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Ogre - RG2013 lightweight
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Nick
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Ogre - RG2013 lightweight

Specifications:

My initial ideas are:

Vertically spinning disk or bar. Diameter TBA but not much larger than a featherweight. Massively thick to pack in plenty of KE and resist damage from horizontal spinners. Material will be waterjetted Bisalloy.

The weapon will spin on a large, fixed axle to help keep the frame strong. It will use a V pulley to a brushless out-runner and spin relatively slowly, 4K rpm tops so that it gets a better bite on opponents.

Body will be Bisalloy frame with "bullet steel" sides if any can be found. Internal parts will use aluminium or magnesium to keep the weight down. Top cover to be titanium.

The drive motors are hard to pick; DeWalt power drives are popular, but I don't like the speed ranges. 4 wheel drive with Banebot P60 gearboxes and brushless motors is looking good at the moment. Wheels will be small Colsons.

Post Tue Apr 24, 2012 9:14 pm 
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Glen
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That's a design i can get behind ;D

Weapon being super thick is a definite, diameter, maybe 300-350 diameter and 7-8kg. Having it thicker and comparatively smaller seems to work just as well as thin and massive in diam. With single tooth blades being pretty easy to make these days you can spin a smaller diameter weapon pretty damn fast to get some major power.

I've wanted to make a 3d disk with a dished out center, but cant think of any way that it could be made without a machining center and some hardcore carbide tooling Razz

+ waterjetting the weapon arms straight out of bisalloy as well with zero taper waterjetting was what i had planned. It really didn't seem all that much lighter having it done out of pocketed aluminium or 'windowed' out bisalloy of an appropriate amount. Guess we would have to sit down and cad it up to see Smile

Now weapon speed, 4000rpm is childs play Razz killer and demon are both 7000rpm and since going to a proper one toothed weapon i can't remember it grinding on anyone. 7000rpm would do it Razz

Not sure if 4wd would be an advantage in a vertical spinner when its got them off the ground most of the time unless your plan is to use 4 smaller motors. A pair of mini magmotor gearboxes up the back with wheels that kinda semi poke out the rear end would be fairly epic. *dreams* lol.
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Post Wed Apr 25, 2012 5:44 pm 
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Jaemus
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Awesome!

Devils advocate: I dunno how wide the chassis is planned to be but would suggest that limiting the rpm with that soft of weight would help with the gyro problems such as demon experiences
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Post Wed Apr 25, 2012 6:06 pm 
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Valen
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our mill has cut biz before
its not *that* insane
and we are building our new mill now, work area is ~600x600
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Post Wed Apr 25, 2012 8:10 pm 
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Glen
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Sounds like you're volunteering ;D haha
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Post Wed Apr 25, 2012 8:18 pm 
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Valen
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speculatively yes.
though keep in mind our current y axis is only 190mm
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Post Wed Apr 25, 2012 8:54 pm 
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Nick
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@ Glen: Not sure what you mean by a 'dished out disk'? Would the arms just be thinner than the rim to increase the KE for the same weight? That's definitely a good idea and would save space as well.

Weapon speed:
I like the idea of going as fast as possible without having the gyro effect reducing mobility - there are plenty of fast lightweights in RG and having something like Touro out maneuver us would be fatal. A wider frame, keeping the centre of gravity as low as possible and experimenting with the RPM will find the sweet spot. I remember that Demon appeared to get a better bite on bots at the last QLD event when the disk was limited - it did almost as much damage and got more frequent hits.

Drive system:
I don't really like ANY of the options for lightweight gear motors Rolling Eyes. Dewalts are the classic solution but the output speeds are far from ideal. The smaller P60 gearboxes are a bit fragile for a lightweight, which is why I was suggesting four of them. The Magnum gearboxes are cheap Chinese garbage and there isn't much else in the right power range. Are there any other suggestions?

How about 2 dewalts with a chain drive reduction to 4 smallish wheels? Alternatively, those 1/8th scale brushless motors that Andrew found look pretty good and are smaller & lighter.

