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Technically if you read the rules (section 7.8-lipos) there's no mention of the baseplate rule. It's currently an advisory, but I'd suggest a metal base plate will make it's way into the rules eventually.
An ignited lipo wouldn't have any trouble melting hdpe
Yup thought so, just checking so that if i do eventually go to Lipo i wont make any daft mistakes
The way Bitza is designed means all the expensive components are in a metal casing, and then mounted right in the middle of the robot a good distance from the floor, so shouldn't be a problem.
The drive motors are 12v Argos Drills, run by 15a Electonize's so can't draw too much current there.
As I don't know any specs about the 24v Drill motor we're using for the disk, I'm going to have to experiment! As I start I'm thinking a 10:1 reduction?
Given the bouts are each 3mins and as per your advise I'll be balancing them after each round I'm thinking 2,650mah upwards will suffice, hopefully......
Can't spend a huge amount, so I'll post what ever Li-Po I pick in the end, probs be a cheapy though!
As for wire what do you use David? I'm currently using stiff 10awg? And where do you get it?
i for one an cirtainly interested in how effective a drill motor will be for a disk.
if it is a half good weapon, it might be my next weapon. a spinner powered by a drill motor :lol:
Why is that so crazy?
Drill motors work fine. Used them in the featherweight typhoon bot and used two in the light weights. They won't give you the instant spin up from more powerful motors but will do the job.
Ratio out the gearbox you might wanna actually gear it up, the output from a standard drill gearbox is around the 800rpm mark, little bit slow in my book!
Good point Dave, I don't run my batteries until they're dead but there have been times that I haven't been able to charge them between battles so it's nice to know that I can run them again and still get a full fight from them.
My plan was to take take the gear box off the motor and then do a 10:1 reduction.
cool, only issue i could see you having with that is attaching something to the output shaft of the motor as they are tiny (only a few mm). You might as well look at getting a speed 900, decent power and a 6mm shaft. Not too expensive either.
For wire/connections I use silicon/wet noodle wire purchased from robotmarketplace.com I think robochallenge are also starting to stock wet noodle wire now though... Drop grant a pm.
Connectors I use deans connectors, there rated upto 70a contin, you can pick them up cheaply of eBay/robochallenge
As Gary said a speed 900 would be a good alternative... But if uve got a bit more weight spare you could go for a car fan motor. On 24v there really good. And better yet cheap of eBay/scrap yard :)
Would you say the car fan motor would be better than the 24v Drill motor? Car fan motor is pretty much in the Bitza spirit!
Id say so yeah, there quite powerful and high speed, I think some are around the 1hp mark. A lot of people who build spinners started of with car fan motor powered weapons :)
I've never used car fan motors but they'd be infinitely better than a drill motor.* If I remember correctly, some of them can chuck out close to 1hp (which, for comparison, is what a Bosch 750 produces). they've got nice thick shafts as well thus minimising the risks of bending from impacts.
*(NST uses a 24V drill motor but that's one of the good quality Dewalt drill motors that are far superior to run-of-the-mill drills)
EDIT: What Dave said :)
That's a really neat idea, I'll have to see if we an get hold of one....
This is a spin-up test of Tony Booth's robot DragonStrike, using a car fan motor from a Ford Mondeo. Cost him £5 out the scrappy:
http://www.youtube.com/watch?v=lV9oBPDI1so
Couldn't find any decent footage of DragonStrike fighting, but The Toonimator uses a similar setup and is very effective:
http://www.youtube.com/watch?v=dXzfHuTfibM
Just to give you an idea of what potential there is :)
Looks like we'll be making a trip to the scrappy then!
Just to confirm, are we talking about the motor that drives the engine cooling fan in most FWD cars or the motor that drives the cockpit air vents?
engine cooling motor
Cheers!
considering my 24v nimh pack has for some reason decided to die on me, I'm looking at lipo. what do people use for a voltage cut-off in the robot?
Damaging the writing of your nimh pack might have something to do with that. In that case I would think twice about moving to lipo considering the higher currents involved.
