Half Slips and Double Slips

In UK practice the minimum angle for a diamond with fixed Ks was 1:8 (note larger numbers means smaller angles) in bullhead track. Modern practice in flat bottom rail is a minimum of 1:7.5 so 1:8 would also be built with movable blades, ie. a switch diamond. Keith

Its actually to try and reduce the effects of heat from the sun on the rails. The tollerances for switched diamonds are marginal at best and so even something minor like the expansion of the rail in the sun (in jointed track) can cause failures.

HTH Jeff.

In message , Keith writes

Sorry, you're right. I meant 1 in 8.

Incidentally, with "short-angle diamonds" (those with crossing angle less than 1 in 2) all the running rails through the diamond are vertical, rather than inclined at 1 in 20 as usual.

In message , jeff mcghie writes

Yes it does. I knew there had to be a "proper" reason for it.

Standard 113A flatbottom rail design is for vertical rails within all switch and crossing work, the newer CEN60 and older flatbottom designs are (were) inclined thou.

Jeff.

Getting confused here. Do you mean angles less than 1 in 2, or angles of

1 in less than 2? The former doesn't make sense to me, but I may be missing something.

Ken.

That's the way it was written in the source I took it from.

It's the second of your options. 1 in 2 is an angle of 26 1/2 degrees, so "less than 1 in 2" means "more than 26 1/2 degrees"

Try using parentheses, as in (less than 1) in 2, for example 0.5 in 2 which is equivalent to 1 in 4. We don't express "1 in n" angles that way, so it isn't that, but we could if we wanted to, and lots of people would get confused.

Right. It would never occur to me to say an angle of less than x in y when I meant a larger angle. Would you care to identify your source if you can recall it?

Ken.

Usefull spread sheet Terry , thankyou. It may be semantics but for my money there are only check rails on the K crossing. I've had a look at my slips today, built with home made gauges, and the dimensions are identical after two plus years outside. I cannot see how they are more difficult to get right. But I am using coarse O and the original poster may have talking 16.5mm, which could be more fiddly.

Ken.

GWR Switch and Crossing Practice, by David J Smith

Thankyou Jane. I'll take a trip to ABE books and see if I can find a copy.

Ken.

Hi Ken,

Full details at:

regards,

Martin.

---------- email: snipped-for-privacy@templot.com web:

Thanks Martin, ABEbooks couldn't offer anything.

Ken.

Ugh. Tell me about it! My Dad and I had one fail at an exhibition, albeit not on a double slip (which caused another nightmare in another show). Luckily, the point wasn't crucial to the operation of the layout and failed at a time when nobody was watching. It still took a lot of faffing about by myself and a jewellers' screwdriver to 'persuade' the spring back into its place.