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Trackless Locomotive

Posted by zimirken 
Trackless Locomotive
February 28, 2022 01:17PM
I'm back. Long story short, my toddler found a train game she likes to play, and after watching her play it, and then playing a realistic steam train simulator game myself, the old steam bug started biting again. I did a whole lot of tinkering and experimenting back several years ago, but I never really got a whole steam powerplant working.

I've gotten some upgrades too. I've gotten pretty good with my flux core welder, so my previous building method of janky pop riveted sheet metal can now be replaced by welded construction with big ugly welds. Also, I have a large HAAS TM3 CNC machine at work that's basically my personal toy. That should hopefully make the engine a piece of cake. It can do everything I could possibly need except maybe cylinder boring. I even have a small coal forge, in case I need to bend some metal. My biggest weakness now is time. I don't get much time to work in the barn nowadays, but most things that don't require welding and are small enough to be carried I can bring in to work and work on during lunch breaks.

My ambitions have been tempered to a much more realistic level. Specifically, I want to do whatever gets me to a steam powered vehicle that goes at least 0.1mph, within my budget and before I get bored and move on to something else. However, if things really don't turn out the way I want, I am willing to settle for building a smaller RC tug like thing that could possibly pull me in a wagon at a walking pace.

I do have some design goals though. I want it to look like a train. I believe the specific term is trackless locomotive. I think I'm going to use a riding mower chassis for the base. Maybe it could look kind of like this? Going in that direction, I would like it to be coal/charcoal fired, and ideally the engine would use the wheels as the crankshaft just like a locomotive. I want a max pressure of 100psi, as things get very expensive and hard to find above that.

Ideally, I would love to have a horizontal firetube boiler. But since I don't have $5,000 to buy one, or $2,000 in steel and $2,000 in tig welding and metal shaping machinery, I'm probably going to build a "fake" firetube by hiding a lamont boiler inside a barrel. Unless someone wants to donate a boiler of course.

I have some previous experience with building a lamont. Previously, I used an industrial air cylinder driven by a gear motor for the circulation pump and it worked quite well. I plan on using this same pump (rebuilt with a metal frame instead of a 3d printed frame, it was all melted when I pulled it off my old steam scooter). For the coils, things have gotten cheaper and easier to get. I'd like 4 or so square feet of surface area. Alternatively, I'm looking at something like this. It's prefabbed, finned, cheap enough, and ready to be hooked up. It's rated for the temperatures and pressures, and was built to do a similar task. For initial testing, I have a big propane banjo burner that would fit just right under it.

I took a quick look at my old steam scooter that's been sitting in the barn for a couple years. The tank is way too small! It's no wonder I had trouble getting a reliable water level reading. I want a bigger tank. That should give me more reliable water levels as well as a bigger steam reserve. I'm thinking about getting the tank off one of those 2 gallon air compressors.

Alternatively, I have a 6 gallon RV water heater that I want to examine the feasibility of using. I haven't torn into it yet, but I believe it's stainless steel. It's only rated for ~9000btu, so surface area would be quite low, but it's something to look at. At first glance this sounds absurd, but water heaters are fired pressure vessels subject to almost the same codes as boilers. Also, Mythbusters themselves used water heaters as boilers! In season 5, they tested the myth of a water heater rocket by removing all the safeties and just turning one on until it blew up. All the ones they tested failed above 200psi steam. THEN, a few episodes later, they used two electric 40 gallon water heaters as boilers to power a steam machine gun. They were running them in the 160psi range and they were walking around them up close with no blast shielding or anything. This was very interesting, especially considering that meant their insurance let them do that. I have no intention of deceiving myself about the safety. If it looks sketchy, I won't use it. However, it does bear investigation. I plan on taking it apart to closely examine it. Right now it's all covered in insulation.

