Idea for eccentric rotational sealed couple.

 I had this idea trying to seal this gaddamned ethanol system.
(The vaseline grease gasket works perfectly as long as the shaft doesn't move, after ten minutes of rotation, it starts leaking)
For the sake of expedience I'm currently going with a different option, but I
think this one's actually better and will come back to it when I get
the chance.

I don't know how self explanatory the animation is, but basically it
converts rotation into eccentric rotation/motion and then back again.
Since the circular housing between the two shafts isn't spinning as
such, it can be sealed with a rubber sleeve. The system is therefor
completely sealed. I've tried it and it does work, with low
resistance, but tends to wobble a little and the two shafts can get
out of phase. I think both these problems can be solved by having two
'outrigger' rollers, rather than one as in the animation.

Link to animation that hasn't been messed up by instructables resizing it:

Picture of Idea for eccentric rotational sealed couple.
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SolarFlower_org (author) 7 years ago
Aha! PKM I see what you're saying, and you're right. Most of this arrangement is redundant, a simpler form would be the one below.<br /><br />It also wouldn't have the problems of jamming or wobbling, and would be quite a bit easier to construct.<br /><br />Link to version not messed around by uploader:<br /><br /><a href="http://www.sugarandfat.info/pedal_couple1.gif">http://www.sugarandfat.info/pedal_couple1.gif</a><br />

I think for my application, with the very low torque and revs, I'd get away without bearings etc.
PKM7 years ago
How do the two shafts get out of phase?  Surely both sides of the rotating disc are locked into a circular path?
SolarFlower_org (author)  PKM7 years ago
 Ideally, yes.
However, in practice, if the rollers are too tight on the inside of the cylinder they tend to jam. Make them too loose tho and there's an amount of slip before it starts exerting force, then another amount of slip before the cylinder transfers that force to the other shaft.
In that time the two rollers can easily get 90 degrees out of orientation, meaning their ideal vectors of force are quite different, and it jams.

But I'm pretty sure having two rollers per shaft will resolve this.
Ah, the rollers are pushing the clear cylinder around.  I imagined it would would have a bearing on the end of the crank, like a bicycle pedal, so the rubber bulkhead bit in the middle is attached to the eccentric but free to rotate (or in this case not rotate).

Assuming you can find bearings or bushings that like being immersed in ethanol, this should let the coupling transfer more torque out.  As always, do you have photos of a working model?
SolarFlower_org (author)  PKM7 years ago

The light grey shaft is within the ethanol system. It transfers motion to the cylinder through the process shown below, which then reverses that process onto the dark grey shaft on the left, giving it the rotation.

Both shafts make contact with the walls of the cylinder only, it being kept in place by the flat plate with the circular hole. The larger flat disks at the center of the cylinder are plastic washers to reduce friction against the plate.
Yeah- I didn't realise that only the rollers were transferring force.  I figured that they would be attached to the flat disk in the middle of the cylinder by bearings, and there would be one bearing on each side of the disk for each crank.
Arg. I don't know what instructables have done to their commenting / uploading applet, but I hope they're fixing it.<br /><br />The second gif keeps getting screwed up, here's a link:<br /><br /><a href="http://sugarandfat.info/eccentric_ortho1.gif">http://sugarandfat.info/eccentric_ortho1.gif</a>
lemonie7 years ago
While I'm interested in this machine, and you've already shown it works to an extent - it is getting rather elaborate. I think that with enough sunlight to drive the device you migh be better with something electric? Or even a wind-up clockwork mechanism?

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