May I suggest more hardox? The more parts you get cut the cheaper they are, so you could get a big stack of weapon teeth and spacers (same shape as the teeth but with, uh, no tooth) cut for a few quid each, then you’ll be able to fine tune the size and weight of the tooth by swapping out parts. You could go for a big lump of tool steel, but it’ll be a much more expensive part to make and will likely immediately get chunked and end up out of balance.
So, reading the size requirements for the safety box, the size is 46 by 43 by 38, all in centimetres. The bot, without the teeth, is currently 40cm in diameter. If I add the teeth, to… give it a 2.5 centimetre bite, would I still be within size tolerances fully? (I didn’t include height because I’m more than within height tolerance at this current time.)
Question for the EO’s
My take outside the safety box fitting question is that ~400mm is immense for anything beetle. That’s hobbyweight borderline featherweight size. I have a feeling you’ll be fighting weight and tip speeds
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yeah i agree with harry, i think you really should look at how you can shrink this your really going to struggle to make the shell ridged enough. for example my hobby weight shell spinner is 350mm at the teeth
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Well, I think I’m going to do a little bit of redesigning… again, but hey, that’s the cost of progress and sheer idiocy. And I think I might go ahead and reorient the motor to a horizontal base, like Rhys suggested, but this idea is currently up in the air at the moment, sooo… we’ll see.
Is it even a robot if you haven’t done at least one full redesign before it even exists?
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as someone who’s just decided to rush build a shell spinner for new bloods next month during my finals this is an interesting re-read.
My take having done a bit of work of my own now (although not a shuffle shell) is that the JCR motor is probably not ideal for a non-direct drive setup since it’s really bulky due to huge bearings and so makes the packaging a nightmare. I considered it for mine but I don’t know if it’s quite beefy enough for a full shell. that being said Seth did run it direct on subtraction which has a pretty huge weapon but with a shell where the load is offset I think you’d get extra twisty forces that could make it sad .
I think packaging is the biggest obstacle on shells. I’m aiming for ~ 204mm tooth diameter. a lot lot smaller than your 400-350 range. I’m doing a hubmotor but I think on a friction shell even with your shufflers you can get your diameter down a lott with improved packaging and turning that motor upright.
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Well, with a little bit of changing of the orientation of the motor to run horizontally, and shrinking the outside down, I’ve managed to get the minimum width down to about 365mm without the teeth, so I have a bit of leeway with the teeth length… not much but it’s a lot more than what I had previously. On top of that, I’ll be pocketing the top panel of the shell a little more to bring the weight down just a bit more if needed.
By upright, I assume putting it flat so that the shaft is pointing upwards (no stop that), which I’ve done now. And the reason why it’s still rather large in terms of diameter is more to do with clearance between body and shell, as I still want it to be able to spin even after taking some damage if it does decide to oval itself.
Hm interesting… that sure does seem like a lot of clearance. To me that still sems like an insane diameter and super hard to get in weight. if youve managed it then fair play but thats basically twice the diameter i’m working with at the moment.
Im not sure you need all that radial clearance though, With your two plate design i would have thought that your main concern will be the rings buckling vertically rather than ovalling inwards if that makes sense since they should be strong for hoop stress but theyre quite thin so i wouldve thought you’d be more in danger of high centring yourself if the shell deforms rather than it catching the chassis. especially if youre fighting some kind of vert. That means adding ground clearance though which i know you dont really want to do so its tricky.
My thinking either way would be reducing radial clearance (assuming the inner bot is already as small as it can be) in order to allow for a more robust and stiffer shell since theres the whole r^2 thing in the area of a circle you should be able to make it more stronger-er against the pringle-ing for the same weight (100% real words). Would be interesting to see a top-down / bottom-up view to get a proper look at the layout.
Either way i’m still yet to fight or build my shell so what do i know? twice the diameter deffowill result in a lot more KE but what you have there is probably like the highest KE potential in a beetle in the uk anyway.
The angled tpu filler/armour bits on the shell are pretty neat i will be borrowing.
Well, the inner diameter is roughly 265mm at the little tabs, but I’m just eyeballing things as I’m no physicist or engineer… I’m just doing this for the love of it.
Going against verts is a scary thing, but that’s where spares come into play, as nothing really goes to plan when going into battle… or whatever that damn quote goes.
As for bringing down the weight, I’m looking at where I can take some weight out of the top shell piece and weapon/shaft mount without removing any structural strength out of it, so fingers crossed, it should be alright. Should being the operative word.