ElectricMotorcycleForum.com

Tony,

As applies to your question, "When there are no gear ratio, can the front and rear's horsepower output be 50:50?" I would point out that the power delivered by an electric motors (and especially in the case of 2 matching electric motors) is proportional to the electric power delivered to the motors.  Electric power is measured variously as V*I (voltage x current), V^2/R (voltage squared divided by the load resistance), and I^2*R (current squared times the load resistance.)  The torque developed is proportional to the power.

So to a good approximation, you can deliver whatever arbitrary ratio of power you choose  to each wheel  by controlling the instantaneous voltage and current you deliver to each wheel's corresponding motor.  This holds absolutely true, but is both complicated and simplified slightly by the fact that most electric vehicles use 3-phase motors.  Complicated, because the math to derive the absolute power is complicated slightly more by involving factors of 3^.5, and 3^.5/2 (square root of 3; square root of 3 over 2) depending on specifics of the measurement of the current delivered to individual windings.  And simplified by the fact that (and this is the reason 3-phase is used in many large power electrical and electro-mechanical applications) the instantaneous power of 3-phase is CONSTANT. 

Single-phase is really best conceived of as delivering the signal and its inversion { sin(t)/2 and -sin(t)/2 } to the 2 inputs of the motor.  The instantaneous power is then proportional to V(t)*I(t), V(t)^2, or I(t)2.  If you think about it, sin(t) goes up and down, crossing the zero baseline in the middle.  In a single-phase motor, at each instant when the sin (and therefore the sin squared) functions cross the zero baseline, NO power is generated.  So the instantaneous power delivered by (say in a 60 Hz signal) a single phase motor is alternating between a high value (squared) and ZERO torque 120 times per second.  This generally produces an audible "buzz."

In 3-phase, the signals delivered to the 3 windings are sin waves mutually separated by 120?.  You can verify for yourself that
{ sin(t)^2 + sin(t+2?/3)^2 + sin(t+4?/3)^2 }, which is proportional to the instantaneous power and, hence, torque, is constant in any way you wish.  (I personally recommend https://www.wolframalpha.com.)  This is the reason 3-phase power has always been used virtually exclusively in motors for machine tools, and high voltage (high power) electrical transmission lines.  3-phase provides a much "smoother" energy source.

If you are unfamiliar with the operation of 3-phase motors, I recommend the animations in this vid:
How Electric Motors Work - 3 phase AC induction motors ac motor


and I highly recommend this short and concise article by Kazuya Shirahata:
Speed Control Methods of Various Types of Speed Control Motors
in HTML:
https://docplayer.net/21243181-Speed-control-methods-of-various-types-of-speed-control-motors-kazuya-shirahata.html
in Acrobat ("PDF"):
https://www.orientalmotor.com/brushless-dc-motors-gear-motors/technology/pdf/speed-control-methods-speed-control-motors.pdf
I note that this excellent young author and researcher is also in Taiwan.

To achieve a precise ratio of torque dynamically and instantaneously delivered to each wheel – including variations in supplied (battery) voltage due to dynamically-varying load – would require a complex (probably digital) special purpose dual motor speed controller.  But as I become more calibrated on the current (pun intended) state of your development of an all-wheel-drive motorcycle, I believe that you could achieve a reasonable approximation to whatever ratio of torque you desire to deliver to the 2 individual wheels by statically setting a constant ratio of electric power delivered to each motor. 

I am NOT advocating building a production motorcycle in this way, but as a test vehicle (pun, again, intended), you might consider using far larger (more highly parallel) batteries (WRT short-circuit current) than are required (so that the battery voltage remains approximately constant under load), measuring the motor winding resistance, and selecting an appropriate series resistor to be put in series with each of the motor windings of the motor you wish to deliver less torque.

Such an approach would NOT be acceptable in a production motorcycle, because a significant portion of the energy will be wasted in the series power resistors.  (Best to carefully calculate the maximum power requirements of said resistors:  Their power dissipation will be significant.)  By changing out the series power resistors for various values, you could determine what ratio of power between the 2 wheels you think makes the bike respond and handle best.  If you were adventurous, you could even use variable resistors (rheostats) or a 3-phase variac to adjust the relative power. 

{
Caveat:  I am somewhat squeamish about this adjustable power-ratio approach, because I think the probability of knocking the adjustable loads out of kilter during test flights is high, and the consequences could be devastating:  Both in terms of causing a crash, and and/or possibly burning out motor windings.  That's why I say the adjustable load approach is only for the "adventurous."  (As a biker, I'm sure you catch my meaning; danger is our middle-name.)
}

Both the danger of crashing during a test-flight, and the convenient availability of a "lab-bench space on the bike" are reasons that I suggest the possibility of first prototyping this beast using a commercial e-scooter.

I wish Craig Vetter were here to weigh in with his invaluable opinion.

Best of luck in your venture!  Wish I were in Taiwan to help with it!!!

godot

Tony,

I can't tell you what the problem is without more information.  I need to see the electronic schematic for what components you are combining, and, in the case that you have a wiring error, I would need to probe your wiring with a VOM.  No biggie; just details.

I don't know if you are using a bistable throttle, like you see on commercial scooters, or a proportional throttle controller like you see on a Zero.  My guess is the latter, which would mean that you will need to diode isolate the two speed controller inputs from each other, or one will find an unintentional electrical path through the other. 

Another likely problem would be that you think the 2 speed controllers are independent, but they are sharing the same chassis ground (metal frame of the bike) which can lead to unintended electrical paths.

But the most likely problem of all is usually that there is just a wiring error somewhere, or a short.  I can show you how to find these things quickly with a voltmeter.  But the most important thing is to know what we are looking at.

If you are feeding the same proportional throttle signal to 2 speed controllers -- even if they are precisely the same model of speed controller -- one will "current hog" and steal the lion's share of the electrical current from the throttle.  Because of the non-linear nature of dominant current paths, current-hogging is an effect which takes place and causes problems even if you have perfectly matched components -- for example transistors or diodes.  One will randomly draw slightly more current, and as it becomes dominant. it will become an even more efficient current path of least resistance, and hog even more current.  Hence:  "current hogging."

How is your project going?

I have wanted to build a 2 motor electric motorcycle for a long time.  I just discovered this forum, and am thrilled that someone else is crazy enough to want to do this!

Controlling the distribution of torque to the 2 separate motors is a difficult control problem.  It is a complex electronic control problem which requires a highly intelligent electronic control system with multiple kinds of sensor inputs.  The controller must actively shift the balance of electric power delivered to each wheel instantaneously depending on the immediate circumstance of each moment of the ride.

Recall how complex the motor speed controller is for a Tesla, and Musk has the advantage of 4 points of contact, so his vehicle maintains static stability even if he screws up the control somewhat.  If the motor speed controller on a bike misestimates the balance of torque, it can easily lead to loss of dynamic stability (which is the only kind you have on a bike), resulting in a fall.  And I haven't even mentioned the difficulties involved in handling wheelies and burnouts.  But I am sure it can all be handled safely – given a rational development program.

If you are in California, I would like to help you build this beast.

Thank you.

Is the OP associated with Vetter Fairings?