Tag Archives: drawing errors

Relief Vales and Drain Cocks

An experiment – Steam Operated Combined Drains & Relief

Much earlier in the process I baulked at drilling the cylinder castings for the cylinder drain cocks because they looked hard to drill with out risking damage to some rather expensive castings. Moreover, previous experience with manual cylinder drain cocks on the loco had been poor (leaky, difficult linkages etc.) and on the steam launch most people seem to opt for 4 manually operated cocks which involves a deal of “faffing” in use. Continue reading

More Engine Work; Valve Setting etc.

For about a year now I have been saying “Yes, the engine is done, apart from a few bits and bobs” – so the other week I found myself waiting for some timber to arrive and decided to just “knock those bits and bobs on the head” – 10 minutes inspecting the engine revealed that there were in fact (at least) 23 jobs still to be done!!! So so far we have spent two weeks reducing this list to 7…. (and deciding to do some much later!) Herewith some notes on some of this activity… Continue reading

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

Don’t think the air pump will work

I think there is a problem with the air pump design/drawings…

This looks like it’s not a problem with the drawings, so much as an oversight in the design…

The outlet flap valve assembly is not fixed/located by anything vertically within the outlet chamber… neither is the lower valve plate – part 3 on P20 of the book – (the one with the holes)  sealed against the lip it rests on above the cylinder….so (as I noticed when I completed a trial assembly) the whole valve (both plates and the rubber washer) move up and down with the piston rod, and even if the vacuum held it down, I feel sure any hard won pressure difference would be lost as the air leaked back into the pump round and under the valve plate.

My current plan is to make a nylon “block” which is a light push fit in the outlet chamber, has “ports” to let the air-water out to the  delivery port, and is slightly longer than the available space, so that when the top cover is fitted it will press the lower valve plate down onto a gasket I am fitting under the valve plate….

does anyone have any better ideas/opinions? am I missing something?

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…

Stud Clash on LP Valve Chest

There is a clash in the drawings between the bolts holding the reversing lever slider pivot (shown in the scrap drawing on page 33 of “the book” entitled “Reversing Arrangements”, and numbered item “2”) and the upper-right stud securing the LP Chest to the LP Cylinder….

Having hit the problem, I moved the pivot in-board about a quarter to miss – I now have an ugly hole to plug 😦

Also take care, I think the original hole locations in the pivot are also incorrect, as they seem to result in the slotted arm (item 3 in above drawing) fouling the studs on the LP valve cover. So I made mine (the 2nd one!) a bit longer and located holes by eye.

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!