sunofjustice's gearbox idea...continued


Well-Known Member
Local time
2:11 AM
Nov 4, 2006
Pittsburg, Ks.
...........what if you CUT away(dremmel) just th' gearbox part of a happy time(?) china engine......... and weld th' smaller of the two gears in th' trans housing to a jack shaft

very interesting. seems do-able. using the happytime block....less head, jug, piston & connecting rod.
Ideally, the crankshaft would be replaced with a plain shaft, but unless you are a machinest...or have one as a close friend...this would be expen$ive.

Having a manual clutch would open up all kinds of possibilities for donor engines

Mounting to the bike would be simple....and the whole unit is quite compact.

does anyone see a down-side or any problems here? I'm all ears!!!

or should I put this to sleep with the fishes:LOL:

Zomby, excellent thread & info...BTW
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BRILLIANT! Who's going to be the first to attemp this???? I wish I had an old clapped out Happy Time to play with. Looks like a great project!
:cool: The happy time engine's bulk come into mind, as does the location of its mounting bosses.

In essence, it'd be like mounting TWO engines in tandem.

Beside the inexpensive generic jackshafts on the market, there are adjustable "pillow block" supports, pedestal mounts which look like a shaver's safety razor standing upright and others. most need a flat plate welded or secured to the frame as a mounting surface.

Zomby, how about some links to the gearbox suppliers? I'm looking ,but not finding anything on the 'net.

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:cool: The happy time engine's bulk come into mind, as does the location of its mounting bosses.

In essence, it'd be like mounting TWO engines in tandem.

as for bulk...I doubt it weighs more or takes up more room than a store-bought gearbox.
& where/how it will mount seems like a plus. chain alignment to the rear wheel would be perfect.

you mentioned "inexpensive" jackshafts...pillow blocks, etc.
I mentioned "recycling". (jackshafts included....and a manual clutch.)

Now, tell me why this won't work. :cool:
:cool:srdavo, Standing in front of me is my old bike with a very wide cruiser frame. I also have two happy time engines here for measurements/placements. Let me see if i can fit everything into place.

Even though the engines' top halves aren't banging each other, I can't seem to fit BOTH of them in my frame in tandem.:rolleyes:

That IS how you guys were thinking about mounting this 4.1:1 "engine-tuned-gearbox", right?

Even if I removed the engine's top half, this new "gearbox" would be too long for the wide cruiser frame. I tried to turn it in every way possible to facilitate the connection, but no dice. The linked chain would not align with the drive and driven sprockets.

Please clarify, as I am very interested in finding gear reduction and reverse-direction ideas.

Hmm, do you realize that by adding another cog into the arrangement that the engine's drive direction will be reversed?

I cannot appreciate a second clutch in the arrangement. It offers no benefit, therefore might be considered a liability.

Brian, I'm sorry I might be wrong, because somehow I'm not visualizing what you guys are seeing.

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1 happytime bottom end. (gearbox)
1 engine of my choosing. maybe a chainsaw...maybe a weedwhacker?

I am aware of which way engines rotate.

what if....I use a stretched frame?
what if...I build a frame around the gearbox & engine of my choosing?
(would you then tell me there is no Santa Claus?)
what if....we stop carping on Zomby's thread.

sorry Zomby
:cool:That's what I mean, srdavo. In MY daydream, I'm seeing TWO.:confused:

Will someone kindly explain exactly how this "gearbox" links into the drivetrain ?