The drive units have failed (totally!). I'm looking at the gimson GR2 units. Other than the expected work to make them fit, will they fit in the same space as an Argos unit with a robochallenge 75mm wheel? It's the length I'm concerned about as my bot is very compact (see the pic earlier in this post).
Cheers
Dan
yes their shorter
How have the drives failed? We have just bought a bunch of innards to make our drills 24:1...
Did the pins that hold the gears on the second stage (the 6:1 bit as against to the Gimson first stage which is 4:1) fall out/come loose?
If yes, that's a good thing (for me anyway, that's how all of our drills have failed to date), if you stripped the first stage of gears, that worries me, we just spent 65 quid on parts!
Yeah, the pins came loose. Put it all back together but didn't work, could hear it grinding when you turned the wheel. Did get a good amount of use out of them though. Will contact gimson robotics on Monday to get hold of all the parts I need.
Got a bit of an issue with the control as well but Mario helped me out with that. I think the thermal protection on the escs was kicking in as all the motors and ESCs were completely sealed. This then lead to the drive dying about 2 mins into the fight then being fine 5 mins later!
Ah, okay. We should be able to avoid that as we're also going to be running 18v motors, but at 5s. I don't see why they should fail, the setup will be running more or less within factory spec. It can only be better than our current setup where we blow something up in every fight!
And yes, I think the max rating for the tz85s is 24v so you're probably just nudging their limits after a few minutes of battle. I saw some of the footage and it certainly was running fast!
Also Ewan may be able to advise better, but if you intend to run 18v Gimsons on 6s then you're likely to run into this problem again. The pin setup is the same as that in the average drill, so the failures may well happen in the same way unless the load is dropped by upping motor v or lowering the battery v.
Keep us posted.
What wheel size are you using? 100mm wheels with 24:1 and 18 volts is really pushing every thing to its limits, should work, it's just for how long is the question. I'm doing every thing I can to keep every thing cool in my robot and I still don't think mines going to last very long.
If you can, buy some 24V fans from Technobots and fit one for each motor, the bigger the better. That might help them last longer. You could also bend some Heatsinks out of sheet copper and attached them to the motors with thermal paste.
We have a single 40mmx40mm fan on Binkys 160HV for the weapon. It has never got hot even in heavy testing! A bit of air circulation can do wonders :-)
I don't see how motors working at their designed voltage on 100mm wheels is pushing it, really... It's only like having 16:1 banebots gearboxes and smaller wheels, same end ratio I mean. Plus we have four, so the load is spread out. If you're referring to Robob, I believe he's using 75mm wheels.
Also the issue with Robob's setup isn't the motors overheating at all, which is our experience with overvolting 12v motors to 5s, it's the torque they produce as a result of overvolting that kills the gearboxes. I'd still be running 12v motors at 18.5 if there were suitable gearboxes that can take the stress. The motors do get warm, but nothing more than I'd expect, and the power you get out of them is awesome.
best give a bit of background!
im using 75mm wheels and the gearboxes are very old. the output shafts are the same ones ive been using in my drill powered bots since my first event at the O2 so they were due to fail at some point. I can imagine the overvolted motors and increased speed will have exacerbated the problem a bit! luckily the GR02s will fit in nicely so ive emailed Ewan to get hold of the necessary parts (i just need the housings really). All just in time for the championships!
Only issues ive got now is the suspected ESC thermal protection breakdowns which i think are solved by removing all the tape from the motors and unwrapping the ESCs from the foam that they were wrapped in and a strange problem with my DX6i which i think is due to the mixing. For example, when your go full forward and full left hoping to stop the left hand motors and let the right hand motors bring the bot around, the reverse happens and the right hand stops, left hand carries on and ends up going right?! As i say, i think its due to the mixing im using which is the built-in elevon/aileron mix with the following set-up in the youtube video below to get full throws: . Any help with that would be great!
You shouldn't really have any problems running 18V GR02's at 22.2V, it's only a 24% increase, though of course you should take care to ensure the motors are well ventilated and aren't allowed to stall (which usually only happens in combat robots if a wheel locks or gearbox fails).
One thing people often forget is that if you start with with a motor designed for a higher voltage then the current draw will be lower which will help reduce the amount of heat produced - for example running an 18V motor at 27V (1.5 x voltage) should be less prone to thermal failure than a 12V motor run at 18V.
Another thing to add is that I've not yet had any gear or pin failures reported for the GR02's (famous last words..). A large number of these types of failure with drills seem to be related to how well (or poorly) the output shaft of the gearbox is supported, so do make sure external bearing are used for overhanging loads.
Will send a reply in a few minutes Dan!
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