Trackless Locomotive Build

[rolphill]

This is a continuation from my boiler build thread here.

My boiler is to the point where I need to start mounting it and the steam engine together so I can pipe them up. I was originally planning on putting them in a little rowboat. However, I knew in the back of my mind that I'd almost never have a chance to actually take that out on the water. However, something that can putt around the yard can be played with much more easily. So, I started my build by stripping my old steam kart down to the frame. I thought about making a new frame, but reusing the old one adds some character and removes some decision paralysis at the same time.

One of the major improvements I'm doing is to use real wheels instead of harbor freight wheels. The harbor freight wheels had way too much drag between the cheap bearings and the wide tires in grass. This is a significant loss since I only have half a horsepower or so to work with. So I started with the wheels by getting some kids bicycle wheels. My daughter recently got a bigger bicycle, but didn't want to get rid of her old one. She was very happy that I am keeping the 12in wheels off her old bike to use for the front wheels. For the rear wheels I just bought an old kids bike off marketplace for the princely sum of $5.

Bicycles are great sources for parts because people give them away all the time for next to nothing. However, bicycle wheels have a major disadvantage. The axles are designed to be held on both sides, and are very small diameter. So I took the wheels apart, and machined new hubs to accept 5/8in axles. The front wheels have nice bearings so they roll with little resistance. The rear wheels are 18in and are locked to the axle. Rather than use a keyway, I ended up welding a pinch collar to the hubs to grip the axle. This has worked well for me in the past. The new hubs are also a little bit wider than the old ones to increase lateral strength. I then ordered new spokes to fit the new hubs and re-laced the wheels. I didn't really do any truing since they are small wheels for a relatively lower speed application. The 18in rear wheels are also extremely solid and beefy now because I could only find a pack of 4mm motorcycle spokes in the right length. For whatever reason I haven't taken any pictures of the rear wheels yet. oops.


While waiting on parts for the wheels, I made the front axles. These are machined and welded up from pieces of 1in rod. They are pretty self explanatory.


I also wanted to upgrade the steering. I had this old printed steering wheel that was part of a gaming wheel setup for playing driving games. I took the steering wheel and machined a matching gear and mounting bracket. The gear modulus is big so I could cut out the gear using a 1/8in end mill instead of having to try to use gear cutters. It's about a 1:3 reduction, and the large gear pinches fingers super easily. This steering setup should work quite well. I may have to reprint the wheel in something like petg for higher temperature resistance in the future. This was actually the first gear I've machined on the CNC. I'm surprised it took this long.


I've got the front wheel assembly all put together. I won't install the steering wheel and linkage yet until I put the boiler on so I know where to place and route it.



The next step is the rear axle. I don't have a picture of the whole frame at the moment, but the arrangement will be: rear - seat - boiler - engine - front. The engine will be connected to the rear axle using bicycle chain, with two sets of 10:30 sprockets. I also want to add a second gear at some point.

The seat has an open box area underneath it for coal storage. I was actually thinking of building a tender to hold the water and things like tools, more coal, battery?, and stuff. That would keep weight and length down on the vehicle, so it's more portable. I might add like a 1gallon water tank to the main vehicle.

 

[rolphill]

It's coming together. All the wheels are on, and the boiler is on.



There's more space on either side of the boiler than I was expecting, which is good. That means It'll be easy to route the steering linkage on the right side, and the drive chains around the left side. However I had to remove the hand pump, as it was right where my legs are going to go. I'm not quite sure where to put that yet. If need be I'll just go without it and add an electric water pump.

I'm a little concerned about the diameter of the rear axle. It's 5/8in, which is smaller than an average go kart live rear axle. However I probably won't be hitting go kart speeds so it will hopefully be fine. If not, I can always enlarge the hubs to 3/4in. I also have to get a new tire for the other rear wheel next week.

