2½" Gauge LNER P1


This arrived yesterday and is waiting it's turn in the workshop.



It's a 2½" gauge version of a LNER 2-8-2 P1 of which there were only two full size ones built, numbers 2393 and 2394. The full size locomotives were designed by Gresley for hauling heavy mineral trains and were originally fitted with a booster engine on the trailing truck. The boosters were later removed when it was found that they were only effective when the locos were hauling loads much greater than they normally handled. The locos were three cylinder with the Gresley Holcroft conjugated valve gear driving the middle cylinder valve but this model is only two cylinder. Although it's been painted over and you can't see it in the photo, the tender has 2393 on the side

I'm not sure how old this loco is but it doesn't seem to be to any published design. There is a design by the Locomotive Design Company for a 2½" gauge P1 but this is definitely not one of them - it predates that. I think the only one made so far to the LDC design is by Tom Barnes which appeared at the Harrogate show in 2014.

For some reason the original builder put the connecting rod on the third axle instead of the second and the owner wants this putting right.



The loco was bought from a dealer some years ago and is very nicely made. Judging by the amount of soot in the smokebox it has done a fair bit of running which is a good sign. It's a big boiler with a combustion chamber and should be a good runner. There is no boiler history/certificates so the boiler will need a twice working pressure hydraulic test but I don't think there will be a problem with that.

It will probably be a few weeks before I can start to work on this but I had a quick look at it today. As we suspected, there is a problem with clearance between the top of the connecting rod and the bottom slidebars and this may have been the reason the builder moved the connecting rod to the third axle. Moving it further back means the vertical movement of the rod is smaller and clearance less of a problem. Even so, the connecting rod would foul the slidebars when at it's highest point if not for the fact that there is a gap between the bottom two slidebars and the top of the rod can go between. The spacer that goes between the top slidebar and the two bottom ones has been relieved where the rod would otherwise hit it.



So the job is to make two new shorter connecting rods along with two shorter eccentric rods. The crankpins in the wheels on the second and third axles will also need replacing. I can't just swap the second and third axles over as the third axle has the eccentrics fitted on it for twin axle pumps.

Moving the connecting rods to the second axle will make the clearance problem worse but the original rods are a bit on the chunky side and can be reduced in height to help. The rods will still be able to pass between the slidebars if necessary so I think we should get away with it.

Once the loco is sorted and running again it may get a paint job in the correct black livery.



I decided to remove the boiler on Tuesday and give it a hydro test. Should have kept quiet about the boiler passing the test ok as I found a leak on the firehole door ring! It's only a pin hole though so should be fairly easy to seal with some Comsol. The rest of the boiler seems fine. The regulator leaks like a sieve as I expected so I had to cap the steam pipe to the cylinders to do the test. It's a typical disc in tube type so I'm going to have to try and remove it to do some work on it. There are no stops on the regulator handle at the moment so you can just rotate it 360° which makes it rather difficult to tell when it should actually be shut!


I had a go at the leak on the boiler yesterday and successfully repaired it with a spot of Comsol without causing any more. When I cleaned up the area where the leak was there was a small gap between the firehole ring and the firebox backplate and the original solder obviously hadn't flowed into the joint properly.

I then discovered a leak where the superheater header bolted onto the bush on the front tubeplate but this had to come off anyway to remove the regulator for attention.

I then managed to remove the regulator from the boiler but it was a bit of a struggle. The regulator is right at the firebox end of the boiler and there is a long copper tube takes the steam to the bush on the front tubeplate. The regulator comes out through the bush in the backhead and it was held in with brass screws, all of which sheared straight off as soon as I tried to unscrew them! I've now got the fun job of trying to get the remains out of the backhead bush. The superheater header had to come of and that was held with brass screws as well. Two of them did come out ok but of course the other two just sheared off! It probably didn't help matters that some really hard setting gasket cement had been used. Brass screws are not really suitable for jobs like this as they are not strong enough to be removed when they are tight or stuck.

The regulator did originally have a pin fitted to limit the rotation of the disc but it had fallen out which is why it could be rotated continuously.


I managed to drill out the broken screws and retap the holes in the backhead bush and the steam pipe fairly painlessly. I then decided to replace the old regulator assembly with one of my screwdown type and spent today making that. The screw thread is 5/16" x 18tpi Whitworth and the seat once again made from some bearing grade PEEK. I didn't bother making any drawings first and just made it up as I went along,



The boiler doesn't have a steam dome so I couldn't fit a steam collecting pipe to the regulator block like I usually do. The original regulator just had some small holes drilled in the top of the tube to collect the steam so I did the same thing on the new one.

