The Hotel Lima, for Ants: A Build Diary

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MarkR
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Re: A Hotel, constructed of Limas, for Ants: A Build Diary

Post by MarkR »

It's easy to preach after the fact...

I usually test my electronics with a multimeter (for short circuit) bench supply (for functionality) before plugging a lipo in. The Lipos give enough current to pop the magic smoke out of any faulty electronics.

That said, I've never had the lipo itself catch fire, only the dodgy circuits.

I saw a reference linked somewhere on this forum that suggested to fully discharge and put in a bucket of salty water overnight.

Lipos don't contain anything super toxic like mercury or cadmium, so they should be safer than e.g. coin cells to put in the waste, if fully discharged. I guess a lipo which has already burned probably isn't going to start any new fires.
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LimaHotel
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Re: A Hotel, constructed of Limas, for Ants: A Build Diary

Post by LimaHotel »

It had passed all the tests before being crammed into a robot shell, and I don't possess a bench supply, so it was lipo time!
I'm pretty sure that lipo was toast before I'd plugged it in. I think it'd been horribly over discharged, and whilst it survived recharging it didn't survive use.
All the electronics are fine btw - plugged a freshly charged lipo in and it seems happy as anything.
It was so weird though seeing it pop! Initially I thought the right motor had managed to short some dog hair or something and set it alight, especially given that the robot still drove happily. I picked it up and tried blowing the fire out, nothing. Then I realised the flame was coming from in the Lipo, flicked the switch off, and it stopped burning instantly. It did still smoke for a bit though.
A grabber? I CHALLENGE IT WITH JIGGY!
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GeorgeR
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Re: A Hotel, constructed of Limas, for Ants: A Build Diary

Post by GeorgeR »

As Mark suggested, unlike most batteries they don't contain anything toxic, so the way to dispose of a dodgy lipo is to fully discharge it, and then simply put it in the bin.
Leaving the lipo in a bucket of salt water for a couple of days is a good method of discharging as it should contain any fires if it were to reignite.

The way the fire happened, and the fact switching the robot off stopped it suggests you may have had a short somewhere, I would definitely triple check the wiring again.

And a final reminder for everyone, be careful with your lipos!
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LimaHotel
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Re: A Hotel, constructed of Limas, for Ants: A Build Diary

Post by LimaHotel »

Found the short
The servo signal wire was shorting against the N20's gearbox. Fortunately this time all I got were a few sparks and a little bit of melted insulation - this fresh, happy lipo didn't seem to mind.
Right. Time to cover someone in gluegun. *Stares at servo signal wire*
A grabber? I CHALLENGE IT WITH JIGGY!
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LimaHotel
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Re: A Hotel, constructed of Limas, for Ants: A Build Diary

Post by LimaHotel »

So as I near competion of my new flipper (I'm not sure this is a key grip rebuild after all - it's very different. Too different.), I've noticed the pink servo gets hot. I mean VERY hot. Like "ouch I touched it" hot. Is... Is this normal? It didn't in the old key grip, but then it was running off the lemon / dasmikro bec instead of full battery power.
As to finishing this flipper, I need to lose 2 grams. I've drilled a LOT of holes. Where else can I save weight? *tears at hair in frustration*
A grabber? I CHALLENGE IT WITH JIGGY!
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Kyro
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Re: A Hotel, constructed of Limas, for Ants: A Build Diary

Post by Kyro »

cutting corners... liturally...
rounding off both corners and actual edges.
casing the battery.
now you know where electronics will sit, shortening wires to only what you need.
removing the remaining polycarb in the middle of some holes in an area where strength is not as important (can fill hole with coke bottle plastic if need be)
cutting/grinding any hardware down so its the perfect length for everything it goes through and no more


a few of these wont make a huge difference, but they do all add up... i would focus on wiring as you will be surprised just how much you can save by losing a few cm off of every wire... if you still need more, work from that down to cutting bigger areas of polycarb and replacing with coke plastic (i personally will try and save weight from anywhere but leaving armour until last)

hopefully this will help
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GeorgeR
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Re: A Hotel, constructed of Limas, for Ants: A Build Diary

Post by GeorgeR »

Regarding the overheating servo, it probably can't move through its full range of motion due to the linkage. So at one end of its travel the servo is constantly stalled, which will quickly heat it up. The solution is to program the servo end points on the transmitter.
Team Zero - AWS 58 Champion!
Zero - rambot - - Axiom - axebot - - Valkyrie - drum spinner
Blueprint - rambot - - Vampire - horizontal spinner - - Particle - ???
RBMK - quad spinner gyro walker - - Duality - dual spinner gyro walker
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LimaHotel
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Re: A Hotel, constructed of Limas, for Ants: A Build Diary

Post by LimaHotel »

Yeah, you're half-right. It still has full motion and isn't completely stalled, but to reach full-down on the flipper arm it is slightly stressed against the chassis. It looks like one of my polycarb bends isn't too neat and is fighting the servo. I'm gonna see if I can fix it

I've also trimmed all the wires as much as possible. I haven't trimmed all my m3 bolts - that might be enough you know. I could also use a less overkill material than 1.5mm aluminium for the wings.
Name wise, I'm thinking something in keeping with Jiggy Sawdust. Other song names from the album...
Suffragette Flippy? :-?
Maybe not that one.

So, with the stalling servo fixed, here it is!
Image
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Kyro
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Re: A Hotel, constructed of Limas, for Ants: A Build Diary

Post by Kyro »

key flip...
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Kyro
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Re: A Hotel, constructed of Limas, for Ants: A Build Diary

Post by Kyro »

antmobille...

it has a look of the old batmobille to it with the wings
Team Rocket
Trappist 1(4wd grab 'n' lift)
Ton 618 (4wd expanding bot)
Io(4wd flipper)
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