# Swinging Elbows



## Captain Jerry (May 7, 2012)

Open for discussion

I'm not ready to build this yet but I think it is possible. I just thought I would put it up here for discussion.

Jerry







View attachment variable elbows.pdf


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## maverick (May 7, 2012)

As the angle between the two cylinders approaches zero, there is little or no rotational force. It might work down to 20 degrees or so.
 Interesting concept at any rate.


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## Ken I (May 7, 2012)

Captain,
      Firstly four cylinders will not work (OK maybe it was just for illustrative purposes) at 90° A'la elbow engine.

With 4 cylinders at 90° elbow engine style at the 90° rotation you reach a point of singularity - the cylinders simply tow each other out and lock. (Try it with one piston pair in place or look at my vid on this and you will see what I'm getting at.)

[ame=http://www.youtube.com/watch?v=eqdyO4FcFS4]http://www.youtube.com/watch?v=eqdyO4FcFS4[/ame]

Ignore my voiceover comment about 5 cylinders I was mistaken - but 4 won't work (at 90°)

At the increaced angle it should be O.K. down to about 110° and at 180° (in line) there is no stroke.
So I'm guessing you want to be able to swing it from 180° (zero stroke = won't run) to 90° (stroke = pitch circle diameter of cylinders) then you need 3 or 5 cylinders.

Frictionally a 6 cylinder is rather like two threes working together - from this it follows that cylinder numbers should be "prime" 3, 5, 7 etc.

Obviously you need some sort of joint at the elbows and the cylinders need to accomodate the changes in stroke occasioned by the change in angle.

Interesting exercise just thinking it through.

I've sent you a PM on my build notes.

Ken


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## Captain Jerry (May 7, 2012)

Ken

So far, it is just a thought exercise. If it ever gets built, it will be used to test some ideas and options that are often talked about but never proven or tested and maybe some ideas that haven't been talked about yet. This frame idea will not be able to test all ideas but it should be able to answer the question of the range of possible angles between 90° and 180° and in the process give some answers about flexible joints.

Your engine clearly proved the axial valve and seals can eliminate the oil spray. The rigidity provided by the center bracket will be more obvious with time. I predict that time and use will allow the seals to seat without undue cylinder wear.

I think this design will use the axial valve but will not use seals or bearings. I expect that it will leak a little air and oil, but not as much as the face valve of the original design.

It will not be reversible. The complication of additional air passages would cloud the issues and reversing is well understood.

I think it will use cast iron for the pistons and have ball joints at the flex point but could also use half/lap or knife/fork joints.

The cylinders will be either aluminum or cast iron turning on a polished steel center shaft. If the cylinders are aluminum they will have cast iron or bronze bushings.

I don't think there is any doubt that jointed elbows will work. There is a wide range of opinion on the range of angle. My bet is that it can be made to run well past 160° after break in.

If there are any other ideas that need testing, please speak up. There is plenty of time. This isn't going to happen tomorrow.

Jerry


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## Captain Jerry (May 8, 2012)

This seems like a small change but could be important. By putting the pivot in line with the cylinder where the piston is at TDC, it keeps the piston/head clearance constant. When the pivot is centered as in the previous model, the piston/head clearance increases as the stroke decreases ... a bad thing!

Jerry


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## Ken I (May 8, 2012)

Captain,
      See attached *.pdf - I found that swinging on the corner is lousy for geometery - but swinging on the intersect of the inboard cylinders works well and keeps the dead length constant.

However that won't permit any form of stiffener (other than an adjustable one perhaps).

Swinging on the centreline intersect would permit some sort of hinged stiffener - but the redundant volume in the base of the cylinders increaces with swing - lousy for efficiency with steam or compressed air (wouldn't matter for hydraulic).

2c
   Ken 

View attachment ELBSWING Model (1).pdf


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## Captain Jerry (May 8, 2012)

Ken

I see you have been through this thought process before. What else did you discover?