The original steam pipe from the regulator to the front tubeplate was only 3/16" diameter and threaded into the tubeplate flange. The flange itself screws directly into the 1/8" thick tubeplate as often done on boilers of this age which means you have to screw the flange into the tubeplate and onto the steampipe at the same time. I hate that so I modified the flange by drilling the central threaded hole out to 0.25" diameter to fit over the new steampipe I made to replace the original and recessed it to take an O ring. The O ring seals the steampipe to the flange and also seals the superheater header at the same time. Much better than gaskets. I replaced the original steam pipe as the internal bore was only 1/8" and I thought that was a bit on the small side for a passenger hauling loco. Unfortunately, the superheater and the steam pipes to the cylinders are also only 3/16" so the steam circuit will still be a bit restricted. I may replace those as well if the performance is a bit sluggish.

I gave the chassis a good wash down with paraffin tonight and blew all the gunge off with the airgun. The chassis itself hasn't been painted so I was surprised that it wasn't rusty. Some of the wheels and motion had a slight coating of rust though. The lubricator was full of congealed steam oil and grit from the smokebox so I removed that and gave it a good clean out before refitting it. It's a twin cylinder oscillating type with the two outputs joined together to give a single feed to the steam tee that feeds the cylinders. I would expect the output to be somewhat excessive for this size loco, especially as the ratchet is quite coarse, but we'll see when it's given a run. I just hope that the grit in the lubricator hasn't found it's way to the cylinders and scored the port faces and the bores.

I then gave the chassis a good oiling and tried it on air. It was a bit stiff at first but ran extremely well in both forward and reverse. It notches up well and runs quite well almost in mid gear so things look promising. After a bit it would run easily on just 10psi. The only thing is that the reverser is back to front i.e. you have to pull it back to run in forward gear and push it forward to run in reverse. That should cause some confusion! It's because the lifting arms on the weighshaft point backwards rather than forwards. Not much that can be done about that without major surgery.

If I have time to get the loco back together for Saturday I'll take it to our 2½" running day at Whitwick and see how it runs.


Well I managed to get the P1 back together in time (just!) and took it to the club for a run today. I fired it up for the first time in many years and it gets up to pressure very quickly. A couple of the screws holding the regulator flange leaked but they just need some threadlock to seal them. I didn't want to do that before incase it all had to come to bits again. Also the water gauge glass leaked but I'm going to replace the whole fitting as some of the threads are a bit loose in the boiler bushes. Also, the bottom fitting had a separate blowdown valve which snapped off when I tried to unscrew it! I've just blanked it off for now.

It seemed to steam ok so I took it on the track to see how it went. Unfortunately, the right hand front bogie wheel kept climbing the rail and I only managed one very slow lap stopping frequently to rerail the bogie. I don't think it's anything serious, the bogie just needs more weight on it. However, one lap was enough to show that the loco runs very well indeed. I think it will make a very good passenger hauling loco. The new regulator is very smooth and works very well, apart from the handle coming loose a couple of times!


I've managed a bit of time on the P1 over the last week or so.

I had a look at the front pony truck and the springs in the plungers that act as the suspension were quite weak so I've fitted stronger ones (the pony truck is the same design as for LBSC's Dyak). The pivot had loads of washers on it to alter the height of the pony truck frame so I got rid of those as well.

Some of the main axleboxes had spacers between the axle box and the hornstay so the axleboxes were basically solid in the horns and had no movement. These spacers were only fitted to two out of the four axles so all the weight of the loco was just being carried by these two axles, the other two were doing nothing. I took the spacers out and adjusted all the springing to try and get an even weight on all eight driving wheels. Hopefully, this and the stronger springs on the pony truck should cure the derailing problems.

I've made a new bottom fitting for the water gauge complete with blowdown valve. I was going to temporarily just make a valve to fit the existing fitting but decided it would be just as quick to make the complete thing. I've made the bottom gauge glass connection much longer than the old one as originally the nut was below the crown of the firebox. Now it's above it.



The silicon tubing drain pipe is just temporary and will be replaced with a proper copper pipe and union.

I've sealed the screws holding the regulator now I know the regulator works ok and secured the handle so it doesn't come loose again!

I steamed the loco yesterday at home and the seal on the bottom fitting for the gauge glass leaked. I tightened it up as much as I dare which seemed to cure the leak but later the sealing ring, made from a slice of silicon tubing, blew out. I thought the glass had broken at first due to it being over tightened but fortunately it was just the seal. I think the original seal was a bit small in section so I cut a new one from larger diameter tubing. After fitting that the seal was fine.