As far as the engine goes, I'm not going to worry too much about it until I get a boiler working. The hardest part about that will be getting big chunks of steel for making larger parts on the CNC. I will likely try to use the same style of air cylinder that I used for my old 3d printed steam engine, or at least use the cylinder, piston, and rod. I want to try to keep things simple here. I'm thinking hackworth valvegear. I probably won't start with a wheel mounted engine, but we will see. It's much better to have a mediocre engine and work on making a better one than to get frustrated making a fancy one and not have any engine at all.
Re: Trackless Locomotive
March 12, 2022 01:12PM
Just finished rebuilding the circulation pump, with CNC machined aluminum parts instead of printed plastic. I'm using the cylinder and motor from the steam scooter. The cylinder bore is 20 or 25mm I think, and the stroke is 50mm. The motor is rated for 35rpm at 12v. The cylinder isn't rebuildable, but it it's bad, it's only like $15 for a new one. Conservative estimate is 0.016 liters per second if I use both sides of the cylinder. That works out to about 120 pounds per hour. I'm aiming for ~5sqft of tube surface and ~30-40 pounds of steam per hour so that gives about a 3:1 circulation rate at max fire.

Here's a quick video of it running.
Re: Trackless Locomotive
March 16, 2022 07:59AM
I finished my hand feed pump / hydro test pump. It's just an industrial air cylinder and some check valves.

I also attached another picture of the circulation pump.

I need to start working on the framework from the boiler, so I can figure out how big my chassis is going to be. I'm not sure if I should make the chassis out of steel or wood. I can always bolt steel brackets to a wood frame and weld bits on to the brackets.

Re: Trackless Locomotive
March 19, 2022 05:52PM
Interesting there. Over on the recirculating steam generator thread there is discussion going on . My brother and I are doing the math work slowly but steadily towards a larger system. We will be posting as we go so we can get useful critique on things. Once we are sure of the math we'll build and test. Your input would be appreciated if you have the time and interest. Hopefully we will get something reasonably good

By the way, great to see you back!
Re: Trackless Locomotive
March 30, 2022 10:52AM
I've got a preliminary gauge put together. I think I'm going to remake the plates that hold the rods, as the rods are way too close to the fittings. I just made adapters to hold the glass with o-rings that screw into 1/4npt, with some off the shelf needle valves. I can't recommend enough using a CNC to thread mill large diameter threads. Perfect threads with little to no effort even in tool steel.

The glass is 8mm x 12mm borosilicate, and cutting it was a bit of a nightmare. Several techniques just didn't seem to work because it was so thick and resistant to heat shock. Luckily I bought a pack of five tubes, so I have plenty to practice with. On the plus side the glass thickness makes it feel extremely sturdy.

Alternatively, I was testing an electrode water level sensor, and this style of LED indicators seem to work really well directly connected to the electrode using a 12v source with no amplification circuitry. In fact, they even seem to give a bit of an analog output, as their brightness changes depending on how much electrode surface area is submerged. I don't know how well I'd trust that though, given changing ambient light conditions outside.

Edited 1 time(s). Last edit at 03/30/2022 10:57AM by zimirken.

Re: Trackless Locomotive
March 30, 2022 03:03PM
Would it be better, with a glass tube gauge, to have a surrounding toughened glass casing in the old fashioned way to contain any bursts?

Re: Trackless Locomotive
March 31, 2022 12:27PM
I guess? Anything I've read is that those kinds of things are more to protect the glass from say, random coal shovel impacts. You don't really see fully encased gauge glasses very often. Normally it's designed in such a way that you can easily isolate it, and sometimes even replace the glass while under steam.
Re: Trackless Locomotive
April 02, 2022 07:14AM
For safety you should consider using commercial Gage valves. Penberthy, Ernst or others. They have built in check valves, if the glass lets go the check seats and no one will get burnt.
Over 150 PSI, I use Reflex gages flat glass. Above 300 PSI I use LED displays.


