RogueTwo Robots

**RogueTwoRobots** · 14th January 2012, 22:05

Update

Ah, the toxic aroma of welding and grinding fumes! Spent most of today welding the endcaps into the drum and making a mount for the brushless motor. My welding's getting better but the angle grinder is currently still my favourite welding accessory

Anyway, got the new endcaps welded into place on the drum. Bolted the timing pulley onto it too and fitted it into the robot. Just the perfect width:

(excuse the lower quality photos, couldn't be bothered going back in to get my proper camera)
Spins much better and a lot more free than the old drum. Spent a bit of time trying to balance it too, and while I think I've made it better, I won't know for sure how good it is until I spin it up. But it seems pretty un-biased for now. With everything bolted/welded in place, the total weight is 2.35kg, which is a bit heavier than the previous assembly. Whether that will make much of a difference, again I won't know until I spin it up/fight it.
Once I've checked the balance, I'll give it a nice coat of paint and probably the spiral I had on the drum back at the 2009 tag champs.

Onto the brushless mount, I've probably went a little overkill with 5mm steel but nothing should be going anywhere!

So there's the main faceplate that bolts to the chassis, to which the brushless motor also bolts. Then, heeding the advice of others, I made up a rear plate to lend some support to the back of the motor. I haven't used a bearing here, just a couple of zinc shaft collets that I had (one welded to the plate, one on the shaft). Despite not being bearings, the shaft spins in them nice and smoothly, so it's enough to make me happy.
I thought about making the mount as entirely one piece - in a U-shape - to have it as one solid unit but I quickly realised that once the motor was in, there would've been no way to get it out. So that's why I opted to do it in two pieces. They need to get tidied up a bit (cut the corners off/down a bit and grind everything so it's all nice and clean) and then I'll get them primed and painted and that'll be another thing ticked off the list.

And finally, made a start on getting the outer armour and wedge back together again. The first step was to alter the design so that rather than having two side pieces that bolted on, it would be one single piece that wrapped around the whole robot. The back panel is all that's done so far:

It's the same 5mm mild steel as used in the brushless mount. Once the sides (4mm hardox) are welded on, I'll cut some pivot points for the rear wedge and weld them onto this back panel. Then hopefully the armour will actually protect the robot, as opposed to it falling off in almost every fight.

So that's that for a day. Should have more updates tomorrow, although not sure what I'll actually focus on, as Carcinus is at the stage of needing re-wired, which is tempting. Either way, at the current rate of progress I'll have both robots finished by mid-February, which will leave over a month for plenty of testing :twisted:

**Mouldy** · 14th January 2012, 22:12

Looking good Jamie- what ratio you using for the drive on the drum?

**RogueTwoRobots** · 14th January 2012, 22:22

Not 100% sure yet on the ratio Dave. The original small pulley I bought gave a 4:1 ratio but with the increased brushless shaft size of 8mm, that pulley is too small in diameter to fit grub screws into for securing in place. So I've yet to buy a new one (gonna have a look on Technobots shortly) but will probably aim nearer to a 2.5:1. Think Boner ran that ratio at the champs and seemed fine, and this drum is almost 2kg lighter.

**Anttazz** · 14th January 2012, 22:43

You'll be just in time to do some more child educating then?

Looking good, will be very interesting to see what sort of power you can get with it now. Looks a lot more secure now too with the new fit, hopefully it runs the way you've wanted it to since you made it, and if it doesn't, you can't blame cutting corners any more :wink:

**PJ-27** · 16th January 2012, 08:34

Looking good Jamie! Give us a spin-up vid soon!

**PJ-27** · 17th January 2012, 16:58

Out of interest, what would you use on the shaft if you didn't have the collets?

I need something similar, that'll stop something moving along a shaft that also doesn't inhibit it spinning too much.

**RogueTwoRobots** · 17th January 2012, 19:04

Umm, probably just bearings. I would have used bearings for the back end of the motor shaft but I wanted to weld it on and I didn't know how well bearings would hold their integrity when subjected to extreme heat.

The collets don't really inhibit spinning much. There's marginally more friction because the shaft is spinning in something that's not moving or has rollers or ball bearings, but it's not particularly noticeable and I'd be surprised if you saw a significant reduction in rpm as a result of using a collet. I was planning on using these 8mm collets as a form of bearing for Paws' spinning disc (although I'll have to buy some more now!)

The only issue I can think of is that to limit movement along the shaft, these collets need to be fixed in place with the supplied grub screw, which then obviously prevents the shaft from rotating in the collet. This can be avoided depending on the application though, so it would depend on how you plan on using them (or mounting them) really.

**PJ-27** · 17th January 2012, 20:23

Hhmm something to think about. Way I see it your trying to reduce friction between the motor and the back mount, while staying fixed to the shaft to act as a spacer.
You need a bearing that has two independently moving faces while being able to spin freely on the shaft, but fixed in place also. :shock:

There must be such a thing. I'm thinking about my own robot design and just noticed your situation was similar.

**RogueTwoRobots** · 17th January 2012, 20:46

The back mount of my motor doesn't actually need the additional collet fixed to the shaft to act as a spacer. The shaft is fixed to the can and a combination of the magnetic attraction and a circlip at the front holds the motor together. I could run the motor with just the front mounting plate holding it on; the back mount is just to add support to try and reduce motor movement during impacts. So there's no lateral movement that needs to be restricted. I just added the second collet to the shaft because there was space for it, and to make it look better :P