Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

Hi all. I’m am new here so I’m going to be asking questions

So I’m just getting started on a boiler build. I’ve looked at YouTube builds and having worked on pressure vestiges including repair of big tank trucks I have great respect for pressure tanks. I’ve seen some disastrous explosions but none  with steam . An exploding steam boiler would be no fun at all. Some of the YouTube ones there is no way I’d pressurize.

So I’ve laid out a build. I’ll take pictures as I get to making chips. Initially I started out thinking I’d use bar stock aluminum. Bore it to size then make a screw-in end cap. Well my old design for mfg. training kicked in. I looked up the price of 4” diameter aluminum bar and about fell off the chair. Aluminum has about doubled in cost over the last year. We’ll fortune stopped by and my son received a number of aluminum drive shafts. Some as big as 6” of. So I selected a 4” of piece it’s got 1/4” wall thickness.   I thought the end caps should be at least that too . Now I’ve TIG WELDED MATERIAL like this but with my poor eyesight it’s probably not a good idea. Besides we didn’t have any flat stock . I thought it might look cool if I machined a dome cap but even that means a thick piece to start with. I could cut threads bot internal and external so a screwed in cap would work but it’s still a lot of work, next I thought we’ll I have to get so pretty thick stuff any way so I thought possibly insert with Teflon o rings then bolt or use button head screws both around the of ant in from the end. It’s a lot of drilling and tapping and mating holes but just time consuming. So I sat down and did a couple pages of calculations and #6 or #8 screws will work and in stainless will give a try steam boiler look . Teflon o rings don’t stretch well so a flat dis equating to the groove required then a retaining flat plate screws on with the same button head screws wil fork. The hole will not go all the way through. My engine I’m about to purchase uses this method so I’d say it’s proven.   Teflon o rings are about $10 each . 
So here is a question , what is the bundle of internal tubes called. A very long time ago there was a boiler buil in a model magazine and they were called super het tubes then we call them pass tubes in the auto worldvrelated to radiators  initially I thought small maybe 1/4 inch but I think 1/2” will be easier . Copper tube was less expensive so I have a coil coming . I can cut and straighten with out an issue. I then thought Teflon discs would be nice for holding these until I saw the cost of Teflon round or flat stock. It’s worse than aluminum or copper.  Since I have enough aluminum bar it will be an easy lathe job to just cut off discs face then drill on the rotary table or coordinate measur bolt hole circle set up will be easy I can cut some 1/2” I’d stock for spacers to space the discs. Next was a heater. I wanted a simple 110 plug in heater. It took a little searching bu I found a heater with 1/2” npt threads so I think just tapping a hole in the end cap and putting a hole through the support discs for the element would be simple. Next is fittings. Since most model steam stuff is metric and I find 1/4” 20 TOI ME  to be pretty common size  so far I haven’t found a tap and die set I’m comfortable with . Many descriptions lead me to believe I’ll be getting US inch threads. Now I’d like to tap a row of 1/8” or 1/4” npt threads for gages but again some have metric some have US threads. I’d like small gages as automotive gages are 2-1/16 dis and I think will be ugly unless in a panel the little enging is only about 5” x5”  so I’d like to not have a massive gage station there are some cool electronic things but again the price is way more than double my airliner dash I had in my street rod. So this is up in the air. I can modify standard brass pipe plugs but it starts getting messy looking  there will be pressure temp output , fill and drain plugs so lots of drilling and tapping  I found AN braided Teflon hose for boiler to engine line and even the exhaust lines. I have two turbines ordered that I’ll probably send exhaust into for oil separation as they can spin 50k rpm pretty easy.
I forgot the boiler will be mounted on two half circle mounts pretty standard then wrapped with auto exhaust insulation and it will have a polished stainless over lay shield I’m als thinking I can roll a piece of polished sheet to put inside as a heat reflective barriers think it might help heating faster and maintaining heat better as stainless I’d terrible for heat transfer. Plus’s ther will be plenty left over from the decorative outside piece  I have an idea for a neat mounting board simulating the old textile mill floors. They were highly polished as textiles are very dusty products so smooth floors made cleaning easier.  That’s down the rod.

I know this is wordy so bear with me I’ll get a picture
I’ll have more info later as soon as I order the engine. I just received email from chilertern and their new electric boiler is not big enough for the 4 cylinder mill engine I want. They recommended almost the same size as I have planned or air compressor. I’ll have picture   story later.

Byron

Summary.

I need metric tap and die set but not all sizes just steam stuff.

Your volume is almost exactly what I had calculated too. The smaller 1 gallon ultra quiet air compressor might not be enough to run at sustained rpm I was planning about 1,000 cruising speed and 35,00-4,000 top speed with the exhaust tuning to the turbines they don’t take much at all until loaded. I haven’t even figured that out yet it’s going to take a pretty fancy gear box to gear 50k down to a usable value. I’m in the middle of a staged planetary unit. I found that rod or bar stock pinion is available so that part is not bad ring gears are expensive and not common I could probably do an external gear just the opposite of internal but my design will need major changes. That’s what happens when you get locked into a thought there are even a couple model gear boxes around but I’m going to support USA economy and stay here. Politics aside. Brass gears are going ballistic now maybe I can get something 3D printed.  The turbines have only a 5/64 shaft so I don’t think that will last long there is a shaft calculation that rail roads used to analyze analyze  axels. I don’t have my Roarks book here so maybe I can find it on the internet. I’m planning on replacing the shafts anyway as it’s hard to find couplers that small.

Regarding corps ion, being ex boater I’m well aware of corps ion I did plan on a zinc anode there are all kinds of boat ones the local marine store has lots of them. The end caps will be easily removable so cleaning the boiler will be a regular item. Copper and aluminum don’t work too well together there was a lot of bronze on my cruise. The props and rudders primarily. It was easy to clean them before spring  splash in. I just hit them with the small angle grinder and wire brush. The rudders had zincs so they were easy to remove and clean there were zincs in the bilges too although there wasn’t much to corpse ther the pumps were mostly plastics there were a couple in the engine room around the engines but much of the engine stuff was bronze even the oil coolers there were lots of ground wires anything aluminum was grounded with wires to the engine even cylinder heads and intake manifolds were grounded . The exhausts were subject to rust and corrosion and a real problem if they got bad. Mine were very good but my neighbor had his rust out really bad there may have been zincs in the mufflers too but I never had issues with mine seems like there was a ground wire there too as there was a rubber flex hose between the manifolds and mufflers.  Thy aren’t a primary concern now anyway.  I’m glad I’m out of the boat. They are a constant source of expensive maintenance  both motors had water separator as did the generator. It seemed like I had to change all of them every time we went out . You never want to be dead in the water on the Missippi river with the tugs and barges they don’t like having to get out of erratic boaters.
Byron