Twin Bike Sports Runabout
 

Engines synchronized by common distributor

Bikes already suck vs cars re payload moved/gallon. This twice as bad.

This is just for fun!

Until you turn. :rolleyes:

Yes, some method of de-clutching the inside wheel activated by the steering, perhaps electrical clutches on the rear wheels.;)

Yes, but 90 deg out of phase with each other so that there are four single power pulses each revolution, rather than two double power pulses. This can be achieved through the use of an eight cylinder distributor shared by both engines.

The closest to that I've seen were projects for wheelchair-accessible trikes, but those resorted to scooters instead of traditional motorcycles. But I'm not sure what had been done to keep the engines synchronized.

Maybe, the easiest system would be to place the two engines behind the rider, and join them physically, 90 degrees apart, with a double sprocket idler shaft, and drive a single rear wheel, making it a twin engine trike. Slightly lighter, easier to turn, and easier to license. The reason for connecting the engines 90 degrees out of phase is to have 4 instead of 2 power pulses per revolution. Smoother, and sounds better.
(Something like this:)

Let 'em be "unsynchronized"- twin engine aircraft make no attempt to phase crankshafts; matching rpm is sufficient.

Twin engine aircraft don't drive a single wheel, and drive, instead, a fluid. In addition, to provide for rpm differential to aid in turns, the two aircraft engines have to be able to operate separately. Again, twin engines provide limp home capability. On the other hand, I believe some twin engine aircraft DO mechanically join the two props, so that one engine can turn both, if the other goes out.
I don't want the engines to phase in and out with each other. Those vibrations would be far less pleasing than eight evenly spaced firings.

This makes for much less headaches.

Car and Driver featured a twin-engine CR-X over thirty years back. To get it to work properly, they simply linked both engines to the same gas pedal and let the automatic transmissions match speeds through the road.

That car did 0-60 in 6.2 seconds using two 1.8 liter engines mated to four-speed automatics. Pretty nuts.

Yes, but the torque converters smoothed out the differences. Manual transmissions don't have that buffer. I remember that article. It was a 1984 Gen 1 CRX with the rear axle replaced by a second engine/transaxle, with the steering locked on the rear engine. The two engines came from Accords.

I wasn't refering to a reverse-trike. Well, I'd like to see how the CVT in each scooter motor could provide some compensation analogue to the differential effect, or if it would need some other way to do that.


It's not viable to couple both propellers to only one engine in a twin-engined aircraft. However, at least in the Piaggio P180 Avanti the propellers are so close to each other that it may lead to an impression that both propellers could move during single-engine operation.

Maybe I was wrong on that.

Why not two big engined scooters instead of two manual bikes?
Seems like you are trying to do things as difficult as possible. (not judging, everyone can do what they want as a hobby :thumbup:)

Do you have two bikes somewhere or are you going to purchase them? I'm interested in seeing how this turns out.

I would think you could freewheel each wheel, and let the outside wheel coast around the corner. I wouldn't do that on a four wheel motorcycle because at higher speeds, I'd want engine breaking. A trike solves that.

No, this is just a mind exercise. My ideas are far larger than my bank account. (DAMMIT!)

You don't want engine breaking cuz then you're down to one boring old engine.

Siamese two V-Max' and you won't have to worry about differential action.

No, I didn't mean "break an engine" I meant leaving the engines engaged and down shifting to let them drag the trike down from speed.:p

Oooooh, braking! Why didn't you say so?

Uh! yeah, I spelt it wrong.:o

Without a direct mechanical coupling the second engine using spark timing from the primary engine would rarely, if ever, run.

I know! Use a multi-cylinder engine!

I believe you are right. I moved both engines behind the driver, placed an idler shaft behind them, and put a sprocket on the shaft for each to drive. Then added a third sprocket to run the final drive chain to a single rear wheel.(Yes, it's now a reverse trike - see permalink 8 in this thread). The Idler should provide the direct mechanical coupling you speak of.

I envision four pedals, two right for throttle and brakes, and two left, one for the clutches and up shift, and the other for clutches and down shift. Hands free for the steering wheel (legal on motorcycle trikes in Texas).

There were some twin-engined GM Coach buses which resorted to a pair of Detroit Diesel 4-71 engines before the release of the 8V-71. IIRC it resorted to a special gearbox that took the output from both engines and sent it to the transmission through a single output shaft.

Yes, like my two chains driving one intermediate shaft. Not sure if I can keep them in perfect sync, with chains wearing, but gears are too difficult.

Here's the idea on the Clutch/Shifter pedals:

Actually, since I'm using solenoids and switches, I may as well just use one pedal with both up- and down- shift switches on the pedal

There is the possibility that one engine might shift, and the other might not complete it's shift. This could be very bad, unless motorcycle engine/transmissions are used that have gear indication lights on the instrument pods. The clutches could be equipped with servo lock outs that would hold the clutches disengaged unless both indicator lights match.
In the case of a missed shift on one one of the engines, the trike would coast until the pilot could manually correct the mismatch.

It's becoming too complicated. Maybe if you could set both engines to deliver their output to a single shaft, eventually resorting to clutches to disengage one of them in case of failure, it's going to be the safest way to deal with them.

There was a TV show that featured a twin-engined dune buggy fitted with 2 Royal Enfield engines, maybe you should watch it on YouTube to seek for inspiration.

You have just described my diagram in message 8, as further described in message 30. I would keep both engines disengaged in a mis shift (verified by the shift position lights) because of the "solid" connection of the intermediate shaft. otherwise, if I wanted one engine to run without the other, I would have to add clutches at the intermediate shaft. It's simpler to use the clutches inside the transmissions. If I thought one transmission could handle the outputs of both engines, I would find some way to tie the two crankshafts before the transmission, but using both transmissions with safety clutch lockouts is simpler. I'm sure the dune buggy you mention was equipped with two inputs to one transmission, and I'm sure the two engines were not synchronized with each other, but I want to keep mine smoothly sync'ed 90 degrees out of phase to avoid the kind of thump-thump, thump-thump Harleys have.

I actually don't remember, I just remember one of the clutches failed.

Did it fail to engage, or to disengage?

Actually it blew away for some reason that I don't know, but it might have been due to overheating (it was riding through a desert).