I think I'll try to lower the seat a bit. Currently I have to hunch down to see into the firebox, and see the pressure gauge. I can move the pressure gauge, but not the firebox door. On the subject of ergonomics, I'll also want to add a deflector for the relief valves, so they don't blast me or my leg.

The next step is mounting the engine, and then finally plumbing it to the boiler. Oh and installing the footrests.

 

[The Ignoble Troll]

What a cool crazy looking contraption!

 

[rob smith]

A boiler between the legs creates a bit of "excitement" "tension"

 

[The Ignoble Troll]

Jju

A boiler between the legs creates a bit of "excitement" "tension

Just wear a sports cup, what more protection does a guy need?

But seriously, really cool Frankenstein build and awesome idea to just re-spoke those tyres!

 

[rolphill]

Jju

Just wear a sports cup, what more protection does a guy need?

But seriously, really cool Frankenstein build and awesome idea to just re-spoke those tyres!

Having access to a CNC and a bunch of scrap metal, but very little money or free time at home really flips what's "easy to make" and what "should be bought instead" upside down. Although if I had a reasonable metal lathe at home and time instead I'd probably still do the wheels the same way. It seems like an easy and cheap way to get good quality low resistance wheels. The only thing would be getting a wheel truing stand to get them trued up, but that's not really important at low speeds.

I'm currently working on cutting out sprockets. Alro steel just happened to put a retail outlet a couple miles from work, and 1/8in steel plates are cheap and accessible now. 1/8in is just the right thickness to machine out bicycle chain sprockets.

The engine sprocket is 14 teeth. I'm planning on a jackshaft with 30 teeth and 10 teeth, followed by a 30 tooth axle sprocket. This is just for starters, as I'd like to add a derailleur and a high gear at least. I have to balance pulling power, speed, and steam usage. I can't really be sure how it's going to act until I try it.

 

[rolphill]

The exhaust and blast pipe are plumbed up. I used a section of automotive heater hose as a flexible coupling between the engine and the boiler to allow for chain adjustment/alignment. The blast pipe is centered-ish in the stack. Unfortunately, the takeoff for the blowdown / gauges sticks way up and gets in the way. I might machine a custom "turret" type fitting to get rid of the obstruction, and then make a centering bracket.

The transmission machining is almost done. All I have to do is plumb the feed water and I can finally do an actual test with the engine and boiler together! I'm considering adding a small water tank on the front.

Speaking of free running the engine, I happen to have a big fat brushless motor that would be a perfect match for the engine as a generator. It's 525kv, and rated for around 1500 watts as a motor. It wouldn't be much trouble to make a bracket for it and hook it up to the engine. I bet I could make a couple hundred watts at least. I would want to make some circuitry to efficiently couple it to a load though. Connecting it directly to a battery through a rectifier is very inefficient.

Ideally I would use an MPPT style controller (like solar panels use) with additional feedback from the boiler pressure. But I'm building a vehicle, not a power plant, so that's super overkill. So I was thinking about using an off the shelf buck-boost converter, with the current limit controlled by a lever manually. This would allow me to manually control the load on the engine.

In any case, I'm on vacation next week, so I hope to make good progress!

 

[100model]

The harbor freight wheels had way too much drag between the cheap bearings and the wide tires in grass. This is a significant loss since I only have half a horsepower or so to work with.

I would not have believed that until I tried to run a electric scooter with worn out batteries of the driveway onto grass. i was amazed on how slow it was on the grass and how it suddenly speeded up back on the driveway.

 

[Steamchick]

Great stuff! I enjoyed your slightly unconventional but "effective" engineering of the boiler...
Just be careful of water-feeding and pressure management, as that is a Hot-Bomb between your knees... (Although many model loco drivers do the same on weekends). Steam and hot fires burn, whatever the boiler safety and configuration. - It is usually the outside fittings that fail, especially when the whole thing falls-over by accident! - Then you get scalding hot steam cooking the flesh it "meats" - sorry, that should read "contacts!" - Rather like spilling a pan of hot oil off the cooker.... (not nice, but RARE). Don't let anything happen to you, especially when kids are around.
I like your "It's 525kv, " generator. Sparking 12ft long!? I designed and made HV switchgear at work for 400kV (UK max distribution voltage) and 525kV (export countries). Generators were typically always only 33kV max... (I also did a stint design and installing Busbars in power stations, etc.), - But I think your little finger just got excited and hit the "letter k".... Otherwise you have a hell of a bit of kit!
Enjoy!

