In Spain in 1987/8 their were two Seat Ibiza two-engined cars that actually raced in Spain.
There are lots of examples of transmissions with multiple power inputs. Twin-engine helicopters are a standard example. The monster tractor pull guys have rigs with 6 or even 8 mongo 1000+ hp dragster V-8s all coupled into a single transmission to drive the two massive rear tires. (tractor pull multiple engines - Google Search)
The funky two totally separate driveline cars we’ve been talking about in effect have the two crankshafts coupled together as well. But via a real Rube Goldberg arrangement. It goes like this: Crank1 -> clutch 1 -> transmission 1 -> tires 1 -> ground -> tires 2 -> transmission 2 -> clutch 2 -> crankshaft 2.
Sophisticated engine control systems generally measure torque applied at the engine to transmission interface and trim the throttle / fuel control on each engine to equalize their power output. So the operator sets a gross power setting that applies to all engines and then the torque monitor fine tunes the engines individually to match their outputs.
On our push-me-pull-you VW we could put torque sensors between each crankshaft and clutch & use that to trim the throttles just like the big boys do.
This is what I’m not getting. If you had a two engine vehicle where both drive trains are manual gearbox and clutch transmissions they are not going to slip between the tires and engine, but only between the tires and road. Consequently when engaged but not at the same RPM the two sets of wheels are constantly going to be in conflict with each other between one driving and the other being driven. And when driving on pavement on normal roads & speeds (i.e. not racing) tires do not slip easily. It would be like constantly driving around a corner without a differential, the tires would resist slipping and the drive trains would be constantly binding between turning and being turned.
Engines are not engaged at any particular RPM. The powers of the two engines might be different, but the RPMs will be the same.
This would be relevant if you had one engine on the left and one engine on the right. In that case, the car would veer in the direction of the weaker engine. But we’re not talking about a left-right split, but a front-rear one.
I know this has been done to death by now but please entertain me.
If the front wheels are turning at an RPM that results in a 60 MPH speed, and the rear wheels are being turned at a 40 MPH speed, then the front engine will be providing all the drive power since the rear wheels will just be dragged along and pulling the ineffective rear engine with it, no? In other words, the rear engine is a hindrance and contributing nothing at this point. Is this true, or not?
Maybe this will help.
You can turn an engine through the wheels and transmission EVEN if it’s OFF if something else (the other motor say) is moving the car.
Thats the WORST case scenario.
Everything else (like both engines running) is just slight imbalances in how much each engine (assuming same size, gearing, and general details) varies a bit, which has been explained many times just works itself out naturally.
That’s exactly what I’m saying. The rear engine may as well be off since it’s contributing nothing to the drive train. All the rear wheels are doing is spinning the transmission and engine.
Whats going to be harder to “turn over”?
An engine that is OFF or an an engine that is running and seeking by the wonder of motor physics to find a balance between the power it puts out and the power required of it?
I don’t know the answer to this.
It just occurred to me.
You can think of each CYLINDER of an engine as its own engine. And that works okay obviously.
The fact they are linked together by a crankshaft rather than transmission-tires-road-tires-transmission like the two engine vehicle is only a minor difference.
But if you’re dragging the engine isn’t valve timing and everything else going to be off? Aren’t you dragging a sputtering, backfiring mis-timed engine?
Yeah, ok, I can dig that. But it wouldn’t be appropriate in any kind of modern, normal, day to day driving vehicle. At least its benefits wouldn’t outweigh its complications.
Seriously?
Please tell me you are kidding.
Well, I can guess, but this thread is still in GQ. So I have no conclusive answer: that’s all.
As long as all the wheels are on the ground, this won’t happen. You can have front wheels supplying 60 HP and rear wheels supplying 40 HP… but in that case, that just means that the front wheels are providing 60% of the total power, and the rear wheels are providing 40% of the total power. The rear engine in this case is not deadheading; it’s increasing the total power by 66% above what it would be with just the front engine.
There was a guy in the 1950s that put twin engines in everything . Faegol bus company but he made trucks and race cars as well.
If 1950s engineering can make it work then it’s probably not that complicated and doesn’t need fancy computer control to synchronize engines.
No, because the engines are not stepper motors or anything else that has a fixed RPM output for a given input.
Think of these cases:
The car is driven in 3rd gear on flat ground and the accelerator pedal is depressed to exactly one third of its travel, then clamped in place by some gadget. The car will accelerate to a certain speed and stay there.
A 1% upward gradient is encountered (the gear selection is unchanged and the pedal remains clamped). The car will slow down and settle at a slower speed than on flat ground.
A 1% downward gradient is encountered (gear and pedal still set the same). The car will speed up and settle at a higher speed than on flat ground.
Cthulu rises and lifts the car completely off the ground (the gear selection and position of the accelerator pedal remain fixed, as the driver is eaten first). Without the load of pulling the car along, the engine will revv dramatically and the driven wheels will spin quite a lot faster than they did in any of the previous phases of the experiment.
Cthulu extends a tentacle and grasps the spinning wheels; they first spin against his quivering flesh, but as his grip increases, they slip less and less, slowing down in the process, until the RPM drops to a point where the engine stalls.
I still have a hard time grasping the concept.
It’s just that it is completely normal for an engine’s output rpm to be limited because it is labouring against a load, and this is no different.
Same thing with two mismatched cyclists on a tandem; the weaker one still contributes to the overall power.
Just wanted to pick up on this. Electric motors are used in-wheel on large earthmoving equipment, and in Diesel-Electric train engines, and they load-share.
In the synchronous electric motor used for large equipment, the torque is proportional to the torque angle. If a wheel slips, it looses torque. If a wheel stalls, it gains torque.