# Brian does Popcorn



## Brian Rupnow (Sep 30, 2011)

I have been playing about all week modelling Stew Harts Popcorn engine. Stew kindly sent me a package of 2D drawings that he had created, and it looked so interesting that I promptly set about modelling it in 3D. I discovered a couple of missing dimensions, and informed Stew, and as I modelled it I kept Stews metric dimensions for everything except the fasteners and the shaft sizes. ----and the piston diameter----And the bore of the crosshead guide. Those I converted to the closest British Imperial sizes. I have no desire to start a thread that competes with the fine work Stew is doing, but I thought that probably interested model machinists might want to see what the engine looked like as a 3D model. There was no base drawing in the package received, so I "Made one up" that would do the job. If any of you CAD guys out there want a copy I have saved these files as.xt and .iges. and as .step files and can post a link to a download.---Brian


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## Brian Rupnow (Sep 30, 2011)

And a couple more shots. I may make detail drawings of this stuff at some point in the future using British Imperial units instead of metric units, and if anyone is interested then answer this thread and you will receive any updates when I do. For now though, I am not going to post anything more untill Stews build is finished.


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## kjk (Sep 30, 2011)

Count me in Brian.


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## Captain Jerry (Sep 30, 2011)

Brian

I would like to have a copy please. I downloaded your .iges file this morning and Alibre' opened it just fine but of course there is no part detail. I would really like to play with the parts.

Jerry


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## Brian Rupnow (Sep 30, 2011)

If I've done this correctly, this should get you a download in .igs format
http://www.mediafire.com/?1v5u97zu457g93u


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## Brian Rupnow (Sep 30, 2011)

This will get you .step files
http://www.mediafire.com/?bhwtyoq1lj10xzf


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## Brian Rupnow (Sep 30, 2011)

And this should get you parasolid .xt files.
http://www.mediafire.com/?gcvpdka9eno5z77


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## Brian Rupnow (Sep 30, 2011)

And there's nothing like being able to see it run before its even built!!!


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## SBWHART (Oct 1, 2011)

Thats a great Job Brian :bow: :bow:

Stew


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## Captain Jerry (Oct 1, 2011)

Brian

Thanks for making these files available. I have imported the .step files in Alibre' and the parts are individually accessible. Two parts show up as wire frame only, the "valve rod guide" and the "crankshaft". Do you think that this is a failure of the Alibre" import translation or were these parts different in some way when you created the file?


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## rleete (Oct 1, 2011)

I'd be interested in an imperial unit conversion. Also, if they are SolidWorks files, can you make the originals available?


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## Brian Rupnow (Oct 1, 2011)

Captain Jerry  said:
			
		

> Brian
> 
> Thanks for making these files available. I have imported the .step files in Alibre' and the parts are individually accessible. Two parts show up as wire frame only, the "valve rod guide" and the "crankshaft". Do you think that this is a failure of the Alibre" import translation or were these parts different in some way when you created the file?


Jerry---I don't know why those two parts don't import properly. There is nothing different about either of them. Perhaps you could try importing the .xt files or the .igs files.


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## Brian Rupnow (Oct 1, 2011)

rleete  said:
			
		

> I'd be interested in an imperial unit conversion. Also, if they are SolidWorks files, can you make the originals available?



This link should get you all the files in Solidworks 2011.
http://www.mediafire.com/?0tj0wm289gkbv89


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## rleete (Oct 1, 2011)

Thank you so much. I know how much hard work goes into making these models - I do it for a living, too.

Suffice to say that making these available to the community is very much appreciated.


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## Brian Rupnow (Oct 5, 2011)

I'm trying to stay in the background here and not step all over Stew Harts thread. Out of boredom, more than anything else, I have started making details in British Imperial (inches) from my solid models, and modifying the models if I find any errors or logical changes while I detail. This happens more than most designers/design engineers will ever admit. Utmost care is taken during the modelling phase to enter all the math data correctly, because with 3D cad the detail drawings are generated by the model. However, while the drawings may be easily generated by the model, I choose to add any notes, and dimensions manually because the software will throw in "nonsense dimensions" that while accurate, are not the dimensions that a machinist would (or could) use.---And its while I am doing that that I sometimes see where changes should be made to the model. This is not a big deal, because when I go back and change the model, my software automatically updates the drawing and any changed dimensions. I have been building the parts as I detail them, and have accumulated a tidy little pile of parts. This is the first time I have made a double tapered connecting rod (It was surprisingly easy) and I made the steam chest from one solid part, rather than 2 or 3 parts soldered together like Stew chose to do. After using extreme care to turn the cam to the perfect size,( once its parted off the main chunk of material, you're pooched---there is no way to hold it if you need to turn it down farther.) I managed to screw it up and have it about 0.010" too large. I had a 3/4" reamer with which I had reamed the assembled eccentric strap, and it would have been a real pig to set up correctly and bore it larger. After trying unsucsesfully to "run it in" under power and lots of lubricating oil, I finally popped it apart and coated it with valve grinding compound, then let it run for 5 minutes, gradually tightening the bolts which hold the eccentric strap together. This fixed things in short order, so after a quick disassembly and a good wash in Varsol, it runs smooth as silk. So here I am, this far into the Popcorn build.---Brian


