That was an idea but I'm a bit worried about how it'd affect weight distribution, if I moved the motors back to fit a belt drive in there there'd be very little weight over the wheels, so it'd probably not drive so well, I'd assume...
How thick is the bar? I can't see how that design weighs 3.5kg, as it looks quite thin. Also, a design like that looks menacing but the MOI for the weight will be quite low, as much of the mass is near the bore (in the counterweight).
A shape like this measures 200mm tip-bore and has an offset bite of about 17mm, but it would have to be more than 15mm thick to weigh 3.5kg...- could be made to look nastier, just an example. It could be mostly 10-12mm thick with thicker ends to bump up the MOI.
Can't see how the one in the CAD weighs the same? It looks like it's mostly 6-8mm thick?
Either way it will be nice to see a bigole vertical bar spinner, they're always intimidating!
Last edited by Ellis; 16th July 2014 at 18:56.
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.
A pair of ruggedized Gimson GR02's with 18V motors* and 36-1 gearratio will do well enough I think.
Put everything on 5S and simplify the logistics train a lot.
* 2500-3000 KV Brushless inrunners with 1/8" axles are a possible replacement for the original motors.
@Ellis; The bar in CAD is quite possibly thinner than the actual design, Alex designed it and I roughly remade the shape with the same dimensions in the CAD. This may give a better idea:
@Mike; That URL gives me a 404 :/
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.
That explains it! The massive tooth is pretty awesome.
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.
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 costsOriginally Posted by MikeNCR
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
Last edited by overkill; 17th July 2014 at 01:04.
Posting Permissions
Reply With Quote
Bookmarks