 

[Steamchick]

I think I appreciate where you are coming from using Automotive heater hose.... for the steam.
But - A cautionary note (again). That hose is DESIGNED for 1.2 ~2 bar running - say 260 deg.F. But you propose using "proper steam pressures and temperatures" - I am guessing 6 bar? Over 340deg.F? My worry is that the BURST pressure of the hose is likely to be "in excess for 6~8 x NORMAL working pressure... - and AUTOMOTIVE designers work to the lower limit so the costs are minimised. I.E. 6 x 1.2 bar is 7.2Bar... but using a material that may not survive your pressure at your elevated temperature. - It will simply cook - like steak left in a hot oven - go hard, brittle then break - catastrophically! - Leaving you at the open end of a hose blowing steam at high temperature. = far more heat than boiling water. Please use a metal tube that is safe. Make a few coils in the pipe from boiler to engine to permit a small adjustment, and LAG the tube well to avoid losing all the heat in transit to the engine.
From the web:
High Temperature EPDM Rubber Water Delivery Hose

Tube	Smooth EPDM black rubber.
Reinforcement	Textile braid
Application	Delivery of hot water, slurry, etc
Temp Range	-30°C to +100°C (intermittent to 130°C/266°F)
Safety factor	3 x working pressure

Car hoses won't be much better, as the material' temperature resistance is the weak link.
"silicone" hose is a similar hose but the inner layer is silicone.... CHECK heat ability before you buy. - BUT I Recommend a proper metal pipe. with proper fittings for the steam connection. (NOT a "flexible" pipe either!).
Sorry to be a bother, I don't want anyone, ever, to experience a steam injury. (My friend did!).
K2

 

[The Ignoble Troll]

I think I appreciate where you are coming from using Automotive heater hose.... for the steam.
But - A cautionary note (again). That hose is DESIGNED for 1.2 ~2 bar running - say 260 deg.F. But you propose using "proper steam pressures and temperatures" - I am guessing 6 bar? Over 340deg.F? My worry is that the BURST pressure of the hose is likely to be "in excess for 6~8 x NORMAL working pressure... - and AUTOMOTIVE designers work to the lower limit so the costs are minimised. I.E. 6 x 1.2 bar is 7.2Bar... but using a material that may not survive your pressure at your elevated temperature. - It will simply cook - like steak left in a hot oven - go hard, brittle then break - catastrophically! - Leaving you at the open end of a hose blowing steam at high temperature. = far more heat than boiling water. Please use a metal tube that is safe. Make a few coils in the pipe from boiler to engine to permit a small adjustment, and LAG the tube well to avoid losing all the heat in transit to the engine.
From the web:
High Temperature EPDM Rubber Water Delivery Hose

Tube	Smooth EPDM black rubber.
Reinforcement	Textile braid
Application	Delivery of hot water, slurry, etc
Temp Range	-30°C to +100°C (intermittent to 130°C/266°F)
Safety factor	3 x working pressure

Car hoses won't be much better, as the material' temperature resistance is the weak link.
"silicone" hose is a similar hose but the inner layer is silicone.... CHECK heat ability before you buy. - BUT I Recommend a proper metal pipe. with proper fittings for the steam connection. (NOT a "flexible" pipe either!).
Sorry to be a bother, I don't want anyone, ever, to experience a steam injury. (My friend did!).
K2

To add, compressible substances should use tube that has 4x safety factor while incomprehensible stuff like hydraulic fluid gets 3x.

