food for thought

[gowest]

These little steam engines that Hornby built have taken up a lot of my time as I think they were the best thing that happened to 00 gauge, the engineering is for me just a little marvel in every way if we can polish up the system then it could only get better as like many of the railway companies they built steam engines and later on refits changed parts and designs in an effort to make them better. So this is my ideas on yet another part of the Hornby engines and relates to the A3 engine only.

Hornby Live Steam Valve mod

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This project was to test the idea that the valve system does at some point in the live steam engines life suffer from excusive wear.
This being the case then the steam tight seal between the valve face and the valve are degraded and the engine suffers poor steaming as steam
escapes from the valve into the centre drilling and then up the chimney
leaving the engine to build up steam before it can move off again.
This miss alignment of the valve can also lead to the port face drilling not lining up
Correctly.
1. I think this has come about may be because the finished brass valve port has the hole drilled too large for the vale shaft this is some times done because if you are going to chrome plate the brass unit as with these later engines you must allow for the plating which will coat the hole sides making the drilled hole that much smaller and on assemble the valve shaft will not fit in the hole as the hole is now too small.

The next thing to consider is the materials used in this area in an effort to cut down the wear of the rotating valve on the brass port face on early engines the chrome plating idea must have come about which did solve the problem for the rotating valve but the trouble is that by introducing the chrome plating to this part the drilling for the valve shaft would be chromed and as the shaft it self has chrome in it being stainless steel you then get a wear problem with it being 2 similar materials.

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You can see what I mean by this picture here.
If you look at the centre hole in the valve block you can see a circle of raw brass showing where the drive peg on the valve shaft has been turning and worn the chrome off the port face leaving this
Section now lower than the rest of the face.
The shaft has also worn the hole in the same way and the shaft has become sloppy and resulted in being a poor fit.

What may have accelerated this wear might also be the way the valve shaft assemble is made up you can see in the next picture that this assembly
consists of a washer a brass tube type spacer and a spring this small spring applies pressure to the end with the shafts drive peg and by pulling this peg onto the chrome ports face and will generate the wear as seen in the
previous picture.

 

 

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My idea is to bore out this centre hole and make a bronze sleeve that will be a press fit in the valve block there by giving the a new lease of life to the valve assembly. You could make a completely new valve block made entirely of Bronze, but its worth just trying this mod and see what happens.

Once the new bearing is pressed in to the valve block the hole for the exhaust passage needs to be drilled in place this is done by using the existing hole in the top of the valve unit and drilling down into the now bronze bearing.

This chrome plating idea and the problems which can arise has all been done before
I believe the Rover Car Company did the same thing I think in the 1930’s they chrome plated the bores of there engines to stop the
engines wearing out but as the compression rings where made of chrome the engine
suffered and worn out quicker.

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This is the bronze bearing in place from the front and again pictured here from the back I have made the back end with a boss which helps to press it in place and gives a little more bearing surface and support to the valve shaft.

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Now with the shaft in place pictured from the front the centre of the shaft has the exhaust drilling and the small peg that drives the rotating valve.

The last picture is taken from the back with the valve shaft in place it will be interesting to see what happens when this idea is tested out.
Also it might be worth considering the valve drive shaft drive peg this peg engages in the rotating valve as the means to drive it the valve but as it acts on only on one part of the valve is this also contributing to excessive wear.
If it had a different design of coupling to the rotating valve might the wear on the shaft be less? Say a splined or two pegs type of unit.

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The next 2 pictures show a possible assembly in drawing form and with the spring no longer used but in stead a circlip to stop the shaft sliding back into the valve and thereby reducing the steam exhaust passage.

There is an idea to add a bearing to the back end of the new bronze sleeve.

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Here in this picture you can see the valve shaft and the circlip in place.

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The next picture shows the different parts which will make up this new valve assembly.
In the drawings a new idea was to make an under cut in the shaft back from the end with the peg in and fit a rubber seal here this would act as a better seal to the shaft and valve body 

Look closely at the picture and you might just be able to see this rubber seal.
I hope this makes sense  I’m not sure it does me and I wrote it?

[96RAF]

Superb Ken.

[ellocoloco]

An absolutely fascinating read. I hope it delivers the improvements you are hoping for?

 

Thank you.

[gowest]

testing the idea

[gowest]

With just a little bit more engineering a 3rd new valve unit was constructed this one was as the last full drawing using the ball type outer bearing fitted to a slightly larger boss machined on the end of the bronze sleeve bearing.This picture shows the completed new valve unit ready to fit to an engine.

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I have pictured here just how small this bearing is and does give a good positive feel to the valve rod as it is turned.

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Here are the 2 valve units side by side the standard Hornby one and the new valve unit. You can see the new valve unit no longer has the brass spacer and the spring this would also make the unit a good candidate for smaller wheel base engine as there is a long section of valve rod that can be shortened to fit different size engines.