Re: Trackless Locomotive
April 20, 2022 08:13AM
The time has finally come for me to make a real steam engine. I've made several of various types and sizes before, but I've never really run any of them on live steam. I did a little bit of test running on steam with a solenoid valve engine I built several years ago, but there were drawbacks with the valves that made it not run very well, and it wasn't worth the effort to work around them at the time. I've put lots of hours into modeling steam engine parts, but I've always had trouble with decision paralysis, since there are a million different ways to make a steam engine.

Now that I've got access to a CNC, it's time. So far I've decided on a vertical engine using piston valves and viton X rings. I originally wanted to do a frame mounted locomotive style engine, but a vertical is easier to make separately and work on. The bore is 1.5in, stroke is about 46mm, and the piston valve is 13/16in diameter. Forgive my mixing of units, as I think and design in metric, but mostly have access to standard sized parts in America. I'm leaning towards the hackworth valvegear, since it's simple and it worked well on the very first steam engine I ever built. I'll be using ball bearings on everything, as oiling things does not appeal to me. Ball bearings are dirt cheap these days, so the only reasons not to use them are things like aesthetics or authenticity.

According to my calculations, this should give me approximately 250 watts of power with one cylinder, 60psi steam, and 70% cutoff at 500rpm. This design should also be easy to modify into a two cylinder engine as well. Of course these calculations don't take into account inefficiencies, but usually losses mostly increase steam usage, not so much reduce horsepower.

So I decided that the place to start was the cylinder and valve block. Those are the most demanding part of the engine, as they require the tightest tolerances, and are the part that are exposed to steam temperatures. Everything else can be mocked up using printed parts. It's pretty much all going to be aluminum, since that's what I have laying around. This should be fine since I'm using x rings. Now, the HAAS CNC at work is basically my personal toy, but the lathe in the machine shop is usually always busy. While it's easy to start the CNC and then go work on things, I'd have to use the lathe during my lunch break. So I'm trying to use the CNC and not the lathe as much as possible.
Machining video

So I started with the cylinder. I did the cylinder bore on the CNC by using a large carbide insert end mill and spiraling down the bore. I was expecting to have to finish it with a boring bar or on the lathe somehow, but it came out perfectly. I continue to be amazed by the capabilities of this machine, as the bore is very round, with no faceting that I can see, and it has a mirror finish. This is plenty good enough for running x rings, and better than I've seen inside industrial air cylinders. I may see if I can try to anodize it at a later time, as it is a bit on the soft side.

Since the cylinder block turned out so well, I did the valve block next. I made the valve passages small slots, which should work well with the x rings. The finish isn't quite as good on this, but it should be good enough for now. I can always make it better, if it wears out the x rings.

Now the piston valve. This seems like the perfect thing to make on the lathe, but that would be getting uncomfortably close to putting in actual effort, so I gave a go at cutting it on the CNC using a slitting saw. It turned out good enough for testing. I'll likely remake it later.

This is as far as I've gotten with the design so far. I wanted to make sure I could make the cylinder and valve block first. If I couldn't do that, the rest would just be a waste of time. Also, making them first means I can't change their design, so no choice paralysis.

This is how I feel now. I've been into steam engines since I was a child, but I've never really had the time, money, and tools at my disposal to make a real go of it until now.
Re: Trackless Locomotive
June 28, 2022 03:46PM
I've mostly posted my progress on other websites, and forgot to post anything here, so here's a short summary. Well, I built an engine. I ended up using the rv water heater for a boiler, and it worked well enough. Unfortunately, it was limited to 60-70psi. My little one cylinder engine just couldn't make enough torque to pull me around. So I rebuilt it into a two cylinder engine. The whole thing was machined on the CNC out of aluminum, with basically no lathe work. I even bored the piston and valve cylinders on the CNC via helical tool paths. The two cylinder engine works great. It's a piston valve engine with 1.5in bore and 1.8in stroke, using viton o rings for the pistons and x rings for the valves. It has a hackworth valve gear, and has ball bearings everywhere except the eccentric.

