Trestle or sawhorse for the apprentice
This is from Louis Mazerolle's book, Traite Theorique Et Pratique De Charpente, planche 27-28.
I had developed this drawing, only to realize it was wrong. I didn't get the hip rafters, sawhorse legs,correct in Plan View. So the geometric development of the sawhorse legs on the roof surface is wrong.
Here's a couple of drawings with the correct sawhorse leg development in Plan View.
The correct geometric development for the sawhorse leg on the roof surface.
After Developing a 3D model of the Tréteaux Dit Cadet I see that my original hip rafter foot print was off slightly, but it affects the entire geometric layout of the model. Back to the drawing board.
Finally got it right. The hip rafter foot print is now correct. Next, I developed the profile rafter slope just like a regular roof. Swing some arcs to a line parallel with plan view. Draw the Tréteaux,Trestle,sawhorse leg, hip rafter on the real roof surface and transfer the lines to the timber just like the drawdown method.
Checking the bevel angles at the foot of the sawhorse/hip rafter.
Here I took the developed 3D legs of the sawhorse and rotated them into position to make sure the 2D geometric development worked.
Next up, are the side crossing timbers of the sawhorse.
For the side cross rafter I used the sawhorse bevel angle and the sawhorse footprint angle to develop the cross piece. It's not precise, but it's a lot easier than Mazerolle's method. The barbe angle should be 3.38° instead of the 3.50° angle I used, but this is less than the thickness of pencil lead.
Here I develop the 3D view of the barbe angle to check it against the footprint angle I used.
3D view of the cross rafter after geometric development.
Next up, are the front crossing timbers of the sawhorse.
The crossing timbers of the sawhorse can be laid on top of the elevation view for geometric layout.
3D view of the pieces fitted together from the geometric layout for the Tréteaux Dit Cadet.
Side elevation view with arcs transferring the lines to the roof surface view.