Original Green Twin Oscillator (drawings by PatJ)

[GreenTwin]

This is the flywheel that is on my green twin (shown in the photo above).

It had a few sand inclusions because I used Petrobond with iron instead of resin-bound sand, but I was able to repair them.

Nice clean metal inside, no hard spots or internal voids, and easy to machine.

I got lucky on this flywheel.
This was literally my first gray iron casting.
It took me quite a few more years to be able to consistently cast high-quality gray iron parts, especially thin parts.

 

[Donrecardo]

More green twin drawings by PatJ.

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View attachment 138422View attachment 138423View attachment 138424View attachment 138425View attachment 138426View attachment 138427

Love the engine and have downloaded the images from this post and the earlier one . I notice ther are two identical pics GT-01 but no pic GT-10 , Should there be ?
Don

 

[GreenTwin]

Don-

Thanks for pointing that out.
I also noticed that I plotted the sheets at a 1.023 scale, not a 1:1 scale, so I have replotted and reloaded all of the green twin drawings, and added sheet 10.

The revised drawing file date is 07-16-22, and those drawings are exactly 1:1.

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[Donrecardo]

Don-

Thanks for pointing that out.
I also noticed that I plotted the sheets at a 1.023 scale, not a 1:1 scale, so I have replotted and reloaded all of the green twin drawings, and added sheet 10.

The revised drawing file date is 07-16-22, and those drawings are exactly 1:1.

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Thats great thank you . will download them now
Don

 

[David Shealey]

WOW! That is really nice work. My first thought was "The base pattern was more work than the rest of the engine!" I may try that engine one day but I would either machine all from raw stock, or 3D print the base pattern. I would likely print multiple pieces and glue them together. It could be printed one piece, but supports would be needed, and getting supports off cleanly is a real task.

 

[GreenTwin]

The base can be 3D printed upsidedown without supports if you print the bottom flange separately.

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[David Shealey]

The base can be 3D printed upsidedown without supports if you print the bottom flange separately.

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I only have FDM printing capabilities, so if that process is used the bearing support protrusions would have to be seperate items to get a flat surface on the build plate, but alignment pockets for the seperate protrusions would be an issue. An option would be an alighment jig to hold the protrusions in place for bonding. But this could be printed one piece by sending it out to a printing house using HP MFJ printers. I had parts printed that way in my last job, now retired.

 

[GreenTwin]

Looking back at the green twin build photos, we used a variety of methods for the patterns for this engine.
At the time, I did not have a good or reliable 3D printer, so the flywheel was sent out to a professional 3D printing company for a 3D printed pattern.
My buddy in Canada had assess to 3D printers at his local maker's space, and so he 3D printed some of the patterns, which he mailed to me.
And I ended up making some of the patterns out of wood, steel, etc.

These days, I have pretty much gone to all 3D printed patterns, just to save time and effort.

The quality of 3D printers has really improved these days, and Prusa's will recover from a broken filament, power outage, etc.

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