Author Topic: Myers Stirling Stove Fan  (Read 2110 times)

Offline bent

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Re: Myers Stirling Stove Fan
« Reply #15 on: June 25, 2019, 08:13:33 PM »
Thanks Thomas!

One thing I must say - these castings are of very good quality, both in the soundness/lack of material porosity (knock wood, haven't hit any yet) but also in the dimensional quality - faces are reasonably parallel across the parts (no pattern shift or float/tilt) and bores concentric.  There is one part coming up that has some weirdness, but in areas where it won't matter (they get machined away).  I do sit and stare at that part and wonder how the heck they made the core and pattern...will post photos of it when I get to that step.

Offline bent

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Re: Myers Stirling Stove Fan
« Reply #16 on: October 08, 2019, 04:39:27 PM »
Man have I been busy...or lazy.  Quick update - took the time to locate the base cover on the mini mill at home, leaving enough room between clamps to "touch off" on the machined i.d. and find true center, then bored 9/32 thru, replaced drill with 1/2" endmill and spotfaced the holes (photo below).  It's so much easier to use DRO's for bolt patterns, I'm really glad I installed them.  Oh, and I need to invest in more 3/8" nuts, had to use some spare t-nuts to get the clamping done. :embarassed:

I've also ordered and received a nice little 2" boring head that will let me do some of the more complicated boring tasks at home...but in contemplating (fondling?) the castings realized that two of them need work done on the large lathe at work (because it has a larger chuck), and the drill/mill because it has the required headroom.  But work has been busy, with me being a machinist to make assembly jigs and tooling for a new product, and then doing some R+D...and more to do today...

So maybe later this week I can get some more done?  Will see.

Online b.lindsey

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Re: Myers Stirling Stove Fan
« Reply #17 on: October 08, 2019, 08:05:30 PM »
You are making more progress than me lately and I don't have the excuse of W*** now. At least it's nice to have the machines at work when you need them though.

Bill

Offline bent

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Re: Myers Stirling Stove Fan
« Reply #18 on: October 16, 2019, 07:46:55 PM »
A bit more done, once again using the work mill and lathe due to lack of headroom and/or swing on the home machines.  The upper piston housing needs to have the i.d. bored, so set it up on some blocks and used a 3" boring head to turn the i.d. (photo 1).  Had to use the side hole of the boring head to get to the 4.3" i.d., which means I couldn't clean up the bore all the way to the bottom.  Will either need to hand work this bit, or just adjust the displacer piston to fit, will decide that later.  After getting a reasonably square/true i.d. datum, I could chuck the part and turn the o.d. of the flange to remove the unsightly casting gate (photo 2 and 3).  Now that good datums have been established, this part will go back to the home mill to get a bolt pattern put in using the dro's, and then bore the power cylinder and displacer piston rod hole.

Photo 4 is just me contemplating the next tricky part - the piece that holds the fan and crankshaft.  Somehow I need to bore out all of the internal casting so the part will fit on top of the piston housing.  Not gonna fit on the lathe, so will need to dream up a jig and means of clamping for the drill-mill.  Hmm... :headscratch:


Offline crueby

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Re: Myers Stirling Stove Fan
« Reply #19 on: October 16, 2019, 08:05:54 PM »
Thats a pretty intricate part, looks more like the trim on an old Dusenberg or something!

 :popcorn: :popcorn: :popcorn:

Offline bent

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Re: Myers Stirling Stove Fan
« Reply #20 on: October 16, 2019, 10:21:51 PM »
I know what you mean, Crueby!  Some days I just sit and look at it and marvel at the person who carved (?) the original pattern, then at the foundry man who figured out how to cast it.

Offline bent

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Re: Myers Stirling Stove Fan
« Reply #21 on: October 17, 2019, 11:45:28 PM »
Well, I decided to jump in and get the fancy standard part started.  After thinking and kicking around ideas with a colleague, I decided to cut a piece of 4" steel pipe we had lying around at work, as it seems to make a fairly snug fit to the part's i.d.  Squared off the end with careful cuts on the lathe yesterday, and tested the fit (photo #1) .

Just needed a notch at the crank shaft end, right?  Yeah, no.  (photo 2).  The fins appear to have warped inwards as they cooled from the casting...or the i.d. of the part is actually tapered along the axis?  Ah, whatever.  Added a strip of polyethylene, and made a c-clamp shoe to fit over the external rib (and a pocket to center the c-clamp swivel end), and voila' (photo 3).  Kinda rickety looking, but it held up well to the shake test, and a couple of whacks with a bit of 2x4.

