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 →
We have turned one eye to the business of the drive train and prop-shaft for Befur.
I have concluded that I am putting a CV joint in the drive train, to allow the engine to be mounted horizontally, and also going to use a toothed belt drive from the engine to the prop-shaft, so allow me to install the engine off-centre, and improve internal layout.
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 →
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?
I couldn’t resist the temptation to see if the engine would turn with the newly finished valve gear.
I hadn’t finished the reversing gear and used some bungies to hold the expansion links and set the eccentrics by eye, and after some tweaking of the valve rod lengths to get the valves something like central, applied some compressed air (via a manifold to make it a high pressure twin)… and it turned (smiles all round)…
Sometimes you just have to face the fact that things are not going well – and lift the lid off the scrap bin and cast out that the bit you have been carefully crafting and toiling over, in the knowledge that it’s for the greater good 😦
And so it was with the crank and main bearings…
The fabricated main bearings were just not a good solution, and the approach I had taken to machining them had resulted in dimensional errors that needed “uncouth” solutions (shimming etc.) to get them right. Moreover the crank would not press up straight (even after peening the webs to remove post-press distortions.
After much soul-searching I concluded that I needed to bite the bullet and re-cut the main bearing journals afterassembling the crank – this means that the bearings would be oversize, so would need re-making. Having reached that point I decided that I should re-make them from a block of solid gunmetal (a 62mm square block 7-inches long, only £160!) as the cast blocks from Camden were too small to fit the over-size housings that the base castings arrived from France with….
Cutting the main-bearing material in half, to fit it back together!
As always, coming to these “scrap and start over” decisions is accompanied by much wringing of hands, but delivers a calmness that lets you sleep better….