Incidently, I make the sealing rings by sliding a length of silicon tubing over a length of rod, mount the rod in the lathe and use a sharp knife to cut the tubing into rings. The rod is of such a diameter that the tubing is a tight fit on it. There is no way you will get nice even rings by just trying to slice a bit off the tube on it's own.

I've given the loco a proper steam test now which it passed with no problems so it's now got it's certificates. I was a bit concerned that the safety valves might fail the accumulation test but the steam pressure hardly rises above the working pressure with the blower full on. I did modify them some weeks ago and checked them on my test boiler before taking the loco to the club on June 27th. Originally, they blew off at about 50psi and I couldn't adjust them any higher so I replaced the springs with slightly stronger ones. They then 'popped' quite violently so I had to play with them to make them a bit softer. They still 'pop' nicely but don't stick open and drop the pressure too much before shutting.

When I was running the loco yesterday I noticed that the ratchet on the lubricator stopped turning when it got to a certain point so the lubricator stopped working. It looked as though the driving lever didn't have quite enough enough travel to click the pawl over the ratchet at that point so I drilled a new hole in the bottom of the lever for the connection for the driving arm to increase the movement a little. That helped but it still stopped at the same point now and again. I took the driving pawl off the lever and it looked a bit worn on the tooth so I cleaned it up with a file and put it back. I haven't tried it again so I don't know if it has cured the problem. I might try it again later today if I get chance.

As mentioned before, I think the lubricator as it stands will deliver far too much oil so it will need either replacing or modifying. It should only need one ram instead of the two and a much finer ratchet.

I'm taking the loco to a 2½" rally at Nantwich tomorrow to give it a proper run so we'll see what happens then.

One thing I have noticed is that the boiler gets up to pressure very quickly and seems able to maintain pressure even when the bypass on the axle pumps is fully shut and putting water into the boiler. The pumps seem very good and it will be easy to overfill the boiler very quickly if you are not carefull!

On a different matter, I'm collecting another loco tomorrow from friend David which he's letting me keep loan. If anyone has heard of Edward Adams, they will maybe know that he was a friend of LBSC and was mentioned several times in LBSC's Lobby chat. He also wrote a few articles for Model Engineer back in the 40s. He did quite a lot of experimenting and built many 2½" gauge locos which he ran on a circular track at his home.

The loco I'm collecting is his 'Monstrous' which was descibed in one of LBSC's Model Engineer articles for June 1948. It's based on a New Zealand Railways K class loco which is a 4-8-4 tender loco. As it's narrow gauge, the loco is pretty big for 2½" gauge, hence the name!

I'll be writing a separate section on Monstrous once I get the loco. The idea will be to try and get the loco running again if possible.


Well, it was a glorious day yesterday weatherwise but a bit of a disaster running wise!

The P1 really struggled to get around the Nantwich track and I think it's because the curves were just too tight for the loco and the flanges were rubbing all the time. It would have romped around our track at Whitwich. The Kingette struggled as well, possibly for the same reasons.

Good news is that the pony truck wheels didn't derail this time but I suddenly noticed that the axle wasn't square to the track and the wheels were running at an angle to the rails. No wonder the wheels kept riding up onto the top of the rail last time. When we got home I removed the pony truck and found that the pivot hole in the truck frame was not on the centreline, it was offset to one side, which explained that. I'll have to bore it out to centralise it and fit a bush to bring it back to diameter.

I also noticed that the oil in the lubricator hadn't gone down much so that hadn't been working either. I was expecting it to be nearly empty. The ratchet wheel was stuck in the same position as before.


I've modified the pivot point for the front pony truck frame by enlarging the existing hole and moving it to the centreline. I then pressed in a stepped brass bush to bring the hole back to the original size. After refitting the pony truck the axle now seems square to the frames so hopefully that will solve that problem.

I've also modified the lubricator by removing one of the cylinders so it's now only got the one and filed the driving pawl to a better shape to try and cure the slipping. However, when I ran the loco with the wheels jacked up the lubricator still stopped when the wheels were going at a reasonable speed. The driving pawl had never had a spring fitted to it and relied on it's own weight to keep it engaged with the ratchet. This worked at low speeds but as the speed increased, the pawl started to bounce and failed to engage the ratchet teeth. I 'bodged' a quick spring to press down on the pawl to keep it engaged and hoped that would solve the problem temporarily until I built a new lubricator.