With the two cylinder engine, it's mostly self starting, and I was actually able to move under steam power... for a hundred feet or so before running out of steam.

The boiler works well for what it is. It has a steam blower, a sight glass, and all the fixings. However, it only has 1 square foot of surface area. After all, it's designed for 10k btu, not 60-100k btu. So my flue temperatures at over 700 degrees, and even with stainless steel turbulators/ radiators (which massively improved steaming) it just can't make steam faster than the engine can use it. So back to the drawing board.

Idle run of single cylinder engine.

Bench testing two cylinder engine.

Wheels up run of two cylinder engine.

It runs! But not for long.

So, on to the future. I'm thinking about trying to go back to forced circulation. I don't have a tig welder and I don't have umpteen million dollars to make a copper boiler or anything like that. Forced circulation is relatively easy to do with off the shelf components.

Okay, so I've got a tent stove I made out of a small propane tank last year, that has plenty of space for both a coal fire / propane burner and lots of heating coils. I should be able to fairly easily fit 3-5 square feet of tubing in here.

I was also dinking around on the CNC this week and I made a centrifugal pump that seems to work quite nicely! It should stand up to boiler pressure and temperature, as long as the motor doesn't overheat. I might have to put a small fan on it. Otherwise I still have my piston pump from the last boiler that's a proven success. I just figured a centrifugal pump would be simpler.

I'm sure it's FAR from an optimal design, but it makes good pressure when I plug the outlet with my finger with water in it. At 12 volts it draws about 6 amps when the outlet is blocked. However this is at atmospheric pressure and temperature with water. I'll try to test it this weekend by putting some copper coils in the exhaust stack of the water heater and seeing what happens. I have a good sense of how fast pressure builds when using an electric blower and when using the steam blower, so I'll notice a difference. Meanwhile, I cut the top off the tent stove, and will be trying to figure out a layout for heating coils. I'd like them all to be attached to the top through rods welded to the top, that way I can just pull the whole top off and all the coils come with it.

I also have to figure out a new reservoir tank. The water heater will work for now for testing as an unfired vessel especially since it's already plumbed with water gauge, pressure gauge, feed pump, and safety valve. But I'm looking at getting something like this later:
200 psi rated air tank

It's rated for 200psi, so I'll feel comfortable running it round 80-100 psi on steam. It's got lots of ports in all the right places, and it's cheap enough that it's not a big deal if it only lasts a few years.
Re: Trackless Locomotive
June 29, 2022 06:32AM
I'm not aware of any successful centrifugal pump at this scale. Another successful forced circulation system, piston pump, is Tony Grzyb's steam bike. My fear with a centrifugal pump is cavitation.

Please try this centrifugal pump and give us another data point. Whether it be success or failure, very good information.

I have a theory about piston pumps in that it sends a shock wave through the boiler. If tied to the engine rotation then it would be commensurate with the piston motion. I gave a presentation one year at the SACA Meet, I don't remember which one. I attached a couple of slides from that presentation for thought provoking ideas. It is like modulating to achieve higher net pressures to the engine.

One could modulate the burner in the same manor, commensurate with the engine. After reading the book about Tesla, I realized the potential of modulation.

I would like credit to go to the late Roger Ulsky on the data. He collected that pressure data one meet against my steam scooter engine. The data on my engine was a bust. However, he provided the data from his engine on the same file for me to play with. It is his data converted to PV diagrams real time. This lead me to this concept in modulation from the boiler via the pump.
open | download - Valve Simulation2.pdf (304.9 KB)
open | download - Valve Simulation2.1.pdf (151.6 KB)
open | download - Valve Simulation2.2.pdf (340.9 KB)
Re: Trackless Locomotive
June 29, 2022 11:02AM
As far as a centrifugal pump goes, I may have a couple of suggestions.

