# LTD Stirling engine



## Powder keg (Jan 5, 2008)

I've been wanting a LTD Stirling so bad I can taste it. I want it to run next to my computer. The problem is I don't have any time. So What I've been thinking about doing is taking several plans I have and combining a few features, that I like, to make a new engine. This engine would be fairly simple, inexpensive to build, and a LTD. I have a few ideas that I want to try. I'd use proven piston sizes/strokes to ensure that it should run:O) Also I'd like it to be running in one weekend. From start to finish. We would call it the "Weekend engine" or something like that? It would then be posted in the plans section.

I was thinking this could be a group project. We could hash out the design and materials. Maybe someone would be kind enough to draw up a nice drawing of it? I've seen some neat 3D renderings(wink, wink) This would give us time to get any materials/tools we might need. The only exotic, harder to get, material I really want to use is Graphite. (I have a couple ideas I want to try) The rest would have to be off the shelf and stock easy to find items. After we get it all designed, The plans would be posted here for the whole world to enjoy. 

The only other criteria, I can think of is no balloons for pistons. I want this to look expensive when its done. 

What do you think? Is this doable? We could plan on a weekend and have a build log. Maybe a couple others would like to build one of their own the same weekend?

Later, Wes


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## Brass_Machine (Jan 5, 2008)

Ok. I'm in.

This is a good idea. I have some other 'group' projects in the back of my head that I have been wanting to present and work on. This is a good way to find out if a group design and group build would work.

I also like the idea of "weekend Engines" 

Not sure what skills I can lend to the project... I do have some CAD skills...


Eric


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## BobWarfield (Jan 5, 2008)

We could easily build almost any engine in a weekend if we were to divide and conquer. How about a "pot luck" engine? An interested group designs it, each member is responsible for producing enough of one part for everyone, and then everyone mails each of the other guys the parts. Should be able to build a single part for an engine in a weekend, no? It would require some precision for it all to fit together at the end.

Just a thought...

Best,

BW


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## wareagle (Jan 5, 2008)

That is a very interesting concept. I would say let's go for the Stirling, and see how it works out. No sure what help I could be with the design of the project, but I could do drawings of the final design for publishing if need be.

Another thought I have had goes along the lines of a group project. My thought is to have the members here all make one part for an engine and then send all of the parts to a designated assembly point (maybe a show). After it is assembled, then auction it off and donate the proceeds to a charity. If there is enough interest, maybe build up two engines for the purpose. We could most likely even fund the site this way.


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## Powder keg (Jan 5, 2008)

Glad to see there is interest in my Idea. There are quite a few interested in Stirlings, but not that many actually building them? I thought a design that one person could build in a weekend might spark more builders to get off the puter and start making chips? Especially if they see that it can be done. Some of the designs are more complicated than I think they need to be. I have always used the KISS method when I'm designing and building something. 

I'm going to start throwing ideas out here and younz (that was for you Rick:O) can join in. I'll draw up some sketches and we'll see where this goes. 

Stirlings don't make much power. Usually, just enough to make them selfs run. For this reason they need to be friction free. I'm planing on using a brass cylinder and a graphite piston. I want to use graphite for the main bearing. I have never seen graphite used this way before. (might work?) I also want to use graphite for the seal for the displacer. I have machined graphite before and it is nice to work with. Dirty, but it machines really nice.

For the con rod bearings I want to use plastic with a groove machined in it to accept bent wire conn rod. These would be easy to machine and if reamed .001 over, they would be free running and light. This is where I was going with my "Eyes" topic. 

I have some plans that use that foam with cardstock on each side. I think this would be one option? it looks easy to work with. 

All Ideas are welcome, we all might find something usefull?

Later, Wes


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## BobWarfield (Jan 5, 2008)

WarEagle, I like the charity idea too. 

Anyway, I'm game to participate any way I can. I have drawing capability, a lathe, and a mill.

Sterlings are known to be finicky, so if we build a group project, we should do one that is proven. Otherwise, would love to see someone's "weekend" Stirling. 

Best,

BW


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## Powder keg (Jan 5, 2008)

I to like the charity engine idea. As well as the group effort idea. But I don't know if this will even work yet and I'd hate to build ten or more that don't work. I'm game for one built from a proven design. Steam might be a better option there, because these stirlings are known to be finicky. 

