Stirling Engine : Laura

[Brian JohnParticipant @brianjohn93961]

Danny : Thanks for the link but they charge ten times what I buy them for from China (and that includes the nuts). I will call next week to see if they have small sizes in stock though.

Hopper : I wonder if this is Aluminium Potassium Sulphate : it could just be sloppy labelling (Aluminium Sulphate) ?

**LINK**

 

Edited By Brian John on 05/02/2016 08:06:31

[Ian S CParticipant @iansc]

You have it Brian, Aluminium Sulfate is how it seems to be labled. I didn't think of swimming pools, I can only think of one private swimming pool about 5k down the road, there is a public pool in town. Your local council will also use it in the town water supply. Sorry for leading you up the garden path in the hunt for Alum.

That's going to be a very nice looking motor.

Ian S C

[HopperParticipant @hopper]

Yes that looks like the stuff. The MSDS sheet says it is otherwise known as Alum.

Product Name:

Hy

–

Clor Flocculant

Other Names:

Alum, Aluminium Sulphate

Uses:

Water and waste treatment, tanning agent, paper and pulp processing.

see

http://www.hyclor.com.au/pdfs/Products/Manuals/MSDS%20Flocculent.pdf

[Andy HoldawayParticipant @andyholdaway]

What a lovely word – flocculant! Got to try and use that today!

I'm not see if that's exactly the same as the stuff I used. Mine was labelled as aluminium potassium sulphate, and from the formula on the data sheet the flocculant is only aluminium sulphate. Not sure if it makes a difference or not, I'm no chemist!

[AjohnwParticipant @ajohnw51620]

You could look through what these people have for screws Brian. The only problem is that they will usually come in packs of 100 so choose sizes you are likely to need. In my case I have a couple of sizes in nickel plated brass as they usually get used on electronics bits and pieces – BA too but those tend to be a bit expensive now.

You'll find all types of screws kicking around on there.

**LINK**

I just picked out M2 plain brass. Often it's best to search a general term and then use the filters to home in.

There will also be model, say aircraft etc suppliers around at your end that sell screws. There was a good one in the uk, Initially Giant Shark, then Giant Cod and now rcliffe.co.uk but no longer selling screws.

For shortening I usually use the lathe. Unwanted bit in the chuck, part part off, chamfer with a file and then finish off or lock 2 nuts on the thread and grip those, saw off and finish off the end with a file. There are various ways. If I was doing this a lot 1 would make a holder with a split to grip in the lathe. There are all sorts of options but I like neat ends that screw in without any problems.

John

–

[Brian JohnParticipant @brianjohn93961]

I have fixed the main engine assembly to the wooden base. The initial design called for the aluminium columns to be drill and tapped for M2 socket heads and then M2's screwed in from top and bottom but aluminium is messy stuff to drill and tap so I drilled right through the columns and used M3 socket head caps passing straight through. The wooden base is counter bored underneath for the M3 nut and washer. This is my usual method of attaching things to a wooden base.

You can also see six nuts and washers resting on the wooden base. If this engine works (big ''if'' !) then I will sit the whole thing on a larger wooden base having two handles and a copper plate on which to rest the burner. I will drill through this smaller wooden base to take M4 X 40mm socket head caps ; these will be inserted from underneath (counter bored) and the nuts on top. This is not quite as neat as having the socket heads inserted from the top but it allows me to join the two bases easily without disassembling any of the engine parts ie. the cylinders get in the way when trying to insert the socket heads from the top. Placing the holes elsewhere did not look right.

I have finished painting the inner flywheel red (two coats of etch primer and three coats of Killrust) so now I have to wait a few days to let it dry thoroughly. I should have painted it earlier but it was a last minute decision to paint it. The unpainted cast iron did look quite nice and I am still not sure I made the correct choice there.

Edited By Brian John on 06/02/2016 06:15:03

Edited By Brian John on 06/02/2016 06:15:49

[AjohnwParticipant @ajohnw51620]

It's coming on well Brian. Well done. For the future when people look at this sort of post I think it's always worth including the usual 6" rule in the shot. This thread will probably show up in searches for a long long time.

I'm going to make one from a kit mostly based on cardboard to find out a little bit more about them. Alignment has been bugging me as it comes but I think I came up with a solution as I went to sleep last night.

John

–

[Ian S CParticipant @iansc]

My guess is that the graph paper under the motor has about 10 mm x 10 mm squares on it, but I agree with John that a 6" rule or something like that is a good idea, but not a coin, there is such a variation in sizes all over the world.

Ian S C

[HopperParticipant @hopper]

Posted by Brian John on 06/02/2016 06:12:24:

I have finished painting the inner flywheel red (two coats of etch primer and three coats of Killrust) so now I have to wait a few days to let it dry thoroughly.

