OCCUPATIONAL THERAPY.

 It's raining again today so I am back playing in FreeCAD. Designing an exhaust with equal length pipes is a real challenge. I find designing anything in FreeCAD a serious mental exercise but the software is very good once one gets used to it's little foibles. I prefer it's curves and splines to Blenders as they are much more controllable once one susses the tricks. Sketching 2D reference drawings anywhere and at any angle to another face or point is not easy but once mastered the drawing plane can be placed anywhere to suit in 3D space but you have to persevere.

I am running through a series of tutorials by an American....JOKO ENGINEERINGHELP. I am finding him invaluable.

I am trying to create his latest which will be revealed tomorrow if I manage to crack it. It's not an exhaust for my dream bike but the workflow should be applicable.

As you can see above I have the three (Green) Bezier curves going where I want. These are three point curves controlled by reference sketches at the ends and the three white lines or the points at the end of them in the middle, the lines are a sketch so can be modified in length with no bother. One can add as many control points as you need and put them where one wants so I'm getting closer to a constant length pipe regardless of it's path. I just have to click a point on the bottom sketch then click the middle point then the one on the top sketch. The job is parametric so just like non-destructive editing in Photoshop one can go back and play with anything and get an instant or not so instant update depending what your computer is like. As always remember not to bevel or chamfer till all is sorted as unless you have a mainframe computer you will wait forever. This is old fashioned CAD but as I grew up with a pencil and sheet of paper it is wonderful. I can recall having to use French Curves. 

As you can see the Curves Shapes Add-On pops a few wire frame replcas of the sketch along the curves. It doesn't want to do more than three curves but one is plenty for a pipe. You can see under items (High lighted) that we have five sections.

As you can see a perfect loft and the cutout in the profile is larger than the sketch in the first screen grab. One just goes back to the sketch and adjusts it for an instant update. I love it.

 With fifty items instead of five I get a wonderful profile. Like Photoshop and Blender the software is fine. The trick is to know what is where and when to click. On the left the panel shows many options like the usual programming True/False, it also can be used for points in space and sometimes dimensions. It's not a real problem excepting when trying to use ENTER. It's better to alter a 'Z or Y' if you are altering an 'X' or press re-compute. There is a button in most Workbenches for this and there are many Workbenches. It is good fun and could be of some use were I to get my dream bike.

The wonderful Honda CBX 1050. They are available for a few grand though not looking like this one. The originals handled like a sack of spanners or marbles but sounded wonderful. A French bloke did frames, forks and brakes for them in a desperate but misguided effort to make them user friendly; I suspect this is a modified one of his as the engine is being used as part of the frame....Brave. It is drop dead gorgeous. All these are forty years old now and are much more rewarding than modern bikes with traction control and ABS. I can but dream.

Have fun.