Part 7 – More cranky…

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Even more cranky –┬áMay-June 2010

This next bit was going to be tricky! It is new territory to both Mike, an experienced loco builder, and myself, a completely non experienced loco builder! Mike’s Drewry Class 04s have been tram locomotives with skirting over the wheels, so he hadn’t got to worry about cranks – all axles were linked by heavy motorcycle style chains and it works extremely well and reliably.

Mike’s second Tram loco was bought by Ray Armstead – the man behind the recent revival of the Barking Park Light Railway. Ray says the loco has done some 450 miles during 2009, a remarkable achievement given the loco was built for a few trips round the local track at Lynnsport and there was no intention for it to do that sort of mileage! The benchmark has been set, the Ffesties must match it!

There are a fair few pictures in this section, as they can tell more than any amount of words can! I hope it all makes sense.


To ensure the rods were exactly the right length, these cap shaped jigs (lower two pieces) were made to fit onto the axle ends. The protruding piece is the same diameter as the bearings, and the rod ends, once drilled to size, push straight onto these – these can be applied to the loco in situ to ensure everything is spot-on for length.

The jig highest up in the picture is for spot-drilling the rod ends; the milled out piece is to take the oiler box representation. Once pressed on, the rod ends can be marked using the jig, and then drilled to take the bearing.


The jackshaft drive rods, or coupling rods, were made first and test fitted in place – all worked well and moved as they should!

The rod ends were laser cut for us by Dales, all we had to do was drill out for the bearings and weld them onto the end of the bar section we would use as the main body of the rod, like this…


… and the first attempt looked something like this. The right hand side of the rod had been milled half-thickness, so it would be a half-lap joint. This being a simple method of allowing flex and our first try-out.


The first attempt at a side rod, mounted on top of the cap jigs shown earlier. This was tried all ways and on both sides of the loco to ensure the rods were the correct length.


The first rod has its half-lap joint marked ready for drilling and pinning.


This screw-headed bolt was threaded into the hole and testing could begin, once some pins were made.

These were made by myself on the lathe, and was my second or third serious turning effort and I am rather pleased to have made them within a thou each time. The front right one is an early test out and wasn’t quite the right size on the end retaining cap. As explained on an earlier page, the narrowest part pushes into the crank body, then there is the diameter for the coupling rod bearing and then the outer retaining cap for the whole assembly. The middle axle has longer pins with a second section for a bearing, which is for the connecting rod from the jackshaft.


The plan is to spot weld the pin to the crank from the back once all the rods and bearings are in place and working; thought was given to tapping it and putting a nut on but there isn’t much space to play with – remember this loco is not a scale model and is about half the size of one! Should a bearing need to be changed (unlikely) the weld will have to be milled/drilled off and the pin can be pushed out.

The cranks were put on and bolted up tight, the rods put on. The half lap joint to this design didn’t work as well as we had hoped – a little bit of give had been designed into it, but evidently too much as the rods went skewed to each other when the jackshaft was being turned over by hand. This may have been down to only having one set of rods on; having the second set on would probably have kept it more in line. However, studying of photos of other 7.25″ locomotives led us onto this design, which we feel will be more stable…


The joint this time is on the bearing pin, not flapping about a couple of inches off-centre. We feel more confident with this idea, if not totally prototypical for Harlech and Criccieth.

This picture shows it all better; the joint on the centre axle is over the bearing and all contained on the pin. Will it work though… only one way to find out…


More of the pins were made up in the lathe by myself, was rather pleased with myself getting them to within a thou or two – not bad for an amateur! It can be seen more clearly now how it works; this pin has been part pushed into a crank for illustration purposes. The diameter for the bearing can be seen and the larger cap on the end to retain it all.


Below – the rods for one side all complete and test-fitted in place. The quartering proved tricky, get one crank a degree out and the whole assembly starts clonking noisily and axleboxes rock in their slots. Find the offender and correct it, all is well…


Close up of the centre axle where the coupling rod from the jackshaft joins. The rods were slimmed on the mill for both weight reduction and to allow better clearances.


Don’t look bad, does it!!


The almost completed article. The rods were on both sides and push-fitted in place, not fixed yet – there was to be a track trial to see that all worked out!


The electronics were quite straightforward and a quick to fit affair, so quick that not many photos got taken! Here the main double pole isolator and trip unit can clearly be seen. In the beige box is the relay unit for the two tone horns (a paired set of windyhorns from the local motorspares place) and the main headlight.

The power for these accessories comes from two sealed 12v batteries that fit inside the nose alongside the main traction batteries. Attempts to wire the accessories separate to the main batteries didn’t work out, the small batteries didn’t have the grunt to operate the relay, or so it seems, so the traction batteries are wired in for relay operation, and accessories are powered by the small SLA’s.

In the metal box just visible beneath the beige one is the main brains – the 4QD Vortex. Not as complicated as the Pro 120 originally intended to fit, but more than suitable for the job.



The white connector links is in the line from 4QD to the motor, and is in place for two reasons. Firstly, maintenance. Should the motor ever need to be removed, it is easy to do so and we don’t need to delve into the 4QD case and possibly inflict damage to the board.

Secondly, in case of problems when we get around to the multiple working feature. Both locos are being wired identically, but often things don’t work as they should and if the locos try to play tug-of-war, one of them can have this connector block turned around and reverse polarity to the motor and they should both run in the same direction.

The latter SHOULDN’T happen, but in case Sods Law decides to intervene, we have a solution!

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