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Author Topic: Powered tin Bath?  (Read 394 times)

Offline John S

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Powered tin Bath?
« on: October 10, 2020, 05:52:59 AM »
Well not big enough to sit in but a 1 inch scale version of Monarch although I have increased the draught by 25 mm partly for a bit more stability but also to get the 5 inch diameter Scotch boiler as low down as possible. An ideal subject for lazy builders, flat bottom, vertical sides and no compound hull curves. Apart from seating, mast and a few items for mooring purposes the only other item is a toss over the side anchor that in one photo shows it having a bit of rope tied to is so no fancy anchor wench needed. Hull is being built from 0.5 mm electro galvanised steel, soft and easy to work especially as everything is flat or has a gentle curve. Although I have added a bit under water that does spoil the rise from bottom up to transom shape I can live with that and anyway should be under water so not really visible. It is a pity I could only get a metre long sheet of steel as it means I have to add bits each end so although the datum line is the paddle shaft a folded bow section will be fitted that should stop it cutting through any duck that gets in the way as it will now be rounded. A similar length section at the stern bent to form the transom as well as the remaining part of the hull bottom. In general I am following the way that the modern canal narrow boats are built so will add some angled ribs but how many depends upon what is found after the first floating with boiler and engine parts in the bath (when Elizabeth is not around of course). Machinery will be the inverted oscillator with Penn calve gear and a 5 inch Scotch boiler with about 24 5/16 inch flues but have not yet decided whether a single gas furnace or two will be fitted so will need to make an auto flame control to find out how well the flame can be controlled. The engines are 1 inch bore x 1 1/4 inch stroke directly connected to the paddle shaft so will not need a very high boiler pressure to operate and if I calculated the internal volume correctly that should be about 0.6 Litre so a 40 PSI pressure will still be within 3 Bar Litre although the boiler will be built to aged Model Engineer standards and I usually hydraulic test to 200 PSI ( Remembering LBSC of course  who set me off building steam locos ) and that has served me well over the past 65 years building steam engines and boilers.
Monarch is again up for sale and if we win the lottery I will be down to Wareham with a skip load of shiny 1 coins to bring her back to Peterborough.
            Well we can all dream can't we.

Offline DamienG

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Re: Powered tin Bath?
« Reply #1 on: October 10, 2020, 09:07:51 AM »

Offline John S

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inverse Tin Bath tin Bath?
« Reply #2 on: October 14, 2020, 04:17:58 AM »
Basic soldering done to time for a leak test so filled the shell up with water, a couple of pinholes need attention but maybe more once I have finished cleaning up the solder that leaked out here and there, well mostly there  but at least I know it will not sink due to a major leak but floatation testing is a long way off although it would be sensible to see how well it supports the machinery and boiler. Even half full it felt rather heavy  when I lifted it up to empty the water out taking care to avoid the fish pond as the flux used is water soluble and approved by the Water Council for use with Potable Water so perhaps the fish might not have suffered if I had spilt the soapy looking water in with them.
Basic details then. Based upon Monarch (now up for sale again), 42 inch long, 7 3/4 beam plus paddles, weight 4 pounds or 1.81 kilo so not very heavy considering it is made from 0.5 mm electro galvanised steel, draught about 2 inches but is deeper than in the real world as I wanted a bit more stability. Like the real one a flat bottom with the only bit that has more than a simple curve is under the stern where the flat bottom rises to join the curved transom. the wheels however are over scales as I had the 4 frames near finished for the aborted schemes so instead of 4 inches at 1 inch scale mine are actually 5 3/4 inch diameter frames with the floats within that diameter. There dis not seem to be any point in wasting the fretted out frames even if they are a bit big but then I have increased the draught and most dimensions have been inspired guesswork, no to attempt to load a picture. When in the water the extra depth will not be seen and hopefully Monarch Minimus will not look too different from the real ship.
Working photo shows how small Monarch is, bulwarks not even knee high and the flat bottom, not so mucg draught as my version though.
Could not resist hanging a wheel frame on the side, hope I got the shaft at the correct height but that appears to be deck level.
Breathe enough fumes for today so an evening of rest.

Offline John S

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Re: Powered tin Bath?
« Reply #3 on: October 16, 2020, 06:21:22 AM »
No soldering today, too cold and wet to be outdoors but I managed to correct differences in the sheer lines. Flat bottoms are wonderful tor measuring  as they sit on a flat board so choosing the best looking curve I marked off at 100 mm stations and measured the height from the base marking the other side at each station. Using a wooden batten I checked the first side curve clamping it first in the middle then each end then cheap spring loaded clamps to pull the wood against the side  and that looked fine to me just a nice curve from bow to stern so transferred the batten to the other side lining up with the height marks then marking with a fibre tipped pen. Next using a sanding disc in the electric drill ground any high spots down to the line  which was made easier as I still had the batten clamped in place so easier for me to see and work to. Next the transom was evened out and finally the shaped sides at the bow. Turning the shell over I ground any pieces of metal sticking out from the seams back so now have a relatively smooth shell with a nicely curved sheer line that most importantly is even both sides so then time to come back indoors as it had started to rain.
Once back in the warm I placed the embryo engine and boiler in place but very soon realised I needed to raise the paddle shaft in order to fit the engine underneath but the 8 mm holes drilled in the sides can be raised 1/2 inch   and holes punched through for the shaft bearing housings and reinforcing plates. The plan is not for a cross shaft as is common but the engine coupled to separate paddle shafts with flanged couplings as in the real Monarch but this means the paddles need bearing housings long enough to stop them drooping and tied together across the shell. Bearings sourced are 8 mm ID rubber sealed ball bearings in stainless steel so should be both corrosion resistant and waterproof. There will be two each side at about 1 1/2 inch centres so with the reinforcing plates and cross beams I hope they will stay in line but that part comes in a few days once I have added some bulkheads and side ribs.
 Another thought is for the condenser and at present I am thinking of a 3 section keel condenser from 5/16 diameter tube each section being about 12 inches long and then I will need a hot well and reserve water tanks to fit in as I want to have a closed circuit feed water system so no oil  to contaminate the pond or hopefully salt water and keel condensers should not need circulating pumps only the engine driven air pump.
With luck Monarchus Minimus should be afloat middle next year when possibly travel restrictions have been lifted and we can get a bit socially closer than at present.


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