Improbability Drive

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Ken I

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Towards the end of Captain Jerry's most entertaining thread on his Encabulator build, Mike Flannery accidentally called it an Ecabulatometer - Jerry replied that he knew of no such thing and I suggested I would invent & build one.

I built it - it didn't work due to a damn fool error in the design - so, disenchanted with it, I worked on my V4 wobbler - once that was out of the way, I went back to the Encabulometer.

Since I don't want to steal any of Jerry's thunder I decided to rename it the Improbability Drive. Alternatively its an Inside Out Radial.

Why ? it's improbable because the pistons go up and down twice for each revolution of the "crankshaft"

It uses the Archimedian principal of "give me a place where I can rest my lever...." and the "Square Peg In A Round Hole" valve system.

I want to see which member of HMEM is the first to figure out what makes it tick.

The 8 radial cylinders work outwards via levers.

It has no practical application - but then who said this hobby has to make sense.

Here's a picture of the finished engine..



And all the bits....



And detail of the valve "Square Peg" - air entrers the groove to be distributed to the inlet ports in the base of each cylinder - twice per revolution - and the exhaust similarly out the side of the shaft.



Here's a video of it running - please note during the slow part of the run you can see the tacho marking tape goes around once while the pistons go up and down twice ? - curiouser and curiouser said Alice.

You might also note that opposing pistons go up at the same time.

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

It starts off at ±50 rpm - so you can see the pistons cycling at twice the output shaft speed - I then goose it up to 950 rpm - at that point it starts to get noisy - but who's interested in speed anyway.

It works without a flywheel - but I added one to get the really slow motion (its actually a turntable off a 1948 Wurlitzer 1100 Jukebox temporarilly pressed into service).

Why did I build this ? .......... why not ! - it amuses me.

Ken
 

maverick

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The two flats on the valve shaft pressurize each cylinder twice per revolution. The bearing outboard of the fulcrum is eccentric with the
shaft and receives impulses from the levers, acting as a crank throw. Only 1 power pulse per piston per rev acts on the eccentric bearing
as the opposing piston lever is against the wrong side of the bearing.
Close enough for a start?
 

Ken I

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Nahh ! that would be faking it - and it would still only go up and down once - but I like your thinking.
 

steamer

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That is so )_(#$*)( cool I can't stand it!

Karma from me!....and I want some of whatever your smoking...

Dave
 

ttrikalin

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steamer said:
That is so )_(#$*)( cool I can't stand it!
Karma from me!....and I want some of whatever your smoking...
Dave
yeah,
can i get some of that too?

take care,
tom in MA
 

compspecial

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I have no idea how it works either but its fascinating, I'm mesmerized! :bow:
Stew.
 

cfellows

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It appears that the opposing pistons travel in opposition directions which squeezes and distorts the ring on the opposite end. This squeezing creates a rotating oval, although the outer ring doesn't actually rotate. The cam attached to the crankshaft has two opposing lobes, so the squeezing action of the connecting rods rotates the crankshaft at one half the speed.

Chuck

Edit: If that's a standard ball bearing race on the bottom end in the parts picture, scratch my explanation...
 

Ken I

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Chuck - move to the top of the class - you've almost got it.

It is most definately not a standard ball race - its something rather special.

Ken
 

steamer

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I think your close Chuck. I think the bearing and eccentric are oval shaped like a harmonic drive, which provides the crank action.

Dave
 

Ken I

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Steamer - first prize - its a ball race from a harmonic drive.

Sometimes refered to as a "wave generating ball bearing" or a "flexible ball bearing".

The raceway walls are thin enough to flex - an elliptical inner distorts the bearing. By squeezing it you can make it rotate.
 

steamer

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woohoo1 th_wav

I'll take the prize behind door number 3!
;D
 

bearcar1

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Does that prize come with an emergency patch kit? (well, you know. it can get a bit rough on the open sea) :big: :big:

BC1
Jim
 

steamer

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bearcar1 said:
Does that prize come with an emergency patch kit? (well, you know. it can get a bit rough on the open sea) :big: :big:

BC1
Jim

I was gonna respond.....but I'll let it rest now.... :big:

Dave
 

Captain Jerry

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Nice job Ken. I didn't see this thread until the mystery was revealed. But that's just as well. I wouldn't have figured it out in a hundred years. I guess its a good thing you didn't decide to build an "impossibility drive." That would have taken a little longer.

Jerry
 

Ken I

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Jerry,
Steamer was too quick - I really thought it would take longer to figure out.

For all that harmonic drives are fairly commonplace, few people know what they are or how they work.

I use them all the time in my line of work - robotics.

Cyclo gearboxes are even wierder.

These devices provide reductions between 50-300 : 1 at better than 50% efficiency - which makes them reversible !

Ken

120px-Harmonic_drive_animation.gif


Cycloidal_drive_thumb.gif
 
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