Author Topic: Neat gearless valve train design from the Wright Bros.  (Read 11726 times)

Offline Myrickman

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Neat gearless valve train design from the Wright Bros.
« on: July 16, 2014, 12:48:26 AM »
Saw this design on a description of an engine built by the Wright Bros in their shop in Dayton Ohio . It is so stupid simple but find it so clever I had to mock it up in wood to convince myself it would work. I wonder if centrifugal force will keep the flipper in position as it cycles from one position to the other or if it needs a tensioning washer....? I have an old air cooled inverted compressor which I plan to put this on and give it a go to see how it functions as an engine.   <a href="https://www.youtube.com/watch?v=M7H-wnHxxXU" target="_blank">http://www.youtube.com/watch?v=M7H-wnHxxXU</a>

Offline Brian Rupnow

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Re: Neat gearless valve train design from the Wright Bros.
« Reply #1 on: July 16, 2014, 01:33:48 AM »
Myrickman--That is neat!!! My thoughts have been wandering towards a gearless i.c. engine with all sealed bearings and no oil sump. I don't want to think about it too much, at least until I recover from the Nemett Jaguar--Canadian Style. I have been checking into a number of "gearless" mechanisms, but I haven't seen that one before.---Brian

Offline geoff_p

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Re: Neat gearless valve train design from the Wright Bros.
« Reply #2 on: July 16, 2014, 12:16:54 PM »
You rotter, Myrickman!

That creates an urge to either modify my engine or cast-up a new one.

Regards,
Geoff
"Statistically speaking, people who have more birthdays live longer"

Offline BronxFigs

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Re: Neat gearless valve train design from the Wright Bros.
« Reply #3 on: July 16, 2014, 07:19:07 PM »
Mrickman....my hat's off to you.

I struggled for months to try to understand the Wright Bros. 2:1 concept, but my pre-senile brain threw in the towel.  Now that I see a working 3D model of this gearless device, my jaw dropped at the simplicity, and the elegant solution.

I can't wait for some clever machinist to employ this mechanism in some engine design.  Hint...hint!!!!!


Frank
90% of everything is BS!

Offline BronxFigs

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Re: Neat gearless valve train design from the Wright Bros.
« Reply #4 on: July 16, 2014, 07:39:29 PM »
Myrickman....

Do you think two ball detents - mounted behind the flipping, pivoting cam - would solidly lock that oscillating, flipper-cam in the correct orientation as it pivots into its new position?  You wondered about centrifugal forces acting on the pivoting cam.  Maybe the detents will positively locate and hold the flipper-cam in the correct place even at higher RPMs.  Who knows?  I just thought I'd ask.

Also, I can't tell by your wooden model, but is there a roller bearing mounted on the other side of the horizontal arm that engages into the track created as the flipper cam oscillates into the different positions?


Frank
90% of everything is BS!

Offline Myrickman

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Re: Neat gearless valve train design from the Wright Bros.
« Reply #5 on: July 16, 2014, 09:57:02 PM »
Yeah, I thought you gents would get a kick out of this. The cam follower is just a piece wooden dowell . Frank, I like the detent idea...insurance at higher rpms. I am a fan of unusual mechanisms like this to operate valves. The Wrights certainly were a pair of smart cookies...

Offline GailinNM

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Re: Neat gearless valve train design from the Wright Bros.
« Reply #6 on: July 16, 2014, 10:43:47 PM »
Thanks Myrickman.  I like it.
I think that a break over center spring would work easily to keep it in position.  Think older wall light switches before they all went to silent operation or a standard toggle switch.  A small single spring is all that would be necessary. I can allready think of two ways of mounting it.  :thinking:
Gail in NM
I would like to be the kind of person my dog thinks I am.

