RogueTwo Robots

[harry hills]

Lol, shows if you sort through the shit hard enough you might find a diamond.

[Mouldy]

What wheel OD, voltage, gear ratio and motor are you going for on the banebots? And it don't look like a total rip off of 720... Mines got a gap between the motors so I can take them out without splitting the chassis :P

In all fairness 720 was a combination of drumroll/touro it's kinda the optimum shape for an invertible drum.

[Max]

it's kinda the optimum shape for an invertible drum.

Ahh roboteers modesty! Lol!

[Mouldy]

If you try designing it in any other way there's draw backs...although the latest touro feather being an exception.

[RogueTwoRobots]

I hone the overall shape (although I was heavily influenced by US/Aussie drumbots), Dave comes along and makes it better, then I come along and copy his improvements
But yeah, not a huge scope for major differences, Touro aside.

Wheel OD is 125mm, running on a 5S lipo, 16:1 gearboxes and still tossing up between 775 and 550 motors. The CAD is with 775 motors but there's literally just 5mm of space between the ends of the cans. I don't know how easy it is to pick up spare 775s over here compared to 550s so that could factor into things.

I also envisaged just being able to slide the motor/gearbox out through the cutout in the side, hence why the lack of space in the middle wouldn't be a problem, but now that you've drawn my attention to it, I've realised that the motors are larger than the surface area of the gearbox and wouldn't fit through the cutout. 550s would though. Hmm, deliberations!

[Mouldy]

I went through the same thought process with the hole for the gearbox, then decided to go for the 775's just because there rated voltage is 18v and i wanted to run 5s anyhow... and with the 98mm wheels on 16:1 they stay relatively cool, and spin the wheels easily... not sure what differance running 125mm wheels will make... might be a bit fast? I've turned my turn rates down to around 60% to make it controllable, and ive got way more pushing power then i need really.

[RogueTwoRobots]

Yeah I reckon it'll be stupidly fast on 125mm wheels so dual rates will be on. The added pushing power would be handy as the current version lacks that compared to the first Drumroll, and running them at their rated voltage is never a bad thing.

Was worried that 125mm wheels might be putting too much load on the gearbox as I reckon that's been the cause of having numerous drive failures over the past couple of events, but then those were drill gearboxes and 125mm is the biggest wheel Banebots make so they must be (reasonably) confident it's suitable to use on their gearboxes.

Will probably just go for the 775s then. If I need to get one of them out, worst case scenario I can rip the side bulkhead off in less than five minutes with a battery gun and a hex bit.

[daveimi]

Is there a big difference in power and stuff between the 550's and 775's? I like the look f the 775's

I also wondered, you know on the Banebot's gearboxes how the shaft is one long shaft? Once you've bought your hubs and wheels, what stops the hubs etc. sliding of the end of the shaft?

[Eventorizon]

Info on the two motors can be found here...

775 @ 12V: http://banebots.com/pc/MOTOR-BRUSH/M7-RS775-12

555 @ 12V: http://banebots.com/pc/MOTOR-BRUSH/M5-RS555-12

The 775 has just over double the stall torque of the 555. At peak efficiency the 555 has 4.67 oz-inch where as the 775 has 250% of that at 11.69 oz-inch. I would call that quite a big power difference.

[Maths was: (100/4.67)*11.69 = 250.32]

If you go up to 18V versions then the 775's have a massive 23.99 oz-inch, thats 513% of the 12V 555's.

[Maths was: (100/4.67)*23.99 = 513.7]

EDIT: The shafts on the BB gearbox's are keyed and have a thread tapped into the end, but some loctite and a nice tight grub screw usually do the trick. I did that with mine and I couldn't knock it off or pull it off.

EDIT 2: This will be interesting to see. All of us will be running 18V 775's on 16:1 gearbox's but we will all be using different wheel sizes. C3 uses 73mm, 720 is 98mm and drumroll 3 looks to be 125mm. In a pushing match who will come out on top? C3 will have the advantage of 4WD but will the shear speed of 720 and Drumroll give them an advantage?

[Ellis]

775s, cute!

#885represent.

(looking really good, it will indeed be interesting to see how the thing drives on the 124mm wheels, 18mph top speed give or take!)

edit: actually, pretty sure the 885s, mathematically, aren't as punchy as the 775s. So we'll see.

[Mouldy]

Re; mounting the hubs.

I went belts and braces... The shaft/hub has a key way so I used that... The hub also comes with grub screws in, the screws are to long as standard by about 3mm so I drilled two dimples about 3mm deep into the shaft (one per grub screw)

Then the end of the shaft has some dodgy American thread in it, I drilled and taped that out to M5, put a bolt and a washer in the end...