I think I like the pivot on the inboard cylinder intersect. That is what I was trying to say but used too many 
words. I guess I will just have to rely on the wonders of modern pharmacology for the stiffener.

Jerry


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## Ken I (May 8, 2012)

Captain,
      You gotta love them little blue pills. Knew a guy who took too many - then needed a whole tube of Deep Heat for his arm.

If you put the pivot point any closer inboard than the cylinder intersects, the reverse happens - the pistons descend further into the cylinders exacerbating the dead length problem - so I guess the cylinder intersect it is. (I mistakenly thought you were going to pivot at the corner edge of the cylinder - which will keep that constant - no good purpose in that - that I can see.)



			
				Captain Jerry  said:
			
		

> I think I like the pivot on the inboard cylinder intersect. That is what I was trying to say but used too many
> words.


No you explained it just right - I'm the idiot who didn't read it properly.

As regards the stiffener - I removed mine from my elbow engine and it still turns over by hand and runs - pretty much the same as with it.
It sounds a little more "grumbly" so the reaction forces are probably springing the 90° slightly and my "springy elbow thingies" are taking care of it but at the expense of some increaced side load on the pistons.

That said your "hinged elbow thingies" should take any of that kind of deflection in their stride.

What else have I found - Hmmm - you keep sparking me so keep the ideas flowing.

Regards,
       Ken

PS - in my build notes - my comments on the number of cylinders and friction etc are on page 20-21 - to save you wading through all the guff.


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## Captain Jerry (May 9, 2012)

^^^^ VIDEO ^^^^

I think I have the geometry worked out, at least good enough for Alibre'. The number of cylinders is just for the convenience of comparing piston positions at 180&#176; apart. I know I could do that with a six cylinder design but I think I am leaning towards a five cylinder design.

Alibre' has no problem with rotating 4 cylinders, but strangely enough, it can't handle just two cylinders very well. And there is no friction in Alibre' so it is a purely geometric issue. It will rotate through almost 180&#176; before locking. I think I have an answer but I want to investigate before I say something stupid.

Here is a screen capture of the thing working. The articulation and the rotation are manually controlled so I can't do them simultaneously.

Jerry


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## Ken I (May 15, 2012)

Captain,
      Not many people chipping in to this thread - I think you've scared them off.

Further to my comment about your elbows taking flex in their stride - I was wrong - the flex will be at 90° to your hinges - but since the flex will be very little I would presume a little play in the "hinges" would take care of it.
Alternately your suggestion earlier of a spherical joint - but that approach will almost certainly have limited articulation.

Ken


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## Noitoen (May 15, 2012)

I'm here. If you search deep enough on earlier posts, you will see that I've being wondering about flexible elbows on these engines for a while. Swinging elbow idea is new to me but I'll follow along. ;D


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## maverick (May 15, 2012)

With the swinging geometry, You also get a variable volume / compression ratio effect.
 An opportunity? or just another worm in the can? You decide. Maybe the reason for the silence 
 is guys like me scratching their head with both hands and nothing left to type with.

 Regards,
 Maverick


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## Captain Jerry (May 15, 2012)

Ken

I'm not ready to build this yet but I can still think about it. I am still leaning towards a spherical joint for two reasons. 

  1. I have worked out a method that is extremely simple to make and they have about 270° of articulation. An example 
    of this joint is shown on my three cylinder opposed wobble plate engine shown here. These joints are articulating 
    40° but that is nowhere near the maximum available.

    [ame]http://youtu.be/YR7SH5YDQGY[/ame]

  2. Half lap joints like I showed in my 3D model are easy to draw but very difficult to machine with the same accuracy and 
    the cantilevered pin can add a point of binding.

Knife and for joints are better balanced for thrust forces than lap joints and would be my second choice. The most important point for the joint is that it must have very little slop. To be able to change the relative angle, it must be able to articulate, but any slop will lead to alignment problems and binding.


