The 6H7 means it needs an accurate hole so dril smaller than 6.0mm and ream.

Yes drill out the corners but saw and then file to shape, forget the Dremel.

You may have problems with an aluminium cylinder expanding and loosing compression, there is a reason they suggest glass.

Turn end roughly to profile and then file in the lathe, ideally a ball turning tool would be used

I do not think the bullet shaped item is a piston, but a displacer. The cylinder needs to be glass ( pyrex) as this is where the heat is, the glass has very low heat conductivity where as ALU is the opposite and would conduct heat to the cold end – not what you want in a Stirling engine.

As for the bullet shape, not important at all other than asthetic appearance as you can see it through the glass tube.

Start changing things from the original plans ( without knowing what you are doing) and I can guarantee you, you will not get it running.

Beng kits are very good – build as plans show if you do not want to waste good money.

Why would they sell plans desperately? They are trying to sell kits ( beings kits have a lot of parts pre machined 

CNC I would assume) not commercial sense to just sell plans.

Edited By Howard Winwood on 11/10/2015 10:13:21

Edited By Howard Winwood on 11/10/2015 10:14:29

The glass bit can be changed for a metal hot cap, but I would not use aluminium, stainless steel is the best. Depending on the diameter, a good place to get a ready made hot cap is a NiCad battery, I have a little motor that uses the metal case of an AA size battery. I find it unusual that the displacer is made of solid metal, these are normally hollow, and as light as possible. Some of the engines with test tube hot caps also have a test tube displacer.

I bought a little Bohm Stirling Engine from Jaycar, I find it is not really well designed, but it does go.

Ian S C Here's the little one of my design.  The flywheel is 2" diameter  Stainless steel, main and big end bearings are ball races salvaged from VHS tape machines.

Edited By Ian S C on 11/10/2015 12:28:52

The glass test tube can be replaced with metal (stainless steel) but why would you? It is supplied in the kit. The glass test tube will be more efficient in stopping heat getting to the cold end than a metal cylinder.

Plus, with a glass cylinder for the displacer you can see the action of the displacer, it is surprising how many people think the displacer is the actual piston………

I have made a couple of marble Stirling's, everyone I demonstrate them to think the movement of the marbles directly moves the pistons, until I explain the principle and demonstrate the timing.

Brian it is your kit, you are free to do what you want with it, but I would have thought it would have been a lot cheaper just to buy some plans and modify to your hearts content  ( whether it worked or not). There are plenty of plans out there, have a look at Jan Ridders designs/plans – although I would still not change anything, Jans designs will work if made exactly to the plans as SOME parts are quite critical, things like flywheels can be changed without compromising the engines performance.

On the subject of flywheels , they can be easily made from steel/ALU tube and will usually work out a lot cheaper.

Cast iron flywheels can be a pig to machine, others can be a pleasure, you will know which you have when you start to machine it!   

 

Edited By Howard Winwood on 11/10/2015 13:32:03

 

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Spend a few minutes learning about 'Wax Chuck' technique, as used by watchmakers.

… Originally [and best] done with Shellac; but 'SuperGlue' is a reasonable alternative for jobs like this.

MichaelG.

Changing plans is OK if the person making the changes is more experienced than the original designer.

I would imagine you will want the engine to work after you have finished it, so would suggest make as per plan, get it running, THEN make your changes and see what differences your changes make.

I doubt whether you will better the original, please feel free to prove me wrong. 

Howard

I would suggest that instead of making the hot cap from solid, try and get some tube, I'v been getting a stainless disc TIG welded in the end of mine, but my tame TIGer was having eye sight problems last time, so the next one will be brazed in, I use either a narrow strip, or piece of brass wire, It's cheap, and stands the heat on the displacer. The hot cap on my motors needs to withstand red heat. The hot cap for my first tthree engines were made from solid 316 stainless steel, and it took quite some time.

Ian S C

Especially when working close to the chuck, after setting up, it is a good idea to turn the chuck and spindle one or two full turns by hand (with power cord unplugged). Do this to be sure nothing is fouling the chuck jaws or carriage, before switching on.

With most drill stands I have seen for holding corded hand drills, it is difficult to get the drill set up truly 90 degrees to the table and keeping it there. The frustration is not worth the effort. Small drill presses have gotten very affordable in recent years and a good one will be a pleasure to use for dozens of jobs in any shop. I'd look for one if I were you. If shopping for one, take a 6" square and verify the table is at 90 degrees to the column and a drill in the chuck is 90 degrees to the table. Also extend the quill as far out as it will go and wiggle it – if there is perceptible play, look for a different one. For this reason it is wise to buy a far-eastern-made drill press in person.

Good luck, JD

You may be able to devise a way of drilling the holes, if you look at your lathe you'll see that it is a drill press laid on it's side, so you might be able to hold the parts in the tool post, and the drill in the lathe chuck, or if the tail stock drill chuck will fit in the head stock maybe use that.

Ian S C