Doncha just love painting in 34 degree / 80% humidity weather? I've had motorbike stuff take weeks to harden up. At least you can put your little job inside in the air con and knock the humidity down.

[Brian JohnParticipant @brianjohn93961]

1. Hopper : I agree. I have removed the masking tape and masking liquid today and then trimmed the edges with a scalpel. I usually put things in the hot sun on a baking tray for a few days to help them harden and dry. Do you think the air con would be better ? I must be patient The flywheel does look quite nice now.

2. I did call about the pool chemical flocculent Aluminium Sulfate. Even though it is called Alum, the manufacturer said it is NOT Aluminium Potassium Sulfate so I am not quite sure where to go from here ?

3. I did a quick dry run on mounting the flywheel to the supports today (being careful not to touch the fresh paintwork). I am having problems getting the M3 grub screw to hold onto the 6mm axle. Do you usually put a dimple in the axle to solve this problem ? I am worried about not getting the dimple in the correct position.

[HopperParticipant @hopper]

I dont know about the alum quandary. I guess all you could do is get some and try it out. Or wait for the good stuff to arrive from eBay.

I've had paint in this weather that would not harden up even in the sun. But putting it in front of a fan helps, or heat gun used gently. So I think the humidity just makes it hard to evaporate the solvent out of the paint.

A small flat filed on the shaft for the grubscrew to seat on is a common solution. If the flat is a bit longer than the screw you can move the flywheel back and forth along the shaft a little if needed.

[Brian JohnParticipant @brianjohn93961]

The painted flywheel looks quite smart so I think I made the right decision in painting it. The paint has dried enough to handle it so I have filed a flat on the axle to accept the grub screw. I made one axle from silver steel and another from stainless steel ; the latter gives the best fit so I have used that one. I realised that I have almost enough parts to make a second engine. All I need are the premilled base, bearing supports and cylinder holders !

I will be fitting the pistons and cranks tomorrow then I suppose it will be time to try it out. I never really expected to get to this point

I am not 100% happy with the supplied bearings. They seems a bit stiff when the bearing supports are tightened up. I have ordered replacements from Hong Kong which have already been posted (not everybody goes home for Chinese New Year) and they should be here in a few weeks. Hopefully, they might be a better fit.

NOTE : a small ruler has been included in the photos as requested.

Edited By Brian John on 10/02/2016 06:18:55

Edited By Brian John on 10/02/2016 06:28:19

[pgk pgkParticipant @pgkpgk17461]

If the bearings go tight just when you dog down their housings then that suggests you're compressing them oval.. which would happen with any replacement bearings too. Perhaps just a shim between housing parts would be better (paper, drinks can foil..).

If they only go tight when the flywheel is between them then that suggests that the flywheel design is binding on both inner and outer races and you need a shim washer to space just the inner race.

Paint job looks good.

I'm mounting, fettling and assembling mine at the mo. I've not decided re any painting.. I'll leave that until i get it together and see if it runs (stretching my optimism there).

If you truly have enough parts for a second except for the support frame then consider tracing the important aspects of those and fettling up 'duplicates'. You can always modify the aesthetic parts to make them easier to fabricate. For instance the drawing I'm following has its cylinder supports as one thickness cross-drilled and plugged at drill entrance rather then two thicknesses with a groove. And ally is cheaper than brass..

[HopperParticipant @hopper]

Yes it looks good in red. Very spiffy.

HK never shuts down, New Year included. Christmas shopping there is done on Christmas day — all the shops are open.

+1 on shims between the upper and lower bearing housings to reduce clamping force.

[JasonBModerator @jasonb]

Could also be the two bearing supports are slightly off which could happen if the clearance holes have a bit of play. Try it without the axle going rightthrough, if each bearing turns OK on its own when the caps are tight then its not the bearing. Then slip the axle right through without the flywheel, if it binds then things are out of line, if not then as pgk says but beware of adding shims as it may make the total width of shims and flywheel wider than the space between bearings

[Brian JohnParticipant @brianjohn93961]

The bearings do not turn very well on their own which is why I ordered new ones. The clamping of the bearing supports does make it worse though. There is also the fact that metal parts can sometimes be slightly smaller or larger than they should be : you only have to look at the variation when you order 6mm diameter silver steel or stainless steel rod for axles. I am hoping the new bearings may have a slightly smaller OD.

I do have some M2 washers which I can try for shims on the existing bearings if need be but I think they will be too thick.

Edited By Brian John on 10/02/2016 09:36:26

Edited By Brian John on 10/02/2016 09:36:45

[AjohnwParticipant @ajohnw51620]

You could try loosening the screws on each of the bearing supports in turn allowing one to move if needed. Any axial miss alignment between the bearing housings will stiffen up the bearings.

