Drive motor options

[Liftoff]

Hi there, need some advice/suggestions regarding drive motors for my feather build.

As some might know I'm using track drive on my machine and the motors I'm using are the gimson Gr02 18v. I used these motors as their compact size and little weight makes them ideal.

Unfortunately when the first test drive was done the motors overloaded and almost burnt! Don't think the issue is with the motors themselves but rather with the tracks...they do put some load on the motors even when free wheeling, which increases as you steer.

What I'd like to know is if there's any motor I could get with more power than the Gr02 but which could be coupled to the Gr02 gearbox and of the same length. Diameter up to 55mm is ok, larger than that will not fit....

[Ellis]

The problem with coupling a more powerful motor to the gearboxes, which would be possible with an adapter plate of some sort, is the added torque and power going through the gearboxes. They won't last long, with enough resistance to almost burn out a motor on the output, and a motor that will just keep on spinning on the input, I imagine the drill internals will get eaten.

You may need to look into some 775 16:1 Banebots motors and gearboxes, or similar. They aren't cheap (US-only, too) but they'll be more suited to the job. The gearboxes are also roughly 40x40, so with some new bolt holes they might be able to just drop in. Whether they'd arrive soon enough for you, I don't know. For similar money there's the Magnum 775s, also US based.

[typhoon_driver]

banebots seconded

[Liftoff]

Thanks Ellis, what I was thinking was of reducing the motor shaft diameter and press the input gear on to it, then mount it directly to the gearbox just like the original motor (maybe with some minor machining) But if the banebots are of similar size but with more power then I'll have a look at their specs to compare... I think it will pay off to invest a bit more in a better matched motor rather than end up burning up motors not suited for the job.
Something else, don't know if it has any effect on what happened, the gearboxes I run are 1:36 ratio...

[Max]

I presume you weren't using the Gimson 24v motors as these had big problems with lots of people's motors failing under relatively little load? If you were using them then I'd suggest changing to the 18v motors

[Liftoff]

Yes I originally had the 24v motors, but had them replaced by the 18v ones, so they should be ok. I had the output shaft of the motors machined into a square drive, and in turn that engaged into the track drive wheel which is supported on both sides by ball bearings...that is there's no side loads on the motor.
Will post a couple of pics tomorrow when I'm back home for better understanding.

Regarding the banebots, do they only do 16:1 ratios? Think that's too fast! What do you guys use?

[daveimi]

Do they do Banebots stuff with 3/8 output shaft that you could put RoboChallenge wheels on? I'm not into the keyed shafts etc.

[Ellis]

Here's their site: http://banebots.com/index.html

In their range of gearboxes (the p60 sizes) suitable for 775 motors (a step up from 550s), only the 16:1 option is close enough to useful (next closest are 4:1 and 64:1). It makes for, at nominal voltage, an output speed of roughly 1250rpm. That is a lot faster than those 36:1 Gimson gearboxes, yes, which spin at around 550rpm. But I'd expect the motors to handle it, they're very punchy.

That is your only option for the 775 motor range from banebots.

They sell many more ratios for their gearboxes suited to 550 motors, including 16:1 again, 20:1 and 26:1. I didn't bother mentioning those above because they're basically the same motors as used in Gimsons, and the overheating problem would be the same. Worse, perhaps, due to the lower reductions. The next reduction up is 64:1, which would make for a very slow robot.

You can get 775 motors coupled to "Magnum" gearboxes, which are 20:1. http://www.robotpower.com/products/magnum775_info.html - looking at 650w from one of those at 18v, I should think that would be enough! Makes for about 900rpm, again at 18v. They look very very solid to me.


It may be cheaper to come up with a custom solution?
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As for smaller shafts, I have never seen that on Banebots, but take a look at their (dodgy!) site, they might do. Could be done on a lathe. Or, you may want to look into modifying the wheels instead of the gearboxes.

[Liftoff]

So how's the speed like with the banebots 16:1? I mean are they driveable or it's like having a loose firework! And what about the esc? I got the 2x60 sabretooth, will it handle the 775 banes? I know there's a lot of bias against them, but as I already got it I just want to know if its outright incompatible or not

[Ellis]

I don't know if that ESC will do the job. I have heard the same general dislike towards them but have no experience, and can't really comment. Statistically they should handle two 775s fine. Statistically. Two TZ85a speedos from Botbitz would do it.

As for speed, I don't know how big the driving wheels on your tracks are, but at say 80mm, you'd get about 11mph/18kmh. That isn't crazy fast. Many machines are that fast (Tormenta 2 does about that) and faster. I imagine it'd be more a worry of if the added stresses from the speed increase would cause problems with the tracks. Skidding sideways to a halt from 11mph will make the tracks work harder than from say, 5mph.

The Magnum gearboxes and motors would garner around 8-9mph, again assuming 80mm driving wheels and 18v. They're more expensive but potentially the better option, they look a fair bit chunkier and the added power/reduction won't go amiss when shoving a tracked machine around.

Plus, more speed = more cool factor, right? Right!