ENGINE 39
RMLI Report from Strasburg Observations, April 2009
On Monday, April 8, 2009 I had the pleasure of meeting with Rick Musser, Shop Foreman and Linn Moedinger, President & CMO at the Strasburg Railroad Company. Work is progressing on the firebox of Engine #39. 39’s new roof sheet has been fabricated and work continues to prepare it for installation.
I was happy to meet one of the young craftsmen who work for Strasburg. Mr. Brendan Zeigler has been spending many hours working on the firebox restoration. Brendan is a frequent contributor to the Railway Preservation News Forum and has the ability to explain complex mechanical/engineering concepts in a way the layman can understand them.
Repair work continues on the backhead. Overall, the backhead is not in bad condition. Welded repairs to those areas showing too much erosion are being performed to build those areas up to full thickness.
The crown sheet on the other hand is another matter. Upon close inspection it was found that steel around many of the staybolt holes in the center of #39’s crown sheet had been badly eroded. Since so many areas had been affected it was deemed most efficient to cut out the bad section and replace it with a new crown sheet section. In the following photo, the red marks outline some of the worst pitting and steel erosion surrounding the staybolt holes.
Looking upward from inside the firebox, we see that much of the crown sheet has been removed. The remaining steel does not exhibit the erosion and pitting seen in the center of the crown sheet. (Note the supporting rods for comment later in this report.)
Here is the new crown sheet section, resting on the floor, awaiting installation into the top of the firebox. Note the tabs welded around the perimeter of the steel. These tabs are located to hold the steel section in place while welding is performed.
Brendan holds one of the many flexible staybolt sleeves that will be welded onto the roof and side sheets of the firebox.
In the following photos we see the sleeve set upon the sheet;
a staybold is passed through for demonstration purposes;
and finally the cap is placed over the staybolt into the sleeve.
These flexible staybolts are located in areas of the firebox that must be allowed some movement while expansion and contraction of the steel occurs during firing and cooling.
Following are three photos taken the week of May 8, 2009 by Rick Musser at Strasburg.
The roof sheet is held in place by braces and the new flexible staybolt sleeves have begun being tack welded into place.
Work is progressing at a rapid pace.
This is a brand new staybolt not yet finished. It awaits machining to place the threads on the end and the taper. This is critical work as the threads at both ends of the bolt must start together to maintain the correct distance between the inner and outer sheets of the firebox.
Here we see two NEW support rods. These rods were manufactured to replace the two broken rods located below the roof sheet and above the crown sheet as shown in earlier photos.
Since our inspection trip on April 8, we have shipped #39’s whistle valve and bridge pipe valve (turret valve) to Strasburg for locating and mounting on the roof sheet. In June we will move the steam manifold to Strasburg. Following is a photo of #39’s bridge pipe valve prior to shipping.
Respectfully submitted,
Don Fisher, President
Strasburg Update: June 11, 2009
Staybolt Sleeves
Are the staybolt sleeves shown in the photos a standard PRR Design?
They do not look familiar compared to older photos.
If this is a revised design, is this being done to resolve a 1920's era staybolt size/spacing design that no longer satisfies FRA requirements?
I thought I read that this was the last straw for 1361 - that the staybolts were spaced too far apart for the thickness of the firebox sheets. Going to larger bolts, and a sleeve that supports a larger area under the staybolt head, is a logical technique for reducing the stresses and getting back to a design that could be certified.
Has the LIRR/RRMofPA team found a solution that could help 1361?
At the same time, all of those caps look possible future water leaks. After a number of thermal cycles, if water can get into the space around the bolt (which is supposed to allow movement, which to me means it is not permanently sealed), then repeated boiler thermal cycles will force the trapped water, as it changes to steam, to find a way past whatever sealant is used on the threaded joint. Once the seal is broken, then water may leak out whenever the staybolt is not fully seated (e.g during cold fill and pressurization, especially the pressure test). Obviously I am an amateur - can anyone explain? Or do I have it backwards - staybolts often leak when cold and the boiler is full? And then seal themselves when heated and pressures rise?
Inquiring minds want to know....
Dave Evans
Hello Dave and Gentle Forum Members,
After talking with Brendan Zeigler and Rick Musser yesterday at the Strasburg Railroad Company Shops, I have some answers to your questions.
The staybolt sleeves are not duplicates of any PRR design. They are actually “industry standard” design staybolt sleeves used by Strasburg on boiler rebuilds/restorations as well as work on their own engines. The size of our sleeve is relative to the G5s’ firebox dimensions.
This design staybolt sleeve has nothing to do with the pitch/spacing issues of the staybolt to roof sheet thickness calculations on the #1361 and the #39. There are no extant PRR designs for their old staybolt sleeves and to try and duplicate such a sleeve and make the dies necessary for reproduction would be costly – money best spent on the work at hand. Please remember that almost all of these flexible staybolts are covered with insulation and sheeting and are not seen while the locomotive is in operation.
Strasburg’s solution to the pitch/spacing issue on #39, using thicker roof sheet material, would conceptually work on the #1361 – but each engine is different and calculations would have to be made to determine the specific “fix” for #1361. In other words, for a K4s the roof sheet thickness might have to be greater than ½” relative to her staybolt spacing and pitch to conform to the working pressures and current safety values.
You are correct in your observations concerning leaks around the flexible staybolts following heating/cooling cycles. The solution to such a problem is the insertion of a gasket in each staybolt assembly. The PRR historically used copper gaskets. Today, with space age science, the industry uses Teflon gaskets to seal the staybolt sleeves.
Here Brendan is holding a brand new flexible staybolt. In our case, since the firebox is still together, the staybolts will be inserted from below, up through the staybolt sleeve as shown.
Once the staybolt has been properly tightened into the tapered crown sheet hole, a shaped head nut is tightened onto the staybolt in the sleeve from above.
Here is one of the Teflon gaskets:
The Teflon gasket is inserted into the sleeve, surrounding the shaped head – effectively sealing the assembly.
The final product. This assembly will be duplicated many times over during the restoration of #39’s firebox. We are very pleased with the expert engineering and craftsmanship going into #39 at Strasburg.
Again, thank you to all for your continuing interest in this project,
Don Fisher, President RMLI
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