# Improbability Drive



## Ken I (Nov 13, 2011)

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


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## maverick (Nov 13, 2011)

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?


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## Ken I (Nov 13, 2011)

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


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## maverick (Nov 13, 2011)

OK, I'll have another cuppa and think on it for a while.


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## steamer (Nov 13, 2011)

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

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

Dave


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## ttrikalin (Nov 13, 2011)

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


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## compspecial (Nov 13, 2011)

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


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## cfellows (Nov 13, 2011)

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...


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## Ken I (Nov 13, 2011)

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


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## steamer (Nov 13, 2011)

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

Dave


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## Ken I (Nov 13, 2011)

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.


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## steamer (Nov 13, 2011)

woohoo1 th_wav

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


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## Ken I (Nov 13, 2011)

It's a free burial at sea with an inflatable lady of your choice.

Ken.


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## maverick (Nov 13, 2011)

Way to go Steamer. I'm glad I didn't win, don't know how to swim.


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## steamer (Nov 13, 2011)

She's ALL MINE!

 ;D

Dave


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## bearcar1 (Nov 13, 2011)

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


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## steamer (Nov 13, 2011)

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


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## Foozer (Nov 13, 2011)

Ken I  said:
			
		

> Improbability Drive
> 
> Ken



Not Again 

Robert


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## Captain Jerry (Nov 13, 2011)

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


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## Ken I (Nov 14, 2011)

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


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## Jeremy_BP (Nov 14, 2011)

Oh... Well... Um...
My mind is absolutely blown. That is awesome. Would you consider making plans?


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## steamer (Nov 14, 2011)

Hey Ken,

I've used them before in automation applications...so I had an unfair advantage....

Dave


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## /// (Nov 14, 2011)

Ken I  said:
			
		

> ...
> 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.
> ...



Some of the top-end telescope mounts use harmonic drives instead of the old worm and wheel.
Not heard of cycloidal drive... interesting!


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## Captain Jerry (Nov 14, 2011)

Ken

Your device has been kicking around in the back of my mind, trying to find a slot to fit in. Sort of a radial engine (inside out) and sort of a swash plate (plate angle parallel to shaft) but totally unique. I think you have created a new class of engine. I would call it a "Squash Plate."

Jerry


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## Ken I (Nov 14, 2011)

Jerry, "Squash Plate" :big:

Jeremy_BP - it never crossed my mind that anyone else might want to try it.

I do have drawings - give me a couple of days to tidy it up to "as built" and add a few build notes to it and I'll post it under the downloads section.

Obviously you would have to redesign around whatever bearing you can get your hands on - these things are fearsomely expensive so you would need to find a discard.

This one came out of the "L" or "U" axis drive on a Yaskawa Motoman L10 W 6 robot - which is now hopelessly obsolete - if you can find a local Motoman repair shop they might give you one off an old unit being cannibalised for spares.

The actual part number is
HD (Harmonic Drive Systems) 25-80-474 3
No idea what the designation means - the bore is 28mm and the OD is 60.6 x 62.1 (Eliptical)

Ken


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## student_Machinist (Nov 14, 2011)

:bow: that is unbelievably awesome!


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## kustomkb (Nov 14, 2011)

That's really cool Ken!

It really gets the "wheels" turning, or should I say "harmonic"


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## Jeremy_BP (Nov 14, 2011)

I would absolutely love to build one, although a harmonic drive would be rather difficult to source for me. I'll have to start asking around.


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## Ken I (Nov 15, 2011)

Jeremy_BP - O.K. I've posted the plans under the download section.

I draw anything I make - I'd rather find the obvious flaw on the drawing board than in the middle of manufacturing.

The file contains 2D ACAD *.dwg & *.dxf as well as a *.doc file of build notes.

Ken


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## ChrisB (Nov 15, 2011)

A truly fascinating engine, and an even more fascinating mind to come up with it and build one.

Downloading the plans now, if for nothing else to have a good nose through to work it out. Thanks for taking the time to share this really interesting build with us all. I know that I for one will get a lot out of it.

Cheers


Chris


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## Jeremy_BP (Nov 15, 2011)

Ken - Thanks. Time to start scrounging.


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## Rocket Man (Nov 15, 2011)

That is a very interesting engine. 

For many years I have wanted to build the 12 cylinder apposed cylinder engine but I don't have the equipment to make the cam crank shaft.  Your engine has given me some ideas to play round with.


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## bearcar1 (Nov 15, 2011)

Truly an interesting and unique drive assembly Ken. Fascinating to watch with all of its parts and as has been presented, quite the mystery to figure out how exactly it works. A big thank you for sharing your drawings with us and a well deserved KP for all of your efforts.

BC1
Jim


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## mu38&Bg# (Nov 15, 2011)

I think anyone that's seen a harmonic drive mechanism would remember it. It wasn't obvious in the photos, but I had a hunch that's what was going on. The video proved it, but Steamer had identified it by the I had woken up that day. It's a great idea!


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## AussieJimG (Dec 16, 2011)

Thank you sharing your ingenious engine and for introducing me to the harmonic drive and the cycloidal drive. Now you have got me thinking: does it need a harmonic drive? 

Could it be done with the roller bearings on the end of the levers operating on a cam shaped something like the wave generator?

Jim


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## Ken I (Dec 17, 2011)

Jim, you've got a point - if you built an eliptical (4 radius) hub with roller bearings constrained by a cage (which does not have to flex as long as its inner and outer rads don't foul) then each of the levers could contain an arc segment to bear against the rollers.

All horrible and complicated to no usefull purpose other than to have fun.

Ken


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