The most obvious is to inject your cooler feedwater right into the centrifugal pump suction. The cooler water should reduce the chance of flashing (cavitation) and the feed pump discharge pressure should improve the pump suction head. In recent years, it has also been found that shear is a problem with centrifugal pumps, especially those dealing with very hot liquids. It has also been found that fluidic shear can disrupt such a pump. One approach was to add tangential jets to the suction line in order to induce a spin in the direction of the rotor travel. If you are injecting the feedwater, perhaps introducing it so as to create a bit of a vortex will prove useful.


Re: Trackless Locomotive
June 29, 2022 03:22PM
I could see the intermittent nature of a piston pump helping to scrub steam bubbles off the walls of the tubing. I mostly made the centrifugal pump because I had the idea and the parts laying around, but I still want to test it. I have the piston pump I built earlier on this thread, I just need to get new check valves for it. That would probably be better as it's double acting, so I can set up two separate heating loops if i wanted.

I do remember visiting a ~35MW steam powerplant once during college, and their main feedwater pump was centrifugal. So I'm not surprised that it's more effective at larger scales.

I remembered that I have access to an oxy-acetylene torch at work, which means I can easily do silver soldering now. I did some silver soldering a few years ago on some boiler fittings, and it was rather tedious with just a propane torch. Also, silver solder seems to be much cheaper now and available in store. I cut the top off my little tent stove and took some measurements and sketched up some ideas.

It's 9in o.d., and ~8.5in i.d. at the weld seam. It's about 8in long from the grate up to the top where I cut it off. It's quite spacious in there.

I was thinking of lining the inside with 1/2in copper pipe soldered together in a zig zag to make a sort of "water wall". Using 6 inch long pieces and 1 regular and 1 street elbow, each vertical pipe is ~1.375in apart, which lets me fit about 16 around the circumfrence for about 1.5 square feet of heating surface. That's already halfway to my goal, at the cost of about $50 in copper pipe and elbows. Then, for the center, I'll probably make a pancake coil like I have previously.

I pulled this out of the last boiler I made a few years ago. The coil and the circulation pump worked perfectly, but there were other issues (like not having a viable path to an engine at the time) and I just lost interest.

I might try and reuse this coil, or make a new one. 20 feet of 1/4in tubing nets me about 1.3 square feet of surface area for like $12 in copper. 1/4in tubing is by far the best bang for my buck around here. Regardless of wether I use this coil, or make a new one, I'll be making a frame out of two steel plates with threaded rods welded on to mount the coils and the water wall.

If I use the piston pump, I could have two pump circuits, one for the pancake coil and one for the water wall.
Re: Trackless Locomotive
June 30, 2022 09:37AM
I know Rolly had a lot to do with making some centrifugal impellers for forced circulation. The casting can be seen at Tom's Shop at Berrien Springs. Perhaps Rolly can chime in...I don't know if there were any test results.

Centrifugal pumps seem to be less headache compared to piston pumps. From experience, check valves seam to be a high failure mode. I know many Stanley owners who use redundant checks both ball and flap. My engineering imagination would recommend a flap type of check with a centrifugal pump forced circulation type system. Ultimately, I would like to see a Tesla Fluid valve or diode used in this situation.

I'm pleased with your comment to try out your centrifugal pump. I also like Ken's idea to feed the colder water from the tank to the inlet of the pump.

After seeing some mono-tubes in action, it appears that there seams to be some oscillation regarding where the pressure is happening throughout the length of the mono-tube. The faster you can move the water through the generating tube, the more steam you'll produce. The smaller the diameter of generating tube, the more steam you produce. The ultimate diameter of tube is the 3/16" brake line (fastest model Hydroplane Boat).

The negative is that your water rate is hard to achieve for a larger engine than that of the high speed Hydroplane Model Boat. The pump pressure will exceed the output steam pressure just to circulate the water to generate the steam.

