Cicatrix Build Diary

**RogueTwoRobots** · 12th September 2011, 21:59

The weight loss has just been a result of the design. The new drum is shorter, has less teeth and has lighter end-caps whereas the old drum was longer, had four teeth (each being 15mm thick instead of 13mm) and stainless steel endcaps. Not sure what the density of Supralsim 690 is (new drum teeth) compared with Hardox 450 (old drum teeth) but there could be some weight difference there too.

Yeah ideally as much weight in the weapon as possible. The whole robot currently only weighs 11kg I think, so the weight is there to use. Contemplating a beater replacement, making it thick and throwing as much weight as possible into the outer edges.

**PJ-27** · 12th September 2011, 23:08

Make your own build diary Jamie!

Supralsim? Sounds like something from Star Wars. 11kg gives you loads to play with.

**Anttazz** · 12th September 2011, 23:26

No worries Jamie, more interesting than my boring box anyway :sad:

It won't be for long though... Thunderbird 2 is about to switch from pod 1 to pod 2

**Anttazz** · 13th September 2011, 19:04

Beginnings of the drum have arrived in the form of a big chunk of pipe.

Going to order a Speed 900 motor too over the next few days to go with the a relay/battleswitch combo.

Now need to get some teeth made, some sort of shaft and all the gears/pulleys sorted.

I'm guessing something along these lines would be ok?
For the drum: http://www.technobotsonline.com/timing-pulley-25t.html
and for the motor: http://www.technobotsonline.com/timing-pulley-10t.html

**RogueTwoRobots** · 13th September 2011, 20:21

Noice

I'd go for bigger timing pulleys personally; the 10T pulleys are quite small so it can be difficult securing them to the motor shaft. To keep the 2.5:1 ratio, you could go for a 40T pulley on the drum and a 16T pulley on the motor.

I can't wait to see Pod 4, yellow submersible for the win!

**Anttazz** · 30th September 2011, 16:09

Finally rebuild Cicatrix today but its doing some funny things at the moment, using and XL and an XXL, one in each half of the bot to hopefully make it easier to split in half when the drum pod is built. The complicated electronics are undoubtedly the problem, but that seems to have become the robots trademark, it has only worked properly in 1 fight really (out of 6) and it did very badly on that occasion so the more complicated the better I reckon!

As for the drum pod, i've sent off a few emails to see about getting teeth made and was just about to post a thread about which websites were selling the real Speed 900's when I noticed Dave had already done so. Also need to get those pulleys ordered at some point, as well as bearings. What would people recommend for the bearings? Also, have I forgotten anything? Or should I say, what have I forgotten?

**psycho_fling** · 30th September 2011, 18:38

i think im right in saying for bearings it depends on if you are using a dead or live shaft as in will the shaft spin or will the drum spin on a fixed shaft

**RogueTwoRobots** · 30th September 2011, 19:04

Regardless of whether the shaft is fixed or spinning, you'll probably find what you need on http://www.bearingboys.co.uk/

Got needle roller bearings from them for the original Drumroll's drum and they're dirt cheap and haven't failed yet (to my knowledge).
I read reviews that said they're only useful up to a certain RPM and aren't as good at sustaining shock impacts or loads but I much prefer them to typical ball bearings and will be reverting back to them on Drumroll II.

Having a fixed shaft provides much more structural support than having a spinning shaft as you can use it as a connecting rod between your two bulkheads. Having the shaft spinning means that you have bearings inside the bulkheads instead of the drum but it's not as solid a setup. At the time of designing Drumroll, the majority of the American drumbots - and notably the most successful ones - all used fixed shafts, which is why I opted for that method.

Other than that, you need the shaft, the drum, a pulley for the drum, a pulley for the motor and a belt. Don't think you've forgotten anything major. From your drum transmission you'll have your motor, motor controller (ESC, relay etc) which will then link back to the receiver, so nothing missing that I can see.