On one of the Shays:

http://www.railpictures.net/viewphoto.php?id=166987

Not having grown up around steam I have a few questions;

1) The staybolts.. are they holding the top of the firebox in place or the boiler walls in place?

2) Why are so many needed? Is there a built in "factor of safety" to have so many?

3) The section of the boiler in front of the firebox (where the flues are) does not have staybolts. Why are they not needed there?

4) Staybolt material. Are they just steel, or can stainless steel or some other alloy material, less sustainable to corrosion, be used?

cjvrr

[quote="cjvrr"]Not having grown up around steam I have a few questions;

1) The staybolts.. are they holding the top of the firebox in place or the boiler walls in place?

2) Why are so many needed? Is there a built in "factor of safety" to have so many?

3) The section of the boiler in front of the firebox (where the flues are) does not have staybolts. Why are they not needed there?

4) Staybolt material. Are they just steel, or can stainless steel or some other alloy material, less sustainable to corrosion, be used?

cjvrr[/quote]

The staybolts are holding the flat areas. The flat areas have to be stayed from the pressure otherwise they will have a tendency to want to be round. A round vessel is not stayed, only flat areas.

There are calculation for the amount of needed staybolts and the angle and spacing. This assures that the flat areas do not bulge from the pressure. Yes the calculation provides for a factor of safety of 4 times under FRA. Under ASME on new construction boilers this is 3 times.

The rounded area or knuckle is not stayed. This area is designed for some flexing due to heat expansion.

Staybolt materials are generally specified by tensile, elongation etc. When you read the spec then this gives you a choice of materials that may be used as long as it falls into the range outlined by the spec. I believe that A31 and A36 are used. One other but I can not think of it offhand.

what is the black pipe above the drop light foor? Obvisouly it wasn't there when under steam.
Thanks

The black pipe appears to be capped off for some reason. It could be simply something slid into place as a brace during the boiler work. The lack of scale makes this plausible but then it is hung by a permanent bracket. Could then be an auxiliary steam supply pipe taking steam for a manifold, appliance, turbo gen or something.. The worklight is hanging from a disconnected backhead brace.

My guess is that the black pipe would house the throttle rod, as I am not aware of a shay with a front end throttle. Note that it ends under the dome where the throttle casting would be mounted. Perhaps one of the guys who has recently been inside a boiler can confirm.

It sure does appear to be just that, a housing/guide for the throttle rod. The lack of scale threw me but the pipe could have been replaced.

The black pipe is the auxiliary dry pipe that is running back to the turret. It is probably temporarily capped to keep trash out of it and so you don't get scraped up too badly climbing in and out through the dome. It is a tight fit even with the throttle out of your way.

The throttle rod is the rod below it with the drop light hanging from it. You can see the hole on the end to connect it to the linkage.

JohnB

Adam,

Thank you for the informative response!

Chris

Think of the section at the rear of the boiler as a horseshoe as might be hung over a doorway, open at the bottom. Inside the horseshoe is the firebox sending out plenty of heat. The space between the two walls is normally filled with water to be boiled, but at the same pressure as shown on the steam gauge, only liquid. That pressure will want to push the metal in toward the fire, just as it wants to push the outside the other way. The staybolts hold that together in a sort of balance. The exhaust gasses from the fire pass through the flues (tubes) also providing heating surface for boiling.

At the bottom of the horseshoe is an area referred to as the mud ring, and this if often an area of concern on older boilers. Minerals and other sediment from the water concentrate and collect in the water side as pure steam is boiled off and the mud ring provides a relatively less turbulent zone for them to collect. And if properly operated that is 'blown down' by slowly opening a valve and ejecting any accumulated sludge.

Do not do it often enough and corrosion presents itself, especially when the boiler is down between firings. Do it too often and you waste fuel, and perhaps subject the boiler to a minor shock cycle needlessly.

Bob Kutella

Thank you all for sharing your endlees bits of information. my wife and I spent 2 days at Cass this past October. and found the people there to be very freindly and helpful. I was able to ride the cab of #11, Life is Good!
Dave

That is correct.

The pipe supplies steam to the turret (the manifold that in turn supplies steam to the locomotive's appliances). In operation, there is a 90 degree elbow on the end of the pipe where the cap is which points up into the dome, and another length of pipe threaded into it that sticks up into the top of the dome to get the dryest steam possible.

The rod is indeed the throttle control rod. It goes through a packing gland at the firebox end of the boiler into the cab, where is attaches to the throttle handle.

What an interesting thread.

Can someone describe the difference between this and a front end throttle? Is a front end throttle what I remember seeing on N&W 611 - a linkage running along the outside of the boiler?

Thanks,

Bob

This engine is equipped with a dome throttle which is a single poppet on the end of the dry pipe. The throttle poppet itself has two seats and resembles a spool. In this arrangement the dry pipe then is a pressure item. If the dry pipe fails then steam is in the units and cylinders and no matter what you do you are not going to shut it off unless there is a shutoff way down stream.

Yes the linkage along the side of the boiler is a sign of a front end throttle.
The difference is that the front end throttle has multiple poppet valves which open progressively by a cam. The front end throttle also has a balancing chamber to help overcome the boiler pressure holding the valves closed. The reason for multiple valves is that it takes much more steam to operate a large engine and so the total opening inlet must be larger. Also this can not be accomplished with a single large valve as there would not be any fine control over the steam. Having multiple valves opening progressively allows the control and prevents the drivers from running away everytime the throttle is cracked open.

I recently inspected a really beautiful 0-6-0 with a multiple front end throttle, and other wonderful modern conveniences of the 1930's that one would normally expect to see on "big engines' too. I hope it will be restored and used in the not too distant future - a great size and in very good restorable condition.

dave