Model Boat Mayhem

The Shipyard ( Dry Dock ): Builds & Questions => Steam R&D: => Topic started by: hammer on February 27, 2018, 12:00:04 pm

Title: My 7th boiler.
Post by: hammer on February 27, 2018, 12:00:04 pm
I am building this boiler for Totnes Castle show in working vessels above. But I will post here as well as steam fans may not have see it. My first attempt was a wedge type, this was successful, But due to lack of running knowledge, running engine on the bench, it ran out of steam. I now know less steam is used under load. Would have been fine in model. However I had built No2, horizontal 3"+6" fire tube. No 3&4, 2"+4" verticals for the grandsons. No 5+6, twin tube horizontals 2.5"+8". Why 2 I built one with 22mm fire tubes couldn't burn all the gas in the tube could light the top of the funnel. Not good in a boat. more later.
Title: Re: My 7th boiler.
Post by: hammer on February 28, 2018, 10:22:18 am
Sorry post interrupted yesterday.  I made two regulators for the 22mm fire tube but still gas would burn outside the funnel.
Now No7 I was lucky to see a 103 +300mm 16g copper pipe on ebay only 9.99. free P&P. Can't be true but what's a loss of 9.99. What a surprise a BS mark steamline perfect condition.  Just managed to score for the cut in the lathe, by placing over the chuck & pulling the jaws out. Then cut with hack saw, gentle clean up in lathe by moving the wooden plug. Cut the remainder down the middle annealed & flattened. Turned the wooden plug down 2 thickness of the copper as a former. Cut plates on band saw  annealed  again & started to form. Annealed again then in the citric acid for another go top day. The fire tube brazed up pipe fitting as seen. Two fins on out side near to burner to compensate for less cross tubes than normal. Cross tubes silver soldered in after. Any comments good or bad welcome.
Title: Re: My 7th boiler.
Post by: rhavrane on February 28, 2018, 06:29:10 pm
Bonjour Hammer,
I am a collector, not a builder so please forgive in advance these remarks based on my experience.
I am quite surprized by the 180 angle you give to your central fire tube. To my opinion, it will block the torch flow. Even with a little angle at the chemny level, I already have heat flow probems
Sometimes, the fire goes back in the torch : at 3'50"
I have a tool to check my burners... My nose :-))  and when it stings, I know the combustion is not complete.
To have more water pipes on one of my latest acquisitions, I have asked my manufacturer to lengthen the fire tube to let a maximum of water pipes in the boiler and the  the dart of the torch at 5 cm of the first one :
Title: Re: My 7th boiler.
Post by: hammer on February 28, 2018, 08:37:26 pm
Thanks for your comments Rhavrane. After I had brazed the sharp angle I did try the burner before completing the other joints. I must try again now the cross tubes are fixed. Especially in view fo you comments, l will do tomorrow. 
Title: Re: My 7th boiler.
Post by: rhavrane on February 28, 2018, 08:56:39 pm
Bonjour Hammer,
It is my pleasure to share my experiences, and of course, it is just one opinion, and furthemor the one of a collector. I would also strongly suggest you to make your test with a chemney and possibly in an environment representing a hull, the breathing of the burner is very dependent on its environment.
One of my latest bad experience is a fire in my last boat, probably due to a lack of air around the burner and a bad flow of the fire in the torch:   <:(
Title: Re: My 7th boiler.
Post by: steamboatmodel on March 01, 2018, 02:13:54 am

I see no reason why you would have problems with that flue design. Full size boilers use return tubes all the time, You may not have flame all the way around the bend, but you will have hot air which will transfer its heat to the boiler. You may even have to install turbulators to slow the flow down.
Title: Re: My 7th boiler.
Post by: hammer on March 01, 2018, 10:09:02 am
Thanks Gerald. As posted above I did a test with the tube dry before going a head. Hopefully the cross tubes will act as tabulators.
YES rhavrane, I will have the companion way fore & aft open there is also a hatch to the boiler room that can be left open. Thanks for the warning.
Title: Re: My 7th boiler.
Post by: hammer on March 01, 2018, 10:33:43 am
Cut down the length of the remainder of the tube, annealed flattened, cut into two circles, 9mm larger than boiler tube. The wooden plug used on lathe when scoring, was reduced by twice thickness of copper +.  A bolt fitted in the centre, this will be former for end plates. I know it should be steel, but I don't have any. I have used ply for this before with no problems. Annealed plates again, started the flange. Annealed again now in the citric acid, for next time, slowly, slowly catch monkey.
Title: Re: My 7th boiler.
Post by: hammer on March 03, 2018, 10:16:32 am
View of my hearth from building insulation blocks. Have lots of smaller pieces to pack around if wanted.
A trick to speed up the flanging, a jubilee clip stops the last hit from moving out at the next hit. tap around the clip tighten & repeat only twice, then anneal.
The burner I use for fire tube boilers. Jet needs to be 2.25inch min from gauze.
Title: Re: My 7th boiler.
Post by: derekwarner on March 03, 2018, 04:49:08 pm
Still here RGY..... %)

1. is the boiler burner body constructed from a 65x50 copper concentric type/style reducer?.......
2. is the boiler burner mesh stainless steel?
3. did you scrounge the wire mesh for the burner from a miniature chook house  {-)

