Hi-Power Spinners cause spectacular carnage and violently win matches, but they rarely win events if they have to go more than a few rounds..

Carrying that much energy around means you are carrying the seeds of your own destruction within you. Newtons laws of action and re-action still apply.. so they need to absorb just as many kilojoules as they dish out,

The difference is that hopefully their bearings and frame are designed to absorb the energy in the same place each time (the spinner shaft), whereas their opponent's armour usually can't be designed to handle kilojoules of energy everywhere they are likely to be hit (unless its a brick bot, the spinners natural enemy).

Its a *very* difficult engineering challenge to come up with a spinner than can hit hard, and *keep* hitting.. Even the most successful spinner ever (Hazard) had to throw the entire chassis away and start afresh with each season due to the torqued-up twisted frame from thumping out so many hits.

For those who wish to go the high Kilojoule Spinner route, I salute you, but I wouldnt give much for your chances of seeing you on the winners podium for a while..

Thanks Spockie.
I hope that 'Toe Cutter' or 'Ankle Bitter’ is the first to survive a whole event.
Just need to make sure that the design will hold together, just when it is spinning and the parts aren’t to expensive.

I found a couple of different bearings that would do. However, the cost is a little frighting. Need a sponsor.

Any sponsors out there.
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It's all about the destruction.

Very interesting that you mention Hazard; my lightweight Artemis is heavily modeled on Hazard and is a 1/2 scale model in many ways. I plan to fix that frame problem by adding lots of baulkheads and compartmentising the interior of the chassis, particularly around the central gearbox. I will be seam welding everything to create a very stiff torsion box design that spreads the loads out evenly. The chassis will still get battered but I hope it will last longer and at least its one of the cheaper components at around $50 of ali.

From the limited photos I have of Hazard, it's chassis problems were due to a screwed together construction and the single U shaped gearbox support down the centre of the bot. If they had added some extra bracing across the chassis that was well attached to the base and outside frame, it would have been quite a bit stiffer. the outboard wheels and single wedge needed fixing too & needless to say, I taking cae of that.

Any other problems that people see in the Hazard design?
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Australian 2015 Featherweight champion
UK 2016 Gladiator champion

@ Ajax; Care to share your bearing ideas? I am just about to ring around to get prices on double row angular contact bearings - I figure around $50
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Australian 2015 Featherweight champion
UK 2016 Gladiator champion

For low mileage high load bearings, I thought a simple oillite-style bronze bush was supposed to be the way to go.. in use by many of the big US spinners I think. maximum contact area, minimum surface loading and cheap as.. just make sure they're supported properly and you should be right..

My Gyrocopters 25 foot diameter rotors were held on by a single bolt (in double shear !) running through 2 bronze bushes with a light smear of HP grease.

No balls to flat spot, roller-shafts to bend or other small bits to get torqued up under shock loads.

If you really want to go for a roller style bearing, the sort they use in the front-axle of a car can obviously deal with years of thumping and banging from tons of weight, although they might be too heavy for a feather..

You are correct about the bronze bearings, but for someone without a lathe or mill, a bearing is easier to use. With a bronze bushing, the motor shaft has to be finished to tight tolerances and I think there are extra difficulties in dealing with axial loads. I would go that way if I had the machinery, but bearings offer the easy-out for the under equipped
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Australian 2015 Featherweight champion
UK 2016 Gladiator champion

Yes a bronze bush will work in most cases, but this is me your talking about. I can never do something the simple way.

First Problem.
Making sure the design will not self destuct once it is spun up to speed.

Second Problem
The inside dia of the bearing needs to be
140mm for 'Toe Cutter'
350 - 400mm 'Ankle Bitter'
??? 'Knee Capper'

Third Problem
Weight
'Toe Cutter' 3Kg
'Ankle Bitter' 12Kg
'Knee Capper' 25Kg, 50Kg, 100Kg, (Not sure yet)

with this in mind a bush will cause to many problems.

I did find the perfect bearing fo 'Toe Cutter', but at $2000 each and I need 2. I said re-design, or look for other options. (Still looking, do have some good Ideas)

Nick,
In most cases you are able to by a bronze bush of the self in metric or imperial and shafts to match. The problem is the side load, but for the types of loads that we are going to have a bush will be fine.

About the bearings let me know what you want to do an I will see if I can help. If your looking for a basic bearing for the drive train or weapon. go and have a chat to 'CBC' or some one like that. They are normally a great source of information, and will help you pich the correct one.

I just have the problem that nearly every thing I want to do is just a little bit of the wall.
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It's all about the destruction.

car bearboxes have a few nice bearings in them, and diffs have some angular contact ball bearings which could work nicely.
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The Engine Whisperer - fixer of things

WOW, $2K and 350mm daimeter for a bearing? It must be a ring bearing off a crane turntable or something!

