Reliable High Discharge Lipos

[ewan]

Re: Reliable High Discharge Lipos

There's some variables which you're unlikely to know with too much accuracy: the coefficient of friction of the tyres (which will be different on different surfaces) which obviously effects the point of wheel-spin, and also the inefficiencies in the drive-train (friction, heat etc.) which will add to power consumed when reaching wheel-spin. As far as your battery is concerned you only need to rate peak current at a little over the wheel-spin condition, the 'possible 133A' you mention is surely the stall condition (?) which you shouldn't be aiming to reach, the closer you get to it the more power you'll be expending as heat rather than movement.

[Eventorizon]

Re: Reliable High Discharge Lipos

is there any real point in such powerful motors if I cant get the power down or can you put slick tyres on and the like to give more traction

[Max]

Re: Reliable High Discharge Lipos

You could use tracks, depending on how you do it that could increase the friction giving you lots of power. But on my tracked bot the tracks slip on the ground rather than the motors stalling so still not enough friction on my design but that's partly due to the fact the bike tire I used wasn't very grippy and the lack of a wheel in the middle and suitable tensioning means in the middle of the track not much weight holds it on the floor.

[ewan]

Re: Reliable High Discharge Lipos

The obvious thing you can do to boost traction is to increase the contact surface area by both changing the tyre material and wheel count. Think how Storm II is a 6WD machine with custom tyres specifically designed for the arena environment- specifically for this reason.
Although using a softer rubber compound generally helps, it's worth bearing in mind it can become 'gummed up' with dust and debris from the arena or just wear down too rapidly to be of any use. The orange banebots compound seem like a good compromise between wear resistance and traction from my experience, they're a little softer than the Robochallenge 'Blue' wheels but are not as wear prone as the (incredibly soft) green versions.
Other than that if you're aiming specifically for the Robochallenge arena magnets ought to be worth considering, though they bring their own complexities.

[Eventorizon]

Re: Reliable High Discharge Lipos & other things now...

I was going to use 8 of the green banebots wheels, but I know 30S is very soft, I had considered tracks but I know of now way to make featherweight tracks. it seems now that its not a question of power but a question of traction so now I just have to figure out how to maximise traction!

MORE WHEELS!!!

[typhoon_driver]

Re: Reliable High Discharge Lipos

A lipo with a 100A discharge will be more than enough for a rammer

[blazerbotics]

Re: Reliable High Discharge Lipos

What speedo are you planning on using, seeing as most heavyweight controllers are current limited to about 120amps per side?

[Eventorizon]

Re: Reliable High Discharge Lipos

Victor 885's, but given I will only be able to use 30A before the wheels spin I am going to need to rework the design to make using that much power worth while. I am certain we can do it and use all that the motors have to offer its just figuring out how. I can see myself doing some tests when I get back to uni on what grips best to Hardox 800.

It seems now that power is not the issue but just fundimental grip. Thanks for your input guys, it never crossed my mind that I would not be able to put the power down. I am going to have to design the Bughatti Veyron of robots to make use of all that grunt!

[ewan]

Re: Reliable High Discharge Lipos

Take cues from Dave's 540 and go for magnets with 6WD- that's probably the best set-up for mechanical grip that's realistic for a feather.
Also if you're going for the 'Bughatti Veyron' of drivetrains then look into sensored brushless motors & speedos for drive- can't get much better than them these days & they're now pretty affordable, worth a browse on Hobbyking.

[Eventorizon]

Re: Reliable High Discharge Lipos

I have read nothing but bad reviews about hobby king and rubbish customer service... yet some people seem to have no issues which is strange, its one extreme or the other...

With the Cellite and Ti to make the chassis it is probably possible to make a seriously grippy and torquey robot cos you can devote much more weight to the drive train! I will just have to be careful I don't go up in a cloud of smoke like 540 every other fight, never understood why that happened.

[maddox10]

Re: Reliable High Discharge Lipos

I have to admit I don't have any complaints about hobbyking.
Especialy not if you take care of ordering from the German warehouse.
Also, ordering out of stock stuff won't help a lot.

And of course, you get what you pay for.
If you buy a £10 100 gram brushless with a 3.2mm shaft and a max power of 3S 100A to power your spinner you can expect broken axles.

[PJ-27]

Re: Reliable High Discharge Lipos

For everyone that just did what I did:

http://www.teamnovak.com/tech_info/brus ... rless.html

540 on paper and is an awesome machine with a serious amount of power. But that was it's undoing. With that much power there's always a weak link, and when you're fighting that will always be exploited.

Read this the other day and it confirmed what I've always said.

Fights are won in the arena, but the Battle is won in the pits

Your machine can be awesomely destructive, but if you can't last the weekend then you aren't winning the championship. Just look at how well BitzaMk1 did, and that had the side of a dish washer for a front!

[Eventorizon]

Re: Reliable High Discharge Lipos

LOL the first thing you get in google when you type in sensored brushless

Was it 540's motors that kept burning out? It was superbly engineered, I don't know if we can get close to that in terms of mechanical accuracy, all our wheels will probably be out of alignment. (But hey, so were Conkers and that didn't really matter)

Like I said before its just another idea, but it would be a fun robot to drive and Tornado was always a crowd favorite, so hopefully it will be fun to watch to!

[grant_ploughbot]

Re: Reliable High Discharge Lipos

540 burnt his motor's out as the magnet was just too much, and geared too fast for the size of the motor. It's fine going off that chart that tells you 30A is fine, but thats not realistic for for more than just driving around.
As soon as you slamming forwards and back, that burst current will shoot right up. Also when you underneath someone with their extra weight giving more grip will shoot that current rating up. 540 needed LOADS of power to stop and change direction due to all the grip, and the motor's just couldn't take it.

If your running without magnets there's not much to worry about on this front - get a decent lipo such as OptiPower of the new thunder power 65C packs (pretty pricey these though) and work from there. With all that power your more likely that the motor's can't hack it rather than the rest of the system if they're particularly small in size.

[Eventorizon]

Re: Reliable High Discharge Lipos & other things now...

So am I right in saying that to avoid the same issues that 540 had I would need to fit larger motors and then gear them down further OR use 1 motor per wheel as I do atm with conker. Both of these would ensure that I had more power to deal with the increased grip.

What motors did 540 use then I know that I need to go up from there or change the ratio, that thing was seriously fast so reigning in the speed would probably help