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892 posts

Now with the new parts installed the engine was run once more and this times things were much better it was a bit stiff but as a fellow engineer used to say “its only the newness”And after setting and resetting the valve timing and letting the engine run for 30 minutes it soon showed that the extra work paid off and it had lots of steam and power the speed at full boiler pressure was great enough to run the engine off the curves despite its slightly smaller wheels.

Here you see it as I have just managed to catch it as it nips round my small track with 2 coaches on

I did add a set of rubber tyres to the third set of drivers these were the standard Hornby tyres for the A3 and A4 and appear to fit ok.

I still have the problem with the rear truck wheels and as you can see from these pictures just how far the rear end of the chassis swings over the rails making things hard to work as the full size engine with flanged wheels.

Another problem I found was the pivoting Hornby connecting rods these seam too flexible and would lend them selves to locking up the wheels and in some cases jam the quartering or slow the engine down so a quick fix was to solder the flexible link on the rear of the rod on the second driver this was the wheel set connecting to the piston and was therefore delivering all the power to the wheels especially the set with the rubber tyres on.

The fixing points were made to fit the body to the chassis this way I could get an idea as to how thing were working out and all looks fine the steam exhaust from the working chassis was almost directly under the hole in the brass body so no real problem there the only thing to change was the very front of the oil tank which needed more of an angel to match the angel of the front of the brass body so a little filing and this fitted better.

Still thinking on the working valve system for the model i came up with this idea which is to take the drive from the Hornby valve system and extend it out the front of the valve cover and with a small double pulley and 2 rubber o rings drive 2 small shafts above the cylinders and then down to the second drivers this way as the engine moved along the small shafts would rotate and look like the full size engine but we will see as there is still much to do on the chassis and body.


892 posts


As a much younger man I might have given up on this one but I do like odd looking engines so must give this one more try 



892 posts


yes it ran well on compressed air but when I tried it on the track in steam it was very poor not starting on its own with out a push and then only went 2 ft and stopped it did run a little better backwards but ran out of steam very quickly so after all that work a complete failur.

one of the problems is all the chassis that I'm using now are none runners that I bought some years ago and have problems before I start  the mods.

i have spent at least 3 days trying to find out what the problem is with this engine and have gone through every part taking it to bits and inspecting ever part. In the end I cam to the conclusion that the valve assembly was worn to the point that when hot it was acting differently from when cold and running on compressed air all looked fine. I think Hornby did find a problem with this part and on later models chrome plated it which while a good idea for the rotating valve and stopped any wear to the valve port faces not so good on the valve shaft as this is stainless steel which is a mixture of chrome and steel means you are now running 2 metals of the same type against each other which will cause them to wear out faster and if poor oiling is added to the equation it life becomes even shorter.

i have toyed with the idea to re engineer this part and make it a lititle better but getting back to the engine I decided that I would replace the valve assemble which would need machining it as the valve unit is a none standard part now for this engine plus change the cylinder assembly so a major rebuild along with making up new connecting rods.

all this work was carried out and after a few runs in steam it has run much better there are still problems like the main drivers are slipping which is bad as this uses up the steam fast and leaves the engine out of steam at some point and the engine sits there while the pressure builds up then it's off again with wheels spinning till it reaches the same point again and stops due to lack of steam.

This is the old part remove and a new one made


so now the question arises which wheels need rubber tyres and will have to remove them from the engine and machine some grooves in the metal tyres

i did get the from bogies to run ok so at least one thing went with out a hitch but as to the set under the cab lots of problems there using flanged wheels has presented a problem and I see why Hornby opted for flangeless wheels floating above the track.

so still lots to do which is Nearly all rework to get the engine to run properly plus still working on making the outside valve gear rotate 

Now your up to date Ken


892 posts


You are right about how much detail is needed,

when running my Hornby electric very high detailed engines bits fall off from  to time but maybe that's just me 


892 posts

Just thought I would show you this as I have now got it running with all the wheels going on compressed air at 20 psi



