Rotary-Vee Engine

Rdean33422 · Sep 16, 2024

I saw this video the other day so I am off down another rabbit hole..

I started with the cylinders in the milling machine. The three piston holes and the center axis hole must all be in alignment to each other. At this point the outside of the cylinder has not been turned true and I was not too concerned if it was even straight up in the vise. After the holes were drilled the cylinder was taken over to the lathe with an arbor in the center hole and the outside was turned to final size.
This gave me the best chance to get everything aligned properly.

The video above and an article from Popular Mechanics magazine the December 1965 issue shows the pistons made in one piece and bent in the middle. I can only imagine the problems associated with that bend. All the pistons must be bent at the exact same angle and exactly at a 90 degrees. I don't want to try to do that if there is some other way. The Cardan joint should take care of that problem and you can see in the picture that is what I made. It swivels in the middle and will allow for the cylinders to be mounted at different angles to each other.

Test fit.

Progress so far
Thanks for looking.
Ray

wce4 · Sep 16, 2024

Your build of this interesting engine is something I will be following closely. Is the flywheel to be machined and installed as per the drawings or as depicted in the video? Thank you for sharing. I just downloaded the drawings and instructions for building, found it on scribd.

Rdean33422 · Sep 17, 2024

wce4 as you probably know I seldom follow any plans or drawings but there will be a flywheel maybe even two.

Before I jump right in to making the side supports I want to see what kind of tolerances are needed for a smooth rotation.
I cut this piece of steel in half and drilled some holes for the axles.

With the plates clamped down to my work bench I was able to turn the cylinders but with some difficulty.

I found out just what I had suspected. The axles must be in exactly the same plane as far as nod or rise is concerned. My angle iron supports are not 90 degrees either so first I need a better base and then a better alignment..
The angle of skew or turning one cylinder from being in line with the other cylinder to 90 degrees to it has little effect. The Cardan joint has taken care of that issue.

Thanks for looking
Ray

Peter Twissell · Sep 18, 2024

I've seen a few of this style of engine, but never built one.
It's often referred to as an elbow engine.

Rdean33422 · Sep 18, 2024

Yes Pete it is but this one will be at an angle not 90 degrees. Thanks

I mounted the brackets on a poplar board at a 60 degree angle and spent the rest of the day getting the cylinders to turn smoothly.

This doesn't seem like it should be a big deal but the brass pistons are a close fit in the cylinders and they are binding. I have another reamer that is 0.001 over 3/8" so I will try that next.

Thanks for looking
Ray

Peter Twissell · Sep 18, 2024

Perhaps the binding could be relieved by allowing one of the cylinders to float radially.
I am thinking of it's bearing in an oversized bore, constrained by retaining plates front and back. This would be preferable to adding leakage.
I would suspect that oversize bores in the cylinders could create another source of binding.

Rdean33422 · Sep 19, 2024

I reamed the cylinder holes with a 0.001 oversize reamer and that did the trick. It now turns free and smooth and I don't think the extra clearance will hurt me.

As I said before this is just a test stand and not the final product but I kind of like the steel angle iron supports so I thought I would pretty them up some on the rotary table.

I forgot to mention that I made and installed a flywheel on one cylinder too.

Thanks for looking
Ray

Rdean33422 · Sep 21, 2024

Progress on this build has slowed considerably because of other jobs that had to be done but I was able to get a couple of items made.

I made the air slots in a separate piece of aluminum that will ride on the end of the cylinders They will have 3 coil springs between the plate and the steel upright. By doing it this way the plate is free to conform to the end of the cylinder and make better seal. The two small holes in each plate are for the compressed air attachments.

The original axles were 3/8" all thread.
Well that wouldn't do so I made some proper ones.

Thanks for looking
Ray

Rdean33422 · Sep 24, 2024

First an update on the project over the last few days.
The next two pictures show how the end plates and the cylinders are assembled. The brass nipples are where the air supply is attached and for the exhaust air.

A close up view of the end plates front and back. Using a surface plate and 600 sand paper I sanded the end plate and the cylinder ends for a good fit.

This is one of the piston assemblies that shows the scratches and swirl marks on the piston caused by them binding in the aluminum cylinder.

The motor will run for a very short time but then it binds up.

I believe I made two fatal mistakes when I started this project. I made the cylinders out of an unknown grade of aluminum that was difficult to turn and drill. It seemed to be gummy but I used it anyway thinking it would be OK for this.

Using brass for the pistons was probably not the best choice either. A steel piston in a steel cylinder may have been a better choice.

I am not giving up on this project but letting it rest a while for now as I think it over some.

Thanks for looking
Ray

Steamchick · Sep 26, 2024

I am surprised at the scuffing and binding - if you oiled the job adequately. Or did the compressed air "dry-up" the oiling? An in-line oiler for air tools, and air tool lube should ensure oily air to prevent scuffing?
Or maybe I am completely off track - in which case just ignore my comments.
Cheers,
K2

Jasonb · Sep 26, 2024

Your use of a screwed joint is quite likely to have some play in it which could be the cause of things binding. Why not make the elbows solid as all the other elbow engines are but just bend them to suit the angle of your cylinders. At the very least make some proper pivot pins so you have a close fitting plain shank in the holes not the thread of a screw.

Steamchick · Sep 26, 2024

I think Jason could be right, that the flexible joint means the piston is not supported by the other end of the piston, at least in one plane. (without thinking too deeply...) Maybe this causes some localisation of side thrust on a piston that leads to lubrication failure?
Just an idea.
K2

Rdean33422 · Sep 26, 2024

Jasonb said:
At the very least make some proper pivot pins so you have a close fitting plain shank in the holes not the thread of a screw.

See post #8

Ray

Jasonb · Sep 26, 2024

I don't see anything about what you quoted me saying in post #8 or #9

I have built a lot of engines with aluminium pistons in brass cylinders so the two run together OK provided the piston is not getting pulled out of line which slop in your joints will allow.

Rdean33422 · Sep 26, 2024

I originally miss read your statement sorry.
I have tried tightening the pivot joint screws to the point of making the joints immobile.
It has made no difference. I think the distance my pistons are retracted is too close to the outer end of the cylinder allowing them to bind. I am planning to start over with these issues in mind.
Thanks for you comment
Ray

Steamchick · Sep 29, 2024

Ray, Makes sense to me.
K2

NapierDeltic · Sep 29, 2024

Hi Ray.
I think also the pistons are too much retracted in outer position -lever effect. I notice the wear is clearly localized. Maybe increasing V angle would help (though reducing cylinder volume).
Also, maybe a complete cardan (or ball joint) could be of help. As I see, the pistons are forced to perform a combined motion versus cylinder block; axial and rotation with a certain angle.

Rdean33422 · Sep 29, 2024

I came to the same conclusion Brad and am waiting on some drill rod to arrive. I'm not going to rush through it this time and try to get a closer fit.

Ray

Rdean33422 · Sep 30, 2024

The last few days I decided to make Model #2 and it is much smaller than Model #1.
All the parts are made just like the larger model just smaller which has changed the stroke now to 11/16" instead of 1".
The original pistons were turned down for the smaller bore. No flywheels this time either.

This is a video to show it does run but not as I would like.

I am going to call this project a small success and may continue exploring ways of improvement in the future.

Thanks to everyone who followed along and left comments.
Ray

minh-thanh · Sep 30, 2024

"Project a small"... But quite interesting ...
Congratulations and thanks for sharing !

Rotary-Vee Engine

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