 

[rolphill]

I think I appreciate where you are coming from using Automotive heater hose.... for the steam.
But - A cautionary note (again). That hose is DESIGNED for 1.2 ~2 bar running - say 260 deg.F. But you propose using "proper steam pressures and temperatures" - I am guessing 6 bar? Over 340deg.F? My worry is that the BURST pressure of the hose is likely to be "in excess for 6~8 x NORMAL working pressure... - and AUTOMOTIVE designers work to the lower limit so the costs are minimised. I.E. 6 x 1.2 bar is 7.2Bar... but using a material that may not survive your pressure at your elevated temperature. - It will simply cook - like steak left in a hot oven - go hard, brittle then break - catastrophically! - Leaving you at the open end of a hose blowing steam at high temperature. = far more heat than boiling water. Please use a metal tube that is safe. Make a few coils in the pipe from boiler to engine to permit a small adjustment, and LAG the tube well to avoid losing all the heat in transit to the engine.
From the web:
High Temperature EPDM Rubber Water Delivery Hose

Tube	Smooth EPDM black rubber.
Reinforcement	Textile braid
Application	Delivery of hot water, slurry, etc
Temp Range	-30°C to +100°C (intermittent to 130°C/266°F)
Safety factor	3 x working pressure

Car hoses won't be much better, as the material' temperature resistance is the weak link.
"silicone" hose is a similar hose but the inner layer is silicone.... CHECK heat ability before you buy. - BUT I Recommend a proper metal pipe. with proper fittings for the steam connection. (NOT a "flexible" pipe either!).
Sorry to be a bother, I don't want anyone, ever, to experience a steam injury. (My friend did!).
K2

I think you all missed the part where it's an exhaust hose, so it doesn't see any pressure. Also, the motor isn't putting out kilovolts, kv is a measurement for brushless motors of how many unloaded rpms the motor will spin per volt (as a motor). So 525kv means that the motor will spin at 5,250rpm unloaded when driven at 10 volts. Lower numbers are better when used as a generator.

In any case, what a disappointing, unproductive, gross, hot week off.

I managed to get everything built to the point where I could test it, but it was quite the failure. I got the steering, the engine, feed water, and drive chains put together. I even quickly threw together a very simple tender.


The steering is smooth. It doesn't turn left as far as it should, as there's some interference I have to fix. The steering wheel is a bit too free, I need to add some friction so it doesn't turn by itself.


The chain drive was a big pain. Apparently the chamfers on the ends of the teeth are very important if there's any misalignment. I had to take all the sprockets off and grind chamfers on all the teeth to keep the chains from coming off. Luckily I'm using bicycle chain which is much more tolerant of misalignment than regular chain. I still need to install a tensioner pulley to one of the chains.


I managed to find a spot to install the hand pump. It's not a good spot (right now), but it works. I also added a little bracket for an oil can.


Unfortunately, my first test was a complete failure. First problem: the engine water pump seized almost immediately! The piston is so seized in the bore that I can't pull it out. The clearance must have been way too close. I had to completely remove the bracket connecting the pump piston to the engine piston rod. Also, when it seized, the crankshaft slipped, and threw off the cylinder timing relative to each other. The crankshaft is made using pinch style connections. At least the eccentrics are also the crank throws, so it's impossible for a cylinder to lose timing, but with the cylinders no longer at 90 degrees, the engine no longer self runs. There's not nearly enough flywheel for that. I was able to get it back, but by then there was another problem. Oh, and the chains came off. This was before I chamfered the teeth.

By the time I got the engine turning again, the boiler had a problem. While the fire was fresh and new, there was plenty of draft pulling air up through the grate. However, once ash began to build up, the air resistance through the fire became too high, and any draft just pulled air through the plumbing gaps in the top of the shell, instead of up through the grate. So I couldn't make much steam, regardless of blower or engine blast.

