Team Bitza - Banshee

Hello

After re-configuring what remained of Spinza Mk I into Ankle Biter for last years BW champs I've decided to try building a couple from scratch for this years competition. The first will be Ankle Biter MkII (horizontal bar spinner) and the second will be my first stab at a drum spinner, Banshee.

I wanted to try out a few new ideas with the drum spinner (Innovation pushing tried, tested and reliable options aside!) The first new idea is building suspension into the wheels by remove material around the motor mounts and rely on the Titanium flexing and not bending.

The second idea I could use some advice with, having seen a miniature turbine spun to 80,000 rpm with compressed air I starting thinking if it would be possible to power a spinning weapon with compressed air. My thoughts are to have either a small EDF or 3D printed centrifugal compressor blow high speed/pressurised air into veins to turn the drum. Although there would be a tiny amount of torque I'd hope that the drum would build inertia which could deliver the punch, in a similar way that you may drop the power to the motor before an impact.

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My brain can't work out if this is at all possible, any thoughts much appreciated.

Very nice designs! Can’t wait to see them!

Bad Wolf

Looking good! and great idea with the air turbine, would be awesome to see it work, though I think there would be issues with the torque, and having enough to spin up any weapon in a reasonable time. Though I do not know much about those type of systems so I may very well be wrong!

Good luck

Designs look good but like Andy the air powered drum doesn't sound like something that would work to me.

I just can't imagine it being able to spin up to speed anywhere near fast enough to be competitive so unless you're the worlds best driver you're never going to get a good hit in.

That turbine drum idea is nuts. I have no idea if it would be successful or not but would love to see it come to fruition. Obviously experimentation would be required but it might benefit from a few venturi nozzles on the outlet (perhaps hinged) to accelerate the air flow and allow you to get the optimal angle for air to vane contact. If the drum is well balanced and spins very freely on its mounts then I don't imagine it would take too much to get it turning, at which point momentum becomes your friend.

The turbine drum will probably work if you can get it spinning very freely. Spinup time will be dreadful though. How would you make the turbine blades? Might be possible to get some flat plates cut with slots to slide the blades in at each end, with some thin ti for the blades. If you make the nozzle for the fan/compressor the same size as the blades you might be able to improve the efficiency a bit by focusing all the air. Needs a small gap between nozzle and blades too. Jamie's idea of using venturi nozzles might help too.

cool idea, but would spin down time also be a problem as well ?

So it'll destroy and clean at the same time. It'll be interesting to see what it can do.

There are already solutions for Motors powred by compressed air... Long time since i looked into things like that, but still... Anyway, the real benefit of using compressed air would be to use it for drive, too. Interesting on these motors was, they use (almost) no air while stalled. And since good griP is always the bigger problem than torque...

Uhm, what weight class should that be? Feather? Beetle?

Love the drum idea, I can see it working so interested to see how that turns out. You might have come across it already, but there was a pneumatic spinner in season 5 of Battlebots called The Butcher. It's the only one I can think of though.

Nor sure if that was the one I remember, but there was one in battlebots operating completely on co2 I think, only a very small battery for receiver and controlling the valves. Thing with such motors is, the faster they turn, the more gas they consume.

Thanks for the input. I'm going to give it a go and see how well the EDF can move the drum, ideally I'd like to funnel the air directly onto the veins but I've read EDFs really suffer when restricted. If it comes to it theres enough weight and space to swap the EDF for a conventional belt driven setup.

I've got a slight dilemma at the moment. I bought a length of 25mm x 50mm 7075 a while back that I was planning on making this from, but completely messed up the original design and its too large for the material. I've changed the design to work with what I've got, but it doesn't look as strong and its a little heavier. I can't find any 50mm x 50mm 7075 online, but I can buy 6082 T6 that will work.

Do I machine a worse design from a stronger grade ali, or will the 6082 be good enough? Also I've no experience machine high grade aluminium. I'll be using a small CNC at the school I teach at, would it be worth setting the machine as if it's machining steel or keep it as ali?

Pic 1 + 2 are the original larger sides that could be machined from 6082 T6
Pic 3 + 4 are the ones that I can machine from the 7075

Thanks

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7075 is much stronger, buy a bigger piece and mill it down.
Which machine does your school have?

We have a Denford Novamill at school. I have access to a larger Denford Triac but last time I used it I blew the spindle drive thrysisitor bank, I think because there wasn’t enough power supply to the garage. I’m sure the Triac could handle it, but it’ll be a while until it’s fixed and the electricity supply beefed up.

Any suggestions for 7075 suppliers? I need a 50mm x 50mm x 320mm length. Thanks.

I always buy those Materials at ebay, an then mill it to the right size.

Time for an update on the 2 beetles.

Ankle biter is taking shape nicely, it's a simpler build with far less to make on the CNC mill. Progress was slightly held back when I came across a 1930's lathe on Gumtree, it took some a little coaxing to bring back to life, but it's a nice addition to the garage and came in handy finishing off the ali. The Ti and Hardox were cut at K-cut and I've just a few more parts to fabricate before it's combat ready.

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Banshee is going a fair bit slower, the sides need a bigger mill to fabricate so I'm currently trying to repair the Triac and source a suitable machine vice for it. After much fettling the Ti armour sits together nicely, and the Hardox teeth sit snugly on the drum. Unfortunately the vein holders came back from K-cut without the slits for the veins in them, so having to rethink how to catch the air from the EDF, also the waterjet must have started on the part as each tooth has a notch in, hopefully it wont make it too unbalanced.

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Enjoying the process so far, but it's certainly a much slower way to build than some of the other machines PJ and I have made in the past!

Very nice work!