OT mechanism design

Multiple revolutions, or just a partial turn?

have a look here :

there's a nice small software that's definitely useful to design such things :

Do a google search on a "crank mechanism".

A converging (think trapezoid) 4-link mechanism will make an approximate center of rotation in space but has a limited arc. The point of rotation will resemble the letter E if it were written. Another method is to use a spherical joint similar to a computer monitor base.

partial turn, approx 25 deg total.

Mads "Dale Dunn" skrev i melding news:Xns93FB55DC352EBdaledunnatjamestoolc@65.24.7.50...

The problem is that the point of rotation must not translate, spherical joint is difficult because of lack of space.

thanks for the suggestions, greatly appreciate it

Mads

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What sort of accuracy are you looking for?

Is the point of rotation in 1 or 2 planes?

I've done something like this before. Build a circular guideway or track outside the part. Adjust it so the centerpoint of the track's radius is at the desired point of rotation. Attach the part with an arm to a carriage that follows the track. The motion will be circular about the centerpoint of the track's radius, but with no attachment to the centerpoint.

Art Woodbury

I have another solution but it will be difficult to describe. If you are interested, let me know and I'll email the model to you.

Do you want to turn about a true center, or approximately?

To turn around the true center, you might use a guide rail in the shape of circular arc. There are linear bearing systems that will work on a curved rail.

To turn about an approximate center using linkages, there are several possibilities I can imagine, and probably a lot more in the handbooks others have mentioned. Without knowing exactly what you're doing, I can only suggest guesses.

I have used a double tracked cam follower systems in the past. Two cam followers mounted on a bar and being guided by the paths cut into a side frame. You can move points in space with almost no restrictions. There are some tricks to getting it to work really well though.

Jay

I have received and tested your model, it was exactly what i was looking for, thanks.

Mads

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