Post Wed Apr 25, 2012 9:09 pm 
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Glen
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WELL. i haven't tried to cad it yet, but my thoughts were that yeah, the spokes and part of the rim could be machined in the Z axis such that it balances the one tooth disk more effectively.

Its a giant waste of KE doing it the way i currently am, because you need so much counterweight added closer to the center. If it's dished out properly, then most of that weight can stay in the rim.

Pretty tricky to explain, i'll have to draw it out when i get bored Razz

With the right design i don't think mobility will be too bad. Half demons problem is when it lifts up, it takes both wheels off the ground because it lifts up on the side of the frame, so it has nearly zero friction on the ground and does a few circles before the wheel hits the ground and it can drive again.

That and the weapon shaft height is really high up versus its wheelbase. The current version is just making the most of a really crap design Razz

I have an inkling with a good weight balance, having the wheels further back and a wide-ish wheelbase would make a vertical spinner that steers much much better. The vertical spinner Angus made drove a million times better with that setup than mine ever has lol!

Could make a mockup of it anyway to test the drivability side of things anyways once you get a basic design penned down and work out the internals.

To be honest i dont know what would be good for lightweight drives. Dewalts would have the power, but i reckon they'd fall apart. What about those CIM motors they use in FIRST robots? i don't think they are that huge Razz
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Post Wed Apr 25, 2012 9:24 pm 
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Knightrous
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quote:
Originally posted by Glen:
To be honest i dont know what would be good for lightweight drives. Dewalts would have the power, but i reckon they'd fall apart. What about those CIM motors they use in FIRST robots? i don't think they are that huge Razz


Might have something you can try.

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Post Wed Apr 25, 2012 9:35 pm 
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Nick
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I have a CIM motor; they are OK quality but have a low power to weight ratio compared to anything else and are about the same size as a DeWalt. Its probably overkill, but I already have some Banebots P80 gearboxes; sticking a brushless motor on the back of a P80 would make for an extremely tough (if bulky) drivetrain[/b]

Post Thu Apr 26, 2012 12:07 am 
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Glen
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Might be worth finding a suitable motor and doing a custom gearbox housing with chunky spur gears then.
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Post Thu Apr 26, 2012 1:11 am 
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dyrodium
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I just dug out those planetary gearboxes I bought for the 100W motors, they're hugely chunky and with a new custom drive plate and bearing I think they might be a decent option too. Smile

Post Thu Apr 26, 2012 1:14 am 
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Nick
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Are those the flat ones from a scooter drive - any idea on the ratio? If we used one larger motor per side with a lower RPM and then a further belt reduction to the wheels, that could save quite a bit of space. Perhaps an outrunner and a reversible car ESC would be a good match?

The only reservation I have is future supply - can we get a few more for spares?

RE Glen's comment on better drive wheel positioning: I had a look at Catastrophe with the drill motors and bunnings wheels at the back. It looks like a trade-off with armour; Demon's angled sides do a brilliant defence job and only get bent where its been re-welded multiple times. If we went back to vertical sides so the wheels had better floor contact, the bot would lose much of the armour effectiveness. Its a difficult choice - we might need to do some testing.

Post Thu Apr 26, 2012 2:55 am 
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Knightrous
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The planetary gear sets for the scooter motors are 4:1
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Post Thu Apr 26, 2012 8:09 am 
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dyrodium
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!

http://www.ebay.com.au/itm/Currie-Planetary-Gear-75mm-Planetary-Gear-Scooter-/270848021636?pt=LH_DefaultDomain_0&hash=item3f0fccd484

They seen to be available still, and the price isn't bad. The gears and ring are really good quality but the carriers are cast shite. A rotary table will make short work of a new carrier and whatever output. Smile
The 100W 12v motors overvolted might make a good lightweight drive, or any motor with an 8mm shaft to engage with the D in the gear.

Post Thu Apr 26, 2012 2:09 pm 
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