The Hotel Lima, for Ants: A Build Diary

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LimaHotel
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Location: W. Devon

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 (Rear-hinged Flipper, currently out of service)

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MarkR
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Location: Reading Hackspace
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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.
Robot: Betsie - RaspberryPi controlled flipper bot with gyro stablisation - too clever for her own good?

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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 (Rear-hinged Flipper, currently out of service)

Kyro
Posts: 156
Joined: Fri Jan 18, 2019 12:36 am

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 (2wd control bot)
Dominus (4wd flipper)
Twinzer (L&K) (cluster)
Remembering Rex (antweight cassuis)

Sometimes, i wake up grumpy... other times i just let her sleep in...

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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 (Rear-hinged Flipper, currently out of service)

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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.
Robot: Betsie - RaspberryPi controlled flipper bot with gyro stablisation - too clever for her own good?

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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 (Rear-hinged Flipper, currently out of service)

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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!
Team Zero
Zero - rambot - - Axiom - axebot - - Valkyrie - drum spinner
Vampire - horizontal spinner - - RBMK - quad 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 » 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 (Rear-hinged Flipper, currently out of service)

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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 (Rear-hinged Flipper, currently out of service)

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

Post by Kyro » Sun Apr 28, 2019 1:33 pm

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
Team Rocket Robotics
Esper(4wd flipper)
Mantis (2wd control bot)
Dominus (4wd flipper)
Twinzer (L&K) (cluster)
Remembering Rex (antweight cassuis)

Sometimes, i wake up grumpy... other times i just let her sleep in...

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

Post by GeorgeR » Sun Apr 28, 2019 4:23 pm

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
Zero - rambot - - Axiom - axebot - - Valkyrie - drum spinner
Vampire - horizontal spinner - - RBMK - quad 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 » Sun Apr 28, 2019 8:17 pm

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

Key Grip (Rear-hinged Flipper, currently out of service)

Kyro
Posts: 156
Joined: Fri Jan 18, 2019 12:36 am

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

Post by Kyro » Sun Apr 28, 2019 9:09 pm

key flip...
Team Rocket Robotics
Esper(4wd flipper)
Mantis (2wd control bot)
Dominus (4wd flipper)
Twinzer (L&K) (cluster)
Remembering Rex (antweight cassuis)

Sometimes, i wake up grumpy... other times i just let her sleep in...

Kyro
Posts: 156
Joined: Fri Jan 18, 2019 12:36 am

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

Post by Kyro » Sun Apr 28, 2019 9:23 pm

antmobille...

it has a look of the old batmobille to it with the wings
Team Rocket Robotics
Esper(4wd flipper)
Mantis (2wd control bot)
Dominus (4wd flipper)
Twinzer (L&K) (cluster)
Remembering Rex (antweight cassuis)

Sometimes, i wake up grumpy... other times i just let her sleep in...

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