Offline BronxFigs

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Re: Neat gearless valve train design from the Wright Bros.
« Reply #7 on: July 17, 2014, 12:18:53 AM »
In the demo video, Myrickman is turning a large, disc to show how the oscillating cam works.  In reality, do you think that this larger diameter disc was actually the engine's flywheel, or, mounted on the flywheel....and the smaller disc, the engine's crankshaft?

I can already envision using this mechanism to control the exhaust valve on a vertical, air-cooled, gas engine with atmospheric intake.  The horizontal follower bar that's shown in the video can be flipped 90 degrees so that it rides the flip-flop cam vertically.  The other end of the follower can then be slipped under the stem of the exhaust valve.  It would be, essentially, just like the Olds, Vertical Gearless, but without the ratchet-indexer.  Even the original governor could probably be adapted to control the hit and miss feature.  Just thinking in print.  Am I on the right track?

The more I watch the video, the more I like this very simple, easily machined, mechanism.  The sad truth is that I would have never figured out how this design worked just by looking at the poor drawings, and sketchy explanations of the original Wright Bros. engine.  But then, that's me.


Frank
90% of everything is BS!

Offline crueby

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Re: Neat gearless valve train design from the Wright Bros.
« Reply #8 on: July 17, 2014, 01:09:08 AM »
Very elegant solution - makes you do a head slap for 'why couldnt I think of that'. I really love this kind of mechanism! The wood model makes it so clear for how it works.
I agree with the idea of a spring to hold it in fully place in each position - would be really bad for it to wobble to half position as the follower came around to hit the end at speed.

Offline BronxFigs

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Re: Neat gearless valve train design from the Wright Bros.
« Reply #9 on: July 17, 2014, 12:14:32 PM »
Since we are on the subject of gearless, 2:1 reduction  mechanisms....

Could a Geneva Wheel arrangement be used?  For example:  A 6-slot Geneva Wheel + a three lobe cam mounted to it for the 2:1 reduction.   The driver pin that engages into the indexing slots would be on the crankshaft, and the indexing Geneva Wheel/cam combo would control the exhaust valve.  You could even use a one lobe cam with wheel having 6 slots to make a 6-cycle engine, for better scavenging and air cooling the cylinder.  Of course, intake would be atmospherically controlled.

Would this set-up work?



Frank
90% of everything is BS!

Offline Alan Haisley

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Re: Neat gearless valve train design from the Wright Bros.
« Reply #10 on: July 18, 2014, 04:34:17 PM »
Since we are on the subject of gearless, 2:1 reduction  mechanisms....

Could a Geneva Wheel arrangement be used?  For example:  A 6-slot Geneva Wheel + a three lobe cam mounted to it for the 2:1 reduction.   The driver pin that engages into the indexing slots would be on the crankshaft, and the indexing Geneva Wheel/cam combo would control the exhaust valve.  You could even use a one lobe cam with wheel having 6 slots to make a 6-cycle engine, for better scavenging and air cooling the cylinder.  Of course, intake would be atmospherically controlled.

Would this set-up work?



Frank

I think that I read that Genevas don't do high speeds well. Anyone else know about this?

Alan

Online Dave Otto

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Re: Neat gearless valve train design from the Wright Bros.
« Reply #11 on: July 19, 2014, 02:05:56 AM »
That would be my guess, I used to to work on some CVD wafer coaters that used several Geneva mechanisms for material handing. Very precise but I just can't imagine them running at engine speed.

Dave

Offline BronxFigs

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Re: Neat gearless valve train design from the Wright Bros.
« Reply #12 on: September 29, 2014, 02:07:11 PM »
Some general questions to Forum Members:

If this gearless mechanism is fabricated and used on a model engine, would it be wise to use hardened steel for the crescent-shaped, flip=flop "cam" and circular inner guide, and use a softer alloy steel for the roller/follower.  What I am asking is this:  If this mechanism is used as designed, would it be better for the roller to eventually wear out, or, the central guide/cam?  Should the wearing surfaces be case-hardened?  Is this even necessary?

