Most real tanks and other track vehicles work with one motor driving both tracks and steer by applying a brake to one track. That is if you slow or stop the track on the left the machine will turn to the left.

Obviously with this arrangement both tracks have to be going in the same direction, you can not have the left track going forward and the right track going backwards. Vehicles driven by hydraulic motor can have tracks going in opposite directions, these would mainly be things like excavators and construction machinery.

Has anyone ever made anything like this, if so how did you do it, do you have drawings/photos.

I have an idea of how to make a braking system to allow steering but I'm interested in hearing what other people have tried.

The question is, how do you intend to apply a brake without using another motor?

Most real tanks and other track vehicles work with one motor driving both tracks and steer by applying a brake to one track. That is if you slow or stop the track on the left the machine will turn to the left.

Obviously with this arrangement both tracks have to be going in the same direction, you can not have the left track going forward and the right track going backwards. Vehicles driven by hydraulic motor can have tracks going in opposite directions, these would mainly be things like excavators and construction machinery.

Has anyone ever made anything like this, if so how did you do it, do you have drawings/photos.

I have an idea of how to make a braking system to allow steering but I'm interested in hearing what other people have tried.

I have never built anything like that myself, but I have seen people use one drive motor and a m motor for steering. You can use the differential part to accomplish this. Sorry, I don't have pictures.

You might want to check out Zblj's Ripsaw [link].

It is using more than one motor though: 2 motors are linked for drive, and the steering output of the RC unit applies brakes to one side or the other which transfers power through a differential to the other side and makes it turn. It does demonstrate the 'steer by applying a brake to one track' concept nicely though.

Make sure to check out his video on that page @ 0:53 to see the brakes in action.

Edited April 10, 201311 yr by Splat

@ grs: Welcome to Eurobricks! halhi141 made a Lego NXT-based "One Motor Driving/Turning Tracked Base" vehicle that could be adapted to use a Lego Power Functions (PF) motor instead. He provides photo-sequence Building Instructions too.

MySnailEatsPizza's "MAC Rover" (that halhi141 refers to) is here, with a video here. Again, you can adapt it to Power Functions elements. MySnailEatsPizza wrote, "The MAC Rover’s driving base is a large sturdy tracked base. It uses one motor ...In order to make the MAC Rover drive and steer using only one motor, I had to make a special mechanism. The motor turns a differential gear which turns the two track outputs. On one side of the differential there is a gear and a ratchet. The ratchet is pushed up when the motor rotates forwards, and this allows both tracks to turn. When the motor rotates backwards the ratchet locks into the gear. Because of the differential, only one of the tracks turns. The ratchet is a simple technic studded beam and a small gear rack. The differential turns two large wheels which power the tracks." There are pictures there (which I cannot link here).

Efferman made also one with one motor

http://www.brickshelf.com/cgi-bin/gallery.cgi?f=401452

And finally: http://sariel.pl/2009/01/subtractor/

Guess I should redraw these building instructions finally, they look ancient :)

My idea was to run the motor through a diff gear and have brake system on the outputs from the diff gear. Maybe large pulley wheels with a friction band around it using a second motor to apply pressure to either side.

Thanks for the replies, you've given me a few ideas to try out.

Guess I should redraw these building instructions finally, they look ancient :)

Don´t matter if they look ancient, the result is important. I used your system here and it worked perfect.

Crawler Working Range von BobBongo auf Flickr

;-)

Thanks, that's one good-looking result you've got there :)

I have done something similar some time ago. Simple add/sub gearing with two differentials. Using a second motor for pure braking instead of turning gears shouldn't be such a difficult task.

For me it was a nice exercise in studless technique with and PF motors.

Maybe you can check this MOC, which has almost the layout of real tanks.

Link at Technicbricks: White Tiger Tank

My idea was to run the motor through a diff gear and have brake system on the outputs from the diff gear. Maybe large pulley wheels with a friction band around it using a second motor to apply pressure to either side.

Thanks for the replies, you've given me a few ideas to try out.

This is exactly what you speak of

what your basically wanting to replicate is the kyosho blizzard braking system cause I remember when I was a kid it not having a dual motor but a single 540 motor to a rear axle/diff that had disk brakes on either side to stop it

And finally: http://sariel.pl/2009/01/subtractor/

Guess I should redraw these building instructions finally, they look ancient :)

Its that video that really looked old...