Moriya Stirling Engine Build

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rmac
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Re: Moriya Stirling Engine Build

Post by rmac »

NP317 wrote: Wed Feb 24, 2021 1:02 am And nice job machining, brazing, and cleaning them!!
Thanks. I'll have to admit to cheating when it comes to the "cleaning" part by doing most of the machining after I brazed the tube to the flange. Cleaning won't be as easy with the crankshaft, however. I suppose that'll just involve a bunch of manual work with files and emery paper.

One thing I don't understand about silver soldering is the idea of "pickling". In a couple of YouTube demos, after silver soldering the guy dunked his part in some sort of acidic concoction to "pickle" it. But I haven't seen any explanation of what this is supposed to do.

-- Russell Mac
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NP317
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Re: Moriya Stirling Engine Build

Post by NP317 »

rmac said: "Maybe I worry too much."
Well... yes.
:lol:

For cleaning, I usually soak the brazed parts over night in regular white vinegar, in a plastic food container. (I buy it in the gallon jug at the market.)
This a a simple substitute for the more "normal" dilute acid bath used by many. Copper alloys parts especially like this cleaning method.
The next morning, it all cleans up nicely with a tooth brush and warm water. A visit to the buffing or deburring wheel also might be useful.
Sometimes it requires a little more soaking and effort, but rarely. I usually use the black flux for silver brazing.

And it often makes sense to do some more machining the remove the excess brazing material, if I used too much.
The crank shaft can be soaked/brushed clean, and then some filing and machining will be required after cutting the center out of the main shaft.
Especially to square up corners at the solder junctions. This provides clearance for the main connecting rod, and shaft bearings.
You will easily see what is needed.

Don't worry...
RussN
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Harold_V
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Re: Moriya Stirling Engine Build

Post by Harold_V »

For those who might wish to pickle items, that is commonly used is dilute sulfuric acid. It is chosen because it does not dissolve copper when dilute, but does dissolve copper oxides. It also doesn't attack the silver, although prolonged exposure would dissolve a trace. Bad thing about this pickle is that it dissolves ferrous items, so it's not a viable choice for many projects.

Jewelers use a product named Sparex for pickling. I do not know if it dissolves ferrous, so I can't comment. I suspect it does, however.

One thing to know is that the flux is readily removed by simply immersing the part in water after soldering. If plunging the hot item in water doesn't cause any harm, that's what you should do. If nothing else, it will be free from flux and much easier to clean up.

Folks fortunate enough to own a blast cabinet have the best of all possible remedies. Using bead instead of abrasive, you can remove discoloration and flux easily. One must use care, however, as silver solder, too, can be removed.

H
Wise people talk because they have something to say. Fools talk because they have to say something.
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NP317
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Re: Moriya Stirling Engine Build

Post by NP317 »

Just for fun, attached is a close up photo of my Morita fan after 5 years of use and 30 total minutes of maintenance during that time.
I left it dirty so the true operational look is preserved. It does get wiped down occasionally.
And keeps on running...
RussN

(And of course the picture is rotated and cannot be corrected despite all attempts.)
(One more attempt was successful.)
engine_on_stove.png
Wolfgang
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Re: Moriya Stirling Engine Build

Post by Wolfgang »

Nice simple engine. I love the basic simplicity of hot air engines, and in small sizes are very easy to design and build.
The problem is that they do not lend themselves to size upgrading very easily; ie. doubling all dimensions will definitely NOT get you 8x the power of the original. It is a matter of geometry, whereas the heating/cooling surfaces increase by the square of the size increase, the volume of the working gas increases by the cube of the ratio. Consequently a larger volume of gas needs to be heated via a smaller surface area.
The difficulty are the heat exchangers, both the hot end and the cool end. These require to have "extended surfaces" if an increase in power is wished for in larger sizes.
One combination of materials that I have found to have a very long service life is a cast iron cylinder with a steel piston. Lubricated with a drop of quality sewing machine oil every now-and-then the little engine shown on Youtube under BasementEngineer has run many thousands! of hours during which I've had to replace the hot cap only once after I had chosen to use 310 stainless steel for same. Ditto material for the displacer. One combination I have not tried but was successfully used by a friend in a multi-cylinder ICE engine is cast iron cylinders with 7075 heat treated aluminum pistons.
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rmac
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Re: Moriya Stirling Engine Build

Post by rmac »

Harold and RussN: Thanks for the info on pickling.