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## RonGinger (Oct 5, 2011)

I just tried to load Brians solidworks files into Alibre and it worked perfectly. Every part and all the assemblies were converted to Alibre native files.

Thanks Brian for sharing.


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## Brian Rupnow (Oct 5, 2011)

Ron---When you imported the parts into Alibre, can you access the features in a part or do they just come in as "dumb solids"?---Brian


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## RonGinger (Oct 5, 2011)

Ah darn, they are just imported STEP files and the only features are faces, edges and verticies

I can view assemblies, and rotate and displace them, but the constraints dont seem to hold- I was able to slide the flywheel off the shaft, or drag parts out of the assembly.

I can view all the parts. I can also make a drawing from a part, but no dimensions come up automatically, although I can manually place dimensions and they seem to be correct.

So, its one of those 'almost' cases. I really cannot take your work as a starting point to alter the model, but I could make drawing files of what you have.


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## Brian Rupnow (Oct 5, 2011)

Ron---I don't know how Alibre works, but in solidworks you can see in the feature tree whether or not things are "fixed" or "floating". If you import an assembly and the parts are not constrained, select the top item in the feature tree, hold down the "shift" button on your keyboard and select the last item in the feature tree. This will highlight all of the parts, and you should then be able to right click and select "fix" to constrain everything in its relationship to everything else in the assembly.


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## Captain Jerry (Oct 6, 2011)

Brian (and Alibre users)

I downloaded the sldprt files and imported into Alibre. The assembly and each of the parts were saved as Alibre native files. When the files are imported the individual parts show in the design tree as STEP files and as such, they carry a full description of the part as you saved them. They just don't show the construction history, no sketches. 

The parts can be modified by adding or cutting but the construction sketches cannot be stretched or bent.

They do not carry any of the assembly constraints. These can be added. I took a little time this morning (about an hour) to reassemble the various parts with constraints to allow animation. I dropped the valve cover so the slide valve motion is visible and I left the nuts and screws off because they are not needed for the animation and they slow it down slightly.

Click the animation on Screencast:


http://screencast.com/t/qB9qpiLZ2


Thanks for posting these files. Fun to play with.

Jerry


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## Brian Rupnow (Oct 6, 2011)

Jerry---Thats a great animation!!! ----3D modelling is like a giant magnet---It sucks you in and keeps you learning more as you use it because it is so fascinating. I've only been using 3D for 10 years, and of course it wasn't available when I started in engineering 46 years ago. My God, if it had been available back then, I can't even imagine what it would be capable of now.


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## SBWHART (Oct 6, 2011)

Jerry

Very impresive work, I'll have to get my head round this 3D stuff.

Stew


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## Captain Jerry (Oct 6, 2011)

Brian

Thanks for the kind words. All the more appreciated in light of your modeling mastery. 

Stew - After some initial frustration, the light will go on and you will enjoy the benefits. It is almost as much fun as machining metal and the cleanup is a lot easier.  Its also a way to work when the shop is too hot or too cold.

Jerry


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## Brian Rupnow (Oct 7, 2011)

My stockpile of British Imperial Popcorn parts is growing, and this morning I got to do something I had never done before. I machined the outer profile of the cylinder, which is only half round. This operation has always puzzled me, because you have a round part that obviously can not be turned on a lathe!!! Yesterday I studied Stew Harts post on making his cylinder, (Thank you Stew) and I assume that he must have one of those combination lathe and mills. after seeing his method, the light came on, and I proceeded to use the same method on my machinery. I machined the overall rectangular cross section shape from brass, but made it about 1/2" longer than the cylinder length, then drilled and reamed a 0.5" hole all the way through it in the correct place using my mill/drill. I then slid it over a 1/2" peice of cold rolled steel shaft, and cross drilled in that extra 1/2" of material for a 3/16" spring pin. Then it was taken to the lathe where one end of the cylinder was "faced" to ensure it was square to the bore.


