Is rotary to rotary drive possible without sliding contact ? 2

[TMcRally]

I'm trying to design a rotary to rotary drive 1:1 similar to a spur gear but with one contact face only as the driving part must return and lock in its start position while the driven part remains in its new position but is free to return under some circumstances. These will be in a low/no maintenance environment so I would like to remove all the "slide' from the two parts. The spur gear geometry doesn't seem to translate to a single tooth with 30* of rotation, It's not bad but I'm hoping there is a way to precisely plot a profile to remove all the slide. Ideally both parts would be the same part flipped but that's not a necessity.

I was hoping someone would point me in the right direction.

Thanks
Dave

 

[desertfox]

A sketch of what you are trying to do would be helpful.

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein

 

[TugboatEng]

There are quite a few couplings that allow for misalignment without sliding components.

Shaft Couplings, Spiral, Aluminum, for 1/2" x 1/2" Diameter, 2-3/8" Long, 1-1/2" OD

https://www.mcmaster.com/6208K633

Dodge Paraflex is an elastomer example.

An automotive flexplate is another.

 

[3DDave]

I think he's considering an intermittent motion coupling, but still need some diagram to show the particulars of how intermittent it needs to be.

 

[TMcRally]

Hi

I tried to upload an AVI file of it in motion but it didn't work.

Hope the Jpeg helps.

I am trying to stop the two faces from sliding on each other as one drives the other. I have had better success with a straight radius but it still slides.

It is probably acceptable but it's bugging me now and I'd like to know how to do it right.

Thanks
Dave

 

[TugboatEng]

Large telescopes use toothless drives. You're going to need to consider the friction between the two surfaces and also prevent that friction from being exceeded.

 

[3DDave]

That's what you have. What motion do you want?

 

[TMcRally]

The LH plate rotates CW 30° from where it is shown in the image. This forces the RH rotor to turn ACW 30°. The LH rotor is then turned 100° ACW and locked in place. The RH rotor stays in position, held by a latch until other mechanisms release it. When released by the latch the RH plate rotates CW 30° to a stop via spring pressure.

To reset the LH plate is rotated 100° CW.... Repeate...

 

[IRstuff]

Seems like you are asking a surface to be "sticky" at one point in time and "slippery" at a different point in time. While that could possibly be done with a material whose physical property could be "switched" on/off using electrical or magnetic means, a normal material would require moving the surfaces apart to accomplish that.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

https://www.youtube.com/watch?v=BKorP55Aqvg

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[Jboggs]

It sounds to me like what you want is commonly known as a Geneva drive indexer or a cam indexer. Many styles are commercially available.

Check these links for mechanical theories:

https://roymech.org/Useful_Tables/Cams_Springs/Indexing.html

https://www.machinedesign.com/motors-drives/article/21812974/indexing-mechanisms

Here's a couple of several manufacturers:

https://sit.destaco.com/rotary-positioning/mechanical-indexers.html

https://cdsindexers.com/products/

 

[Factoter]

Perhaps curving cam faces like a swashplate. Or add third elements that freewheels.

 

[3DDave]

OK - it's an oscillating/ratcheting input that generates an oscillating output, output driven in one direct and spring loaded to return.

Does it require conjugate action? Conjugate action is where the angular rate as input is turned results in a constant ratio to the output angular rate. If so, then you are probably stuck for an involute pair.

If not then using a roller on one part driven by a cam on the other will eliminate sliding. Use sealed bearings for a long life. I expect there are linkages, but those would take more space and require more bearings.

 

[MintJulep]

You seem to have an awful lot of self-imposed constraints that are limiting you.

Then you've compounded that by fixating on your current design solution - which frankly seems needlessly complex.

Step back and refocus on what you need to do, not how you think it should be done.

 

[TMcRally]

Thanks everyone, your input helped me come to the conclusion that there is no perfect solution and that I can live with minimising the slide. I settled on two mirrored simple curved faces and they are pretty good, easily good enough for my purposes.

Thanks again
Dave