One way to check further would be to remove the housings, put them together and fit the axle. If you run you finger tip across the bases it's possible to feel errors of a few microns.

The base not being flat could cause similar problems.

If this is causing the problem the looser fitting axle may be better providing the error isn't too great.

Reading your last post Brian I would suggest trying to get some idea of how much error you are dealing with. A simple paper shim might fix it. Maybe even aluminium foil.

John

–

Edited By Ajohnw on 10/02/2016 10:08:21

[JasonBModerator @jasonb]

Bit of paper or plastic bag will do you a shim

I may not have made it clear that the clearance holes I was talking of wre where the pedestalls join the base not the bearing caps, try loosening them with the axle in place which will allow then to take up their natural position and then retighten

Edited By JasonB on 10/02/2016 10:06:36

[AjohnwParticipant @ajohnw51620]

I'm guessing it's a height or maybe cross wise alignment error Jason as well. The way it's put together is a tough call. Can't be sure but it looks like they are mounted on wood. If the parts are spot on a small brass plate would give more certain results and if the parts were made from scratch would also help bore them along with getting good alignment fairly easily.

John

–

[JasonBModerator @jasonb]

The caps, pedestal and baseplate come CNC machined so unlikely to be an error there regarding height and bore

Could the the lengths of the aluminium legs are not all teh same and twisting the base or as you say getting pulled down into the plywood display base

[Brian JohnParticipant @brianjohn93961]

Jason : aha…I see what you mean now. I loosened the screws on the base of the bearing supports and then retightened them slowly while the flywheel was spinning. Things seemed to be better now. I also used some M2 washers as shims ; they are 0.5mm thick but seem to be doing the job. I think it was a combination of things causing the problems before.

[Brian JohnParticipant @brianjohn93961]

Final assembly : now for the really tricky part ! I eventually got the work cylinder moving nicely yesterday ; everything turns over very smoothly after many fine adjustments. But the displacement piston is a different matter. When I added the connecting rods I was getting a slight stiffness at TDC. I have managed to eliminate this stiffness by changing various parts and adding washers but there is still a slight twisting motion on the two connecting rods at TDC and BDC that I am not happy with. This also causes a very slight twist in the piston.

I still have to add the the piston rod guidance and the guidance bolts but I want to have a think about this twisting motion for a while and work out a solution if I can. I am not sure it will interfere with the correct operation of the engine but it should not be there…very annoying !

I know the cranks still look a bit rough around the edges but once the engine is working {very hopeful } I will give them a good polish and tidy up. The socket heads through the connecting rods to the crosspiece are a bit long but I have shorter ones on order.

NOTE : Has anybody got this engine to work yet or is everybody else still having problems ?

Edited By Brian John on 12/02/2016 06:12:40

Edited By Brian John on 12/02/2016 06:15:59

Edited By Brian John on 12/02/2016 06:18:18

Edited By Brian John on 12/02/2016 06:18:51

Edited By Brian John on 12/02/2016 06:19:19

Edited By Brian John on 12/02/2016 06:22:11

[JasonBModerator @jasonb]

Twisting would indicate that either the crank pin is not perfectly at right angles to the crank web or the crank web is not at right angles to the crankshaft (axle as you call it)

[Brian JohnParticipant @brianjohn93961]

 I put in a new crank pin and things are not twisting now ; the old pin must have been slightly bent. I spent an hour assembling the engine and another hour trying to get it to work…no luck ! So I have joined the ROYAL CLUB OF FAILED STIRLING ENGINE BUILDERS. Do I get a certificate or something ?

It is not as freewheeling as it should be and the problem is on the displacement piston side. It will only turn over two revolutions by hand ; we should be aiming for five revolutions according to the instructions. I will think about it tonight and try a few things tomorrow. Friction may not be the only problem and I have slightly larger diameter displacement pistons which can be substituted.

It does look good though. I really thought it might work …very frustrating !

NOTE : I think the engine needs to be 20mm higher to have the glass tube in the hottest point of the flame. I did try that but it did not help. If I mount the whole thing on a larger base in the future then I will take this into account.

 

Edited By Brian John on 13/02/2016 06:39:55

Edited By Brian John on 13/02/2016 06:40:39

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Edited By Brian John on 13/02/2016 06:48:32

[pgk pgkParticipant @pgkpgk17461]

I put my failure aside for the moment 'cos the wife's away this week and all the farm chores are mine, plus playing catchup on other jobs and shed cleaning.

BUT one thought I did have is to freeze some horseshoe shaped ice packs to drape over the cold cylinder and increase the differential… see if that gets it running..

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