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Brian does Popcorn

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Brian Rupnow

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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

 

Brian Rupnow

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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.

 

Captain Jerry

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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
 

SBWHART

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Thats a great Job Brian :bow: :bow:

Stew
 

Captain Jerry

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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?
 

rleete

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

Brian Rupnow

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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.
 

rleete

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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.
 

Brian Rupnow

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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
 

RonGinger

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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.
 

Brian Rupnow

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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
 

RonGinger

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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.
 

Brian Rupnow

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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.
 

Captain Jerry

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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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