Dual engine for 2 speed action?

[tomdowns]

I've had this idea for awhile now but never knew if it would work or not. I love the idea of having a general gear (for 0-30mph) and then having an overdrive gear to pull you to 45mph. Would it be possible to mount two engines side by side and have both of them connected to the axle with different gears? The first gear would be pull start and the overdrive would have electric start so I only have to turn it on when I need the gear. Crazy?

 

[itsid]

Wouldn't the "overdrive" motor statup as soon as you roll, and would it rev up too high to stand the rpm?

Or do you want to add an electric clutch or something?

'sid

 

[ML-TOYS]

Not sure where it is but this was discussed a month or so ago. Try searching for it

 

[tomdowns]

I tried, searched "dual engine"
Not sure where either...

 

[Oxymoron]

Or you could build one of these.

There's another thread where the guy uses two centrifugal clutches and a gear that "freewheels" on the primary to form a two speed automatic transmission. I think it was on a mini bike. A quick search didn't turn anything up, but I'm sure if you dig, you'll find it.

 

[ML-TOYS]

http://www.diygokarts.com/vb/showthread.php?t=22069&highlight=speed

 

[tomdowns]

Thanks ML, I was looking for that. The guy hasn't posted his results yet though. After reading all that it makes me think getting a 11hp with a good gear ratio will pull you to the speed I'm talking about with enough torque to still make it fun.

 

[Oxymoron]

Here's a pretty cool automatic 3-speed setup... just not sure if he ever finished it.

http://www.diygokarts.com/vb/showthread.php?p=50326

Edit: I was just thinking... wonder if I could adapt a coaster brake from a bicycle to a jackshaft, with a secondary gear on it? Then hook up a linkage to a foot pedal or hand lever that locks in place. Whenever you want second gear, push the pedal... when your done, let go. Back in first. Hmm.... me thinks I will attempt this

 

[mckutzy]

Those spragg clutches on bicycles typically wont handle the torque of the motor on it.

I think that mult cen clutch with varying engagement profiles would be a good Idea, but (but with buddies idea) finding the spragg clutch with the right amount of teeth for the shaft dia. might be the expensive part.

 

[Oxymoron]

Those spragg clutches on bicycles typically wont handle the torque of the motor on it.

I thought that too, but the load would be significantly decreased in 2nd gear, since it would already be rotating the shaft very quickly. I wouldn't ever put it in 2nd until 1st was topped out.

Maybe I'll just do a test to find out how fast I can destroy it, lol

I'll be the crash test dummy

Okay... sorry OP, my inadvertent thread jack is over

 

[chris_the_poser]

If I were to do it I would have both motors running the whole time the second gear motor would just idle till I hit the peddle for it. In theory it should work. I wish that other guy would finish his and post the results of it.

 

[mckutzy]

Thats a good Idea with the two engines.
When I pictured this two motor setup I think with a two lever on the steering wheel for the motors, one at least for the second speed motor.

On the other hand another thought is, a setup like multi-carb linkages for hot rods and racing cars. AFAIK.. They have an "idle" carb(s), then a full out power carb(s).

 

[firemanjim]

I like the idea of 2 engines too. Much like mckutzy, I would do main motor on the right foot, and the high speed geared motor on steering wheel with a thumb throttle from an atv..... If I had another good running motor laying around I'd try it out on my daughter's kart. In theory,it HAS to work. You would need a way to lock out the foot throttle to keep from "wanting"to accidentally hitting that gas too. It would definitely destroy one or both clutches. .... maybe even a motor or both...

 

[mckutzy]

I reckon you would need something like a dual pull(push/pull) throttle kinda setup. Use the one cable to the throttle, the other to an interrupter pin in the pedal linkage.

 

[itsid]

wouldn't it be more fun to just set up both engines in parallel using a lower gear ratio and use both all the way?
Just like on ordinary two engine karts...
You have TWICE the torque, so you can lower the ratio and have both enough torque to get going and a higher top speed.

That'd be much easier to set up.

'sid

 

[chris_the_poser]

It would be easier but wheres the fun in easier

 

[itsid]

you're right, didn't think of that ...
my fault.



Okay then, how about this:
Think of a differential, the std mower ones
which is set up in a 3sprocket jackshaft configuration.
Each axle carries a different size sprocket for one of the motors.
The center-Sprocket (the one that's attached to the differential box)
is then direct linked to the axle sprocket.

One motor has a centrifugal clutch the other one direct drive;
both motors are running.

Now the clutch one is the "main motor",
the other one will be our "kicker motor".

• Case1: both motors idle
  The diff-axle of our main motor is spinning backwards, taking the load our kicker puts to the other side, differential will remain still: kart is not moving
  
• Case2: main motor engaged
  The diff-axle of the mainmotor is spinning forward, the other side is prevented from spinning backwards by the kicker motor.
  The differential case will turn and the kart starts to roll up to a point where the difference between the rpm of our main and the rpm of our kicker will prevent further acceleration
  
• Case3: main motor highest rpm, kicker revving up
  More torque is send through the differential-jackshaft to our axle, making the kart faster until both motors are at their highest possible rpm up to a point where the kicker diff-sprocket has a higher rpm then the main diff-sprocket (due to the different sizes)
  And we have "overdrive" of some sort.

Oh and no, I wont even try to figure what gear ratios will be need to make it useful.
But in theory this might work.
And counting a diff as ONE we have a low part count

that's better chris?

'sid