HardWired II

[Eventorizon]

The bar in cad weighs 3.6kg. Its made of 3 pieces of 10mm thick steel (Could be Hardox or stainless or whatever) Its 400mm effective radius with 60mm of bite.

[Ellis]

That explains it! The massive tooth is pretty awesome.

[Eventorizon]

With some clever wiring you can set it up so that with 2 5S packs one powers each drive motor and they both power the weapon. You would need 2 links and high discharge lipos but it would give you the 2 voltages in the same system. the atlernative is two totally independent systems like in Binky & Conker: binky running a 2.6Ah 4S for drive and 2x 2.6Ah 5S for weapon. Conker has 1x 3.3Ah 4S for drive and 2x 2.7Ah 6S for the weapon.

[shakesc]

This may be worth looking at as a banebots alternative- http://www.vexrobotics.com/vexpro/ge...planetary.html

Drumthing Else ran a pair for drive at Motorama with 775's iirc and the gearboxes seemed to hold up fine.

There is no UK distributor for the Vex Pro components. I had a long dialogue with the current Vex distributor but it didnt seem to get to the point of him picking up the Vex Pro line. So the only alternative is order direct from the US with very high courier costs

[overkill]

You can always gear down with smaller wheels. To keep the inverted driving ability, add a set of friction driven wheels above the regular pair. By the time you get around to buying parts there may be a brushless motor option with the right KV or a 3mm shaft that will work on 26:1 Banebots gearboxes - just keep your options open as long as possible.

I did a very rough kinetic energy calc using a straight steel bar with the weight & diameter you mentioned - 11.1 Kj at 7K rpm! Your bar has more weight at the tips so its going to have an even higher energy. That would probably be the highest energy rating for a featherweight in the UK.

Update: with a 3.6Kg weight, a straight bar would have more like 13.5Kj

[overkill]

This may be worth looking at as a banebots alternative- http://www.vexrobotics.com/vexpro/ge...planetary.html

Drumthing Else ran a pair for drive at Motorama with 775's iirc and the gearboxes seemed to hold up fine.

I have a pair of those and they are VERY disappointing! The internal gears are fine, but the output shaft is aluminium . Its also quite short at 1.5", so you can only use a very narrow wheel if you want to use an outside support bearing. Changing the shaft to steel might be possible but looks like more work than most people will want to do. If VEX came out with a better output shaft, I would definitely recommend them.

[Flag Captured]

Yeah, I really like the massive tooth on it! I guess things could always be refined but the general idea seems to be spot on! I'd possibly like to up the diameter of the bar's shaft a little (20mm to maybe 25/30) to account for the power in it, but I don't think it'll be too big of an issue considering it's fixed.

The tradeoff with such huge bite is that it might not have as much KE in it I think, however it does mean if I'm feeling truly insane I can maybe up the speed and still get nice bite. 14000 rpm anyone? (I'm kidding, that really would cause absolute carnage, for precisely one hit. If I could hobble over to another machine before everything got all nice and firey electronics-wise.)

Keeping options as open as possible like Nick says is probably my best plan here. I like Mario's suggestion of the strengthened GR02's since that'd help save a nice bit of weight that could go on helping strengthen everything else (or even extra batteries). Those Versa gearmotors look pretty decent too, Mike, but the problem is that the site's saying they don't ship to Europe... which could be a bother. I do like how they appear to be customisable though, might be a good way to get the exact reduction I'd need!

I'm thinking having dual voltages through separate systems may be a better option in this case, it's more weight but perhaps it'll end up working better, especially if I have a 4s/5s drive and something like a 12s weapon motor. I don't know, but I certainly will keep my eye out for motors that may be more efficient at a lower voltage. Probably will look into the types of motors that such as Demon or maybe even Unmakerbot use for inspiration. Particularly Demon, because Demon terrifies me with how brutal that is...

I've been looking at the design too, and perhaps the wedge at the back being how it is may be a little unnecessary? I don't know, perhaps a more angled slope and less long design, but keep it as wide? Could have a little angled tail at the back too to house the bulkheads whilst keeping the wheels to the front... wouldn't be able to be invertible though if I did that, though could possibly allow me more weight to go towards making the belt/bar system as reliable as it can get... It would, however, make things a tighter squeeze inside the machine and I'm not entirely sure how I feel about that! Shock mounting is definitely something I'm looking into more across the board too, it was certainly my downfall this year.

That's downright scary as well Nick, from the sounds of things - thanks! 11-13kj might cause some serious carnage! I'm almost starting to worry about keeping it in the arena at this rate, it'll just take something to catch it right and it's off out, though I suppose that is the danger with spinners!

[Andy]

Starting to sound crazy powerful lol, also what you said about the belts upping the ratio with banebot gearboxes and what matt said about having the motors not directly attached to the gearboxes might be a good idea with the energy that could be going through the system, maybe you could do some kind of suspension or shock mounting with this? goodluck with the build.

[overkill]

I did the maths on the bite depth and with weapon at full speed and the bot moving at around 14 KPH ( what it would do with 775 motors and 32:1 reduction) the bite depth is 35mm, still very destructive. Once you finalise the choice of the drive train and it's top speed. you can adjust the bar design to make the counterweight side longer and lighter, like Ellis pointed out. I can put the maths into a spreadsheet for you if you want to run different scenarios.

With the gearboxes, the GR02 sounds ideal for lower weight and the gearing is about right without messing about with extra belts. The VEX gearboxes can be bought from resellers that ship internationally, I found a couple with Google if you want to go that way. I am testing a pair out with in-runner motors and so far, I like the results.