Noitoen

I'm glad you are watching and still interested. Yes, there has been plenty of discussion of flexible elbows but as I see it, there is a difference between "flexible", (think RUBBER TUBE), and articulating, (think hinged). A fully flexible elbow could allow the two pistons to be forced out of the same plane, which screws up the geometry of this engine. If the joint only articulates, the two pistons must remain in the same plane and the two cylinders must also remain in the same plane. This is the single most important constraint in the geometry of this engine. Ken's center axis joiner assures the coplanar arrangement of the cylinders on his engine and even though he has said that it didn't change things much when he took it off, I think it was important in establishing the coplanar relationship.

Maverick

Variable volume/displacement is an important part of this design. As the engine articulates from the 90° orientation to 180°, the displacement changes from a maximum value ( depends on the bore and the PCD of the cylinder arrangement), to ZERO. If the "swinging elbow engine" can be built accurately, and is running freely at 90°, it should accelerate as the angle is increased up to some angle as the displacement is reduced. If there were absolutely no friction, it would continue to increase in speed dramatically, approaching infinity as the angle approaches 180°. 

But of course friction does exist and as the displacement is reduced, so is the power and somewhere along the path, friction will begin to slow the speed and the engine will run out of power but the point where that happens is very dependent on the materials used and tolerances maintained. There have been several estimates as to what the maximum angle is that can be achieved. That could be seen by some as a challenge.

The more I think about this thing, the more anxious I am to build it. I may not have the skill or the equipment to do it justice but It is worth the time to try.


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## steamer (May 15, 2012)

I'm here also....got my eye on you two !   ;D

Dave


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## Ken I (May 16, 2012)

Captain,
      Another problem with the "hinge" elbow - at 180° (in line) they could rotate to any position and then be unable to bend.

O.K. I know that doesn't make a lot of sense - bear with me - as you approach 180° the propensity for the two pistons to rotate increaces - thowing the alignment of the hinge out of whack - as it bends it will realign itself - but at some point it will introduce self-locking forces. Perhaps the motor will fail to run because of overall frictional limits before this particular limit is approached - but I thought I would give it a mention.

Regards,
      Ken


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## Noitoen (May 16, 2012)

At 180º the engine wouldn't rotate anyway.


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## Ken I (May 16, 2012)

Noitoen, I am aware of that - but at 180° if you were to rotate it by hand the elbow hinges would would be free to rotate out of synch making it impossible to change the angle without first lining them all up by hand first.
Similarly as you approach 180° (I know the engine is going to come to a halt somewhere as you approach 180° as the stroke diminishes to zero) there will be a tendency for the elbows to try and rotate the hinges out of synch which will eventually reach a self locking condition - what I don't know is whether or not this will be the limiting condition.

If as Jerry thinks, the engine will run to about 160° it probably won't be.

Ken


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## Captain Jerry (May 16, 2012)

Ken

I think that while the pistons would be free to rotate in the bore, at 180° there is no force that encourages that. The pistons then rotate WITH the cylinder. When the cylinder has rotated 90°, the hinge pins are locked in relation to the base hinge. This is another of those questions that will only be answered by building it. 

Jerry


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## Captain Jerry (May 16, 2012)

This is the joint that I think will work best for this experiment. It provides plenty of articulation in the XY plane as shown here. This is a video.





With a very slight modification, it will also allow about 15&#176; of articulation in the YZ plane as well. Rotation of the ball member has no effect on the articulation in any plane. Rotation of the clamp member is where the problem would occur, and that only becomes evident when leaving the 180&#176; orientation. I believe that with the slight modification, the clamp member will re-align with the XY plane. I can not model this because Alibre' has no means to limit motion based on interference between faces. It will have to be tested.

This is the modification:







While thinking about this, has anyone got any theories as to what happens when the engine is articulated beyond 180&#176;?

Jerry


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## Ken I (May 16, 2012)

Captain Jerry  said:
			
		

> at 180° there is no force that encourages that.



Agreed - but at 179° there is - the question is will the "self righting" of the elbows defeat the "self locking" tendency.

However your suggested design renders this moot - even if it does move out of whack it has sufficient articulation to reenter the self righting zone.



