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Archive for July 30th, 2009

I’ve never really been a car enthusiast. I mean, I like race cars and I sure enjoy the looks of a few models, like this particular one that was parked at some sort of car expo near the amusement park a few weeks ago. Isn’t it a real beauty? I actually like this one better than its younger cousins that were also on display that day.

 Anyway, I like to look at cars and I like to drive them, but I’m certainly not the kind that can remember makes and models, let alone identify all the different pieces that form part of a vehicle.  Last night, however, and out of sheer curiosity after reading a post from the SolidWorks Discussion Forums where someone was asking for examples on how to use the universal joint mate and someone else suggested looking at a drive shaft, I found myself searching the internet, trying to find pictures and information about cars and transmissions and what not. I eventually found some really nice assembly pictures for a 280Z, and my husband,  who  by then had grown curious about my sudden interest for cars, was more than glad to explain to me how each of those parts was supposed to work.   I never thought I would say this, but it was actually very interesting and even kind of fun.  Or maybe he’s just a good teacher, who knows?

This is one of the images I found for the drive shaft.

After taking a long look at it, I went back to SolidWorks to try to find some information on how to use the universal joint mate, but I couldn’t find much in the help. I guess it’s because it’s not really such a complicated mate?  So, I put together my own universal joint assembly to experiment.  The universal joint, also known as Hooke’s coupling, is used to connect two intersecting shafts, and apparently has its widest use in the automotive industry.  A simple model of the Hooke-type universal joint is shown in the following image. The small shaft could be the driver, the long one could be the follower and the third link is a cross piece that connects the two yokes. 

 As the driver rotates, it transfers this rotation to the second shaft.  In SolidWorks, the universal joint mate is useful for those cases when you need to transfer rotational motion around corners or, like in the case of the driver shaft of a car, between two connected shafts that are allowed to bend at the connection point.  

I actually came up with two versions of the same assembly, one with the third link connecting the two shafts, and one where that link is missing. The one without the link uses the universal joint mate, while the other one relies on the link to transfer rotation between the shafts. The results of using one method or the other were pretty much the same.

So, to add a universal joint mate between two components, simply  select  it from the mechanical mates group, and then, under Mate Selections,  select the two components you wish to mate together (in my case the two yokes)  and, as an option, define the joint point.  The joint point (in purple in the image) represents the connection point between the two components. In this case is the point where the axis of one shaft intersects the axis of the other.  Since I didn’t have a physical component connecting both shafts, I actually sketched a point to serve as joint point and located it where the center of the missing link would be.  Just as in the case of other mechanical mates, such as gear mate and rack and pinion mate, this mate will work even when the components don’t actually touch each other or have any other component to come in touch with both and connect them, but you’ll need to add other mates to the mix in order to control the position of the elements in the screen and with respect to each other. In my case I mated the axis of each shaft coincident with a couple of reference axes that intersect each other at the joint point.

I added a rotary motor to the driver shaft and then ran the motion study.  I’m sorry I didn’t actually make a video of this one, but it’s only ten seconds worth of animation, so I didn’t see the reason for it. This is an animated gif; if you double click on it you’ll be able to see the movement of the universal joint.