Team Expat - Beetleweight Adventures

[Ellis]

Having made all sorts of potential beetle designs over the past few months and not having bought anything towards one, today I bit the bullet. Some of these should be on their way from Hong Kong tomorrow. £26 delivered. Not too bad. Hopefully I can say the same about the product in a few week's time.

Other purchases I hope to make soon will include two 10a botbitz, 35mm Banebots wheels, some Nylon, a cheap and cheerful 3s and perhaps an equally cheap and cheerful radio set.

As for what today's design (tomorrow's will probably be different, as yesterday's was very different to today's, and go back a few weeks and designs included drills and threaded rods!) is, I'm off to see what sawblades can be had locally tomorrow. I'll leave it there for now.

Will be nice to be building something again, beetle scale feels perfect for between the featherweight builds.

Hope this goes well!

[Ellis]

Since this post I have ordered a decent tap set for m4 bolts, and a suitable drill. Bought a set of cobalt drill bits, again to have them. Bought the drive speed controllers (10a premium botbitz jobbies). Bought bearings, and Mario has made me a little 12mm silver steel shaft with m6 tapped ends, around which will spin an also ordered, 140mm diametre single tooth disc.

I think that's it.

Next few purchases will most likely be wheels, nuts and bolts, deans, some cable, and a battery.

Once I start getting parts I'll get the nylon for the chassis, and order up the weapon motor stuff.

[harry hills]

Show the people the pretty CAD pictures mate :P

[Ellis]

Right,



...subject to change. Want to change the rear to see if I can make it drive on its back wheels when inverted. That may mean changing the side armour too.

[SamO]

That looks very promising indeed!!!!!!
Good luck with the build

[harry hills]

Nice 1000th post Ellis

[swanaldo]

Nice CAD mate. i do like the 4wd designs too i think you get much more control.

[Ellis]

Thanks guys. Also 1000 posts woo!

Just bought some tiny magnets, 2.2kg pull. Will experiment with having one either side, to help with the gyro forces. About to settle on a battery, too. On this scale the amount of choice is staggering!

Getting excited now.

[swanaldo]

The scope is good at this weight. I thought it would be limited but the components are abundent and design posibilities are practically unlimited. especially with 3d printing and brushless technology.

[Ellis]

Perhaps something like this at the back would be suitable. Provisionally 2mm mild steel, until I can justify getting a sheet of ti, around the 1.5mm thick mark. Point of this is to allow it to drive (after a fashion) whilst inverted. I'd prefer have it so it can drive all the way around the back, so there's a chance it could self-right, but with the rear motors right there I see no method of solid attachment.



Also since the previous post bought 3m of red and 3m of black 20awg wire, a bunch of heatshrink and a 3s 1300mah 35c lipo.

[Ellis]

First few bits and bobs have arrived! Am going to stick pics on photobucket, here - http://s1088.photobucket.com/user/Kr...?sort=3&page=1

So, 4x 1000rpm 12v gearmotors. They are surprisingly heavy, which gives a positive feeling of maybe being not-entirely-unreliable. The shaft spins very smoothly, and the build quality seems reasonable. The shaft has a bit of play in-and-out, but is solid laterally, which is promising. I have yet to hook them up to a supply but so far they look the part.

The weapon bearings also arrived. 5x (will either use 4 or 2 in the weapon, not sure) 12mm ID, 21mm OD, 5mm wide ball bearings. Not much to say, other than I think they'll serve.

Desperately waiting for more goodies now!

[Ellis]

Disc has been cut and is at Mario's currently. That's a 151mm literal diameter, 162mm diameter "bitten", 5mm thick Creusabro 4800 (similar to Hardox 450/500) single tooth, weighing around 360g.

Just did a rough energy calculation, and that looks like this:



The resulting joules figure seems quite high... if anyone can spot a glaring flaw in that mess of imperial figures, let me know. I don't think there's a screw up but ~1750J of energy seems a bit crazy?

edit: for the record, thinking about this I'm fairly sure it's wrong, one day I'll muster the energy to recalculate...

[swanaldo]

Good job the arena has 10mm polycarbonate.

[Ellis]

Coming my way, courtesy of Mario.



That's the disc, a 12mm silver steel shaft (thank you Mario's lathe), and a sheet of ti.

[SamO]

How's the disk made?