			
				Captain Jerry  said:
			
		

> While thinking about this, has anyone got any theories as to what happens when the engine is articulated beyond 180°?



I would guess it will pick up where it left off - restarting again at (whatever)°

Ken


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## Captain Jerry (May 22, 2012)

Dang it! I can't stop thinking about this silly project. I'm thinking about doing it like this. 







The way I am thinking is that friction is the big problem with this engine so I am looking at ways to reduce it. One way to do that is to reduce surface contact. I am looking at the piston as having two separate functions ... piston and crosshead. The piston of course must be full diameter to seal the bore. The crosshead does not need to seal the bore but must provide constant linear contact. To reduce surface contact, the crosshead portion can be fluted as shown. The area between the piston and the crosshead is reduced to eliminate surface contact in that area and the piston has three oil control groves. It could be made to include an o-ring if necessary. The cylinder is aluminum and the piston/crosshead is cast iron.

Don't be shy. Tell me what you think. There is still plenty of time do do it differently.

I have also discovered an additional problem that can occur if the cylinders are allowed to reach the 180° position. At that position, the pistons can shift longitudinally in the bore. At that point, the hinge point is locked in the bore and cannot be expected to re-align or recover. A limit will have to be placed on the swing angle.

Thanks for watching

Jerry


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## Ken I (May 23, 2012)

Captain Jerry  said:
			
		

> I have also discovered an additional problem that can occur if the cylinders are allowed to reach the 180° position. At that position, the pistons can shift longitudinally in the bore. At that point, the hinge point is locked in the bore and cannot be expected to re-align or recover.



Didn't see that one coming - but its obvious really - much nicer to discover these things in the "gedankexperiment" phase - well spotted.

Whenever systems approach a point of singularity - generally violating the "Thou shalt not divide by zero" commandment - all sorts of nasty things happen.

Ken


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## Captain Jerry (May 23, 2012)

Ken

I didn't see it coming either. I was manipulating the Alibre' model to verify the piston length at the extremes of articulation and it just happened. It was a revelation about the design as well as a revelation about the ability of Alibre' to uncover unexpected results.

Jerry


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## Captain Jerry (Jun 11, 2012)

I have been absent for a while due to some strange phenomena. Vertical and horizontal orientation gets out of whack making it difficult to get to the shop. Which is just as well. Probably not the best place to be. The dizzines also made it difficult to read and write without getting nauseous.  

It has gotten much better so a may get back to the shop soon, but for now I may just read and write for a while. Here is some of what I was working on last:















What are the chances of making this worK

Jerry


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## Ken I (Jun 12, 2012)

Captain Jerry  said:
			
		

> Vertical and horizontal orientation gets out of whack making it difficult to get to the shop.



Put more water with it.

But seriously - sorry to hear that.

As to it working - cute proof of concept - I think friction is going to get the better of it unless you apply some serious pressure.

But that's just an opinion - what do I know.

Ken


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## Captain Jerry (Jun 12, 2012)

Ken I  said:
			
		

> Put more water with it.



Water? I have heard of people doing that but I never quite understood why?

Jerry


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## Rayanth (Jun 13, 2012)

As is always the case when I am at work and bored, I started thinking crazy thoughts.

I am throwing this one out there as another possible joint to eliminate locking from rotation.

How about a plated magnet on the end of one rod, and a steel ball bearing on the end of the other?

- Ryan


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## Ken I (Jun 13, 2012)

That's actually a rather good idea - I would add a ferrous spherical seat to the magnet - but the idea of an open magnetic socket holding a ball is intriguing.

Ken


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## Rayanth (Jun 13, 2012)

Only suggested plated for the magnet to ensure it would have a hardened surface. A soft magnet surface would not likely stand up to the wear and tear very well at all. Plus it'd be shiny, like the ball bearing on the other end.

Glad to know I'm not TOTALLY insane... 

- Ryan, quietly thinking up other silly ideas.