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## Brian Rupnow (Oct 7, 2011)

I then set my rotary table with the 3 jaw chuck attached up on the mill table, and chucked up the 1/2" cold rolled rod. I centered the spindle over the center of the 1/2" rod, and using a 3/8" end mill I took about a zillion passes back and forth parallel to the centerline of the peice at full depth with spindle height locked. Each time I took a pass with the milling cutter from end to end, I would advance the rotary table about 5 or10 degrees, and repeat the passes with the milling cutter. The reason that I set the cutter at full depth and locked it is that when you first begin to cut, the tip of the cutter is just "kissing" the material, and its the turning of the rotary table that actualy presents more and more material to the cutter as the part revolves. This method worked amazingly well, and now I've done another 'New Thing' with my equipment.


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## SBWHART (Oct 7, 2011)

Nicely done Brian:- thats more or less what I did except I din't use a cross bar, I turned a 1/2" dia mandrell up and bolted the cylinder to that, and used a small fly cutter.











Ther's more than one way to skin a rabbit.

Stew


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## Brian Rupnow (Oct 7, 2011)

I've done something that might be considered "dumb" in some circles!!!! As I converted this engine from Metric to British Imperial, I carefully changed the bores to accomodate my 1/2" and 5/8" reamers. I changed all the fastener holes to suit my favourite #5-40 taps. I changed the non critical bores to correspond to my 3/4" drill instead of the 20mm Stew had used. I changed the radii on the cut-outs in the crosshead guide to suit my 5/8" ball nosed endmill. However, I went blithely along with Stews metric offset for the cam and actually built the cam. It was only today as I whittled away on the cylinder that I realized I hadn't changed the slotted steam passages to correspond to an Imperial sized endmill. I didn't want to remake the cam, and the cam offset has to interact correctly with the size and spacing of the steam passages in the cylinder. I agonized over just how to get around this issue, then said "To heck with it!!!" and went over to my toolshop and bought a 2mm and a 3mm endmill. So----When I get around to posting all the drawings with "Imperialized" dimensions----Anyone considering building the engine from these plans will have to pony up $10 for a couple of metric end mills. And I have to tell you---Its a damn ticklish job, making a slot the depth required with a 2mm endmill!!! I think I held my breath the entire time I was cutting the slots, but all went well.---Brian


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## doc1955 (Oct 7, 2011)

:big: :big:
I know what you mean hold your breath small end mills just need to many RPM's to do real well.

I don't think my flywheel for the Atkinson I'm working would work to well it is probably bigger then your whole motor will be. :big: :big:

Things are looking good Brian!


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## SBWHART (Oct 7, 2011)

Brian

If you change the steam ports the slide valve has to change to match, i can't do it just now but some time next week, I,ll post the imperial sizes.


Stew


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## kvom (Oct 8, 2011)

For those who don't have a dividing head or a horizontal rotab, there's a couple of other ways to get a half-round cylinder profile.

With a vertical rotab you can cut the profile with the side flutes of an endmill. This gives a radius at the ends of the profile, but a small endmill to finish and/or filing can square it up.

In Kozo's A3 book he shows mounting the cylinder on a lathe and using the carriage with a parting tool mounted sideways to act as a shaper.


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## Brian Rupnow (Oct 9, 2011)

Well, the fat lady hasn't sang yet, but we're a lot closer to a British Imperial (inch) Popcorn engine!!! I must say, those pretty little bearing stands are a pain in the butt to whittle out, and I have never built an engine with "glands" on the cylinder and steamchest before, but so far, things are going very well.


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## Harold Lee (Oct 9, 2011)

Wow Brian - That is sure looking good! Thm:
Can't wait to see it run...

Harold


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## Brian Rupnow (Oct 9, 2011)

The credit here mostly belongs to Stew Hart. Stew was going like gangbusters on his Metric build of this engine, then got slowed down by some family commitments. I have been slogging away on this build, converting mostly everything to decimal inches, and trying not to outpost Stew. I have yet to make the crosshead guide, which is a fairly complicated peice, and a base. I am rather torn as to what to do about the flywheel. I would like to do something fancy, perhaps a bit larger in diameter than what stew had originally posted in his plans, but I've actually been too busy to give it much thought as yet. I have a peice of 3/16" Lexan that I want to use for the steamchest cover. Every time I build one of these small cylinders, I am absolutely dazzled by how many set-ups and machining operations are involve with them------------And this time, none of my threaded fasteners break thru into the cylinder bore!!!


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## Brian Rupnow (Oct 9, 2011)

I am thinking of making a built up flywheel with 3/16" or 1/4" steel bent spokes. I would bend them somewhat similar to the spokes in Stews drawing, silver solder them into holes in an inner hub, and set the outer ends into cavities machined in the side of a bronze outer rim, with a 0.100 steel side cover plate screwed onto the side of the bronze to lock them in place.---still in the thinking stage.


