Author Topic: Gold Blend. A Coffee Jar Engine........ (Read 54130 times)

Stilldrillin · « **on:** July 20, 2011, 03:52:43 AM »

A couple of weeks ago, after finishing Rizzo, I had a vague idea...... Something larger. Perhaps!

To maybe, make a hot air displacer cap, from a stainless steel salt/ pepper pot.

So, I took a walk in my local Wilkinson's.... And found a coffee jar too!

Here they are, leaning affectionately upon each other........

I gave the jar some thought....... A medium temperature hot air engine!

It will need a plug to form the top deck.

Soon, I had topped an old square piece of 1/4" alloy, into a round piece of 1/4" alloy.......

Something like this sort of idea.
At 11mm down, it could hold water, for cooling......

Someone, somewhere, has mentioned balsa wood, for a displacer.

Mounted on 4mm dia silver steel. Messy stuff.........

Next up, two .9mm steel discs. Turned .1” under the 3.75" bore size........

This was the collection at yesterday's knock off.......

At 1" stroke, what diameter power piston should I go for?

I'm just drifting along with it....... Allowing it to develop.......

Anyone any thoughts/ input?

David D

sbwhart · « **Reply #1 on:** July 20, 2011, 05:28:31 AM »

Now this looks interesting

Stew

arnoldb · « **Reply #2 on:** July 20, 2011, 01:53:57 PM »

Nice one David

Don't know about the power piston diameter; Stirling engines are still a bit of an unknown to me... But I would have thought that you would have hollowed out the balsa sandwhiches in between the outer ones a bit to drop a bit more weight

Looking forward to your progress though

, Arnold

DaveH · « **Reply #3 on:** July 21, 2011, 03:30:35 AM »

David,

Looks very interesting

DaveH

NickG · « **Reply #4 on:** July 21, 2011, 04:58:29 AM »

David,

Looks like a great start to me.

Is the displacer still quite light with that rod? Will all need to be light for this sort of engine. Are you going to use graphite for the power piston or will it be a bit hard to get in that diameter? It would be a good idea as light, self lubricating and easy to get a good fit. Prob worth doing for the displacer rod guide too but the brass you have there might work if it's a good fit.

Leaving a recess for water sounds a good idea to me too. You could always stick a tea light under it if you find it needs more heat too.

As I always bang on about, for an LTD you generally need a fairly high ratio of swept volumes, but I'm not sure how high. Assuming you are making the displacer and power cylinder both the same stroke (you don't have to since there will be two cranks) and your Power Piston bore looks about 1"? That would give you a 13.3225:1 ratio which is relatively high but not sure whether it's high enough.

I've got some pics of a commercially available LTD which worked really well, I could try to scale those off and get some idea if you think it might help. That thing could run from the heat of your hand with no cooling to the top plate!
Nice work

NickG · « **Reply #5 on:** July 21, 2011, 06:07:06 AM »

David,

I found this link useful, thought you might like to see it. Ihad to read it a few times but think I get it!

http://www.stirlingengines.org.uk/modeng/note.html

Cheers,

Nick

Stilldrillin · « **Reply #6 on:** July 21, 2011, 03:58:04 PM »

Thanks for your replies Chaps!

Arnold.
The displacer feels surprisingly light, for it's size. About the same as Boggy's Robinson replacement.
I thought about hollowing the centre, making rings. But, wasn't sure what the heat might do to any glue used. I think unglued solid discs might be best.... For now.

Nick.
Thanks for your usual enthusiasm!
I have a piece of brass tube, which should clean up at 17.5mm bore. Piston will be brass too, probably.
I am hoping it will run on a small, single wick meths burner. If it runs on only a tealight, I'll be delighted!

I have a Contax LTD engine..... Running this past 14 months, behind my computer. That is my inspiration......

Thanks for the link. Read some time ago...... Always good for a refresher!

Managed a little progress today.
Attached the disc to the 4mm shaft, using a 3mm countersink screw, and my faithful high temp sleeve lock.......

Turned the o/d to bore size........

Drops in, so far..........

A gentle push, gets it to the bottom.......

This then locates the top deck. Holding it level, and concentric with the displacer shaft.......

I think 4 off, 3mm screws through the side, into the deck will locate. Allowing future dismantling and accurate re assembly.