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## Captain Jerry (Jun 14, 2012)

Ryan

Magnets! Good idea. Got me thinking. Experiments with the ball and forked socket have not been entirely succesfull. It is difficult to maintain a close fit and any slop leads to misalignment and added friction.

Ken

I agree that a spherical socket would be helpful in maintaining alignment. So, how about two sockets with a ball trapped between them? I am thinking of trying something like this:






They are 3/8" diameter neodymium magnets with a countersunk face for a screw and are available as a pair with N/S poles outfacing. I would not attach them with a screw since the pistons are cast iron but would turn a very short spigot to fit the straight part of the screw hole to hold them in alignment with the piston. A 3/16" or 1/4" ball should fit the recess.  Being magnetically challenged, I'm not to sure how the n/s fields would interact when the cylinders are at 90° but at greater angles it should work well.

Another option would be regular cylindrical magnets with a cast iron cap for the seat. I think either would work. How about it?

Jerry


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## Ken I (Jun 15, 2012)

Captain,
      That looks like a plan - but the conical sides of the magnets would need to be opposite poles for the best effect.

Try it - if you place a piece of steel between two magnets - the magnets will stick to it if the piece of steel is thick enough to carry the magnetic flux but the attraction is very much weaker.

On a thin piece they will still repel - I suspect on a ball they will either repel or be very weak.

That said, such a joint on an elbow engine is always in compression (there is no induction stroke).

Ken


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## Captain Jerry (Jun 15, 2012)

Ken

I think that's why they are sold in pairs. One is N out and the other S out so they will attract each other when screwed to opposite faces.  I just don't know how well the will hold the ball when the poles are at 90° but then I'm not sure that I can get them to 90° with a 3/8" diameter ball. It depends on how deep the ball sits in the seat.






No sense guessing. I'll have to try it out. The 90° position is not as important for this project as the range of angles between 100° and 170°.

Jerry


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## Ken I (Jun 15, 2012)

I'm going to presume it will form a NSNS circuit - when you bend the joint the field will bend also - I'm guessing the loss of force will be very little - but why guess when you can try it out easilly enough.

There are going to be friction losses here - but again I don't think they will be too significant.

Let us know how it goes - its a very interesting concept.

I gave Rayanth a KP for thinking outside the box.

Ken


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## Rayanth (Jun 15, 2012)

bah, I'm only thinking outside the box because I'm too new to have FOUND the box yet - I honestly expected an explanation as to why magnets wouldn't work, not everyone jumping on board and running with my idea  ;D

Still trying to figure out how the elbow engine even works. I've got the basic concept down, i can see how it's working in the animation. but haven't figured out transfer passages yet.

Any plans available out there for free? This certainly has my interest.

- Ryan


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## Captain Jerry (Jun 15, 2012)

Ryan

Experience is a two edged sword. It may be that time has shown the best way to do something but as technology changes it may limit the exploration of new alternatives. This is a good case in point. Without the use of super magnets, I doubt the method would be successful.

Ken

I don't think friction is a problem at the joint. With fixed elbow, there is no movement at all in the joint and so no friction. The only time there should be any movement in the joint is when the cylinders are being articulated. BUT! if the friction in ball/seat is less than the friction between the cylinder wall and the piston, then the rotation may occur at the ball joint, rather than in the cylinder bore, but the result would be a reduction in friction loss. A little dab of silicone grease in the seat might be a good thing.

Your elbow engine design allows the piston to rotate on the elbow shaft, but it could rotate on the shaft or in the bore or a combination or at different places on the power and exhaust stroke. Now that you have had some run time on you engine, what does the wear pattern on the pistons look like?

Jerry


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## Ken I (Jun 16, 2012)

Captain Jerry  said:
			
		

> Now that you have had some run time on you engine, what does the wear pattern on the pistons look like?



There isn't any - there's no repetetive locus of motion so no pattern should emerge.

As regards my comments on friction - that'll teach me to type without aforethought or attention - thank you for pointing out what should have been blindingly obvious.



