# Redesigned "Leakproof" Elbow Engine



## Ken I (Apr 27, 2012)

Here's the completed elbow engine.







And a "prequel" video of it running - I piped up the exhaust so you can hear it without the exhaust noise - but the clatter you can hear is rain on my IBR workshop roof.

You can see the slow running hesitancy at the tight spot which I am hoping to run out before posting a better vid later.

http://www.youtube.com/watch?v=X0-vCBC0KkU&feature=youtu.be

Edit: It now has about 12 hours of run time and will tick over at 50rpm - I'm hoping for 30 or less once the tight spot works itself out.

I set out to design an Elbow Engine that would address some of the problems of the conventional axial flow designs by changing to a radial flow via axle porting. The use of a stiffener joint and slightly flexible "elbows" gets away with most of the alignment issues.

The pistons also rotate on their axles to further reduce running friction as does the inclusion of ball radial and axial bearings.

"O" ring sealed pistons and lip seals on the axles constrain any leakage to the exhaust.

The only oil it "throws" is what makes it past the piston "O" rings and is very little - typically the motor will run for 2 hours before the build up of oil at the cylinder throats becomes heavy enough to start throwing it about.

The G.A.





You can follow the build thread here :-

http://www.homemodelenginemachinist.com/index.php?topic=16790.0

Special thanks to: Captain Jerry, John (Bogstandard), Marv (mklotz), rustyknife, foozer, cutajar, miner49r, dsquire, Arnoldb who all passed comments, made suggestions or simply offered up encouragement  it is all appreciated.

I am trying to upload the design drawings but the uploads section is not cooperating, hopefully Bob will get it sorted, he normally does.

The file will contain a 2D Autocad *.dwg & *.dxf, a single sheet *.pdf and a *.doc file containing over 40 WIP photos and instructions for anyone who's interested.

For now I have attached only the *.pdf because of file size restrictions.

Regards
      Ken


View attachment ELBOW6.pdf


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## kustomkb (Apr 27, 2012)

Beautiful job Ken!

Thanks for the great design.


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## b.lindsey (Apr 27, 2012)

Ken, that is one of the best versions of the elbow engine I have ever seen...extremely creative and obviously no sacrifice (indeed improvements) in performance. A one of a kind to be proud of for sure!!!

Bill


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## Ken I (Apr 29, 2012)

Here's a "prettier" video of it running.


http://www.youtube.com/watch?v=WHhnuLk15SY&feature=youtu.be

Ken


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## picclock (Apr 29, 2012)

That is one very sweet engine - I shall have to stop myself starting one as a project until I have finished the stuff I have on the go. Truly an excellent rethink of the leak issue. 

Not sure about the music in the second video .. . ;D

Best regards

picclock


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## ref1ection (Apr 30, 2012)

Extremely nice rework of the elbow engine and I like your choice of music. ;D

Ray


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## Ken I (May 1, 2012)

I have posted the drawings as a *.zip file under the downloads section if you are interested.

It contains an Autocad 2D *.dwg & *.dxf file with each part drawn in a different layer / colour.

There is also a single sheet *.pdf of the same.

At this time the downloads section will not accomodate the large (5MB) *.doc file of build notes and photos.

(The download limit seems to be 2.5MB not 25MB as stated)

If you would like a copy of the *.doc file, send me a PM.

Regards,
      Ken


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## steamer (May 1, 2012)

Nice Engine Ken!

Love the video!  Now your going to tell us how you got those camera pans and zooms right?

 ;D

Dave


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## doubletop (May 1, 2012)

I like that Ken, great job

Pete


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## Noitoen (May 1, 2012)

New design 45º elbow engine. :hDe:


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## Ken I (May 1, 2012)

steamer  said:
			
		

> Love the video!  Now your going to tell us how you got those camera pans and zooms right?



I was wondering how long it would take someone to ask that - and I'd have bet a dollar to a donut it would be you - I also suspect you already know the answer.



			
				Noitoen  said:
			
		

> New design 45º elbow engine. :hDe:


It's possible ! I think ? Maybe ?

Ken


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## steamer (May 1, 2012)

Ken I  said:
			
		

> I was wondering how long it would take someone to ask that - and I'd have bet a dollar to a donut it would be you - I also suspect you already know the answer.
> It's possible ! I think ? Maybe ?
> 
> Ken




 ;D.....OK so are you going to show it! or do I have to get rough with ya *knuppel2*


 ;D


Dave


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## Ken I (May 1, 2012)

O.K. I'll 'fess up - just give me a while to take a photo of the set up.

