Swinging Elbows

[Captain Jerry]

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

 

[Ken I]

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

 

[Captain Jerry]

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

 

[Captain Jerry]

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

 

[Ken I]

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

 

[Captain Jerry]

Put more water with it.

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

Jerry

 

[Rayanth]

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

 

[Ken I]

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

 

[Rayanth]

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.

 

[Captain Jerry]

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

 

[Ken I]

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

 

[Captain Jerry]

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

 

[Ken I]

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

 

[Rayanth]

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

 

[Captain Jerry]

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

 

[Ken I]

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.

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

 

[Captain Jerry]

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

 

[Blogwitch]

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

 

[steamer]

Give it a whirl Captn' Wear your glasses!

Dave

 

[Captain Jerry]

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

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