Bob J's No.21 Steam Engine (drawings and STP files by Pat J)

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GreenTwin

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My dad scratch built a nice little single-cylinder oscillator many years ago.

It is a relatively simple design, but looks nice, and so I thought I would post it here for those who may want to build it.







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In the process of documenting this engine, I mapped out what the difference was between the 2D program I had been using with my new 3D parametric design program (Solidworks).

Sometimes you have to put things on paper to be better able to understand the process.

The drawings I made for this engine in 2D CAD are not related to each other dynamically, and so if a change is made to one part in 2D, one must be very careful to update every view of that same part, and also one must update any part that mates with the part you changed.

With 3D modeling, if I change a part, all of the views of the part in the 2D drawings automatically update to reflect that change, and by viewing the assembly, I can tell how the changes affect mating parts.

Everything in 3D modeling emenates from the 3D models of the individual parts, including the Bill of Material, the Exploded View, the 2D drawings, the motion study, etc. Any change in any model is automatically and dynamically changed in every other entity, most importantly in the 2D drawings.

3D modeling is a quantum leap in design power, and I have likened it as ranking in importance in the design world to things like the creation of the wheel, or the creations of computers themself.

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Here are my 2D drawings for my Dad's No.21 steam engine.

These drawings are laid out for a barstock build.
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A few more drawings for my Dad's No.21 steam engine.
 

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I also used this engine design to try my first 3D printed part.
I ended up filling the frame print, to give the surface a convex shape, and keep it from looking so flat and plain.

This was my No.21 frame pattern.

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And I decided to build a foundry in 2011, and this was one of the first items I tried to cast in 356 aluminum.

This was a very crude attempt at casting an engine part, but considering it was about the 3rd item I had ever cast, it turned out pretty well in my opinion.

I had no idea what I was doing when making these castings, but the way to learn is to try, fail, try again, fail again, and continue trying until you succeed.

Nobody ever got an engine built by giving up when things didn't go right.

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Ok, I was able to reload Solidworks.
Not an easy task, and it requires license transfers over the net, and some serious sweating while hoping the transfer goes through.

Here is Part 1 of the STL files for Bob J's No.21 Oscillating Steam Engine:
 

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Here is Part 2 of the STL files for Bob J's No.21 Oscillating Steam Engine:

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Here is Part 3 of the STL files for Bob J's No.21 Oscillating Steam Engine:

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Thanks for posting the design.

I would suggest that if you're going to supply 3D CAD models, post them in .STP format. .STL is for 3D printers and most CAD software that I've used doesn't really open up .stl files that well.

RJC
 
verdenstein-
Thanks for the heads-up.

I have not posted any 3D files on a public forum prior to this, so this is new ground for me.

The file extensions have always confused me, but I will try to keep up, LOL.

Here are .STP files for Bob J's No.21 Oscillator Steam Engine:
(Part 1)

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Edit:
This site will not allow me to upload .STP files.
I will have to upload these files elsewhere.

I will post a link in a minute. (sorry, this link no longer exists)

https://www.classicsteamengineering...s-no-21-steam-engine-a-tutorial-by-admin.927/

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well first casting or not I think it looks good. I’ve only ever cast small silver jewellery in sand so NOT an expert. Many photos of castings in kits don’t look too much different. I’m fairly certain I could mill that ready for use, so that in my mind makes it a good cast!
Thanks for the thought of the No21 engine that is a great looking design. I’m only equipped for metric so not easy for me and I note with some regret what you say about the metric offering. Don’t think I’ll support that.
 

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