Author Topic: Myers Stirling Stove Fan  (Read 2136 times)

Offline bent

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Myers Stirling Stove Fan
« on: June 20, 2019, 08:45:57 PM »
So, some time ago I added the subject casting kit (from myersengines.com) to a Christmas list...then pretty sure I deleted it as a) we no longer have a wood stove, and b) it's pretty big, too big for most of the required machining to be done on my mini-mill.  Also, it's been a busy year what with getting the youngest through school and all his concerts and shows and...well anyhow, it's been busy.

The youngest and I also have been planning a canoe trip, one last big outing for ourselves before he goes off to college -- something I did with his 3 brothers as they got older.  Part of that was finding all the camping gear and getting it in working order.  The old Coleman single-mantle gas lantern needed a new globe, so off to Amazon to order one...which of course was the wrong size. :Doh:

Meanwhile SWMBO apparently thinks I spend too much time behind a screen  :stickpoke: and dug the Stove Fan kit up off that old list and ordered me one.  So, on Father's day, I opened up the kit (see photo below) and was properly "thankful".  Now it's sitting in the office at work, while I contemplate the steps necessary to get it working.  At least one thing is going "right" - the wrong size lantern globe is the right size to use in this kit.    :shrug:

Hopefully I can get it built and working, and can test it out on the bbq or the wife's gas stovetop.  Then find somebody to gift it to...wish me luck!

Offline Ye-Ole Steam Dude

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Re: Myers Stirling Stove Fan
« Reply #1 on: June 20, 2019, 08:53:51 PM »
Hello Bent,

That is some good looking castings, are they aluminum or cast iron.

Have a great day,
Thomas

Online Jo

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Re: Myers Stirling Stove Fan
« Reply #2 on: June 20, 2019, 09:33:39 PM »
That looks a very desirable set of castings   :)

Jo
Enjoyment is more important than achievement.

Offline bent

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Re: Myers Stirling Stove Fan
« Reply #3 on: June 20, 2019, 11:13:35 PM »
Hi Thomas, they are aluminum.  Should be straightforward machining, but I need to think through the steps, how to clamp them, etc.

Jo, thanks.  A bit spendy, but it was the wife's money...ha ha.

Offline b.lindsey

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Re: Myers Stirling Stove Fan
« Reply #4 on: June 21, 2019, 02:01:48 AM »
Nice Bent. Myers usually does a pretty good job on their kits. Just study the drawings closely. I have found a few errors in other kits, though have no experience with the fan itself.

Bill

Offline bent

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Re: Myers Stirling Stove Fan
« Reply #5 on: June 21, 2019, 05:43:39 PM »
So far the drawings seem fairly straightforward, though the tolerances aren't given, so it will be a matter of figuring out what is critical and what ain't.  Castings (I'm checking the big pieces first) seem to be good, i.e. there is enough metal to cut back and form the necessary features.  I've got to figure out how to hold some of these things, without distorting the parts too much, and that's got me slowed down a bit...along with the fact that work and things like that continue to get in the way.  Maybe I should push up my retirement date, but do you think they'd let me still come in and borrow time on the drill-mill and rockwell lathe?  ::)

Offline b.lindsey

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Re: Myers Stirling Stove Fan
« Reply #6 on: June 21, 2019, 06:10:07 PM »
As for retirement, I love it but have had less shop time for numerous reasons. Hope that will change here shortly!!

Bill

Offline Dave Otto

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Re: Myers Stirling Stove Fan
« Reply #7 on: June 21, 2019, 07:18:51 PM »
I built the Essex fan from Myers casting a number of years ago. I didn't like the fact that it had an aluminum bore, so I sleeved it with a cast iron sleeve. I also sent the piston to High Performance Coatings and had them coat it with their SDF moly graphite coating.
https://hpcoatings.co.nz/services/advanced-engine-coatings/#sdf

It has always been a great runner. Looking forward to seeing progress on your fan.

