Team Thrifty /Fifty Build Diary for Bitza

[PJ-27]

Re: Team Thrifty /Fifty Build Diary for Bitza

Just trying to avoid adding more components.

Its seems such a odd feature, what use does it have?

[PJ-27]

Re: Team Thrifty /Fifty Build Diary for Bitza

I'm using a Sabertooth 2x12 and it seems to have some strange characteristics on the built in mixing. All straight movements on the stick seem to have half power, and all diagonal movement (so moving only one motor) seems to have twice the power.

Dimension Engineering said this was odd, and suggested that maybe my battery just couldn't supply the amps to turn both motors at full whack simultaneously.

I thought this too, but I'm using a 3S 20c 2650mah Li-Po which should be able to supply more than enough power.

Obviously this is causing me great problems since I lack torque to tank turn effectively and my straight line speed and acceleration is half what it could be.

Any ideas? (I'm using those MFA Como motors)

Cheers,

[Mouldy]

Re: Team Thrifty /Fifty Build Diary for Bitza

Try turning the mixing off on the esc.... Then throttle up so both channels are running flat out (move stick to top left or right position for example) then compare your results to running with the mixing on... If it's better I'd suggest a dodgy mixing function on the esc.

[PJ-27]

Re: Team Thrifty /Fifty Build Diary for Bitza

Good idea, I'll give it a try.

[Laser]

Re: Team Thrifty /Fifty Build Diary for Bitza

What radio gear are you using?

[PJ-27]

Re: Team Thrifty /Fifty Build Diary for Bitza

Spektrum DX5E Tx and one of the cheapy DSM2 Rx's from Giant Cod.

[Laser]

Re: Team Thrifty /Fifty Build Diary for Bitza

Are you using the mixing on the transmitter aswell?

[PJ-27]

Re: Team Thrifty /Fifty Build Diary for Bitza

No I'm not because it has those stupid half throws.

[PJ-27]

Re: Team Thrifty /Fifty Build Diary for Bitza

Sorted.

Apparently if you have Switch 6 not in R/C mode then this effects the mixing.

I had it in this mode because this is the only way I could get the drive to fail safe. Something else I can't seem to get to work.

If I am in R/C mode when I shut off the Tx the motors creep forward and no matter how I try and adjust the trims, set the sticks on start up, or re-bind I can't stop it from happening.

Furthermore the lost signal shutdown never comes into operation, which would have me believe it is a problem with the Rx. Except it can't be due to what I described above about not being in R/C mode.

*brain explodes*

[PJ-27]

Re: Team Thrifty /Fifty Build Diary for Bitza

Got a problem with Spinza where the blade is no longer able to spin up.

At first I thought the problem lay in the fact that because the Ti is so bendy in some position it was putting additional strain on the timing belt. After faffing around for a few hours adjusting the tightness of the belt for a few hours I found this made little difference.

I've re-assembled, greased and oiled the blade assembly and it now spins free-er than ever but still refuses to spin up. In a check we started the blade spinning with a long piece of wood (chocks away!) and it was perfectly able to then spin up.

It's like the motor has lost all of it's torque, so before I start swapping bits out and spending money just thought I'd get other opinions?

-

The pulley on the motor shaft also came loose before I could do much testing, and I managed to get oil on the main pulley so had some issues with belt slip!

[PJ-27]

Re: Team Thrifty /Fifty Build Diary for Bitza

More problems!

For what reasons could the Error light on Sabertooth come on? The manual says Thermal cut out or Over Current but neither of these are an issue.
I just re-wired the whole robot thinking it was some dodgy soldering causing a short but the light still stays on. Furthermore when the error first came about, if I wiggled the power wires going to the Sabertooth (before the re-wire) the light went off. And now after spending a few hours trying to sort the problem my Brushless ESC has started making error tones.

It's all quite bizarre. The voltage reading at the power distributor is 12.3v and I recently charged the battery. If I wiggle the throttle stick the Brushless ESC comes to life, but the motor barely turns (actually appears to shudder backwards and forwards). Really quite stumped so any ideas would be much appreciated.

Thanks,

PJ

[RogueTwoRobots]

Re: Team Thrifty /Fifty Build Diary for Bitza

That's odd, your robot's behaviour is the sort of thing you tend to see in the arena after it's worked perfectly well on the bench!

Sounds like there's a bug in there somewhere. Either an individual component messing everything else up or a horrible little beastie circulating within your wiring intent on causing merry hell.
Best option might be just to take everything out, whack it on the bench, and systematically start replacing each component until it works again. I'd be inclined to say that there's something up with the battery, as although it seems to be charging and holding voltage fine, your brushless setup is lacking power and your esc is glaring at you which, if you're using a built-in BEC and the voltage is low, could result in an error light. Perhaps a duff connection or cell? After that, I'd say it could be worth inspecting/swapping the radio gear. But other than that.....

[PJ-27]

Re: Team Thrifty /Fifty Build Diary for Bitza

I think your right.

My thoughts are:

Dodgy Battery
Dodgy Battery connector (the only one I didn't change!)
Dodgy Rx
BEC gone on Brushless ESC

I'll gradually work through these and see what fixes it! I'm hoping this will also solve the blade problems I was having.

[PJ-27]

Re: Team Thrifty /Fifty Build Diary for Bitza

Quick update:

The Battery Seems fine
The Battery connector seems fine
The Rx seems fine
I swapped the BEC's over so I'm now using the one on the Sabertooth. This seemed to solve the problems with the Sabertooth Error light and now that run's fine (except one motor is runnig faster than the other now, so it doesn't go straight, but I think that's a separate problem)
I still get error tones from the Brushless though, and the motor still doesn't spin (instead just shudders around).
I ran the brushless ESC and Motor by itself, same. I changed the channel controlling the throttle on the Tx and again got the same. The odd thing is, the error tone is for Throttle stick not in bottom position but it is. If I then move the throttle up and back down the error tones stop, but I still just get the shuddering.

My thinking is either the Brushless ESC has gone, or the Brushless Motor has gone. They've had minutes of spin time though and nothing arduous. Any tips on how I could determine whether the motor or ESC has gone?

[jonny]

Re: Team Thrifty /Fifty Build Diary for Bitza

have you checked the soldering from the burshless esc to the motor?