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## Captain Jerry (Oct 9, 2011)

Brian - I did a little YouTube surfing for Cretors popcorn Engines and saw a number of examples of both models and restored originals. One of the things I noticed on them is the mounting of the flywheel between the bearing stands as on this one:

[ame]http://www.youtube.com/watch?v=44iFMcn-jB0[/ame]

None of them show how power was transmitted to the rest of the machinery but I would guess that there would be a belt drive pulley outboard of the bearing on the flywheel end of the shaft, probably for round belting.

When you get around to making the Xhead guide, be careful of the relationship between the end bore depth and the side cuts. I downloaded your 3D parts and spent some time looking at that part. In your model, the bore is VERY near to breaking through onto that nice visible curved face. I guess you will do the bore first and then mill the face with a ball end mill. Just be careful, I know how much it hurts to mess up when you're that far into the part and that curved face is one of the main eye attractors on that part.

You assembled parts are looking great. And as usual, fast. Nice work.

Jerry


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## SBWHART (Oct 9, 2011)

Kricky Brian you've realy steamed along with this, I recon between us we've now got enough parts to complete an engine.

Have you got any ideas for bells and whistles for the enigine, i've got a governor and stop valve sketched up, and ideas for a whistle and displacement lubricator more or less sorted, plus a little suprize to finish with :

 :big: :big: :big:

Stew


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## Brian Rupnow (Oct 9, 2011)

All I have at the moment is a variation on your curved spoke flywheel. I don't really plan on the bells and whistles approach, I'll leave that up to you Stew. I'm just aiming for a running engine. Jerry does have a good point about the flywheel being between the bearing supports. This leaves lots of access at the outer end of the crankshaft for a drive pulley to power some device. I like that idea. I haven't made a base yet, so I may move the flywheel inside. There will definitly be a cut-out in the base to clear the flywheel diameter----Possibly four stubby legs on the under side of the base as well because a 3 1/2" dia. flywheel will hang below the base.  Jerry---I had caught what you are talking about on the crosshead guide, so have altered it a bit to keep it from breaking through. As I said in an earlier post, it is not uncommon for me to create all of the models, then end up going back and "tweaking" them as I do the detail drawings and notice thngs being a bit "tight" in areas.---Brian


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## cfellows (Oct 9, 2011)

Brian Rupnow  said:
			
		

> I am thinking of making a built up flywheel with 3/16" or 1/4" steel bent spokes. I would bend them somewhat similar to the spokes in Stews drawing, silver solder them into holes in an inner hub, and set the outer ends into cavities machined in the side of a bronze outer rim, with a 0.100 steel side cover plate screwed onto the side of the bronze to lock them in place.---still in the thinking stage.



Brian, here's a brief pictorial on curved spoke flywheels built up by Find Hansen. The result is a right nice looking flywheel.






Chuck


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## Brian Rupnow (Oct 9, 2011)

Chuck--Linkee no workee---


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## doc1955 (Oct 9, 2011)

curved spoke flywheels built up by Find Hansen


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## tel (Oct 9, 2011)

Not unlike how I do 'em


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## JorgensenSteam (Oct 9, 2011)

It is a little hard to tell exactly how the power was taken off of some of these Cretors, but in one case, clearly a chain was used.

In a photo of different engine, perhaps shafts and gear drive?

It is also clear from the video above that the Cretors was not balanced very well.
I think a properly sized counterbalance weight in the crank disk would stop most of that horizontal motion.


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## Brian Rupnow (Oct 9, 2011)

Yes, I'm definitely liking it better with a 3.5" flywheel mounted between the bearing towers. There is just enough room for an eccentric with a hub off to one side and the flywheel between them. Tomorrow I will start posting drawings of everything. I have everything built now except for the base and the crosshead guide and the flywheel.


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## Brian Rupnow (Oct 10, 2011)

Okay---Here we go!!! These drawings are based on Stew Harts drawings of the Popcorn Engine. I have redone them so that 99% of the tooling required to build this engine is British Imperial "inch" measurement. The exception is the steam ports in the cylinder, for which you will need a 2mm and a 3mm endmill (preferably 2-flute). If many of the dimensions seem a bit "wonky" its because they are direct "hard" conversions from metric. I have built the parts from every drawing that I post here, except for the flywheel and the crosshead guide and the base. I will post these parts when I complete machining them, just to confirm that the parts do indeed match the detail drawings. The first two drawings are the bearing stands. Nothing to "trick" about them, but fussy little buggers to make, just the same. I managed to somehow screw up and make one of mine about .030" too short, so I will have to put a shim under it. There is far too much work in the darn thing to remake it!!! *I WILL BE POSTING A LINK TO DOWNLOAD ALL THESE DRAWINGS AS .PDF FILES WHEN MY ENGINE IS UP AND RUNNING.*


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## Brian Rupnow (Oct 10, 2011)

There is nothing too exotic about the steam chest. I made it from one solid chunk of brass, used a 1/8" drill in the 4 inside corners, then squared the inner corners up with a file after the fact.


