Trackless Locomotive Build

[rolphill]

First, a question for everyone: what does everyone use for gasket material? I was using 12-pack soda box cardboard, but I'm starting to get bubbles through them.


Okay, I pulled the top end apart. The good news is that the linear ball bearings for the crosshead are still sliding smoothly. I believe they are stainless steel, but I'm still impressed. I don't think I'll have to replace them with bronze plain bushings. I also don't see any wear or damage on any of the bores.

The bad news is the silicone o-rings on the piston valves have lots of vertical cuts in them, and one of the (viton) piston o-rings is damaged. I'm not super surprised for either of them, but it's still annoying. I didn't make the o-ring grooves on the pistons correctly, as those were some of the first parts I made. There is way too much clearance between the piston and the bore, so the o-rings were at risk of getting extruded. I may remake them, if I can find some more brass of the right size. Or maybe I can make them out of aluminum to match the cylinders? I would replace the silicone o-rings with viton, but I'm out of them, and the o-ring store has a minimum order value.

I was thinking about machining a slight enlargement at the valve ports with a special v shaped cutter I have (similar shape as a threadmill). The pneumatic spool valves have such a feature, so it's probably a good idea.

 

[Steamchick]

Moving the working edges of the valve ports will change the valve timing. "Don't do it unless it is designed to have it." is a very sensible rule to follow.
K2

 

[rolphill]

I did end up making a small cavity on the valves. I used a 60 degree notch tool and increased the diameter by 0.6mm, while also making sure to minimize the amount of increase in the size of the passages. I was able to steam it up for a quick second, this time with lubrication, and it worked just like it used to, maybe a pinch better.

I still have the issue of the engine water pump not working very well at anything more than minimum rpms. I suspect the small diameter water lines (and possibly a clogged filter) are contributing. Regardless, I think I'm going to change the routing so the crosshead pump doesn't have to pull water through the hand pump check valves.

 

[rolphill]

I made a new flywheel.



That's it. Hopefully this will help me test shortening cutoff and such.

 

[rolphill]

I have had a rousing success last night! It's so angry!



It took some time to figure out the fire, but I was able to get the engine thundering at quite a speed while the boiler maintained pressure, even gaining pressure a little! The engine was also pumping water into the boiler slightly faster than it was consuming it. I was also able to notch it up quite a bit, however I still couldn't open the throttle all the way without a load.

It was kinda tricky, but it seems that as long as I can maintain the stack temp reading around 700f, it makes plenty enough steam for the engine, as long as it's near or above 80psi, no blower needed. At higher pressures, the engine is more efficient, and the water carryover is unnoticeable. I was also able to notch the engine up quite a bit thanks to the new flywheel. I was able to maintain this thundering pace for several minutes without having to significantly mess with fire or controls.

Change list for this run:
I added a new smaller needle valve to the lubricator, although it still just needs to be cracked a tiny bit to give a proper oil rate, I can actually control it better.
I also installed that much bigger flywheel, and it made a big difference.
Finally, I redid the feed water plumbing, to put the engine pump before the hand pump, as well as removed a connector that was causing a significant restriction. Now the engine water pump is able to maintain water level even at higher speeds.

Things to work on now:
Many of the gaskets on my engine seem to be leaking. I need to redo all the gaskets.
I need more practice firing it. The firebox doesn't like being overfilled, and also burns better once everything gets hot.
The piston on the engine water pump leaks a good bit when pumping, maybe revisit?
I need proper steam oil, gear oil stinks.

Oh, and I've changed my mind again. This boiler is too finicky to handle on a land vehicle. If it was a firetube, with bigger water reserve and slower pressure change, it wouldn't be so bad. Or if I added automatic controls like water level or liquid fuel. I think I actually am going to put this on a boat. Last year my FIL gave us his old aluminum fishing boat, and I've started fixing it up. All the wood needed replacing and paint and such. However, since it is my FIL's boat, my wife has a strong nostalgic attachment to it, and thus I get significant leeway to work on it as far as time and funding goes!

edit: I went through the video frame by frame and the engine is spinning about once every 3 frames, which is about 580rpm. Neat!