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to be honest it mainly depends on mounting (catch points etc), but yes chopping board is alot more brittle. everyone seems to get their hdpe from http://www.directplasticsonline.co.uk
your CAD design looks ok the sides are sloped and if made out of 10-12mm HDPE will stay strong for a bit
tormentas problem was a. the catching point and b. the screws all flew out.
to make your robot stronger you can't have enough bits of support and rivets
if the back of your model is sloped you will be fine
but that was NST (i think- the video wouldn't load) and i doubt the will be any vertical spinners like that at the events you partuciate in
''but that was NST (i think- the video wouldn't load) and i doubt the will be any vertical spinners like that at the events you partuciate in''
Hope not! but you never know... before last year there were no spinners strong enough to bother, but last year there was and it performed well...this year I'd expect more!
That Cad design is not final yet - but those are the lines, as sloped as possible to try deflecting any hard impact
Saw you saw our little 'incident' with Tormenta! Ah yes, well, that. We knew chopping boards had been used for cheap armour by others in the past, and a local shop had loads of sizes, so having purchased some and having played with it a bit, we decided to use it as the main building material for the robot. The kind of stresses you can put on the stuff with your bare hands produced no signs of the material being brittle. The fight against NST was so explosive not because the armour was badly mounted or due to the shape, as said above, but purely because of the brittleness. It simply couldn't take the massive hit from NST, and it shattered like glass.
For Tormenta 2 (being built) we will be using all HDPE. We live in Spain, and having contacted Directplastics they have been able to get sheets of the stuff to where we live. Of course, it wasn't cheap. A single sheet was £20, whilst several was still £20. So, make as much of the order as you can, perhaps buying for future products as well, as you will save money in the long run.
Our little (but growing) experience with HDPE has been 100% positive. A high percentage of UK machines are made with HDPE. It's good stuff. Unlike whatever we used for Tormenta (not sure anyone really knows what chopping board is), HDPE gouges and deforms, as against to shatters. If thick enough and mounted well, you'll be able to take even the biggest of hits.
This isnt too helpful but I can see that most of your issues are being resolved. But, One of the guys my team's partner is at the University of Malta and a member of the IEEE. Sent her the video you posted to see if she knows any of you guys. Small world
Didn't know Tormentia was built like that Ellis, and on that vid it looked a bit more than a ''little 'incident'' But now I think I got myself convinced to go the HDPE way, still waiting for 'directplastics' to reply re. shipping tho...
Do you bother coating the HDPE outer surface with something say Kevlar or something else to protect it from gauging and dents or its nor really worthwhile? Its just a thought...
Hi Tony, probably she'll recognise most of them (if she's not a first year) but she wont recognise me as I never attended Uni I'm the ''support/logistic/mechanical/design'' part of the team, my brother and his mates are the actual team - they'll handle anything which got to do with electrickery and wires! And finally they drive and have all the fun with it!
Do you bother coating the HDPE outer surface with something say Kevlar or something else to protect it from gauging and dents or its nor really worthwhile? Its just a thought...
A few problems there.
HDPE is a tough, soft, resilient,light material, chemicaly resistent against a lot of things, ranging from sodiumhydroxide to aqua regia. But it can't stand Benzene, toluene and Xylene.
And there is the problem. There is no glue, epoxy, paint or other adhesive that sticks to it with any meaningfull strength. Coating it in kevlar won't strengthen it, unless you make the kevlarlayer thick enough, and that beats the idea of using HDPE.
The 2 ways I use to connect 2 HDPE pannels are hot air welding and bolting/screwing the parts together (angle ali can be your friend here)
Right, so that will make my job easier, HDPE all round it will be, not worth the hassle and expense to try to cover it with kevlar which is not going to stick anyway then!
I'll use some light gauge alu box section for the chassis frame and bolt HDPE on to it. Is it easy to cut with a bandsaw or similar?
I also have some acrylic aircraft window panes which I think I'll use as a cover for the flipper top section, it should be out of reach there, and its nice to be able to see the internals without taking anything off!
I know most of you recommend to stay clear of acrylic but I've had these panes tested and they are quite indestructible (after a good beating with a hammer till the hand got numb!)
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