Note that your construction ideas look sound.
Re: Trackless Locomotive
June 30, 2022 10:58AM
Centrifugal pumps do not put out high pressure. Some can reach 50 PSI; it’s all in the housing design and motor power on the impeller and the impeller design.
Most heating plant boilers for general heating and air conditioning only run under 30 psi and most under that, can get away with centrifugal pumps for feed water and distribution.

The pump I designed was for circulation of the water in a forced circulation generator. The housing was designed to withstand 4000 psi as well as the bearing assembly. Pump pressure above boiler pressure was only 9-PSI hard thing to do.


Re: Trackless Locomotive
June 30, 2022 01:24PM
You should look at the White steam generator. Several years ago I had the opportunity to see two White generators apart and out of the cars.
I did cad drawings and made a scale model for my collection. I belong to model engineering club and build scale.

The White would fit nicely for your size and is a proven design. 3/8 copper tube would work just fine, just a little larger then my model.
See attached details.


Re: Trackless Locomotive
July 01, 2022 12:38PM
So I sketched up a quick model of what I'm planning on. It's all 1/4in steel tubing. My circulation pump uses a double acting cylinder, so I'll have two circuits: the water wall and the pancake coil. The water wall calculates out to being like 80 feet long with 2.6 square feet of surface area, but it's not going to be that long because I have to route the coils around the firebox door. Since it's a water wall, the surface area is effectively halved unless I space out the coils for airflow which I might do, that would also reduce the amount of tubing. The pancake coil is just under 50 feet for a total of about 1.7 square feet of surface area. Together this should put me somewhere between 3 and 5 square feet of surface area, which is right on target.

I'll have a steel plate on the top that has holes for threaded rods that all the tubing will be bound to, so that they are held in place against sagging, and I can lift the entire coil assembly up out of the firebox for servicing.

The water wall won't look exactly like this, as I need to make room for the firebox door. Also, I think I'll be spacing the coils out a bit to use more of the outer surface area. It will be held in shape by 6 sets of rods.

You can see how the pancake coil is arranged inside the top.

The yellow part is the top frame plate, with rods screwed or welded into it. The green part is a separate piece that is bolted to the plate. I'll make that out of a piece of 2.5in exhaust pipe, with welded rods to hold the pancake coil in place vertically. The rods coming off the top plate will hold the pancake coils in place horizontally.

Here you can see the two frame pieces by themselves.

This should give plenty of space for fire, and allow easy accessibility for repairs and modifications. It also won't cost an arm and a leg, as I can get 25 feet of 1/4in steel tubing for ~$15. Plus, since it's steel, I won't have to worry as much about it running dry if something happens to the circulation pump.
Re: Trackless Locomotive
July 01, 2022 12:51PM
I’ll say one thing for you, you do nice 3-D cad work.

I’d go with larger tube size like 5-16 or 3/8 and less space between the tubing. Slightly less then the tube diameter.

Re: Trackless Locomotive
July 01, 2022 03:18PM
Unfortunately for whatever reason fusion 360 does not have a proper helix tool, only this weird coil maker tool. That's fine though because it's just a visual representation of hand wrapped coils.

Looks like 3/8in steel tubing is pretty comparable as far as $/square foot goes, I already ordered 25 feet of 1/4in, but I can always use more tubing.

I found some reasonably priced 3/8in steel tubing, but it's got a thin PVF coating. I assume that will burn off on the first firing.
Amazon link

Using this stove as the fire box means I can burn anthracite coal, which is easy to get at TSC and supplies much more radiant heat than a propane fire. It's also more fun too.

I still need a steam vessel. I'll probably use the rv water heater initially, but there's no room left on my frame for the firebox, so it will probably just have to be stationary tests. Unless I remove the water tank, and replace it with a water tank on a trailer. So far my runs have been short enough that I never needed to add any water, since the tank holds 6 gallons. I don't know, we will see how things go.