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## Brian Rupnow (Oct 10, 2011)

The drawing of the steamchest cover calls for it to be made of brass, however I have made mine from a peice of 3/16" clear lexan because I want to see that valve working.


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## Brian Rupnow (Oct 10, 2011)

All of the linkage rods are pretty straightforewars stuff, all made from cold rolled steel rod. The only observation I have is that I need to buy a new #10-24 die, as mine seems to be almost too dull to cut---however that won't effect you.


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## Brian Rupnow (Oct 10, 2011)

The rear cylinder cover is exactly as per drawing, nothing unususal about it. The front cylinder is different than Stews, as I chose to use shcs in it to clear the crosshead guide.


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## Brian Rupnow (Oct 10, 2011)

Nothing to say about this little guy, other than be sure to hold that backing dimension tightly---It has to line up with the bore in the steamchest.


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## Brian Rupnow (Oct 10, 2011)

These two connectors for the valve rod were built exactly as per drawing, except I built the smallest one from steel because I had a peice of 1/4" square cold rolled stl. laying around.


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## Brian Rupnow (Oct 10, 2011)

I built the exxentric as per Stew Harts drawing, then figured out after the fact that it would be a LOT easier to adjust the valve timing with an offset hub and set-screw to let you access the set screw without having to remove the eccentric strap to do so, so thats how I made the drawing.


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## Brian Rupnow (Oct 10, 2011)

The eccentic strap--(two peice)


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## Brian Rupnow (Oct 10, 2011)

Nothing real exotic about the crankshaft, except that I siver soldered mine, while I think stew Loctited his together.


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## Brian Rupnow (Oct 10, 2011)

I made the crankshaft bearings from brass, exactly as you see them.


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## Brian Rupnow (Oct 10, 2011)

The two "glands" I made were made using 7/16" hex brass because I had some in stock. The drawing calls for 3/8" stock, which might look a little more to scale with the rest of the engine.


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## Brian Rupnow (Oct 10, 2011)

The cylinder---What can I say, except, Jeez!!! There's a lot of work in that thing!!!


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## Brian Rupnow (Oct 10, 2011)

Crosshead---Just as you see it---


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## Brian Rupnow (Oct 10, 2011)

The pin that connects the piston rod to the connecting rod.


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## Brian Rupnow (Oct 10, 2011)

The crosshead guide. I haven't made it yet, but it certainly looks like its going to be interesting!!!


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## Brian Rupnow (Oct 10, 2011)

The connecting rod. This was the first tapered con rod I have ever made, and it was far easier than I thought it would be. Stew Hart shows how it was done in his Popcorn thread.


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## Brian Rupnow (Oct 10, 2011)

And last but not least, the support that the cylinder sets on. Its kinda tricky, because there is an angle on all four sides.


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## Brian Rupnow (Oct 10, 2011)

Whoops!!! Forgot the main base!! I haven't built this yet.


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## SBWHART (Oct 10, 2011)

Great set of drawing Brian:- I've PM you about them

I don't know how your planning to do the cross head guide but if you're going to use the fixed steady method i used just a word of warning, check out the steady that it bolts down secure to the lathe bed, the steady that was suplied with my Chines lathe was a load of crap as suplied, in fact I would say it would have been dangerouse to use. I modified mine by bolting a chunk of ally across the base to make a wider more positive base with tapered pull ups, that fixed it securly to the lathe bed, can't post pictures of it at the moment.

Stew


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## Brian Rupnow (Oct 10, 2011)

I forgot these two guys.--I built them this afternoon after wife and I went out for a drive to see the autumn leaves. Wife had a nap, I played machinist. (Wife is far brighter than me!!!)