It was also around this time that the steam whistle decided to just flop over. I guess it was tight when cold, but came loose in the heat. Also, I'm still having problems with water carryover. You can easily tell in the one short video of the engine turning I managed to get.

Oh and some minor issues to add insult to injury: The whistle and relief valves need to be moved somewhere not right above my knee. I can't see into the fire door hardly at all. It's incredible how much harder it is to roll on grass versus a hard surface with my weight on it, so I'll be pulling it to my driveway at least next time. Also, I don't have any control linkages for the cutoff made yet. At least the (flopped over) steam whistle works?

So, after a very disappointing setback, it's time to take a step back and make a list of the things that need to be done:

1. Rebuild the engine water pump completely, this time with a stainless cylinder instead of mild steel (and larger clearance), and fix the janky drill hole plugs.

2. Rebuild the crank shaft with keyways instead of pinch bolts. I might have to remake the eccentrics as well.

3. Rebuild the top of the boiler. I'll make some custom fittings so that I can make everything flatter and keep it from sticking up too much. I'll also extend the shell, so I can seal plumbing perforations and keep them out of the part where the top goes on. The nice thing about this boiler is that I can just unbolt the entire top flange and bring it in to figure out what I want to do with it.

4. modify the pipework so the relief valves and steam whistle aren't right above my knee. The steam whistle especially dribbles a lot of hot water before it warms up.

5. Build linkages to control the cutoff lever.

6. Insulate all the piping and the engine head. I'd rather not use fiberglass. I was thinking about cotton or wool. I have a ton of high temperature kapton tape, which is ugly, but super high temp rated.

7. chain tensioner.

8. Finally, more stationary steam tests with the engine not hooked up to the wheels (or the wheels lifted off the ground).

9. Oh, and make some fenders for the rear wheels. If I let my legs out they rub on the wheels. This is actually a bigger hazard than the chain.

Also, I need an even easier way to crush coal. I went through the bucket of coal that I spent 20 minutes or so crushing way too fast. Or I could give up on coal and make a grate with secondary air tubes for wood pellets or burn oil or something.

I'll also eventually build a better tender that can hold coal and tools.

I have no idea what to do about not being able to see into the firebox. Maybe I could add a mirror or something? I don't have much leeway for moving the seat, as the rear axle and sprocket are in the way. I can't move it too far backwards as it'll throw off the weight and make it tip.

Other ridiculous ideas: Give up on chains and use an electric transmission. Give up on this boiler entirely and finish building my lamont boiler. Build a smaller steam engine to use less steam with fixed cutoff so I don't have to futz with cutoff levers and hackworth valve gear, and slide valves so I can maybe do away with the cylinder drains. Heck, I could build a high speed bash valve uniflow pretty easily if I could ever settle on a design.


Okay, okay, let's end on the positives:

The hand pump, check valves, tender, and wall water lines worked.
Before it seized, the engine water pump worked perfectly.
The vehicle itself rolls very smoothly on flat surfaces, and the steering works well.
Before clogging with ash, the boiler went from cold to pressure quite fast.
The secondary relief valve that I choked with a needle valve worked well, starting to blow before the main valve.
The engine still turns and it looks immaculate inside the cylinders still.
No catastrophic failures.

Most interestingly: when everything was quiet, I could hear the boiler percolating quite noticeably. It was a really interesting sound.

 

[Steamchick]

OK, I missed the part "where it's an exhaust hose, so it doesn't see any pressure".
AND thanks for explaining "kv is a measurement for brushless motors of how many unloaded rpms the motor will spin per volt (as a motor). So 525kv means that the motor will spin at 5,250rpm unloaded when driven at 10 volts". Lower numbers are better when used as a generator". I was a bit confused as to what you were trying to tell us, otherwise.
It helps when we have the knowledge... otherwise we look like numpties! I guess it is just another modern thing invented by someone for a special need, and kept within a specialist group... so "Joe Bloggs" who uses SI units and Imperial, etc. doesn't understand the language. I have BRUSH issues with my lathe motor, so learning about "Brushless" motors is a new thing for me.
But I appreciate you are talking of that only if the Steam go-kart fails to satisfy...
K2

