Rango - Build diary

[overkill]

Hi Ellis, I just became the postman for some TZ85 controllers. I am getting to the NEC a day early to get over the jet-lag, so we can arrange to meet as soon as you arrive if you want.

[Ellis]

Hey guys, proper updates soon, just finding I'm too knackered to write anything comprehensive at the end of the day! Jeroen's stuff has indeed arrived, I have made the motor mount plate, I have now got the entire mechanical side of the drive system installed and seemingly functioning well, save wheel spacers and tyres. Though buzzing the motors on low voltage or on speed control is making the electrical side get surprisingly warm after maybe just a minute of on the bench testing, namely the tz85s. It's all relatively smooth running now, the right angles run nicely, but the oilon bushes are creating quite a bit if friction on the (now uber polished) wheel shafts. Some grease has helped. It's entirely because of the drive belts putting big stress on the wheels. It does work, but I worry for the speedos. Angry driving for 3 minutes, and if this amp draw keeps up (must be pretty high for no load to make them even remotely warm?!), I would expect them to leak magic smoke before long.

I can only hope that the HTD belts will give a tiny bit. If they do it should be okay. Going to be a matter of doing actual drive testing in short bursts and hoping that slackens everything up some. If it doesn't... eek.

Does anyone know if HTD belts even do stretch? I am 95% sure they already have a bit, suggesting they might some more.

@Max: I'll get back to you.

@Nick: yes, thank you! We'll be there on Wednesday too so that will hopefully work out nicely. Thank you for playing postman.

Tomorrow I'm hoping the package from Mario will arrive along with Guilherme's spare weapon motor. Soooo much left to do!

Going to bed, cheers.

[knightrous]

Three BotBitz 85A V2 ESC's and Programmer box are on their way to Nick's

[Eventorizon]

What does one have to do to get some more TZ85's on their way over to England? And a programming box sounds useful too.

Ellis: I have found every belt I have ever yused has stretched though the HTD belts have stretched less than the cheaper ones. You could try just running Rango with her wheels off the floor for 10 minutes or something to run the belts in and try and give them a bit of a stretch to relieve some tension.

[overkill]

Sorry, its too late for me to bring them over - they couldn't be mailed until Monday and wouldn't get to me in time. You can still order them direct from the Botbitz store: http://www.botbitz.com/index.php?rou...tegory&path=59

[Ellis]

Yeah it's going to be a matter of just running them in. I hope. I'm surprised they even get warm, they had a drill motor stalling with the other nearly dead in T2 probably about ten times in its lifetime, never above room temperature. This must be something anyone running belt drive must suffer?

Also, Nick, just to confirm, you mean it's too late for more to be sent, right? Lol, just, just checking...

[overkill]

Thats right about the TZ85s; Aaron express posted them today and as long as they arrive early on Tuesday I can pack them. Anything posted after that has little chance of making it.

The belts really shouldn't get very hot - the few times I have used timing belts, they got mildly warm at most. I recall a US builder had this problem and solved it by boring out the bronze bearings he was using by a small amount to allow the axles to pull closer together - he seemed happy with the results.

[Ellis]

Sorry, I wasn't very clear, by "they" I meant the speedos! The belts don't seem to care either way, the issue is their tension is putting load on the (already bored out as big as I'd like, i.e., quite loose) wheel bushings and the friction from that is putting strain on the ESCs.

[overkill]

DOH! Mah comprehunshion lurvels are low today

Its unusual for a TZ85 to get more than warm during testing - is anything else getting hot from friction?

[Ellis]

Nope, not that I can tell. I can't run it for more than 10-15 seconds, though, as the wheel bushes keep popping out, making those spacers right now and I'll report back later.

[PJ-27]

What motors are you using? They're not anything anyone has used before? Could be putting undue strain on the ESCs.

We found the fan motors in Splinter were too much for the TZs, even though our amp draw wasn't massive thanks to (and this part I don't fully understand) the motors having a very low inductance it meant the current spikes were very large.

My point is, types of motor could be giving you issues beyond their nominal current draw.

[Eventorizon]

They are torpedo 800's I believe, similar to the Speed 900's but smaller. Since a S900 max'd out at 40A they should be well within the capacity of an 85A ESC but something could be a miss elsewhere.

[Revsmin]

Johnson 885s, should be more than comfortable on a TZ85.

[overkill]

I doubt its due to the type of motor; Steve @ Botbitz has used them in a heavyweight with large winch motors. The 885 motors should have typical inductance - the low inductance motors usually have no iron laminations in their armature and outside of those pancake motors used on car fans, they are really rare.

One good test is to run the motors out of the bot and maybe without the shaft support. Also try them on a different motor. If the TZ85s still get hot, contact Botbitz.

[Ellis]

The motors run nicely without anything attached etc. Same when installed in the right-angle first stage reduction, no noticeable delay in startup. But the wheel bushing material I used, and it was an experiment from the beginning, is pants. Oilon is a nono, it'd seem. I still have basically everything to do, in four days.

There is no immediate way to solve the bushing issue. No quickly made bearing-based replacement and I don't have regular nylon rod in stock to try. So, to slacken the belts, I have bored the bushes out hugely, talking 1mm or more. It really really sucks after all this work and wanting the machine to run true and be smooth. Point is, though, it now functions; motors aren't straining. The wheels are very loose. If I had the time I'd remake the bushes out of proper nylon and get it sweet but it ain't happening... I'll be redesigning this for sure.

So now it's just tyres on the wheels before a test drive, but I really need to do anything else or I won't finish.