Tag Archives: leak compound steam

Shiny Things

While we await the 600+ cut and bent boiler tubes from the other members of the “Boiler Collective” beavering away in Sussex, we went back to the engine to try and close off the final list of “to do” jobs….

Cleading/Lagging/Cladding

I think Cleading is the official word for this, even though WordPress objects!

This is installed around the cylinder block to try to keep the heat in, raise the temperature of the block and reduce power-sapping condensation in the cylinders. (A thin film of condensate on the cylinder walls can apparently eat up to about 50% of the input steam in small (2″) cylinders according to this paper).

While on the face of it the Leak’s cleading can be quite simple, it still took two days of paper templates and careful nibbling of the 40thou stainless sheet I chose to use. This is thicker than often used, but I had discovered in using the same material on the 5″ Nigel Gresley I built, that is produces a far more robust job, and is much less prone to kinks and dents.

This was layed over a sheet of Kaowool blanket (with extra layers stuffed into the spaces) and secured with 2BA screws (temp ones shown in pictures) and I was quite pleased with the overall job.

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Condenser Mounting

The mounting of the ancillaries onto the engine always seems to entail many hours of contemplation and procrastination (see next bit). On the Leak the condenser was not discussed in the original Model Engineer articles, and while the drawings are available the mounting is left to the builder’s discretion.

I opted not to undertake the building of the condenser. and instead managed to purchase a second-hand item (probably for a Stuart Turner 6A) from Simpson’s in Coniston at a very fair price. I eventually decided to build some large “shelf brackets” from some 3mm brass plate in the “stores”, and attached these to the flat faces on the rear of the bed and columns that were originally meant to hold the air/feed pump assemblies and cross-head guide. Having polished them with those fantastic York abrasive rubber blocks that Cromwell stock they looked quite posh!

The Condenser Shelf Brackets

The Condenser Shelf Brackets

Clearly the condenser itself still needs a coat of nice paint!

Displacement Activity

The next task is to find a place to mount the lubricator pump, and this engendered a lot of head scratching and eventually got diverted into some classic “displacement activity” (things you do to avoid doing the thing you need to do!).

So I polished the gauges I plan to use… more abrasive-block work and a nice result…

Shiny Gauge Set

Shiny Gauge Set

Onwards…..

A little lubrication

While we wait for the plasma cut boiler plates and housing to arrive I went back to a job that’s needed doing for a while on the engine; the Lubricator.

Approaches to lubrication

There are several approaches to lubricating a steam engine, from a hand-held oil can (tends to be a bit erratic, and you chop the end of the spout off in moving parts) thru oil wicks, to pumped lubrication. I felt that a pumped system was the way to go.

There are 11 bearings that need lubrication in the engine (3 main bearings, 2 big ends, 2 little ends/crossheads, and 4 eccentrics). Actually, there is cylinder lubrication as well, but we are going to deal with that via a separate displacement lubricator which injects oil into the incoming steam (a sort of 19-century “posi-lub”!

There seems to be two approaches to pumped lubrication, either a single pump producing a pressurised rail, and then a set of individual needle-valves or calibrated jets. Or individual pumps for each bearing. Memories of failed cam-shafts on Ford Pinto engines in the 70’s steered me towards the latter approach, so that is what we decided upon.

A V11 pump

jim ewing-style lubricator

A Jim Ewing-style Lubricator

So, the conclusion is a 11-pump lubricator. These are normally arranged as a “V” to reduce the overall length. I have previously built one to Jim Ewing’s design (see pic) which worked very well on the loco. My first plan was therefore to build a set of these and then drive them from a set of cams.

However. for reasons I can’t remember I thought I only needed 10 pumps so, when I drew these up in ViaCAD I drew them with 5 cams driving these in pairs.

FIrst plan - a V10 lubricator - in solid modler

FIrst plan – a V10 lubricator – in solid modler

First plan - a V10 lubricator

First plan – a V10 lubricator

Sprag Clutches

The cams are driven by a pair of “sprag clutches“, which are small needle roller bearings which only allow the shaft to turn in one direction. So, by holding one still in the oil tank and putting the drive arm on the other, one gets effectively a fine ratchet mechanism that will convert any to-and-fro motion into a rotating motion to drive the cams.

Pump Units

However, I concluded two things 1) making 10 (actually 11) of these pumps would take a while and 2) you could buy similar pump assemblies from Lubetec (these are Interlube AC pump units) ready made… So that was what I did – here are some pictures of the final lubricator with 11 of the LubTec pumps fitted – smaller capacity (red) ones for the eccentrics and larger (yellow) ones for the mains, big & little ends….

Onwards….

