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The weakness of machines

All of the robots I have built have failed in fights, and usually at the axles/wheels, it's like a running joke.
So why should it be any different with this featherweight?
Meathammer was designed back in 2005/06 when using 4 drill motors was a bit of a novelty... it was made more novel still by mounting the epicyclic gear cages directly to the chassis, which unfortunately sends all the drive shocks back through the gearbox.

The original version ran for a number of fights at modelworld 2006? and even won some, especially the sumo, which favoured its very low profile.
I've just rebuilt the gearboxes with all metal gears, and tested it, and it seems it should last for at least one fight… but as I put it in the car after testing, I noted one of the wheels had nearly fallen off. Mark that bolt for Lockthreading!

All this got me thinking if I could make something less likely to lose a wheel, break a gearbox etc
I have a huge pile of bits and bobs that were destined for heavier machines, and so are less likely to break, so I thought I'd try and lash them together into a more robust unit, instead of mashing on the same old design.

So here's the parts list:
2 X 30A  Indiana General motors, which first saw light of day in the original KillerCarrot, then in a middleweight version. Their big advantage is they only draw 30amp at stall (Some might see this as a disadvantage), and they are only 80mm across, meaning I can run them direct to 100mm wheels. They are hugely heavy though.
KC1 rebuilt with steel shell back in 2001
4 X 12mm Bearing mounts
A length of 12mm silver steel driveshaft
Sabretooth 2X25 ESC which should cope with the motors, as they allow a brief peak of 50Amps.
2 X 18Volt 1.8Ah Lion battery packs from an old strimmer.
4 X 100mm Blue trolley wheels.
A bunch of old lexan, and some bolts and steel and whatnot… and an old 40MHz Tx/Rx set.

All I need to machine are a couple of wheel mounts to fix the wheels to the driveshafts, and a couple of motor mounts, which will be made of a bit of angle (If I have any… )
Here's a photo of the parts…




...and hopefully the next post will be an assembled "thing" ready for testing.

So here's the design: direct drive full body spinner. The motors turn at 100rpm per volt so 18 volts gives  1800rpm, thick driving straight forward on 100mm wheels gives 314mm travel for each rotation, which is around 33kph or 21mph. It will be fun to see if it is in any way controllable.

As a full body spinner the circle described by the axles is around 35cm which means it takes about 11 wheel rotations to turn the body, which means at full blast it should spin the body at 165 rpm.

Maybe… but I've run out of steam today, and will leave the machining till next week.

Comments

Safal Trading said…
This is useful and very Wonderful article,

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ready for action

Just put the finishing touches to Meathammer
The whole setup works quite well.. I'm off to modelworld to run it through it's paces a couple of times.
The weak bits look to be the drive shafts, which I'd like to bulk up to at least 20mm and have some better bearnings for.
The battery packs are also a bit weedy, but we'll see how they last, and may invest in a few high output packs.
Of course it could also really do with running the 4QD 35's or 60's instead of the electronise speedies.. but we'll see how it performs and make amends.
Since I took this phot I've added a hinged scoop, so we can get under other feathers... it's a popular design in the states, should work over here.
I only need to wire in an LED to show power and then we are ok to roll.

robot rebuilds

For two years in a row I've missed out joining in with Ian Watts robot bash at the Uni. So I'm making sure I've got something running before it swings around again.

So I welded a couple of new gearbox cages into the 4 wheel push bot, and dug out a set of Electronize speed controllers. I fitted the titanium plate that has been cluttering the basement for a decade and have been doing some testing with a set of LiON batteries that used to belong to a cordless strimmer, which fell apart from overuse.


I've run it up and the battery doesn't really have enough life to power 4 motors, but is useful for testing. I've stuck some old NiMH units on a charge cycle to see if they have enough life for a bout or two. The only things I actually need to "buy" are a 2.4GHz radio set, as the old 40MHz stuff is against the rules these days, so I've ordered a Hobby King 4 channel set for £20 off ebay.

Strangely yesterday Mentorn emailed a bunch of robot folk to say Rob…