Hack Hitchin

The Flinger takes shape….

30th Nov 2015

As part of night’s work the Ball Flinger has started to take shape….

Ball Flinger









First stage of assembly


Fly wheel assembly










The flywheel assembled with kevlar anti expansion strengthening.



General view with ball pusher arms installed

Ball pusher servos and arms installed… now to wire it up and attach the speed controllers


Raspberry Pi Zombie

27th Nov 2015

or “How I Fell in DooDoo and Came Up Smelling of Raspberries”

OK. Picture the scene. It’s late on a Friday night, and you’ve been hacking on your Pi Wars robot all evening. It’s been productive. Between you and co-roboteer, you’ve ironed out glitches in your Remote Control code, you’ve soldered up the wiring looms, and you’ve even designed and printed custom parts to mount the pi onto the baseplate you laser cut earlier. You’re robot building machines. Go you. High fives all round.

Flushed with success, you both decide to power up the pi and and take it for a spin. So, you plug in the USB cable that you wired up to that adjustable 5v regulator earlier to step down the power from the lipo battery, and… uh. I’m pretty sure the activity light doesn’t normally do *that* when it’s booting. what the..? yank the power! yank the freaking power!

Welcome To Cockupsville. Population: You


OK. wait a second. what just happened? Well, remember that 5v regulator you wired up earlier? The key word there was adjustable, Dingus. And you didn’t check it, did you? You buzzed every single other thing you soldered, but you forgot to check that the output voltage was actually, y’know, ADJUSTED to 5v. So you just sent how many volts into your Pi? 12? Excellent work. well done. Slow hand clap.

You decide to check the damage, hoping against hope that the Pi just kind of wouldn’t notice that you just rammed 12v up it’s tiny USB port and you can pretend like nothing happened. After all, no blue smoke came out, so … fine, right? Fine. Probably fine.

Except, no. Adjusting the voltage regulator to 5v (triple checked – bit late now, but whatevs) and trying to boot again does nothing. Well, not exactly *nothing*, but only some flickering of the activity light and no actual booting. Saddest of sad faces.

Alas Poor Pi


So that’s that then. You’ve fried your pi. It has gone toes up. Time to give it a viking funeral.

But. BUT. A bit of Googling seems to suggest a few things:

  1. There is such a thing as a polyfuse
  2. They can heal themselves when they’ve tripped.
  3. Actually flipping *HEAL THEMSELVES*
  4. The Pi has one on the USB power input.

So you leave it an hour and, with great hope in your dumb little heart, you plug it in.

Nothing. Just a bunch more flickering. Probing across the polyfuse seems to suggest that it’s maybe a bit better, but stil a loooong way away from being useful as part of a functioning computer. sigh.

M. Night Shyamalan style plot twist


Fast forward two weeks. You’ve nearly forgiven yourself for frying a perfectly innocent Pi. You’ve ordered a replacement and plumbed it in to your Bot, and you’re sitting at your desk idly surfing the web when you see out of the corner of your eye that poor little dead Pi, half hidden under a pile of papers. “I wonder…”, you, um, wonder.

So, you dig out a phone charger and a cable, and you plug it in. <DEITY> be praised! It’s booting. It lives! You’re like the Doctor freaking Frankenstein of consumer electronics! Except that he made a sort of patchwork quilt of chopped up people and you’ve reanimated a credit card sized computer. Same thing apart from that though. Probably.

Step aside Pi Zero, I give you Pi Zombie!


So, there you have it. You too can get away with stuffing 12v into a 5v hole, if you’re very , VERY lucky. But what have we learned? Well, we’ve learned:

  • If someone gives you an adjustable voltage regulator and tells you that it’s set to 5v, don’t believe a damn word of it.
  • Stick your multimeter across EVERYTHING.
  • Raspberry Pis don’t like 12v up them, Corporal Jones.
  • Polyfuses are an actual thing. They freaking HEAL THEMSELVES, people. Insane.
  • Sometimes you can fall in the doodoo and come up smelling of Raspberries.

Development of the ball flinger

26th Nov 2015

So for the skittle challenge we did some thinking and testing and figured that just “nudging” the ball in the direction of the pins wouldnt cut the mustard so to speak. We needed something a tad more energetic. Resident ingenious person Mark quickly rustled up a 3d printed contra-rotating mechanism to give the bowling ball a spot more oomph!

Here are some tests

The first couple of tests used the small ramp but the ball was getting too much air so we swapped things around for the subsequent tests.

Here is another video

Things we learned from these tests:-

  • Lose the ramp. In this case getting air is not good.
  • Balance is your friend. 3D hubs and spindles are not well balanced and cause huge vibration.

It is difficult to see but the rig was difficult to hang on to once the wheels got up to speed. So we went back to the drawing board and Mike took on the task of fashioning Mk2. This time we would have steel shafts and a metal chassis. First models for the Mk2


2015-11-20 (1)



























The second version tidied up a bit…


2015-11-20 (2)














2015-11-20 (3)















Cutting some metal


2015-11-21 (1)


2015-11-21 (2)


































A revised hub was printed without the built in spindles to try and make it less out of balance to reduce vibration.

Mk2 Solid hub


The Mk2 flywheel assemblies are finished and look like this.

 Mk2 Flywheel finishedBoth Mk2 Flywheels finished

There is still quite a lot to do to make the assembly on which the flywheels will be mounted and which will be attached to the front of our robot. Here are some views of the cad of the rest of the assembly.




Ball Flinger Assy Cad Model Iso View Ball Flinger Assy Cad Model Side View Ball Flinger Assy Cad Model Front View

Some laser cutting for the main support arms, 3d printing for the smaller arms and a bit of metal bashing for mounting brackets. Finished off with a bit of wiring. More updates as the assembly comes together.