Ebay barely works on my Android 4 tablet , the price is right so I have ordered 6 gearboxes for $183 with postage. Apart from the carrier plates, it looks like a fixed backplate to attach the motor and at least a light front cover plate is needed.

Can someone have a think about how to reverse engineer the plates and make a new set? I have a fair amount of 3/8" 6061 ali plate to make the carriers and mounting plates from. Adding a bronze or even roller bearing to the planetary gears might be worthwhile to increase efficiency - thoughts?

For a motor, I like the idea of an outrunner with a around 300W output; if a 550 motor capable of 100W can successfully push a feather around, then a more efficient 300W motor should have no trouble in a lightweight. This one might be appropriate:
http://www.hobbyking.com/hobbyking/store/__14847__NTM_Prop_Drive_Series_35_36A_910Kv_350W.html



It would need a new shaft to mate with the gearbox; not much work in that.

I happen to have one of those exact ones right here above my PC. It's only a little large in size to the motors we're using as beetleweight spinner motors... I think it's really just too small?
Carrier plate reverse engineering, I'm already on it.

OK, I'm not adverse to going larger, just want to avoid using a motor that would blow the ESC. We could use a larger, higher voltage motor and down-rate it to get enought power and heat dissapation so it never blows itself or the ESC.

Most of the motors in this class are pretty low voltage and the ESCs are only good to 3 to 4S LIPO packs, so it looks like the bot will need seperate batteries for drive and weapon. That makes the electronics a little more complicated but stiill manageable.

If the motor has a low KV and spins around 11K rpm on 3S, then the gearbox will need about another 2.5:1 reduction to the wheels to give a good speed range in the arena. This one might do it: http://www.hobbyking.com/hobbyking/store/__19831__NTM_Prop_Drive_Series_42_38_750kv_785w.html

If you're looking at brushless drives, Hot Stuff at Robogames was using a brushless mated to a dewalt gearbox and it seemed to work fairly well-

http://forums.delphiforums.com/THERFL/messages?msg=6331.67

Yeah, I have been following that thread - the motor and ESC are great but I am really not keen on a plastic gearbox! The other thing I like about the current outrunner + Currie gearbox is how short it is compared to a DeWalt powerdrive kit. IMHO, many vertical spinners have problems fitting in long drive motors with battery packs and weapon motors and make bad compromises.

Research time

I downloaded & watched a shed-load of vertical spinner videos today and there are some important design lessons to take on board:

1) Vertical spinners with front wedges do better than those without (IE K2, Electric Boogaloo, Demon).

2) When vertical spinners face off, the one with the larger wedge usually wins.

3) Vertical spinners without a self-righting mechanism never win medals.

4) Even the best vertical spinners lose if they are out manouvered by faster bots.

There are plenty more videos to analyse but Ogre needs overcome all the above to get on the podium.

Speed : more than K2 (using DeWalts in low gear @ 22.2V and about a 4" wheel) and preferably something like Touro Light (drive unknown).

Wedge : This is the most critical part and also the area where we can make a smart decision! A heavy and low angle wedge like K2 works well against other vertical spinners and wedge bots, not so effective with undercutters. I propose the front & back of the bot are angled around 45 Deg. and the front has optional lower angled wedgletts that can be removed for undercutter matches.

Drive: 4 wheel drive now looks to have too many weight dissavantges; 2 wheel rear drive with really grippy wheels and the torque to push a fixed wedge will provide enough drive while giving a front fixed wedge plenty of pushing power.

quote:

---

Touro Light used two 36:1 42mm Banebots gearboxes, powered by 14.4V Mabuchi RS-775
motors, to drive its two 5” diameter Colson wheels. Even with the speed controllers trimmed to a
20V limit, the overvolting of the 14.4V RS-775 motors caused them to overheat. This overheating
forced us to replace them almost every 2 matches during RoboGames 2007.
In 2008, the RS-775 were upgraded to
18V DeWalt motors

---

For that carrier we could CnC it out of a block, just need to make some kind of broach or something for the central gear (or put a fixed shaft there for another pinion gear)

I think roller bearings are probably not the best idea in a bot, they are generally much weaker than a bushing in terms of impact, but if they are stronger than the teeth it might still be a win.
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Mechanical engineers build weapons, civil engineers build targets

Doh! I should have thought of looking at the Riobots book! that brings up an interesting point; the old 42mm gearboxes have the same sized gears as the newer P60 gearbox. If that is working reliably in Touro Light, then it could be a good choice for Ogre as it is so compact & light. I have plenty of spare P60 gearboxes and we can built a quick test platform to see how they go.

@ Jake: sounds good, I agree that bushings are probably the right choice. I think I already have a 2024 ali rod about the right diameter. On the output side, the carrier could just have a pressed-in shaft that is supported by a bearing fixed in the front cover plate ( something else to be designed)

After looking thru many brushless ESC specs, comparing prices and reading reviews, I am going back to Dewalts, at least for now. The future is definitely brushless motors, but the controllers are not quite there yet for robots. The cheap HK car ESCs are all out of stock and most of them don't do sensored motors and instant reverse. The name brand controllers are quite expensive and the motors even more so.

Going back to 18V DeWalts is the safe, if boring choice and they will couple up to the most promising gearboxes. To keep the motor from breaking due to impacts, I will design a plastic support block to hold the can in place and stop the brushes popping out - going to need some high temp plastic for that!

For, wheels, Colson 4" by 2" wheels will provide plenty of grip; once they are turned down flat the real width will be around 38mm.

Probably a good choice for an international contender. Better to go with tried and true / reliable brushed drive rather than bleeding edge brushless.

Ideally I suppose the bot needs to be as reliable as possible, given the nature of the undertaking incl. expensive flights and accom etc.
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<Patrician|Away> what does your robot do, sam
<bovril> it collects data about the surrounding environment, then discards it and drives into walls

If you're set on dewalts they're going to need a different gearbox solution than the scooter motor gearboxes I don't think the ratio will be near enough. I know they're heavy but the 100W size motors are pretty reliable and burn out proof plus lets you get away with a very small esc. Also K2 uses dewalts (in low gear I think?) and it's slow as.

EDIT: I know all the brushless escs are out of stock on hobbyking which sucks, but realised that one of these motors would mate quite easily with the scooter gearboxes, it's the same I bought for the CNC and its got an 8mm shaft despite being only 43mm long. I think I might have to try buying one of those car controllers and seeing how responsive it is. Considering how well hot stuff did with the escs I don't think they should be dismissed quite yet.


They're also currently $25 ea posted haha

Has anyone ever had a 100w scooter motor fail in combat?
I think Glen didn't even kill the one in Visceral with that epic 36v 1:1 drum setup.
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https://www.halfdonethings.com/

I think Gary is the only one to have had one of those motors fail. It was driving the drum on Reboot and the weapon teeth contacted the motor casing causing a magnet to come off/break.

I don't know if I would call that a failure rather being destroyed....

Steve
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Steven Martin
Twisted Constructions
http://www.botbitz.com