Parts – Page 2 – Aviation CAD TechNotes

NAA P-51 Mustang: Tail Wheel Housing

June 19, 2015January 7, 2021HughLeave a comment

NAA P-51D Mustang: Tail Wheel Housing

In my endeavors to develop the assembly and parts register I have made some progress determining the associations in conjunction with the listing in the NAA documents. I have started with the Tail Wheel assembly,which actually has 59 drawings for the sub assemblies and parts…it was surprising the number of drawings just for this one area!

This is a partial screen shot of the assembly register; again divided by sub-assembly level down to the individual parts.

Having collated this information I started work on building the 3D Cad models, starting with the Tail Wheel Oleo Housing.

This housing is perhaps the most difficult model in the series for the Tail Wheel and it has given me problems.

The main lower bracket struts are shown in the end view on this drawing as being tangent to the main body housing but the side view suggests that the alignment is lower than the centre and therefore not tangent. The main body is tapered from the middle of the main body so a tangent with the lower struts would be difficult to achieve…I know I tried it and the geometry was complex.

I wondered if this should be tangential as is typical of these types of castings. Sometimes its not too clear what the intent of the designer was and this drawing sure would have benefited from the inclusion of an additional section through the strut.

I couldn’t be sure what the intent was here and the plan view did not present any new information, however I did notice a small detail for one of the side brackets with a solitary single line that turned out to be a reference for the interface with the struts and confirmed that in fact this item is not tangent!

This is the work-in-progress model which shows the generated profile of the junction between the main body and the lower struts, which satisfies the main details of the drawing.

As it turns out the strut is tangent but only to the edge of the end of the main housing and not the main body itself. There is also a glimpse of a side mounting bracket which will be quite complex to model due to the nature of the curved profiles that will need to be developed individually and then lofted to define the final surfaces.

Update: Finished model for the Tail Wheel Housing item 91-34003. To complete this sub assembly I just need to add the bushings.

These models and several others are now available on CGtrader

NAA P-51B/C/D Mustang: Radiator Coolant Mount

June 15, 2015June 19, 2015HughLeave a comment

NAA P-51B/C/D Mustang: Radiator Coolant Mount

I discussed in my last post the development of a comprehensive drawing register for the P-51 and my rather ambitious intent to derive the list of parts associated with each sub assembly and main assemblies.

This could indeed be quite a task as for example on the P-51C alone we have 348 assemblies listed, some are sub assemblies and some are top level assemblies. The challenge is organizing the drawing parts list according to their assembly and retain the order of links on my filing system as per the main document register.

The NAA Numerical part lists (AN01-60JE-4 Section 2) give us some idea of how this data can be collated but the chart lists the top level assemblies and does not follow the hierarchy to the individual part. The individual parts though are listed in subsequent chapters of the parts list.

The part files themselves also contain information to assist with establishing the hierarchy of assembly; similar to the following for the Radiator Coolant Mount.

As you can see from the scans this part drawing typically lists the associated next level assembly, quantity and the aircraft variants to which they belong.

This image on the left is the next level assembly (sub assembly) which shows the inclusion of fittings and bushings and again lists another next level assembly.

Typically this is how the hierarchy works and its great that we can track the target assembly from the individual part drawings.

This is the top level assembly as noted in the above drawing. Our Coolant Radiator Mounts are highlighted in red.

In this example we don’t have all the drawings for the parts listed and though it would seem unlikely to be able to build this assembly with incomplete information it may be possible to interpolate sufficient data from what we know to develop the parts that are not available.

This is typical of these types of projects as the majority of scan drawing sets are incomplete and many parts can only be developed from physical examples or interpolated where we have the requisite data from other sources.

This approach is similar to how I plan to tackle this document register in identifying the links between the part files and the assemblies. We have the NAA register; which is a great starting point; and the part and assembly files themselves. There may be instances where the information from the drawings or the NAA register is unclear, in which case I would refer to other drawings in the series that may reference this information in the notes or comments.

At this stage I have transposed the NAA register assembly chart (noted above) into a spreadsheet format so that I can add additional key information.

The image shown here is a partial screenshot of how the fuselage data has been organised, showing the hierarchy level of the main assemblies according to their respective position in the NAA chart.

The first column is a reference number I use for hierarchical lists of this nature. There is still a lot of work to be done to collate the parts associated with these assemblies; hopefully most of which I will be able to transpose from the NAA scanned register.

In the interim I shall continue to develop some of these part drawings into accurate 3d cad models.