I'll post some sketches tomorrow.

Wes


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## Brass_Machine (Jan 5, 2008)

Powder keg  said:
			
		

> I to like the charity engine idea. As well as the group effort idea. But I don't know if this will even work yet and I'd hate to build ten or more that don't work. I'm game for one built from a proven design. Steam might be a better option there, because these stirlings are known to be finicky.
> 
> I'll post some sketches tomorrow.
> 
> Wes



Wes... (and everyone else)

I personally think that we should separate the "group build" charity engine from the "group design" LTD. I would like to do both. 

The way I see it, we could do group designs using ideas from all of our members. Working out the design etc. I have a few design ideas for engines I would like to do group designs on.

Then on the other hand, we could do group builds for various engines and donate them for charity. If the group designed engine works into a group build, then so be it.

So what do you think? We have 2 separate ideas going? Group Design and Group Build?

Eric


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## mklotz (Jan 6, 2008)

Building an LTD Stirling in a weekend is possible but something of a stretch.

If you're in a rush and not upset with the idea of using commercially available components, consider using a dashpot* for the cylinder-piston assembly. They come with a threaded fitting on the end so it's only a matter of drilling and tapping a hole, screwing it in and attaching the piston rod to the flywheel.

I used this approach in the Ringbom LTD Stirling I built







and it worked very nicely indeed. In this engine I used graphite for the displacer bearing and that worked well too. Graphite is self-lubricating and that's important for engines with such low specific power. Oil, even the lightest, can bring them to a halt.

Graphite rods are available as EDM electrodes from most of the usual suspects. Though fragile, it machines beautifully. 

Although mechanically simpler, I don't recommend a Ringbom Stirling as your first attempt. They're very tricky to design and quirky to run in an LTD configuration. Use a standard design where the displacer is driven off the crank.

-------------------------

* A dashpot is a mechanical damping device which develops a force proportional to velocity (as opposed to a spring force which is proportional to displacement). It typically consists of a cylinder of quartz glass or clear hard plastic into which is closely fitted a graphite piston. A valve is fitted at the top of the cylinder. By adjusting the valve the resistance of the piston to motion can be changed. (With the valve fully open it functions as a simple piston in a cylinder.) Despite the advent of PLCs for machine control, dashpots are still used in some forms of machinery and are available commercially.


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## Powder keg (Jan 6, 2008)

Hey Marv, I like that one:O) I know it's a stretch, to build one in a weekend, but I think it would be fun to try. Then if I suceed, I'll have my own LTD Stirling:O)

I have a few of those dashpots (mine aren't threaded so they have to be glued on) that I want to use eventually, but I want to keep the materials easer to get for this engine. I was planing on designing the engine around these, so they could be used in the future. That way people can see that they have different options. 

I'm glad that the graphite bearings worked for you. I haven't seen this used before. I like the skinny bearing post that holds up your flywheel. 

No I need to see if my scanner will work on my new puter?

Wes


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## two dogs (Jan 6, 2008)

Marv,
I like the idea of using dashpots.
Where did you get those pictured on your engine?

Thanks
Mark


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## Powder keg (Jan 6, 2008)

Does it matter much on these, what the top and bottom plates are made from? I've seen them run made with aluminum, brass, plastic, and I think stainless? I would imagine stainless would be the best? But they seen to work good on all these materials.

Wes


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## Powder keg (Jan 6, 2008)

You can get them Here

Wes


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## mklotz (Jan 6, 2008)

Powder keg  said:
			
		

> Does it matter much on these, what the top and bottom plates are made from? I've seen them run made with aluminum, brass, plastic, and I think stainless? I would imagine stainless would be the best? But they seen to work good on all these materials.
> 
> Wes



Aluminum is the most common material. I've never seen plastic used for the plates on an LTD and wouldn't recommend it. However, the displacer chamber is frequently made from plastic (PVC drainpipe in mine pictured above) because one wants it to be non-conductive so the temperature differential between the hot and cold end can be maintained.

Stainless would probably work. Brass would be pricey. For a first time engine, I'd stick with a proven material - aluminum in this case.


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## Powder keg (Jan 6, 2008)

Here is the one with the plastic top plate Marv. It will run on solar power. 

