I`ve not posted this until now as I`ve got 101 projects on the go and wanted to get a little closer to finishing this one before talking about it. I have been posting little blogs on my website and so I`ve basically pulled my three enteries on this build from there. I`ve been working on this for about 3 weeks now on and off. One thing I`m starting to learn is that things take time and up until now I`ve been rushing everything to get a result ... hopefully this will pay off but yet to see....these engines aren`t easy to run but really blow me away!
This is Jan Ridders Simple LTD Stirling....
--part 1 July 15th 2010 --
I made an attempt at an LTD Stirling Engine several months ago and failed quite miserably. I know these things are temperamental but after my first attempt I did have quite a few ideas for improvements...nothing new, things that people have already been doing but stuff that I ignored! So over the last few months despite having 101 other projects on the go I started collecting materials. I decided on a glass cylinder with a graphite piston for the power piston and also point bearings as shown in Jan Ridders latest LTD simple stirling plans.
Here is the lump of graphite I`ve managed to get hold of... it is a fair old lump!
And it seems to cut OK. I hacked a long block off the top and turned it down holding the vac under the tool to pull all the graphite dust away. This was just a test but I used the same process to make the displacer piston bushings.
The power piston will have a glass cylinder. I needed to know that I can cut test tubes before I got into this and this setup worked a treat. Turning the glass slowly in the lathe I eased the dremel cutter slowly into the tube. I believe you can cut it half way and snap it the rest of the way but I actually held a cloth under it and cut right through.
Here is a collection of most of the materials. The only thing missing is the 2.5mm silver steel which I forgot to include in the picture.
The container was purchased at Asda for £1 and is about 101mm OD. I rang a plastic company and for a 100mm OD clear acrylic piece of 20mm length they wanted £12 plus £10 postage!!!! I think this will do the trick nicely and it cut far more easily than the tapered Tesco spaghetti tube I used last time - the 20mm cut off length can also be seen above! You can also see the glass cylinder.
So I`ve now made some progress with the displacer cylinder, top and bottom have been cut and the top displacer rod hole bushed with graphite. The displacer cylinder will be permanently sealed once completed unlike some designs (and my last attempt) which used screws to clamp the cylinder in place. I think I had a problem with air leakage last time so this time I`ll stick to Jans idea of a permanent seal. I`m actually going to use sealant to permanently bond the bottom section of the aluminum to the plastic displacer cylinder. I`ve cut the top aluminum so that there is a rim of the same ID of the cylinder. This allows me to lock the cylinder onto the rim and I`ll use a small bead of silicon just on the outside join to seal the two as it is held tight without any bonding. If anything does go wrong it`ll be easier to cut this small seal if I need to disassemble the displacer again.
-- Part 2 - 21st July 2010 ---
Still pushing on with this, I have now cut a new cylinder to size and with a better finish from a 16mm OD test-tube with 14mm ID. This is the graphite piston to a perfect polished fit. This is the first time working with graphite and I`m very impressed with the fit!
Wasn`t quite finished in this picture but you can see the mirror finish starting.
This is the graphite bush for the displacer rod.
Since I don`t have a boring head for the mill and didn`t want to offset the plate in the mill, I luckly had this step drill that gave me just the 16mm by 3mm shoulder I needed just to sit the glass piston cylinder inside.
I then turned up two supports...
And here is the insert for the graphite power piston.
And what I have so far....
------ Part 3 - 3rd Aug 2010 ---
A little update here as I feel I am coming to the final straight!
Here is a picture of the parts so far but not including the glass cylinder and graphite piston - they are safe away from potential smashes! I`ve now cut the main parts for the crank shaft assembly - the displacer and piston rods, various size parts to the crank axis and of course the four webs.
I`ve also turned the tiny graphite bushes that sit between the webs and allow smooth movement of the rods.
I have now made a small error as at the same time I`ve not soldered the other axis to give the 90deg shift. I DID thread them onto the axis to keep them aligned whilest silver soldering these bits and my intention was to solder the axis for the 90 deg shift in my next "shop time". Of course when I solder the next bits, it`ll loosen the current soldered parts!! I am strongly considering gluing the other parts that make up the crank assembly. Especially with it being a stirling engine, there are few excessive forces or temperatures to worry about.
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I`ll keep updated from here, any advice appreciated. I really hope this runs!!