 

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Now all I need is an engine to test this valve unit out on and looking through my small collection I found this engine looks to be of the type of A3 with the chrome valve unit and the larger oil filler screw so must be one of the last engines that Hornby made.Its missing some parts like the rotating valve and its cover along with the pony truck but apart from that looks ok.I bought this engine on ebay a few years ago as a none runner for spares or repair so what is wrong with it I do not know by my intention then as now it to use the parts to turn it into a different engine altogether may be a Back 5 or the like.

Once I have sorted it out and got it to run after I will filling the tender to the top with water and run it with 3 coaches and keep it going till it stops and check its overall run against a clock making a note on stopping and starting then change to the new valve and hope it runs as good or better the new unit will not have been run in so could affect its performance but that’s what testing new ideas are all about. In reality the new valve only has to work as good as the old Hornby one but the improvement is in the fact that it will not wear out too quickly.Will report back and let you know????

[96RAF]

I know I keep harping on about it Ken, but folk generally do not realise the scale of these tiny assemblies. Your picture of the bearing brings things into sight of those who can visualise such things, but all credit for the miniature engineering you carry out.

 

Could this be the cure for the troublesome 51XX that posed so many problems, which as usual you just sorted out as the project progressed.

 

Wouldn’t it be good if Hornby could do a limited edition run live steam engine incorporating all these modifications you have developed, along the lines of the over the top priced retro tinplate models - that don’t seem to be selling at £500+ a pop - does that tell you something about their flawed max profit based marketing strategy.

[gowest]

Hi Rob

not sure about all that marketing stuff but I did suggest a limited edition one off loco but I think they got there fingers burnt once get it burnt so will stick to the standard electric stuff but you never know 

As I'm typing this have got the non runner running and it's going great guns after a bit of tweeting it's been running for 15 minutes and the sound and the steam is a joy to watch what great models they are there is nothing like it not sure what will happen when I strip it down and fit my new valve? Then I must pick up the 51xx and see what's to do.

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[gowest]

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I hope this helps in understanding just how big or small this part is the initial fit of the valve unit with the bearing had a small problem which was that its bearing housing fouls the case chassis so a small amount of filing was needed to allow it to fit in plac.

am looking into home chrome plating so that the poor old A4 engines which missed the chrome mod could be brought up to date.

A second idea might be to white metal this area and polish it flat and see how that might work so have ordered some white metal and will give that a try.

As I have 3 different styles of new bronze bearing valve units it will take a bit of time to check them out on my test engine and see what I get.

[gowest]

In the drawing here I have filed out the bottom part of the chassis so that the bearing housing with the bearing in will fit in the chassis.

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Once this was done the engine could have the valve unit fixed in place and then all the other parts like the red/green light PCB fitted in place and the supper heaterThen a test run undertaken.

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 The 2 pictures shown the new valve unit fitted and a nice fit it turned out to be so the engine was put on the track and a steam test carried out and after a while I had enough steam to run the engine and away the engine went once at speed it fell off the track which showed the engine operated no differently at all I let the engine just run for a good 20 minutes and no problems showed up so all in all I’m very pleased with the valve mod.

Time will tell if this has reduced the wear in this area and also help in offering a new repair to worn out units as parts become more harder to obtain.

Re chrome the valve front face is possible as this can be applied using a brush and small electrical supply or another idea that might work would be to use white metal on the valve face and see how this works out.

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Here you see the engine running round my track it went better than I thought as it needed to have the valve and valve face run in a bit.

If any more runs or tests using the plain bronze bearing are under taken then I will let you know the out come.

[96RAF]

Another job well done Ken.

[Gitter]

Very interesting. Well done Ken.

[gowest]

Hi

yes still sitting here late at night running the engine and still going great must try a valve unit with the plain bronze bearing.

[96RAF]

Good to hear you are burning the midnight oil in support of the hobby Ken.

If the various mods are similar in performance, it boils down to cost but also to ease of manufacture if you are going to move the mod forward into the wider world of live steam.

[gowest]

Hi Rob

if down to cost then the valve unit could be machined for bronze not brass and if it is constructed with out the bearing the cost should be a little cheaper plus it would be easier to shorten the valve shaft for different engines plus you can do away with...

No stainless steel spring 

No brass tube

No chrome plating

all items needing some machine work where as the additiona parts a off the shelf washers and an E clip.

the live steam club pick up on my postings and have reproduce an idea or two of mine so maybe one day they might look into producing parts in an effort to keep club members and other live steam owner going.

but the you never know Hornby just might one day build a new engine and all the parts I have re engineered be incorporated into a new engine?

[gowest]

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The plain bronze bearing sleeve with out the ball bearing fitted was assembled into the test engine and a second test run carried out all went fine and no difference in the 2 bearing assemblies could be detected the engine in both cases performed well and oil could be seen making its way through the bearing and shaft to the position of the washer and E clip on both units.

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Looking at the engine in this picture you can see the valve drive shaft and how exposed it is.

