Team Bitza

[PJ-27]

Who?

[psychostorm]

http://robotwars.wikia.com/wiki/Griffon

Meet Griffon, successor to first war finalist Cunning Plan. Managed to lift Sergeant Bash but not over turn it. Had a shot at Killalot before Wheely Big Cheese too.

[PJ-27]

Oh yeh I remember that!

[PJ-27]

Me and Dan spent a bit of time yesterday cadding up the 4 Bar in Inventor and managed to simulate the action. Pretty happy with the arm lengths we've chosen.
I'll get pics up in a bit.

In other news got my hands on a car wheel for the FBS:


Wheel 1.jpg

BitzaWood in the background for scale. Figured I'd have one last stab at the Bitza thing.

Problems already:
It weighs 8kgs! Back of beer matt calcs tell us that we'll need to get it down to 6kgs to be viable.
I'm assuming it's strong, but I could be wrong. I figured spinning at several thousand rpm under a car for several years taking the pot holes of Britain it's got to be pretty strong right?

[Andy]

Reminds me of spin doctor and trouble and strike, looking forward to seeing the robot finished, certainly sounds cool so far :P

[psychostorm]

Reminds me of micro maul. Now there's showing my age. LOL

[PJ-27]

Some mock-ups of the 4Bar. Going for big wheels lots of ground clearance because I'm sick of getting stuck on debris!

Screen Shot 2013-06-12 at 17.49.07.png
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[Ellis]

Looks good but honestly, people using standard drill-based gearboxes for such weapons will forever have problems. They break in drive setups, the shocks a lifter arm sees are different but possibly a lot greater. Think 720 hitting the arm as you're bringing it down, torque of the motor fighting the massive impact shock going in the opposition direction, or it landing from a 6ft flip onto the arena wall.

It may sound like I'm just being cynical but, either the motor pinion will come loose and jam, the second stage gears will strip, or (most likely) the pins will fail on the second stage resulting in it promptly killing itself. Look at the relentless problems people are getting with such gearboxes in axe weapons.

You can probably soften some of the huge impacts with a torque limiter such as the one a drill has installed, but you'll lose performance. A Gimson, unless it's belt driven and has some decent slip, will almost certainly fail.

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There are definitely ways to improve these issues, however. You can put a flat on the motor and use a pinion with a D shaped bore, and you can prevent the second stage pins from coming loose with some tricks. We are doing this in Tormenta 2's drive and finally, after forever, we're seeing some reliability.

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I don't mean to burst any bubbles, I'm just going by experience of using drills since the beginning. :P

You can still use a 550 motor with a tougher gearbox as the problems almost always arise from the transmission. Banebots come to mind.

Or you could use a larger motor (lifting anything at speed with a 550 is always going to be interesting), such as a scooter motor or similar. A fraction of the reduction needed and worlds more robust. I realise I say this with a drill behind our weapon, but it's one big drill.

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My 2 cents. I like the design. Next 4WD type thing we build will also most likely have big wheels, I love that look. I'm sure you'll get the current setup working reliably with time but I'm just trying to prevent some headaches.

[PJ-27]

Dan thought it was a bad idea too for other reasons, so starting to be convinced.

I had also forgotten than the recommended maximum torque on the Gimson gearboxes in about half what they can put out at stall, so yeh they would likely break since I would need full stall torque from both to do anything meaningful.

So now thinking linear actuators, or big low rpm motors with a single stage reduction.

We have 3 fan motors spare, but they're just big, heavy and difficult to mount.

[Max]

If you want to be 'Bitza' then you could possibly use a heavy duty wiper motor- cheep to replace and low rpm, I think if you gets good one they have quite a lot of torque. I thibkiñg like or from a lorry or train. Of course they way a lot, but that's the challenge!
Your going to struggle to make an electric flipper without some serious torque, even Tormenta 2 with it's massive drill motor is just a fast lifter I would argue, but I've seen little of it in action.

[Max]

Something like this:
http://item.mobileweb.ebay.co.uk/vie...722&cmd=VIDESC
Which claims to have 50Nm rather than a GR02 which has 12.1. But I imagine that thing ways a lot and is quite a lot but I imagine something similar could be bought from a scrap yard

[Ellis]

I'd argue way in favour of a large low rpm torquey motor geared down! We've all see linac four-bars, a fast moving one would be awesome!

Also I don't think Tormenta 2's classifiable as a flipper quite, but it certainly throws robots (and itself) with ease, which perhaps distances it from the lifter class. Let James control it at Yeovil, and when he went to use the weapon he wasn't expecting the speed and clean snapped the chain purely by turning it on hard.

[PJ-27]

Wiper motors could be an alternative, I have a few spare car ones. Not sure on the gearboxes, but maybe a couple of them would do it.

[PJ-27]

Well my ideal situation would be to have a motor spinning a flywheel that engages a clutch via RC that slams the arms round. I don't think there are any stored energy weapons in the UK (except spinners) but that level of engineering is out my my reach unfortunately.

If I did linacs then I'd do them fast. 2 actuators, connected as close as possible to the pivot point, 12v motors on 24v.

[Bacon Wizard]

Apart from the type of weapon itself, that's exactly what I'm up-to in my heavy. Just bought an Etek motor off typhoon Gary for the flyweheel