Is this what you are trying to do?
The constraint icons shown in the tree should help.
Click back of shaft, CTRL then front of disk, click on the constraint illuminated on bar, same with pin/pegs click on diameter CTRL plus hole diameter then select illuminated constraint icon.

In a way I suppose it could be remotely related to Wankel engine, I admit I had not thought about it those terms.

Hi emills2. This particular model I generated a little over a year ago in FC V0.16, the greater majority of the parts were drawn in Part Design WB with the use of Part WB for Helix, cubes and cylinders, all assembled using A2. Assembly strategies vary with the model at the time, sometimes starting f...

Hi All. I would be happy to share my files , this one however is to large to include here.
The plans for this model can be found at http://www.vapeuretmodelesavapeur.com/telechargements4/
Hope this is of some help.

Hi Guys. I am more than happy to share my files, regrettably again this file is too large to include at 2,165 Kb. I will try at a later date to whittle it down to include here.
You can download the plans for this model from here if it helps:- http://www.vapeuretmodelesavapeur.com/telechargements4/

Simpson and Shipton short stroke steam engine Ca 1845.
Uses horizontal rotating piston.
More info here:- https://www.pollymodelengineering.co.uk ... Engine.asp

As well as agreeing with Herbk comments, this is how the model is presented in the plans.

Thanks for all your comments, if not closed I would have expected a broken face error, redrawing the sketch cured the problem, it is that I couldn't see the error.

Further to your post, attached file of joined tubes and screenshot of helix thread form if the helix is made longer than required it can be positioned to give actual length needed. I have left the thread form visible FYI. Again unfortunately the complete file is to large to include here. When comple...

Sorry forgot to include here it is