Building a B12

[gowest]

The middle axle is the one that drives the valve gear and I did give some thought as to how this would work on this engine the reason being that on all the Hornby engines the piston and connecting rods drive the middle axle and the gear on this middle axle then drives direct to the valve system so no loss of timing in the different parts. but on my engine S69 GER as I should call it not a B12 designed by S. D. Holden has the pistons connected to the first cranked axle but with the valve drive still on the middle axle so all that keeps it in time with the valve events are the outside connecting rods so any wear in these parts might result in poor timing and thus poor running. But we have not got to that part yet so will see what happens see the drawing blow.

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Still what’s that old saying “if if’s and ands were pot’s and pans there be no need for tinkers” I don’t know why I said that but in might make sense to some one.

Back to the job in hand some brass bar was put in the lathe and the middle axle housing was started on the bearings for this axle are smaller than the ones used on the cranked axle they were 6 mm outside dia these are 3/16 outside dia they have to be this small so that they do not fail on the large gear that mates with the smaller axle gear for the valve timing.

Along with this part of the job was to cut down the cylinder block which needed to be done before any work on this can be carried out and you can see just how much too long it was.

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With all the parts made for the middle axle housing the fixing holes needed drilling and the housing could then have these holes taped out 1.2 mm there would be 2 fixing holes each end and this housing would make up part of the frame stretchers.

I have added a match stick in an effort for you to get an idea of the size of the parts I am making all this with fingers like half a pound of pork sausages.

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The brass tube like part is the bearing spacer which is held in with a screw and stops the bearings moving from left to right.

The unit fully assembled ready to fit in the frames. 

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You can see these very small bearing which even have dust covers on.

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[96RAF]

Great stuff GW. I know the problems with pork sausages coupled with varifocal lenses, etc.

 

For the benefit of those not aware of these things - Bearing Basics 101:

 

2 main types, ball race or roller (includes very small rollers called needle bearings). In either metric or imperial sizes.

 

Each can be single or double row and straight as show in GW drawings or tapered like the wheel bearings in an older car. Tapered bearings have to be used in opposing pairs to take end loads. SIngle row ballrace are normally known as thrust bearings as they can carry end loads.

 

Any bearing can be open or have seals, which can be on one or both sides and be either metal, like GWs or rubber or synthetic to hold in lubricant and resist environmental issues. An open bearing for instance could be used in  gearbox where it would be submerged in oil. Sealed for life bearings could be used in the food industry or in corrosive environments like underwater.

 

Designation of a bearing is type code, OD (diam of outer race) x ID (bore of inner race) x width plus seal designation (1 or 2 and material code). Race is the shaped track that the ball or roller races around on.

 

Cross ref catalogues can be downloaded from most bearing manufacturers web sites, showing each manufacturers equivalent of others products.

[gowest]

There's a man that knows his bearings 

[RB51]

I can't think of any more superlatives. To know what to do and then do it at such a scale is impressive beyond words. I too look forward to reading more. Well done GW, fascinating stuff. R-

[96RAF]

There's a man that knows his bearings 

 

The ones I worked with were around a foot across and a tad heavy. They occasionally failed so you can imagine the loads they carried.

As an aside - there was a tale by a bearing rep one day about how a customer had moaned about poor longevity of a certain bearing used in a gearbox for a wind turbine. Upon investigation it seems this gearbox had been running for 5 years on the inhibiting oil put in during manufacture and which should have been drained and replaced by the proper grade upon commissioning. 

So always keep your bearings lubricated with the proper stuff.

[gowest]

Now with all the wheels in place and the outside connecting rods fitted all the bits that should go round did and all the bits that went up and down did with out any tight spots the only thing that had drag was the pistons doing up and down in the cylinders but once run in may be this would clear itself.

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[96RAF]

Looking at the overhead shot GW - the piston binding is probably due to the offset of the con rod(s) Causing binding on the crankshaft webs.

 

My suggestion would be to either beef up and slot the little end(s) or make the piston rod connector and little ends half lap offset to better align the con rods to avoid binding on the crankshaft.

 

Of interest how durable is brass for connecting rods or is this a mock up for steel ones later. If steel do you then have to look at soft bearing faces.

 

Last question - will the third axle benefit from the same bearing assembly as the centre axle. 

Rob

[gowest]

Well spotted Rob about the last axle not having any bearings have one or two ideas as some sort of movement up and down maybe needed to take out any odd bits in the track 

as for the con rods yes I did draw up a fork type fitting for the small end which will dissipate the energy equally on the small end pin assemble as for the brass con rod steel with bronze bearing might be the answer but all the Hornby engines are brass running on Stn/steel and its the Stn/steel that wears first if you look at the Hornby crank pins.