 

[rolphill]

OK, I missed the part "where it's an exhaust hose, so it doesn't see any pressure".
AND thanks for explaining "kv is a measurement for brushless motors of how many unloaded rpms the motor will spin per volt (as a motor). So 525kv means that the motor will spin at 5,250rpm unloaded when driven at 10 volts". Lower numbers are better when used as a generator". I was a bit confused as to what you were trying to tell us, otherwise.
It helps when we have the knowledge... otherwise we look like numpties! I guess it is just another modern thing invented by someone for a special need, and kept within a specialist group... so "Joe Bloggs" who uses SI units and Imperial, etc. doesn't understand the language. I have BRUSH issues with my lathe motor, so learning about "Brushless" motors is a new thing for me.
But I appreciate you are talking of that only if the Steam go-kart fails to satisfy...
K2

Brushed motors could be rated in kv, but they are usually described using legacy terms like number of windings. Brushed motors are also usually just given a max voltage rating. Modern brushless motors are quite amazing. This one is about 1.5in x 2in and it's capable of around 1500 watts peak output.

Anyways, I got the engine and crankshaft apart. It was really interesting taking apart the eccentrics. The eccentrics used a 3d printed PLA+ sleeve pressed on, spinning against an aluminum eccentric strap. Their condition was immaculate. The aluminum eccentric straps were polished smooth, and I couldn't even see any wear on the plastic. It looks like any debris that got in the eccentric just got embedded in the plastic. I like PLA+ for applications like this as it's relatively hard, while the printed layers allow lots of space for grease or oil. The only risk is high temperatures softening it. PLA+ is more temperature resistant than regular PLA, but I've still had large PLA+ objects deform in my car on a hot sunny day.

I'm currently working on cutting 4mm keyways in all the crankshaft rods. The rods are 12mm case hardened and chrome plated, so the little 1/8th carbide end mill takes gentle circular cuts at like 0.3mm depth instead of being able to hog it out.

Next is to remake the crank webs / eccentrics. I'll be making the new eccentrics out of mild steel, and changing the design to a conventional way where there's a slot in the middle and locating bolts on the strap that ride in the slot. I'll also be remaking the eccentric straps as one piece instead of split. They'll probably have to stay aluminum unless I decide to press in some sort of bushing on the strap.

I got the water pump piston and cylinder apart. The piston is in good enough shape to clean up and reuse. I'll remake the cylinder in stainless, aluminum, or brass, and add a larger clearance.

 

[rolphill]

A bit of progress this week. I made a new water pump cylinder out of brass with a bigger clearance. New bore was made with a 0.322in reamer. The piston has good clearance but the o-ring still seems to seal.

Next, I finally received the toolholder I needed to be able to use this:


This is a keyway broach for the CNC mill. Before I use it on actual work parts, I might as well learn how to use it by converting my crankshaft to keyways. The HAAS canned broaching cycle has a lot of variables but is easy to figure out and it cuts through aluminum like butter.


The hard heheh part was milling keyways in these hardened chromed shafts. Each keyway cut took about 40 minutes.


I got the crankshaft rebuilt, and it's a pinch wonky but a few hammer taps has it spinning pretty smoothly once mounted. The engine is all back together with a repaired water pump and a crankshaft that isn't held together with friction and prayers.

 

[rolphill]

Things are turning around... literally haha.

I reinstalled the engine (no chain connection) and gave it another go. I had much more success this weekend! Literal minutes of engine turning!

The water pump worked well! Although I did notice that it was less effective the faster the engine turned. The engine water pump only has an outlet check valve. It's in "series" with the hand pump, and relies on the hand pump check valves for the inlet check. This allows me to use the large hand pump to easily purge any air bubbles out of the engine pump. However it's likely that there is cavitation at higher speeds that reduces the amount of water pumped. This isn't a big problem though. It sure was nice not to have to hand pump every little bit of water into the boiler!