I took the loco to our 2½" gauge rally at Sutton Coldfield MES yesterday and gave it a run. The lubricator seemed to work ok this time judging by the amount of oil on my glasses! The loco still seemed tight on the rails even though the track is profiled aluminium and there were sections of the track that the loco really struggled to get a grip. The aluminium rail doesn't help as it is very greasy but the other locos seemed to get around with no problems.

I took it easy for the first few laps because of the previous pony truck problems but it behaved itself this time so I then went around a lot faster which helped to keep the loco moving on the slippery bits but I had to press down on the boiler at times to get some grip on the rails. In the end I must have done about 20 laps. The boiler had no problems keeping the pressure on the red line all the time and it was possible to use the axle pumps all the time to top up the water level without affecting the pressure at all. The valve timing is a bit out but that is easily sorted.

It seems that even on the aluminium rail there is virtually no sideways play between the wheels and the track so I'm thinking now that the wheels are probably over gauge and that is why they are tight on any curved sections of the track (That was the problem with the 3½" Princess Royal but in that case the wheel flanges were too thick). There's also very little sideways play between the wheels and the axle boxes so there is no flexibility at all in the chassis.

I probably won't run the loco again now until all the modifications are done to the connecting rods. I can check all the wheel profiles and the back to back distances once the chassis is stripped down again.

I've just had a quick look at the tender wheels and taken a few measurements. The back to back of the wheels on two axles is about 0.019" too wide but the third is 0.029" too wide. The main problem seems to be that the flanges are too thick, perhaps by something like 0.030". That explains why the wheels are tight in the track so they are going to need reprofiling and the back to back distance correcting. The actual wheel treads are too wide as well but that isn't really a problem and can be a benefit if the track is a bit overgauge in places. I haven't looked at the loco wheels yet but if they are the same then that explains why the loco labours around the track.


I decided to do a few hours work on the P1 for a change and take it for a run at the final 2½" gauge rally of the year at Chesterfield. I took all the tender axles out and regauged the wheels by taking one off and machining a bit off the shoulder on the axle to reduce the back to back distance between the wheels. I decided to do this rather than remachine the flanges on the wheels as it was easier! This loco will never be run on scale track with points so the back to back is not really critical. I machined 0.0313" off two of the axle shoulders but the third axle needed 0.063" to give sufficient clearance between the wheel flanges and the rails.

I also gave the trailing axle of the loco the same treatment as those wheels were also over gauge. Fortunately, the driving wheels and the pony truck wheels seemed to be ok so I left those alone.

I took the boiler off again to make it easier to work on the loco chassis and renewed some of the pins in the valve gear to get rid of some of the play. The expansion links really need new die blocks as they are quite a sloppy fit but they are a rivetted assembly and I didn't want to mess about with those at this point. I also bushed the ends of the eccentric rods as they were quite loose. Whilst I was at it, I retimed the valves although they weren't far out at all.

Running the chassis on air revealed quite a lot of air escaping from the blast pipe and I rightly assumed that it was blowing past the pistons. It was relatively easy to get the pistons out by removing the front cover of the cylinders and unscrewing the piston rods from the crossheads. The pistons had two holes drilled in the end for this purpose.

The pistons each had two grooves filled with graphited yarn and this was now not sealing the pistons anymore. Rather than renew the packing (I'm not a big fan of graphite packing) I machined another groove between the two original ones and fitted a Viton O ring. The depth of the grooves was increased from the measurement given in the O ring data to make the rings an easier fit in the bores. You need very little compression of the rings in this application.

Another run on air showed the pistons now sealed perfectly so the boiler etc. was refitted and the loco taken to the rally today. It ran well and I had it in steam for about 2 hours. It seems very free on the rails now and had no trouble getting around the track. The lubricator is giving far too much oil (I expected that) and I had to refill the tank every 3 laps. Most of the oil finished up on my face and glasses!

The loco seemed to lack power however when tackling a steep gradient and I had to run it in full gear to get up comfortably. I am wondering if the small steam pipes are restricting the steam supply to the cylinders or the valve gear is not giving enough valve travel. That's something to look at when I alter the connecting rods etc. I'll measure up the valve gear then and put the dimensions in the simulator and see what the results are like.

Tom Barnes was also at Chesterfield today with his P1 built to the Chris Barron drawings and this one is a much bigger loco all round than Tom's which will be pretty much to scale. I should have taken a photograph of the two locos side by side but didn't unfortunately.


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