I have on some of my engines remove the Hornby middle crank pin spacers and make the big end up wider with a brass spacer soldered to the back of the connecting rod this gives it a larger bearing surface. 

I just thought how the other parts that go to make up the valve system will fit in the chassis so the complete wheel assembly was really done for this reason and some problems are around the corner like the Hornby oil tank will not fit in the smoke box and the valve rod is too high on the engine to mate with the large bevel gear assembly which I will go into later.

thanks for your in put and all these points that you brought up will be looked at in detail when it looks like this engine is going to work Thanks

ken

[gowest]

Following the success of the fitting of the wheels it was time to make a start on the valve assemble. Looking at the layout for this engine seemed to suggest that there will be many new parts needed to made to complete this part.

Beginning with the middle axle as this is where the valve drive is taken from for the rotary valve system.We have the axle and its gear in place the next part is the gear that mates with this axle gear which is even on the Hornby engines lager than the width of the frames so will need a slot cut in the frames to allow the gear to turn with out failing the frames the Hornby part pictured here is fixed in place with 4 screw threaded into the frames and as these frames are only .5 mm thick, brass blocks will need to be soldered onto the side of the frames so that a fixing point can be achieved with screw threads.

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Once this gear assembly is in place then the cylinder block needs to have the Hornby valve assemblyfitted and the steam passageways drilled or milled in place I am lacking parts for this next stage so I may have to borrow them from one of my better engines which is a shame as these I did not want to touch as they are the best in condition and runners not like some of the other engines I have cannibalised

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If you look at the second picture you can see that the drive is taken from the small gear onto the larger gear on the valve shaft indicated by the arrow. its worth noting that on these later A3 the valve block is chrome plated which on engines i have worked on show no sign of wear unlike the A4's which in plain brass do tend to have a few tram lines in the valve ports area. 

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The other part which looks to be too long is the brass valve cover, to over come this I can machine a millimetre off and counter bore the top 2 fixing screws this then will let it into the body of the smoke box a little better.

The valve drive shaft is also too short so a new shaft will be made this shaft not only drives the black rotating valve but has the exhaust steam passage way drilled in it and the under cut that also has a small hole to line up with the end drilling.

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You can see from this picture just about that the cranked axle needs to miss the small gear assembly and that the valve shaft is about an inch too short and looks to be to high.

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[96RAF]

Interesting problems Ken.

 

Rather than teardown a known good loco could you not just mock up space models for now until parts become available.

 

Peering at the pictures and bearing in mind what you said earlier about providing some springing for the third axle, would it be better, but maybe not accurate, to reverse the outside connecting rods to have the articulated bit at the back and the solid bit connecting the centre and forward axles which could help with stiffening up the valve timing path.

 

Rob

[gowest]

Hi Rob

very good point most engines do have the rods the other way around and would be a better idea. As for parts did wonder if Hornby might help out but have not had any contact yet I have bought some parts on flea bay o might be ok for a bit.

[96RAF]

As for parts did wonder if Hornby might help out but have not had any contact yet I have bought some parts on flea bay o might be ok for a bit.

GW - Please contact me either via Adam or from the email on the contact page in the link in my signature.

thanks Rob

[gowest]

Fitting the valve drive is getting to be a pain all the major parts don’t seem to want to fit as I wish but that’s always the way you solve one problem and 2 more pop up. 

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The idea I had in the end for fixing the valve assembly to the cylinders was to mill down both sides of the valve block but at an angle making a greater fixing area at the bottom but giving access for a screw driver for fitting this did not encroach on any of the other parts that are fixed to this unit.

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The bottom picture shows the fixing holes drilled in place ready to be transposed onto the cylinder block.

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So going back to the transfer gear assemble as was said I think the frames needed 2 slots to allow the large black bevel gear to hang out through the frames this was filed in place on both frames.Then 2 brass blocks were soldered to the frames to give something to fix this gear assembly to.

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You can see the frames and the brass blocks and the gear assembly which some Hornby Steam operators will have come across before no doubt.Every time you make a part you fit it see how the rest of the parts go that have to mate with it and it was on one of the assembles that I could see the large black plastic gear on the valve shaft was not going to mate with this gear assemble. This was because the my cylinder block was higher than the Hornby ones. I could reduce the metal on it but this would make it harder to drill the passage ways in and might also fail the inside crank and as it was only a small amount I decided to angle the gear assembly in an up would direction.

You can see in the picture here I hope what I mean this all seemed to work well and was some thing that I did on the 9f as the cylinders on that engine are angled to the axle not straight like Flying Scotsman.

