Some help needed.

[32motleycrue]

I picked up a 4hp Robin 2 Stroke Engine. Its made for a cement mixer so its got the 6:1 Gear box on it.

How would I go about running it since now the axle spins 6 times slower than before?

This is what I thought and I want to know if it works.

Putting a 40t sprocket on the axle, running it to a 10t jackshaft, then back to a 40t rear wheel.
In my head this works, but i'm a better frame builder than engine guy.


Also, I would have to post a picture for this, but when I took the engine apart to clean it up I took off the throttle bit w/ governor and now im not that sure how it goes back on. If there are any diagrams out there, that would be sweet.

 

[gone_fishin]

that's a pretty neat double-tensioner idea...i moved this into "wild in the streets" because, well, it's wild

i'm not much help with gearing, but you may count on a crazy or two coming along and helping out
__________________
"....Get a bicycle. You will not regret it. If you live." - Mark Twain

 

[32motleycrue]

Here is the bike its going on. No pedals. How would I go about making it just idle and not take off once I start the engine?
The motor has the internal gear w/ clutch I think, but I know poop about motors.

 

[mickey]

If you're going from 40 x 10 x 40, isn't that the same as 40 x 40? or 10 x 10? You'll just end up with 6:1 reduction. Is the jackstaff just to move power to the other side?

 

[gone_fishin]

we need pics (or links) of the engine, too, before we can get to work

i believe the jackshaft also serves to offset the power around the engine and back into center for transfer to the rear wheel.

 

[32motleycrue]

I'll put up pictures later tonight of the engine. Im at work all day so i'll just surf this site and look at cool bikes for now.

 

[Ghost0]

The way your picture shows it would be 1:1. You are going 1:4 then back to 4:1 making it 1:1, effectively no change in ratio.

If your engine has a clutch on it already you shouldn't have a problem with it sitting and idling after start up.

 

[32motleycrue]

Well currently its 6:1, how would I go about adjusting it so I can power the rear wheel and go about 40mph max? (20" rear)

 

[5-7HEAVEN]

I'm a "crazy", and proud OF it.

Tell me at what rpm your maximum hp and torque is realized. Then I can predict which gears you need to reach 40mph.

Myron

 

[Bean Oil]

Tell me at what rpm your maximum hp and torque is realized.

^ MyRHONE (Myron) is the man... LOL... although if the op may not have those torque/rpm specs they might be published somewhere.

I used to do gear-inch charts for friends when I rode mountain bikes, but I've forgotten all that stuff now. *sigh* With 7-speed clusters and three chainwheels there was a lot of cross-shifting involved if one wanted the very next possible ratio up or down... but I digress.

Carry on. ~