So, rough-planed the end where it will mate to the piston housing, then shimmed the part in its clamps to get it a bit more square and somewhat even around the rim (photo 4).  The other mickey mouse bit is shown in photo 5, an o-ring was used to stop the c-clamp handle from rattling around during the milling (annoying as all get out until I "fixed" it!).  Finally, in photo 6 you see I've made some marks for the flange and roughed out the center.  Next to bore through the flange with a boring head and make it more circular and sized to fit the piston housing...after finding the center of the rim with a mill with no dro's and really sloppy handwheels... :insane:


Offline bent

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Re: Myers Stirling Stove Fan
« Reply #22 on: October 23, 2019, 11:46:31 PM »
Okay, a bit further along.  After I finished boring out the i.d. of the standard piece flange, the next step was to bore an offset "notch" to allow clearance for the piston housing boss that the standard bolts onto.  Photo 1 below shows milling a R1.40 radius notch at about a 1.25 offset from center (dialed in by the handle markings on the drill mill, so those numbers are probably +/- .020 or so, but not critical.  Though I did need to open up the measurements after eyeball fitting the two pieces, and realizing the castings run out a bit more than the drawings show (drawing calls for R1.15 at 1.18 offset, a fair bit of difference. 

The fit was checked by eye (photo 2), which wasn't exactly the best method...the center part of the flange interferes with the cast "fin" running down the back side of the piston boss and the parts can't be mated flange-to-flange until that gets cut out (photo 3). 

But the drawing has a note about removing that material should wait "until all other machining is finished".  Hmph.  No way to clamp the parts and transfer punch the bolt hole pattern until the cut is made, and I can't dial in the bolt pattern very reliably with the dials on the drill mill (and part won't fit on the mini mill with its DROs at home).  Phooey, 4 drilled holes and then the rest of the machining at the opposite end of the part which will require a completely different workholding setup, so off to the bandsaw and zipped out the interfering piece.  (photo 4)

Tomorrow, perhaps I will get the bolt holes set up and do a bit more pondering on how to finish the displacer piston bore...I'm thinking I need a fly cutter to be able to mill the bore down flush to the cast bottom...or else come up with a 1/2" boring bar with a 1/2" or so offset.  Probably about time for a family shot then as well, once all the parts go home again.

« Last Edit: October 23, 2019, 11:52:14 PM by bent »

Online b.lindsey

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Re: Myers Stirling Stove Fan
« Reply #23 on: October 24, 2019, 01:08:20 AM »
Nice work on that very tricky standard Bent. You are making nice progress on this project :ThumbsUp:

Bill

Offline Dave Otto

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Re: Myers Stirling Stove Fan
« Reply #24 on: October 24, 2019, 01:08:51 AM »
Lots of tedious work in that part, its coming along nicely though!

Dave

Offline bent

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Re: Myers Stirling Stove Fan
« Reply #25 on: October 24, 2019, 04:55:49 PM »
Thanks Bill.  Dave: Tedious, yes.  One of the more puzzling things I've tried to machine.

But that's the fun, too, figuring out the 3d puzzle of how to get a working end product.  I did realize yesterday that, after getting the machining on the flimsy pieces all done, I might be able to bolt the two parts together, and then turn the o.d. of the standard to better match the piston housing (it's overhanging the housing right now about 50 or 60 thou and really rough looking).  We'll see.

Off to do some more R+D and a hydrotest on a new production casting, so probably a couple more days before any new progress gets made.  I also need to do some shopping for bearings and a piece of cast iron for the piston.  The drawings call for double-shielded bearings (to keep the dust out I suppose?), but I worry those will have a lot of friction drag (and be packed full of sticky grease) and hurt the performance.  If I soak them in solvent and then in a light machine oil, will they do ok, or should I opt for unshielded bearings that are either ungreased or lightly oiled?

Offline Dave Otto

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Re: Myers Stirling Stove Fan
« Reply #26 on: October 24, 2019, 05:33:49 PM »
I would go with the unshielded bearings and light oil.
I will post some pictures later today of how I did the bearings on my Essex; which I'm pretty sure is the same design as the stove fan. What I did is not to the plans but I'm pleased with how it worked out.

Dave

Offline bent

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Re: Myers Stirling Stove Fan
« Reply #27 on: October 24, 2019, 10:36:45 PM »
Thanks Dave, I'll probably go with unshielded bearings too.

Offline Dave Otto

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Re: Myers Stirling Stove Fan
« Reply #28 on: October 24, 2019, 11:58:36 PM »
Hi Bent, Attached are a few pictures.

I had forgotten that the bearing shields were part of the original plans; I thought that I had added them; you can see one of them in the picture of the unpainted fan.
What I did add was the front bearing shield and the oil holes. The front shield is captured between the fan hub and inner race of the bearing, it spins along with the crank and fan hub.
In the picture of the original fan you can just make out the oil holes in the bearing housings. On the back end, the crank disk is so close the casting I didn't bother with a shield there.

Dave

Offline bent

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Re: Myers Stirling Stove Fan
« Reply #29 on: October 25, 2019, 04:38:11 PM »
That seems a pretty good solution, Dave, and I was thinking the same thing (externally mounted shields).  The oil holes are a good thought too.  Did you just make a weep groove for the oil to wash down to the bearings, or does the outer bearing race have an oil passage?