Dennis -

Speak for yourself!


Les

I'm hoping for a Q2, myself....

Jeff

I'm not so sure that pre-engineered buildings make much use of cantilevered construction. This whole exercise has been based on adapting standard components, on which the engineering has already been done, to a building that looks like a roundhouse. However, one can certainly obtain shorter stalls by using components from buildings that have different spans. The real question is what does the added complexity of jogs in the rear wall add to cost vs. what does the decrease in square footage save. Example, if we assume a museum has a collection of twelve locomotives that range in length from 60' to 110', which is most cost effective: A custom stall sized to the length of each locomotive? Build the entire house for the longest locomotive, even though two of the shortest won't fit in the same stall and leave either viewing room or walkways? Would two groups of different length stalls be cheaper to build than three groups of different length stalls that more closely match the length of the locos that will occupy them? The answer to those questions would be nice to know at the beginning of design.

Another topic I should touch upon, since this discussion will be searchable far into the future, I hope, is the size of the turntable. We are really doing this design somewhat backwards. We've rather arbitrarily picked a design length to fit some common engines, then reduced the angle of the stalls, and thus the span, and cost, of the roof to the bare minimum, without giving much thought to the turntable. Few groups are going to design and fabricate a custom turntable; they are going to use what they can acquire. The table may be smaller than what is really needed to turn engines that will physically fit in the house, and that's OK. I could certainly support an argument for putting a 90' turntable in front of a 120' long house, even if that meant the longest engines had to be disconnected from their tenders and moved in two parts; this is, after all, a display building, not an operating terminal, at least not for the largest power. There is a danger, however, that needs to be looked at before much design work is done.

For any given angular displacement of the stall tracks, there is a minimum length turntable. This is a function of the track gauge. If the table is too small, the rails need to cross before they reach the pit wall. I'm sure most of us have seen a roundhouse somewhere that had this situation, if not, here is an example:



The problem is, these aren't standard switch frogs; they need to be built to an angle that matches the track arrangement in the house. You will never find them, you will have to have them custom fabricated. You will need one less than the total number of stalls. I dare say the cost of these frogs will likely be more than the cost of increasing the stall spacing, and thus the width of the roof. By all means, do a detailed layout before spending any money on building design.

Since I'm sitting in front of my CAD station all day anyway, I did a quick layout to determine the minimum angle between stalls that can be used with any given turntable before this situation develops. The following table is based on standard 4'-8.5" track gauge and rail with a 3" wide head, allowing the rail base to be clipped, if needed, but not the head:

Length of Table..... Minimum Angle of Stalls
120' ....................5.25*
110' ....................5.5*
100' ....................6*
90' .....................6.75*
80' .....................7.5*
70' .....................8.75*
60' .....................10*
50' .....................12*

For any given stall angle, a longer turntable will, of course, intersect the stall tracks where they are further apart.

This has also answered the question I had as to why older, shorter roundhouses tended to have wider stall spacing.

If the layout allows it, locomotives that are too long for the turntable
are in stalls aligned with the turntable leads and just use the turntable as a bridge across the pit.

-Hudson

And, by the way, ALWAYS build more than one lead - one derailment on the only lead can ruin your day.

dave

Hudson -

That's fine, as long as the locomotives don't have to be turned.

Les