Eliminating the driven sprocket

[Andyinchville1]

HI,

I am dying to try this out!....One thing tho....Will this kit fit on an aluminum frame with over sized tubes?

Thanks!

Andrew

PS - I suppose I could take a ball peen to dimple where the u bolt goes around the seat tube but is there enough clearance for the sprockets on the jack shaft?

 

[Pablo]

What size tube?

I suppose the rear mount bracket could be "adapted" in several creative ways to take a larger u-bolt.

 

[zebratruck]

I stumbles across this 15 page thread and read it all with excitement. Very interesting and a good idea. I have to throw this out there though: anyone looking to do this should have the rear derailleur hanger alignment checked at a bike shop or buy the park tool (Park DAG-1) to do it yourself. Being out a couple millimeters can make a big difference in shifting when putting the leg to it, could get ugly when adding in the torque of the motor. And make sure the low limit screw is adjusted so the derailleur doesn't meet the spokes and lunch the wheel. And don't just put on a new chain, have the chain checked for stretch with the propper checker (Park CC-2) or just put a whole new drivetrain on. New tolerance chain on old cogs means skipping and trouble. Not as bad on older mountain bikes with 6 or 7 cogs in the rear but an 8 or 9 should definitely be checked.
And did I read those last few posts right, you will be able to lean a bike over, clutch lever out, and use the crank arm like a kick starter?

 

[Pablo]

Indeed. Bike needs to be tuned. If your dérailleur is marginal, have it adjusted. If your low limit is off, I think you would know it before installing a jackshaft, but yes check that and the high limit.

Yes. But with engine cold, it's a bit easier to do it with bike upright so you can get your legs into it.

 

[zebratruck]

Ok, I just meant leaned over enough so the rear wheel was barely off the ground.

 

[zebratruck]

Pablo, where can i see a larger pic of the bike in your avitar? Looks cool but I can't squint that much anymore

 

[Ghost0]

Here is the rendering of the photo that Pablo uses. It is what is theoretically possible with the jackshaft kit. I also included a picture of the bike I started with.

 

[Jemma Hawtrey]

Hi,

Ok, I will try and explain this so it makes sense...

What I have at the moment is a GEBE belt drive 32cc 2S

What I want to do is get a hold of one of these jackshafts with one side configured with a GEBE gear so I can run a short belt to the jackshaft and then use the hub gears for a geared transmission - 7 speeds.

What I need to know is what is the dimension of the jackshaft and also can I set it up without using that idler chain as shown in the pictures - ie have the standard chain lengthened so it would go chainring/jackshaft/hub and back.

This would get me the best of both worlds and be the cheapest solution all in all...

comments and suggestions welcome

Jemma xx

 

[Pablo]

Hi,

Ok, I will try and explain this so it makes sense...

What I have at the moment is a GEBE belt drive 32cc 2S

What I want to do is get a hold of one of these jackshafts with one side configured with a GEBE gear so I can run a short belt to the jackshaft and then use the hub gears for a geared transmission - 7 speeds.

What I need to know is what is the dimension of the jackshaft and also can I set it up without using that idler chain as shown in the pictures - ie have the standard chain lengthened so it would go chainring/jackshaft/hub and back.

This would get me the best of both worlds and be the cheapest solution all in all...

comments and suggestions welcome

Jemma xx

The shaft itself is 5/8" - but the hassle in your set-up may be mounting the assembly. Also - I assume with what you describe your pedals would turn when under engine power [?]

 

[Jemma Hawtrey]

I would need a freewheel crank of some description but my local bike shop reckons they dont exist!

Mine is a one piece schwinn cruiser type so would I need to replace that in order to use the jackshaft with the usual method of drive..?

Also why would there be problems fitting it - I assume its just two clamps to the frame?

On the upside - it looks like the belt would fit pretty much perfectly as regards a run from the gebe mount to the input side of the shaft

now I just need money.

The reason for this is to make the bike more flexible but still keep the reliability of the GEBE kit while adding gears - better hill climbing and possibly much better speed with the same power output.

Jemma xx

 

[spad4me]

Hi,

Ok, I will try and explain this so it makes sense...

What I have at the moment is a GEBE belt drive 32cc 2S

What I want to do is get a hold of one of these jackshafts with one side configured with a GEBE gear so I can run a short belt to the jackshaft and then use the hub gears for a geared transmission - 7 speeds.

What I need to know is what is the dimension of the jackshaft and also can I set it up without using that idler chain as shown in the pictures - ie have the standard chain lengthened so it would go chainring/jackshaft/hub and back.

