I was checking out the T1 Trust Facebook page and they have lots of recent updates on the boiler construction. It looks like they have been busy making the firebox parts and assembling them. It looks like Steam Services of America machined the mudring and the guys at the Trust are building the firebox off of that.

It looks like they are putting rivets in mudring, why would you do that on a welded boiler. It seems you would weld that. Is there a reason that it needs riveted? Is that something FRA requires? Just curious, it seems like extra work.

Here is a picture they posted of the backhead. That seems larger than most I have seen.

I'm assuming the post you're talking about the mudring is this one?
https://www.facebook.com/t1locomotive/p ... 4719984812

Your question basically gets asked in the comments and is answered there sort of; basically it's just for the looks.

They could have made the backhead smaller, but then it wouldn't fit the rest of the boiler.

The ASME code allows for a welded thin mudring essentially the same thickness as the firebox sheets. However, the code is written mainly for stationary boilers. Several years ago, the British reproduction locomotive Tornado made news when it was reported that the boiler suffered hundreds of broken staybolts after only one year of operation.

Right, wrong or indifferent, our school of thought on that was that a thin plate mudring offers no rigidity or stability to the firebox/wrapper interface, and can allow the firebox to "bounce" in relation to the wrapper on a locomotive underway, which if correct, could explain the large numbers of broken staybolts on Tornado. Note that we have no evidence that the above theory is what happened to Tornado, it just makes sense to us.

Accordingly, our standard practice is to make a substantial mud ring and rivet it into the boiler, Then we know that it is going to work.






Note that the backhead brace T-irons are riveted in place as well. The standoffs could have been welded directly to the backhead , but then a doubler would need to be welded to it as well to support the thin backhead. As it is, the T-irons do double duty, supplying the anchor points to the backhead braces, and acting as doublers to the backhead.

Thanks for your thoughts and great pictures of boilers under construction. I like your thoughts on the mud ring and think your right on. I am a fan of welded boilers moving forward in our industry. But in the case of mud rings I think I like the idea of riveted construction too.

My disclaimer is I am just a guy with an opinion and not a boiler guy with tons of experience. But if opinions matter on face masks and what others should do with their equipment all based on opinion that make me ok too! The adage of "Opinions and Aholes, everybody has one" holds true for most of us. Think we get in trouble when "opinion" become confused with absolute truth. Again I appreciate Kellys thoughts and sharing.

Thanks again, John.

... And most of them stink...

I think that this appearance of being larger than most you have seen have to do with the fact that most backheads extend below the cab floor and running boards, thus you are not seeing the full picture. If you remove the cab you will (likely) see a comparably large backhead.

One thing you are also forgetting is the design of the firebox itself. The T1 uses a Belpaire firebox which is taller than the boiler overall. Look at most models of any Pennsylvania steam engines and you will see the shoulders of the firebox in front of the cab. Also the T1 requires a large firebox for the amount of steam it needs to produce. So hence the larger than you would expect for it to be. You are basically building a 4-4-4-4 simple rigid frame simple articulated engine. It has 4 steam cylinders to feed and they will be using a large amount of steam at high speed.