Moriya Stirling Engine Build

[NP317]

Ah yes: The gland and the displacer cylinder cover. Brass into aluminum, if I remember correctly.

My experience is that high precision is not required to make the Moriya fan project. My students had high degrees of success.
The few times when the press fit was insufficient between the brass gland and the cylinder cover, they just center-punched several places around the
gland and pressed it back together. The gland stayed in place and worked. Internal operating pressures are quite low in this engine. Several psi at best.

To secure the bearing cups in the tops of the bearing stands you can even use LocTite products. Super glues. No biggie

Reaming speeds: Lathe rpm 100-60. Or less. Oil the reamer. I've even done reaming successfully by hand turning the chuck.
Again: Don't over think this project. It is surprisingly forgiving to build. Just do it. Go slower when in doubt.
And keep sharing pictures of your progress!
RussN

[rmac]

Ah yes: The gland and the displacer cylinder cover. Brass into aluminum, if I remember correctly.

Correct.

My experience is that high precision is not required to make the Moriya fan project. My students had high degrees of success. The few times when the press fit was insufficient between the brass gland and the cylinder cover, they just center-punched several places around the gland and pressed it back together. The gland stayed in place and worked.

That sounds like a good hint to keep in mind. But for me right now, this project is as much an exercise in machining as it is just getting an engine to run. So in general, I'm trying to do as good a job as I can, which means just remaking any parts that I mess up. At least until I run out of material, that is!

Reaming speeds: Lathe rpm 100-60. Or less. Oil the reamer. I've even done reaming successfully by hand turning the chuck.

Hmm. That slow, eh? This afternoon I reamed some 3/8" holes in 1/8" thick aluminum for the bearing stands. I took a hint from Abom79 (on YouTube), who suggests running your reamers at about half the speed you would use to drill the same sized hole in the same material. That worked out to about 750 RPM for what I was doing. I'll admit that it seemed a little fast at the time, but it seems to have worked like it should.

Again: Don't over think this project. It is surprisingly forgiving to build. Just do it. Go slower when in doubt. And keep sharing pictures of your progress!

Will do. With any luck, I'll have some pictures tomorrow of some bearing stands with some bearing cups pressed in.

Thanks one more time for your interest, help, and encouragement.

-- Russell Mac

[mcostello]

I was taught reamer speed is 1/2 drilling speed and twice the feed.

[NP317]

I was taught reamer speed is 1/2 drilling speed and twice the feed.

That likely makes sense. I'm surprised Harold hasn't spoken up to correct my comments.
Always welcome.
A day not learning is a lost day.
RussN

[rmac]

Progress Report #3:

I got the bearing stands and bearing cups 90% done today (still need to clean up the edges of the bearing stands). The plans say to rivet the "feet" of the bearing stands to the upright parts, but I decided to attach them with cap screws instead. I realize now that the heads of the screws may interfere with the power cylinder, but haven't checked for sure yet. If that turns out to be a problem, I'll just move the power cylinder over a little bit.

I didn't have any trouble getting the press fit between the parts to work. As noted earlier, I reamed the holes in the uprights so they all had a nice and uniform 0.375" diameter. Then I used Harold's famous "get close, then take three equal cuts" routine to hit 0.376" on the cups. Both parts are aluminum and they smooshed together without incident in my bench vise.

The picture shows two of the stands bolted (temporarily) to one of the hot ends, just to see if the bearings were going to line up. At least with that pair of stands, the answer is yes.

So far, so good.

-- Russell Mac

[NP317]

Nice progress! Looking' good.

Those cap screws can be replaced with countersunk screws so they do not interfere with the power piston placement.
Moving the power piston implies changing the base plate layout and the crank shaft length. Not worth going there, in my opinion.

And the crankshaft stand bearing cap should be flush with the outside of the stand, otherwise it will interfere with the outer crank, which will not line up with the power piston.
Keep machining and enjoying!

RussN

[rmac]

Nice progress! Looking' good.

Thanks!

Those cap screws can be replaced with countersunk screws so they do not interfere with the power piston placement. Moving the power piston implies changing the base plate layout and the crank shaft length. Not worth going there, in my opinion.

I thought about countersunk screws, but decided against them for a couple of reasons.

And besides that, I have a second reason to move the power cylinder. The plans call for the power cylinder to be machined from a big chunk of solid bronze. Instead of converting a bunch of expensive metal to chips, I decided to fabricate that part (sort of like the hot end) from a piece of tubing and a flat plate for the flange at the bottom. In order to do that, I want to make the flange a little wider than the plans show, which also means the cylinder has to move a little bit.

We're only talking 1/16" or so here, so it's no big deal to change the base plate at this point. I haven't decided exactly what to do with the crankshaft yet, but there are two or three ways to get that 1/16" back.

And the crankshaft stand bearing cap should be flush with the outside of the stand, otherwise it will interfere with the outer crank, which will not line up with the power piston.

Not so. The plans show the caps proud of the stand like I have them. I'm not sure why. In any case, my CAD model confirms that everything lines up.

-- Russell Mac

[NP317]

OK. Good to hear those things.
You've got it. Well thought out.
RussN

[Sandiapaul]

I used graphite for the piston, it worked great to get a good seal. I also used loctite for putting the crankshaft together, that worked well also. I used #609.

Also if you want you can check out the whole build here. I did this with my 13 yr old nephew years ago

https://www.homemodelenginemachinist.co ... ild.24771/

[rmac]

Sandiapaul: I read through your write up on the other forum a week or two ago. Very nice!

-- Russell Mac

[Sandiapaul]

Thanks Russell!

[rmac]

Progress Report #4:

I cut a bunch of fins yesterday and finished the cold ends today.

For cutting the fins, the plans suggested 1) running the lathe in backgear at its slowest speed, 2) using the power crossfeed at its slowest setting, and 3) applying lots of lubrication. Not knowing any better, I did all that. Everything worked just fine, but it was really, really slow. Someday I'll try an experiment to see what kind if disaster happens if you crank the RPMs up some.

-- Russell Mac