McAllister MX Pro

[Phin]

At least I believe it's an MX Pro. From the old RCCA articles I found on Pro10-Classic.com the difference between the McAllister Outlaw Stocker and the MX Pro were the Pro was upgraded with a graphite chassis, graphite rear axle, bearings and the rear "Power Pod" ....making it more like the Delta Villan. The car I got off eBay last week looks like it has almost all of those upgrades but the chassis appears to be fiberglass. So it may be an Outlaw upgraded into an MX Pro.

Car's in mint condition. All I've done to it so far is wipe off the light layer of dust then upgrade the nylon rear "damper" to a new Delta shock, and add a Villan bumper I happened to have from a parts lot I picked up awhile back. Also put on some Proline wheels for rubber tires but they're likely only temporary.

Not sure where I'm going with this car but while looking at the rear pod it crossed my mind that it's so wide it could almost fit two 540 motors...so naturally now I want to put two motors in the car that will run each wheel individually. To do so I think I'm going to need to find a couple of brushed 380 modified motors (LRP made some nice ones), a second diff hub, and another graphite axle.

If I get the two motors working and the car still likes to turn I'll look at upgrading the front suspension to something like a Cheetah front end, or even better an IFS from a Delta Villan. I'll also add a couple of side shocks to the rear pod.

If the car doesn't do corners I'll keep the front end, lock down the side-to-side at the rear pod and turn the car into a drag racer. With 1.5" wide foams at the rear I can bring the rear track down to 200mm.

[Mr. ED]

If you want to run 2 motors you'll need to ditch the diff, not get a second one!
A solid axle with the same size spur and pinion on both sides is the only thing that can make it run straight.

[Phin]

I need the diff hub just to mount the second spur...not to actually work as a diff. As a matter of fact I'm thinking about putting those Traxxas friction pegs in the spur instead of balls to turn both spurs into a slipper.

It also won't be a solid axle....they won't be connected at the center. Essentially I'm hoping to build something like the wheel hub motors you find in some electric 1:1 cars.

Both motors will be connected to one ESC and the same batteries. I believe the idea is that I would still have the potential for actual turning without a diff since each electric motors would draw more or less power as it's needed naturally depending on the torque forces at the wheel the motor is attached to.

[Mr. ED]

individual moters on the right and left can only work if you have a speedcontroller capable of sensing and commanding RPM.
With standard rc material you will allways have differences between the left and right and the car will be impossible to drive straight.
Think of how a tank turns, that's what you'll get, but less controlled

[GoMachV]

Just add a gyro, problem solved

Please please please get video of this maiden voyage!

Btw, if it is bugging you I have a sealed MX pro at home I could root thru and probably determine if that's what you have

[Phin]

individual moters on the right and left can only work if you have a speedcontroller capable of sensing and commanding RPM.
With standard rc material you will allways have differences between the left and right and the car will be impossible to drive straight.
Think of how a tank turns, that's what you'll get, but less controlled

If the car pulls to one side I'll set the motors on the appropriate sides so car favors left turns and run it as an oval.

I've actually already previously considered the possibility of how gearing each wheel differently could replicate tire stagger, and how it would make the car perform as a dirt oval racer with a Villan IFS.

Just add a gyro, problem solved

Please please please get video of this maiden voyage!

Btw, if it is bugging you I have a sealed MX pro at home I could root thru and probably determine if that's what you have

You're just hoping to watch the car explode aren't you?

Whether it's an MX Pro or an upgraded Outlaw is not bugging me at all so don't go opening a sealed box just to find out. I'll be putting an email out to McAllister to try and find a second wheel hub so I'll ask him about it.

The chassis material is the same stuff used to make the stock T2 shock tower I have (PN ASC7352) which is labeled as "Black Fiberglass" on the header card.

[Coelacanth]

individual moters on the right and left can only work if you have a speedcontroller capable of sensing and commanding RPM.
With standard rc material you will allways have differences between the left and right and the car will be impossible to drive straight.
Think of how a tank turns, that's what you'll get, but less controlled

If the car pulls to one side I'll set the motors on the appropriate sides so car favors left turns and run it as an oval.

LOL So, depending on the speed difference from one side to the other, instead of steering with your front end, you'll just accelerate or decelerate? Yeah, take vids, because this project is headed for trouble. Unless you can precisely control the rpm of each motor, I predict some rather schizophrenic driving characteristics.

[EvolutionRevolution]

Use a four channel transmitter and receiver and steer it like an old school tank. 1 ESC per motor, both sticks forward = car goes forward, both sticks back = car brakes, 1 stick forward = theoretically it steers , being a pan car it actually will spin out of control and smash something, breaking.

Honestly, why waste a perfectly good vintage pan car? It just sounds like destruction and injury waiting to happen.

