New featherweight (DMBLBIT)

[Niels - Team K.a.L.M.]

From what I know there isn't. Only antweights and heavyweights are restricted within their dimensions

[psychostorm]

There is a size limit. to featherweights - it's the doorway...

[RogueTwoRobots]

Ah the good old days of wheels falling off. Used to happen to me all the time on my old wiper motor bot, and for the first wee while when I transitioned to drills. I kinda miss it; damn improved building techniques!

[JamesDavies]

any tips on keeping them on then?

[RogueTwoRobots]

Grub screws, circlips, collars/collets, nuts - whatever best suits the design and how the wheel is mounted etc

[Flag Captured]

You might want to try adding a layer of armour to the outside as well as an outer bearing along with that - I think that might be very handy for this kind of design, and definitely will reduce the stress on the wheel axles I'd imagine. Would also help keep them on too!

[JamesDavies]

Wheels sorted. Made it into a thwak bot for now (10kg before i added that).

Planning on making a range of (boring) weapons to be bolted on the front including a practical scoop. Not sure I can fit anything active into 3 kg.....

[JamesDavies]

IMG_20140905_110749.jpg

Got problems charging. Using an Imax b6ac charger and a turnigy 3000mah 22.2v (6s) lipo.

Error message reads "low voltage".

Battery voltage is 14v on my multimeter. I'm worried I might have knackered some cells in there...

Obviously I now won't use it until I know what's going on. I'd it something stupid I'm doing wrong or is the battery done?

James.

[overkill]

As long as none of the cells have completely died, its possible to recover the battery by giving it a partial charge to bring the voltage up to a point where the Lipo charging program recognises the pack as having 6 cells. The best thing to use is a current limited bench power supply but as they are rare, you can use the Imax charger in it's Pb (lead-acid) mode.

* Set the charger to an 18V Pb battery and low charging current, 0.5A or less. Don't connect the balancing cable at this point. The charger should accept the pack as a

* When the charge current drops down to almost nothing or the charger finishes its cycle, the battery should be charged up to around 18V.

* Disconnect the battery and check the voltage. Wait around 15 minutes and check again; if the voltage is the same or only a little lower, the pack is savable, if the voltage is heading back to 14V, its dead.

* Assuming the pack holds its voltage, set the charger for a 24V PB battery and start charging again. You don't want to complete this charge cycle, you just need to raise the battery voltage to around 20V so that the lipo program recognises the pack. Charge for 15 minutes, check the battery voltage and repeat until the pack holds around 20 to 21V.

* Set the charger to the Lipo mode, connect the balance cable, set the current down low and try charging. If the charger still indicates low voltage, try more time on the Pb charge mode. If the charger accepts the pack, monitor the individual cells by pressing the DEC button (described on page 30 of the manual). If any of the cells are wildly different voltages, you probably need to switch over to balance charging.

To stay safe, do all this outside on a non-flammable surface. I have brought back several packs this way and while they may have balancing problems or a shorter life span, its worth trying.

[Ellis]

If it's reading 14v it's severely discharged. Works out to 2.3v/cell assuming they're discharged evenly, which is a good way beyond what they should be. A high end charger might be able to resurrect it. Have you tried Charge or Storage instead of Balance? The Imax might happen to be okay with the lowlow voltage in other modes. It's very possible the pack is permanently damaged and trying to force charge into it could be dangerous, so I would put it outside and keep a very close eye if it does accept it. It might also be wildly unbalanced so only charge to say 3v per cell and then switch to balance.

Not very recommended but you might save it. Looks like overdischarge, easy enough to do but you won't do it again. :P

I'd suggest getting a LiPo alarm/voltage reader for a couple quid from Hobbyking. Allows you to stay on top of the voltage and stay above unsafe.