Solar Stirling

Later, Wes


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## two dogs (Jan 6, 2008)

Thanks Wes. I'll check it out

Mark


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## mklotz (Jan 6, 2008)

Powder keg  said:
			
		

> Here is the one with the plastic top plate Marv. It will run on solar power.
> 
> Solar Stirling
> 
> Later, Wes



Yes, but that one is heating the air via light absorbed by the displacer and re-emitted as infrared so, obviously, the upper plate must be transparent to allow the light to reach the displacer.

The more conventional design heats/cools the plates rather than the displacer piston so one wants a material with a reasonable coefficient of conduction.


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## Powder keg (Jan 6, 2008)

I think I have some scrap aluminum around here somewhere:O) 

What did you use for your displacer piston Marv? Nearly all of them use Styrofoam I've seen a couple that use that Styrofoam board with card stock on each side. I'm thinking the plain Styrofoam would be easiest? One had a piece of 1/2" wood dowel glued in the center to make the connection stronger. 

Wes


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## mklotz (Jan 6, 2008)

All my LTD Stirlings use styrofoam for the displacer. If you can't get sufficiently thin material, you can stick thicker stuff to a faceplate and 'machine' it down using a sanding disk in a Dremel held on the toolpost. The posterboard material faced with thin cardboard is unnecessarily heavy. I'd avoid it in an engine with such small specific power.

For the Ringbom, I made a 'tophat' shape with a wide brim of aluminum (drilled out to reduce weight) and glued that to the styrofoam disk. Be careful, many glues contain solvents that will attack styrofoam. Offhand, I don't remember what I used but it was probably Gorilla Glue or white woodworking glue. If you can't find a suitable glue, use double-sided carpet tape (everyone should have some of that in his toolbox).

Note that the displacer should not contact the chamber endplates at either end of its travel.


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## Powder keg (Jan 6, 2008)

So the top hat shaped aluminum piece fit in a hole in the foam? I imagine that there was a hole for the con rod to glue into? I'm thinking of gluing it and having a 2 piece con rod held together with some silicon tubing. If I can find some tubing small enough? 

Maybe it would be better to have a more mechanical conection between the two conrod pieces that silicone tube?

Thanks for your input, Marv.

Wes


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## Powder keg (Jan 6, 2008)

This one uses a small piece of Chain to lift the displacer up and down. This might look kind of neat when running? I wonder how good it would work? It would be easy to make the pieces. 

Wes


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## mklotz (Jan 6, 2008)

Powder keg  said:
			
		

> So the top hat shaped aluminum piece fit in a hole in the foam? I imagine that there was a hole for the con rod to glue into? I'm thinking of gluing it and having a 2 piece con rod held together with some silicon tubing. If I can find some tubing small enough?
> 
> Maybe it would be better to have a more mechanical conection between the two conrod pieces that silicone tube?
> 
> ...



Not "into" but rather the brim of the tophat was glued directly to the displacer disk. There's no provision for attaching a con rod. A Ringbom Stirling has a free-floating displacer that is driven to and fro solely by the changing gas pressures inside the engine. In fact, it is that rather remarkable fact that distinguishes a Ringbom from more conventional designs.

Silicone tubing is fine as a connector for such a flea-powered engine but sort of visually tacky. A thin bit of brass tubing and a drop of Loctite might make it look more mechanical. (Loctite breaks down when heated if disassembly is required.)


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## Powder keg (Jan 6, 2008)

Gotcha, Marv. I was thinking you had it inserted into the foam to make the connection between the con rod and the foam more durable. I was thinking a more conventional engine with a mechanical connection between the flywheel and the displacer.

I think the silicone looks tacky also. Are you talking about a really thin tubing that would flex back and forth as the piston went up and down? So it would be connected solid to the piston and the crank would have a bearing of some sort?

Thanks, Wes


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## mklotz (Jan 6, 2008)

Wes,

Maybe I misunderstood you. An LTD Stirling is unlikely to have the power needed to flex a piece of tubing (if that was your intent). The connecting rod needs to have a very low friction connection. Exactly how you establish that is a design detail but it must be as low weight and friction as possible.