Then the wheels slide over the hub and are secured with a circlip. In testing the circlip did pop off.. So the washer under the m5bolt is big enough to stop the wheels sliding of the hub.

[daveimi]

That's great thank you.

I'm on my second drill powered pusher and looked at Gimson's and the Banebots stuff but couldn't work out how the hubs and stuff went together, but have been really interested in these. After a rough tot-up with a pair of 775's, 16:1 gearboxes, hubs and wheels I get the cash total to about $165 / £100 plus shipping, does that sound about right?

[RogueTwoRobots]

That's one calculation I forgot to do actually, the speed.
Never really bothered with torque figures much, the arena is a law unto itself and what comes out on top in theory and on paper doesn't always come out top when fighting. That said, theoretically C3 would win in a pushing match. 720 and Drumroll (still calling it Drumroll 2, not 3 ) will be faster but smaller wheels = more pushing power plus you've got four of them so I would expect C3 to take it.

I actually intended to drop the wheel size down to 98mm when I first thought about redesigning back in May, but for some reason I completely forgot when I fired up the CAD last week. And belts and braces is what I was going to go for too, same with tapping out the end shaft hole to a metric thread. Thought about doing it to the gearbox mounts too but more likely to screw something up there, plus it's easy enough to get the 10-32 (or whatever silly imperial size) socket cap screws on eBay.

After a rough tot-up with a pair of 775's, 16:1 gearboxes, hubs and wheels I get the cash total to about $165 / £100 plus shipping, does that sound about right?

I get it to be just over $180, that was with 98mm wheels. Bear in mind that you also need to order the pinion gears for the motors, and keyways for between the motor shafts and the hubs to stop the wheels from slipping. The hubs do have grub screws but I wouldn't trust them to hold all 100% of the load. Plus they'll wear down over time if they're loosened and tightened. Here's a screenshot of all the parts that you'd need (as far as I can tell - Dave or Alex can enlighten me if I've missed anything crucial):

bb_order.jpg

Plus, as you said, shipping etc on top of that which can add $60-odd onto the cost. Worth it in the long run though it seems.

One question though Dave (Moulds - too many Daves on here :P). Have you had to use your spare gearbox yet? I like the idea of having one as a spare but it does push the price up a fair bit. Planning on getting a spare motor anyway but not sure if I could get away with just ordering some of the individual gearbox parts that are more likely to fail rather than going for the whole assembly.

[Mouldy]

Not used it yet, but did swap it because when i taped the end of the shaft i snaped my M5 tap in it lol... so my spare has a tap stuck in it...

id deffo get a spare motor, and make sure you support the back some how (ive got a tube that supports the motors against eachother in the centre) as overtime they will weaken or could bend due to big impacts- one of mines bent slightly and sits at a slight angle to the gearbox after the big hit with NST- it runs ok but im going to swap it out for a spare before GSL just to make sure its super reliable again. Also- i taped my gearbox mount holes to M5 too... there blind holes, so you cant run the tap to deep to damage anything.

RE; your order;

Nope! if your getting 2x 2wide hubs you'll need a minimum of 4 off wheels... and for the price id get a set of spare "snap rings"... circlips if your english... as they dont cost much and if they ping of at an event there not going to be easy to find lol... also worth getting a set of alen keys from the US... as they come with some dodgy bolts with heads that dont tend to come in your average imperial allen key set.

Tip with the banebots wheels- after a match you'll find they furr up a bit because there a real soft compound- take the robot outside after its rained and do a burnout on some slabs or similar... it gets all the arena dust etc out of the wheels and makes them super grippy again.

Which compound tyre are you going for jamie? Ive got about 12 off the orange 98mm wheels kicking about with the hex hole... so if you go 98mm dont bother buying spares as i bring all mine to the champs and your welcome to use them should urse get smushed... im going to buy a few sets of the blue this year though and see if they last a bit longer.

[Eventorizon]

I went down to our local engineering shop and found these.

2014-01-07 14.48.19.jpg

They are a exact match for the 4 long bolts on the gearbox's. I think they were £4, but at least I will always be able to get my gearbox's apart of I need to. I would have to be left stranded over such a simple thing. I also got a load of circlips from uni before I went so I have quite a few of those spare.

Actually, on this subject, one of the gearbox's was supplied with the wrong mod of gear to go on the motor shaft. I was just going to cut the gear off but where can I find a replacement? I have emailed them twice with no response.