Author Topic: NDDE Nutating Disk Displacement Engine  (Read 26038 times)

Offline paul gough

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Re: NDDE Nutating Disk Displacement Engine
« Reply #90 on: April 20, 2016, 02:33:31 AM »
I have been pondering this problem regarding proving each individual seal. Leaving aside that which would be obvious, with largish I.C. engines, turbines etc it is usually a matter of running for an appropriate time and stripping down to inspect for undesirable wear or other signs of defects, if OK then run for a longer time and repeat until satisfied. Tedious but effective, R & D in engineering is not for the impatient. It might be possible to introduce a dye or powdered graphite, at certain points and run for a short period, this might leave witness marks where there is blow past. It might take a bit of experimentation to get the right run period before everything is smothered with graphite but at this point I can't think of anything else. Marking blue, (not marking out blue), might be useful for initial checks on the seals effectiveness before everything is boxed up. Powdered graphite is a good lubricant and should be freely available, if not then ask your local locksmith where he gets his.

For your purposes it may be possible to make transparent end plates using 'Lexan',or equivalent, it is a clear shatterproof 'plastic' that is available in sheet. It is used for machine guards and places where there is a danger from projectiles injuring people. I assume it would be available in thickish sizes. It is incredibly tough and can be bent in a pan brake to any angle as well. I think it would be machinable but I am not sure if machining marks can be polished out. Acrylic sheet, bar etc. may also be a possibility but I am not aware of its impact resilience.

One question Jerry. What was the reasoning for using relatively large balls on the disk, Bishopps and Mollards designs were around 30% disk dia., yours are much larger.? Regards and best of luck when you 'breathe' some life into your new creation. Regards, Paul Gough.

Offline KB

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Re: NDDE Nutating Disk Displacement Engine
« Reply #91 on: April 20, 2016, 08:15:00 PM »
Very impressive work Jerry.

I hope testing goes as well as your machining.

Online Admiral_dk

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Re: NDDE Nutating Disk Displacement Engine
« Reply #92 on: April 20, 2016, 10:39:40 PM »
Jerry - your machining is wonderful as usual  :praise2: - but I can't see it working ....

I watched your video and I see the same volume no matter how you turn the disk crank and therefor no work produced by changing pressure. If you add another seal - say opposite of the current one, so you divide the chamber into two => changing volume as the crank is rotated = work produced by changing pressure in the two chambers ..... but that's probably just me, still not getting it ...  :help:

Best wishes

Per
« Last Edit: April 20, 2016, 10:45:24 PM by Admiral_dk »

Offline Captain Jerry

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Re: NDDE Nutating Disk Displacement Engine
« Reply #93 on: April 21, 2016, 03:43:17 AM »
Bob, I took the machine to the Cardio Lab today for ultasound testing. There was a stack of forms to be filled out when it got around to date of birth, I had to say that it was some time next week.  Well it seems that this lab does not do prenatal testing and I was referred to a women's health clinic.  when I got there, the place was surrounded by protestors and TV News people so I will have to fall back on more standard methods.

Paul, I have built and tested and many leaky engines.  As long as everything is free and easy, they will still run as long as the timing is close to being right.  I have even run a Corliss type engine with both exhaust valves locked open.  As long as there is no load, they can be made to run.
The timing on this engine is fixed so that can not be a problem and a little bypass at any of the seals does not bother me at this stage.  The problem is that this engine is very tight.  I can turn it with a wrench but there is a real bind.  It may be that the ball seals are to tight or it may be that the disk and ring are misaligned. 

I did not get much shop time today.  The mower was in the shop all last week and the grass got way ahead of me.  Six hours on the mower today to cut seven acres and my old bones are aching.

As to the size of the ball, that is really dictated by the bore for the internal ball bearing and the size is determined by the diameter of the shaft.  If the ball were made in two halves, assembled around the bearing, the ball could be made smaller but that would be a phase two refinement.  I believe that the two designs that you reference are "dingle arm" designs that have the shaft fixed in the ball and that the ball functions as the bearing.


Kevin, I think you have it exactly right.  Testing is going every bit as well as my machining and thats the rub.

Per, there are actually four chambers in this engine.   On each side of the disk, there are two chambers.  I think you are missing the point that there is a line contact between the face of the disk and the end plate that moves around the chamber.  That line contact divides the chamber and as it passes the partition, the volume between the face of the partition expands under pressure.  The chamber between the line contact and the other face of the partition contracts and because it is open to the atmosphere through the exhaust port is at a lower pressure.

I hope this is usefull to your understanding.

Jerry

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Offline Captain Jerry

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Re: NDDE Nutating Disk Displacement Engine
« Reply #94 on: April 22, 2016, 01:58:52 AM »
I am feeling much more optimistic tonight.  This thing will run!  Not yet, but soon it will run. 