I just want to replace the crappy bearings on an EV motor. The design goals are for it to be thin (10 to 15mm), light, simple and to resist radial and momentary forces. It also needs to take shock loads. The best options would be dual face to face tapered roller bearings or angular ball bearings, but they are way too thick and roller bearings are demanding to mount properly.

I am going to try a deep groove roller bearing with a 20mm ID. Its a compromise on strength, but it fits all the other goals and if it can't take the force, I will stack up a second bearing.

Whatever I use, it needs a custom housing lathed from aluminium and that's the expensive bit.

The other reason I can't use a standard bush and shaft set is that I already have an 8mm shaft in the motor. I need a custom, thicker (about 17mm) shaft to encase the existing shaft and run thru the new bearing (lets call it a fancy tube. The shaft needs steps to locate the bearing and the weapon blade. Finally, the new shaft needs to be coupled to the old one running down it's centre. I don't think pins would be strong enough in a 8mm shaft and cutting a key sounds difficult & expensive, so I might try welding them together at the end. The old EV axle is only 30 mm long on the outside of the motor case, so all this stuff has to be really compact and that rules out all the fancier options...

I'm no engineer and got all this stuff from design guides, so if anyone wants to point out some better options then I'm all ears
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Australian 2015 Featherweight champion
UK 2016 Gladiator champion

I'd probably try to mount the shaft and bearings solidly in the chassis, then use more of a flexible mount for the motor, and drive the main shaft with either a strong pin setup, or some sort of splined coupling.
That way the motor can be partly isolated from the main shaft so that any minor angle changes won't cause more load on the motor's bearings, and you could even use something like a well compressed rubber tube in the coupling area if you knurl / roughen up the motor shaft.
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The Engine Whisperer - fixer of things

Nick,
With what you said the following is what I would consider.

Option 1
Buy a standard shaft, or steel rod to suit and use a bush. (Could use a bearing if you want too)
Then do as "DumHed" stated. there are different types of couplings available including shaft size reduction.

Option 2
Bearing or bush as in option 1.
Drill the centre of the larger shaft to the size of the motor shaft. then drill a couple of holes on the side of the large shaft and tap them (M4 or M5) and use grub screws to hold them.
I would make sure you are able to put 2 grub screws in the holes though

Option 3
Bearing or bush as in option 1.
Drill the centre of the larger shaft to the size of the motor shaft. then cut a slot length ways about 1 or 2 mm wide, and put a clamp around the larger shaft.

Option 1 is my preferred choice. then option 2, if desperate option 3.

I will draw something up quickly to night for you, for a better explanation.
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It's all about the destruction.

Thanks for all the advice!

There isn't enough length for option 1.
As you will find out, grub screws suck in robots, moreso with shock loads,
I am looking hard at your option 3, but using a trantorque bushing to do the clamping. I don't know if you have seen these before; I was using a small one to hold the blade directly on to the EV shaft at the Annhilator event and my experience with them has been great!

The key thing here is that everything has to fit into about 30mm length and still be strong enough to transmit several thousand joules of shock energy when the blade hits. Like Brett said, that isn't easy to do. everything HAS to be tough; my bigger spinner uses a Team Whyachi gearbox with a 1" titanium shaft, massive fortal aliminium housing etc and that's what it takes to be reliable.

If I used a bronze bushing, it would need to be flanged or have a thick wall so there was something for the stepped shaft to run against and resist axial loads - it could work but I think the rather short length I would have to use here (between 10 and 15mm) might not be strong enough unless the daimeter was quite large and therefore heavy.

I almost forgot, the housing to hold the bearing needs to attach directly to the end of the EV motor, so imagine a 100mm wide by 12mm thick ali disk on the end of the EV, with 6 or 8 small screws attaching it around the edge. There is nowhere else to hold the new bearing and if its attached to the motor itself then it doesnt need any of the flexibility of option one.

If nothing else, we are all learing a bit of engineering from this...
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Australian 2015 Featherweight champion
UK 2016 Gladiator champion

By the sounds of it you would be better off finding a different motor.

The trick with grub screws is to have one flat side of the shaft and use two in the same hole. One to lock the shaft in place the other to lock the first grub screw in place. and for extra insurance use some loctite 222 or 242

242 is a little stronger.

and by the way the $2K bearing was the 140mm one.

I can get the turret bearings (Cran bearings) for around $300 to $500. but they are to heavy for a 12Kg bot.

Well that is at the moment anyway, my design is not finished yet. (If I could only remove about 2 -3Kg from the design)
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It's all about the destruction.

quote:

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(If I could only remove about 2 -3Kg from the design)

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Just belt drive the mongrel will u already. Wont kill so many motors that way.
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Andrew Welch, Team Unconventional Robotics