I do not see why the bronze sleeve could not be made 20 mm or so longer passed the boss there by giving more support to the shaft at the gear end and extend the life of the valve unit further.As far as wear is concerned this would all contribute to the life of the valve unit even longer.I have drawn up what it might look like in the drawing here.

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I think we have looked in detail at this valve unit and arrived at a repair should one be needed and the possibility to build a much harder wearing unit in the future .There are other parts of the engine which need a looking at some I have covered in my rebuilds but for now I think its time to draw a line here with the valve unit return to other projects under construction.

[gowest]

Just an update

As I have the white metal I thought I might give it a go so took the valve unit with the bearing in and dismantled it I clean off the chrome plating to reveal the brass underneath as the white metal will not bond to chrome.

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I heated the valve unit and fluxed the surface then dropped on small bits of white metal as the metal started to melt I pushed it about with a brush to try and get an even layer.

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Using some wet and dry the valve face was ground flat ready for the valve and shaft to be refitted. The engine was rebuilt and some steam tests were carried out I think the chrome idea will be a better bet.

[96RAF]

Usually white metal bearings would be running in a pressurised oil flow, like car big ends on bery older vehicles, so the severe working conditions of your steam engines may be the death of that idea Ken.

[gowest]

Yes Rob

i don't think it will be a lasting bearing surface as the all brass valve units end up looking like a record with round scratch marks so this soft white metal is no doubt going to look the same after a few runs I will run the engine a few mor time a take the valve unit apart and see what's what.

white metal was used in loco axle boxes before the Timkin roller bearings were fitted and old cars had engines with no oil pumps and these were splash fed lubricatedI have 2 old Fordson tractors one 1939 and one 1945 both have white metal bearings on the crank shaft and no oil pump and are splash lubricated and still going strong but this small valve unit is left best with the chrome face and bronze centre bearing shaft 

while in dissimilar metals for bearing maybe a look at the gear drive of these engine could do with an up date.

[96RAF]

With all these changes Ken, you are getting to the ’its the same brush just had a new handle, head and nail’.

To be fair the engines and control system changes you are making are a vast improvement in many areas from the originals.

[gowest]

But isant that the way thing evolve some times they are good improvements some time not take the woman that put the rubber washer in the Spifire carburettor float chamber to stop the engine loosing power in a roll or dive I say this as Rob is an old RAF chap and may have touched on this in his time with the RAF? The RAF chaps gave it a nick name which if I tell you will get me thrown off the forum!

ken

[gowest]

The next part that could do with up dating is the servo drive unit this is well constructed and with individual bearing to each gear shaft well made.

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If you look at the picture here of the servo unit you can see that the shaft for the first gear section is steel but the part we are concerned about is the red arrow and the shaft here is brass so we have a brass shaft running in a brass bearing not good.

You might have seen a black oily deposit around the area of the servo unit this will be from the bearing and shaft and is the brass wearing away.There is quite a load on this part as it move the steam valve open and close and set the valve timing into forward or reverse.I have found that the mesh of the 2 gears becomes poorer as they start to loose a good depth of tooth contact with wear and can fail or add back lash to the gearing making it harder to control the engine.

This can tend to add load to these componets as the bearings are not giving free running and will therefore add more load to the gears and electric motor.

To remedy this I propose to change the shaft from brass to steel I can under stand why the worm gear was made in the way it was as it can be made more easily so lets make a start on the changes.

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First I set up the worm gear in a collet lathe this is a more accurate lathe than a 3 jaw lathe.

In the picture here I am removing the old brass shaft from both ends of the gear.

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 Then I drilled a hole larger than the old brass shaft this way I can machine the steel shaft down to the right size to fit the old Hornby bearings.

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Now I’m turning down the steel shaft to fit the Hornby bearings this should over come any wear in the old bearings and make a firm fit.

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Here are the 2 worm drive gears side by side the old brass one and the mod one with the stainless steel shaft.

That concludes the changes I cant see a problem but will try it all out in the test engine. 

[gowest]

I have now run the test engine and completed 5 hours running with the worm gear and the white metal valve face.The worm gear mod showed there is no noticeable wear in the gear shaft or the bearings the black plastic gear teeth still have a good mesh and movement in all the relevant gear train is positive and free running.

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As for the white metal valve face this to has had the 5 hours running so thought it would be a good time to see what was happening here. I removed the 4 screws holding the front cover in place and lifted the rotating valve off the end of the valve drive shaft and low and behold the white metal surface was now a bright silver finish from the contact with the rotating valve there were no signs of excessive wear and the thin coating of white metal had not worn through.

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 You can see in the picture that there is no damage to the valve face or any tram lines so this could be a way to improve the A4 valve face if you wanted a cheaper option than to try and chrome plate the brass valve face on older engines but the chrome plate idea is with out doubt the best way to go.

Even the drive peg on the shaft has not worn through the white metal as it rotated and revealed the bronze bearing behind which as there is now no spring it takes the load off this area. Time will tell if the white metal idea is a good long lating solution but as said I would still say the chrome is the best option.