The Hotel Lima, for Ants: A Build Diary

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

Post by LimaHotel » Tue Apr 09, 2019 3:33 pm

Hahaha it is gone now :D
... Shell... The Lipo...
*KABOOM*
Ye. I'm probably being paranoid, but the idea of removing anything from the battery itself scares me :/
Besides, how much do you actually save by shelling a lipo?
Jiggy Sawdust (Grabber)
Jammin' Good with Weird and Flippy (Rear-hinged Flipper)
The Pushbot from Mars (4wd Pushbot)

Key Grip (Retired)

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

Post by MarkR » Tue Apr 09, 2019 4:21 pm

I wasn't suggesting removing the protective film from the pack, just the warning label on the lead :)

I did peel the labels off one of my packs because I was trying to fit it into a very slim space (actually rather stupidly, I bought larger packs than necessary, 300mAh). But not the film or anything else.

I did consider modifying the pack into a flat form factor (from the "brick" 300mah 2S) but that seemed a little risky.
Robots: Betsie - RaspberryPi controlled flipper bot with gyro stablisation - too clever for her own good?
Stacie - tidy flipper; 4wd driven by hair bands

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

Post by LimaHotel » Wed Apr 24, 2019 8:51 pm

Sparks fly from the dremel as I grab some (probably rubbish) steel off an old computer table, and the room stinks of solder as I finish the brain for Key mk 2. I'm also gonna put Key's Key on a diet - there's a lot of metal there that could be lost. Hoping to be driving Key the Second within the next few days, and the bustophedons I want for Pushbot should arrive this Friday (theoretically). Wheels... Grrrr. I'm sure that order's been lost - marked as leaving country of origin over a month ago, nothing since. I'm trying to get access to the 3d printers at the secondary school I volunteer at to print off some hubs for Lego tyres though, and I might print some rims & molds too. Hoping to have things ready for the 5th, for that little back garden event Kyro advertised. It's a long way for something so small for sure, but totally worth it as an excuse to visit friends in the area!
At least Jiggy is ready though!
(I say that - he has a Problem whereby the m3 bolts that hold the grabber in place unscrew. Loosening is fine - the bolts are long enough that the nuts can't actually come off - there isn't room. So my thoughts on fixing it are blob of Gluegun over the back of each m3 so they can't slide outwards. Which isn't ideal. Really, some nylock m3 bolts would be good - except I don't know if they come narrow enough to fit in the gap available. Maybe I should just soak the whole thing in loctite?)
Last edited by LimaHotel on Wed May 01, 2019 10:08 pm, edited 1 time in total.
Jiggy Sawdust (Grabber)
Jammin' Good with Weird and Flippy (Rear-hinged Flipper)
The Pushbot from Mars (4wd Pushbot)

Key Grip (Retired)

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

Post by Kyro » Thu Apr 25, 2019 5:29 pm

i will probably have some wheels you can have.

ordered some "pololu 32mm" wheels from ebay but what came were the fake 34mm pololu copies...

they dont have the best grip in the world but they have done me pretty well at antfreeze and aws...

if they dont want me to send them back you can have some... if they do, your welcome to some slightly used ones after i get some real pololu's

they are good enough to use but real pololu's are better
Team Rocket Robotics
Esper(4wd flipper)
Mantis (4wd grab 'n' lift)
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Remembering Rex (antweight cassius)

life is like toilet paper, either you're on a roll, or taking sh*t from some ars*hole...

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

Post by LimaHotel » Fri Apr 26, 2019 8:08 am

Just did a test drive of Key Grip's chassis to make sure I hadn't shorted anything cramming it all in, and after about 20 seconds of driving FLASH SMOKE
I had my first Lipo fire! :D
In seriousness though, that wasn't great. Turning it off stopped the fire, but there was spark and smoke and bright coming from inside the lipo. I'd upload a picture of a torched lipo, except it looks totally fine? I'm almost tempted to take it outside and deliberately short it so it can finish incinerating itself.
I won't, but the temptation is there.
Okay. How do I safely dispose of a popped lipo?
Jiggy Sawdust (Grabber)
Jammin' Good with Weird and Flippy (Rear-hinged Flipper)
The Pushbot from Mars (4wd Pushbot)

Key Grip (Retired)

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

Post by MarkR » Fri Apr 26, 2019 9:01 am

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.
Robots: Betsie - RaspberryPi controlled flipper bot with gyro stablisation - too clever for her own good?
Stacie - tidy flipper; 4wd driven by hair bands

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

Post by LimaHotel » Fri Apr 26, 2019 10:39 am

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.
Jiggy Sawdust (Grabber)
Jammin' Good with Weird and Flippy (Rear-hinged Flipper)
The Pushbot from Mars (4wd Pushbot)

Key Grip (Retired)

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

Post by GeorgeR » Fri Apr 26, 2019 12:30 pm

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 » Fri Apr 26, 2019 12:46 pm

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*
Jiggy Sawdust (Grabber)
Jammin' Good with Weird and Flippy (Rear-hinged Flipper)
The Pushbot from Mars (4wd Pushbot)

Key Grip (Retired)

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

Post by LimaHotel » Sun Apr 28, 2019 12:27 pm

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*
Jiggy Sawdust (Grabber)
Jammin' Good with Weird and Flippy (Rear-hinged Flipper)
The Pushbot from Mars (4wd Pushbot)

Key Grip (Retired)

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