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Author Topic: The paddle saga  (Read 939 times)

Offline John S

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The paddle saga
« on: September 23, 2020, 03:28:24 AM »
Well not sure if this is the right place nor of anyone will have the patience to wade through the waffled accounts of the saga. It started last year, 27 December actually when I awoke with pains in the chest, a short time later and with the accompaniment of flashing blue lights and wailing siren I was dumped in the emergency department of the Hinchinbrook Hospital in Huntingdon UK.  They came to the conclusion that I had been subjected to some plumbing problems within the chest but not having a suitable scanner I was a couple of days later whisked away to the Royal Papworth chest hospital in Cambridge where it was decided I needed a bity of surgery so on the 9th January they sawed through my bits and fitted a quadruple bye pass so that was the start of my year and led to more relaxed activities than normal. So what to do once back home became the task of the following days not settled until after the arrival of a rather battered 79 year old back home.
While idly searching the internet I cam across Medway Queen being restored and it took my fancy so joined the preservation society and found they sold a set of drawings that could be used to create a model so more cash sent towards restoration was sent and plans duly arrived in the post. Not too difficult it seemed and one view was a reduced copy of an original builder plan from 1923/24 (she was launched in 1924). Plans were redrawn to suit the width of the car which as for many is the limiting hull length factor and the search for a suitable engine design was, well I hate to say it but will launched. #It had to be similar in appearance to the original inclined compound engine and I found the Stuart Turner compound launch engine mounted at a 20 degree from horizontal angle  the cylinders were a good match for the  redrawn plans so I embarked upon a voyage of re designing the rest of the engine to be a real paddle engine. This exercise  was helped by  already having a machined cylinder block to hand with pistons and covers. I did end up with a scheme that looked good so cast the entablature from aluminium and machined to suit, crankshaft for the 1 inch stroke cylinders machined from steel bar as a single piece, connecting rods made with typical square sectioned slide bars and once tacked together when the crank was turned by hand bits went 'up and doon' in the peculiar sequence of a twin cylinder engine then plans changed. Not sure if I really should carry on but will at the risk of condemnation by readers.
I began to realise that although Medway Queen is a lovely ship and the reconstruction of a new hull is well documented with words and many photos she was as pleasure craft and lightly built (hull plates were but 1/4 inch thick and now are 6 mm) she would be rather tender so ideas changed until I came across Strongbow the plans for which were duly sorted out on the computer to some unusual scale of the largest frame fitting on an A4 sheet of paper, this size was dictated by my home made CNC router not taking a wider sheet through the gantry carrying the cutter, more plans therefore drawn saved and the sections printed out. Next the engines were the thoughts, by then I had come across Eppleton Hall with side lever engines, much more interesting than inclined so new engine schemed out and some parts made such as cylinders, beams, built up crank and typical of mid 19th century power so all looked good then..... I came across Empress sadly scrapped but the important thing is her engines are still around now in Wales having been moved from Southampton to a museum where they have actually after some work got the engines running (very slowly and jerkily because of low steam and umpteen years of no turning). At last something that really captured my imagination so schemes worked out for a big oscillating engine based upon the few photos I have. Various new parts are needed but many from the inclined engine are being re-used for the third time but a little problem remained and it took weeks for a solution to be arrived at. The Empress had engines by John Penn and naturally were fitted with his valve gear driving the slide valves. I had considered the Harris paddle engine but that uses semi rotary valves that are not at all what I want but eventually I found all I needed to know on the Penn valve gear. You will all be pleased to know I have nearly finished this introduction to paddle steaming again after a 30 year break. An engine that fits between the hull frames is part constructed and will be 1 inch bore x 1 1/4 inch stroke to suit the cylinders made for it from bronze and being vertical just fits between the bottom of the frames or rather a platform across the middle frames with the crank at the correct height as it will be direct drive with no gearing. The boiler will be 5 inchers diameter x 4 inches long with twin 1 inch bore furnaces and if I remember correctly 24 5/15 inch flue tubes as it is a proper scotch boiler based upon the designs by Harris and Westbury with one or two other designers ideas thrown in. You may query my choice of big cylinders and direct drive but it is all to do with the dreaded Three bar Litre restriction so the boiler has a total water capacity or rather internal volume of around 6oo ml so in theory II can use up to 50 PSI and still remain withi8n the limits but more important than higher pressure is volume of steam at say 30 PSI hence fast steaming boiler wit auto boiler feed and burners controlled by pressure so again automatic but need now to interpret various designs for both control systems next the closing bits.
Meanwhile the hull has not been forgotten  and the reason for proportions coming to light. As ?I said I am limited in size when routing out the frames to the maximum width of 197 mm which appears to dictate a spacing of something like 63 mm which should not be a problem but in view of my heavier than normal model engine and boiler  I was getting a little concerned about displacement so have added three more frames to fit the central section of the hull which is conveniently parallel in section and this of course has changed Strongbow into a Longbow  vessel. The final section of this epic saga is close now. Frames duly fretted out over the course of a few days as my laser might have cut the paddle box fascia from 1/32 ply (4 pieces to be laminated later) but would not cut through 4 mm birch ply, well maybe after about 10 passes it might have done so. A 5 feet sheet of 4 mm ply bought to cut the keel out as a single piece purchased and the last session of making sawdust was to rout out 24 strips of wood to a common height of bottom of groove 4 mm wide and actually about 10 mm deep into which the frames will drop thus positioning them. Each block will be screwed to the building board and as the frames were all machined to a common height above the keel with notches at the deck and bulwark levels I am almost ready to start fixing planks in place however a slight problem remains. I have some 250 feet of sawn strips 18 mm wide and 4.5 mm thick that need reducing in thickness and width ( I did ask the other day for plank size  thoughts) but now I am having to make a small thicknesser/planer for this although the strips can be sawn accurately using a channel guide on the band saw.
I must add my apologies for this rather long winded account of how I have arrived at the present state so will not be offended by adverse comments upon the length but just a couple more lines remain. new 8 channel radio outfit purchased as my aged 2 channel 27 MHz Futaba with brown or blue crystals is not quite up to modern needs and just to be different the Medway Queen has a steam steering engine which is not much different in  principle to a modern servo so that to a suitable size is almost ready to be tried on steam as well.
Again profuse apologies offered.

Offline derekwarner_decoy

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Re: The paddle saga
« Reply #1 on: September 23, 2020, 07:04:28 AM »
John.......about the only matter missing is the need for early consideration of Scale displacement [or available weight] of all matter comprising the scale vessel...something like... :whistle

1. decision on vessel to build
2. scale chosen?
3. scale displacement?
4. materials chosen & their weights
5. weight of steam plant and associated componemts

Then Points 6. to 600. as envelopes or baskets for expansion of the content  :a102

A number of model builders miss these early stages of understanding and end up with a model that has never seen water...

Derek Warner

Honorary Secretary [Retired]
Illawarra Live Steamers Co-op


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