After an hour or so in the oven, to dry out any remaining moisture, I will reduce the displacer to .1" clearance.

I'm expecting no progress during the next few days..... A little Crawling Person will be demanding Grandad's attention!

David D

NickG · « **Reply #7 on:** July 22, 2011, 04:12:51 AM »

David, this is the sort of stuff I've found myself really interested in over the last 5 years or so! People at the club give me funny looks, little sniggers etc as it's heavily loco orientated - I can only assume they haven't built / understood these magical machines!

The LTD I used to have was the same one - they are so well made and would be a good thing to give a few hints on design features.

Ah, I thought you were using the pepper pot for that. The 17.5mm tube may be better. The other thing I've heard of people using is K&S brass tube, which apparently is pretty accurate internally.

The only thing I'm slightly worried about is the heavy displacer rod / disc at bottom, but if the intention is a spirit burner, it may not matter.

Looking forward to progress after weekend - am off camping in Northumberland so will check when / if I return!!

Cheers

Nick

Stilldrillin · « **Reply #8 on:** July 22, 2011, 01:16:02 PM »

Hope you have a great weekend Nick!

Used to spend a lot of time in, above, and underneath the Yorkshire Dales. Just the memory of those times, starts the arthritis nagging, these days.

Herself says the engine should have a name, like most of my others.......

"Gold Blend", she says!

Guess I need to make the rest of the parts, in brass.......

David D

stirling lad · « **Reply #9 on:** July 24, 2011, 11:05:49 PM »

Good grief, your not hanging about with this one. great design, great progress, sods law must be on holiday.
I hope you manage to get loads more done before it gets back ... with a little surprise for you.

keep up the good work, I might try to copy your design one day... after i find the instructions for my screwdriver set.. Doh!

...Mike...

NickG · « **Reply #10 on:** July 26, 2011, 03:07:04 PM »

Cheers Dave, back now, had a good time. Our last two trips were in the Yorkshire dales so we thought we'd try somewhere different, I went to these places as a kid too so brought back happy memories! Going somewhere in the lakes next week, I know what you mean though, beginning to realise it's quite hard work this camping lark! I think I may end up with arthritis, have always had overly achy joints etc for my age and a few of my ancestors have had it.

Ha, as good a name as any, yep time to get the brass out when you've recovered from granddaughter duty!

Nick

Brass_Machine · « **Reply #11 on:** July 26, 2011, 08:17:40 PM »

Very cool. I don't think I have seen you actually build an engine yet... repair and restore, but not build? Or am I mistaken?

Anyways... very cool idea!

Eric

Stilldrillin · « **Reply #12 on:** July 29, 2011, 12:28:39 PM »

Mike, Nick.... Thanks!

Eric. Only the one!
I was feeling a little left out, when everyone was making rocking engines.

http://madmodder.net/index.php?topic=1705.0

After this one, normal service will return, as I have 10 or so differing oddballs to sort out.

Here is one of them........

Anyroad! I made a cylinder out of a piece of bronze tube, 2" x 3/4 od.

Bored it through to clean up. Turned a piece of delrin, a couple of thou' undersize.......

Then spent the next hour or so lapping, with Brasso........

Think it worked ok.........

Turned/ tapped and parted the piston........

Then screwed it onto a 4mm screw, with spacer. To fin turn o/d.......

Threaded a piece of 4mm silver steel, for conrod.

Rather pleased. It won't quite drop any further in, until touched. Then it slides the whole way down........

Next up. I need to recess the cylinder into the deck, at 36mm centres with the displacer bush.......

Slight problem now, no boring head! ......... And it needs a hole a few thou' under 3/4". Just here.......

But, Rizzo has been sold on. And a boring head has been ordered, with the proceeds.

Hoping for delivery, and continuation, Monday.

David D

dickda1 · « **Reply #13 on:** July 29, 2011, 01:25:46 PM »

I really like your idea of using Delrin for the lap. I gather it did not bell mouth the top of the bore.
Dick

arnoldb · « **Reply #14 on:** July 29, 2011, 03:05:08 PM »

Coming along great guns David

Just gotta love Brasso; I see you also mix it with some oil for the lapping.

, Arnold

Stilldrillin · « **Reply #15 on:** July 29, 2011, 04:18:18 PM »

Thanks Dick.
The delrin was turned full length, plus about 1/8".......
I just oscillated by about 1". Allowing cyl to rotate a little, every few seconds. Then I swapped ends, every couple of minutes, or so.

When I made the piston, it was slightly tight, at one end. 5 mins more oscillating got it parallel.

No bell mouth, that I noticed......

Thanks Arnold.
I would have liked something a little more abrasive. But couldn't find anything else in the kitchen cupboard......

No oil! I regularly dipped my fingers into the reservoir, and applied. The darker stain is drips from the polished brass.

Done over a couple of days. (I can't stand for too long at a time). The polish had dried in the saucer, so I added WD40..... Didn't work! Had to use fresh polish......

David D

Rob.Wilson · « **Reply #16 on:** July 30, 2011, 04:02:34 AM »

Way to go David

Very interesting build

Rob

NickG · « **Reply #17 on:** July 30, 2011, 01:59:42 PM »

Nice work David, perfect fit!

Never really done any lapping myself other than wrapping emery around a stick which after being on the forum for a few years now I realise is the wrong way! But I have heard people use tooth paste? Or would that be too abrasive for your needs?

Nick

CallMeAl · « **Reply #18 on:** July 30, 2011, 02:11:25 PM »

Interesting engine made with such a variety of materials! Nice!

arnoldb · « **Reply #19 on:** July 30, 2011, 04:27:12 PM »

Ahh - the dried-out Brasso problem then Dave... Plays hell when it dries out while trying to lap something

- just tightens up and things want to freeze up.

I think Brasso is water-based - in the dry climate I live it really dries out quickly. I just take the dried powder and mix it with some light/thin sewing machine oil and that works well for running in engines and a bit of lapping

- like you said, it's slow

- I have used a bit of fine valve-grinding paste for rougher jobs. And I recently got some tubes of diamond paste, to be used in anger at a later date, but keeping in mind that the lap needs to be softer than the workpiece to prevent the diamond embedding in the workpiece.
That WD40 stuff is more solvent than oil - so it ends up evaporating and leaving just the near-dry paste again

- I think that's why I get more fun from the light oil.

, Arnold

lazylathe · « **Reply #20 on:** July 30, 2011, 05:24:00 PM »

This looks like a fun build David!!!

Following with eager anticipation!

For now i will play with cans and make a simple Stirling first before i reduce too much metal into AMAZING scrap....

Andrew

stirling lad · « **Reply #21 on:** July 30, 2011, 09:12:36 PM »

:offtopic:sorry to go of topic a little David, but nick mentioned lapping with toothpaste,
would smokers tooth powder be any good as its a fine abrasive ?
and its a pretty pink colour so you could try getting the missus to do it for you,haha.

...mike...

DaveH · « **Reply #22 on:** July 31, 2011, 06:10:55 AM »

Looks very good,

DaveH

Stilldrillin · « **Reply #23 on:** August 04, 2011, 01:03:06 PM »

Thanks for your replies Chaps! Much appreciated......

Nick.
I never thought of raiding the bathroom! Or trying scouring powder....

Mike.
Smokers Toothpowder? I think Colgate Sensitive is more me!

Got a little more done.

Drilled the deck, and opened up to 18mm.......

The new boring head had arrived. So, reset and clocked true........

And bored out to 18.5mm.......

The whole clocking/ boring operation took around 20 mins.
This is the first time ever, I've used a boring head. Despite first using a milling m/c in 1958!

I wonder if I'll ever use it again? Something special... Awaiting a something special job......

Shortened the cylinder tube to, stroke + piston length. Then turned spigot to -2 thou on hole size.......

Nothing is finished, yet.
I'm not sure about the steel discs. Might try protecting the balsa with cooking foil.....

Time to start cogitating on the crank assembly......
Can't get me head away from a Ross yoke. But, I don't understand the calculations.

David D

doubleboost · « **Reply #24 on:** August 04, 2011, 05:34:29 PM »

Looking very nice
I keep forgeting to use my boring head
John

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Author Topic: Gold Blend. A Coffee Jar Engine........ (Read 54130 times)

Rob.Wilson