25 HP Nash

Home Model Engine Machinist Forum

Help Support Home Model Engine Machinist Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

Since the Nash is a stationary engine and would be in an engine house, I suspect it was cooled by a cooling tower of some sort mounted outside. The Steampunk look is always interesting.

There were some other parts I needed before I could start to assemble the engine, Like doors so the oil doesn't fly out of the crankcase. IMG_2429.JPG IMG_2427.JPG IMG_2426.JPG

And doors need handles
IMG_2440.JPG IMG_2443.JPG IMG_2445.JPG

A little tool to hold them for filing and sanding

IMG_2455.JPG IMG_2456.JPG

And screwed to the doors.
Little parts seem to take a lot of time!
More in a little while,
Thanks for looking!
This engine uses a wasted spark ignition, with two magnets on the flywheel. The ignition came from Roy Sholl at cncengines.com. It uses a wasted spark, so both plugs fire at the same time (as I understand it) and two magnets so they fire every 180 degrees. I put brass sleeves in the smaller flywheel and will glue the magnets in after I'm sure of polarity.
IMG_2431.JPG IMG_2434.JPG
I had decided to make all the coolant piping from PMR fittings and pipe. I think it made for a lot of extra, very fiddly work. I also had to drill and tap the fittings. The "Ts" and elbows weren't so bad, but the 45s were a real pain to hold.
IMG_2488.JPG IMG_2490.JPG IMG_2481.JPG

The wood mounting is just to get it running, I'll make something more permanent when I've figured out where things will go.
I'm not sure I like where the coolant feed line is running right now, so that may change.

Need to figure out the demand valve and fuel (propane) feed.

Thanks for looking!
Because this will run on propane, it needs a demand valve. The demand valve opens on the piston's intake stroke (suction) and otherwise keeps gas from leaking. I used the plans and parts from www.jerry-howell.com . There are really only two parts to make, the body and the cap, plus whatever adapters are needed to connect the gas. These are all the parts.

and the demand valve assembled
It seems to allow flow when I suck on the outlet side, and not allow flow when I blow on the inlet side, so I think it is working. Only supposed to have 4 or so PSI on the inlet.
I have everything apart, ready to assemble and try running.
I'll be back as soon as that happens.
Thanks for looking!
Doug, I built the same demand valve recently and found it would not completely shut the propane flow off. I found this by submerging the outlet tube in water. Propane was leaking past the threads on the needle valve housing. Some teflon tape fixed the leak. You probably won't have this problem but I wanted to mention it just in case.

It's been a while, but Spring came to Vermont, and all that comes with it. (mud, yard work, other outdoor stuff) I've been working, but not looking like I accomplish much. There were a few more parts to make and start to assemble:
IMG_2512.JPG IMG_2519.JPG IMG_2522.JPG
Wrist pins, handrail stanchions and rail,
IMG_2523.JPG IMG_2524.JPG IMG_2527.JPG

IMG_2530.JPG and the step to reach the cylinder heads.
I started to assemble the valve train
IMG_2504.JPG Lifters, rocker arms and wheels,
IMG_2533.JPG and all together. there is a "faux governor" you can see in the middle.
Someday I'll learn how to make those gears, but for now they're plastic.
I got the valves in the heads, the cams set and the pistons assembled in the cylinders. Piston vacuum and compression felt ok, hand-over-the-hole test,
but the valves were not as well sealed as I thought they were. So I took it apart again, made a valve seat cutter and re-seated the valves.
I think that's all for right now, more tomorrow I hope.
Thanks for looking,
I had it all together to check compression, got the valves adjusted and the cams timed, and the compression was pretty bad. I had seated the valves before the valve cages were pressed in, and I think they may have changed shape.
IMG_2543.JPG IMG_2537.JPG

In the past, I had made a valve seat cutter from a drawing in one of Upshur's plans, and it didn't work very well. This time I used the same kind of technique as for a gear cutter. I turned the cutter to 46 degrees and the original seats were 45 so it would cut near the top most. I cut six flutes then relieved the backs with a small end mill. I was figuring out how to do this on a piece of 12L14 before I went to O-1.
It came out well enough that I just case hardened the 12L14 stoned the edges and tried it. It only had to cut bronze, and it worked! so next time I'll make it more permanent.
IMG_2575.JPG IMG_2576.JPG IMG_2601.JPG
I lapped the valves with Clover and a little extension that threaded onto the end of the valve. It took a couple of tries, but I got them to seal reasonably well.
I had seen this method of testing valves somewhere here, so thank you to whoever this came from. It worked nicely.
IMG_2588.JPG IMG_2587.JPG
an inexpensive brake bleeder for vacuum and silicone plugs for connectors.

