A quick tip as you get started.
Mount everything on a sheet of wood or even a cutting board and test it out.
No transference of electricity, cheap and you can easily view all your components.
Also, don't ever shorten any wires unless you're really almost done.
It's more work adding inches of wire than snipping them off....
Thanks, yeah I'll try that. And yeah, I know full-well about those wires from my Electronic Products GCSE and other work I've done in the past. Short wires are no fun at all.
Ok, just another quick question before I begin designing in earnest (and keeping it in this thread because I might as well). I've been doing plenty of research, and I'm looking at running the classic cannibalized drill gearmotors, but I wanted to go for a tracked robot rather than wheels. I realize this could go varying degrees of wrong, but all the same, I thought I'd give it a try. Though I'll be protecting the outer face of the treads and sprockets with armour, I wanted to go with metal tracks for durability, so I looked at some of the RC tank track designs. I'm an RC modelling newbie, but the Heng Long tracks (especially these type) caught my eye. Does anyone have any advice on tracks, or Heng Long ones specifically? I'm especially hung up on sprocket diameter, because I ideally want something that'll be as wide as the height of my robot (currently I'm thinking 70-90mm). I guess I could make my own sprockets, not sure how much trouble that would be.
So any ideas, or am I making a terrible mistake?
You'd have to use 4 drill motors with that, 2 on their own with tracks will die.
Ah, is that due to excess weight and tension in the tracks? Would it work with two if I geared them down to a lower speed (although I know this kind of defeats the purpose of drill motors)?
Also, I just thought, can you drive the two motors on one side with just one ESC, provided it can handle the current?
Last edited by R9000; 29th February 2016 at 19:56.
You wouldn't want to gear them down more, they're already on the slow end of drive.
If we take a 2wd bot and a 4wd bot as an example (Most the principles of a 4wd bot apply to tracks). When a 2wd bot turns the wheels just turn and follow the arc of the turn. When a 4wd bot turns the wheels slip sideways as they aren't lined up with the arc, this produces a high turning load as the motors now no longer have to turn the robot but also slide the wheels across the floor to some extent.
So while 2 drill motors will happily move and turn a 2wd bot a 4wd bot is a much bigger challenge and is likely to burn them out. Tracks add to this by having the turning load of 4wd with the extra tension and friction of tracks leading to a very quick death to motors. This is why most drill motored robots that are 4wd use 4 motors as they need more power.
You can do 2 motors for one side off of one esc, a TZ85 will be perfectly happy with 2 drill motors.
One thing with tracks, it's fine if you want to go that route but be warned they offer a lot of extra challenge and unreliability for no considerable gain other than looking cool. :P
Wow, thanks for all the info! Yeah that makes a lot of sense now, considering the centre of rotation is now in between all four wheels, and the tracks will scrape along the floor. I think since I'm going 4WD now, I'll still go with the tracks. I like a challenge, and hopefully if they get too unreliable I can just switch them out for wheels and maintain really decent pushing power.
Again, thanks for all the sage wisdom, I really appreciate it.
A 2wd drill powered robot will physically push 13.6kg without any problems. They key to out-pushing someone is getting under them and lifting their drive off the floor. Tracks are a world of pain.
That should be happening too with my robot. :P So are you saying tracks aren't worth it at all? Like I said, I can always switch to wheels retrospectively.Originally Posted by daveimi
I've been looking into the TZ85s today, but the only ones I can find are for brushless motors, and to my knowledge drill motors are brushed. Were you suggesting I mod them to be brushed, or are there brushed TZ85s I haven't seen? I'm also unsure on the current draw from 18v drill motors - could I use an ESC with lower current rating? I checked out Ranglebox, 85A ESCs are sold out but 30A ESCs are in stock.
Here Rapidrory suggested the motors need around 60A, but the thread ended with Giles going for making his own ESCs. I'm not opposed to this, but while I'm not clueless on PWMs, I don't think I have the experience to build a reliable ESC at this point.
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