A last quick post for the day, then it’s back to the cold workshop….
The pump drive on Befur has been an on-going source of angst and failure… So we redesigned and rebuilt it!
This appears to be much better, and pending final cleaning, plating etc. here is a video of it in action on the bench!
Befur home for winter work
Well, Befur is back in the fells for some winter work.
The pull-out and trip home was uneventful, thanks to Simon and Dean’s help, and the garage finally finding and fixing the leak in the Land Rover’s turbo pipes! Much less smoke and much more go!
We have a tentative list of work we want to do, and the game plan is to try to get back into the water before Heggerscale freezes (the lake is a milder climate to over winter in)! However, as I write this post, and document the work, it seems questionable if we will finish the work in 2022!!!
The work falls into several groups, some just inspection/maintenance and some fixing/improving: Continue reading
Following on from the Boiler test, and a quick trial we identified just over 20 items that needed some attention. So a week later, with all these items fixed (from leaking valves to painting and plating valve gear components), we are ready to try again. Continue reading
You will have realised that I am a bit of a sucker for ageing lumps of cast iron in need of restoration. So I could not resist a circa 1940 Worthington Simpson Steam Pump that Mark Rudell offered to me. It seemed it would serve well as a boiler feed pump or circulating pump for the condenser. (providing I could ignore the fact that it’s about 5 times the size we need – but hey the designer said I needed 500KG of ballast in the bottom of the boat, and given I can barely lift this beauty it’s all grist to that mill!) Continue reading
Well the 10th November 2017 marks a major milestone – the boiler passed its initial inspection and steam test, and is now certified for use. (big smiles all round).
Sadly, everything was too frenetic to take pictures during the steam test – but here it is just before we pressed go!
John, our inspector from SBAS Ltd (the SBA’s Boiler Inspecting Company) had been booked to arrive at 3:00pm – at 9:00am I set about final sealing of the try-cocks on the sight gauge – at 1:30pm I nearly called to cancel the appointment as no amount of fiddling and fitting would make them seal, with a constant drip from each of them at anything above 50psi 😦 Continue reading
Here’s a better video (with iffy commentary) showing the feed and air pumps (and alternator) drive in action.
The Edwards pump is working, but I’m not sure that the flap valves are holding pressure (as it seems to have to start from atmospheric on each stroke…) but clearly the ball valves on the feed pumps are very sound (they actually hold 50psi for hours)…..
enjoy…
The plan is to work with the seasons and transition from boat building when it’s warm to mechanical engineering when it’s winter – and we are clearly heading into spring and temperatures in the boat house are becoming tolerable, and suitable for working with Epoxy; however, I was loath to make the switch back to boat building until I had concluded the design and construction of the pump and alternator drive assembly.
This has proven a very slow process, and as my good friend David Mattingley pointed out there is a world of difference between building something from drawings and designing and building from scratch.
Isometric of the planned pump and alternator assembly
I used PunchCAD’s ViaCAD 3D to draw the basic arrangement of this assembly, and this solid modeler was a new experience for me having previously only used 2D CAD systems (like Autocad). With this new solid modeling approach you manipulate 3d objects (cylinders, cubes etc.) to construct a computer model of the thing you are planning to build. You drill holes in things (by subtracting a “hole-sized” cylinders from the object) and merge primatives to create more complex shapes (like the alternator and gear box in the attached pic). This approach allows you to see clashes of components and get a good feel for clearances and shape of the final assembly. It requires a very different mindset. When the model is complete it is possible to create dimensioned 2D drawings of each part (although I confess I found it hard to get this feature to provide exactly what I wanted.)
This got me to phase 1, with the worm box, chain-wheels, v-belts and alternator all in position, and running smoothly (although it did not predict that the chain would need a tensioner as the centre distance I had chosen for the chainwheels forced us to fit a chain that was almost exactly one link too long) 😦
The lengthier part of the build/design process was to then mate this assembly to the air and feed pump assembly we completed a month or so back.
I had decided to use the worm-box output shaft to drive two cranks, each being used to form a scotch crank assembly (see this nice video if you are not familiar with how a scotch crank (AKA Scotch Yoke) works). This meant I could remove the uneven stress on the worm box if we only drive the pumps from one side. It became clear we should mount the pumps over the worm box, to avoid adding too much height to the engine assembly, and so an arrangement with 4 “side levers” running down from the pump crosshead to the scotch cranks seemed right. Mounting the pump assembly required a stiffened plate which I fabricated from some 3mm Brass plate I had in the “stock pile”.
The cranks are fitted to a keyed shaft, and each crank pin is 10mm silver steel. I found some thin section ball races (10mm ID, 15mm OD and 4mm wide) from Bearing Boys, and used two on each crankpin. However, I was unsure of the load capacity of the bearing, and the spreadsheet I had constructed for the pumps suggested that the four bearings needed to support a dynamic load of almost 100lbs (when pumping @ 200psi), and while this theoretically would be shared across 4 bearings, this would require “perfect” conditions. During an initial test I accidentally jammed a plastic mug! into the assembly stalling the engine – this resulted in two of the bearings failing with split outer races. I suspect the jam caused the bearings to be axially overloaded, but none the less this failure was worrying.
I contemplated fitting needle roller races to raise the load capacity, but as an initial “fix” I fitted 3mm thick outer “retaining rings” in silver steel to the bearings to strengthen the outer races… with this fix in place and some hose pipe to prime the pumps I ran a test with a pressure gauge on the feed line, and a 200psi safety valve to regulate the pressure (as you can see we reached over 250psi in practice).
As the video below shows we appear to have a working system (with hints of Tardis – don’t you think!!!) – the variability in pressure is to some extent caused by the safety valve, but also I think the pump valves may be slow to seat…
I feel I can now get on with the “wood work”, with a job well done!!!
The last 2 weeks have been devoted to two topics:
Well, the last week or so has been dedicated to finishing the air pump and feed pump assembly. The original owner of the castings had partially machined and assembled the main air pump castings, but they needed “fettling” to fit. This ranged from minor adjustment of PCD bolt holes, replacement of pump rod, and other minor work thru to remachining / truing of all of the mounting faces, fitting o-ring to undersized piston, reboring the feed-pump rams (to provide increased capacity needed for geared-down operation), the making of all the feed-pump valves and manufacture of all (bar one) of the pipe unions.
This involved a variety of odd-ball threads… I think this assembly now includes all the following:
The larger ones of these were either entirely screw cut on the lathe or screw cut and then “chased” with a standard split die. With the new insert/index threading tools this all went really well.
Interestingly (and as a demonstration of the value of “keeping everything”) a great many of the bolts on the engine are 1/4 BSF, and luckily at a club Auction at Guildford Model Engineering Society (I used to be a member), I managed to purchase a bucket of 1/4 BSF Allen Bolts for about a fiver …. I just had to look after them from 1985 ’till now to find a use for them!
The assembly also needed a number of gaskets (about 7) and these were all cut using a ball-peen hammer and centre punches to tap them out from the components they were sealing. This is such a simple and effective process (but one that many people seem not to know) that I included some pictures of the process in the slideshow below….
(also see link about drawing errors on this part here)
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
SY Befur 