IMG_2605.JPG IMG_2607.JPG
While everything was apart, I started painting the parts that shouldn't need any more work. The color got much grayer as it dried, it looks a bit beige here.
That about catches up. the finish work always seems to take a long time with little visible progress. Time to get it together!
Thanks for looking,
I had been thinking about a mount for this engine. Because the flywheel protrudes past the bottom of the crank case by over two inches, it needs to sit up on something. Or have the flywheel go into a cut out in the base, and I didn't want to do that. I made a "plinth" for the motor to sit up on. It's riveted steel angle and sheet. The rivets are 1/16" round head brass. I first tried gluing the parts together with JB Weld so I could drill them It sort of worked, but some of the joints were too small to be strong.
IMG_2637.JPG IMG_2638.JPG IMG_2639.JPG
I made some little tools for riveting. the one on the left fits in the hole in the anvil (pritchel) or could go in a vise. this has the shape of the rivet head in it, so the head doesn't get flattened out when you pound on it. the center one sets the rivet tight in the hole, and the third has a rounded dimple in the end to form a head on the inside. I know that it can be done to buck the inside and hammer from the outside, but this is kind of small, and strength shouldn't be a problem.
IMG_2635.JPG IMG_2636.JPG IMG_2642.JPG IMG_2650.JPG
In these pictures, the first was glued and drilled, the second with rivets just dropped in the holes, the third with rivets set, and the last, from inside. Riveting the final edges was a bit difficult. I drilled them all with the parts together, then riveted just the top on, slid that in and did the two vertical ends of the long sides. Also, hard to keep square.
IMG_2658.JPG IMG_2654.JPG IMG_2656.JPG

The top was riveted on and used to square the base to the top. The top was flush riveted because the crankcase had to sit over the rivets. The top is drilled and tapped for studs to bolt the crankcase down. I plan to mount the water pump on the side of the plinth, and probably the hall effect pick up also.
The rivets came from Godshall's Custom Machine/ American Model Engineering.
That's all for now.
Thanks for looking!
It's been quite a while. Seems as though I worked a lot and had little to show for it. Making an engine is one thing but making it run is another.
Anyway. A lot of finish work, painting and fitting.
IMG_2715.JPG IMG_2678.JPG
The base, painted with attachment feet, and the Hall Effect pickup

IMG_2681.JPG IMG_2737.JPG
assembled enough to set the valves.
The little brass piece replaces a spark plug, then if you put compressed air into the cylinder, you can hear when the valves open and close,
or where you may have leaks. It verifies what you have done in setup.
IMG_2753.JPG I tried with a bike pump, but I really don't have enough hands. I used a small
compressor and set the output for about 15 psi and that worked pretty well. There is also a probe that fits in the through hole that I used to measure TDC.
IMG_2716.JPG IMG_2721.JPG
I mounted the water pump on the base for a belt drive next to the timing gears.
IMG_2740.JPG IMG_2758.JPG
I also made a "Hucks Starter" for it.

Next time I'll tell you about trying to start it.

Thanks for looking,

This engine is to run on propane. I built the demand valve. I had gotten a propane hose with an adjustable regulator.
Rustkollector had said you need to open the needle valve quite a lot more than for liquid fuel. Also, the carburetor that was recommended
isn't made anymore, so I made one to GBritnells plans. When I first tried to start it, I would get some pops, but only with my thumb choking the air intake almost fully. Seemed like it was way too lean even with the needle valve way open.
Sometime in here, I found I had a weak joint in one of the connecting rods. It separated from the big end. Grrr!
So, a bunch of disassembly, clean up the parts and re braze. This time I drilled a tiny hole in the side of the big end to meet the hole the shaft of the connecting rod as a vent, because I wondered if pressure buildup had kept the silver from penetrating. There was plenty of heat.

In reassembly, I changed a few things about the cams. The cam carriers have 4-40 set screws and I milled a flat for those to sit in.
The cams themselves had 2-56 x 1/16" set screws which use a .035" Allen key. They didn't feel like I could get them tight enough to prevent slipping, so I replaced them with 3-48 x 3/32" set screws which use a .050" key. Not much bigger, but they feel a lot stronger.

To solve the lean mixture, I made a restrictor for the air intake:
IMG_2764.JPG IMG_2765.JPG

And made a new jet with a larger hole, larger needle, and larger feed line:
IMG_2770.JPG IMG_2771.JPG
I was trying not to do anything I couldn't undo if it didn't work.

IMG_2782.JPG IMG_2784.JPG

I had gotten short runs with no coolant in case I had to take it apart again, so yesterday I filled it with coolant and got it running!

It runs. I think it will need a larger cooling system as it heated up fairly quickly. Right now, I'm just happy to have it running.
I guess the next thing is to make a more permanent wooden base for it and eventually figure out a generator.
That's all for now.
Thanks for looking!


Latest posts