Radial completed

[windstuffnow]

  Completed with the exception of the lathe test.  So far it was a sucess, very little cogging as I expected and the iron drag is actually much less than I had expected.  The force needed to start turning it was 2 inch/lbs or 300 grams of force at 3.5" arm.  

  I plan to go back out tonight and set it up for testing and I'll post the results.  Here is a picture of the unit with the rotor off...

  I ended up with 10 turns per coil opting for a 200 rpm cut in speed.  After some thought I figured 100 rpm would be a bit slow.   It's purpose isn't for wind, directly, but for a small stirling engine.  Indirectly, it would work quite nice on a wind genny.

  Fun project !  My curiosity has been taimed and it was quite successful overall.  Have to finish up some other work then I'll complete the stirling for it...

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[RogerAS]

Windstuff,

Please oh please keep us updated about your Stirling. I've taken a very keen interest in these lately, and built a small walking beam model myself.

Pepa, you could give us a few teasing morsels too! :-)

Can you provide a few detail in advance of the construction?

Axiously awaiting,

[pepa]

ED, great stuff as always, i enjoy your work as much as you do.

Rodger, i bow to the master and he will show us the way. pepa

[windstuffnow]

  Spinning the radial in the lathe here is what I came up with... I only ran it at one speed to keep it simple and get an idea of what it would do...

Running at 400 rpm charging a 12v battery.. 3.5 amps at 14 volts 49 watts

I decided since it was quite easy to chuck the rotor in the lathe and the backing plate would pivot to go ahead and check the input as well.  My scale read 2500 grams at 3.25" which comes out to 1.49 ft lbs of force and at 400 rpm was about 84 watts so its about 58% efficient at that speed.   After calculating copper losses ( about 7-8 watts ) the rest has to be iron drag.  So it's loosing about 27 watts to the iron.  Not super efficient by any means but I mostly wanted to see if the odd pole/coil count would be offset enough to reduce the coging.  The cogging is quite insignifcant.   I think using some M19 steel to make up the stator stack the iron loss could be reduced considerably but not completely.

  As it turned out this was a really fun and quick project which merits a larger one in the future!

  RogerAS... the stirling is simply a single cylinder with a 2" piston.   I plan to run the alternator at 1/2 the speed (2:1 reduction).  It's not for anything specific, just a fun project.   The 6" bore engine is still in the drawing stages but I have most of the parts and material collected for it.   A few more parts to design for it then that will become the project that requires "stolen time" for awhile.  The small one is a test base for an odd drive I'm working on instead of using a crankshaft.   If the small one proves out then the path is clear for the large one... These are nothing compaired to a long term project I've been working on...

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[windstuffnow]

RogerAS, I talked with some guys at the local racing machine shop where I had lots of stuff worked over way back when ( hard to believe some of the old die hards are still there - great guys ).  Anyway, I asked if it was possible to get a cylinder sleeve for a 6 or 8 inch.  After looking at me a bit strange he boped over to the book, licked his thumb and buzzed through a few pages and said "yup, heres one".  Looking at the picture and drooling I told him I had to own one.  He looked up the prices on the 6 and 8 and asked if I would like to sit down first.  The 6" was actually affordable and I bought one (sitting here waiting for me to start)  the 8" was a bit out of reach.   The sleeves are long enough to make 2 engines or a twin... should be interesting.   They are cast and rough machined so they require a heavy hone to open it up a bit and a finish/sizing hone to fit the piston.  I'll most likely machine my own piston because of the seals I'm using instead of rings... It's gonna be a fun project!

 

[pepa]

you missed your calling as a mistery writer Ed, you always keep us in a state of suspense. i have been pulling the piston rods from a stock of small junk lawn mower engines to use in my multi-cylinder engine. working out the crank shaft was not as bad as i thought but still a lot of work. pepa

[hiker]

nice work....

whats the next one---a big brake drum mill?

[windstuffnow]

 Pepa, I have a couple ideas for using smaller pistons to make up the equivilant of a larger piston for more power.  Another idea to get rid of that pesky inefficient power sucking crankshaft.  It looks good on paper and a cobbled together model proved the theory.  But will it work with a heavy load...

.

[windstuffnow]

That thought has crossed my mind hiker !  Not sure...

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[Countryboy]

Ed (or anyone else),

  Find a semi truck repair shop.  They have to resleeve the semi engines every once in a while.

  I have a half dozen aluminum pistons our of the farm semi when we rebuilt it.  They are 5.5 inch diamter - a used sleeve for that could probably be found in a dumpster.  (Why the heck did I save them again?)

[pepa]

hi windstuff ed, just as a bit of information, do to a problem i have i am on oxigen 24/7 and have a large supply of 165 liter tanks in the garage that are swapped out on a regular basis. these tanks are heavy alun. and 24 by 41/2 inches od. some of the tanks come with a od of 4 inches and would fit into the larger size with a good fit with seals. i talked to my supplier and he is checking to see if i can get some of the tanks that they cannot refill any more , these tanks should make nice cylinders and pistons. i am also wondering if some of the old military brass shell cases would work, your thoughts, pepa.

