The Clerget 9-cylinder engine is unusual (to me, at least) in that the cylinders rotate and the crankshaft is stationary. So far, all of the major rotating housings have been completed as shown in the following screen grabs with a few comments about the process:
- The Part tree is organized into rotating, stationary, and reciprocating subassemblies. I wanted the rotating bodies in one part so that I could easily rotate them as a complete unit to facilitate timing of cams and valve components and to check for clearances within the engine.
- Picture1.jpg (216.56 KiB) Viewed 11471 times
- The horizontal assembly includes the aero hub for attaching a propeller, front bearing housing, cambox, split crankcase, cylinders, rear bearing housing, air intake, and the distributor/drive gear components. The gears drive the air/oil pumps and magnetos.
Once individual components were created extensive use of Draft>Arrays minimized modeling effort. Although not shown clearly in the pictures, all fasteners created from the workbench or ScrewMaker 2.2 are included in the model. Lock washers were imported from McMaster-Carr. - Picture2.jpg (192.85 KiB) Viewed 11471 times
- The crankcase features were created in the sequence shown above from left to right. Cylinder solids were first created in a PolarPattern followed by a revolve of the crankcase support ring and then pads between the cylinders. PolarPatterns duplicated all the features nine times.
PartDesign fillets were applied in one go without any problems but note that the fillet on the pad between the cylinders was included in the Revolve sketch to make this possible. Learned that by trial and error. Normally I leave fillets until the end but in this case it was necessary to do them earlier in the tree.
The Groove tool was used to split the crankcase and its Edit>Duplicate into two halves. Unfortunately, this approach is not parametric. I tried using Clone and Draft>Clone but did not like the resulting complexity in the tree when added back to the crankcase part. - Picture3.jpg (189.48 KiB) Viewed 11471 times
- Revolve was used to create the solid cylinder. Since the fins were equally spaced it was possible to use LinearPattern to duplicate most of the grooves forming the fins.
The head details were fairly straight forward pockets although several separate sketches were used to keep them simple as possible.
The most difficult features were all the detail around the spark plug bosses. Revolves and grooves to form the bosses were located by sketches on a datum plane then mirrored across the global plane. - Picture4.jpg (239.06 KiB) Viewed 11471 times
- The induction pipes were most interesting but a little tricky due to the offset from center. The tube was created using the elliptical face highlighted on the upper flange and a 90 deg revolve with a Datum line axis then a pad to extend the tube vertically.
The collar for the lower mounting flange is a separate body fused to the induction tube with the PartDesign boolean tool. A groove sketch provided the clearance feature on the lower flange. - Picture5.jpg (142.9 KiB) Viewed 11471 times
The extensive use of Draft>Arrays has created a large file (66+ Mb already) which slows FreeCAD's response significantly so it is likely I will delete all the arrays in my working file and only use them for display purposes. Next up are the major stationary parts such as the engine mounting structure and crankshaft. Stay tuned for an update.
OS: Windows 10
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.18.13826 (Git)
Build type: Release
Branch: master
Hash: 3b02ff2a9481f0883063c7e24c312978ef0ce642
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)