892 posts

Found this on the forum


1312 posts

What are your opinions on the so-called "Cartazzi trucks" on these Hornby Pacifics? My very first opinion of this design, with the flangeless wheels, was completely ridiculous and unacceptable. Watching the rear "bogies?" completely leave the rails, stop turning, and hover in mid-air around curves, just simply looks idiotic to me! To build such highly-detailed models that look so WRONG going around curves, well, the logic behind the design eludes me. I have managed to modify my two A4's by cutting-out the plastic vertical "ridges" inside the truck frame, and Dremelling out a concave relief so the wheels can slide all the way against the metal chassis. Also installing flanged wheels, of course! This allows the wheels to slide FULLY to the outside (against the plastic outer frame), and to the INSIDE (flat against the metal chassis). I have also installed, above the axle, a small coil spring (by drilling a shallow relief hole to hold it there) in order to exert slight downward pressure on the wheels. I have found this to work perfectly. Even around relatively sharp curves AND points! I have since found out, on one loco, that small plastic "shims" over the axles will work instead of springs, to keep the wheels from "riding-up" off the rails. It still seems to me a PIVOTING truck would've been a much better idea! What do you think? Don't you think loco wheels "hovering" in mid-air looks a little STUPID?? Especially since they're not even TURNING! Since they are SPOKED wheels, this is painfully obvious.....

Posted at  16:32:58 Wed, 21 Jan 2015Edited at  16:36:50 Wed, 21 Jan 2015Approved/Moved at  16:36:50 Wed, 21 Jan 2015 (Reply to this Topic

M. Crafton



892 posts


thanks for the information will find some wheels in my wheel box and if I can't get them to track up will turn off the flange must look up Cartazzi


892 posts

The connecting rod were bought as spares for the Hornby P2 so would be easier to fit to the Hornby wheels that I was going to use.The only problem with these connecting rods is they are made from very thin brass sheet and as these engines deliver a lot of power to the crank pins it was thought that excessive wear will take place on the crank pins and rods.

To over come this problem an idea to beef up these rods was undertaken.New bronze bearings were made and soldered to the rods along with strips of brass to be soldered in-between the bearings on the back of the rods this then made the complete assembly a much stronger looking job.

Back to the Hornby chassis now with 6 drivers fitted and the rods also in place now for the last set of drivers The Hornby chassis was not long enough to incorporate these wheels so an extension was needed.

It was decided to fit the rear section of the chassis from the kit by cutting this chassis between the last 2 wheel sets would also give the flared frame section for the last 2 wheels under the cab.I might have to mill off some of the metal of the Hornby chassis to get this sheet section of chassis to fit nicely. Once this was completed the kit part can be held in place by screws and maybe I could start to build up the engine once more and test it all out on compressed air and run in these new rods and bearings.

The chassis had both sides milled out to take the frame extension which is in the picture above The next part will be to find a way to fix these two sections together and where to put the screws so that the wheels will not rub on the screw heads and short out the power.


I’m not sure how this engine is going to run on my track and if the last set of drivers should be sprung ? And also if a pair of the drivers will need rubber tyres for more grip but at this stage it’s a game just getting all the wheels to turn with out jamming up due to the new bearings.The front bogie wheels are articulated so I’m hoping these will not be a problem but the wheels under the cab will need some thought as they are not the standard pony truck type and it looks like the Hornby model of the P2 has the flange removed from these wheels to help with tight curves so some testing in this area will have to be carried out and see what happens.


892 posts

Crank pin

or is it so that the pin is a standard Hornby item and on an engine with conventional valve gear the valve drive connection moves the valve gear rods back and forward.

but on a P2 Hornby engine it has poppet valve a a rotating drive shafts so the crank link needs its out end to run dead centree to the axle so the small gear box will not be going back and forth So by making the plastic wheel have an off the centre look the crank pin boss end with its 2 machined flats for the drive crank to fit to with its small hex screw and this assembly will now run true a bit like a speedo drive crank.

i hope this make sense but until I get to assemble the valve drive i will not know.



892 posts

goes like a fidders elbow

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