Author Topic: Ringbom 1: Tim's Ringbom Stirling Engine Build  (Read 3675 times)

Offline Admiral_dk

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Re: Ringbom 1: Tim's Ringbom Stirling Engine Build
« Reply #30 on: May 15, 2021, 10:08:29 PM »
A nice detailed description so far - still following and enjoying your description  :ThumbsUp:

Per

Offline tvoght

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Re: Ringbom 1: Tim's Ringbom Stirling Engine Build
« Reply #31 on: May 18, 2021, 12:40:30 AM »
Thanks for checking in Per.
As I said in my last post, the photos are exhausted, but I will attach drawings of the remaining parts and try to give descritptions of how these parts were made.

The next part is a graphite bushing for the displacer rod. It is epoxied (JB welded) into the cooler. It has a reduced diameter in the center of its length so that the JB Weld that bonds well to the aluminum will fill the reduced diameter portion and lock the bushing into place. This is because the epoxy will not bond to the graphite.

There is little to say about the machining of the part in the lathe except that graphite turns extremely easily, and there is danger of over-shooting the mark on intended dimensions. One strategy is to get near to dimension with lathe tools, and then finish up using ordinary printer paper as an abrasive.

A drawing is attached.

Offline Roger B

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Re: Ringbom 1: Tim's Ringbom Stirling Engine Build
« Reply #32 on: May 18, 2021, 08:03:25 PM »
Interesting  :)  :thinking:  I am heading towards the cylinder and pistons for my rhombic hot air engine and due to the lack of suitable SS tube I was thinking about making them from bar stock. I have managed to core drill cast iron and aluminium but I am not sure it will work with SS
Best regards

Roger

Offline tvoght

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Re: Ringbom 1: Tim's Ringbom Stirling Engine Build
« Reply #33 on: May 18, 2021, 11:44:24 PM »
Hi Roger, thanks for commenting. The latest iteration of my method really works quite well and allows for a really thin wall. The next time I do it, I will try an even thinner wall perhaps 1mm. I know there must be a practical limit, but the 2.5mm walls are not a challenge at all using this method.
When you speak of core drilling are you referring to using annular cutters? I saw a good video from Adam Savage (of Myth Buster TV show fame), advocating them for our kind of applications. While he is a bit prone to hyperbole, He said they have "changed his life". I went ahead and bought a small set and will experiment with them for this purpose.
I have experimented some with 304 stainless tubing, with the intent of hard soldering ends on, but in the end, I would want to thin the walls anyway.

--Tim
Adam Savage on annular cutters:
https://www.youtube.com/watch?v=-5zSadDZMhA
« Last Edit: May 18, 2021, 11:47:38 PM by tvoght »

Offline tvoght

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Re: Ringbom 1: Tim's Ringbom Stirling Engine Build
« Reply #34 on: May 21, 2021, 09:11:40 PM »
I do have a couple of photos to show concerning the flywheel, but only of the operation I used to reduce waste of my cast iron stock. I had purchased some 3.5 inch stock at 1 inch length. The supplier sawed it off a bit more than an inch long. I really only needed the inch so that I could turn a hub on the wheel as planned. But I thought "how can I make the hub without so much waste?".

These photos show briefly how I got material for two viable flywheels from the stock.

Using a CNC program to outline the hub portion about halfway through the stock. A lathe operation would have worked with possibly a wider cut.



Cutting down to the hub groove. This took a few settings in the bandsaw to cut all around.




The rough parts. The one on the right to serve as stock for the flyweel on this engine, the other can be attached to a separate hub for a future engine.



A drawing of the flyweel to be made is attached. It was meant to be held to the shaft with a clamping collar. A vendor's drawing of the collar I used is also attached. I have to point out that the clamping method ultimately failed with cast iron, as the "tabs" were just too brittle, and one of them broke off under clamping pressure. I ended up drilling out the cast iron hub and replacing it with a more ductile steel hub. The same clamping method was used, and worked fine with steel.


 

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