Throttle management

Rcnut51

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Mar 3, 2022
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I have a thumb throttle that when you push it and let go it returns I assume this has a spring to return normal, so if I want it to stay in any position and manually pull it back can I remove the spring? I plan on using 2 thumb throttles to work my 2 hub motors one on each side of the kids riding motorized plane. Can I wire both motors to run off one throttle? Both motors are 36v 350watt.
 
Rcnut51 said:
I have a thumb throttle that when you push it and let go it returns I assume this has a spring to return normal,
Yes.

so if I want it to stay in any position and manually pull it back can I remove the spring?
Yes, but I am not sure that is all I would recommend that for a kid's (well, any) airplane (which sounds like a possible problem/risk itself, unless they're older than I'm imagining, could they fly a plane safely?). You would probably want to increase the friction on the mechanics so that the throttle stays in whatever position it is put in, and doesn't move from vibration, etc. while in the air.

I plan on using 2 thumb throttles to work my 2 hub motors one on each side of the kids riding motorized plane.
Hub motors for a plane? Not sure most hubmotors are made precisely enough for the high RPM you'll need for propellers (and will probably require a pretty high voltage to get that speed).

You could use gearing/chaindrive/etc from the motor to the prop to increase the prop RPM without as much high speed stress on the hubmotor.

Can I wire both motors to run off one throttle? Both motors are 36v 350watt.

Yes, you can, but youre' not actually wiring the motors to run off the throttle, you'll need to wire the throttle to a controller (one for each motor). There are a number of threads about dual-motor systems and wiring considerations, etc., but basically you only use the +v and ground from one controller to run the throttle, and then use the signal to both controllers. (the other controller's ground is provided by battery negative, only, to prevent ground loop problems--if things don't work as expected, you could use ground from both controllers to the throttle, but still only use one for the +V.


However: if you have slightly assymmetric thrust from the propellers for whatever reason, you then have no way (with teh motors) for the pilot to compensate for this by reducing power to one motor, or increasing it to the other. (presuming one motor/prop on each side, rather than both centralized like a pusher/puller or stacked vertically over each other).
 
I'm not sure you understand, this is like a electric car but an airplane, it stays grounded just driving it around the driveway, so I need 2 controllers but 1 throttle wired into both controllers? Or 1 throttle per 1 controller then just mount both throttles next to each other to operate simultaneously?
 
Rcnut51 said:
I'm not sure you understand, this is like a electric car but an airplane, it stays grounded just driving it around the driveway,
Ah. Didnt' sound that way from the first post. ;)


so I need 2 controllers but 1 throttle wired into both controllers? Or 1 throttle per 1 controller then just mount both throttles next to each other to operate simultaneously?
That depends on what you want it to do, and how complex you are willing to go in building it, for the most simplistic operation by the "pilot'.

Presumably the hubmotors are one per wheel, on each side of the "wing landing gear"? And this won't be able to go fast enough to allow a rudder to steer via airflow?

If so, then if you want to be able to steer it, you either need to be able to pivot the centerline gear (tail or nose) via the mechanical controls (possibly mechanically complex), or you need to be able to separately control the speed of each wheel motor.

One throttle can do that, if you also have an offset control built into the steering control. For instance, a potentiometer wired so it's center pin receives the throttle signal from the single throttle (which would be the "speed control"), and then one outer pin goes to the throttle input of one controller, and the other outer pin goes to the other controller's throttle input. That should cause a lower voltage to the one with more resistance, whichever one the potentiometer is turned "away" from. Depending on the controller design it might take more parts than this, but if there is sufficient change in the (tiny) current flow because of the resistance in the throttle signal, it could be enough to cause turning. Easy enough to test. Probably a 10kohm or 20kohm potentiometer (pot) would work; experimentation might be required.

(if a more complex circuit is needed, it may be easier to just use independent throttles).


Independent throttles for each motor would allow steering easily, and if you wish you could create a mechanical steering control like a pilot's steering column that when pushed forward just moves both throttles the same, and when the "steering wheel" is turned it changes the amount each throttle is moved. Mechanically, that might be complex; I've no quick ideas on how to design that.

Would be easier to design just using two separate throttle controls as if they were on an actual plane, but that would be harder to use to steer with.


The easiest to use would be to have the steering column push forward to increase speed, by simply having it pull a cable-operated throttle's cable; you can control the amount of cable pull by where the cable attaches to the column above the pivot, so that it gives the right ratio of pull to throttle movement.

Then that single throttle output would go to that potentiometer voltage divider as previously described, which would be physically controled by turning the "wheel" at the top of the column. (or using the rudder pedals, if you have those). That can be a simple direct control, literally mounting the wheel as a giant "knob" on the pot shaft.


Alternately, if using the cable operated throttle, you might use two of them, one for each controller. The cables would be fixed to the ends of a pivoting bar, with the pivot attached to the base of the control column, at whatever point gives half the total amount of cable pull when steering is centered and column is pushed all the way forward.

That pivoting bar is then connected (via cables? rods?) to the steering wheel at the top of the column so that as the wheel is turned, it pulls one of the throttles more than the other, causing steering.

Experimentation would probably be needed to get the right ratios of steering to speed to cable travel, etc.


A trimpot can be installed on each controller's throttle input as a voltage divider to "tune" each one's response to be even, if necessary, and also so you can limit the total system speed by turning them down if needed. It would be wired so the center pin goes to the controllers' throttle input, one outside pin to ground, and the other outside pin to the throttle signal coming from your control system.
 
I have built 3 pedal planes and 2 pedal helicopters (my own design, 1 apache and 1 2seat huey) the steering will be mechanical stick to nose wheel I'm just looking for some guidance on using 2 scooter hub brushless motors on the main landing gears for power and want to know if I need 2 throttles one for each motor or can I use 1 throttle controller output for both motors.
 
Then the first method I gave for connecting 1 throttle to two controllers is simplest.

(you do need two controllers, one for each motor)
 
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