Laying Exactoscale Chairs

[animotion]

I am about to embark on building an EM gauge layout and have been gathering as much information as possible with regards to track building. I will be using Exactoscale code 75 bullhead rail with four bolt chairs. I have been looking at several forums on track building and came across an article in the scalefour forum by David Thorpe regarding track laying. The track gauges the  EM society supplied me were a mixture with some by DCC Concepts. I was not aware that you should use Exactoscale gauges with exact scale chairs because the chairs sit on the sleepers at a slight angle or are we only talking about P4 here. I would be grateful if any modellers out there could clarify if I should be concerned over this matter. Here is what David Thorpe said.
“Without wishing to worry you, do make sure that you are using an appropriate track gauge when laying track using Exactoscale chairs. The reason is that these chairs hold the rail at a prototypical angle, with the top of the rail canting slightly in. If you use a gauge (as I did) that holds the rail straight up and then put a weight on it to hold it in place while the MEK sets (as I did!) you may find that when you remove the gauge the rail will gradually begin to cant inwards, leading to gauge narrowing. I had to carry pout a lot of remedial work to several sets of points because of this. It seems that you need a gauge such as an Exactoscale roller one that only holds the top of the rail. If the gauge holds both the top of the rail and the foot, as some do (including, I believe, the Society ones), then after removal the chairs may relax, leading to gauge narrowing.”

[Guy Rixon]

It's nothing to do with P4 vs. EM. The problem that Dave T. describes applies to both gauges because the same chairs are used for both gauges. AFAIK, the EM tolerances aren't loose enough to overcome this.

 

The DCCconcepts 3-point gauge for EM looks like the kind that avoids the problem by only gripping the rail head. It's harder to tell from the picture of their roller gauge, but that looks OK too. If you have either of these you can test the matter: put in a loose rail and if it can rotate in the groove a little around the axis of the head then its should be OK. If it grips the rail with the web at a fixed angle then you have problems.

 

The gauge-narrowing problem can catch you out on curved, plain line as well as in turnouts.

[bécasse]

You will be using exactly the same chairs as in P4 so the same potential problem exists, especially through pointwork, although tolerances are effectively a little greater in EM. Gauges which only hold the head of the rail may be OK provided that they do not hold the rail excessively tightly; you can check this yourself by seeing whether you can tilt a small piece of rail slightly while it is in the gauge.

 

When threading rail on to the chairs, read carefully the instructions about chamfering the web of the rail to make the task easier (or rather a little less difficult!) but you will probably find that you will still bust some chairs as you try to thread them on to the rail. Keep any that you do bust as they can be useful in odd places on pointwork and you may also get away with using the odd one or two on straight trackwork.

[animotion]

Thanks for the feedback. I had no idea that the Exactoscale chairs were prototypically made to hold the rail at a slight angle which I believe is 1:20. I wonder if the C&L chairs are also made to represent this as well? 

[Miss Prism]

5 hours ago, animotion said:

I wonder if the C&L chairs are also made to represent this as well? 

 

Yes.