[pepa]

that idea would be great, i'll bee looking over your shoulder when you get the time. how do you sleep at knight, my wife thinks i am possessed. pepa.

[windstuffnow]

  I never gave it much thought, I have a friend that is still twisting wrenches in a truck shop.. I'm going to have to bend his ear a bit...

Thanks for the tip!

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[tecker]

One thing I ve noticed From missen around with Ceiling fan motors that might apply here . The  inner fields are very close to the outer fields when it comes to output .So a deeper cut or slant pole offset deep in the core would give space for copper.

[RogerAS]

Ed, Pepa, All,

I've been considering a hunk of 6" irrigation aluminum pipe for the power cylinder for a large engine. A sortta local scrap yard gets all kinds of oddball metal and a recent visit revealed a pile of tornado damaged irrigation equipment. I wonder if aluminum would be durable enough, and this pipe is seamed so more work would be needed before it was suitable.

The diesel engine sleeves sounds interesting too.

My model engine showed me some interesting things. I used and undersized, according to specs, piston/clyinder setup but it still ran. Replaced with the "right" size the RPMs went up and the startup heat needed went down. Both were the same in terms of stroke length, and both were glass tubes/graphite pistons. So what I think I've learned is that absolute size isn't as important as is smoothness of operation and the sealing of the working fluid. So maybe increasing stoke length with a smaller diameter cylinder would be fine. However I wonder if increasing stroke length would induce more friction.

Of course a longer stroke would mean a second crank throw in my Gamma configuration. This isn't a deal killer, and might be even better in the long run. With a second throw I could vary the timing and from what I've read this can be a real advantage in terms of overall operation.

Regenerators are something else I'm looking into. My current cylinder has about 1.25" of "dead" space at the bottom of the stroke and I've considered filling that space with loose stainless mesh or very fine copper wire. From what I can gather this one feature is really a big performance improvement. My current engine comes apart easy enough to make such an experiment fairly easy.

My eventual goal is to build an engine large enough to drive either an alternator or DC motor from waste heat from my wood fired convection furnace. If I could get 100-200 watts all winter long I would be extremely happy. My concern is that when I scale the engine up the heat requirements would also go up. Reserch in this field is hard to come by.

I've looked into the Rider-Ericsson, and other "old time" Strilings, and if those guys could build real world working engines surely we "modern" folks can do at least that well. Heck, if I could get a set of measured drawings I'd be more than willing to build a replica of one of those engines.

Anyway, glad to hear I'm not the only "infected" subject of the relm. :-)

[scottsAI]

Hello RogerAS, windstuffnow,

Stirling engine is a huge interest here too.

Looking at options for a 2kw solar panel, cost $12,000.

Figured could build a 3 hp engine for that much. Even hiring out the machine work.

At this point I had a nice paper design of a two cylinder single piston linear Stirling engine.

Later found a design just like mine. Continued looking.

Much research I found:http://www.bekkoame.ne.jp/~khirata/academic/simple/simplee.htm

For a reasonable sized engine I needed a working pressure of over 200psi! Wow!

Not to let that stop me then came across this:

http://www.ent.ohiou.edu/~urieli/stirling/simple/regen_simple.html

1% reduction in regenerator effectiveness results in a more than 5% reduction in thermal efficiency h.

At this point found the Area of working pressure verses the piston movement Area is directly proportional to power and efficiency! Yikes! This has become very very difficult.

Not impossible. This is the type of thing I usually go after. Except, working on a Zero Energy Home design. 2kw solar power is the real goal here, must remain focused.

You can find lot's of Stirling models out there, and that is just what they are; toys.

Getting a Stirling to spin seems to be easy, getting power out is NOT!

At this point I decided maybe a Tesla Boundary Layer Turbine would be better.

http://www.stanford.edu/~hydrobay/lookat/tt.html

Looks easier to build?

Many toy builders out there. Many serious attempts have been made, couple have success in a working engine then seem to go into business building it, without publishing anything.

I didn't understand the difficulties in designing a Stirling engine... I do now.

I will be watching your efforts, assuming you chose to publish:-)

Have fun,

Scott.

[windstuffnow]

  Look for the Rider Ericsson "1/3 scale" model plans.  Those engines weren't very powerful but they ran good and pumped water 24/7 for years.  They were cast from heavy cast iron which wasn't very suitable for heat transfere through the displacer hot end.  Now a days we can get thin stainless.. durable and heat resistant.  Also, they didn't use a regenerator.   The Robinson engine was also another good running engine.   I remember seeing some scale drawings of the Rider on the web.   I believe they are in one of the Steam & stirlling books as well... I believe you can also purchase a "kit" for the scaled Rider with complete drawings.  

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[BigBreaker]

Windstuffnow:

I don't see the return path for the magnetic flux opposite the rotor pictured.  Does the stator have iron behind it?

[windstuffnow]

  The stator is made up of 8 steel plates laminated together.

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