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A fix for the Air Pump

So, following some communication with the steam boating forum we are all agreed that the Edwards Air Pump as drawn is missing  anything to hold the valve-plate in place, or seal its contact with the pump body. This means that:

  1. The whole valve tends to move up and down with the piston rod, (and I think this needs to be a “good” fit to prevent leaking round the pump-rod, so this is unavoidable).
  2. There is nothing to seal the lower valve plate (the one with the holes) where it sits on the ledge of the pump body…

So, my solution is to:

  1. fit a gasket under the valve plate
  2. make and fit a nylon block to hold the plate down – made 10 thou too long, so that the top cover provides some “squishing pressure”

As other members suggested this may help pump performance by removing “deadspace” (but it is beyond the valves so I am not sure if this is correct), and secondly it needed to be made in a way that ensured the outlet port is not cut-off if the block rotates; so, as can be seen in the pics below, I have made it with an exhaust annulus and internal ports to the valve chamber cut in the bottom…

I think this approach will also prevent the valve opening too far….. a test in the kitchen sink proves that it all works!

Here are some pics of the block and completed pump assembly.

air pump stuffing block in situ

air pump stuffing block in situ

air pump valve chest stuffing block

air pump valve chest stuffing block

air pump valve chest stuffing block

air pump valve chest stuffing block

Retirement Beckons!

A change of pace and circumstance

Well it seems I have not posted since November and the arrival of Befur’s trailer. Since then a lot has happened (so Happy Xmas, and Happy New Year)… I have had the fortune to be made redundant, and have (with Louise’s kind support) agreed to turn that into retirement – so from the end of February there will be no more working interruptions, and as I am only “on call” now, progress should be faster. So with the shingles finally subsiding, and hopefully the last of the winter colds and the left shoulder starting to free up,  there can be no more excuses – so 2015 looks bright indeed 🙂 Continue reading

The Impulse Valve (Simpling Valve)

I have puzzled over the drawings of the Impulse Valve for a year or more, and spoken to others who can make no sense of it.

Well finally last week while mulling the design over with a friend, he (I think) correctly fathomed how it is meant to be built and operate…

As drawn there appears to be a plunger in a tube which is operated by a press button. There appears to be no way that this would operate, as it would just admit HP steam to the chamber formed between this plunger and the end of the valve body….

The explanation is that this plunger is in fact a tube! Thus when depressed the steam is admitted to the end of the valve assembly, and then passes down the tube to the valve chest/cylinder. There are hints in the drawing that this is the game, but some of the views are incorrectly drawn which leads to the confusion – and actually I am not even sure it could be reliably constructed as drawn.

I think it would still be hard to make this valve steam tight, but in operation this might not be a practical problem…. Thanks to Neil Davis for figuring this out!

*Simpling or Impulse

In the ME words, Mr. Leak complains that many people incorrectly describe the Impulse Valve as a “Simpling Valve”, and he argues that this is wrong as it does not make the engine run as a simple (which is true) but just introduces a HP steam feed into the LP valve chamber to push the engine off HP TDC if it stops there.

He’s right in the description of what it does, but knowledgeable friends of mine tell me that within the road steam community (Traction Engines) these valves on compounds are always known as “Simpling Valves”… so maybe we can continue to use the term…

Setting the valve gear ….

Well as the videos below demonstrate we have the valve gear finished, and I managed to time it reasonably. There is some blowby on the HP, and that might need further investigation, but on the whole it’s OK.

I scratched my head a lot on how to set this gear, and while this might not be the “right way” and the setting is certainly not “perfect” – let me tell you how I did this….

Firstly we set the engine up so I could feed each cylinder from compressed air, with “ball-a-fix” valves to allow me to control the amount of flow, and which cylinder is fed. Also fitted a small pressure regulator to allow me to control the pressure fed to the engine.

This set up allowed me to turn the engine over by hand and feel when the air pressure was assisting or hindering this turning, and thereby determine if the gear was feeding the pressure at the right part of the stroke. Then one could simply say “is the gear ahead of the crank position?” (e.g. the air is being fed too soon, or cut off too soon), OR “is the gear behind the crank” (e.g. the air is being fed too late). It was then quite simple to slack off the allen screw locking the eccentric to the crank, use the key to hold the eccentric in place, and manually move the crank ahead or behind (forwards or backwards) to attempt to correct the error. I did this first in full-forward gear and then repeated the same process for the HP  cylinder, and then in full reverse (setting the relevant eccentrics).

Three or four iterations produced the results shown below…

Firstly running in (very) slow forwards

Secondly, a “video tour” providing a more detailed view of the various components?

The &^*$! reversing gear…

Well, if you’re building this engine then I hope the valve gear goes more smoothly for you than me!

The Draglinks

The Drag Link Bearings

Drag Link Bearing Blanks

A handfull of work, drag link bearing blanks ready for drilling boring, fitting and oil-hole drilling

I cannot believe just how long it has taken to complete the reversing gear on the engine – and it’s still not done.

The multitude of little blocks (drag-link bearings) take an age to make – if you had some 7/16″ sq Ph Bronze bar to hand then it might be OK, but I didn’t so decided to hack the blanks out of a piece of 2-inch square bar I had. However, I discovered that my trusty Warco bandsaw did not cut as straight as I hoped, and half of the resulting blocks were undersize. So then you spend a while silver soldering extra bits back on, to bring them to size, and then (literally) DAYS on the shaper, transforming a set of rough cut rhomboids into little cuboid shapes.

