Picking your brains.

Hi all,

I've recently re-immersed myself in all things robot combat after several years and I've decided I want to build a featherweight. My favorite robot when Robot wars was on TV was Killertron and I'd like to build a machine loosely based around the same design but perhaps with 2 wheels rather than 6, a lower ground clearance, an axe capable of righting the machine and most importantly a different colour.

After looking at a few threads on this forum I have a few ideas of how to do things and I've spotted a design for an axe using a 300w electric scooter motor that looks pretty awesome.

Here are a few questions that I have though:

If I were to use Magnum 775 gear-motors for the drive and a scooter motor for the axe, what batteries would be best?

What ways are there to control the axe without using a servo linkage? I don't really want to use a speed controller either.

Is lime green any better than pink?


Charlie.

Welcome to the world of robotics Charlie :)

I can't really comment on the batteries, I can however advise on the axe controlling...if you don't want a speed controller the best way would be to use something like a Team Delta dual ended R/C switch, wired to switch two bigger relays that actually switched the axe motor (I suspect a 300w scooter motor draws a bit more than 12A at stall) and use microswitches wired to the R/C switch to turn off the axe at each end of its travel to stop the mechanism wrecking itself. Agent Orange used something a bit like that I believe, only with more servos and bodging, and it'd be fairly cheap as well (the RC switch would be the most expensive bit, about £30 with shipping, the rest could be picked up from Maplins or similar for fairly little)

As for colour, personally I favour flourescent yellow for when you just can't use subtle shades :proud:

hi i'm new here so dont ask me much!

I'm not familiar with the drive motors, could you give a link with their specification?

http://www.robotpower.com/products/magnum775_info.html

I was thinking about using those motors too, but since I had let slip the whole drill motor thing to my dad, he favoured the cheaper, not as good option :x

Sorry that was totally off-topic, I just felt like a rant on my dad, lol.

hey,
this isn't really a related responce to your thread lol, but my dads the same when ever i buy robot parts i've got a general rule where i always say it cost half the price of what it actually cost.

its alright for him to waste large amounts of money going to watch men kick footballs around a large grassy area, but its frowned upon when i buy expensive robot stuff.

My parents don't ask anymore.

Ok batteries, you have a number of options.

- SLAs - very old school. You would be looking to the batteries designed for alarm system back ups. I wouldn't even bother if I were you though, heavy and difficult to get current out of.

- Nimh/nicad racing packs - I think this is probably your best bet. Two 7.2V packs in series will happily run your drive plus axe mechanism.

- A123s - This would require you to build your own packs from cells. A 4 or 5 cell pack would happily run your machine and provide you with higher currents.

http://cgi.ebay.co.uk/10-Pcs-New-A123-3 ... 2a01f91692

Not too difficult to build your packs if you follow the information provided by John Reid on the terrorhurtz site.

- Lipo - I wouldn't bother. You won't need the currents these can provide and they're pricier.

Hi guys, brilliant advice, thanks. I've just realised a small mistake I've made though. The magnum 775 is only 14.4 volts where as most of the scooter motors are 24 volts. I wouldn't really want to over-volt them too much as they aren't cheap. Is there a 24v version that I've not found?

Quote:

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Originally Posted by turps

Hi guys, brilliant advice, thanks. I've just realised a small mistake I've made though. The magnum 775 is only 14.4 volts where as most of the scooter motors are 24 volts. I wouldn't really want to over-volt them too much as they aren't cheap. Is there a 24v version that I've not found?

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Yup ...there is actually a link on the Robot Power page.~~

http://www.robotpower.com/images/LS775P ... asheet.pdf

Here's the same one from Leshi's website.

http://www.leshimotor.com/WebUpload/UpL ... 931577.pdf

BTW... 775 is the motor can size.

Regards Woody

Ok I've been doing some thinking and re-thinking and have decided it would probably be cheaper to use 24v drills. This does seem to throw up a problem regarding mounting them though. Are mounts readily available? Also, where do I get the blue wheels that I've seen mentioned? Finally, what would be a good chassis material? I was thinking welded steel angle for the base and weapon mounts but aluminium angle to hold the armour.

Quote:

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Originally Posted by turps

Ok I've been doing some thinking and re-thinking and have decided it would probably be cheaper to use 24v drills. This does seem to throw up a problem regarding mounting them though. Are mounts readily available?

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No, tried that. The motor themselves were a larger diameter than the drill kits. That and the final assembly came out at 10cm per motor - 20cm end to end. Wheel worked fine though...

for the drill mounting kits and the wheels contact robochallenge (google search) phone or email them

the wheels come in varying sizes