Stirling engines come closer than most engines to operating on a true Carnot cycle. That means that their efficiency is given by:

efficiency = 1 - Tc/Th

where Tc and Th are the cold and hot temperatures respectively (expressed in degrees Kelvin). Taking:

Tc = 32 F (ice) = 273 K
Th = 100f (sun warmed) = 311 K

we have:

efficiency = 1 - 273/311 ~= 12%

So we're talking about engines that, at best, can only convert about 10% of the energy they receive into useful work. (In fact, it's absolutely astounding that they can be made to run at all.) With that sort of dismal performance, anything you can do to reduce friction is very important. Never attempt to lubricate an LTD. The viscosity of any oil will overpower the engine. That's why the self-lubricating quality of graphite is so desirable.


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## Powder keg (Jan 6, 2008)

mklotz  said:
			
		

> Wes,
> 
> Maybe I misunderstood you. An LTD Stirling is unlikely to have the power needed to flex a piece of tubing (if that was your intent). The connecting rod needs to have a very low friction connection. Exactly how you establish that is a design detail but it must be as low weight and friction as possible.



I think We misunderstood each other LOL. I understand how little power these have. You were talking about using a thin brass tube to glue the two half's of the con rod together, right? (to make it look better) I think the engines that use the silicon tubing rely on that joint to flex because the rod is fixed solid into the piston's. I couldn't see how the brass would flex unless it was very thin. 

The reason I want to use graphite in so many areas (main bearing, power piston, and displacer piston seal) is because you don't oil it. I want this engine to be maintainence free.

I can't wait to see what we come up with, Wes


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## Powder keg (Jan 6, 2008)

I have some plans that makes use a heavy plastic storage container to make the displacer cylinder. I think I'll use this method because it will be cheep and easy. The plans even used the bottom of the container to put ice in, so the engine will run backwards. A ring is cut out of the middle to make the cylinder. 

So far I've decided on Aluminum top and bottom plates. I'm going to use graphite for the displacer seal, power piston, and main bearing. I'll probably use a CD for the flywheel then in a later model, I'll use a flywheel machined on a CNC. (to make it look nicer) I'm thinking of making one piece that holds the power cylinder and the main bearing tower and maybe the displacer seal? It would bolt to the top plate. Then again they should bolt on seperatly?

I can't make up my mind on the details for the con rods? I want them to be durable and easy to build. I have seen them that are just strips of thin brass. They seem to work fine. Polished up they look nice also. I'm also thinking that with a engine this small they would last forever? Any opinions on this?

Later, Wes


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## Powder keg (Jan 6, 2008)

If they can make a LTD almost completely out of paper, I shouldn't have any trouble, Right?

Wes


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## rake60 (Jan 6, 2008)

Now *THAT* is the coolest thing I've ever seen!

Rick


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## Powder keg (Jan 7, 2008)

I haven't had time to scan my drawings yet, but I did get over to Walmart and found this. 





It's a 58 oz. acrylic canister. I'm planing on cutting 2" off the bottom for ice storage. Then I'll cut a .750" long ring off on my bandsaw for the displacer cylinder. I'll then sand the end's smooth. How does this sound so far?

Wes


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## Powder keg (Jan 7, 2008)

Here as a really rough sketch. I don't know how this will look?





The black parts will be graphite. I like the wire style con rods better. I think they will look better? The one for the power piston, will need a tab soldered onto the bottom. I think the bends in it will let you adjust the stroke some. 

I'm planing on some stainless screws to connect the top and bottom half's to minimize heat transfer. 

I can't decide on using a regular con rod on the power piston or a chain? I've seen several that used a chain and it looks neat while running. 

Wes


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## Bogstandard (Jan 7, 2008)

PK,
Why not use plastic rod for the spacers, something like delrin. That should stop most heat transfer. Or if you want to be a real cheapskate, pinch a couple of your grans plastic knitting needles.

John


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## Powder keg (Jan 7, 2008)

Plastic would work fine also. Just some shafts with the end's threaded? That way I could use brass screws on the top to Bling it up:O) A shiny engine runs better, Right?

Wes


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## Brass_Machine (Jan 7, 2008)

What sort of dimensions are you looking to do? Like the base... etc

Eric


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## Powder keg (Jan 7, 2008)

I bought 4 of those containers. I was planing on cutting one to get the dims I need and to see how it will workout. I think there is enough jar to get 4 or so cylinders out of it? I'll start getting some of the other dims soon also. I want to have a good plan of attack before I start. The power piston is .625". 

