This time we are looking at how to fix the problems with the Leak’s valve gear design. This is now part of our Leak Hints and Tips section on the known errors or problems with Leak design……
As we get to the end of January 2022, the tuning/rebuild/shopping of Befur’s engine continues, once this is complete we can get on with the list of hull and fittings-related work. But it seems we should at least explain what work the last few months have contained…
As you may have seen from earlier posts, and here we are embarking on a major winter “shopping” of Befur, to address a number of problems.
Measuring the valve timing on the bench
One of these tasks is to analyse and reset the valve timing of the engine to improve efficiency and performance. Continue reading
While these are not drawing errors, they have emerged over the first 3 seasons with the engine, and should be considered by builders.
In the BOOK the designer suggests using Araldite? as a jointing/sealing material… its not a solution, particularly for this joint.
The joint between the HP Valve Chest and the HP cylinder is problematic, as the sealing faces are very thin, and the two components are only secured by 4 bolts, which are hard to tighten and not well positioned to ensure a steam tight joint.
My first attempt was using “SteamSeal” jointing compound – this failed quite quickly.
The second attempt was using “Heldite” jointing compound – this failed within a few hours.
My last attempt was using “Oakenstrong” gasket paper, I had resisted this, not wanting to affect the overall block dimensions. However, rebuilding with gasket paper and jointing compound (Heldite) does seem to have cured this problem.
I spent a long time chasing a knock that appeared to come from the LP small end. Rebushing the piston rod and a new pin did not cure this, and it was clear that the pin was suffering.
This was finally cured by increasing the size of the Lubtech pump units feeding these bearings and slide ways. A “black” one (0.1cc/stroke) silenced the knock instantly.
I am sure that a better builder than me might make the sideway fits better, but the lubrication points at the bottom of the piston rods have to lubricate the “small end” and the slide-ways, and so need a heavy oil flow to ensure that both bearings are supplied on each cylinder, as I think the oil preferentially flows to the slide-ways, starving the bush at the lower end of the piston rod.
A quick note on where we are at, while we wait to hear from Windermere Lake Wardens on our application for a berth at Ferry Nab next year….
The boat is back in Heggerscale, and we are working on the following items:
Masthead fitting, with halyard crane, and other blocks for various parrels and lasy-jacks.
The next bit of this process, is to fit the masthead fitting (pictured above), (with navigation lights, VHF antenna and various shackles and blocks. Then we will cast a hard rubber square block at the foot of the mast, to secure it in the tabernacle base – the only problem with this is that the rubber components say they need to be mixed and poured at over 20-degrees C to cure, and it’s currently about -5-degrees C….
Having “finished” and tested my engine there were a final set of issues that I suggest you keep an eye on:
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
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
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:
So, my solution is to:
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 valve chest stuffing block
air pump valve chest stuffing block
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?
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!
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…
SY Befur 