Does anyone know the design of this boiler?
|Mark Knight 4||05/07/2020 08:33:03|
|21 forum posts|
A few years ago I inherited this 95% complete steam tug from my father who built it between 2005 and 2008. It is a work of art and engineering. I’ve never found the drawings but I know it is a Mobile Marine Models Lady Jan hull with a Borderer piston valve steam engine made from Reeves castings. Does anyone know who’s design of boiler this is?
I’ve got the engine and boiler out and working well on compressed air. The coupling to the prop shaft needs attention because the shaft and engine are not aligned so is very noisy.
The boat has a water pump which is geared to the engine. The engine exhaust steam is piped through the water tank but this just pressurises it and blows the lid off. Is this normal practice with a steam plant to recover some of the exhaust water? Also the pump has no control, how do I guarantee it delivers the correct amount of water to the boiler? I’m tempted to disable the pump and just run the boat for a limited time with the water in the boiler.
|Bob Abell||05/07/2020 09:24:30|
9337 forum posts
Be very careful......Steam engines are quite dangerous in the wrong hands!
The most important item is the Boiler. It must be pressure tested by a competent recognised third party and a Certificate issued
Some Council owned ponds do not allow them, on the grounds of public safety
Your Father has built a very nice model there
You definitely need a close knowledgeable friend to keep his eye on things
|Ray Wood 2||05/07/2020 09:38:37|
2789 forum posts
Your father certainly knew his stuff, what a lovely legacy to have
The centre flue boiler is a Martin Evans design published by SARIK, which comes in various sizes from 4" > 2" diameter, I think you may the 3" version which I also built about 25 years ago, a very robust sound design.
Lots of rules and regs these days about needing a current test certificate for the boiler which some model boat clubs have tester, certainly model engineering clubs do. But if you have a private lake in your garden happy days !!
The most important part of the steam plant is the displacement lubricator which is in the steam feed from the boiler to the engine which needs to be filled with steam oil before the run and the condensed water drained from it after the run, the steam condenses in the lubricator and forces the oil up and into the steam pipe.
The water feed pump should have a bypass valve to allow the excess water to be returned to the water tank, this prevents the boiler being filled with too much water, the rate of feed is a matter of trial & error.
The exhaust steam does appear to be going back into the tank, many folk wouldn't bother and put the exhaust straight up the funnel.
Hope this helps, a gas cut of valve for the burner is a good safety precaution if your going to use radio control, if it gets stuck in the middle of the lake to prevent it boiling dry, because the blow lamp is hot enough to melt the boiler joints!!
Regards Ray (Bob beat me to reply)
Edited By Ray Wood 2 on 05/07/2020 09:39:31
|Roger Clark||05/07/2020 10:51:13|
257 forum posts
Hi Mark, Lovely boat, you should be proud of your dad . Like Bob and Ray said you absolutely must join a club, make sure they have a boiler tester, commercial testers will cost you much money, and being in a club will benefit you with knowledge, experience and third party insurance which you must have if you float your boat anywhere that the public has access to.
If you give your location there may be some who can advise on a suitable club, not all model boat clubs have boiler inspectors but model engineering clubs generally do and some have a boating fraternity as well.
I would be surprised if a condenser tank wasn't on board, they are used to extract the steam oil before the steam goes up the chimney and into the environment, some clubs require this. In saying this the pipework looks quite complex and your dad would not be returning exhaust steam back into a water tank as you wouldn't want oil going into the boiler. Needs further investigation.
Edited By Roger Clark on 05/07/2020 11:00:28
|Mark Knight 4||05/07/2020 22:15:53|
|21 forum posts|
Thanks very much for the replies. I’ve had a look at the Sarik website and they quote 2 boiler sizes, 4” diameter by 11.5” long and 3” diameter by 9” long. Mine measures 4” diameter by 8.5” long so perhaps my Dad customised the length to fit within the space he had available.
I live near Derby so if anyone knows of a nearby club that could help with a pressure test and safety certificate it would be a help. I’m not a complete novice when it comes to model engineering (or full size for that matter). I grew up making steam engines in my Dad’s and Grandad’s workshops and have now inherited the contents of those workshops. I’m also a design engineer by profession with over 30 years working as an aero engine design contractor. The current pandemic has resulted in me having far more time on my hands hence why I’ve turned my attention to this boat which has just been gathering cobwebs for the last 12 years.
