Trackless Locomotive

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.

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.

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.

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!

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.

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?

Mike

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.

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.

Rolly

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.

All files from this thread

File Name	File Size		Posted by	Date
20220312_093658.jpg	628.3 KB	open | download	zimirken	03/16/2022	Read message
20220315_074227.jpg	711.8 KB	open | download	zimirken	03/16/2022	Read message
20220330_095256.jpg	676.2 KB	open | download	zimirken	03/30/2022	Read message
DSC_0014.JPG	362.9 KB	open | download	Rolly	04/02/2022	Read message
My new Code boiler-2.jpg	35.3 KB	open | download	Rolly	04/02/2022	Read message
LED gauge.jpg	39.6 KB	open | download	Rolly	04/02/2022	Read message
water level gauge face.JPG	842.8 KB	open | download	Rolly	04/02/2022	Read message