Clarkson Princess Royal

[baggo]

Brought this home last thursday to do a bit of work on. It's a 3½" gauge Princess Royal, built to the Clarkson design and using their castings. It's only a two cylinder version though so I wonder if the cylinders have been bored out larger to compensate.

It was built by a miner at least 30 years ago, probably a lot more, and was only steamed once before the chap passed away. The couple that own it now have had it on the sideboard for the last 30 years but have decided that they would like to see it running again. Our boiler tester tried to give it a hydraulic test but all the fittings leaked like a sieve so one of the club members kindly volunteered me to have a look at it

There's no paperwork for the boiler so I've taken it off so that I can blank everything off and get it properly tested again. The regulator has seized solid so I'm going to remove it to have a look. I've a feeling it may be a disc in tube type. It doesn't seal anyway and disc in tubes are notorious for that

The chassis is very well made but a bit stiff at the moment. I don't think it's seen any oil for 30 years! After a good clean up and oiling, I'll run it on air to see what it's like before refitting the boiler.

It will be nice to see it running again

John

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[baggo]

Another pic

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[baggo]

And another

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[baggo]

Managed to remove the regulator tonight after a bit of a struggle. As suspected, it is a disc type and the mating surfaces were not very good, so no wonder it leaked. They were lapped flat on fine carborundum paper on the surface plate. The main problem was a deep groove turned on the surface of the valve, presumably to mark the pitch circle for the 4 holes. This would have allowed the valve to leak even if the surfaces had been flat.

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[baggo]

One or two things about the boiler construction that wouldn't be considered acceptable nowadays. The regulator block, which also acts as the connection to the superheater header, bolts directly to the boiler tubeplate without any bush. There was a lot of 'goo' on this joint, presumably to get it to seal. The surfaces are not particularly flat! Some of the tube ends have melted a bit where the builder was a bit over enthusiastic with the torch.

Also the dome bush is just soldered onto the top of the boiler shell, there is no spigot that protrudes through the shell as would be done now. The safety valves screw into a plate soldered on top of the firebox outer wrapper, although there is 1/4" of thread for them to screw into.

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[baggo]

The superheater elements are only 6 inches long so will have little effect on the steam temperature. It will probably be a very 'wet' engine when running. I don't have any plans for the loco but I suspect that the firebox should have a combustion chamber, unlike this one which does not. One on the Station Road Steam archive shows a combustion chamber boiler.

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[Shawki Shlemon]

I am sure John , you are going to bring this engine to life again. As for the boiler the rules are not retrospective here , I guess is the same there , so we treat a boiler condition to the time it was built , it does not look too bad , the main thing is if it passes the hydrostatic pressure test , the rest I am sure you will take care of . It is harder to restore an unknown engine ( by unknown I mean not knowing what the builder did ) than building a new one because the options are very restricted .

[baggo]

Hi Shawki,

Yes, I think the boiler will be fine. I'll test it to twice working pressure though as it's an unknown quantity and has no paperwork. I would imagine our boiler inspector will want to do that anyway. However, without the drawings I don't know what the working pressure should be but I would guess at 80psi ?

It is nice to get these locos running again. I know it holds up my own projects but I still get a lot of fun of doing them There's another two waiting in the wings ;D

I've modified the regulator body to take an O ring that will seal in the hole in the boiler tubeplate. Hopefully, this will make it easier to get steam tight again. I wasn't happy with the fit of one of the studs in the copper tubeplate (it was a bit loose) so I made a special sleeve nut to fit on the stud behind the tubeplate to make sure it's secure.

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[baggo]

Bronze sleeve nut

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[Deleted]

Looks like an interesting project John, pretty loco as well...I think it's great that engineers like you take on these old loco's and breath life into them once again....

Pete

[baggo]

Hi Pete,

I get to play with them as well ;D

Incidentally, the plumbing is almost identical to Hielan Lassie where the injector is teed into the axle pump feed. I'll probably rearrange that and put the injector separately.

Refitted the regulator today and made up some blanking plugs for the boiler ready for a hydraulic test. Had a go at that tonight with not good results. As soon as I applied any pressure, water dribbled out of one of the horizontal stay nipples on the front tubeplate

I guessed correctly that the nipples were the internally and externally threaded type beloved by LBSC so managed to remove the stay and both nipples quite easily. They were both very loose. I was very suprised to find that the stay appears to be stainless steel rather than copper or bronze. Not sure that is a good idea.

The threaded holes for the nipples in both the tube plate and the backhead had stripped and I wonder if they had ever sealed properly? The answer will be to tap out the tubeplate and backhead to the next size up and make some new nipples but I think I will replace the stainless stay with bronze. While I'm at it, I'll replace the other stay as well. Both stays are solid as the blower pipe runs along the outside of the boiler.

I must admit I don't like this method of fastening in longitudinal stays. If the inner and outer threads on the nipples don't engage simultaneously, there's a good chance of stripping one of the threads and I think that's what has happened here. It's not so bad if you've got a proper threaded bush in the tubeplate but these screw straight into the copper.

