Tracked Vehicle Control

[Andrew McKelvey 1]

I have an old Marx-A-Power Bulldozer which I am planning on installing some radio control to drive it. At the moment it has two brushed motors of 3v one for left track and one for right track with independent control.

I require my control to drive the vehicle forward backward and steer. I would like proportional speed control, it is either on or off at the moment, my guess is that those of us that have tanks and other tracked vehicles have a solution to the problem but I don’t know what it is, is there an esc that will do the job, do I need two esc’s, do I need a mix in my tranny to drive two channels, how is it done. Any info will be great fully received to point me in the right direction. I could quite easily design something and then find a solution of the shelf. I want to keep the 3v motors if I can so as to be reverse any mods I make.

[Dad_flyer]

I did similar for a two-prop boat with no rudder.

You will need two brushed ESCs, with reverse. They can be a pain as they are usually designed for cars and have a reverse lock where you need to make the transition from 'mid' to reverse twice. Then a good transmitter should be able to deal with the mixes. If I remember correctly, my very simple transmitter had not got enough mixes and I put in an Arduino Nano between the receiver and ESCs to deal with the mixing.

[Max Z]

THIS could be what you are looking for, dual esc with integrated mixer (which can be switched off)

 

Edit: sorry it says 2s-3s in the specs, which is probably too much for your 3V motors.

Edited February 9, 2022 by Max Z

[Max Z]

I am afraid you will encounter this more, most esc's have a built-in BEC, designed to power a 5V receiver and servo's, hence the 6V minimum you can see in the specs.

You could risk it, disable the BEC by pulling the red wire from the Rx connector and see if it will run on 1s. You will have to provide a separate 5V supply to the Rx then.

Edited February 9, 2022 by Max Z

[Dad_flyer]

4 hours ago, Max Z said:

I am afraid you will encounter this more, most esc's have a built-in BEC, designed to power a 5V receiver and servo's, hence the 6V minimum you can see in the specs.

 

You are right, I did not use car ESCs but DC motor H-bridge drivers. Which is why I would have needed the Arduino to translate the receiver PWM to talk to the motor driver. My mind is sieve. It means that the motor voltage is anything you like, but you will need to supply the 5V for the receiver and 3V for the motors.

[Steven S]

The Mtroniks Tank mixer was made for this job.  I use a similar type of "Robot" controller available locally in Canada for my sidewheel paddle wheeler RC model.

 

https://www.cornwallmodelboats.co.uk/cgi-bin/sh000001.pl?WD=mtroniks&PN=Mtroniks-Tank-Mixer-Waterproof-MMT.html#SID=1866

[Steven S]

https://www.robotshop.com/ca/en/sabertooth-dual-12a-regenerative-motor-driver.html

 

This is the Sabertooth controller in my boat.  The paddlewheels can go forward, reverse, also in opposite directions and at any speed.  I control it with my Spectrum Dx6 using one stick for throttle and the other stick for rudder / motor direction.

 

Edited February 9, 2022 by Steven S

[Max Z]

10 hours ago, Steven S said:

This is the Sabertooth controller in my boat.

Again, the specs say 6V - 12V, with a BEC to power the Rx. And there is nothing in there suggesting you can run the motors at a lower voltage.

 

It looks like your only option(?) is to go with arduino and a separate set of motor drivers. I had a quick search to find some suitable code but no succes. Should not be very difficult to develop though.

 

Driving a track vehicle with a simple 2 channel mixer, intended for aircraft controlling a V-tail set up, now in use for speed+steering wheel control will result in an unexpected sensation when compared to normal front wheel steering, when in reverse the turning direction will appear to be wrong. This is because the steering wheel will keep the rotation direction around the vertical axis the same, and with front wheel steering the rotation is changing with the direction of the vehicle, forward or backward.

[Max Z]

And then there is OpenTX: 

 

I have not gone through this yet to see if this overcomes the "wrong" steering in reverse though.

And you will still need a pair of suitable speed controllers.........

Edited February 10, 2022 by Max Z

[Lima Hotel Foxtrot]

On 09/02/2022 at 13:18, Dad_flyer said:

I did similar for a two-prop boat with no rudder.

You will need two brushed ESCs, with reverse. They can be a pain as they are usually designed for cars and have a reverse lock where you need to make the transition from 'mid' to reverse twice. Then a good transmitter should be able to deal with the mixes. If I remember correctly, my very simple transmitter had not got enough mixes and I put in an Arduino Nano between the receiver and ESCs to deal with the mixing.

Unless it's a crawler esc, or configurable for a crawler, which removes the brake function and gives you equal range directly from forward to reverse. 

[Sparks]

7 hours ago, Max Z said:

Driving a track vehicle with a simple 2 channel mixer, intended for aircraft controlling a V-tail set up, now in use for speed+steering wheel control will result in an unexpected sensation when compared to normal front wheel steering, when in reverse the turning direction will appear to be wrong. This is because the steering wheel will keep the rotation direction around the vertical axis the same, and with front wheel steering the rotation is changing with the direction of the vehicle, forward or backward.

 

These steering modes are refered to as 'Crescent' and 'Star' steer.

