It is still a science, sliderules you know, the belpaire would not have been designed if concepts were not worked out.

Hi All

For your reading pleasure from 49 CFR part 230.

§ 230.25 Maximum allowable stress on stays and braces.

The maximum allowable stress per square inch of net cross sectional area on fire box and combustion chamber stays shall be 7,500 psi. The maximum allowable stress per square inch of net cross sectional area on round, rectangular, or gusset braces shall be 9,000 psi.

§ 230.26 Tensile strength of shell plates.

When the tensile strength of steel or wrought-iron shell plates is not known, it shall be taken at 50,000 psi for steel and 45,000 psi for wrought iron.

The above material was taken from the following site.

http://cfr.regstoday.com/49cfr230.aspx#49_CFR_230p24

Robby

I agree with CCDW

Robby

Ye gods, I never saw so much palaver about something reasonably straightforward. The question doesn't call for strains, or properties of materials, or include the factor of safety, or involve any weird math. And if there is a technical glitch in the 'poll' function -- just provide the fricken answer in a short post, and let the interested tot up the results themselves.

The actual Form 4 is not difficult to find. Go to

https://safetydata.fra.dot.gov/Officeof ... forms.aspx

and scroll down to 'Steam Locomotive form 4' This can be viewed or downloaded as a PDF file.

The relevant item under "Calculations" calls for the maximum STRESS on the crown stay under maximum load. In the example, which is happily 'orthogonal' thanks to the Belpaire geometry, you have all the math done for you; it would appear all you have to do is think. Threaded diameters and such are red herrings (except God help you if they are actually lower than that for the thinnest designed section of the staybolt in question!): the only two things of concern are the items in the data table for the stress imposed by the roof against the smallest diameter of the stay, and the stress imposed by the crown against the smallest diameter of the stay.

The Form 4 calls for maximum stress, so the greater area acting on the roof end of a given stay predominates. That is given as 5359.

Now, I would think the load, and hence the maximum stress actually imposed on the stay (assuming no nominal stress at neutral temperature and pressure) would be the *sum* (resultant with forces 180 degrees apart) of the forces exerted by the relevant 'patches' of roof and crown, divided by the minimum cross-sectional area of the staybolt. I do not see this reflected in the calculations given for the poll. No, I have never filled out an actual Form 4 so I don't know if this is a trick 'none of the above'. I look forward to inding out why this assumption is wrong.

Shows why you don't do math with a 101-degree fever. And mistake the force on the staybolt for the stress.

Of course the resultants balance on the staybolt in question - the stress in tension at one 'end' will equal the stress anywhere else in the 1" section.