Allen 10 wheeler boiler

[rspringer]

Getting ready to replace the boiler on my 10 wheeler. What is the collective thought on girder stay or 3/8 rod to the top of tube and crown sheet. If round stays how many? Also any other changes to add or consider. It will be professional welded. Going to use 3/8 stays instead of the 1/4 in plans.

[NP317]

I prefer crown staybolts over girder stays. Direct connection to the boiler shell.
For crown staybolts, use the same pitch (spacing) as for the firebox side stays. I have seen 6 stays as a minimum.
Yes on 3/8" diameter staybolts, minimum.
~RN

[Fender]

With girder stays, all the pressure above the firebox is transmitted to the mud ring. So, for example, if the firebox is 8”W x 10”L, and you hydrotest to 250 psi, then 8 x 10 x 250 = 20,000 lbs of force is applied to the mud ring. Not to say that this is bad, but must be considered in the design.

[Vance Nickerson]

Just build it like it says and run it. Having built dozens of Allen boilers and never knowing of an issue don't overthink it just enjoy it.

[PeterCraymer]

I used 3/8 stays in original locations. No preference on the type of stay on the crown sheet. I built using the girders but only because that is what was on the print. I omitted a few flues because they were behind the blast nozzle and have had no noticeable effect. I will however use 3/4" flues for the next boiler. Firing on coal and having 1/2" flues means they get dirty and will plug after a couple hours running. Hope to make that better next time!
As Vance stated, don't overthink it!

[Marty_Knox]

No one has addressed the 'Achilles' Heel' of the Allen boilers - that 3/8" wide water leg. Virtually every Allen that I have seen that has failed has had the water leg packed solid with scale and/or rust. It's worthwhile to increase the width of the water leg to 1/2" or even 5/8"

[Pontiacguy1]

Got to maintain that outside firebox dimension so it will fit down between the rear drivers. On 7 1/2" gauge you can cheat out a little bit. Otherwise you've got to either make the sheets thinner (I wouldn't), or decrease your fire grate size enough to make the legs 1/2" wide inside. I've seen several that were done this way and they've all seemed to steam just fine. Putting in enough cleanouts that you can easily get to, and actually using them every once in a while, will do a lot for boiler life as well.

[Fender]

Virtually every Allen that I have seen that has failed has had the water leg packed solid with scale and/or rust.

Wow, a textbook example of a “mud burn”, where the scale prevents water circulation, and the overheated side sheets bulge into the firebox from the boiler pressure. Scary!

[Builder01]

No one has addressed the 'Achilles' Heel' of the Allen boilers - that 3/8" wide water leg. Virtually every Allen that I have seen that has failed has had the water leg packed solid with scale and/or rust. It's worthwhile to increase the width of the water leg to 1/2" or even 5/8"

That is scary!! I would sacrifice the grate width and make those water legs thicker.

David

[NP317]

Terrible looking boiler abuse. A clear reason for water treatment and boiler washouts.

As for narrowing the firebox grate area:
Keith Sternberg did his research and math on his Allen TenWheeler and ended up blocking off the front 30% of the stock dimensioned grate in the firebox.
This provided the recommended grate area to fire tube area ratio, per prototype practice.
The boiler burns coal and is an outstanding steam producer. And the covered forward grate area acts as a combustion chamber, further improving steaming.

I've run his Ten Wheeler and found it all too easy to lift the safety valves! A very free steamer.
~RN

[rkcarguy]

Wow, looks like the owner used salt water in that one!
Any harm in omitting the water legs and using thin fire brick on each side of the fire box instead?

[FLtenwheeler]

No one has addressed the 'Achilles' Heel' of the Allen boilers - that 3/8" wide water leg. Virtually every Allen that I have seen that has failed has had the water leg packed solid with scale and/or rust. It's worthwhile to increase the width of the water leg to 1/2" or even 5/8"

I just flushed my water legs in my boiler. I had some nasty stuff come out.

Tim