Also, the small secondary relief valve behind the needle valve works perfectly! It starts spewing a little bit, then as the pressure rises it eventually reaches the point where it continuously oscillates. However the oscillations are very audibly tolerable and it doesn't pull water with it. The main relief valve didn't even need to open this time.

The engine oiler is running far too rich, I have to crack the valve ever so slightly just to get a controllable amount of oil. I think I'll eventually have to install a smaller needle valve. However it does work, and the visual indicator is very nice to have.

The engine (and everything else) runs much better at high steam pressures, as would be expected. The water carryover is also better at higher pressure. I was even able to pump water while "notched up" on the reverser. I do need to drill a couple small holes in the bottom of the exhaust piping to allow condensed water to drain out. Also the cylinder drains are a pain to reach, luckily the engine seems to be able to pass most water slugs at full cutoff after preheating at startup.

It took about 15 minutes to go from lighting the fire to having 20psi.

However, now for the problems. First, the grate clogged up again. I was able to rake the fire to bring some life back for a few minutes, but I will have to do something about that. The engine draft does not appear to be super effective between that and the air leaks.

I stuck a (sketchy old) temperature gauge into the stack just to see. In the beginning, before I even made steam, the stack temp was like 500-600. But once the grate loaded up I couldn't really get it above 400-ish. I guess my boiler is fairly heat efficient at least?

I ran without the ash pan installed, so I was able to get a picture of the grate. Looks pretty good, so maybe I should focus more on the air leaks at the top? You tell me.


The other problem: coal. In an hour of messing around I didn't use much coal by weight. However the coal I used took some 20 minutes to crush by hand. That is way too long. I either need to build/buy an electric coal crusher, or switch fuels.

I was thinking about trying wood pellets. I know I would have to figure out how to add secondary air inlets. I've got those cleanout ports on the bottom, so I could probably do something with those. On the plus side, I was concerned about fire door visibility from my seat, but I didn't seem to have much issue with not being able to see well into the firebox this time. I just kind of pushed coal in through the door and then raked the fire.

The engine is probably a bit on the big size for this boiler. It would probably work a bit better if it was a smaller engine turning faster. However it may act better once I hook it back up to the wheels and it has to turn more slowly.


I did try to help the air leaks by adding a bit of aluminum tape to seal the pipework holes. It helped a bit, but probably not much. I also plan on adding insulation to the engine and exposed pipes sooner rather than later. No reason to waste heat when I'm already boiler limited.


This week I plan on taking the flange off and making custom fittings so all the plumbing goes through sealed permanent holes in the sides. I'll try to get a picture of the inside of the boiler, for posterity. I'll also try to make some sort of exhaust pipe mounting bracket to hold it steady in the center.

 

[The Ignoble Troll]

That engine sounds delightful!

Instead of BUYING an electric coal crusher, why not whip one up that can be belt or chain driven by the engine while stationary - the way old tractors used belts as their PTO to power stationary machines, like crushers!


Great to hear the engine's song.

 

[rolphill]

So umm, I accidentally another steam engine...


It's fairly obvious that the engine I've been using is too big (unless I stick it on something that has a big load to keep the rpms down). I haven't had much if any time to work on hobby stuff at home lately, but we did decommission an old assembly line at work and I was told to "fill up my trunk" so among other things I grabbed all the nice chunks of steel and aluminum I saw. I was motivated to build a smaller steam engine.

I based it on one of my early steam engines that ended up surprisingly well engineered for being one of my very first designs. This is a two cylinder single acting engine 1.25in bore x 30mm stroke (sorry, o-rings are standard but I design in metric!), with rotary slide valves. I have intentions of eventually making it cam operated like the original, but to start it'll just have a regular eccentric.




