Boiler design: Girder or Plate Stay Design

[weary]

Can anyone suggest authoritative texts that have calculations or detailed explanations relating to the design, sizing (thickness of stay & width of 'feet' etc.), and positioning (number and location across or along the firebox), of Firebox Crown Girder or Plate Stays for copper boilers in our, model, sizes?

I am also interested in empirical data and calculations comparing the support given by girder or plate stays connected to, and those not connected to, the outer boiler wrapper, and the effect on strength /support of piercing these stays to improve water circulation.

Clearly the above also applies to girder or plate stays on other surfaces such as backheads, tube-plates, etc.

Any suggestions or recommendations of general model boiler design texts are also of interest.

[steam4ian]

G'day Weary

Get yourself a copy of the AMBSC Code Part 1 Copper Boilers. Its available through the Australian Model Engineer web site.

Happy reading
Ian

[weary]

Thanks for your reply and recommendation. I had been thinking of purchasing the AMBSC Code, but will now definitely get a copy. From the 'reviews' on this and other sites it is a 'real page turner that will keep me hooked right to the very last word!'.

Some aspects of model boiler design parameters seems very poorly covered in the Model Engineering Press, even the 'standard texts' are vague on some points.

Having had a look at a number of published boiler designs I have a few ideas of the reasons for this vagueness and also of some of the 'rules of thumb' that seem to be used - but was hoping that there might be a text that clarified things.

(This topic would make a nice brief article in ME. However I suspect that it would have to be an edited article with the various published designers giving their thoughts and methods of calculation anonymously.)

[havoc]

While on the topic of these type of stays, can anyone give an example of a 1:1 engine that used them? They are popular in ME but I can see any used in real life. The only variation I ever saw was a girder that rested on to firebox tubeplate and the backhead firebox plate and was connected with threaded stays to the crown.

[fostergp6nhp]

A lot of traction engines used girders, but it does put a lot of load on the foundation ring.

[steam4ian]

G'day Havoc

My brother who is a nechanical engineer designed a new fire box for the boiler in a paddle steamer, it was a locomotive tyre boiler.

The original had girder stays on the crown with flexible stays to the outer wrapper. My brother replicated that. He was allowed to weld the bottom of the girders to the crown sheet with cutouts for circulation, An interesting aspect was that all the corners were butt joints. Instead of rivets they used Huck Bolts to clamp the inner and outer sheets to the foundation ring.

The boiler is still steaming after 20 years and still passing its annual inspections. The shell must be coming up for 90 years old.

Regards
Ian

[havoc]

Thanks, traction engines are not really my thing so that might explain something.

An interesting aspect was that all the corners were butt joints.

I don't see before me where there are corners on girder stays. Which corners? Do you mean corners like where tube plate meets side of firebox? That would be normal for a welded boiler.

[steam4ian]

G'day Havoc

Some Murray River Paddle steamers did use modified portable engines as power units, there was either geared or belt drive to the paddles.
The larger steamers had a boiler about the size of a good 0-6-0 (LMS 3F) with inclined cylinders directly driving the paddle shaft.

I meant the firebox corners.

Regards
Ian

[havoc]

I meant the firebox corners.

Then that would be normal practice. A lap joint would have to be welded at both sides otherwise you would end up with a capilary between both plates and that isn't good for anything.

[Nigel Bennett]

A lot of "traction engines" had no girder stays at all, relying on pressed-in stiffening of the upper firebox surface such as a diagonal cross (Marshalls of Gainsborough) or a double curve - iimagine the top half of a heart-shape and you have the idea - by Garrett's of Leiston.

As said, it does increase the load on the foundation ring a bit - but that's what it's for.