[Phin]

...
LOL So, depending on the speed difference from one side to the other, instead of steering with your front end, you'll just accelerate or decelerate? Yeah, take vids, because this project is headed for trouble. Unless you can precisely control the rpm of each motor, I predict some rather schizophrenic driving characteristics.

Whachu talkin' 'bout Willis? With both motors wired to the same ESC they're receiving the same throttle input..so any speed difference between the two motors' speeds at half throttle will be consistent at full throttle. i.e. if motor A rotates 10% faster then motor B it will always be 10% faster regardless of throttle setting. Accelerating/decelerating couldn't steer the car because turning radius would remain constant...all accelerating/decelerating would do is make the car travel in that same circle faster or slower.

If the car ends up pulling in one direction steering in that direction would be done as it usually is through the front wheels...however counter steering would be needed to go straight, and turning radius in the opposite direction would be godawful.

In a tank, throttle could be used to steer the car because, as EvoRevo suggested, each motor gets it's own speed control and receives it's own throttle input. I'm not trying to build an RC tank though....what I'm looking at would be more like an RC twin prop boat.


As both motors are being controlled by one ESC and splitting power from one set of batteries they are not actually independent of each other. However allowing each rear wheel to be able to spin independently of each other will allow torque at the wheel to adjust the RPM of each motor and shift the voltage from the motor that doesn't want it to the one that does. This should allow the car to turn without the use of a differential.

e.g. in a turn, the motor at the inside wheel will want to spin at a lower RPM and will therefore suck less voltage from the battery, while the motor at the outside wheel will want to spin at a faster RPM and draw up that extra voltage from the inside wheel. Since electricity wants to take the path of least resistance it will travel from one motor to the other naturally, without any commands needed from a special ESC. (though if an ESC could deliver that kind of RPM control command to each motor handling on the car would be awesome).

A solid rear axle wouldn't allow this so a solid rear axle car would only go straight well....it would turn like a block of wood.


The same principle should keep the car going straight because if a faster motor wants to turn the car, while the front wheels want to keep the car pointed forward, that faster motor would end up acting as the inside motor of a turn.

...
Honestly, why waste a perfectly good vintage pan car? It just sounds like destruction and injury waiting to happen.

If I can be honest too, I don't expect the car will go any faster with two 380 motors than it would with a single 540 motor, since the two motors will each be taking half the voltage from the batteries that a single motor would use.

What I'd be doing is using two ponies to pull my cart instead of a single horse.

[Coelacanth]

I think your comparison to a boat with 2 motors is flawed logic. With a boat, you only have a single "wheel" so-to-speak, as the hull is a single plane; a straight line. A boat doesn't have 2 separate steering mechanisms (left side & right side) like a car does. Moreover, the motors themselves do the steering...which ties in with my previous comment, half-jokingly saying you could control right/left with speed changes. That won't work so good with a car on a flat, hard surface with almost no resistance compared to water. The effect would be exaggerated & magnified many times moreso than with a boat.

I know your theory seems logical--with the 2 motors receiving the same input from a single ESC, therefore they theoretically should spin at the same RPM--but that presumes a perfect world where 2 motors are identical in every way. That just doesn't exist in the real world, though. Even mass-produced motors have tolerance ranges. No two motors will ever perform identically, even if they're controlled by a single ESC.

At any rate, it should be a fun experiment, and we'll be enjoying the fun even more than you, I expect.

[Phin]

...A boat doesn't have 2 separate steering mechanisms (left side & right side) like a car does. Moreover, the motors themselves do the steering...

So what are rudders for?

[Coelacanth]

With most boats having outboards, the motors turn left/right and don't have rudders. Inboards usually do have rudders. Either system is hardly analogous to the steering setup of a typical land vehicle with wheels. But anyway, don't let me stop you from pursuing this project, I'll be watching with interest. If you get this driveable in your current description, I'll be the first to man up and admit you proved my logic wrong.

[GoMachV]

If traction was 100% it would be interesting to see if they would equal out. Ever run a stock clod buster in the economy mode? It runs the motors in series (1/2 voltage) and it acts like a third diff. When one end is unloaded it looses power at the drive wheel and spins the free revving motor wide open. I don't know on this project. It will be interesting.

And IF it blows up there better be a camera on it!

[Mr. ED]

You are oversimplifying things: each motor has a different performance curve. There is no constant offset between the 2; both start at 0 RPM.
Depending on how fast you go the car will make different turns, to the right at low speed to the left at higher, it's all possible and highly unpredicatable.

Even if it were constant the chance that the difference between both is just the right ratio to make the correct radius turn for your track is endless slim. And even if you are the luckiest b on earth, the moters will wear different and the steering will become different as a consequence.

I'm all about building and converting, but you really ought to look for a different idea as this won't work.

[GoMachV]

You know, another use for that width that would be kinda cool as I have never seen one on a pan car....

Nova 2 speed