I'm probably going to use silicone to seal the cylinder. I'll make a bead round the rim and lay it down on some waxed paper to make the gasket. After the silicone has dried, I'll remove the paper, de-flash the silicone, and do the other side. Sound good?

Wes


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## Powder keg (Jan 8, 2008)

It took about 30 min with my bandsaw and belt sander to whip out a ring for the displacer cylinder. 




I also cleaned up the bottom piece to hold ice. 

The inside of the cylinder is 4.600" and the outside is 4.800" and the legnth is a little over .750". I also found some aluminum that is .085" thick. I'll use this for my top and bottom of my displacer cylinder. I mainly did this to get dimensions and to see how it was going to be to work with. On the weekend of the build I'll re-build everything.

Wes


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## Powder keg (Jan 9, 2008)

I found a [ame=http://www.youtube.com/watch?v=okYJV7giADI]Video[/ame] of a nicely made LTD. It uses wire Con Rods. 

Some of these engines have longer strokes on the displacer. Is there an advantage to having a long stroke to a short stroke here?

Thanks, Wes


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## Powder keg (Jan 10, 2008)

Thanks for the input birger. Do you have any pictures we can see?

Thanks, Wes


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## mklotz (Jan 10, 2008)

On my LTD I simply used Vaseline to 'seal' the displacer chamber. Remember that these engines will never see any temperatures that your skin couldn't tolerate so sealing need not be a big deal.


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## Powder keg (Jan 10, 2008)

Very nice job there. Thanks for the inspiration. What is that power piston made out of? It looks like some sort of plastic. That center bolt idea just saved me a bunch of work on my weekend engine. 

Thanks again, Wes


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## BobWarfield (Jan 10, 2008)

I'm probably over thinking things, but the center bolt seems like it would conduct the hottest part of the underside to the top, which is what you're trying to avoid in an LTD. As long as you're messing with that plastic anyway, I wonder if the center bolt could be threaded at both ends and the "nuts" made out of the plastic so it would stay insulated?

Nice looking LTD!

Best,

BW


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## mklotz (Jan 10, 2008)

While SS is a suitably lousy conductor, I would opt for a nylon bolt if you're going to do it that way.

A plastic piston may work at these low temperatures but be wary of operating the engine in sunlight.
Many plastics do not play nicely with ultraviolet.


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## cfellows (Jan 10, 2008)

From a practical standpoint, wouldn't the air inside the chamber swishing back and forth between the hot and cold sides do a lot more to equalize the temperature than the thermal conductance of the bolt?

Chuck


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## Powder keg (Jan 10, 2008)

On the piston I'm thinking of turning a smaller portion that will protrude out of the top and cross drilling it for my wire con rod. The graphite should be strong enough for this, right? If that wont work, I can make a small brass piece that threads in. It can be held in place with Locktite. 

The width of the ring I made for the displacer cylinder varies in legnth a small bit. Does anyone have any tricks for turning this in the lathe? I think it would be a mother bear to hold?

Thanks, Wes


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## Bogstandard (Jan 10, 2008)

PK,
Remember how I did my flywheels from plate. What you can do is stick your cylinder to a piece of wood, like mdf with say a hot melt gun or even double sided tape, don't use superglue, it is liable to cause a permanent bloom on the plastic. Then friction turn it, it doesn't have to be central, it will easily trim up. Choose the edge that is the squarest to the sides for sticking first.
Another way is to make a wooden blank in the lathe, do not make it totally round, just round corners will do (if you make it just a tiny bit larger than the ID of the ring, the ring will deform and grip itself onto the blank), slip the ring on and trim the ends. Doing it this way should ensure that the ends are square to the sides.

The lads on here should be able to suggest a few more methods to try as well.

John


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## shred (Jan 10, 2008)

Powder keg  said:
			
		

> On the piston I'm thinking of turning a smaller portion that will protrude out of the top and cross drilling it for my wire con rod. The graphite should be strong enough for this, right? If that wont work, I can make a small brass piece that threads in. It can be held in place with Locktite.
> 
> The width of the ring I made for the displacer cylinder varies in legnth a small bit. Does anyone have any tricks for turning this in the lathe? I think it would be a mother bear to hold?
> 
> Thanks, Wes


3-jaw working on the ID (jaws on the inside of the ring, crank the wrench the "wrong" way, indicate carefully if both sides aren't square) won't hold it? I've done that with bits of PVC pipe for other reasons a time or two. It's a little sketchy, but on plastic can easily be gotten-away with.


