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 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.
So that is where I`m at right now. My aim is to actually get this finished hopefully during the next couple of weeks. There isn`t an excessive amount of work in it now.
Chris
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