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## Brian Rupnow (Oct 10, 2011)

sbwhart  said:
			
		

> Great set of drawing Brian:- I've PM you about them
> 
> I don't know how your planning to do the cross head guide but if you're going to use the fixed steady method i used just a word of warning, check out the steady that it bolts down secure to the lathe bed, the steady that was suplied with my Chines lathe was a load of crap as suplied, in fact I would say it would have been dangerouse to use. I modified mine by bolting a chunk of ally across the base to make a wider more positive base with tapered pull ups, that fixed it securly to the lathe bed, can't post pictures of it at the moment.
> 
> Stew



My lathe will take up to 1 3/16" thru the spindle, so I SHOULD be okay to make the crosshead guide without having to use the steady rest. Thanks Stew, for the warning.----Brian


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## Brian Rupnow (Oct 11, 2011)

I spent a very entertaining day today, machining the crosshead guide. I started out with a 1 1/4" round peice of cold rolled steel, and I turned, and I drilled, and I bored, and I reamed, and, and, and. I actually got to use a couple of peices of kit that up untill today were primarily dust catchers. I have no idea why I bought such a huge height/marking out gauge. I must have thought I would be machining full sized locomotives when I bought the damn thing 3 years ago. The little V-block with clamp is a fairly new "impulse" buy that I bought 6 months ago on a trip to BusyBee Tools, looking for something else. I bought a new 5/8" ball nosed end mill to put the radii in the crosshead guide with, and it worked well, but I found it rather terrifying to use. I was taking a 0.276 deep cut from the side, feeding in about .015" at a time, and the THUMPA-THUMPA-THUMPA and vibration had me wondering if it wouldn't be a much better tool to use on a full size Bridgeport rather than my little Craftex unit.


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## Brian Rupnow (Oct 11, 2011)

I've gotten this far, with only one "gotcha". I have been warned numerous times about the folly of holding an end-mill in a chuck, but I have never found it to be a problem when cutting brass or aluminum. However, the crosshead guide is made of steel, and I had a BIG end mill in the chuck. As I was machining one side, it seemed that the mill was working harder, and harder and Oh Oh---the cut is getting deeper and deeper!!! Hit the kill switch, clear the chips, and Damn----the end mill came loose in the chuck and was dropping down farther and farther into the cut as I went along. Far too much work invested already to start over, so a quick trip out to the garage, fire up the mig, and weld up the ever deepening cut. Then 20 minutes of file work. Now nobody will ever know but us!!! Tomorrow I will endevour to but that humungous 0.787" radius in the last side to be cut away (Not exactly sure yet just how I'm going to do that) and the crosshead guide will be finished.


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## kvom (Oct 12, 2011)

Good work so far. Maybe the radius cut can be set to .75 and just use a 3/4 endmill. The endmill in a chuck for milling problem is a good lesson to learn (of course, a chuck CAN be used when drilling/boring with an endmill).

In looking at the plans, it seemed to me that the valve gland could be lengthened enough so that the little support piece wouldn't be needed, and then getting the support's height exactly would no longer be a problem.


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## Brian Rupnow (Oct 12, 2011)

Kvom---a 3/4" endmill cuts a 3/8" radius.


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## SBWHART (Oct 12, 2011)

kvom  said:
			
		

> In looking at the plans, it seemed to me that the valve gland could be lengthened enough so that the little support piece wouldn't be needed, and then getting the support's height exactly would no longer be a problem.



This is not always a part of the full size engine so I guess yoy could miss it out but I figured it added an intersting feature.

Stew


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## kvom (Oct 12, 2011)

Brian Rupnow  said:
			
		

> Kvom---a 3/4" endmill cuts a 3/8" radius.



oops, my bad.  :-[


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## Brian Rupnow (Oct 12, 2011)

Today, I had to build a part to finish a part. The crosshead guide for the popcorn engine is one of the trickiest parts I have built so far in my machining hobby. The first two cuts were accomplished without too much difficulty, but the last cut with that 0.787" (20mm) radius had me worried. I finally decided to cut it with the boring head in the mill. In order to do this I had to machine a holding fixture from aluminum and bolt the semi finished crosshead to it. The largest part of the cut-away was accomplished with the bandsaw, but even for that the part needed to be held in some type of fixture. I am very pleased with the results, and will post a picture if I can. Photobucket is being very oinky tonite for some reason. My digital pictures are not as focused as I would have liked, but they will suffice to show the boring operation, the fixture block I had to make, and the finished part. All I need to do now is spend some quality time with a bit of emery cloth and I will be able to move on to making the base. I still haven't done anything about a flywheel, but that is the only part remaining to be made, other than the base.


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## Brian Rupnow (Oct 12, 2011)

This is a couple of shots of the completed part still bolted to the fixture block.


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## Brian Rupnow (Oct 12, 2011)

And here is the finished part, just waiting for some final sanding and de-burring.


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## SBWHART (Oct 13, 2011)

Thats a neat way to finish off that radius Brian, never thought of using a boring bar.