Title: Re: My 7th boiler.
Post by: rhavrane on March 03, 2018, 06:24:39 pm
Bonjour Hammer,
If I see correctly your burner, you have melted stainless steell and copper. Based on my experience shared with other builders, it is never good to mix ferrous metal such as stainless steel and non-ferrous like copper or brass, this always generates an electrolytic reaction in aqueous environment, even at level burner, and therefore risk of fouling and / or breakage.
This is what happened to one of my combined gas attenuato/regulator :
Title: Re: My 7th boiler.
Post by: hammer on March 04, 2018, 10:01:18 am
Derek the fitting is a 28mm 22mm reducer.  To answer both post the mesh is brass from an old milk strainer. No it doesn't melt. The fittings & pipe in the fire tube are for refrigeration thicker than domestic. At my pressures 25psi and this diameter domestic would be ok. according to my calculations.  thanks both.
Title: Re: My 7th boiler.
Post by: hammer on March 05, 2018, 10:06:34 am
The problem with using wood as a former if fitted tight the copper can dig in. this can make it very difficult to remove. To overcome this I clamp between two bits of wood. In the vice upside down a small equal gap can be seen. I had skimmed a fraction off the former for this. The end caps in place. a patch brazed over the centre hole. Three holes to drill in burner plate two for sight gauge, one for steam out. I also need to fiddle with the fire tube chimney. lower the burner end & make the chimney vertical. 
Title: Re: My 7th boiler.
Post by: pendlesteam on March 06, 2018, 07:30:49 pm
If I may add a little information to assist you with your build - If you have flame coming out the chimney it is the design of the burner which is at fault and has nothing to do with the flue. There is a lot of research and development behind a burner which works well - or extreme  good luck! A well designed propane/butane burner doesnt need a chimney to operate successfully, but it does work better with one. The flame front on a metal burner should burn away from the gauze/plate, this keeps the burner and gauze from getting too hot. If the flame front is too close the metal gets too hot and the flame moves from outside the burner to inside the burner. It is then only a short time before you need a new burner.
Title: Re: My 7th boiler.
Post by: hammer on March 07, 2018, 09:46:16 am
Thank you for that advice, from some one with knowledge. Much appreciated. The burners have preformed well in all my boilers in which they are used. Just that in the 22mm tube not all the gas was burnt in side. Only a very small blue flame appears above the funnel. I didn't realise this was happening until on bench test I happened to pass my lighter a cross the top. The problem could have been solved with a number 3 jet, in my opinion. But couldn't get them anywhere. With a 28mm tube no problems at all.
     A photo of the two boilers the 22mm still in its jacket. The reason for the double tubes. My son a refrigeration engineer gave me 2.5" pipe. Had a light bulb moment a low centre of gravity, just what is needed in a very tender paddle steamer.   
Title: Re: My 7th boiler.
Post by: hammer on March 07, 2018, 10:17:48 am
Pictures of my other boilers. A conventional horizontal 3", one of the two 2" vertical and the wedge type, with side of jacket removed.  The wedge was an attempt to obtain a low centre of gravity again. 
Title: Re: My 7th boiler.
Post by: hammer on March 08, 2018, 10:21:05 am
Pendlesteam. I have seen one of your burners, just below this post. Our burners a very much alike, the big  difference (apart from the metal) my jet tube passes right across inside the main. Maintaining the length but saving space. Necessary with the twin flues so close. Once again thanks for the interest.
Title: Re: My 7th boiler.
Post by: hammer on March 23, 2018, 10:16:07 am
Testing the fire tube for any leaks. I don't want to make plugs & a valve. So I use 2 balloons, blow them up tie with string. Use a slip knot well up the neck. Fit over ends pull slip knot, place under water & squeeze both balloons. A good pressure is obtained, good enough for a 25lb boiler. No air bubbles so safe to solder in. Photo poor sorry. 
Title: Re: My 7th boiler.
Post by: hammer on April 10, 2018, 10:27:32 am
  tested at 60 psi  safety valve set at 25 psi. etching primer & high heat black spray paint. Taped on a dowel for easy handling, this also masked the burner connection. lagging wood cut enough for 13ins.   
Title: Re: My 7th boiler.
Post by: hammer on April 15, 2018, 09:39:49 pm
You will notice there are no stays fitted' this was intentional. At 25psi there is still a large flat area at the back of the boiler. this did bulge slightly when I tested it to 60psi. I tapped it back flat, when tested to 50 psi buy the inspector it did not distort at all. On the complete boiler the stays are part of the insulation. The face of boiler is covered by a stainless steel plate. this covers a old soldering pad. The back of boiler is covered with 3ply, the rest mahogany strips. The stays hold it all together notice they are long enough to pass through the bulkhead holding the boiler in place.   
Title: Re: My 7th boiler.
Post by: hammer on April 17, 2018, 10:09:48 am
Almost finished just clean up & fit brass straps. All fittings made have to buy a pressure gauge. So no more post back in Totnes Castle blog from now on.
Title: Re: My 7th boiler.
Post by: KNO3 on November 04, 2018, 11:14:56 am
I really like your return-flue design. It should be more efficient than the average short straight flue seen in most model boilers of this type.

If you didnt add stays, why didn't you make the boiler ends domed? That adds great strength to them and they won't bulge.
Title: Re: My 7th boiler.
Post by: hammer on November 04, 2018, 05:43:43 pm
KNO3, I am R.G.Y so I think we know each other from Paddleduck days. The reason for the short flatended design, was I intended to keep all the machinery in the scale engine room. I intend to fit out the saloons to scale. The boat can be seen look for Totnes Castle in Woking boats. You will notice the bolts on the out side, these are the stays. Holding the back to the bulkhead & the stainless steel plate on the front. This has proved adequate as working pressure is only 25psl .
Title: Re: My 7th boiler.
Post by: KNO3 on November 04, 2018, 09:27:53 pm
Yes we do! 🙂
Title: Re: My 7th boiler.
Post by: hammer on November 04, 2018, 09:51:52 pm
Good to hear from you.