Nearly all of the internal components for the dual magnetos, oil pump, and air pump are now complete with the exception of two worm gear sets. Since the Gear workbench can not handle these types of gears I will need to do some research on how to accurately create them.
Several screenshots of the latest progress follows with a few brief comments:
I had no idea how complex 1920's aircraft magnetos were as the above exploded view shows. Many of the parts of which you would expect in an auto distributor is integrated into the magneto such as the condenser and contact breaker assembly.
All of the bodies for Magneto #2 are Draft>Clones since the magnetos are identical. Saves a lot of modelling time. They were moved as a group to their proper location using Placement properties.
The internal components for the speedometer reduction gearbox and the air and oil pumps were fairly straight forward to model with the exception of the right-angle worm gear sets. Note that I have simulated inaccurately the triple worm for the air pump using the Gear workbench but was not able to use this at all on the single worm for the oil pump.
The worm gear is similar to a helical gear with the exception of the root and tip radius to clear the worm. The worm is apparently similar to a Acme thread from what little I have read about it lately.
The reduction gearbox which is connected to the input shaft of the oil pump the oil pump has a couple of interesting components to model.
One is the spring loaded coupling that is shown above. The two coupling halves are joined to the spring with mating grooves in each half. I first created the spring in its proper location. Next, I created the output coupling half in a position so that the spring completely overlapped the coupling. Then I could use a PartDesign(PD)>Clone to do a PD>Boolean>Cut to create the grooves in the coupling body. Next, the coupling had to be moved to its proper axial location and rotated about its axis to line up with the spring using Placement properties.
The input coupling was more straight forward. The coupling body was created in its proper location and another PD>Clone of the spring was simply subtracted to form the grooves similar to the other coupling half.
Believe it or not, the second component that was a bit of a challenge was the deceptively simple housing for the reduction gearbox. In my first approach, joining the oval feature first to the cylindrical body and applying the large fillet at the end of the tree resulted in an invalid solid. As a result, I rearranged the model tree to create the oval first, then the fillet, the flange ears, and finally the cylindrical revolve. That passed geometry check with BOP enabled.
I was then able to go on to complete the rest of the features with out any problems until the screw hole perpendicular to the cylindrical revolve at which point it also failed geometry check. The failure is not fatal, however, since it still accepted the last fillet applied to an inside corner. I am not always so certain how important the geometry check is if none of the features fail.
I still have a few parts to model and many gears to align properly before I can call it complete. There are also some recent drawing revisions that need to be incorporated in my models if they are to be totally authentic. That will be a true test of the model's robustness. So far I have not needed faces or edges for sketches so hopefully the changes will not totally blow up the models.
The latest Version0.18 generally continues to meet my expectations for this project with some very nice additions to the Sketcher and the Placement properties. Sketch constraints are much easier to achieve and the added options for Placement are absolute jewels. However, there is still some awkwardness to complain about in the sketch attachment work process that does not suit me and the time to open and save the two large files is more than annoying. But then again, who else in their right mind would need this many bodies in one file?!
OS: Windows 10
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.18.14838 (Git)
Build type: Release
Python version: 2.7.14
Qt version: 4.8.7
Coin version: 4.0.0a
OCC version: 7.2.0
Locale: English/UnitedStates (en_US)
"It is a poor workman that blames his tools..."