axes in a small space (and weight)

hey guys, i am building a new 4wd feather, and i remembered how weaponless feathers are fowned upon by some peoples so i wanted to add a basic weapon. thought about doing a lifter but decided against it, i decided on an axe/hammer.
i want to mount the whole motor gearing and axe on the top of the bot so i can put a polycarbonte surround on bits that need it. im looking for a fairly cheap not to power hungry system for this to swing a 2kg axe. ideally it has to fit on a 25 by 40cm rectangle and be under 3kg.
the layout of my robot is like this but with another 2 motors the other side and another battery pack.

http://i947.photobucket.com/albums/a...uin/003-37.jpg
thanks very much

http://www.robowars.org/wikka/ElectricAxeWeapons

thanks, ill have a look in to that

How about using car fan motors instead of the scooter motor?

Also, what's the easiest system to build where you have a on/off switch which activates the system where an axe fires and returns in series without any other input?

micro switch check out my vid for it http://www.youtube.com/watch?v=cDLGGTpE7Cw

cool. thanks.

can car radiator fan motors be reversed?

yes

Anyone ever tried a friction drive axe?

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Originally Posted by Danjr1

Anyone ever tried a friction drive axe?

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Having used friction drive on a feather I'd say they do work but you'd be looking at a real prcision piece of engineering to make it work consistently and reliably.

Belt or chain drive would be far easier to achiev and probably more reliable. They would also be cheaper.

Andy

I'll look at gears instead. I'm looking to design something really compact.

After running a gear driven axe with a speed 900 , I can comment on a few things.

Mod 1 gears are to light on the last stage. They wear out in a few fights.
Speed 900 motors are expensive. And having to replace it after an event because crispy is to much of a good thing.

These mechanical issues will be adressed in the repairs/improvements in progress.

Return is done from the TX, after the stroke the motor is powerless untill commanded.

Microswitches and simular idea's are not needed, we use the same timing technology as we use in the Hannibalito's.
A command to fire the axe triggers a Ilyama custom (and expensive)build 100A+ Hbridge for a fraction of a second.

Been doing some maths on the concept of using the robowars tutorial but with the speed 900 replicas on eBay but at 22.2v. The ratio I've come to is 22.3 to 1! That can't be correct can it?!

It could be correct depending on your axe length, weight, and design. If it's heavy and long, then it could be right. If it's light and short, you'd get one heck of a powerful swing, just quite slow. Plus getting a 22:1 ratio into a small space may be difficult.

i think the issue is that the speed 900 replicas deliver their power at a much higher rpm than the scooter motor does so requires the higher ratio. the only thing that was different was the motor and i increased the length of the axe to 0.4m

Had a thought though.In my calculations I used 390 watts but if I use a 30a esc/switch/relay at 22.2v, that would be dumping 666 watts into the motor? Therefore meaning the ratio could be a lot lower?

Kashei used a 20.25/1 gearratio on a Speed 900 and a 300mm axehandle with 300 gram axehead.
6S 2P A123 Packs as powersource.

Result, Crispy Speed 900 after each 2 events. And that without anything going wrong.

I hope this answers the question.

Lol get the idea! No axes for me then!

Now we're redoing it with a gearratio of 30/1 and sturdier gears (mod 2 for the final stages)

That should end the crispy Speed 900's.