Thread: attitude control of flat surface on swing arm.

Hi again everyone.
I've tried everywhere on the net to try and find a solution to my problem but I guess
not knowing how to ask the question may be why I couldn't find anything. I'm hoping
there are some engineers amongst you who can see a solution straight away.

My problem is I have a simple lifting mechanism consisting of two levers and a bracket
to which is attached a large flat surface. As the lower arm is raised upwards, I want the
flat surface to always be parallel to the fixed arm. Here is a diagram of what I mean:




And here are some pic's of the actual mechanism. The small bracket on the end of the
swing arm carries the flat surface and this surface will cover the entire mechanism
leaving about 3mm clearance.





I'm sure there is a simple way to do this, I just can't get my head around it.
Your help would be appreciated.

Is it possable for you to follow the same design they use on floor jacks.

a four bar parallel linkage (like used in some car jacks) will work but has a range of motion limited to about 90 degrees. You probably can go above that depending on your application but the forces on the links increases significantly while the amount of control over the level drops off.

The only solution that comes to mind if you need a wide range of motion is something utilising geared ends... I started trying to figure out how this would work but I am on my day off and my head started to hurt so I stopped.

Searching for 'linkage design' might help you find something useful. If you could get access to a mechanism or mechanical device sourcebooks these usually include all sorts of examples that get the brain going.

Thanks a lot guys.
Yes, just a link or two at equal distance as the two pivot points will do what I need
Sometimes the simplest things just slip under the radar.

Thanks again.

Have a look at the bucket linkage of a Toyota skid steer, I think SK8 model loader (Bobcat type) they keep the same relative bucket angle as the arms are raised / lowered. An internet scan should turn up some pictures or visit a machinery dealer.

Interesting project. I'm intrigued, whats it for?

Sterob

The classic solution is to have two parallel arms, each fixed at both ends with a hinge-arrangement, and the distance apart the same on the base as on the platform. The double wishbone suspension on Jaguars meant that the wheels moved up and down on swing-arms, but stayed vertical rather than following a circular path.

Originally Posted by Sterob

Interesting project. I'm intrigued, whats it for?

Sterob

Thanks, it's to raise and lower the front panel on a Jarrah and aluminium PC case and
needs to carry little load.



Here's the final solution.





Thanks for the replies.