HardWired II

[QUOTE=Flag Captured;453426]

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Originally Posted by Flag Captured

I'm not sure how the stuff you use stacks up to Hardox, Glen, but I'm not sure I'd like to try 3.2mm knowing that!

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After bashing away at Demon for years with hardly any dents to show for it, the steel must be the hardest known to mankind! Given the weight of the weapon, motor and batteries to drive it, I think you are stuck with 3.2mm Hardox. Its not all bad though, you can use clever design to make the frame stronger.

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Originally Posted by Flag Captured

I don't want to make the whole thing so shock absorbent that I end up losing a lot of the power out of the bar

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Its actually the other way around. If you make the frame really stiff in the vertical direction, virtually all the energy will go into the opponent. If the bot runs on skid pads at the front, place them right under the weapon support columns and the path of the impact force will look like this:

http://www.nswrfc.org/Nick/impact.jpg

As long nothing along that path bends, the other bot will be heading into orbit :lol:.

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Originally Posted by Flag Captured

I'm hoping to stick a bearing in that outer side, so might end up with 10mm between the wheel an the outer edge, might be alright...

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That should be fine; if not, you can always increase the floor clearance a little to compensate.

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Originally Posted by Flag Captured

Something I will ask though - is there a calculation that can be use to determine say, what thickness of material you'd need to use for a set of bulkheads, or is it more just trying it out and seeing how it gets on?

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Top-end CAD programs have a feature called Finite Element Analysis (FEA) that can analyse stresses and predict how much parts will bend or break. You can then tweak the design and rerun the FEA until you are happy (or bored :))

It could well be the case I'm stuck with it! Though when I've got it all sketched up properly (I am actually doing that, just hideously slowly and keep having to start over haha) I'll do some calculations on the weight and figure out what I've got left. I'm not entirely averse to using brushless drive if it proves a lot lighter, but for now I'm just sticking with brushed - bridge I can cross when I get to it, and all! If I've got enough weight left for 5mm hardox or something, then I'll be sorted, if not then clever designs will have to come out - I'd rather just have thicker armour because clever design work is not a strong point of mine, see Balsa Steel and HardWired 1 haha

Up to now, it's looking like the main body will be about 6-700mm wide which is probably an awful lot but it should help keep it stable enough... It'll probably be about 250-300mm long too, but these are just ballpark figures for now. Might actually try and cardboard my parts list up sometime and set it all out, see if I can get it all arranged passably!


Ahh yeah, I see the logic there! My worry was making it too solid that it bends, if you get me - hence adding a bit of shock absorbing stuff in it, hopefully a static shaft with 3mm wall box section bulkheads (totally not an idea borrowed from Demon) will be strong enough though. Failing that, I'll go 5mm wall!

Yeah, I've seen that used before - problem being I can't CAD haha! It's handy to note though, would be very useful to determine what I need to do to stop it from imploding on impact! The phrase 'biting off more than I can chew' definitely springs to mind here, but if it works I reckon it'll be pretty scary! Or at least, I hope it will be anyway...

Another thing I've amended is that the bar will now be just a standard one with heavy teeth as opposed to single tooth, for now at least - I feel it might work just that little bit better in terms of having the weight at the end of the bar for more kinetic energy (?)

Another question actually, is there a formula for working out what power/speed motor I'd need to spin this bar up to a given RPM or is it just rough estimation?

Roughly how expensive do you reckon this would end up being?

Counting the inevitable enormous muck-up that results in me having to build it again from scratch?

A lot. Most of that will go into batteries and having the bar cut I reckon. The hardox for the main body won't be too expensive I'd imagine and the bulkheads are just mild steel box section which shouldn't be too expensive either. It'll definitely cost more than HardWired 2 did, but as of now I really don't know given that I haven't finalised the parts yet...

With the build of Caliope and Valkiri 2 in mind, I guess £500 , with all the parts new, is realistic.

Don't forget that huge weapon motor & ESC!

That might be a reasonable estimate Mario, just might have to add an extra £100 or so maybe considering I'll have to have it welded up for me and all that!

The weapon motor and ESC are both something I'm still looking at though haha, can't seem to be able to find anything suitable enough to get it up to 7000... An NTM 50-60 may do the job but I'm worried with it being a 4kg bar with all the weight at the tips. I may have bitten off way more than I can chew, in all honesty...

I mean, if it comes to it I'll stick in one of those ludicrous Scorpion motors and a 12s pack, but I want to be able to save as much weight for structure as possible because I'll need it! Also money, the scorpion ones are a little out of my budget due to recent developments in just general life haha

I'd like to say an NTM on 6s would mean I could keep everything relatively cheap and simple (still go dual packs for the drive voltage at maybe 4s, no getting round that I think) but I don't know if it'd be up to the task. People have told me before that the NTMs are torquey as they get but I'm not sure how happy it would be spinning this bar up on near as damn it a 1:1 ratio!

Actually, just a thought... Maybe I'm overcooking the bar speed? Perhaps aiming for something more like 4/5000rpm would be dangerous still, given the weight and all that being towards the outer edges of the spinning mass (aiming for 1.5kg teeth of possible). I'd still like to push 7k if I can but I'm starting to think that I may be asking a lot more than is actually possible. Even more so considering my own abilities.

It could be doing 1000rpm and still be "dangerous". A £30 NTM(380kv) on 6s, at 2:1, would spin this up violently. It'd be scraping 4,000rpm which is immense. 7k really is unnecessary. The biggest hit you could theoretically get is greater, yes, but if you'll forgive the (really) awful analogy it's like an African elephant and an Asain elephant. One is bigger, but they're both still elephants, ya kno.

If the 50/60 NTM is not powerfull enough, and the Scorpions a tad to expensive, have a look at this one.

http://alienpowersystem.com/shop/63m...-170kv-3200wa/

@12S it runs 7500 rpm

And yes, at full speed turning will become near impossible.

Concerning drive. Defector has run with a 3S 2200mAh pack, and had juice left after a fight.
Caliope does the same, even with the failed Brushless drive.