Drag Link Pins

Meanwhile a relatively simple turning and pressing job produces the pins for the lifting arms and eccentric pivots.

Drag Link bearing pins pressed into lifting arms and allen-screwed into expansion links.

Drag Link bearing pins pressed into lifting arms and allen-screwed into expansion links.

I happened to have some EN1A on the shelf that these got cut from – this is lovely free-cutting (leaded) mild steel, but I must confess I worry that this is so “soft” that it might not last well in service.

BTW – Midway thru the gear building I ran short of 1/4MS bar. So I went off to Metal Super Markets in Southampton (metalsupermarkets.com) and stocked up on a variety of bar and plate, that my “stores” were running short of; (these really are great people, and very helpful and economic – I would recommend them to anyone, over the counter service with a smile, for even small quantities) – But they only had EN3B, and when it came to turning and screw-cutting this stuff you really miss the free-cutting EN1A!!!

The only issue with the manufacture of these pins, is that one of the errors in the drawings means these pins need to be longer than drawn, to clear the bolts and lock nuts securing the Expansion Links and Die Blocks. There’s not a lot of space, so take care – I extended mine to 1.5″ overall (I think).

Drilling and Boring Drag-Link Bearings

drilling the bearingsThe next job was to drill the bearing halves for the rods. I did this by clamping them into a small jig (with tool-makers clamps). My normal approach to this would be to soft solder (“sweat”) the bearing halves together and then drill and bore them as one, separating them at the end. But this was not what the ME articles said – so I followed them… The plan was to create a small jig, drill half the blocks 2BA clearance and the other half 2BA tapping – then tap these and use temporary screws to assemble them into pairs while they are bored, and then open out both sides to clearance for the long rods to be fitted.

Jig Drilling DragLink Bearings

Jig Drilling DragLink Bearings

I think this approach was slower.  A better plan would have been to solder them into pairs while they were all still oversize, drill, bore, finish to size and then separate.

As it was I then discovered that despite machining all the blocks to size, the journals on the pins were too tight (only a few thou, but enough to stop them fitting, so yet more fettling was needed)- At this point I discovered that the relevant reamer has gone missing, so more careful hand work on pins and bores (scrapers and emery tape) was needed to get a good fit….

The Valve Rods

This is about to start sounding like the blog of a complete idiot, but at least it’s improving my patience.

LP Valve Rod

Firstly, while assembling and testing the valve gear (prior to first run on air) I found that the LP valve was fouling something and could not accommodate the full travel of the eccentrics, over a couple of hours of assembly, disassembly, reassembly (repeat as needed) I came to the conclusion that the tailrod was too long and clouting the end of the tailrod guide… there being no opportunity to lengthen the guide, I decided to shorten the tail rod – carefully sawed 1/4″ off, and reassembled again, only to find it STILL DOES NOT FIT!!!!!

Further inspection determined that the valve buckle was actually fouling the nut holding the tail-rod guide – and actually the shortened tail-rod was now falling out of the guide at the lower extent of the valve travel!!! So, it now needs lengthening – more work yet to be completed…

HP Valve Rod

The HP valve rod has a “joggle” on the bottom to line up the valve rod with the eccentrics. I decided to make this as a separate part and screw it to the rod proper. This joggle also serves to further widen the already widened drag-link pins resulting from the error in the drawings. I did measure this and allow for it in the longer pins – but I forgot to take account of the lock-nut on the die-block pin….AAAARRRGGG!!!

I concluded I could shave enough off the joggle to accommodate all this, but the amount of metal left for the thread holding the actual valve-rod into the joggle was going to be a bit thin, so I decided to braze the rod into the joggle – this I did (with no distortion), and decided to use the Linisher (belt sander) to just clean the flux and oxide off the joggle…. What I failed to see as I did the final side was that I was holding the assembly slightly out of square and ground a nice 20thou depression in the bally valve rod – thus rendering the whole shooting match scrap! 😐

Either way it provided me the opportunity to screw-cut the 3″ long 3/8″x26 thread on the new rod, using the off-set compound slide method often recommended (but never tried by me) mechanism – and it does a much nicer job (even on the nasty EN3B!), so I conosoled myself that the extra 3 hours work, had resulted in a nicer job (displays a fixed grin)!

BTW, In this process I again reminded myself that under conditions where you need to take fine cuts on tough material a carefully sharpened carbide or carbon steel tool will outperform a indexable tipped tool – as if you check the specs these are not typically made to make a cut of less than 5thou !

The Result….

Jig Boring the holes in the lifting arms for the weighshaft and drag-link pins

Jig Boring the holes in the lifting arms for the weighshaft and drag-link pins

Overall these 16 half bearings and eight rods and 4 pins took more than a 10 days of effort (probably about 30 hours! not including the remaking of the vale rod) – a slog…. assembling the whole sh-bang produced something that worked but was too stiff, so more fettling and adjusting needed!

I am really hoping I can bring this all to a good end – sometimes I wonder!