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When the gear was turned the axle revolved and tooth mesh looked to be good so things were coming along fine but then problem with the cranked axle in place not so good the webs of the crank hit the gear shaft and gear as in the picture below so some changes were needed to over come this small problem

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I dismantled the gear assemble and milled off about 1/32” of an inch from the body and also reduced the shaft length on refitting the gear assemble the cranked axle rotated and did not hit the end of the gear. 

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[96RAF]

All these mods must be eating into a scarce supply of already very rare parts GW?

 

It would be good to see Hornby showing an interest in this ground breaking work and maybe lending you a bit of support.

 

Maybe Adam could flag this thread to the Live Steam guys at Hornby.

[gowest]

Hi rob

yes parts are a problem and when you think that once mods are carried out like in the valve body above it will not fit straight back into my A3 anymore.

At the end of the day I'm just happy to jog along and problem solve as we go With what ever parts I have.

[gowest]

if it helps i have drawn up the Flying Scotsman lay out of parts so you can see what does what? 

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[96RAF]

Good diagram GW, that gives me a better understanding of the way it works and how the major loco parts assemble and interact.

Rob

[gowest]

A new valve rod assembly was designed because the Hornby valve rod was too short and the valve timing adjuster would not work in the standard Hornby layout as the cranked axle big ends hit on the valve setting unit.

You see the drawing and its basic assembly here and as this engine has a lot of space from the valve unit to the electric motor servo unit the space up the front end near the cylinders was the best place to move the valve setting assembly. A cigarette packet idea was scribbled out of which I had in mind and once in the work shop things started to take shape.

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A new valve rod assembly and all of the new made parts.

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Once fitted in the engine things were looking good and the crank axle turned once more with out hit any of the valve rod parts, what is it the RAF used to say about planes that look right?I was now having a much better feel about this engine and that it might just work?  Or have I spoken too soon.

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I still need to check a few things as we get nearer to finishing this stage of the valve drive instillation which when done would mean I could connect the engine to some compressed air and see what happens.I need to finish the valve rod end with its exhaust passage and that little ear that drives the rotating valve and the bit I reluctantly leave out the steam passage ways in the cylinder block./media/tinymce_upload/859ba04fc235bb188b6aea74eecddc53.jpg

I have checked to see where the exhaust comes out and it looks to be bang under the chimney so the steam should just blast straight up (if it runs) my father was in the signalling department and once working on a gantry signal a light engine came along the track and with the regulator shut it made no noise at all and as it got almost under the signal the driver whacked open the regulator almost blowing poor old dad off the signal in smoke and fumes. O how the crew laugh, not dad.

[96RAF]

Thats looking good GW. I think this one is going to be another good 'un.

 

If it looks right then it usually is right. A good maxim. You could tell if an older aeroplane was going to be a duffer just by looking at it. Nowadays modern electronics, computer controlled aerodynamics and mega power ratios mean that you can get anything to fly, no matter what shape, e.g. F117 stealth fighter and B2 bomber, which would not have worked terribly well on manual controls.

[96RAF]

@GW

 

Looking at the way she sits on the wheels at present Ken the front bogie may well be required to carry out its design duties of load carrying, all depending upon what weight distribution the rest of the working parts bring to the party.

 

Rob

[gowest]

Hi Rob

you are right it is front heavy and had this with the SR schools engine that I built this is why the rubber tyres are on the front drivers but as you also point out that a few more parts need to be added so it might all pan out. Like what you said about aircraft and how modern electronics and fly by wire keep them in the air People do this with 00 gauge stuff now you can even use you phone to operate them I'm told.

[walkingthedog]

Hey RAF we had a flying wing decades before the B2 and it worked well. The F117s have all gone, not sure why. 

 

Gowest as I've said before this is without doubt the best post on the forum. 

[96RAF]

Hey RAF we had a flying wing decades before the B2 and it worked well. The F117s have all gone, not sure why. 

 

Gowest as I've said before this is without doubt the best post on the forum. 

A flying wing although very efficient has no natural stability so the old Northrop and German ones had to be hand flown constantly correcting any excursion. The UK ones by Handley Page, Armstrong Whitworth and deHavilland were never fully developed except the latter probably led Avro to designing the Vulcan. F117s ran out of fatigue life AFAIK.

 

Definitely the most interesting post. This is why kids should be encouraged to take lawnmowers and bikes to bits so they can go on to projects like these.

[walkingthedog]

Didn't last long did they. I know they tended to fall to bits. 

[gowest]

It's a shame I think we all live far away I could see use now up the pub going over planes boats and trains over a pint. I still have a B25 90 % built with a 5 ft wing span and has been that way for the last 40 years so don't hold yer breath To see it fly?