This would get me the best of both worlds and be the cheapest solution all in all...

comments and suggestions welcome

Jemma xx

Get rid of the belt totally go from your rackmount engine to the kits jackshaft with a chain then just like the stock kit.
You have a centrifugal clutch right.
You would then have a one sweeet ride.
From a stop in first gear just advance the throttle and shift as needed.


I must state that after some thought you may not be able to use this kit.
You need to ask Ghost0 about the rpm range for the kits jackshaft input.
As a happy time engine has a large reduction of rpm in its built in jackshaft.
From the clutch to the small sprocket.
It would be a very nice motorized bicycle though.

 

[Jemma Hawtrey]

Thinking about it that would be the most sensible and cheapest way to go - although I might need to change my crankset because its a one piece schwinn and I am not sure that it will work with the freewheel sprocket..

So far as I understand - correct me if I am wrong - but the chengines reduction is merely that of the 10 tooth on the end of the layshaft from the manual clutch as fitted. Therefore as the chengines are direct drive up to the clutch point the reduction is 1:10 at the engine output which would equal a max of maybe 870rpm.

This means I should be able to fit a 10-tooth sprocket to the output of the GEBE's clutch shaft and get equal reduction (again a D/D clutch) and be able to have a suitable ratio with the jackshaft input/output.

So - I need to know the following...

Is there a source of a screw threaded sprocket with 10 teeth that will fit in replacement of the gebe gear?
Will the jackshaft mounting fit a normal schwinn cruiser frame?
Will I need a new crank etc (working with the idea of a chain from jackshaft to crank) as my crank seems to have a stud on the pedal arm?
If I have the same reduction at the motor end as on a chengine - aka 10 teeth - and no reduction on the jackshaft itself.. what is the reduction from the jackshaft to the freewheel sprocket on the crank itself - ie how many teeth does the engine drive sprocket on the crank have?
Given that i am using a Shimano Nexus 7 speed hub... will this actually be any faster than the usual GEBE?

Jemma xx




Jemma xx

 

[Pablo]

I would need a freewheel crank of some description but my local bike shop reckons they dont exist!

Mine is a one piece schwinn cruiser type so would I need to replace that in order to use the jackshaft with the usual method of drive..?

Also why would there be problems fitting it - I assume its just two clamps to the frame?

On the upside - it looks like the belt would fit pretty much perfectly as regards a run from the gebe mount to the input side of the shaft

now I just need money.

The reason for this is to make the bike more flexible but still keep the reliability of the GEBE kit while adding gears - better hill climbing and possibly much better speed with the same power output.

Jemma xx

I assure you crank freewheels exist. I'm fairly certain the crank will fit, even if you have to go to the crank adapter.

The current kit only bolts to the China 49-67cc engine itself. Look closely at the pictures.

IMHO this will be your largest technical hurdle.

Maybe I missed it in your earlier posts - how many speed is your cruiser?

 

[Pablo]

Get rid of the belt totally go from your rackmount engine to the kits jackshaft with a chain then just like the stock kit.
You have a centrifugal clutch right.
You would then have a one sweeet ride.
From a stop in first gear just advance the throttle and shift as needed.


I must state that after some thought you may not be able to use this kit.
You need to ask Ghost0 about the rpm range for the kits jackshaft input.
As a happy time engine has a large reduction of rpm in its built in jackshaft.
From the clutch to the small sprocket.
It would be a very nice motorized bicycle though.

Main problem as stated, is mounting the jackshaft. We have not designed a stand alone kit yet. We have thought about it, but have our hands full right now. Indeed current gearing is set for Chinagirl engine - however it could be stepped up to RPM match other engines - of course there will be size limitations all depending on how it's mounted - I think something like a 36T-44T (? doubt they make much larger for a 5/8" shaft) on the shaft input side an 8T on the output side.......man this will need to be checked out....and then finally a cover designed.....yikes.....

 

[jg767]

hook that up with a denuvi hub,you might really have something!

 

[Pablo]

Yep, no doubt about it.

 

[Bikeguy Joe]

You mean a NuVinci hub?

 

[Pablo]

You mean a NuVinci hub?

Actually I think he meant:DENUVI 7

 

[Pablo]

OK OK Just kidding

YouTube - NuVinci Bicycle CVT

 

[Goat Herder]

This is what I have been tring to do. awsome! I whant one of these kits as soon as they are availible. However I had one major concern, I did alot of peddling over the years One of my biggest mods on all of my pedal bikes was having everthing even whith my body. Is the free wheel crank design capible of allowing crankarms and pedals to be perfectly square with the bike so not to be favering one leg over the other? Also have you checked with phil wood bottom brackets they might help a hurdle they helped alot on some of my custums.