SLICE Admiral Kathryn M CHAINway

McMullet · 12 April 2024 23:29

It’s a whole EIGHT DAYS before Northdown Havoc so I’m feelng well ahead of the game by starting this log now. The genesis of this idea came from a) seeing Chain B*stard at the Beetle Brawl last year and b) my only-semi-deliberate acquisition of an electric chainsaw. All I needed then was an appropriate Star Trek themed name (to go with Ensign Wedgeley Crusher and Captain Jean-Luc Pick-hard) and the unloved younger sibling of the Next Gen era came to the rescue.

Aaaanyway, the chainsaw I obtained is mains-powered, so I have obtained a Cheap… I mean, SURPass 5055 outrunner to power it, and then it’s all the regular drill motors and whatnot.

Here’s some lovely CAD:

The drill motors direct drive the rear wheels, with an HTD5 belt to the front. Front and rear are the same wheels, but flipped around to give the front a wider track.

Proof of movement being last weekend, I had a rolling chassis up and running at approximately midnight after getting back at 7PM from a wedding in south Wales.

However, there’s still plenty to do. The main vertical bits were machined properly last week, but today I cut the baseplate and front bulkhead, by lasercutting an MDF template and then cutting around it with bandsaws, sanders, routers and so on.

To keep things interesting I did a bit more CNC machining and also some good ol’ manual milling too:

So far nothing is disastrously out of bed, tomorrow is another day in the Hackspace and I’m hoping to get the saw assembly built. Cheers for reading and stay tuned!

McMullet · 22 April 2024 19:00

Sadly time once more got the better of me with this build. However, much fun was still had at BEVs and I did get the Slice Admiral running, albeit sans chainsaw for now.

The next stage after where I left the last post was adding more bits to the chassis:

In order to be able to use the saw effectively, I wanted to make this big scoopy area at the from and this mean the length-wise frame is four pieces on each side, front/read and inner/outer. I am quite please with the way it all fits together.

One of the completely arbitrary decisions I made was to use the same printed part for the front and rear wheels. I guess maybe so I would need fewer spares? Anyway this ensured that both were badly designed for their application. The front wheel runs on an M8 bolt and some bits of aluminium tube, plus a 3D printed spacer that I realised I needed later on and had to glue in place, thus making the “same wheels front and back” thing not work anyway.

The front wheels are idlers and look like this inside:

There’s a spring washer on the end to keep the whole thing together, and the caphead bolt goes all the way through the 15mm HDPE, with a few extra washers.

There are also some spacers for the bit of M10 stud that hold the rest of the outer front/wheelguard bit on, plus some rather aggressive tensioners that were a bit last minute:

The eagle eyed may note that there is a distinct lack of belt here. This is because the “tensioner” (a bunch of 10 and 12 mm bearings) was way too close to the pulley and got jammed up, causing the whole shebang to jam up (event report to follow).

The rear wheels were just glued to some threaded inserts that I originally got for the first ever build of Ensign Wedgeley Crusher, to bodge some scooter wheels onto Argos drills. Sadly gluing them to TPU with Araldite didn’t do the required thing, maybe due to the TPU flexing, maybe the dubious decision to use 5 minute epoxy. Maybe because it was a fundamentally bad idea?

Still, for the first couple of minute Chainway drove like an absolute beast, until the hubs mostly came loose from the wheels. I was quite pleased with my first go at casting urethane tyres:

Need to work on my mould designs a bit but I can see how this is habit forming…

McMullet · 22 April 2024 19:23

That takes us roughly up to the weekend before BEVs. I had a few things to finish at home and at the Hackspace during that week, followed by a Friday morning for last minute tweaks. Due to time taken on wiring and bits and bobs for the other robots, I hadn’t made loads of progress with the saw. The idea I got to was to use the original drive for the saw and connect the outrunner to it via an HTD5 pulley. I had a worm motor to actuate the saw with a beetle ESC to power it (amusingly I didn’t realise until about 11pm on Thursday that I had an older ESC without the limit switches…).

This is what I had sketched out:

The drive pulley was tapped and fitted to the prop shaft that came with the motor. I was an absolute mare to get a tap through but I got there eventually. There’s a 10mm bearing sandwiched in there to take most of the side loads (the back end of the motor would have needed supporting too of course), and the driven pulley is just bolted into the original gear from the saw.

This is where I got to on the day at BEVs:

Between driving/maintaining other robots, entertaining my friend’s small kids and drinking cider I decided to call it a day here. It was a really good prototyping experience though, and I’m super excited to finish it off for the next BEVs event. Just got to not get too distracted by trying to make everything perfect and spangly…

That’s all for now, SAW you later ahahahah