Joined Up Motion

So having got the pickups working nicely I turned my attention to quartering the wheels and trying the coupling rods. Unfortunately it was at this point that I started to panic.

You may remember from the previous post that I said the live wheels where a little loose on the axles and my plan was to fix these in place using Loctite 243. The reason I started to panic was because I suddenly realised that I had no idea if the Loctite would act as an insulator. If the wheels were insulated from the axle that would be a pain and I'd need to add pickups to the other side, and there isn't much space to do that.

Having used the Loctite to fix the crank pins in place I used my multimeter to check and my worst fears were confirmed; no continuity between the crank pin and the tread of the wheel. After a little bit of head scratching I realised I had a way out.

If you remember, the axles I turned are stepped which makes it easy to set the gauge. It also means that there is contact between the wheel and axle not just within the hole in the wheel but the shoulder on the axle pushes against the back of the wheel. My hope was that if I added the Loctite to the hole from the front of the wheel and then pushed the axle in from the rear it would ensure that there was a nice contact at the back of the wheel. Of course only one way to find out.

Fortunately it all worked nicely. Quartering the wheels was nice and easy (in comparison to every other kit I've built) because I could line up the spokes with the balance weights offset by 90 degrees. In the video the coupling rod is just slotted on, along with some washers to space it from the wheels, so hopefully it works as well once I put on the retaining nuts and trim down the crank pins.

Crank Pins

Before I can start reassembling the chassis I need to complete the wheels by fitting the crank pins. These are simply 14BA bolts slotted through the hole in the wheel.

I'd already prepared the holes (making sure they were wide enough and countersinking the hole so that the face of the screw head was flush with the rear of the wheel) so it was just a case of adding some Loctite 243 into the hole and then pushing the screws through and into place.

The pins are obviously way too long but I'll only cut them down once I've quartered the wheels and added the coupling rods, because if I cut them now it makes adding the retaining nuts more difficult.

Canopus: Biting The Bullet

So I've finally bitten the bullet and permanently attached the coupling rods on Canopus. The good news is that everything still seems to turn freely under power so it doesn't look like I've messed anything up..... phew!

The instructions say to use solder to affix the retaining nuts in place. Experience from building the Quarry Hunslet suggests this doesn't work very well. The problem is that you need to fix the nut before snipping off the excess pin and filling the nut thickness down. When soldering the nuts the solder doesn't penetrate all the way through the nut which means when you start filling it down the first thing you do is file off the solder and the nut becomes loose. On the Quarry Hunslet I secured the coupling rod in place with superglue but still found this difficult as you get so little time to check and adjust things.

For Canopus I took a slightly different approach and have used LOCTITE 243 medium strength threadlocker. This gives me (according to the datasheet) 5 minutes fixture time (that's for brass, it's 10 minutes for stainless steel). Also unlike superglue it is designed to be reversible, assuming you can supply 26 Newton-metres of torque. I used a slip of paper to try and stop the stuff getting anywhere it shouldn't as well as ensuring that I didn't over-tighten the nuts. This seems to have worked well although removing the last bits of paper was a bit of a pain.

I haven't yet removed the excess crank pin or filled down the nut (this was as much stress as I wanted today) but having had it on the rolling rod everything seems to be working nicely. You can tell that the threadlocker is working as previously running in one direction would cause the nuts to work loose which is no longer happening. Now I've got past this point hopefully progress will pick up a little.