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## Powder keg (Jan 10, 2008)

Shred, This is pretty flimsy stuff. It's hard but there is no way you could hold it in a 3 jaw. I like John's Idea about jamming it onto some wood? Might have trouble getting hot glue off? Besides, I'd have to buy a gun. 

Thanks again for any input. 

Wes


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## Powder keg (Jan 11, 2008)

I dug out my face plate and will get a piece of wood screwed to it and I'll see what kind of damage I can do after work today. I'm planing on using the center bolt to hold it all together. I'll ether use stainless or plastic for the bolt? depends on what I come up with. 

Thanks again for all the input:O)

Wes


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## b.lindsey (Jan 11, 2008)

Shread's method does work...the key is patience...and very light cuts with a sharp edge on the tool bit. It takes a few more passes but leaves a very nice smooth finish also, thus avoiding the need for sealing gaskets as someone mentioned the other day.

Bill


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## Bogstandard (Jan 11, 2008)

PK,
Thinking about it, I would try Shreds method first, it is the easiest to try for the first attempt, should have thought of that myself, I most probably couldn't see the forest for all the trees. It is basically exactly the same as I am suggesting with the wood.

John


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## Powder keg (Jan 11, 2008)

I've got a really sharp tool here. I'll give shreds way a try right after work. 

Wes


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## Powder keg (Jan 11, 2008)

You guys are awesome!! It worked great!!! Quick, easy, and cheep!!! The ring turned out being within .005 in thickness all the way around. 

Wes


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## Powder keg (Jan 11, 2008)

What is a good way to polish the ends of this acrylic tube? I'm thinking just finer and finer emery?

Thanks, Wes


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## b.lindsey (Jan 12, 2008)

Wes, just curious as to why you feel polishing the ends is necessary?

Bill


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## Powder keg (Jan 12, 2008)

It's not necessary. I just have never worked with Acrylic and wanted to mess around with it some. Just to see what can be done:O)

Wes


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## b.lindsey (Jan 12, 2008)

Oh, ok. Well fine/very fine grit paper would work if done on a nice flat surface to avoid any contouring or rounding of the ends.


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## BobWarfield (Jan 12, 2008)

FYI, there are several techniques to polishing acrylic. You can use abrasives of various kinds. There is also a flame polishing technique. I haven't used it personally, but I understand it works pretty well.

Cheers,

BW


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## Powder keg (Jan 12, 2008)

I tried the heat method on my ice tray. It wasn't pretty. I think I need more practice and less heat:O) I'll stick to lightly sanding the edges of the cylinders to clean them up. I'll try to get some more pictures scanned and put up here tomorrow. I have the piston figured out. Still working on the base for the power cylinder and flywheel bearing tower. 

Wes


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## Powder keg (Jan 13, 2008)

Here are the sizes for the power piston. It is 1/2" long and the 1/8" brass rod will stick out about 3/16". I'm using .045 wire for the con rods on this engine. I'm using this size because of the Airpot cylinders that I have. I was thinking of using epoxy to glue them into the mount?





The gland piece will screw into the mount. I think the flywheel support should be fastened with a setscrew? That way it can be adjusted if needed?

How does this sound so far?

Wes


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## Powder keg (Jan 13, 2008)

Looking at some of the videos and pictures I think the conrod wire might want to be a little thinner? All it has to do is push the flywheel. Maybe some .030 wire would be better? This would save on weight. Any opinions?

Wes


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## Powder keg (Jan 13, 2008)

Anyone have any idea what kind of tolerance is needed on the gland for the displacer? I'm thinking of a .001" over reamer would be a easy way to do this. Would that be too loose? Should I ream it to size then polish the shaft a bit?

Thanks, Wes


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## Powder keg (Jan 15, 2008)

I'm planing on using plastic for the con rod bearings. I was going to machine some tubes with a groove on the outside. These would be screwed to the crank and not turn. The wire would just spin on the plastic. This should work good right?

