Raptor (6kg) Thwackbot

[Runsler]

So, since my Feather project is just way too complicated for a first bot (and even more to finish it in time for the event next weekend in Dortmund) i've got the idea to make something simple and sturdy in a lighter class (that's limited to 12V and some kinds of motors (Outrunners for exampe, or even too big brushed ones) are banned) from the spare parts i got now.

Also got a bit of a challenge involved:
I will go by train to the event, so can't carry much spare parts and/or tools.
The idea now is to make almost everything from HDPE (10 or 20mm) and try to use no bigger/different tools than what i would be able to carry with me so i could replace the hole bot there.

In fact that would be:
a drill
a jigsaw
my pocket knife

and well, that's it with tools. Add some HDPE plates, some screws, a bit of bike tire to give the wheels some grip, and that's enough for a chassis.
Also got a tube of Aluminium around, 23.5mm outer diameter and 1.5mm wall thickness. pre fitted with a wooden core (wanted to make a firestaff of it). I know that stuff can take a beating without breaking/bending.
combine this, and the thwackbot is almost done.
Adding giant wheels of HDPE (30cm diameter) to hopefully keep the electronics out of reach of most spinners, put a roughly triangular steel plate on the end of the pipe (triangular since i won't be get through any armor with something like a thwackbot, but hopefully i can get under some of them and maybe flip/push them a bit with that. Also want to go into spinners with that plate first, using it as a shield to deflect horizontal spinner blades up into the air, hopefully using their energy against themselves before they can shred my wheels.)

Build time one week max, trying to avoid stuff i can't do myself with very limited tools as much as possible.
Stuff to start with:
various HDPE-plates (10 and 20mm thick)
padsaw
drill with different drill bits and stuff
a ruler
a pencil
battery (11.1V (3s) @2600mAh)
esc 4_5 from IBF
550 motors on Ranglebox Neptunes
23.5mm Ali tube with wooden core

Well... that's about it.
need to get the steel plate, and maybe i should try to get some more support on the gearbox shafts, but not sure yet if i can do that and how. Also missing link with LEDs and some other electronic small stuff like cables etc.

Build so far:
RIMG1118.jpg

Well... it certainly looks "handmade". couldn't even see where to saw, since all these plastic crumbs were everywhere. And free hand drilling... just started to learn that! Even learned the hard way by drilling in my own hand...
but it fits, it seems sturdy (to me), and whatever gets damaged: just cut out a new one and replace.

Battery is in the front (and well armored), the tube will come in from the back, splitting "electronics-room" in two parts. Will be secured through the back armor and get into the thinner middle-armor. Will also add a long wood screw to the wooden core, so the hole thing get screwed through the thick middle armor, with the screw between the motors and the tube ending in the thin wall.

currently (with everything in the picture plus top armor screwed on) i am at 2850g.
So plenty of weight left to put into wheels, weapon and maybe some reinforcement for the gearbox axles.


I've got no illusion about the thwackbot-design being outdated since a while, but only real alternatives would be a pusher (needs good traction for what i'd need some experience), a wedge (that would need some precision to build, and at least metal top/bottom), or something too complicated for a first build within a week.

(thanks to ellis here, he's shipping me fitting 12V-motors to replace the 18V ones i wanted to use in my other bot but may not use in this class).

[Runsler]

So... some wheels and holes were made.

RIMG1124.JPG

perspective isn't right here, it actually is about 31.5cm diameter.
you can also see how i made them:
Roughly sawn out the wheels (took a big frying pan to sketch around).
Drilled a 5mm hole in the middle and through my "table" (big cardboard box with a wooden plate on it. not enough space for a real workbench there).
put a screw (M5) through it, to fix everything. used this small wooden block also screwed in the table to stabilize the jigsaw, and tried to hold it as steady as possible against it while turning the wheels with the other hand.

Might not be perfect, but well... hopefully good enough.

Did have some trouble pressing in the nuts to fit them on the gearbox shafts, since i don't own a drill bit with 14.5mm diameter. And no normal drill bit above 11mm diameter fits in the drill. next bigger would be one of these wood drills with a flat head, but that would be 16mm and way too big.
So.... used the 11mm one, a hot air gun and (because i seem unable to find where put my hammer, and having my small anvil at work and not at home) hammered it against the floor with a big monkey wrench.
Let's just say: it is in now. somehow. need to look at it again and straighten things up. Maybe even get a useful drill bit before i try it with the second wheel.

I also tried to put in the Ali tube, but again: no fitting drill bit.
Could have gone 20 or 25mm to fit the 23.5mm tube through. Tried to do it with the 20 and some force, but didn't work.
Maybe should have started with a bigger hole and try to fill it up a bit afterwards, since the 25mm drill is no ordinary one, but one of these flat headed ones for wood. Hard to enlarge an already existing hole with that.

Ah well... 5 more days to go. let's see if that is possible for such a noob^^

[TJR]

Hi, I know this advice comes too late for this build but in the future if you find yourself lacking the right size drill bit, but you have a spade bit (the flat headed ones for wood) that is larger than you need, they can be modified by grinding/filing down the sides until you get the desired size. From my experience this is easier to do on the cheaper ones as they tend to be made of softer steel. Just do your best to try and keep each side equal from the center as they can be quite awkward to use neatly if you end up lopsided.