			
				Rayanth  said:
			
		

> Any plans available out there for free? This certainly has my interest.



My take on the elbow engine (current project of the month winner - on the marquee) is available in the downloads section as a *.dwg, *.dxf & *.pdf all bundled into a single *.zip file.
The build notes *.doc file is too large for the downloads section - if you are interested send me a PM & your e-mail and I'll send you a copy.

They's not free - they'll cost 'e a KP point mind'e aargh.

(poor imitation of Devonshire accent - think pirate). 

Ken


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## Captain Jerry (Jun 29, 2012)

Here is a short update on this project. I was not sure how I was going to assemble this thing and get all of the cylinders aligned and connected. While I was pondering the many problems that I face, the FORCE took over and the thing assembled itself, really!





I had to leave the shop soon after this because the storms took the power out but I thought you might like to see this video.

Jerry


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## Blogwitch (Jun 29, 2012)

Jerry,

I have been following this post from the very beginning, and because I never had anything constructive to say, I kept quiet.

But having seen the trials and tribulations as you have progressed with it, I have got to say something at least.

What you (and hopefully a few other contributors) have come up with is amazing, and because of your tenacity, I am sure that eventually you will get it working.

But do keep an eye on centrifugal forces as you start to go a little faster. It is one of those types of forces that can catch you out when you least expect it.


John


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## steamer (Jun 29, 2012)

Give it a whirl Captn'  Wear your glasses!

Dave


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## Captain Jerry (Jun 29, 2012)

Bogstandard  said:
			
		

> Jerry,
> 
> I have been following this post from the very beginning, and because I never had anything constructive to say, I kept quiet.
> 
> ...



Good advice, John. I would hate to have my balls ejected! I think I am safe at any speed that I could hope to reach, but until I know for sure, I will stand to the side.

These magnets are amazingly powerful and I have had to learn some new operating methods. The magnets CANNOT be put on the workbench! In a dramatic display of the forth dimension at work, they will move. You look away and when you look back, they are gone and all you heard was a small "click". They have attached themselves to your pliers, or your file, or both and if you pick up the pliers, the file follows, along with any small fasteners in the immediate area. If you have ever machined cast iron in your shop, you will find out how poor your cleanup was. With the magnets stuck to the end of the piston, the piston surface seems to gather cast iron dust right out of the air.  I have had to change from cast iron to polished shaft rod for the pistons. I was never able to get the dust off of the cast iron. The smooth polished steel surface can be wiped almost clean and then some sticky tape gets the rest. Getting the magnets themselves clean is a bigger problem. I was able to get them clean by looping a brass wire through the center and then hitting them with with high pressure air.

Some material changes have been needed. The steel pivot pin on the base has been changed to brass. I may need to replace the cast iron bushing in the outer end of the cylinder with bronze. There is some magnetic interaction between pistons as can be seen in this video:





The force is not great but it could be a factor. More to come.

Jerry


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## Rayanth (Jun 29, 2012)

Love the accounting of your interesting side effects of magnets in the workshop, Jerry.

Also following along with keen interest. I am now seeing a few places where the magnets might have been a bad idea, but only time will tell!

- Ryan


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## Ken I (Jun 29, 2012)

Getting more and more interesting.

Did you use axial or radial porting.

Bogs makes a good point wrt centrifugal force but at the speeds these things run at I don't think its likely to present problems but the advice is well taken - stay out of the firing line.

Those magnets are acursed by evil spirits. I am using some 50x50x15 (industrial robot gripper application) which exert near half a ton at saturation - bloody dangerous - several workshop tools have attacked me.

And like you say stuff in the air sticks to them - even in a food processing (clean) environment I'm finding iron filings accumulating.

Also keep them clear of magnetic memory devices including credit card mag-stripes.

