Firestorm Drive System / Dual Differential

I have been watching back over Robotwars and I have just watched Season 4 Heat C with Firestorm 2.

I remember looking at this before but I think I am right in saying they used some kind of differential rather than the standard left and right drive motors

I have seen versions of this done in lego but I cant see how they would have fitted it inside the machine. I have spotted Elliptical/Planetary Differential drives but does anyone have any images of the insides of Firestorm showing this mechanism?

Trawled through my images but couldn't find anything I'm afraid.

But yeah you're right. I got a good look at it back in 2005 at an event and, basically, it had one big motor that does forward and back, and two smaller drill motors (bigger than our FW ones) for doing left and right (and then of course, all stick positions in between). From what I remember, the big motor rotated a structure that drove the wheels, but also contained the two drill motors, and the whole assembly rotated when it went fwd/back. Then the two drill motors drove the wheels independently through the differential.

Not the best description I know, but my memory is hazy and my understanding of it isn't the best. Hopefully someone who saw it more often/knows properly how it works can come along and describe it better!

I've got one on my PC of the differential on the plans.

or http://web.archive.org/web/201109010...irestorm.co.uk

I cant get the archive to work. Any chance you can upload the plans?

Next time, I'm on my PC. I'm on my mobile most times

Attachment 3751
Click here for the full sized image
search www.gbone1.force9.co.uk* in the wayback machine for all the pages it has because the navigation on the archived ones is mostly broken

http://web.archive.org/web/200501162...fferential.jpg

That photo.

Why would you use this?

Greater pushing power, better straight line & immobilisation redundancy.

With this you are basically guaranteed to go in a straight line. It makes it much easier to drive as you are varying one main speed input rather than trying top unify 2 separate systems. Also if the main motor does goes, you can still drive with the drill motors.

Also vice versa. You are still counted as mobile even if you can't steer. You can also use a large gearing on forward but a speedy gearing on the the sideways.

Do you know which motor they used for the fwd/reverse? I imagine it was pretty big if it was a single.

No idea at this stage. I am watching all the old Robotwars vids looking for firestorm. I know You get a good close shot of it somewhere I just cant remember when.
But what ever it was took up all the space behind the differential mechanism, that I am sure of.

looks impressive..... way too much work though, 2 x bosch 750 and a wotty job done.
If your really worried about going dead straight then use a gyro.

Ah, that makes sense, yeah. I was just wondering how good for the weight, friction losses, potential to break etc.. Any design like this floats my boat; clever bit of thinking.

Quote:

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Originally Posted by terry

looks impressive..... way too much work though, 2 x bosch 750 and a wotty job done.
If your really worried about going dead straight then use a gyro.

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I am not interested in going straight, I just want to know how it works. But its not to much effort with the benefits that it brings over the normal left and right motor system. But hey, I don't build heavies so what do I know. It would be a great technical challenge to get it in a feather! Ooooo, hours of fun to be had there!

The basic gist of this is that the 2 smaller motors power the planetary gears in the diff and the crown wheel holds the assembly still. If you spin the small motors one way the robot will turn left, spin them the other and it'll turn right.

To go forwards/backwards the big motor will spin the crown wheel and the whole assembly will turn forwards or backwards. By combining the effect of the fwd/bckwd motor and the two steering motors you get the full range of motion for things like steering slightly whilst driving forwards.

Took me far too long to understand differential drive. Amazingly it took a video from the WW2 era to help me understand it
https://www.youtube.com/watch?v=ZoThxbFr6ow