TechNote: MS Excel Drawing Register P-51

June 12, 2015June 17, 2022HughLeave a comment

TechNote: MS Excel Pivot Tables: Drawing Register P-51

The drawing archive collection for the Mustang P-51 includes an NAA Document register in PDF that lists all the Scan Index Numbers, Drawings Number, Aircraft Type and Change (Revision)Number.

To make sense of this large archive; containing thousands of scanned images; it is necessary to first transpose the comprehensive NAA document register into a spreadsheet in order to analyse and filter the data according to requirements.

My requirements are simply to be able to group the data per content; Fuselage, Wings, Equipment etc; and per aircraft type; P-51A, P-51B, P-51C etc.

Further breakdown of data would involve isolating the main assemblies and then parts or sub assemblies belonging to each.

From Adobe Acrobat I extracted the pages of data as spreadsheet tables to which I added a Drawing Description and grouped the data sets together by “Content”…that took a long time to do as the extracted data first had to be checked and then sorted accordingly.

The drawing descriptions came from an index already created by Norman Meyers at Chanute Air Museum, so it was relatively easy to enter this data into my spreadsheet. Its a real pity I had not had access to Normans data earlier; could have saved me a lot of work. My thanks to Norman Meyers.

After sorting the data and inserting descriptions I now have separate worksheets for the content similar to this one.

What I really want now is to identify and organize the drawings belonging to each type of aircraft. For this exercise I use the Pivot Table function in Excel. Pivot Tables are great for organizing and summarizing data according to specific criteria.

Here I have initiated the Pivot Table function and selected the entire data-set of information relating to the Fuselage; as you can see we have a large number of drawings just for this one area!

When working with large data-sets it is good practice to select a new worksheet for inserting this new table.

What we end up with is a new worksheet with the pivot table outline on the left and a selection box on the right. We now select from the latter the columns of data we want…in this case all the main ones plus the P-51D; which will populate the outline table on the left.

Pivot tables by default include a summary row under each entry; I suspect this is more useful for statistics than organizing a document register; which we don’t want.

To remove the summary from the table we just need to select each column in turn using the small arrow as highlighted and turning off this option in “Field Settings” and select “None”.

The final step is to filter the data according to the required criteria; in this case I want all the drawings that have an “X” value in the P-51D column.

This is done by selecting this value from the header drop-down options; which lists by default the unique values in each column from the master table.

We now have a list of all the fuselage drawings and their location in the archive belonging to the P-51D aircraft.

The next step would be to extrapolate all the “assembly” drawings and from there the components that make up each assembly…but that’s for another day.

Pivot Tables are great for this type of job.

846 fuselage drawings for the P-51A
890 fuselage drawings for the P-51B
833 fuselage drawings for the P-51C
923 fuselage drawings for the P-51D
950 fuselage drawings for the P-51H

Many drawings of course are a shared resource for all variants. This drawing register has recently been updated with hyperlinks to all the drawings listed. See this post for details.

For further information on any of these projects please feel free to drop me a line via my contact page or email me at hughtechnotes@gmail.com

Messerschmitt: Bf109 Part

June 11, 2015June 19, 2015Hugh1 Comment

Messerschmitt: Bf109 Part

Scans of the drawings for the Bf109 have long been part of my archive, but I was always reluctant to spend anytime on this aircraft as many others have already done a great deal of work producing CAD data from these designs.

However and occasionally I come across an item that presents a challenge and this part is one of those.

8-10910-2501: Lower Frame mount.

This is a cast aluminium part with a 3 degree draft on all faces (refer second image showing cross section) except the lower edge and the top edge on centre.

The challenging aspect of this part has to do with the top face, where it was important to achieve tangency with the draft faces at each of the mounting holes and maintain this through to the centre portion where the face locally is perpendicular.

The material thickness also increases marginally at the extent of the 2 inward holes.

The front edge of this face has a center portion of a fixed radius; so to achieve the desired results based on the above criteria for the back edge I used a tangential spline. I could have just used a radius arc instead of a spline as the difference was only 0.2mm, but I am keen to get this stuff as accurate as possible.

It worked out rather well.

North American P-51 Mustang Parts

May 31, 2015June 19, 2015HughLeave a comment

NAA P-51 B/C/D Mustang:

Ordinates interpretation, translation and development are an important part of my research work and rather essential to the development of the many part and frame components.

It would be great to be able to develop a full parts library for any of these aircraft projects in 3D CAD and recreate the original drawings. However the number of parts in any one aircraft is prohibitive to achieving this goal. I do though occasionally indulge in developing some of the part drawings; in 3D and 2D; if nothing more than a challenge to recreate something that was first designed 75 years ago!

These are some of the parts modelled for the P-51 Mustang: