# LTD stirling engine



## Twinsquirrel (Jun 17, 2008)

OK, this is the story so far on my first project on my lathe and my first proper engine, I'm not using plans just using the "ugly" LTD as a basis.







I have the top and bottom plates for the displacer cylinder done, I'm not that happy with the grooves or seats for the cylinder itself, not sure wether it was the tool I ground or the backlash in my cross-slide (now fixed) but I couldn't seem to make any cut without A LOT of chatter.

The displacer cylinder itself is cut from a spaghetti jar, it wasn't until I had marked out and cut the grooves in the top and bottom plates that I realised it had a slight taper....doh!!

Still I'm relatively pleased with the progress so far.

David


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## Brass_Machine (Jun 17, 2008)

Looking good so far David.

Keep posting your progress


Eric


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## Twinsquirrel (Jun 18, 2008)

Thanks Eric,

Ground my first boring bar yesterday which looks a bit funny but seems to work OK so I will probably tackle the power cylinder tonight. I am planning to use a ferrite from an old PC power supply as the power piston, any thoughts?

David


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## Bogstandard (Jun 18, 2008)

David,

The chatter is normal when using a wide faced cutter, you only have to be a few thou out on cutter height or bit out on rotational speed. So you are not alone on that score. 
It all depends on how you are going to seal the cylinder at the top and bottom. If you are going for silicone sealant, the chatter marks won't make any difference, I wouldn't worry about it.

I have yet to make a large Stirling, but your idea of using a ferrite rod sounds ok. If it doesn't work, I can always send you a lump of pure graphite to hack up.

John


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## mklotz (Jun 18, 2008)

One of the reasons for using graphite is its self-lubricating properties. I'm not familiar with ferrite in this application but you may want to investigate that. Remember that LTDs have miniscule specific power - so little in fact that they are run dry because the viscosity of any lubricant can sap too much power.


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## Twinsquirrel (Jun 18, 2008)

Well the ferrite idea is a non-starter unfortunately, I tried to turn a small piece down to the correct diameter earlier and the ferrite seems to be made up from iron fillings (should have guessed from the name) compressed together with some sort of binder, probably epoxy. The material doesn't machine well at all and just crumbles/chips when cut. 

I guess graphite is the way to go as you both say, I'd love to take you up on your offer John or if you could point me in the direction of a supplier that would be great too...

David


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## Bogstandard (Jun 18, 2008)

PM or email me with your name and address, and I will get a lump into the post for you on friday.

What size piston are you making? So I can send you the right sized lump.


John


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## Twinsquirrel (Jun 18, 2008)

I can't thank you enough John, you have PM.


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## Twinsquirrel (Jun 22, 2008)

Spent most of the day in the workshop today but don't have a lot to show for it I'm afraid. My 3 week old cheap nasty Chinese lathe decided it didn't like me touching the forward/reverse switch and refused to start , I did manage to get a few bits done to the power piston/cylinder after bypassing the switch.






Thanks to John for letting me have some graphite for the piston (the man is a saint). The aluminium insert is a light interference fit inside the piston but I will probably use a drop of cyano to hold it in place.

David


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## CrewCab (Jun 22, 2008)

Twinsquirrel  said:
			
		

> Spent most of the day in the workshop today but don't have a lot to show for it I'm afraid.



Tell me about it  ??? ....... my ball turner is probably worth about £20 in a commercial environment, in terms of man hours spent in the shop it should be worth about £600  ;D 

Anyway David, what you've produced looks pretty well finished to me, just for reference mind, if you could you stick a coin or something in the photo it would be useful, I'm having trouble judging scale : ........ is the cylinder Aluminium or steel btw

nice work mate 8) ........... including working around the switch

CC


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## Twinsquirrel (Jun 24, 2008)

Hi CC,

Yep, sorry I should have put something in the pic for scale, will do next time. Just to give you an idea the bore of the power cylinder is 13.5mm or just over 1/2" in old money. I'm doing pretty much everything in Aluminium for the moment just to get a feel for things as I'm really completely clueless. 

David


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## Twinsquirrel (Jul 5, 2008)

Had a reasonably productive day in the workshop today.





I managed to get most of the parts finished and ready for lapping, balancing and polishing tomorrow. 

Sorry, I forgot to put anything in for size reference again :-[ :

David


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## CrewCab (Jul 5, 2008)

Well they all look nicely finished already David ............ good luck, looking forward to seeing it running 8)

CC


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## Divided He ad (Jul 5, 2008)

Looking good David, I think I am really going to have to work my way up to building one of these! 

LTD's are really my favourite model engine... I'm just waiting for my accuracy to catch up with my ambitions!! ;D


I'm sure we are all awaiting the Final pic's and the Near obligatory video  ;D



Ralph.


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## Brass_Machine (Jul 5, 2008)

Looking good so far. Very nice work.

Eric


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## Twinsquirrel (Jul 6, 2008)

Thanks for the kind comments all,

All assembled now, just waiting for the adhesive/sealant on the top and bottom plates to go off then I will try to give it a run! 






Ralph

I probably shouldn't have attempted an LTD as my first project but I just needed to get this one out of my system, now I have a big list of things I need to make/buy and a whole world of things I need to work on as far as technique goes. Having said that with the help of this board and using Bogs' "looks right, feels right" mantra it wasn't too difficult...... Then again it hasn't run yet :-\ :-X :

doh!! just realised I STILL didn't put anything in for scale :-\

David


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## CrewCab (Jul 6, 2008)

Twinsquirrel  said:
			
		

> doh!! just realised I STILL didn't put anything in for scale :-\



Well .......... just stick your thumb in front of the lens next time ;D

So ..... Looking Good ........ what's the curing time for the adhesive 

CC


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## mklotz (Jul 6, 2008)

For "does it run?" purposes, you can "seal" the displacer chamber with Vaseline. Remember, the air pressure developed inside one of these is only minutely above atmospheric. In fact, my LTD is still running on the "temporary" Vaseline I used to test it.


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## Twinsquirrel (Jul 6, 2008)

> For "does it run?" purposes, you can "seal" the displacer chamber with Vaseline.


 Argh, wish I had known that before Marv!

Anyway, the epoxy has gone off now and I can confirm IT LIVES!!! After a little tweaking of the timing I'm getting 200-250rpm from a cup of near boiling water.

Big Grins

David


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## Powder keg (Jul 6, 2008)

Congratulations David!!! That reminds me, I need to mess with mine again. 

Great job!, Wes


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## CrewCab (Jul 6, 2008)

Twinsquirrel  said:
			
		

> Anyway, the epoxy has gone off now and I can confirm !T LIVES!!! After a little tweaking of the timing I'm getting 200-250rpm from a cup of near boiling water.



*Pictures man* ;D  

Well done David, bet you feel warm n' fuzzy all over  .......... heck I'm no expert but that sort if rpm from a cup of tea sounds pretty good to me.




			
				Twinsquirrel  said:
			
		

> Big Grins



........... think I can see the glow in the sky from here 

Nice one 

CC


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## mklotz (Jul 6, 2008)

Congratulations! Well done!

Now take it out in the sun* and set it on a saucer of ice cubes. It should run in the opposite direction. You may need to cut a piece of flexible matte black plastic to fit the top and lay that on to help with heat absorption.


--------------
* Since you're in the UK, you may be unfamiliar with this term, so I'll explain. Occasionally you may have noticed a big red ball in the sky. I know you'll find this hard to believe, but that red ball emits a lot of heat. This is especially true during your week of summer so try the suggested experiment soon.


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## Twinsquirrel (Jul 6, 2008)

mklotz  said:
			
		

> Congratulations! Well done!
> 
> Now take it out in the sun* and set it on a saucer of ice cubes. It should run in the opposite direction. You may need to cut a piece of flexible matte black plastic to fit the top and lay that on to help with heat absorption.
> 
> ...



LOL  Will give that a try although when us Brits experience that phenomena we are very busy putting on our shorts and sandals (with socks), cremating meat products on the bbq and moaning about how hot it is. By the time we have done that the drizzle has usually returned :-X


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## Twinsquirrel (Jul 6, 2008)

Couldn't resist another picture


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## CrewCab (Jul 6, 2008)

Twinsquirrel  said:
			
		

> Couldn't resist another picture



'bout bloody time ;D ............. where's yer' thumb for reference :



David, to be serious though ............ that is a very elegant piece of engineering, you should be proud ............ and rightly so :bow:

CC


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## chuck foster (Jul 6, 2008)

the good thing about this one is if it don't run (I'm sure it will) at least you have one hell of a good looking piece to put on the shelf ;D

looking for video .................... a.s.a.p. 

chuck


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## Bogstandard (Jul 6, 2008)

A very classy looking engine David, lovely sleek lines, and what a bonus, it runs as well.

Big 'cheesies' all round.

Very well done.

John


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## Mcgyver (Jul 6, 2008)

David, that looks great, finish and design are both right on imo.


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## Brass_Machine (Jul 7, 2008)

mklotz  said:
			
		

> ...
> * Since you're in the UK, you may be unfamiliar with this term, so I'll explain. Occasionally you may have noticed a big red ball in the sky. I know you'll find this hard to believe, but that red ball emits a lot of heat. This is especially true during your week of summer so try the suggested experiment soon.



I just spit soda out of nose laughing so hard!

Job well done! Anxiously awaiting the video of it running. Have you been hanging with Ralph? That is a very cool style.

Eric


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## Divided He ad (Jul 7, 2008)

I wrote a comment on this last night just after the pic was put up... then the server went nuts and booted me off the site! I lost the comment and a reply to a pm!? something funny going on... and I don't mean ha ha! ??? 

The basic gist of my comment went something like this....


That's very nice... I do like the retro-futuristic styleee of it :bow: (if that is allowed as a phrase?) I like shiny ;D 8) ;D 

I want to see it run!!! I.E. where's the video at? : (still in editting?)  (stick a size ref' in it... like your hand!) 


Seriously, I really like the look of it.... Now when I make mine I am really going to have to think about the design!!! 



Top stuff David. As they keep saying to me... your raising the bar for your next one!! 



Ralph.


(Eric, as far As I know I do not know David....Similar age! I can see that the general British flair  is shining through ;D )


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## Bogstandard (Jul 7, 2008)

Ralph,

I don't think it is 'British flair' at all.

What it is, in the UK we have a much larger percentage of the population interested in model engineering, and we have basically been at it a lot longer in the engine design stakes, and so we tend to show more of what we do. So we have been exposed to it a lot more.

I have seen some fantastic models on well hidden US sites that easily match us for flair and design.

Just wait until this site has sucked in a lot more of our American and Canadian cousins, and they start seeing what we are doing. Then I think, when they get over their shyness, and start to experiment a little more, you will really start to see what they can achieve. It is very early days yet.

I think in time your new crown will be 'stolen' from you.

John


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## Twinsquirrel (Jul 7, 2008)

Thanks chaps,



			
				Divided He ad  said:
			
		

> That's very nice... I do like the retro-futuristic styleee of it :bow: (if that is allowed as a phrase?) I like shiny ;D 8) ;D
> 
> 
> Ralph.



Interesting way of putting it, kind of sums me up too. There are quite a few bits on it that let it down I think i.e. the small end on the displacer con-rod, well the con-rods in general and I could have done a better job on the polishing.


The video is in the camcorder but unfortunately I seem to have misplaced my firewire cable so I have no way of posting it, will do a quick one on the mobile phone later. I'm no Ralph Spielberg though : 

David


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## SmoggyTurnip (Jul 7, 2008)

Great looking machine.

I am wondering how the power cylinder is attached to the top plate.


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## Twinsquirrel (Jul 7, 2008)

Smoggy,

I single point cut an M8 thread (only about 1.5 threads) on the power cylinder and tapped the top plate to match. I would take a pic but it is a threadlocked in now and I dont want to break the seal.

Cheers

David


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## Divided He ad (Jul 7, 2008)

I was only poking them a little John.... No need to Threaten the crown... I've only had the damn thing for a week!...Not too sure I deserve it.... I polish on a lathe you know!! : 
 The way it looks I won't have it for too long anyway!! many far better engines out there than mine... Wait until Bret puts some sparkles on that single!

David, I think it looks just fine as it is  The vid is only a requirement for us 'like to watch bunch'... not a requirement to stay in the class ;D 

Spielburg eh!!..... Hardly! I just use the standard windows movie maker... Anyone can do it. It just takes a little time. well could take hours.... depends on how much you try to get it perfected!?!


Looking forward to the vid, No rush I'm not going anywhere... Well not planning to! ;D 



Ralph.


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## Twinsquirrel (Jul 7, 2008)

k, here it is running, sorry for the poor quality video/audio. video editing is such a frustrating experience!!! I thought the "oompah" music fitting.

[youtube=425,350]<object width="425" height="344"><param name="movie" value="http://www.youtube.com/v/JURY8w57Nq8&hl=en&fs=1"></param><param name="allowFullScreen" value="true"></param><embed src="http://www.youtube.com/v/JURY8w57Nq8&hl=en&fs=1" type="application/x-shockwave-flash" allowfullscreen="true" width="425" height="344"></embed></object>[/youtube]

David


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## CrewCab (Jul 7, 2008)

Absolutely excellent David 8)

CC


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## Bogstandard (Jul 7, 2008)

Poetry in motion

'nuff said

John


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## mklotz (Jul 7, 2008)

Very nicely, and elegantly, done, David. 

Given their penchant for drinking tea, every Englishman should have one.

Take it down to the pub. I did that (well, we call 'em bars here) with mine and ran it off a cold* beer. A number of people crowded around to see what was going on.  To the delight of the barman, the sale of beer escalated. I didn't pay for beer for the rest of my stay. 

--
*That's cold by British standards. (Actually, I prefer the serving temperature encountered in British pubs.)


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## rake60 (Jul 7, 2008)

Beautiful David! :bow:


Rick


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## kustomkb (Jul 7, 2008)

Nice, Its really movin!


