Nice Jackshaft Idea


New Member
Local time
6:07 PM
Mar 3, 2008
I just came across this on the ZBOX site.
I've been pondering a very similar idea for my bike for a while now. Been thinking about the same jack shaft setup and freewheel
at the front but using an internal 3 speed hub at the back.
This is just be the inspiration I needed!

Pics are good..


I just finished doing the same mod on my bike. Well almost the same. Mine is a little more elegant and will be easy for all to do. I am looking into marketing it as a kit but I will share how to's. I am using a front freewheel with a standard 6 speed cassette on the rear. It is awesome to be able to shift. Will keep everyone posted. I have a few more tweaks to make before I publish.

Large Filipino

That's the thing though. Freewheel cranks are tough to come by. Unless you know of a source.
That's truly a helper engine setup,helping you right at the crank.


I guess I don't get that system. Does it mean if you were under throttle and your feet slipped off the peddles, they would keep spinning on their own?

Large Filipino

The rear wheel would have fixed gears. No more freewheel. The freewheel is in the cranks. So the chain would always be moving. Always. When engine powers the bike the crank can stay still cause it's freewheeling.

...but then again,the rear doesen't HAVE to be fixed....right?
The front DEFINETLY has to be freewheel though.

(edit) rear sprockets have to be fixed so the Happy Time can be bump started
Last edited by a moderator:


Hey all,

Wow....Good find....I would love to be able to find a commercial jack shaft like what that bike has!....I would love to see a video of that bike running....Top end would be insane!....Acceleration should be good too.....Too neat!!

Torques - In that setup it is the front 2 chain rings that can remain freewheeling while your pedals remain stationary.... When we were kids my sister had an old Sears bike set with a front freewheeling system....It looked like a regular 10 speed but could be shifted while coasting (the rear sprockets were not on a freewheel...all the sprockets were was the front chain rings that rotated while coasting with your feet on the pedals.....if you took your feet off the pedals the pedals should remain stationary unless the very slight friction of the front freewheeling pawls caused them to move a little--- which they often would with no weight on the pedals. Hope this is clear enough for you.

Ghost - I am dying for some pics or a video too!!...Technology is definitely moving ahead here!



I think I'm a little on the fence with Torques on this one?


I see this as a helper engine that transfers power to the jack shaft and to the crank, to which the pedals and our feet are attached to. The way I see it, if you pedal and engage the engine and then twist the throttle. You will make the bike go faster and will feel less work for your legs. In fact if you lift your feet off the pedals, the crank will keep spinning under power as long as you keep twisting the throttle and using the power of the engine. It looks like you will have to get used to always pedaling when you engage the engine, unless you pull in the clutch and then be able to coast with the pedals in a stationary (9 o'clock- 3 o'clock) position.

Maybe I'm just not seeing it here and a video would be a great tool to help describe the workings of a system such as this.

In the meantime, here's a link to a Swiss company that has this electric assisted motor that can be engaged anytime you need the extra power for climbing up a steep hill or anything else:

They have a few different versions available, but please check out their "Lanz V4 (Free Ride)" version that looks like it says "Version with a crank-free run for technically demanding terrain". Does this mean you can engage the motor and still not have to pedal? Cuz that would be great for very technical terrain where standing up on the pedals and balancing yourself would be very important and not having to worry about pedaling.

Can anyone else shed some light about this type of system where attaching the motor or engine directly to the crank and then to the rear wheel.