Glen used a custom wound Scorpion in Demon, but he has recently upgraded it to a larger model, making it even more lethal. To swing a large diameter blade like yours, you either need some good start-up torque of lots of gear reduction. Whatever you chose, I would go for the largest diameter outrunner as they have more start-up torque. If I was going to pick a dream motor, it would be a Scorpion 50 series with a custom winding to get a higher KV.

The wedge at the back worried me; if an opponent drove up it the weapon would act as a high speed crusher on the down stroke and much of the blade's energy would be transmitted into the frame. If the bar hit something really solid, the frame could get severely bent. I would still give the back panel a slope, just not enough to wedge up an opponent.

@ Andy: with a vertical spinner, you don't want any suspension as it wastes impact energy - the stiffer the frame and wheels, the better the hits. Adding outside support bearings would be a really good idea though, the gearbox axles will need to take a beating.

[overkill]

Update on those VEX gearboxes: one of mine just jammed solid after barely 5 minutes running with no load. They are complete junk and not worth using at any price!

[Flag Captured]

That's still pretty strong, thanks Nick!
My understanding is that with more bite there's less KE, but the more bite you get the more of that KE can be transferred into the target?

Yeah, I think the back may go to being a little more like Hardwired 2's is with a slightly slanted piece of something, maybe just HDPE to allow for a little bit of ability to push and resistance from spinners but nothing too wedgey... It does mean I'd not be able to run invertible wheels maybe but I guess that's just a tradeoff I'll have to take. Besides, I don't think I'll need it if I can put that weight being saved into making the bar more reliable, since it'll right itself anyway when the bar catches the floor or something!

Whilst it may seem completely OTT, would something like this perhaps be suitable? http://www.scorpionsystem.com/catalo...KIII_5035_500/

It's a lot of power, though perhaps with a custom winding for higher KV, it'd be something quite powerful, and maybe a motor that size not running on it maximum capacity might not get as warm either? Granted I'll need to make provisions elsewhere because it's quite a big motor, but I'm sure I could save it by chopping some of the back scoop off and running GR02s or something. Mario's suggested brushless too which could save a nice bit of weight as well, assuming the speed controllers are also light (which the stats say they are).
If that's a little much (7kw peak probably is) then there's the 5020 which is 4kw continuous and about 5.5 peak, which should do just as well. That extra bit of power might make startup a lot nicer though, perhaps... I could attempt to go for the best of both worlds and try a KV rating towards 1000 and go for more belt reduction, maybe 3:1 or something. At 6s that'd be ideal, though I do intend to try and up it to something a little crazier like 10 or 12s at some point for extra punch but it's a question of how reliable it'd be on that sort of voltage as well as if the rest of the machine would take it...

I'm looking at ways to save weight armour-wise if it's needed too, the front plate will be hardox and aluminium bulkheads, but everything else will be hdpe I think.

That solves a debate with the VEX gearboxes haha! Wouldn't want that to happen whilst they're in a machine...

[Andy]

The 5035 is probably overkill, and on 6S it probably wouldn't pay off as Nick mentioned about the 50 motor in an earlier post. It would probably be better do use a hk40 with a higher kv and gear it down more, cheaper too

[overkill]

KE and bite are not directly related, the RPM of the blade is the only thing they have in common. For a high KV, you want plenty of weight (better if its distributed out to the edge) and high speed. For more bite, you want either less speed or fewer teeth, plus a higher driving speed.

As your design has a heavy blade going at a pretty high RPM with only one tooth, you have the best combination of high KV with a large bite depth to help transfer the energy into opponents. About the only thing to change is moving the counterweight a bit further out and making it lighter.

You can probably still run inverted with less sloped rear armour, the wheels would just need to be moved further back. This bot has vertical rear armour and could still theoretically drive inverted:



The only problem with moving the wheels to the back is that there is less weight over them and they get less traction - its all about compromising one way or the other.

The weapon motor is tricky; its probably better to go for more gearing and limit the motor size a bit - I can't find any large, high KV motors in the first place. Just looking at the Scorpion range, the largest motor with a KV over 600 is the HK3 4025 series. All the larger motors are around the 500KV mark and higher voltage. An over-sized motor is definitely going to run cooler, its a question of whether there is the space and weight to fit it.

[Eventorizon]

The 5035 is probably overkill, and on 6S it probably wouldn't pay off as Nick mentioned about the 50 motor in an earlier post. It would probably be better do use a hk40 with a higher kv and gear it down more, cheaper too

It is total overkill. Conker Runs a HK 5020 on 12S and gets 11000 at the weapon, with a 2:1 reduction. I ran that as it was a better shape for my machine than the longer HK 4035. The massive stator give it a huge amount of torque. I believe you could run it 1:1 on that bar and be fine, so long as you ran 10S or more.

The alternative is go like 720, running a 5S pack and have a high KV inrunner and a greater reduction. It simplifies your wiring and means you can save on the cost of batteries, and high voltage ESC's. However I believe in a machine shaped like yours that a HK 50 would fit in better than a long thin inrunner.

EDIT: I have also tweaked the weapon design to have 40mm of bite rather than 60, and it now weighs 3.45kg. With all the bearings and supporting parts it will weigh around 4Kg... that is one hell of a weapon!

[Ellis]

Are you referring to how much offset there is between the tooth tip and the counterweight? Because the maximum (theoretical, and so in unrealistically perfect conditions) bite is just 23mm (6mph and 7k on bar). That's based on the lip/edge you're going to hit entering the sweep of the tooth the instant after it passes by, getting full depth bite on the next rotation. A 15-20mm offset will give a very marked single tooth effect and a higher MOI, as there is more mass further from the shaft.

To contain the amount of energy in a bar like this won't be easy! :P