Wolfgang: When I first saw your engine on YouTube, I thought, "That looks like the one from Popular Science." Sure enough, it was! Nice job.

I started on the bearing support uprights for my engine today, again because I already had the material for them. Mid afternoon, though, I got a box full of goodies from McMaster-Carr, so I am all set now (I think) with everything I need.

-- Russell Mac
Technical Ted
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Re: Moriya Stirling Engine Build

Post by Technical Ted »

NP317 wrote: Thu Feb 25, 2021 11:11 am Just for fun, attached is a close up photo of my Morita fan after 5 years of use and 30 total minutes of maintenance during that time.
I left it dirty so the true operational look is preserved. It does get wiped down occasionally.
And keeps on running...
RussN

(And of course the picture is rotated and cannot be corrected despite all attempts.)
IMG_3847.JPG
The base you made for having the fan on top of your stove.... is it just a round steel plate that the cylinder slides into with the cylinder actually contacting the top of the stove? Please explain.

Thanks!
Ted
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NP317
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Re: Moriya Stirling Engine Build

Post by NP317 »

Ted:
Yes: The base is a round disc turned true with a close slip fit to the hot end cylinder. The cylinder base sits contacting the stove top.
The base supports the engine (in place of the legs) and gathers heat to increase the operating speed of the fan.
I used a chunk of bronze shafting because I had it.
RussN
Technical Ted
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Re: Moriya Stirling Engine Build

Post by Technical Ted »

NP317 wrote: Fri Feb 26, 2021 12:18 pm Ted:
Yes: The base is a round disc turned true with a close slip fit to the hot end cylinder. The cylinder base sits contacting the stove top.
The base supports the engine (in place of the legs) and gathers heat to increase the operating speed of the fan.
I used a chunk of bronze shafting because I had it.
RussN
Thanks for the info! I assume the plate is steel for the needed weight to support the fan.

Thanks again,
Ted
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rmac
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Re: Moriya Stirling Engine Build

Post by rmac »

Some rookie questions:

In this engine, there are a few places where various small parts are press fit into small reamed holes. This'll be a first for me, both for reaming and trying to get a press fit. Since the reamer is going to do whatever it's going to do, it seems obvious that I'll need to ream the holes first, measure them, and then turn the mating parts to the right diameter. So far so good. Now the questions:

--- What's a good rule of thumb for cutting speed when reaming? I'm guessing you need to go way slower than when drilling.

--- It seems like a chamfer would be a good idea (or maybe even necessary) to get everything aligned and straight when starting to press the part into the hole. Good idea? Would it work better to put the chamfer on the hole or the mating part? Or maybe both?

--- I don't have a proper arbor press, but I do have a bench vise, a shiny new milling vise that I really don't want to abuse, a couple of old drill press vises that I don't really care about, and lots of C-clamps. I've also heard people talk about using the lathe tailstock to press things into parts held in the chuck. What's the best approach here?

Thanks,

-- Russell Mac
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NP317
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Re: Moriya Stirling Engine Build

Post by NP317 »

Ted:
Read my note again: The round base is made from bronze. Steel will work equally well. The fan assembly is fairly light weight.

Russell M:
Reaming speed is slow so you can control the process better.
I only remember press fits between the displacer piston and its end pieces. Fits not so tight that the thin piston tube gets distorted.
Easy to press together with your bench vice.
A slight chamfer on the end pieces helps. The thin piston wall is too thin to chamfer effectively. Just deburr those edges.
RussN
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rmac
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Re: Moriya Stirling Engine Build

Post by rmac »

NP317 wrote: Sat Feb 27, 2021 11:24 am Reaming speed is slow so you can control the process better.
Thanks, Russ. I'll poke around a little more to see if I can figure out what "slow" means.
Easy to press together with your bench vise.
Good. I thought I saw somewhere that using a vise wasn't a good idea. But they might have been doing something that required a huge amount of
force. I can't see where the vise wouldn't work for these tiny little parts.
I only remember press fits between the displacer piston and its end pieces.
The plans show a press fit between the gland and the displacer cylinder cover. Also between the bearing mounts and the bearing stands (but you made that all in one piece with your CNC machine.)

Thanks,

-- Russell Mac
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