rc_dude

iTrader: (131)

Does anyone know if anyone has tried something like this before? I really want to try it. The idea is the same as with many hybrid and electric full size cars, attach one motor to each tire.

No doubt this would be a hard and expensive project and I more than likely do not have the time to work on it much, but it sounds like a lot of fun to take a 1/10 truck and attach one 1/18 scale system to each wheel. It would create some very interesting handling characteristics and probably be fun to drive or race as a result.

This is probably a more complicated project that what it's worth but if you were to do this, you could fine tune the amount of brake and throttle per wheel and even adjust the throttle curves for the front and rear to change the power distribution as you pick up the throttle.

I am only playing around with the idea for now but if I find a good platform and the time to do so, I will. Let me know what you guys think and if you know of any RC that would be better to use than the other. Since each differential would be replaced with a spur gear that would have to be supported on both sides, I would probably need a truck with a wide roll center and some room to work with where the diff goes.

Let me know what you guys think, I'd just like to play around with the idea for now, we'll see what the future holds.

mkiiina

iTrader: (71)

Couple quick problems I see it multiple esc's needed with associated wiring needing to be run over exposed (violently moving) suspension. To get around this it would be better to do it on an onroad car i would think. Additionally it would be a pain to sync everything (yes i know there are quad copters out there but its a slightly different beast in this application.)

Next big problem would be huge increase in unsprung weight. Not as sure of a work around for this as of currently.

Should be a cool project but it doesnt sound like you are that committed to it.

rc_dude

iTrader: (131)

Well the motors would be on the chassis still, so I think the hard part would be fitting 2 spur gears where the diff should go and supporting them.

I would love to commit to this project, I'm just trying to make sure its reasonable to persue before sinking a lot of money into it lol

RC10Nick

iTrader: (9)

I think you'd have trouble squeezing it all into an existing 1/10 scale package. You'd probably need to experiment with your own chassis design.

With that said, yes, I've thought of a project like this many times before. I think to really do it successfully, you have to be capable of programming an arduino, or some kind of microprocessor board, to control and synchronize all 4 motors, as well as provide advanced traction control capabilities you'd want for offroad. You would probably need an understanding of physics and the equations that govern motion/acceleration to derive the equations needed in the programming (which might even involve calculus), and a solid understanding of PID control loops.

In other words, it's no small project to undertake.

I've often thought that a good first step for a project such as this would be to take an existing 4wd car and replace the center drive shaft with a motor at each diff housing. You would basically be creating a smart center diff and you'd need a whole lot less custom machining to have 4 gearboxes.

If you decide to take up a project like this, keep us up to date! It sure does sound pretty interesting.

Chr1s

iTrader: (1)

This is definitely an interesting idea. I would take a look the brushless outrunner motors for planes as they typically spin at a lower rpm but can still deliver good power output. You might be able to just stick an out drive on the motor shaft and just mount them where the diff goes. You will need to do some calculations in order to size all this of course. I think you are right though, you need a car with wide inner pivots. Maybe start with an 1/8 scale or 4x4sct and custom make your pivots. As Nick stated, using the arduino is probably your best bet.

Cody01

iTrader: (40)

Inconsistency between the four would cause problems even if you managed to pull it off. Wrong type of motors. Now I do believe we will see hub motors on each wheel of small cars in near future. The movement will generate a charge effect. They will be like a larger version of the bicycle hub motors.

Dyingslow

iTrader: (1)

I would be very interested to see your idea implemented into a RC car. I have seen that implemented in full size vehicles and understand the programming challenges to be the biggest hurdle. When choosing your motors, don't forget that you can use much smaller motors if you are running them at each wheel and still have the same effective power to the ground. Programming the diff action will be your biggest and most rewarding challenged in my opinion.

Good luck.

rc_dude

iTrader: (131)

Thanks guys! If I were to take on this project, I'd probably have to wait till summer before I could get the time.

Nick-I'm find with doing all the calculations involved, I'm a college student studying mechanical engineering so it would be good hands on practice of all that theory as well. I'll also be getting access the the schools machine shop this summer to be able to work on it.
As for the controls, if I use the same model programmable esc for each motor I could just program the throttle curves and end point to each one and run them off the same signal.

Chris- the out runners would be a good idea, but I doubt I could fit 2 of them in the diff's spot, which is why I though running a gearbox of some kind out of the suspension on onto the chassis so I could spin the motor outwards from the center

RC10Nick

iTrader: (9)

Perfect! I would love to see what you come up with! However, I truly believe you will need some sort of feedback control to monitor each wheel to ensure they are all spinning at the same rate, and that's where a microprocessor comes in. As a controls engineer, I can tell you the worst thing you can do is assume all your devices will work as you expect them too. It simply never works that way. You need feedback, which means you need some sort of encoder. Make friends with an EE major on campus and get him to help! In fact, try to make a project out of it. A cross functional engineering project would look real good on a resume as the lines between engineering functions tend to blur in the real world. Good luck!

lbenton

iTrader: (48)

I would like to know how the ackerman steering would be dealt with since a difference in speed will be need to each of the four wheels as it turned. Not saying it can not be done, it is math... but it would be an issue to address in the setup.

rc_dude

iTrader: (131)

Nick-My GF is actually an EE, but being long distance and her trying to find a job for next year would make that harder. I'm actually taking a class learning Matlab, I wonder if I could write a program in it to take the throttle and steering signals to split the power up for each wheel, something to look into since I don't know any good EE's yet at my school.

frankenstang

iTrader: (9)

An LST2 platform would be a good place to start. It's long enough for sure and will fit a smaller wheel and tire package if needed.

As soon as the idea of using TWO motors instead of the center diff was mentioned, the light bulb went off in my head too. How awesome would that be?

CanyonCarverR1

iTrader: (13)

Just a thought, my Airplane transmitter(JR10X) has several programmable mixes. You could mix the steering servo to the ESC's so that, for instance, when you turn left, the right side wheels spin faster than the left. Buying a used radio might be an easy way to test your theories before investing too much time and money.

rc_dude

iTrader: (131)

The two motors is where ill start, and for that really any metal chassis vehicle will work, but when/if the 4 motor design comes, ill need something with more room inside the suspension.

fredswain

iTrader: (1)

A place to start my be with quadracopter parts. Their electronics already control multiple motors. Steering may be fun to integrate though.