Logic would tell me that it is much easier to replace a worn out, roller, than it is to re-cut a crescent shaped cam.  (I realize that on a limited-use, model-engine, wear is probably not an issue, but if built-for-longevity, what would be the correct material selection for the roller, cam, and circular guide)?

Suggestions regarding steel/alloy selection, and heat-treatment (if needed) would be welcomed.  I am thinking about adapting this 2:1 reduction mechanism to control the exhaust valve on a full-size, "half-breed" vertical, single-cylinder, air-cooled, gas engine with a cross-head.  The B/S approximately: 3.5" X 5". 

Note: see video You-Tube...."A Very Big Steam Engine" - Q.C. Technologies, for a general idea of what I would like to build....my plans are to swap a gas-cylinder onto this engine frame, instead of using a steam-cylinder).

Frank
« Last Edit: September 29, 2014, 02:19:00 PM by BronxFigs »
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Offline BillTodd

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Re: Neat gearless valve train design from the Wright Bros.
« Reply #13 on: October 26, 2014, 03:14:27 PM »
This is really quite a neat idea :)

However, should the tilting-lobe move, say as a result of a kick-back or just a inadvertent knock, then the valve  timing can become 360 degrees out .

Bill


Offline BillTodd

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Re: Neat gearless valve train design from the Wright Bros.
« Reply #14 on: October 26, 2014, 05:49:24 PM »
Had to animate it:-)



Bill

Online Dave Otto

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Re: Neat gearless valve train design from the Wright Bros.
« Reply #15 on: October 26, 2014, 11:49:47 PM »
That's pretty cool Bill

If you don't mind; I curious how you did the animation?

Dave

Offline BillTodd

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Re: Neat gearless valve train design from the Wright Bros.
« Reply #16 on: October 27, 2014, 08:45:52 AM »
I use a combination of a 3d modeller and a photo manipulator/ gif editor.

it's really just a typical stop frame process: moving parts to where they should be for each frame . the modeller does some tweening but is ofte more of a hindrance than a help.

bill

Offline BronxFigs

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Re: Neat gearless valve train design from the Wright Bros.
« Reply #17 on: October 27, 2014, 09:17:44 AM »
Bill Todd-

Perfect!  Computer animations are great.  A moving picture is worth a thousand drawings!

Thanks, Myrickman and Bill Todd....for clarifying this simple mechanism.


Frank

***************************************************************************************************************

QUESTION: 

When building this mechanism, what surfaces should be hardened to prevent wearing, if any? .....flipper-cam, follower?
« Last Edit: October 27, 2014, 09:28:41 AM by BronxFigs »
90% of everything is BS!

Offline BronxFigs

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Re: Neat gearless valve train design from the Wright Bros.
« Reply #18 on: October 27, 2014, 09:40:01 AM »
As I am sitting here becoming hypnotized by the demo-video and animated version of this mechanism...some thoughts:

Can valve timing be varied, i.e. advanced, retarded?  How would this be done?  Lobe shape of the flipper-cam? 

Is this mechanism only really practical to use for controlling  the exhaust valve on an engine that has an atmospheric intake valve?
90% of everything is BS!

Offline BillTodd

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Re: Neat gearless valve train design from the Wright Bros.
« Reply #19 on: October 27, 2014, 11:04:19 AM »
I'm working on a design that would operate both valves and have a realistic timing; for instance, a typical cam has a 120° lifting period , this would equate to 240° of the crankshaft. Similarly, the inlet and exhaut cams are typically 90° apart ,to use one crank cam requires followers at 180° ,making it tricky to get the flip mechanism to work.

I think it can be done. I'll post an animation if it works:)

Bill

Offline BillTodd

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Re: Neat gearless valve train design from the Wright Bros.
« Reply #20 on: October 27, 2014, 07:37:52 PM »
Oh well :(

Doesn't look like a dual follower will work

Here's an animation with a cam of 240 degree duration.

 

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