 

With Crescent steer, the vehicle will retrace its forward path in reverse. So, if you run the vehicle repeatedly forward and backwards the steering path will be crescent shaped (like a car).

 

With Star steer, the steering direction is reversed when going backwards. So, if you run the vehicle repeatedly forward and backwards the steering path will be star shaped.

 

 

[Andrew McKelvey 1]

Thanks for the replies guys, I am in a much better position in understanding what I need to do. At the moment the control is on off via a couple of levers which are effectively change over contacts. I need to find out how much current the motors draw but as it was power by 4;U2 cells 2 each side it isn’t going to be a lot. I need to do a bit of experimentation with one of these mixers or even a couple of brushed esc connected to a receiver and see if something like a v tail mix will do it but I definitely have more idea now Thanks. I would have thought that the esc’s being proportional the voltage applied is also proportional so even a six volts i can limit the volts to about three, I am running it off 2 Li Ion cells at the moment which are 3.4v without any problem.

Edited February 11, 2022 by Andrew McKelvey 1

[Denis Watkins]

On 09/02/2022 at 13:18, Dad_flyer said:

I did similar for a two-prop boat with no rudder.

You will need two brushed ESCs, with reverse. They can be a pain as they are usually designed for cars and have a reverse lock where you need to make the transition from 'mid' to reverse twice. Then a good transmitter should be able to deal with the mixes. If I remember correctly, my very simple transmitter had not got enough mixes and I put in an Arduino Nano between the receiver and ESCs to deal with the mixing.

 

Dad flyer has already given the correct brushed solution available.

The problem with trial and error is the chance to fry all the bulldozer wiring.

The brushed controller is very low cost and can be added or removed as you planned, if you did not like the solution.

[Jonathan S]

Andrew, 

I was looking into making a 1/35 model rc a while ago.  I never did but there are a number of sites that discuss how to do it.  I wonder what volts they need might work. 

 

http://35rctank.com/

[Denis Watkins]

14 hours ago, Jonathan S said:

Andrew, 

I was looking into making a 1/35 model rc a while ago.  I never did but there are a number of sites that discuss how to do it.  I wonder what volts they need might work. 

 

http://35rctank.com/

 

The good thing nowadays Andrew, are the available miniature motors with gearboxes, and single or double axle and straight through or 90°.

Like a aeroplane, consider the weight in choosing the motor voltage, which in turn governs the cell count.

You can even choose your gearbox RPM.

 

[Max Z]

36 minutes ago, Denis Watkins said:

The good thing nowadays Andrew, are the available miniature motors with gearboxes

I bought two of THESE to experiment with, fine little units!

[Max Z]

This guy really went to town with his conversion:

https://www.youtube.com/watch?v=YtePwzrzLOk

 

If that is the original maximum speed, it makes you wonder why Andrew is keen on proportional speed control?

 

Cheers,

Max.

[Andrew McKelvey 1]

I just thought that proportional speed control would be a bi product of using off the shelf speed controllers with radio control, just a bit more refined than on off. I have made up a battery with Li Ion cells from a redundant laptop battery three in parallel each side which is about 3.3v and I charge it with one of my multi chargers at 6 and a bit volts both banks of cells are in series and it works well, I have only recharged it once and have had the bulldozer all over the house a lot better than the old U2 batteries as I seem to remember

[Max Z]

It may or may not be of use to the topic starter, but this topic inspired me to pick up a project started some years ago.

I devised a 2-channel mixer in Arduino for controlling a track vehicle. Contrary to the use of an external V-tail mixer as used for aeroplanes, this one is mimicking a front wheel steering car. The properties:

It will maintain (approximately) the same turning radius with varying speeds, as the inside track slows down proportionally to the forward/backward speed.

Reversing to the left requires steering to the left, the same to the right, so unlike the behaviour I described in my post of Feb. 10.

Any 2-channel transmitter can be used, as no internal mixing or manipulating channel outputs is required.

As a bonus, the vehicle can swivel around its center, just keep the sticks neutral for a quarter second, then move the steering stick first. If the speed stick is moved first, the vehicle will resume "normal" forward/backward steering.

 

Here are my videos on YT:

 

https://youtu.be/6eCfx49-bnQ

 

https://youtu.be/mdWiSlG8kYk

 

Apart from the ProMini Arduino board, you can see a TB6612FNG dual motor driver, which uses a separate power connection for the motors as opposed to the power source for the Arduino and the logic part of the driver. However, in this case the same power source has been used for the motors and via the on-board step-down regulator of the Arduino for both boards.

 

I do realise that this has nothing to do with flying, but as the topic already existed I decided to just jump aboard ?

 

 

Edited March 15, 2022 by Max Z

[Andrew McKelvey 1]

Max Z

I don't suppose you have the script and a schematic available that you could send me. I have an Arduino ready to program and hook up..

[Max Z]

I do and will send it. That is, when I have found the connections schematic I did. If not, I will do a quick sketch.

Which one do you prefer, the one with a dedicated dual motor driver board, or the one for connecting two ESD's to (forward/reverse type).

 

In any case, please send me a PM with your email address.

 

Cheers,

Max.

[Max Z]

Hi Andrew,

I have sent you a PM with the relevant attachments, no need for your email address.

 

Cheers,

Max.