V0.18 Challenge--Clerget 9B Aero Engine--UPDATE #6

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saso
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Re: V0.18 Challenge--Clerget 9B Aero Engine--UPDATE #5

Postby saso » Sun Sep 16, 2018 3:24 pm

Great showcase, as always! :)

One function of the multi-body design that our bodies do support and I don't see you would be using are the boolean operations on the bodies. I am not saying they are better in any case and that you should be using them, but if you are exploring the capabilities of PartDesign then they are one more way to deal with more complex parts. As you can see it can be specially helpful in such cases where a lot of features are required to build a singe part, as for example in your gear case, but gets even more useful when the number of features goes even much higher. Here are two examples of this method in catia

example 1
https://www.youtube.com/watch?v=qUzLKNOM6qg
https://www.youtube.com/watch?v=Sz9AEfgEDJU

example 2
https://www.youtube.com/watch?v=UoEsQG9yQos
https://www.youtube.com/watch?v=v0aj6KeB36w
https://www.youtube.com/watch?v=9RXV8QPIixU
https://www.youtube.com/watch?v=-7crEdfMKGU
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ppemawm
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Re: V0.18 Challenge--Clerget 9B Aero Engine--UPDATE #5

Postby ppemawm » Sun Sep 16, 2018 3:54 pm

chrisb wrote:
Sun Sep 16, 2018 3:15 pm
How do you guarantee the position of the accessories? Do you have a master-master-sketch?
The short answer is no.

What I do in the accessories file is to import a .step file of the mating part(s) from the engine file in order to locate the new parts. I realize that this is not too robust because if I make changes in the engine file then I have to manually change the accessories file. So, these models are not "real" assemblies. I suppose that is why we need to be able to link files and have constraints among bodies. Some day.
saso wrote:
Sun Sep 16, 2018 3:24 pm
I don't see you would be using are the boolean operations on the bodies.
I have used that before in these instances but have not had good luck in the booleans always succeeding. But, I appreciate the reminder of that capability. The example links show that having separate bodies for the exterior and interior could make a lot of sense. I left the interior to the last and simply used the subtractive groove function for the various bores.
"It is a poor workman that blames his tools..." ;)
chrisb
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Re: V0.18 Challenge--Clerget 9B Aero Engine--UPDATE #5

Postby chrisb » Sun Sep 16, 2018 5:56 pm

ppemawm wrote:
Sun Sep 16, 2018 3:54 pm
What I do in the accessories file is to import a .step file of the mating part(s) from the engine file in order to locate the new parts.
Aah, that's a good idea to transport the geometry. Poor man's assembly.
Joel_graff
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Re: V0.18 Challenge--Clerget 9B Aero Engine--UPDATE #5

Postby Joel_graff » Mon Sep 17, 2018 2:15 pm

@ppemawn: I'm giving a presentation that will feature FreeCAD in the US at the Ohio Linux Fest in Columbus, Ohio next month. I'd like to use some shots from this thread, if you don't mind...
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ppemawm
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Re: V0.18 Challenge--Clerget 9B Aero Engine--UPDATE #5

Postby ppemawm » Mon Sep 17, 2018 8:13 pm

Joel_graff wrote:
Mon Sep 17, 2018 2:15 pm
I'm giving a presentation that will feature FreeCAD in the US at the Ohio Linux Fest in Columbus, Ohio next month. I'd like to use some shots from this thread, if you don't mind...
I do not mind. Please feel free to use any of the graphics in this post.
If there is any additional specific graphics you may want from this engine model, please let me know.
"It is a poor workman that blames his tools..." ;)
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ppemawm
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Re: V0.18 Challenge--Clerget 9B Aero Engine--UPDATE #6

Postby ppemawm » Mon Oct 08, 2018 3:35 pm

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:
Picture32.jpg
Dual Magneto Assembly
Picture32.jpg (201.11 KiB) Viewed 516 times
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.

Picture33.jpg
Engine Accessories Internal Components
Picture33.jpg (198.18 KiB) Viewed 516 times
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.

Picture36.jpg
Air Pump Worm Gear Set
Picture36.jpg (185.67 KiB) Viewed 516 times
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.

Picture34.jpg
Speedometer Reduction Gearbox Assembly
Picture34.jpg (164.39 KiB) Viewed 516 times
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.

Picture35.jpg
Reduction Gearbox Housing
Picture35.jpg (147.99 KiB) Viewed 516 times
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
Branch: master
Hash: 0d228bce02f3a4aa39f2b0f2bfbd5ca5eb2a6d4b
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..." ;)
triplus
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Re: V0.18 Challenge--Clerget 9B Aero Engine--UPDATE #6

Postby triplus » Mon Oct 08, 2018 8:02 pm

Gears for sure can be challenging. Regardless of the CAD software used. That is if you plan to create them manually or some custom gear is at play. ;)