Anyway back to the question, most people don't. Just over size the pack and charge after every battle.
the wiring isn't damaged, was just a little flattened. and anyway, I'm pretty sure its a single cell causing all the issues (its discharging fine and linear but the recharging is erratic to say the least!) but when i look at the price of the single cell and the new soldering iron i would need, just makes sense to go to lipo.
Just wanna check a few things. Lipo's on it's way. I'm guessing u discharge first then balance cycle a few times? And at an event, can you top up the battery after a fight or do they need to be full discharged then recharged?
Don't bother discharging them. Lipos don't like being discharged like nicads and nimh. Just charge them up and the balancer should do it's job on the first charge.
You shouldn't ever need to cycle Li-Po's it won't do them much good either.
It's all finally arrived and as my luck with batteries and chargers isn't amazing I wanna run through a few things first.
1. Will the charge time be the same as previously with a NIMH battery, if everything is constant?
2. The charger has a storage function that seems to want to bring the battery to 3.7v per cell. I'm guessing this is my discharge function? As the discharge function wants to bring the battery to 18v overall?! And that's bad for lipos isn't it? I want to charge the battery up just to check it's all working but I don't want to leave it fully charged (or is that ok for lipos?)
3. Lipos should be stored at 3.7v per cell, correct?
Thanks
Dan
I've looked into the storage mode and it does charge/discharge the battery to 22.2v. I just need to know the very rough balance charge time (for the timer cut-off)Quote:
Originally Posted by Danjr1
thanks
I think storage mode is deigned for when you plan on actually storing you Li-Po, ie. not using it for a long time. What you want is balance mode, just keeps the amps low.
I'm currently charging in balance mode at 1.5A then ill leave it a while and storage discharge it to 22.2v, just wanna check everything is working but the new battery is a beautiful fit my bot!
Also, the difference between the lowest and the highest cell is 0.1v, that good or bad?
Why are you discharging? You should avoid doing that on Li-Po's, just charge until you have 4.2V per cell. They should all be 4.2v.
Try balance charging at 1a, or less.
not discharging yet. I've read that storing them at a full charged state isn't great so i was going to use the storage function which will discharge to 22.2v? i don't want to stop the charge now (but i wish id known! lol) but next time, ill balance charge at 1A
Just don't STORE at full charge then, charge them (fully), stick them in your bot, bash other bots around!
And then balance at a very low amperage as often as possible to keep them in good condition.
seriously, how long to these things take to charge/discharge?! I let it balance charge last night for 5 hours and it only got to 2800 out of 4800mah?! it went into this funny routine where one of the cells reached 4.2v and the overall charge amps started to jump from 0A up to 0.5A, rather than being at 1.5A (which i know isn't great). Its currently discharging to storage level at 0.2A (thats the max i can get out of it), at this rate, its going to take 14 hours to discharge the 2800mah!
proberbly not, it depends on how many amps the load is how long it will take to discharge.Quote:
Originally Posted by Danjr1
ie:
a 4000mAh batt wiv a 8000mAh load will take half an hour to fully disharge if fully charged
How many amps are you charging this batt at?
it was charging (on balance charge) at 1.5A (which i know isn't great but i didn't know) until one of the cells got to 4.2v. At this point, the Amperage started to basically bounce from 0A to 0.5A so the charging slowed right down! I can't make the discharge rate go any higher than 0.2A
What charger are you using?
an Imax B6 from ebay. not the most amazing one, any recommendations for a new one? Just had a rebate from the taxman!
try some of the the fusion range from logic r/c.
they are top quality
orr some of the more expensive ones £50+
ill have a look around. Out of interest, what discharge rates are other people getting on 22.2v Lipos?
Might treat myself to this:
http://www.giantcod.co.uk/a610-200w-bal ... 04525.html
I got one of those eBay iMax6's £8 couldn't resist!
STOP DISCHARGING!!!Quote:
Its currently discharging to storage level at 0.2A
Are you saying it's ok to store the battery at, say, 23.5v cos that's what it's at now? I'm not planning on using the battery for while until the robot is ready.
PJ, do you just charge your new lipos to full, use them in the robot and then charge them back up again?
Had a look around the Internet and bringing them down to 3.85v for storage seems to be the general consensus?