Dave

Offline Ye-Ole Steam Dude

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Re: Myers Stirling Stove Fan
« Reply #8 on: June 21, 2019, 07:45:05 PM »
 Maybe I should push up my retirement date, but do you think they'd let me still come in and borrow time on the drill-mill and rockwell lathe?  ::)

Hello Bent,

Sure they will, just tell them that you are doing all of this work for FREE :ROFL:

Have a great day,
Thomas

Offline bent

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Re: Myers Stirling Stove Fan
« Reply #9 on: June 24, 2019, 04:55:49 PM »
I was thinking of charging them a consultant's fee Thomas!  :D

Dave, this version of the fan has a DOM steel tube cylinder liner (to be press fit to the aluminum casting), and is mated to an aluminum piston.  I'm a little worried about differential expansion causing binding...but we'll see.  Can always go back and build a steel or stainless steel piston if it is an issue.

After dithering around thinking about milling the features on the base, I realized it would actually fit in the chuck on the Rockwell with the jaws reversed (photo #1).  That allowed me to bore all the internal features to size, and face the end of the part and the bolt pads (photo #2).  Then reversed (re-reversed? un-reversed?) the jaws and flipped the part over and clamping on the now machined i.d. surface, I very slowly (500 rpm or so) and carefully (light, .01-.02 deep cuts) machined the o.d. to size and made passes on the bottom face until it was cleaned up and nicely flat (photo #3).  All well and good, but the next operation was to machine the opposite face of the base flange, leaving a 0.300 flange width.  Flipped the part and chuck jaws again, and then shimmed behind the part to get the material exposure needed.  This setup felt a bit less secure than previous ones, so I put a live center in the tailstock and ran it down to secure the part a bit better (photo #4) and finish up the turning operations.  All that was left was to drill and tap 1/4-20 holes on the bolt pads...which is a good task for my mini-mill and its DRO's (someday we might put DRO's on the work machines... ::)).

Photo #5 is the base part fully turned, and sitting next to the next-biggest, and flimsier, skirting piece that fits atop the base.  May have a go at that today (Monday) if time and other tasks allow.  The skirt seems to be just a cosmetic feature, so if I bung it up, no harm?

Photo #6 is from Saturday, dialing in on the center of the i.d. bore with a center finder and the DRO.  Drilling and tapping was a snap (love the spiral flute tap for aluminum, photo #7) and the mill made short work of the bolt pattern - completed part in photo #8).  Even being interrupted halfway through by SWMBO (had a graduation party to go to), and losing the zero for the DRO's, it was still straightforward.

A satisfying day's work, spread over a couple of days.

Offline b.lindsey

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Re: Myers Stirling Stove Fan
« Reply #10 on: June 24, 2019, 10:34:07 PM »
Off to a great start Bent!! Looking good so far.

Bill

Offline Ian S C

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Re: Myers Stirling Stove Fan
« Reply #11 on: June 25, 2019, 03:52:53 AM »
Bent, the best material for a piston in a steel bore would be cast iron, steer clear of aluminium unless  it's got something like PTFE rings on it. What ever Stirling Engine you build you should always be on the look out for ways of reducing friction, happy is the day when you have to introduce some load to slow things down.
Ian S C

Offline b.lindsey

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Re: Myers Stirling Stove Fan
« Reply #12 on: June 25, 2019, 02:27:15 PM »
You might also consider a graphite piston if you can source the material....self lubricating and thermally stable.

Bill

Offline bent

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Re: Myers Stirling Stove Fan
« Reply #13 on: June 25, 2019, 06:06:49 PM »
Thanks for the advice gentlemen.  Will probably try sourcing either grey iron bar or some graphite, if the piston proves any trouble.

Yesterday's efforts went towards the base skirt/shroud piece.  Once again chucked the part in the lathe (Photo #1), with the intention of scratching the i.d. opening on the surface of the casting, then cleaning it up on the mill.  But (being a lazy engineer at heart and in body) decided it was probably about the same amount of time to just take slow, small cuts on the lathe to clean up the chewed i.d. to form a smooth bore (photo #2).

With the i.d bored to size, reversed the part and found some shim washers to move the inside face out enough to make a skim cut and smooth it up (photo #3).  Then machined the face and end of the part, and cut a step to mate to the base piece made yesterday (photo #4 - trial fit, had to make a couple of adjustments from there...).  Took the part home last night to get the bolt pattern done, but we had a birthday dinner for one of the boys, so at home it sits.

Next...the tricky parts.  If I can figure out how to jig them up.

Offline Ye-Ole Steam Dude

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Re: Myers Stirling Stove Fan
« Reply #14 on: June 25, 2019, 06:47:40 PM »
Hello Bent,

Looking real good and some nice machine work.

Have a great day,
Thomas