Stew


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## Brian Rupnow (Oct 13, 2011)

Thanks stew. I don't always get consistent results with a file----seem to have a hard time keeping things level. It certainly is an aquired skill!!! Here is a drawing of the four feet that go beneath the main base. Since I am using a larger diameter flywheel, it actually hangs below the base a bit.


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## Brian Rupnow (Oct 13, 2011)

Well, I have a great lot of parts!!! Most are finished, some "semi-finished". I just whittled out the base this afternoon, but it needs a fair bit of sanding and de-burring yet. I haven't done any more with the crosshead guide. All I lack now is a piston, a flywheel, and the four feet to go on the bottom of the base. This will be a nice little engine, but I wish I hadn't built two engines so close together. I'm finding this one more of a chore than the Overcrank single, not because its any more difficult, simply because I do better if I wait about 3 or 4 months between builds.


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## steamer (Oct 13, 2011)

Looking good Brian!

Dave


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## Brian Rupnow (Oct 14, 2011)

Could this possibly be the last drawing? I got up this morning and made the four "feet" that go on the bottom of the main base, then realized that I had enough 5/8" dia. stock left to make a piston. Then i realized that I hadn't yet made a drawing of the piston. So---Here it is.


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## Brian Rupnow (Oct 14, 2011)

I had to make this drawing to establish all of the correct set-up lengths for my linkages, so will include it in the complete set. I am going to lose my computer for a week or two, as I have taken a short term engineering contract where I absolutely MUST be "on site" along with my mega computer that hosts my solidworks. My crummy little lap-top is about 6 years old and is way underpowered to run Solidworks on now. I will save all my current popcorn drawings as .pdf files and put them on a disc so that I have access to them on the laptop while my big computer is away. I don't like to do this, but after a wonderfull summer of "Fun in the Sun and no work" I have to do something to refill the kitty!!!


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## Brian Rupnow (Oct 15, 2011)

Gentlemen--We have a runner!!! I spent the day fitting my pile of Popcorn parts together, and a long, tedious day it was. Both my 10-24 die and my 5-40 die were so dull that I had to buy new ones and rethread everything. Then I managed to break the 1/8" dia. control rod off flush with the surface of the eccentric strap. However, luck was with me and I was able to drill it out, rethread, and save the part. When I set the cam I followed Elmer Verburgs instuctions---Set the piston at either top or bottom dead center, and set the valve exactly in the center of its travel. After assembly, the engine was very stiff, but after an hour of "running in" with my electric drill motor, it freed up considerably. I wanted badly to try the engine out, but haven't yet built a flywheel for it, so I robbed a flywheel off of the Chucks Hit and Miss Air Engine that I built two or three years ago, as it was close to the right diameter and width. I had to open the bore up from 1/4" to 5/16" and machine about .040" off the width. I plugged the air in and opened the valve, and to my great pleasure the engine started immediately and has been running in my basement for the last two hours. I will be building a "fancy" flywheel for it, but that will be sometime in the next two weeks. I'm posting this from my wifes laptop computer, because my big computer is temporarily across town at an industrial plant where I am working a temporary engineering/design contract.


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## ShedBoy (Oct 15, 2011)

Nice runner Brian, well done Thm:
Brock


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## GailInNM (Oct 15, 2011)

Thm: Thm:
Gail in NM


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## RonGinger (Oct 15, 2011)

Very nice work Brian, and very nice of you to share it with all of us.

I have one nit to pick. You refer to adjusting the cam. In steam engine terms its called an eccentric. I know it acts like a mechanical cam, but in all steam terminology its called an eccentric.

Whatever you want to call it, its still very nice work.


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## Tarheel (Oct 15, 2011)

Thanks for another great design. Anxious to build this one.

Larry


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## Brian Rupnow (Oct 16, 2011)

If anyone wants to go ahead with this build, all of the posted drawings are correct. I will be adding a pdf download file later this week, because I don't know how well the .jpeg files I have posted will print out. One warning though---This engine is not for "newbee" machinists. Thre is a lot of complex and finicky work in that crosshead guide, and it is really the main showpeice of this engine. ---Brian


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## maverick (Oct 16, 2011)

Wonderful engine Brian. Thanks to both You and Stew for the development and great drawings.
 I've fancied the Cretors version for a long time and now have good incentive to build one.

 Regards,
 Mike


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## danstir (Oct 17, 2011)

Really nice engine. Thanks for sharing the build and the plans!!


