Torque required for hammer to self right?

[daveimi]

Hi, quick question. To build an electric axe capable of self righting what sort of size of motor would I need to look at to power it?

[Ellis]

Re: Torque required for hammer to self right?

Depends on the gearing! A scooter motor will have the beans at a high ratio, but a standard drill size 550 motor will too at a low enough ratio.

Can you give any idea what sort of motor you had in mind?

[maddox10]

Re: Torque required for hammer to self right?

Speed 900, 6S, 30-1 gearratio, 300mm long arm. Does the job very aggressively.

[daveimi]

Re: Torque required for hammer to self right?

Erm, my fav robots are Little Hitter, Tiny Toon (not relevent lol), b-e-t-a, basher

I have a nearly finished robot at circa 6kg. Was umming and arring about building another for a cluster or armour this more and going with a big hammer, although then it won't be invertable.

So was looking into it and most are pneumatic, but would rather go electric and wanted to see if I'd be able to sort out a big enough motor with a 6kg allowance. To be honest I don't know what ratio to be looking at, I think it'd depend on the motor. I'd hoped it would be manageable with something like a pair of wiper motors etc. But if it needed something like a wheelchair motor in I'd never do it in the weight I don't think.

[daveimi]

Re: Torque required for hammer to self right?

Sorry, forgot to say,

So I was just looking for an indication of the power it needs in the first place to self right if i move towards a better more rounded shape etc.

[maddox10]

Re: Torque required for hammer to self right?

If you want to build a 6 kg machine, you should have a look at the German Raptor rules.

But to make the search shorter.
No brushless ,no brushed larger than speed 700 size and no rare earth magnet motors allowed.
12V SLA, 10S NiMH, 3S LiPo or 4S LiFePo4 batteries.
Voltage boosters or extra batteries allowed for valve control.

The rest is classic featherweight rules.

[daveimi]

Re: Torque required for hammer to self right?

I didn't deliberately end up with a 6kg robot, its just the way it's ended up, hence either building a second as a cluster or trying to build a hammer to go on top. Sorting the hammer won't be that bad, I'm just not sure of the size of motor and torque that I'll need to be able to self right.

[Daniel]

Re: Torque required for hammer to self right?

Avenger has a 300W scooter motor on 22.2V, a 80:11 reduction and a 300mm axe and it manages to get a bit of air while self righting. A quick guesstimation while looking at the motor power graph (chinese, so don't trust it) and guessing the rpm, I'd say it gets 30Nm at the axe. Can't decided if that's too high or low, so I guess its close.

[daveimi]

Re: Torque required for hammer to self right?

Do you mean a scooter as in an electric wheel chair type of thing? Do you have any pictures of Avenger?

[maddox10]

Re: Torque required for hammer to self right?

The motor Daniel mentions is a large, heavy motor, on the edge of usability of feathers. Also called EV warrior.

Most we see now are Chinese clones.

I do happen to have one in my spare box.

[Daniel]

Re: Torque required for hammer to self right?

The most recent pictures I have are on this page http://www.robowars.org/forum/viewto...=asc&start=435 Videos from its fights at our Nationals are on youtube too.
1.5kg for a motor is a bit heavy, but I find the lower rpm makes up for needing extra reduction. But I've broken all my scooter motors at our last national championships and have now discovered that my local supplier has put his prices up. So I'm currently redesigning my two scooter motor powered robots to use HK brushless motors instead

[maddox10]

Re: Torque required for hammer to self right?

Funny Daniel, that is exactly the motor I have in my spares box.

[daveimi]

Re: Torque required for hammer to self right?

So something like a pair of Gimson GR02's wouldn't give enough of a kick to throw it back over?

[shakesc]

Re: Torque required for hammer to self right?

So its all in the gearing (I suspect)

So I toyed with one of thoe scooter motors and have one in my spares box

Instead I went the 2 GR01 route
Been busy at work but plan to weapon test over Christmas

[typhoon_driver]

Re: Torque required for hammer to self right?

Well why not do the sums and work out what will be able to self right?

Lets assume a 30cm long axe with worst case the majority (say 10kg) at the axe head end of the robot. Torque is simply distance x force so that would be 0.3m x 10*9.8 (to get the mass into newtons) = 29.4Nm. Call it 30 to keep the numbers simple.

Now looking at the gimson GR02 18v. That will give you 1.41Nm at peak efficiency. So in theory you would need a ratio of 21:1 to get a flip back over.

Now of course I have assumed that all the 10kg mass is on one side of the axe mechanism and is only balance by very little mass on the other side. So what I would do is roughly work out the mass distribution of your machine and then work out the imbalance that the axe mechanism has to self right. You will probably come out with a figure somewhere between 5:1 and 10:1.

I would always advise doing the sums and work out what you will need adding a little bit more for the real world rather than going down the route of yeah that should work, spending the cash and time on it then realizing it doesn't.