With regards to a pressure test, I don’t have access to a hydraulic pressure tester but I air pressure tested it to 100 psi. The boiler was placed in the middle of the paddock so in the very unlikely scenario that it did suffer a catastrophic failure no damage would be done. It passed with no leaks after 30 minutes. This was carried out to put my mind at ease for when I ran the boiler at up to 60 psi on both air and steam. The safety valve didn’t blow at 60 psi and the pressure gauge runs up to 100 psi. Does anyone know what the recommended working pressure is for a Borderer engine running with this boiler? The engine runs sweetly down to only 10 psi before friction dominates.
With regards to the water pump, how would a bypass valve be controlled because the water pump exit pressure would surely only be similar to boiler pressure until the boiler was full of water by which time it would be too late.
Presumably a gas shut off valve would require another radio control channel or is there a passive method for doing this?
|Mark Knight 4||06/07/2020 08:47:46|
|21 forum posts|
Edited By Mark Knight 4 on 06/07/2020 08:50:09
|Bob Abell||06/07/2020 09:35:22|
9337 forum posts
Very nice video, Mark
You are half way there, already!
Will the engine start, after stopping in any position?
This is essential with RC control
|Mark Knight 4||06/07/2020 10:02:03|
|21 forum posts|
Hi Bob, yes at 50 psi the engine self starts in both direction from any position. However below about 30 psi it sometimes sticks and won’t self start. I’d like to improve this because once turning it runs down to only 10 psi without problem. The engine is slightly tight when one of the pistons is at TDC. I’ll probably dismantle the engine in order to investigate. When running on compressed air, I’ve put a few drops of machine oil down the steam delivery pipe and also lubricated all the external moving parts so it isn’t a lack of lubrication.
Edited By Mark Knight 4 on 06/07/2020 10:02:50
|Ray Wood 2||06/07/2020 10:58:21|
2789 forum posts
You obviously have a good grasp of what's going on with the engine, the boiler feed pump will fill the boiler with water against the steam pressure with no problem, the bypass valve just reduces the pressure of the water being pumped in and normally returns it to the storage tank. this prevents the boiler from being completely filled leaving no room for the steam to gather at the top, I forgot to advise you but you may know the water level must be maintained at a level above the centre flue tube, it's worth making a note of this level on the gauge glass.
Regarding the safety valve setting if it's a loco type valve it will be adjustable to blow at say 10lbs above your working pressure say 60 lbs.
During a boiler hydraulic water test it will also be good practice to test your pressure gauge to see if it's reading correctly with a bigger gauge.
I'm hoping the Model Boats Steam Guru Richard Simpson can let you know about clubs in your area?? I'm in Kent.
|Mark Knight 4||07/07/2020 08:28:28|
|21 forum posts|
I’ve now sorted the engine, it starts from any position in both directions at only 10 psi. The problem was the axial setting of one of the valve eccentrics on the crankshaft. It was causing the valve con rod to cross bind With the eccentric when it was at TDC. Once I’d slid the eccentric along the crank to align it with the piston valve the engine runs like a Swiss watch as shown in the new video above. The No 1 cylinder big end bearing has a slight knock so I’ll investigate that further and if shown to have too much clearance, remanufacture it.
Thanks for the advice Ray. I’m still not clear how the water feed bypass valve would work. Is it a valve within a branch pipe between the feed pipe and water tank that would require its opening adjusting by trial and error in order to keep a constant water level or is it a valve that opens at a certain pressure like a safety valve? If it’s the former, I would think the opening to keep a constant level would vary for different boiler pressures and engine power (throttle opening). I don’t think the latter would work because the boiler could still fill at a low enough pressure that wouldn’t open a pressure operated valve.
The water level glass tube is wholly above the flue. I guess it was designed like this so that if the level is anywhere in the glass it’s ok.
I’ve compared the pressure reading on the small Reeves gauge on the boiler with the gauge on my air compressor and both read within 2 psi so no problem there.
Next job is to remount the engine in the boat to accurately align it with the prop-shaft and hopefully stop the coupling from knocking.
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