Ken


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## Ken I (May 2, 2012)

Steamer,
        Here's how I did the camera pans :-






I mounted the camera on a Yaskawa Motoman MH6 DX100 6-Axis industrial robot (one of my showroom machines) normally used for MIG welding (note weld gun tied up out of the way).

Programmed the camera flyby - a very quick and dirty program (10 points) but it worked just fine.

I just played the music in the background as my editting suite is not on speaking terms with my computer for some reason.

Ken


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## steamer (May 2, 2012)

That's awesome Ken! I want one of those...for the camera flybys..... ;D

Actually I loved the music!

Dave


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## Captain Jerry (May 2, 2012)

45° Elbow? Not that easy. 135° is a piece of cake but acute angles, while theoretically possible, are not really practical. More than 135° also gets into the silly stuff. I have been there!

Jerry


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## Ken I (May 3, 2012)

Captain,
      Oh Yeah ! - I did a quick cut and paste on Autocad and quickly realised its either going to be a heap of troubles or is flat out not going to work.

Plus a whole new slew of frictional problems.

Possible yes, practical - no.

Ken


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## steamer (May 3, 2012)

Ken I  said:
			
		

> Captain,
> Oh Yeah ! - I did a quick cut and paste on Autocad and quickly realised its either going to be a heap of troubles or is flat out not going to work.
> 
> Plus a whole new slew of frictional problems.
> ...




Based on the fact that two master engine makers can build an Encabulator.....I'd bet they can do a 45... ;D

Dave


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## Ken I (May 6, 2012)

Ohhhh..... Captain Jerry - did you hear that - first a compliment then a gauntlet is tossed down.

Sorry Steamer but I'm not biting - but I did draw it up.....






Note what happens - the nominal stroke is 30mm @ 90° - the PCD of the cylinders - but when you open the angle to 135° the stroke is radically reduced to 12.53 so the overall "power" of the engine is more than halved - but almost all the frictional problems stay the same.
When you diminish the angle to 45° the stroke increaces to 54.85mm but frictional problems increace. I very much doubt that the pushing cylinder can drag back the exhausting cylinder at an acute angle.

An elbow engine sails perilously close to self locking frictional limits at the best of times.

I believe (I haven't done the math) that deviating from 90° will very rapidly push you "over the edge".

Sorry Dave but that's one challenge I'm not going to pick up.

Regards,
        Ken


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## steamer (May 6, 2012)

Hey guys,

Ken, I expected nothing less than a full engineering analysis, which you provided.  :bow:....The fact that you laid it out tells me you were thinking about it!.....Thanks man!


I will try to make myself worthy in future of the genius that is Ken and Gerry! :bow: :bow:

Dave


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## Captain Jerry (May 6, 2012)

Yeah, I heard it. One of these days, after I tame the donkey, I will try my hand at an elbow.

There is no good reason to even consider an acute angle, but I actually like the oblique angle numbers. If you consider the bore/stroke ratio (10/12.3) is much closer to normal in the 135° configuration, with all of the benefit of reduced piston speed, better ring and bore wear, etc. A few years ago I built an similar engine with a 108° angle and it ran quite well in spite of my limited equipment and limited experience at the time.

It is next to impossible to experiment with the range of possible angles for an elbow type engine due to the number of parts that need to be modified. BUT! The geometry of the elbow engine is identical to that of a swash plate engine. Just imagine an invisible swashplate that is set at a 45° angle to the pistons of a 90° elbow engine at the center of each elbow.

I have done a fair amount of experimentation with that type. It is easy to change the angle of a swash plate and it can be done by changing only one simple part. I have used swash plate angles as close as 15° that correspond to a 165° elbow but I have settled on a 20° swash plate angle as a good compromise. That is not far from the 22.5° geometry of a 135° elbow.

So many options, so little time.

Jerry


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## Noitoen (May 6, 2012)

When I said 45º, I meant bending the rods by 45º from straight like your 135º example. That's (about) the angle of many hydraulic swash plate motors/pumps. I suppose the real 45º motor you drawn, would work ok as a motor but not a pump.


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## Noitoen (May 6, 2012)

:ideaon´t forget "spring return assist"


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## Ken I (May 6, 2012)

Captain, Noitoen - the 135° should work - I'm pretty sure the 45° won't.

I had a brief go at modeling the friction but the maths doesn't gel.

Well after a few beers one shouldn't attempt calculus.

"DON'T DRINK AND DERIVE".

Ken


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## steamer (May 6, 2012)

Looking at the 45 layout Ken, I think by inspection it will violate the old 2/1 rule.

If you want a derivation of the 2/1 rule and a self locking bearing I can do that.... but I'm in the throws of washing machine surgery right now....considering the quack doctor operating.....I don't have a lot of hope for the patient! :

Dave


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