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## Brian Rupnow (Oct 18, 2011)

Not having my big computer at home is making me a bit crazy!!! I have come up with a really nice way to make a built up flywheel, and although I have modelled it in 3D, I have no way currently to post it. I have been going in to work a bit early each morning and pulled detail drawings off the model so that I can proceed with the build in the evenings, and so far I have completed the two part outer rim (in bronze) and the hub (in brass). Although I have brass here to make the spokes from, I might get radical and make the spokes from aluminum for the contrast. Since no soldering is required, this is an easy thing to do. My spokes will not be bent like the ones pictured in the drawing of the engine, but will be tapered----large at the hub and small at the outer rim. Not great from an engineering standpoint, but it looks slick!!! I think that when I get my computer back next week, I may start a seperate thread on the building of the flywheel. It feels realy weird after 10 years to be going across town to someone elses factory to do my thing, but its an interesting project. The company I am doing the design work for makes metal spinning lathes for industry, and I am helping design the automatic feed and part removal system for a large new metal spinning lathe.


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## kvom (Oct 19, 2011)

Can you post an STL file for the flywheel? I don't have SW but might try to CNC mill it.


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## kjk (Oct 19, 2011)

Pat Joorgensen (BigonSteam) and I have been corresponding on a couple of engines, including a Cretors. I use Alibre, and Pat uses both SW and Alibre. The problem with Alibre is that while it can export STL, it cannot import it (at least my version can't). I can export the STL but I can't examine the output to see if it is smooth enough. 

There are some parameters in Alibre which determine the quality of the STL it outputs, but since I can't see the effect they have, I just aimed fairly high. The result is over 45mb and so I put it here: http://www.mediafire.com/?6b9pqobciw4jjk5

Please post to let us know if it will work out for cnc.


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## kvom (Oct 19, 2011)

I was able to load the STL file into CamBam, but as I have not previously tried any 3D milling I am not sure how to generate the g-code. I posted a thread over at the CB forum asking for advice. Since CB wants to mill surfaces, I suspect that the file it needs would have just the spokes and the inner rim as a separate surface from the rim, and also not to have the hole in the center. The actual rim would be turned on the lathe or milled 2.5D.

I'll report back when I have some idea how this needs to go, but in a different thread so as not to hijack Brian's build further.


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## Brian Rupnow (Oct 19, 2011)

This is the flywheel I am building for the Popcorn engine. I have started a seperate thread for it, titled "Built up Flywheel-2011".


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## Brian Rupnow (Oct 20, 2011)

As promised, here are all the files required to build the "inch" version of the Popcorn engine. You will have to buy two metric 2-flute end mills, a 2mm and a 3mm to machine the steam ports in the cylinder. I have not included the plans for the flywheel because it is still a "work in progress". The flywheel is 3.5" o.d. x 1/2" wide with a 5/16" center hole. Stew Hart did the original metric design of this engine, and I took Stew's drawings and bastardized them into British Imperial, with a few changes but not many. If you download and/or use these files please give me a Karma point-----and give Stew Hart one as well, because without Stew firing my imagination and posting the original metric plans, this wouldn't have happened.---Brian

http://www.mediafire.com/?akf34e4hcok5i04


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## jpeter (Oct 20, 2011)

I'd like to see a short straight section on the spoke where it exits the hub. I think the taper to the end would make it hard to fit the spoke in the hub without showing a gap. Some flutes in the spokes would maybe add a nice touch too.


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## Tarheel (Oct 20, 2011)

Brian-

These files are for the OVERCRANK engine which I already have.

Larry


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## hopeless (Oct 21, 2011)

Brian I have given you a karma point for your overcrank which I am halfway to finishing (don't get too excited a lot of my stuff gets to that point :big so am looking forwards to this project as well. :bow: Stew is in line for a point too ;D
Pete


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## Brian Rupnow (Oct 21, 2011)

Tarheel  said:
			
		

> Brian-
> 
> These files are for the OVERCRANK engine which I already have.
> 
> Larry



Terribly sorry about that.---My Bad!!! Link has been corrected.--Brian


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## Tarheel (Oct 21, 2011)

Thanks Brian. Just printed them out.

Larry


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## Brian Rupnow (Oct 21, 2011)

If anyone is crazy enough to want to build this multi part flywheel, I have posted .pdf files with the posted drawings over on the "built-up Flywheel--2011" thread.


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## Brian Rupnow (Oct 22, 2011)

I just finished the flywheel for this engine, and I really like it.


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## Brian Rupnow (Oct 22, 2011)

And here we have the engine with the new flywheel on it.---Video to follow---


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## Brian Rupnow (Oct 22, 2011)

Allright Boys!!!---we're done like dinner!!!


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## lazylathe (Oct 22, 2011)

Another great runner Brian!!!

Like the lexan cover on the valve chest.
A neat idea so that you can see what is going on in a usually closed environment.

Now you just need to build a 1/3 scale popcorn vending machine!!! ;D

Andrew


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