Thanks, Wes


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## BobWarfield (Jan 15, 2008)

I'm getting curious about machining some graphite while reading this thread. I know it is very commonly used with EDM machines. I'm wondering if there are grades or sources of graphite that is especially machinable. I've never messed with a very big chunk of the stuff.

Best,

BW


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## Davyboy (Jan 15, 2008)

Hi Wes, I had the bearings on my Simple Simon too tight, and it wouldn't work. My crankshaft was made from hand-straightened wire, so it had a bit of runout. The crankshaft bearings were rigid in the frame, they worked only after I let them "float" with the crank. (Slopped'em out a bit  ) This guy has to turn over easily with no binding. As for the weight of the con rod wire, I believe that balancing the weight is more important than mass, at a reasonable scale of course. Just my .02c


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## Powder keg (Jan 16, 2008)

I've made a couple graphite pistons. The best way I've found to get a good size is to turn the piston down to a thou. bigger then file it down to with in a couple tenths. Then sand it down with newspaper. This will give a really good finish. 

I was planing on making the bushings a running fit in the con rods. 

I think that the less rotating mass you have the less weight there will be on the graphite bushings. This will mean less friction. 

Wes


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## Powder keg (Jan 18, 2008)

I started night school to learn CNC's and I am thinking of making some of the parts there. That would partially void the weekend engine idea, but I'd have another engine:O) I'll still post the plans for download:O) I have the top and bottom plate drawn up and will try and machine them soon. I am also drawing some of the pieces. 

Wes


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## Powder keg (Jan 18, 2008)

I have a couple pictures drawn up on Mastercam and I would like to make them into Jpegs or something that everyone can look at. Is this possible?

I figured out a way to hide the bolt's that goes through the center to hold the two half's together also. I about have this drawn up. I am planing on cutting this part out on the CNC. I'll tke some pictures and hopefully some video:O)

Wes


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## 1Kenny (Jan 19, 2008)

Hey Wes,

Is there something like a Mastercam reader we can down load?

kenny


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## Brass_Machine (Jan 19, 2008)

Powder keg  said:
			
		

> I have a couple pictures drawn up on Mastercam and I would like to make them into Jpegs or something that everyone can look at. Is this possible?
> 
> I figured out a way to hide the bolt's that goes through the center to hold the two half's together also. I about have this drawn up. I am planing on cutting this part out on the CNC. I'll tke some pictures and hopefully some video:O)
> 
> Wes



Wes... I am not familiar with mastercam, what is the file type when you save it? I may be able to convert it for you. OR look to see if the is an export option OR take a screenshot with mastercam open.

Eric


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## Powder keg (Jan 19, 2008)

I'm fairly new at this. How do you do a screenshot? I can save the files as DWG's if that helps? I've only had one night class so far on cad and I have a lot to learn. Mastercam is a program made to design a part and then machine it. From what I've seen, It's not a super Cad program, but what it does on the CNC end is awesome! I can machine a part on my computer before I even get the mill warmed up.
	

	
	
		
		

		
			





Later, Wes


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## Brass_Machine (Jan 19, 2008)

Sent ya a PM

Eric


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## Powder keg (Jan 20, 2008)

Anyone have any ideas on holding the styrofoam displacer cylinder, without smashing the crap out of it?

Thanks, Wes


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## Powder keg (Jan 20, 2008)

I'll give that a try. Should there be something in the middle to reinforce where the displacer shaft enters the foam?

Wes


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## Kactiguy (Jan 20, 2008)

Wes, I built a displacer out of that blue insulation foam that they put on houses. It was very lightweight and very easy to shape with sandpaper. I stuck some on a mandrel once and spun it on the lathe, then shaped it with sandpaper. Seemed to work fine for me.


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## Powder keg (Jan 20, 2008)

I have most of the pieces drawn up now. Once I figure out how to post them here I will. I have the displacer cylinder done. I've decided to CNC some of the parts. The top and bottom plate, The flywheel support, and the flywheel will be cut out on the CNC. I'll start to post pictures in the build log section of this engine. 

Wes


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## Brass_Machine (Jan 20, 2008)

There ya go Wes


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## Brass_Machine (Jan 20, 2008)

Posted for Wes


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## Powder keg (Jan 21, 2008)

Thanks! I have all the toolpaths figured out for the flywheel pedistal. I should be able to machine it at school on Tuesday. I'll try and get a video:O)

Wes


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