It's a long weekend, but I won't be able to buy any more tubing until next week. I'll probably focus on making the framing, and winding the tubing I do have.
Re: Trackless Locomotive
July 05, 2022 11:53AM
I found 100 feet of 1/4in stainless steel tubing for $45! I think that settles my indecision on tube diameter. I only hope that I am able to bend and flare it. The only other big purchase that I can think of besides the tubing is the steam drum.

If I get a chance, I'd like to add a little sight glass to the output of the circulation coils. That would be useful to see what's coming out.
Re: Trackless Locomotive
July 05, 2022 03:23PM
I have made sight glass from tubing fittings, and used them up to 150 PSI. I think it was stretching it a bit. But they worked.


Re: Trackless Locomotive
July 06, 2022 07:02AM
So there's not much you can make for a boiler on a CNC. But I made a sight glass. Turns out the glass I have fits perfectly inside a 3/8 sch 40 pipe, and the couplers I have can fit 3 silicone o rings inside a little cavity between the two threaded end parts. I even managed to cut the glass the first time. The secret was to take a well dressed grinding wheel (not cutoff disc) and roll the tube against a corner of it. So now I have a little sight glass for viewing the output of the circulation coils. That should be very interesting, and I'll be sure to post a video of it.

I had an idea for the steam drum. I think I might try and get a nice piece of 4-8 inch diameter pipe, and machine end caps held on with tie rods. I've seen a few boilers made this way in my research. It's easy enough to use the CNC to carve a circular slot for the pipe to go inside of, and then seal it with silicone. I can put all the NPT threaded holes I want in the caps wherever I want. If you take a compression fitting and drill the center out so the tubing can go through it, you can route the tubing so that it opens up where ever you want inside the boiler. I did this with good success in my current boiler, as there wasn't any other way to have a steam takeoff at the very top of the tank. I would really like to have it horizontal for aesthetic reasons, but if it has to be vertical that's ok. This method also makes boiler cleaning a breeze, which is good because my water at home has enough iron in it to forge a sword from an evaporated kiddie pool. It's super easy to calculate the tie rods and stresses too.
Re: Trackless Locomotive
July 08, 2022 08:19AM
My tubing arrives today. Hopefully I can work on it this weekend. In the meantime I have the check valve array for the circulation pump set up.

Also, does anyone have any info on the watermann steam pump system? I thought about dinking around with my old pancake coil trying to make it a little monotube for something using that setup. I thought maybe instead of building a steam pump, I could mimic the action by having a thermocouple in the bottom of the separator trap that controls how fast an electric feed pump runs. I'd just have a needle valve in the bottom for a constant slow drain, and the higher the sensed temperature, the faster the feed pump runs. Maybe add a pressure sensor to more realistically mimic a physical steam powered pump?

I ordered like 4 1/8npt check valves from china for $7 on a whim, and when they arrive I'll see what they are made of. Probably only good for cold feed water, but you never know.

Bonus: found this on my suposedly blown down boiler that's been sitting in the barn for two years.

Re: Trackless Locomotive
July 08, 2022 08:41AM
If using 1/4" tube, I would think your concern would be the ability to push the water through the generating tube. Recommend to just push the water through the tube as fast as you can to generate steam. To make it variable with therm couple control is just adding an exercise in building complexity. Knowing a fellow mono-tube builder with successful results, he uses a therm couple and Adreno control to regulate the fire precisely. Perhaps make that your quest. His system is a once through mono-tube generator. It is based on the Richard Smith bike design. The same principle applies for a forced circulation system.

For shits and giggles...your trying to make your system adiabatic.

Nice bonus, must of been frozen on that check valve. I like your progress, thanks and looking forward to seeing your results.
Re: Trackless Locomotive
July 08, 2022 09:26AM
Oh no, this is just a regular lamont with the circulation pump running full speed all the time. I was just bored at work thinking about stuff. I've got that copper pancake coil stack and was thinking about testing out small monotube ideas with it at some point just to tinker with while I save up for the steam drum on the lamont.

