Thursday, 3 January 2008

Wagon suspension and so on

I've done a couple of trial wagon builds over Christmas to assess the relative merits of the MJT (compensated) and Bill Bedford (sprung) etched W-irons.

I started with the MJT ones on a Parkside 16T French type mineral wagon. I've built one of these wagons before and they go together very easily without any problems.

The MJT W-iron etches are very nice although possibly a little over-scale (or is it the Parkside moulded ones that are under-scale?). The thickness of the half-etching makes it a little tricky folding up the smaller bits like the bottom bars with the rivets in.

I cut off the moulded plastic W-irons along with the axleboxes and springs and fixed the new W-irons to the underside of the wagon with impact adhesive. The fixed W-iron required a small piece of plasticard to fill in the gap between the folded-up spacers and provide a flat surface for fixing.

At the same time as fixing the W-irons I also fitted in place the moulded brake hangers and brake gear as these are provided as a one-piece moulding for each side and determine the exact spacing of the wheels.

It was at this point that I realised the whole wagon was sitting too high and I duly had to cut out the floor and reposition it about 1.5mm higher up inside the wagon body (only possible because everything hadn't dried completely solid yet) - a right old mess, although you can't really tell at the end of the day! I should have measured everything up first - well, I certainly will in future - you live and learn!!

I used MJT cast whitemetal replacement axleboxes and springs, with the spring hangers cut off on the compensated axle and then glued seperately to the solebars but with as little gap as possible - the end result once painted is very convincing and not at all noticeable unless you look really hard. I was careful to keep checking that the compensated axle rocked freely at each stage.

I like to fit sprung buffers and coupling hooks, so these went in next. The back of the coupling hooks had to be bent and the springs shortened to fit in the gap between the buffer beam and W-iron which is a bit of a bodge but seems to work ok. I guess I could have cut them down and re-drilled the hole for the split pin.

Finally I fixed in place the brake levers.

Apart from the mess-up over the height of the wagon, a relatively straightforward procedure.

Next it was the turn of the Bill Bedford sprung W-irons. I thought I'd try these on a standard 16T mineral wagon (again from Parkside).

I haven't put one of these kits together before and it turned out to be far less straightforward than the others I've built. The various parts don't seem to fit all that well. Other Parkside kits I've built seem fairly accurate even just going by the mouldings. Some very careful filing was necessary on the body sides and ends to get these properly square (so that the top corners looked half way decent). The instructions say to attach the solebars and then the buffer beams fit in between the ends. Having followed these instructions, using the bufferbeams to determine the solebar spacing I discovered that they were too wide - only very slightly but enough to be noticeable when the wheels and brakegear etc. were positioned in place. The gap between the V-hanger and the brake rods would be far too big. Clearly the bufferbeams required some shortening which I should have figured out first. But by this stage there was no going back.I ended up having to cut the V-hangers off the solebars and re-attach them using some Plasticard packing inside the solebars. Fortunately this isn't too obvious. The other 'fallout' from this was that the small pieces that fit between the wagon sides and solebar under the vertical 'stanchions' either side of the side doors and at each end had to be trimmed to fit the smaller gap there now was.

Anyway, all of that aside...

The Bill Bedford etches are much easier to fold up, being slightly thinner than the MJT ones. I soldered the bearings into the spring carriers (filing away the excess solder afterwards) and fitted the spring wire supplied into the top of the carriers. Then I inserted the bearings into the W-irons, popped the wheels in and that's that.

This time the coupling hooks and springs fit without any modifications needed as I'd left the top of the W-irons flat to the base of the wagon without folding up the edges.

The top of each side of the W-irons is wider than on the rocking type and the spring wire protrudes from either side of this. This means there is only about 4 or 5 mm between the W-iron and the buffer beam which makes it a bit tricky when fitting sprung buffers. I had to bend the ends of the W-iron spring wires at the buffer beam ends so they don't interfere with the backs of the buffers. It's tight but the two don't seem to foul each other.

Also, the moulding that holds the brake gear together had to be severely trimmed to allow it to fit between the W-irons leaving room for the end of the spring wire, which makes it a bit fragile. I suppose if you're using an etched underframe etc. then everything can be soldered together and would fit much easier.

The brakes are only fitted to one side as on the prototype and I fixed a length of brass wire between the two V-hangers using superglue (again, soldering would be easier and less messy if using an etched underframe).

I used cast whitemetal springs and axleboxes again - but in order to allow for the vertical movement of the bearings the axleboxes had to be painstakingly hollowed out using a file with its end ground down. My fingers were about raw when I'd finished! I did try using a minidrill but couldn't find a way of holding the axlebox tightly enough without damaging the detail on the casting. Does anyone make axle-boxes that are already hollowed out?? The axleboxes are then carefully fixed in place with superglue (while the wheels and spring carriers are removed top prevent everything getting jammed up), and finally the brake levers attached.

I guess the next one will be easier! To be fair, it wasn't the W-irons themselves that caused the problems.

Unfortunately I don't yet have any P4 track yet to test the wagons on!

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