The spreadsheet says it'll hit half a horsepower at ~1000rpm, so I'll have a good bit more rpm range to work with.

I pulled the top flange and there was a bit of iron sludge from the original test water, but otherwise it looked fine. The seal was destroyed, so I'll have to replace it with some high temp RTV. I did machine a new turret, but I still have to rebuild the top of the shell once I put it on.

I've been interested in boats again lately. The only problem is that I'd never get a chance to sail a steamboat that couldn't fit my wife and kid, and this boiler is too small to power anything bigger. I do have an aluminum rowboat that needs just a bit of work though. I think I might put the first engine in that and put my monotube firebox back together and rig it up as a wood fired computer controlled monotube boiler, or make it a lamont like I originally intended it.

 

[rolphill]

Exciting new developments! Success!

I finished rebuilding the top of the boiler somewhat. I removed the exhaust blast pipe, and tried my best to seal all the shell penetrations with aluminum tape. Then I finally got a chance to fire it up last night. This time I used wood pellets instead of coal, and I actually got more steam than I ever have before!

Wood pellets worked amazingly. I figured out that the best way to fire with them was to just feed them in the fire door so the fresh pellets are in front, and leave the fire door open. Fresh wood pellets release a ton of volatiles before turning to charcoal. So feeding the firebox from front to back seems to be ideal. The secondary air rushes in through the open fire door, mixing with the volatiles coming off the fresh pellets and burning vigorously. As the pellets burn off, they slowly convert to charcoal and move towards the back of the firebox. So the back half of the fuel pile is charcoal.

I had no grate clogging issues, and the natural draft of the boiler was plenty enough to make lots of steam with the steam blower only being used a tiny bit in the beginning. Having a thermometer on the stack was essential, and I did plenty of experimenting. The pellets burn best and produced the highest stack temps with this front to back method. I tried evenly spreading pellets, but that would actually tend to snuff out the fire, as well as making more smoke and lower stack temps. Also, for secondary air, I have the firedoor, as well as two 1in diameter cleanout holes on either side of the firebox. I had both cleanout holes open, although there was certainly some coal and ash in there. I poked it through a bit, but they probably weren't super free flowing. Closing the fire door also increased smoke and decreased stack temp. I've read that pellet smoke is "sticky" when it condenses on the boiler, so minimum smoke is important. My stack thermometer is old and has been overheated a few times, so it's accuracy is questionable, but it hovered between 500 and 700f while making steam.

Speaking of steam generation, there was plenty this time! I hovered around 60psi most of the run, and there was enough steam to run the engine constantly for once as long as I kept the fire well fed. However there was still a good bit of water carryover, so next time I'd like to try to stay closer to 80psi where the carryover is reduced. I'm no longer concerned that my engine is too big for this boiler though, which is a significant step forward.

I did have one problem though. You can see in the video how the engine wants to stop and surge. Part of that is from the engine being unloaded and having lots of superheater volume. However I found out at the end of the run that the engine wasn't getting any oil! Instead of cracking open the lubricator valve, I had simply unscrewed the knob from the valve stem. I noticed that without oil the o-rings will get "sticky" whenever the engine stops, and require a significant force to get moving again. I'll probably want to check the o-rings for damage, but my immediate next step is to replace the junk needle valve with a better one that also has finer adjustment.

I also need to figure out how to put a load on the engine while it's on the bench. I think I'll try to hook it up to that brushless motor.

 

[The Ignoble Troll]

That's fantastic that wood pellets work so well with your fire box geometry.

In the long ago past I built a semi successful forge that used pellets the way you did. It degassed them rendering them into chaocoal nodules which I used to heat steel. I unfortunately gave up on it because my grate kept filling with ash, unlike yours, but the heat from the burning charcoal was immense. They are just about the perfect size for airflow/surface area. I always wanted to harness that power for a boiler but had nothing to power a boiler with... so it remained an unanswered pipe dream.

Very stoked to see your successful implementation!