Ken


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## Captain Jerry (Jun 29, 2012)

Here it is, running, not perfect, but it is almost the first successful run. It actually ran a few minutes ago but I didn't have the camera set up. At the time of this video, it has actually run about one minute. 

http://www.youtube.com/v/8N0Z42wox8c?version=3&amp;hl=en_US&amp;rel=0

Before I quit for the day, it had about 15 minutes of run time and the performance had improved substantially. It self starts reliably and the angle of articulation has increased some. It is terribly inefficient. There are no rings or seals on the pistons, which are 3/8" polished steel shaft running in an aluminum bore, so there is a lot of air leakage, blow by. Without rings or seals, the only way to get any sealing is with a lot of 30wt oil. I am using so much oil that it might be classed as a "hydra-pnuematic" motor. I probably will not do anything to reduce oil flow until I am convinced that the rough edges are worn of and that free oil flow has purged the wear products and any remaining contamination.

The valve is radially ported. I did not show any detail of its design or fabrication because of the huge doubt that this thing would work. Now that it has proved successful, I will show its design if there is an interest.

More testing and reports will follow.

Jerry


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## ProdEng (Jun 30, 2012)

Remarkable engine :bow: I have little imagination and rely on applying others ideas, so this sort of invention is a wonder for me.

Jan


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## Ken I (Jun 30, 2012)

Its Alive !

Well done Captain - Another motor to add to your collection of engines with a high WTF factor.

I like it.

Ken


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## steamer (Jun 30, 2012)

Nice Job Capt!
 :bow: :bow:

Definitely classifys as a WTF masterpiece.....I have never seen an engine do that! th_confused0052 th_wtf1

Dave


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## Captain Jerry (Jun 30, 2012)

A little backpedaling and I'll show how the valve was made. The main cylinder rotates on cast iron bushings turning on a 1/4" polished steel shaft. The air enters one side of the standard, connects with a passage in the shaft, travels through the shaft to the valve port in the shaft. As the main cylinder block and bushing rotates, a radial hole (one of five) passes over the port and transfers air to the appropriate cylinder to drive the piston. In the second half of rotation, the cylinder port passes over the exhaust port on the shaft and air is exhausted through the shaft and out the other side of the standard.

This is similar to the porting that Ken used in his Six Shooter elbow engine (last months award winner) except that I am using a much smaller diameter shaft and needed a different method of forming the two air passages through the shaft from the standard to the port and a slightly different method of making the port.

The first step is to drill a hole in the end of the shaft. The hole is 7/32" diameter, 1.25" deep was first center drilled and then drilled to full diameter without intermediate sizes. Super high precision is not needed for this hole. 







The shaft is then extended from the chuck and parted off at a length of 1.5". The shaft is then extended from the chuck for a length of about 2" and turned to 7/32" or to fit hole drilled in the first part.






This fit should be close but should not an interference fit. When the thin shell of the first part is fitted over the turned down section of the second part, I don't want it distorted. It will be secured and sealed with locktite but before it is fitted, the air passages must be milled. Out of the lathe and into a V-block in the mill vise.

Two 1/8" wide slots are milled on opposite sides of the shaft. The length of the slots is not critical but it should not extend to the end of the shaft or to the shoulder. The depth of each slot is .062" leaving a web thickness of .126".






After the slots are milled, and the edges cleaned up with a file, the locktite is applied to the shaft and then inserted into the shell being careful not to allow sealant into the slots. The shaft is not removed from the V-block during this process so that the position of the slots is retained.










After the locktite has cured overnight, one hole is drilled through the outer shell to intersect the groove. This hole will match up with the air passage in the standard to allow air into the slot. The port is positioned, according to the dimensions of the standard and the position of the passages in the cylinder block. At this position, the port is mill as a transverse slot to the same depth as the lengthwise slot. 






 The depth of this slot affects the timing of the valve and was worked out using experimentation with an Alibre' solid model. It may not be optimal and may not even work. Actual experimentation will be needed for that answer. If the cross slot is milled too deep, it may weaken the shaft and also may bleed between pressure and exhaust. Too shallow and there may not be enough power.

The same process is carried out on the opposite side of the shaft for exhaust.

I hope this makes sense and is of interest.

Jerry


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