The lamont is going to be coal fired. I'm going to have two flow circuits, one for the water wall and one for the pancake coils at the top. That should make the flow rate better. The pump is 25mm diameter with a 45mm stroke, and I think it spins at like 1-2 rps, so it pumps at least 21ccs of water per second ignoring the piston rod diameter on the return stroke. That's like 10 times as much water as my engine is supposed to use.
Re: Trackless Locomotive
July 10, 2022 08:19AM
Tom Kimmel has had great success with a mono-tube to a drum design. He used a device to control the water level to turn on and off the feed pump. I believe that one can reduce input pressure when the feed water is divided up to a two circuit design. However, care needs to be taken for ballancing flow or preventing tube burn-out.

With your experiments I think you'll learn that the feed control is difficult. I like your approach(s). Give it a try.

I attached a couple of designs for your consideration. Hope it gives ideas.

A quick note about my drawings. I might be considered old school. It relaxes me to draw with pencil and paper. It also helps with design verification in that I imagine actually coiling the tube when I draw it.

Re: Trackless Locomotive
July 11, 2022 12:25PM
Disaster! I didn't realize that the tubing I ordered had such thick walls. It's almost impossible to bend, impossible to flare, and the I.D. is too small to have good flow rate. What a waste of good tubing and $45.

Look at how thick that is! This stuff belongs in a science lab doing fischer toph synthesis or something. I might try to resell it or use it for structural purposes.

On the flip side, last week I ordered 25 feet of 1/4in steel brake line from Amazon, and they lost the package so I got a refund. Well it showed up on Friday. So I put it to good use. This stuff looks nice, it's even copper coated on the inside. I might order some more of it this week.

So, I hydro tested my old copper pancake stack, and it passed. So I worked on putting it into the top of the firebox. I pulled all the old wire off that was holding it together, and made a crude welding abomination out of sheet metal and 1/4in bolts and nuts. I like the way this went together, So I think I might make a new coil this way, but with a more precise CNC machined framework. I like being able to thread in all the framing rods that hold the coil's shape. That makes it come apart easily for repairs or cleaning or winding a new one. I don't remember how many square feet of surface area this coil stack has.

It's a little bit low on surface area, but if I need more I have space to add it. I started putting everything together and I realized that I never made any mounting holes in the frame of my circulation pump. I'll have to do that this week.
Re: Trackless Locomotive
July 12, 2022 09:04AM
Awesome news...you're definitely learning the ins and outs of building steam stuff. Keep trucking...
Re: Trackless Locomotive
July 13, 2022 05:35PM
Rolly, that White steam generator scale model is the coolest! Thanks for sharing it. smiling smiley
Re: Trackless Locomotive
July 18, 2022 10:42AM
Well, I plumbed everything up and tried to do an atmospheric steam test. The circulation is working great in the video, and the stack temperature is pretty low too. It's really neat to see the sight glass on the output of the coils.

Video here!

Unfortunately right after I took the video the circuit breaker popped (unrelated), and in the time it took for me to go reset it and come back, my blower got too hot and died. I later tried to do a test using a propane turkey fryer burner. That seemed to work really well, but I didn't have enough time to do any sort of accurate study. Besides, without any insulation on anything I'm losing a TON of heat to the air instead of keeping it to make steam. Plus, that big pot has a lot of surface area to lose heat to as well, further reducing the accuracy of my test.

Next step is to put some fiberglass on things and try to do a more accurate test. I'll try to see how fast it takes to boil a gallon of water. There's not much else I can do with it while I work on getting a steam drum put together. I'm thinking 6in sch 40 steel pipe, with 1/2in steel plate caps, held together with tie rods. I can CNC little slots in the caps for the pipe ends to rest in, and seal it with a bead of silicone.
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