plastic chair systems not holding rails in slide chairs

[nigelcliffe]

I've been doing some fettling to the group layout. Two turnouts are built with plastic chairs onto plastic sleepers, the turnouts are built in situ onto Templot plans. I've noticed a problem where the rail runs on slide chairs near the blades - as the rail is unsupported on its inside, it can drift inwards, thus reducing the track gauge and derailing light stock (heavy stock seems to push the rail back against the chairs). I've checked the actual gauge very carefully, its correct if the rail were resting against the chairs, but under gauge if it springs inwards.

This seems a serious problem and there does not appear to be an obvious way to rectify - I think I'm going to end up drilling some 0.3 or 0.4mm holes and driving in fine stiff wire "pins" to the foot of the rail to locate the rail against the chair and hold the track gauge.

If I were starting again on these turnouts, then ply+rivet and soldering rail to the rivets would seem sensible where the slide chairs are located.

Anyone else seen this problem and got any comments on solutions ?


- Nigel

[Andy C]

Is the problem particularly on the curved stock rail? I had problems some years ago when building using C & L components where not only was there some flex away from the slide chair but under the butanone drying there was some creep in the full chairs sending it marginally out of gauge - all down to tension in the curved rail which although pre bent to shape was still a little off the required radius, the tension in the rail sent it out of gauge.

Two solutions, both used, first was a pin under the web of the rail and a solder job, the second a tiny dab of superglue on the inside face of the slide chair to anchor the rail. The pin whilst most faff was the preferred solution ( abit more robust and permanent) Whilst the superglue did work, after a time of manhandling baseboards it worked loose again.

[Russ Elliott]

I think the fact that the manufacturers offer cast brass slide chairs, to which the unsupported side of the stock rail can be soldered, is confirmation of the existence of the potential problem.

[nigelcliffe]

Andy C - yes, problem worse on the more steeply curved rail, though with close inspection it can be seen to be also present on the straighter rail. The turnouts in question are built on a curve, so no totally straight rail.

Russ - cast chairs onto rivets are clearly a better solution in this area, but I don't fancy the excavation hassles with these turnouts unless forced to do so.


- Nigel

[craig_whilding]

I alraldited the brass slide chairs I used onto the ply sleepers and then soldered them to the rail. This was due to the double height sleeper being unsuitable for a rivet. You might be able to lift the slide chairs in situ and epoxy brass ones down in place?

If i'd used plastic sleepers mainly it'd be easier as you could solder the slide chairs to copperclad.

The Exactoscale turnout I have built as per the kit doesn't seem to have any issues though, I think its because I pushed the curved rail out to slightly less of a radii so its in tension against the chairs.

[Tim V]

It's the fundamental problem with plastic chairs Nigel. They ain't up to the job.

That is why, even today, it is better to use soldered joints in these areas. The prototype used large nuts and bolts, you can't expect any glue to do a similar job.

[andrew jukes]

I'm not sure why this ever needs to be a problem.

If the stock rail is the correct shape to start with, if it's held in the right position and alignment by - at the toe end - a couple of chairs beyond the toe and - at the heel end - by 1P, 2P, etc chairs, and if it's free to move when it expands and so never be in compression, the only loads on it are going to be outwards from wheelsets passing through the switch.

In The P4Track Co kits, good alignment may be helped by the etch under the 2P and 3P chairs, but in any event, if you're fussy about getting rails to be the required shape before building them into the track (something I aim for everywhere) that should be enough. I haven't had a problem (so far!) with stock rails moving inwards.

Incidentally, I don't use the brass slide chairs normally and haven't yet come across a situation where I need to use them. They are available and modellers buy them - but their existence does not demonstrate there is a potential problem when using the plastic chairs (provided all the 'ifs' are dealt with).

Andrew

[jim s-w]

I replace one of the sleepers with a copperclad drilled and a brass pin pushed through - never had a problem with them.

HTH

Jim

[DavidM]

Try using Loctite 480 - this is supposed to be ideal for use with ABS, and seems to do the job well. Keep it in the fridge as it's a little expensive IIRC, but mine is now three years old and still ok.

David