to emerge. This may be way cool, but I'm going to let it ferment a bit before sharing. Anyway, thanks for your knowledge.
Aw. To heck with it. I'll post it in general so people can tell me why it won't work.
09-17-2007 #10Old Dude Guest
Newbie, 1st post.
I have been pondering an idea that would ideally allow driving the pedal crank with the motor, and still retain full pedal function with the motor off. One could still use the pedals as a foot rest while motoring. Also allow a geared rear wheel hub to function.
I stumbled across another forum where a forum member made a vague reference to driving thru the crank. It turned out to be a jackshaft arrangement. Looked like it would work but not the solution I was hoping for.
Having a lot less life ahead of me than behind me Ive come to the conclusion that there arn't to many original ideas out there. If you can think of it, odds are someone somewhere already has. So I'm going to share my idea in hopes someone on the forum will have heard of or seen it done....or do it and share with the group.
Basic parts: 3pc crank, main shaft modified are retooled to accept a sprag clutch/bearing on one end and a bearing of the same OD on the other end.
(Because of load torque it may prove necessary to use two sprag's and omit the bearing)
This assembly is inserted in to a hollow outer shaft. Each end of this outer
shaft is fitted with a bearing. This whole assembly is inserted into
the existing bike crank cylinder. (about 2" ID) The "drive sprockets" left motor, and
right wheel, go on the outer hollow shaft and the pedals on the inner crank
shaft. (Where they were originally) It will help to draw this as you visualize it in your mind. Also google "Sprag" clutch if your unfamilar with them.
I have no doubt this scheme will work, but fitting it into the existing crank cylinder might be impossible. Kinda like 10lbs of stuff in a 5lb bag.
A new larger crank cylinder could be fitted to the bike in place of the original.
The rights to this idea (If it is original) belong to this forum and its members, to refine, expand, improve or change for the use and sharing of all on the forum.
Their are some clever guys on this forum, so hash it out guys.
BernieP, the "Old Dude"
Last edited by Old Dude; 09-17-2007 at 10:42 PM.
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