Universal Joint

[Charles Lamont]

Another fun project completed.

It may not be well known that a Hooke joint does not give a uniform output: there is a cyclic varaition in speed. If the input and output shafts are parallel, or both joints 'bend' through the same angle, then the joints should be lined up so that the effect gets cancelled out. That is to say, the two forks on the cardan shaft should be at the same angular position. Where the 'bend' angles are different, there is a (ISTR somewhat complicated) formula for calculating the correct disposition of the joints to give uniform output.

 

[perko7]

i cheated a bit and used as a basis a 3/8 inch universal joint from a socket set. it has the two axes of the swivel joints offset, so had to make a new spider with the axes in line, and grind down the arms on each side to restore the available angle of operation to what i needed. Drilled and tapped the spider to take high tensile socket head screws with the heads machined smooth to rotate within reamed holes in the arms. Not intended for heavy duty or continuous use but works a treat.

 

[Brian Rupnow]

Perko7--Nice!!!--we like pictures here.---Brian

 

[perko7]

Only have one picture (attached), not the best quality but shows the overall arrangement. This universal had roll pins as pivots for the forks on the spider so they were punched out and the holes opened out to suit the approximate head diameter of the M3 capscrews, which were skimmed in the lathe to remove the knurling and make them a snug sliding fit. The screws also had to be shortened to avoid hitting each other when screwed into the new spider. A touch of threadlock when assembling should prevent it from flying apart when in use. Needs to spin at about 2000RPM so not sure what the balance will be like

 

[werowance]

i came across something today I thought was intriguing, and knowing how Brian likes to experiment with different types of mechanical motion, I thought this may interest him to. magnetic gears. using neodymium magnets to propel its counterpart without actually touching.


Edit - wonder if this actually counts as mechanical motion?

 

[Brian Rupnow]

Kind of neat, but I don't think you could transfer much torque.--Brian

 

[perko7]

I seem to recall in my previous employment that some commercial water meters used a 'magnetic drive' to transmit rotational speed from an impeller in the water stream to an electronic flow meter on the outside of the pipe section. It meant there were no holes or seals to leak. As there was no real power transmission it worked perfectly well. I don't think it matches the 'magnetic gears' principle though....

 

[ShopShoe]

Brian,

Thank you for another great "fill in" project. I enjoy all your posts, but this one is nice in that it's just a quick thing "for fun". Now, I gotta do this, along with the 90-degree mechanism, which I want to do as the three-way version some day.

Someone needs to figure out a "shop-time increaser" so I can have time to actually get something done in my life that's gone crazy for the last two years.

perko7,

I have cheated and remade a U-joint from a socket wrench set myself more than once. It's a great way to get one when you need one but don't want to start from scratch.

--

So, has anyone made a CV joint? I've thought about trying it.

--ShopShoe