Rob Roy Boiler

I had a go at building a Rob Roy boiler in the mid 1980s. It has not been completed and or pressure tested but I thought it would be worth posting the pictures and getting a few opinions before going much further.

It is not the neatest boiler but I think it is a fair first attempt. I am not the slightest bit concerned if the end result is a trip to the scrap man but I would be very pleased if it can be made to work. Reading and contributing to other threads, I am aware of a few of the snags and I will point out the ones I know of as I post the pictures.

So here is the first picture of the side.

The previous picture doesn't really show any of the real snags but this next view shows the first issue. Note that the main boiler tube obviously needs to be re rounded with a wooden plug and a few taps with a mallet - the main problem is the lack of bushes for the regulator and longitudinal stays.

I had not fitted the stay and regulator bushes because the original drawings show threaded holes directly into the plate. I understand that direct threading is no longer permissible so my guess is that a reheat to fit the bushes is gong to be necessary. Does everyone agree - or is there a smart work around that could be proposed to any inspector?

Hi Phil,

You shouldn't have a problem silver soldering in the bushes on the front tubeplate. Just make sure that you flux all the exising joints as they may well melt again.

I've added bushes on the backheads of a couple of Tich boilers for someone without problems and that is much harder than working on the front tubeplate.

One point about having to extend the firebox sides on such as Rob Roy boilers - offset the cut in the barrel for the part that has to be folded down to make the firebox sides such that you only have to extend the one side. Just makes it a little easier. I prefer to make the firebox wrapper as a separate piece and joined to the barrel with a joint ring or an overlapping joint. That eliminates the need for the extension pieces.

John

Thanks John, I will do a reheat for the front tubeplate to add the missing bushes.

You have anticipated my next picture of the backhead. You might notice the missing stay bushes at the backhead end. Again, I assume there is no clever fix and a reheat will be involved? While I do a reheat - I guess the top water gauge fitting could also be added. Again, the original drawing and book suggest the top water gauge could be added with screws.

Phil,

If you are contemplating having your boiler certified for public running then your boiler inspector will probably wish to examine the penetration of silver solder on the inside. To this end I have been advised to present my almost complete boiler to the inspector before the backhead is fitted - you might want to remove the backhead completely before fitting the additional bushes.

HTH,

Rod

Rod,

I think it would be a devil of a job to try and remove the backhead at this late stage of the game although I do see your point. I think you would probably finish up wrecking the boiler.

John

Edited By John Baguley on 13/05/2017 17:09:38

Rod,

Yes the aim would be to certify it for public running and I agree that staged inspection would definitely be the right thing to do if I was starting the boiler now. However, I agree with John here - I think removing the backhead would not be impossible but it would be an interesting challenge.

Also, I am not convinced (maybe I'm wrong) that full inspection of solder penetration is always that easy. For example, it would be very difficult to examine the front tubeplate unless it is soldered quite early. If it is soldered quite early in the process allowing both ends of the plate to be inspected, you would not be able to inspect both sides of the tubes for penetration.

Phil H

If the foundation ring isn't in place he should be able to get an idea of the sort of penetration you are getting.

Neil

Neil,

Yes sorry, Ill post another picture. The foundation ring is very firmly in place and this next picture shows the next challenge. On a separate thread, we have discussed the side stay spacing. You will note that mine has a 4 x 4 pattern at 3/4" x 5/8" spacing for 1/16" sheet. It has been suggested that the spacing should be 5/8" maximum.

.

The throat plate and backhead both being flanged was it awkward in way of the outer wrapper buttstrap when s.soldering? 

Mick

I'm sure you're right chaps, it will be difficult - something I need to have a go at with a Jenny Lind boiler I tried to make decades ago.

My inspector will be using a mini video camera to look at the back of my Rob Roy smoke box tube plate .

Rod

Mick,

The wrapper buttstraps on my boiler were cut short at both ends - short enough to fit both plates without any issues.

Rod,

What is the issue with your Jenny Lind boiler i.e., have you almost or entirely completed it like my Rob Roy boiler and an inspector is insisting on seeing the internal joints?

I think it is possible to remove my backplate but it would obviously destroy the plate and the key question is whether it is strictly necessary. Is the mini video camera being used by your inspector small enough to see all the tube joints i.e., is it a very slim medical style camera?

Phil H

Phil,

My Jenny Lind boiler is "complete" but failed my own air test with bubbles coming from a pinhole in the firebox crown where it joins the firebox tube plate. I never managed to re-heat this successfully, even with a cyclone burner which kept blowing itself out in the confined space. Also, thIs LBSC design, although modified by Alec Farmer at Reeves, does not have any join between the crown stays and the outer wrapper. I haven't discussed the Jenny Lind boiler with my inspector yet. In general though I don't think that they like being asked to approve a completed boiler which has (as far as they are concerned), no provenance. A certificated boiler made by a commercial outfit is somewhat different. I should take my own advice really, show him what I've got and ask for his guidance on the way forward.

As we have discussed on this forum recently, boiler certification is a fairly loose but effective system so discussion at the earliest stage possible with the inspector is probably best. Joining a club so one can rock up with a completed boiler and request a certificate could result in a frosty response.

Cheers,

Rod

Rod- I did see a chap on you tube who suggested that having the holes which draw air into the torch located at the handle end of the torch instead of at the nozzle reduced the chance of the flame being blown out when using in a confined space

Thanks Phil re buttstap

Mick

Yes, that's the cyclone burner. **LINK**

The space is so confined that I'm guessing that the combustion products are getting drawn back in to the air intake or that the burner doesn't solely rely on the air from the intakes near the handle. However, this was all happening 25 years ago and I have now bought one of the little Oxy Propane sets but not used it yet. Really must try to finish the Rob Roy first

Rod

Rod

Okey dokey I live and learn

Mick

Rod,

Two different inspectors at two different clubs have actually picked my boiler up and had a quick look at it. They did not perform a thorough visual inspection or a test of course. Both of them seemed very approachable, helpful and suggested that the way forwards would be to start with a pressure test. Both clubs were a long way from being frosty. However, life got in the way a bit and I have not returned yet. Also, I have since discovered the various issues that they might not have noticed or appreciated with their quick look. Such as the lack of longitudinal stay bushes, the regulator bush and the 3/4" spacing of the side stays on 1/16" sheet. Also, the lack of a top water gauge fitting.

In defence of the boiler as it is, it was built in accordance with the drawings and construction manual that I had at the time and I suspect the staged visual inspections have been introduced since say 1985.

One reason for posting this thread was to check whether there were any other weaknesses that I should make sure the inspector sees and whether there might be any elegant solutions to the weaknesses.

Interesting to note that you had problems with the cyclone burner. I don't have one but I was relying on that type of burner to help if I had similar firebox issues.

Phil H