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## bretk (Jul 7, 2008)

Very Nice!

You know, the front view in the video, it kinda looks loke one of those hula hula girls I used to have on the dashboard ! :big:  :big: All kidding aside, a supurb model :bow:


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## J. Tranter (Jul 7, 2008)

That really is beautiful. 
John T.


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## Divided He ad (Jul 8, 2008)

Now that vid was worth the wait ;D See you too can get all funky with the grafix!  

Nice tune too..I think your right, it fits quite well ;D


I like the movement and the way as Bret said 'it looks like one of those hula hula girls' I never had one on my dash, but I've seen them! 


Nice job all round David,




Ralph.


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## Twinsquirrel (Jul 8, 2008)

Thanks guys, I'm really pleased with the end result...Time to put it on the shelf and start the next one....



> --
> *That's cold by British standards. (Actually, I prefer the serving temperature encountered in British pubs.)



You crack me up Marv  ;D...BTW do you have real beer over there now? Last time I was in your neck of the woods all a man could find to drink was this kind of amber coloured water which someone had mislabeled "the king of beers"....

David


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## mklotz (Jul 8, 2008)

All our beer from the big breweries is, as the Canadians like to put it, like making love in a canoe - f..king close to water. It's best to pour it directly into the urinal and cut out the middleman.

Happily, here in California, microbreweries, where the beer is actually brewed on the premises, have become very popular and many of them turn out a product that is actually worth drinking. It requires a lot of careful tasting to find the best ones but I'm up to the task.


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## malcolmt (Jul 8, 2008)

;D ;D ;D Now that is a lovely piece of work, If i had produced that i wouldn't stop smiling for a week. First class job well done. ;D ;D ;D

keep up the great work

Malcolm


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## BrianS (Jul 9, 2008)

Wow really nice. Beautiful engine and nice video of it. (I even liked the ompah music. It fit somehow.). Was this REALLY your first engine? Big problem for me now, I gotta build one of these types and take it to the coffee shop I frequent and let it run. Yet another project to add to the "list". : I hope you don't mind some questions about it:

Are there plans for it? You said the displacer ring is from a spaghetti jar, is it plastic or glass? Is the bottom, displacer ring and top plate just epoxied together? I have some pink foam would that work instead of blue for the displacer piston? Besides getting a loan where is a good place to get the graphite to make the power piston? Never bought graphite before is it expensive? Sorry if this should have been a PM instead of a post.

Thanks in Advance
Brian


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## Twinsquirrel (Jul 10, 2008)

> Are there plans for it? You said the displacer ring is from a spaghetti jar, is it plastic or glass? Is the bottom, displacer ring and top plate just epoxied together? I have some pink foam would that work instead of blue for the displacer piston? Besides getting a loan where is a good place to get the graphite to make the power piston? Never bought graphite before is it expensive? Sorry if this should have been a PM instead of a post.
> 
> Thanks in Advance
> Brian



Hi Brian, 

I'm afraid I don't have any plans for the engine as I sort of just made it up as I went along, the displacer cylinder is plastic, if you go to your local discount kitchenware store you should be able to pick up a polycarbonate jar pretty for next to nothing. Obviously this sets the size for the whole build, mine is 4.5" in diameter.

You can use almost anything for the displacer piston as long as it is light and fairly easy to work with, I used a craft foam substitute I found on eBay, I think it is actually an insulation foam, pink foam sounds "lovely" . I machined mine by securing it to the face plate and mounting my dremel with a dremel router bit on the tool post.

As far as graphite is concerned, Bogstandard help me out with mine as I didn't have any idea where to get it from either, I have a little left over that I can let you have if you are stuck.

cheers 

David


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## mklotz (Jul 10, 2008)

Here in the States, Enco (and probably MSC also) sell EDM electrodes blanks. They're graphite and can be bought in diameters up to about one inch.

I've built numerous engines using this source for pistons and can confirm that it works well and machines beautifully.


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## shred (Jul 10, 2008)

Artist stores also carry graphite pencils (don't get the more common carbon and charcoal) in reasonably large diameters for cheap. Probably not near as pure as EDM graphite, but I bought a couple ~1"x3" rods for a few $ a while back and they worked well.


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## BrianS (Jul 14, 2008)

Thanks for the heads-up on where to get the graphite.  I will check out a few art/craft stores and I can't find some cheap chunks I'll look into ordering.

Brian


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## Brass_Machine (Jul 14, 2008)

BrianS  said:
			
		

> Thanks for the heads-up on where to get the graphite.  I will check out a few art/craft stores and I can't find some cheap chunks I'll look into ordering.
> 
> Brian



Hey Brian... check ebay. I got a huge rod of graphite for really cheap from there. Are you in the states?

Eric


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