Can't see inside? Open it up.  I did. I found some things that need to be fixed. Things that would keep it from working.

The first thing I noticed was a heavy wear pattern where the partition plate contacts the ball.   I had previously shown the ball/disk turning inside with the partition and pivot moving freely.  In that video, there were no end plates and I had commented that the end plates would stabilize the partition.  A little more investigation and I found that the slots in the end plates that hold the plate were neither deep enough oe long enough.  When the end plates were tightened, they turned the partition plate into a wedge clamp. Not wanting to overdo anything, and having no easy way to measure, I took a conservative approach and mad small adjustments and re-assemblies until the binding stopped.

I was doing re-assemblies without the outer ring so that I could see the effect of the small changes.  I saw some additional and unforeseen problems.  The disk face was making perfectly flat contact with the end plate on one side but there was no face contact on the other side.  The indication here is that the diameter of the seal on that side is too small.  This would also have a clamping effect on the ball when the end plates were tightened.  Okay, back to the lathe and adjust the diameter of the seal.  A few tries and the faces were making full contact.

I was reaching for my back to give it a pat, when I noticed a problem that can not be fixed with a little adjusting.  Both end plates will have to be remade.  The ball seals are made as an integral part of the end plates.  I had designed the seals as lip seals and the lips were intended to collapse a bit before the ball contacted the part of the sal that acts as a locating bearing against ball face.  The end plate/seal is made of High Density Polyethelene or HDPE sold under the trade name as Starboard.  It is rigid enough in large thickness but also fairly flexible in small sections.  It also has a  low friction.    In order for the lip to flex, it had to be undercut with a small grove.  The problem is that I had cut the groove on the wrong side of the lip.  It works just file as a seal between the engine cavity and the atmosphere, but it provides an open path between the high and low pressure sides of the disk face/end plate contact point.  It is a very small pathway and will probably not affect the engines ability to run in test mode.  But it is wrong and will be fixed at some point after the general design has been shown to work.

I had to close shop and head to the house for dinner, but as I said, I am much more optimistic now.

I need to get this wrapped up soon.  Unlike some other contributors to this forum, I can only work on one project at a time and the list of people building "Monitor Type" engines is growing.

Jerry
NOTARY SOJAK

There are things that you can do and some things you can't do. Don't worry about it. try it anyway.

Offline paul gough

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Re: NDDE Nutating Disk Displacement Engine
« Reply #95 on: April 22, 2016, 02:24:23 AM »
Jerry, Thanks for the detailed description of the faults and problems. These are important, informative and instructive, they enhance detailed understanding and having them to refer back to may also lead to alternatives arrangements becoming apparent in ones mind. Hope you find the time to build a refined version in the not too distant future. I'm sure you will get this one to run a bit, nothing like seeing some movement as a motivator. Regards, Paul Gough.

Offline Maryak

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Re: NDDE Nutating Disk Displacement Engine
« Reply #96 on: April 22, 2016, 02:49:48 AM »
Bob, I took the machine to the Cardio Lab today for ultasound testing. There was a stack of forms to be filled out when it got around to date of birth, I had to say that it was some time next week.  Well it seems that this lab does not do prenatal testing and I was referred to a women's health clinic.  when I got there, the place was surrounded by protestors and TV News people so I will have to fall back on more standard methods.

Jerry

 :lolb:

Enjoyed every word!

Regards
Bob
Если вы у Тетушки были яйца, она была бы Дядюшкой

Offline Captain Jerry

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Re: NDDE Nutating Disk Displacement Engine
« Reply #97 on: April 25, 2016, 07:24:56 PM »
This is serious work but a good laugh makes it worth continuing.  Work does continue but slowly as my shop is idled by a visit from the electricians.  They are here to complete the wiring and lighting installation.  I have been working  under temporary arrangements of extension cords and clip on lights.  While waiting for them to finish, my attention has turned to the design and possible construction of a "monitor" engine. 


If you are interested in my version, a new thread will begin soon.
NOTARY SOJAK

There are things that you can do and some things you can't do. Don't worry about it. try it anyway.

Online Admiral_dk

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Re: NDDE Nutating Disk Displacement Engine
« Reply #98 on: April 25, 2016, 08:22:33 PM »
Quote
I think you are missing the point that there is a line contact between the face of the disk and the end plate that moves around the chamber.

Thank you very much Jerry - No, I hadn't noticed that very important fact  :facepalm:

Offline zeeprogrammer

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Re: NDDE Nutating Disk Displacement Engine
« Reply #99 on: April 25, 2016, 09:52:41 PM »
If you are interested in my version, a new thread will begin soon.

I'm in.
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