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[Andrew C]

I'd be worried about the thread on a bronze stay. It may just be my experience of threading bronze they never seem to cut cleanly.

With a stainless one the only thread that strips is the one in the plate. If the happens atleast the tube plate is still retained by the stay all be it by the stay and effectively an end cap.

Andrew

[baggo]

Hi Andrew,

I don't seem to have any trouble threading phosphor bronze so long as you use a suitable lubricant. It's drilling the damn stuff that I find difficult! I use it for longitudinal stays and all my boiler fittings. I'm very dubious about re-using the stainless due to possible electrolytic action between the dissimilar metals. I removed the second stay this morning and that had definite spots of rust on it. I don't know what grade it is but it's strongly magnetic.

Work on the boiler will have to wait now until I order some bigger taps and dies and some 1/4" phosphor bronze bar.

I oiled up the chassis this morning and ran it on air. It ran very sweetly in forward and reverse on 20psi but has a bad blow up the exhaust. It's probably the piston packing that's dried out and shrunk but I'll check the valves for leakage first. I don't think the oil from the lubricator ever got to the cylinders as the union on the steam Tee to the cylinders was solid with some sort of gasket goo! It's possible the port faces are scoured because of them running dry, although wet steam lubricates quite well fortunately.

[baggo]

Disconnected the valves so I could move them by hand. Most of the 'blow' was coming from the LH cylinder and it still blew when the valve was in the centre. Time to remove the steamchest cover. There were a few score marks on the port face but also polished points where the valve was obviously contacting and dull places where it was not

The steam chest was soon off and it was obvious that the valve was only touching the port face at two points and not evenly all over. Lapping the valve flat will be easy but the port face will not be so easy if that needs doing as well. The cylinder might have to come off as well which I want to try and avoid.

Looks like the builder had an 'Oh Bugger' moment with the ports judging by the plugged holes at the ends. Good job the exhaust port doesn't play any part in the valve timing as it's a bit irregular!

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[Deleted]

Well I still know very little regarding boiler construction but on talking to some of my club boiler inspectors some weeks back they don't like stainless in a boiler for anything other than the superheater. Can't remember the reason why now but whatever it was it made sense to me at the time.

Pete

[baggo]

Hi Pete,

I think the main objection is chloride stress corrosion which causes cracks in the stainless but it's enough for me that one of the stays is showing signs of rust! I do use stainless for valve stems but that's a non critical area.

I lapped the slide valve flat tonight and when it was tried on the port face it rocked from corner to corner! The valve was definitely flat and I checked the port face with a slip gauge that was known to be flat. The port face is definitely warped or has a bump in it. I think the cylinder is going to have to come off

I think this job is going to have to go to the back of the queue for the time being as it obviously involves more work than originally anticipated

Thinking about it, truing the port face up would be an ideal job for the new shaping machine when it's up and running

John

[baggo]

Whilst having a break from making two Tich steam turrets for someone, I took the offending cylinder off the engine and gave the port face a bit of a rub on some wet and dry. It's got a definite convex curve on it when put on a surface plate. It's very badly scored as well so the face is going to have to be skimmed - it's too bad to sort out by lapping. While I'm at it, I may as well true up the ports and either adjust or remake the valve to suit.

I've removed the other valve chest cover and things look at lot better with that cylinder.

The cylinder bore is 1-3/16" diameter which fits in with similar 3½" gauge locos so should be powerful enough. There's no polish at all on the bore so it's definitely not run very far.

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[Shawki Shlemon]

In our COPPER boiler code SS is NOT permitted in the construction parts but it is permitted in operational attached parts such as regulator operating rod and even on attaching bolts/screws as long as they are not in direct contact with steam . What John does is basically the same as our code .

[baggo]

Finally managed to get back to the Princess and decided to get the boiler sorted before going any further.

A close look at it showed that there was a bulge on the bottom of the firebox tubeplate. There were no stays in that area so it's not surpising as it's a large area to leave unsupported.

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[baggo]

The only thing to do was to retrofit some stays and that meant all the cleading had to come off. Oh well, at least it would give me chance to have a look at the general construction of the whole boiler.

The cladding was all soft soldered together in situ so I had to unsolder all the joints to get it off! It came off easily enough but it will be a pig to put back and it will need repainting as well

The original stays were 3/16" copper threaded into the wrappers, rivetted over, and then soft soldered. The boiler itself is brazed or silver soldered together. Pretty much how boilers were built in those days.

I decided to fit three stays in the throatplate/tubeplate. Drilling and tapping the plates was awkward as they are not parallel, so the holes had to be at an angle to both plates. The plans call for a combustion chamber but the builder of this boiler had omitted this and made the front of the firebox vertical instead of following the slope of the throatplate. (thanks to Martin from Melbourne, Australia, I now have a set of drawings. Thanks Martin

I also had to make a tap from silver steel as the ones I had were not long enough.

Anyway, the stays were fittted and caulked with High temp soft solder, although I think the rest are probably done with ordinary stuff, maybe Tinman's?

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