Bulkhead material/Thickness for drumspinner/beater/vertical discs

[Runsler]

What material and thickness do you use for your Bulkheads/Weapon mounts on feather vertical spinners?

Was thinking of integrating it into 20mm side armor to save some weight, but i'm quiet unsure by now since i've read about people having problems with mounting rotating shafts into hdpe. Was about drive trains, but still, wouldn't think it's different with the weapon.

[lowndsy]

What sort of weapon is it? An axe / flipper wouldn't always be active so there would be less continuous friction / heat on the axle.

edit: sorry, just saw the vertical spinner bit.

[typhoon_driver]

For a vertical spinner, it's been a few years since I was on the featherweight circuit but generally you want to be looking to keep your bulkheads and armour separate. One good knock to the side of the robot and that can be curtains for your weapon too.

As to material, I wouldn't recommend HDPE for structural members. If you want to stick with plastics then nylon would be the way to go. Metal wise, aluminium would be the recommendation.

Do you have any images of your design to share?

[Runsler]

Sadly not, since most is still only in my head, and the last internal parts (brushless motor + esc for the weapon) just arrived today, so i could only estimate the rest. will start to build a rough design, maybe a wooden frame first to get a better view of what i'm doing and what i need this weekend, or at least hope i'll find the time for it.

My drawings are horrible, and learning cad from zero to bot seemed a bit overkill for the first bot. I know myself good enough i'd tinker forever with that stuff instead of actually building anything.

Basically it's a wedge shape, with a beater on the "back" of the wedge. symmetry no matter if it's on the right side or back, titanium top/bottom plate, HDPE sides (possibly... seemed to be a good idea since i can't wield anything bigger than 10cm and could just screw everything into the HDPE, and it gets back into original form after a hit instead of getting bent. Also replacing a flat sheet of HDPE on each side, with just cutting it into the right shape and drilling some holes in seemed easy replacable. Maybe i should change that, just don't know what else to take instead.) inner frame from thinner plastic just to give every bit a place, a bit like a honeycomb structure with pockets for motors, esc, battery and stuff like that to help the top/bottom plate withstand big hits from hammerbots or maybe even crushers. Two wheels, direct drive on Neptune-28 from ranglebox, getting through both top and bottom plate (but only just). And a third contact to the floor somewhere close to the Weapon, maybe a wedgelet, but i'll take care of that last, i think.

[calumco]

Hey there!
A few years ago I had TS3 which was the best beater featherweight in the country for a couple years a so. That was nylon bulkheads with hardox outer armour which was a great set up but the nylon ended up shattering/splitting against NST - a horizontal spinner.

The best beater these days seems to be conker 3, alumec bulkheads with hardox outer armour and ti top and bottom I believe. Would say that's the way to go for sure.

Need to get TS4 on the go at somepoint! But time/life gets in the way!

[Eventorizon]

Wooo! Conker 3 finally made it!

Anyway, Calum is correct in all that, though it really wasn't cheap. I'd recommend 25mm HDPE. Its cheap, easy to source , easy to work with, it bounces and it doesn't shatter like Nylon. Nylon is the 'engineering' plastic but it doesn't fair well when struck. The base of Conker 1 was Nylon and it shattered in two!

[Runsler]

Sadly i think hardox outer armor might get way too heavy for my design, except i'd make it really, really thin
Maybe if i just have a really thin plastic inner chassis, and fixing top/bottom plate with nutstrips or stuff like that. But with additional aluminium bulkheads that wouldn't leave much weight for the weapon itself.

Already was thinking about mixing some materials, but weight is always an issue, and i'd have no idea how i should bolt a relatively thin outer layer of metal into a thicker plate of plastic without screws sticking out (and being an easy target for horizontal spinners) or cutting screw heads so far they don't hold anything anymore.
Possibly with wielding the screws right on the metal, drilling holes into the plastic and fixing them with nuts from the inside afterwards. But that seems so crude, and my wielding skills are quiet non-existent.


Do you have pictures of TS3?
Also, how did the Nylon shatter? I only know Nylon used for stuff where it's really flexible and wouldn't shatter at all. But then again, i only know Nylon for stuff where it's used really differently.

Edit:
oh wow, even 25mm HDPE? for all the side or just for the bulkheads to reinforce them?
was planning with 20mm by now.
Could i just put 20mm HDPE as side armor, and put a second plate on the inside of that to strenghten the bulkheads where needed? or wouldn't that be any useful and i should better try and make everything 25mm? With everything 25mm, it's just as heavy as taking 3,2mm hardox.
Harder to work with, but maybe worth just taking hardox for everything, then.

[Andy]

in my opinion 25mm hdpe is stronger than 3.2mm hardox, at least for bulkheads and structural parts

[Runsler]

Ah well, for structural purposes i'd share that feeling. As armor, i'm a bit unsure whether "getting chipped away" is better than "getting bend in".

[Andy]

Id say its far better in most ways, unless its for a wedge or something that needs to stay sharp

[Eventorizon]

At this point it comes down to stiffness. If you double a materials thickness, you quadruple its stiffness.

Now a sheet of 3mm HDPE and a sheet of 3mm Hardox... yes, the hardox is stiffer. But with 25mm HDPE... yeah, no contest.

Also remember, something many people forget, Hardox is designed to bend! Its designed to be formed into scoops and buckets so in combat it will bend if hit hard enough.


Go HDPE. Once you have got your design resolved and have a few competitions under your belt, then you can upgrade to Alu bulkheads :-)