Thread: Ensign Wedgeley Crusher (FW Sportsman)

Predictably, we went right to the wire with this build again. Didn't help that I had a stinking cold the week before Robodojo... I woke up on the Friday morning and really just felt like going beck to sleep, but I had a clear day and there was a decent chance the Hackspace would be busy on Saturday so I wanted to get cracking.

FRIDAY 10th MAY
As mentioned, I woke up feeling like cr*p. I decided that I'd be better off spending the morning sitting down so I got started on the electrics for the new linac. As mentioned previously, the linac runs off another Argos drill motor, to minimise the number of spares we have to carry. We considered using a relay switch to run it but a cheap ESC isn't much different price-wise and offers some finer control if needed.

My main job for Friday was thus to put some Anderson connectors and ring terminals onto the ESC, and then to wire up some microswitches to use as end stops. I'm quite pleased with these, since 1. I figured out how to set them up from scratch then found the exact same circuit diagram I'd sketched on the Gimson website, and 2. they worked first time, i.e., I had the diodes the right way round and hadn't cooked either of them while soldering.

If anyone is interested and doesn't already know, this is how the limit switches are wired up:



I spent a few hours tinkering with all this lot, all the while lamenting the fact that I'd seemingly forgotten how to solder. Having completed almost everything, I decided to maybe see if I'd possibly just chosen a slightly duff iron, so I tried the one on the next bench and suddenly soldering was easy again. Would've taken about half the time otherwise, but I quite enjoyed the sitting down aspect of the process so it wasn't a dead loss.

I then spent the rest of the day making an adaptor to fit to the leadscrew nut. Basically a doofy do that stops the nut spinning and provides an attachment to transmit the axial/linear force out to the rest of the jaw mechanism. We'd got a bunch of little bits of aluminium so I made a little frame thing that fits around the nut:



(Image taken after the event, hence the rest of the mechanism is also there, as are the limit switches.)

Although this worked fine, I felt like I entered some kind of transcendental state of bodging while making these parts, as not a single face I cut managed to be at right angles or indeed anything resembling flat. I eventually give up filing it and let it be, lest I file it into nonexistence.

SATURDAY 11th MAY
Despite much procrastination, we were in reasonable shape going into the last day of building. All three of us were free for the whole day so we headed to Hackspace early in the morning (by which I mean, about 9AM) to get started. Remaining jobs at this point were:

• Finish the nut fixture which needed a couple of extra hole drilling and tapping
• Mount the limit switches to the linac frame
• Try to beef up the mounting for the motor and bearings of the linac (currently just CNC'd HDPE)
• Put some armour over the linac
• Assemble the lower jaw/front fork and fit to the chassis - fairly simple job, quite a few holes to drill/tap
• Add some "tailfins" to prevent wheelying and hopefully reduce the chance of getting flipped
• Add some spring steel strip to the front of the wedge to stop the HDPE getting chipped
• Cut/drill/mount all the linkages and parts for the upper jaw and mechanism
• Cover for the sharp ends of the forks and a locking system

Some of these jobs were optional, and some could be done in "tinkering time", to borrow once more from Scrapheap Challenge - that is to say, in a yet more bigger rush and shoddier manner on the morning of the competition.

I had ordered most of the aluminium for the weapon linkages already cut to size from Metals4u - they don't appear to charge (much) for cutting so most of the pieces were only a quid or so. Simon took on the job of drilling holes in them and filing the corners down, and of cutting and grinding the front forks to shape (they're made of cheap mild steel, probably not up to much in full combat but fine for what we need). Meanwhile, Becky discovered the joys of tapping, as many threaded holes were required for the lower jaw assembly.

We decided to scrap the idea of cladding the wedge in spring steel for now, as it unsurprisingly turned out to be hard to drill. Reading around, I will give it a try with a 90° milling bit that I bought for CNC engraving. We also had to drop the tailfins, as it turned out they would be harder to mount than originally thought and might have interfered with accessing the link.

The extra bits on the linac were also left off, as we just didn't have time to finish. However, we got pretty much everything else done!

Dry fitting various parts. Note the carefully engineered blocks to wedge the motors in place:



Test fitting lower jaw/weapon mount:



Lower jaw in place:



Linkage integration:



COMPLETED WEDGELEY:



Previous Wedgeley for direct comparison: https://imgur.com/4Fhkj7v

In my last update I made, or at least implied, a bold claim...

Originally Posted by McMullet

… the crusher (which will undoubtedly destroy exclusively itself if ever called upon to crush anything more substantial than a coke can)

... namely, that the crushing mechanism would NOT destroy itself if called upon to crush anything OF EQUAL OR LESSER substantialness than a coke can, and that is would INDEED CRUSH SUCH A THING.

I AM NOTHING IF NOT A MAN OF MY WORD:



I was seriously terrified at this point that the whole thing would fall apart. As it turns out, the shaft collars aren't quite up to the axial forces and will start to displace if faced with an excessively resistant foe (e.g., a bean tin), so for future iterations we'll need to modify that part of the machine (might see if my dad can just weld if for us...).

POST-EVENT
I will write up our experiences at the event shortly, but here's the final final build, with a few additions made on the day. Obviously there's a spoiler here that Wedgeley survived intact, but it was only a sportsman competition so that shouldn't come as too much of a surprise.

This is the final form, with armour over the linac, to protect from axes and when flipped over:



All just scrap bits screwed in place.

Skid bars fitted to prevent wheelies - these were some very conveniently-shaped bits from the offcuts bag!



Finally, the new weapon is designed to come off as one sub-assembly - just an Anderson connector and a couple of bolts and it slides off:



Obviously, that also means if a couple of bolts break, it falls off, but we live in an imperfect world. This has the advantage that we can take the weapon off and drive it (relatively) safely around the house. I've been experimenting with various dual rate/exponential settings to make it more driveable in future.

Cheers!