Another project that is long overdue is a drawing register for the P-39 Airacobra. This will be an Excel spreadsheet complete with drawing number, description and a link to the actual drawing file.
Assuming you have the P-39 folder arrangement as default the links will work fine.
The spreadsheet contains multiple worksheets each designated according to the folder name. The names are tabbed along the bottom to open each worksheet. The links will open the connected file in Adobe Acrobat so make sure you have the Acrobat Reader as a minimum.
The spreadsheet is still work in progress which hopefully will be available for free download this evening. The spreadsheet needs to be deposited in the root P-39 folder.
The spreadsheet is fully editable so you can adapt it for your own project. I should note that columns G and H are temporarily hidden columns that contain the hyperlink address…so don’t be alarmed when they suddenly pop up when you are developing your own adaptations.
To HIDE or UNHIDE a column, select the column header, right-click and select the option from the menu.
Every aircraft manufacturer has libraries of standard parts in addition to the MIL specs that are used for their various aircraft designs. These vary considerably covering a wide number of standard parts like bolts, nuts, washers, hinges, screws, grommets, extrusions etc, etc.
When I was working on the P-51 Mustang Tailwheel mechanism I was forever jumping back and forth looking for the various standard parts which was a nightmare due to the large number of files in the archive. This was further complicated as the file names were the scan numbers and not the drawing names. So I figured it was time to get this stuff organised.
I have worked through the archives for the Grumman F4F Wildcat and F6F Hellcat and extracted the Standard Part drawings and renamed them with the correct drawing designations. I have also done a similar exercise for the NAA P-51 Mustang.
The actual drawing filenames have been adjusted slightly to make sorting easier (by group) and make the names more legible. Where for example we have 1E48; this is denoted as 1E-48…the 1E is the alpha-numeric group designation with the numerical sequence suffix. This just makes it easier to read when you have hundreds of files in the same folder.
The excel spreadsheet is a register with the different manufacturers’ part drawings listed on separate sheets in one workbook. This is tabbed along the bottom of the spreadsheet. It is envisaged that each set of drawings as listed will include a download link to an online resource to access the files. This download link for the collection of standard part drawings is located on the top right of the spreadsheets.
The NAA Part Drawings also include the previous specification identifier as some of the earlier blueprints still refer to this number.
This is an evolving project and will be continually updated as more information becomes available with the inclusion of other manufacturers data. Currently, over 400 part drawings are registered. For further information please drop me a line at hughtechnotes@gmail.com.
P-51D Mustang: 3D Instrument Panels: Updated 11 June 2022
P-51 B and D Instrumentation Panels are now available online as a separate package. This package includes all below noted Instrumentation Panels 3D CAD models in STP, STL and 3D DWG formats with associated dimensioned 2D drawings and PDFs. Note the hole positions are listed in a tabulated form on the drawings which can be extracted for CNC work.
Also included is a copy of the original NAA instrumentation drawings for reference.
Update 20th June 2022: All Instrument panels now also include the Parasolid X_T format. The complete package is available for download, get in touch at hughtechnotes@gmail.com.
Early Version P51D: 106-51002
Later Versions: 109-516002, 109-517002
Update 15th Feb 2022
For P-51B Mustang: 97-51002
3D Model Views:
For further information drop me a line at hughtechnotes@gmail.com.
Occasionally when trying to Emboss text in Inventor the command will fail. Most likely the problem will relate to intersecting lines for the font style..invariably it will tell you why it doesn’t work.
This can be very frustrating with few solutions other than reconstructing the font style would be apparent. However, there is a way to resolve this…well at least the particular font I am trying to use for the P-51 Mustang instrument panels. In a previous article, I had opted for an alternative to the MS33558 TTF as this font style is flawed.
I have now found something more compatible and it is called TGL0-17 ALT. This is actually very close to the MS font…however I have still encountered problems.
The solution is to first open the text editor in Inventor and select the font type, set the height, width and spacing. You may need to select Exact for the latter and type in a value to achieve the correct spacing instead of using the defaults. Once you are satisfied with the formatting close the text editor and try to emboss it. If the emboss fails move on to the next step.
Select and open the text editor again and this time highlight all the text, then copy and paste this into MS Word as Text Only. Refresh the font style by selecting an alternative and then select again the TGL0-17 ALT. Copy and paste back into the Inventor text editor, close it and voila now it will emboss.
Before you ask, I have absolutely no idea why this works only that it does in this case So next time you have a problem embossing text in Inventor try this workaround and see if that works for you.
This is a sheet metal part for the P-39 Airacobra (#12-509-052) sent to me by a fellow enthusiast for comment. Before I get immersed in discussion on this subject I would just say that this part is a cable cover that is unlikely to be under any substantial stress and thus would probably be fine as modelled.
The part comprises 2 tabs, one on the top and one on the bottom. It is the fillet radius that I will focus on. The first bend is offset from the edge of the plate. The drawing specifies a 5/32″ (4mm) radius for the fillets at the intersection of the top tab and the main body which overlaps the sheet metal bend. The originator has taken this literally and attempted to create a finished fillet of 5/32″.
I suspect that the drawing is actually referring to a 5/32″ radius as it would be for the developed flat pattern because doing so otherwise; due to the bend being offset as illustrated on the cad model; this introduces stress points.
The images show the irregular continuity which creates angular edges that essentially become focussed stress points. It is often best to try to achieve smooth continuity both for bending purposes and of course when in use. What they did was sketch a face profile; which included the specified radius (#1)and then proceeded to adopt the standard commands to build the flanges. Technically it is not wrong but as the manufacturer’s drawing does not contain a developed flat pattern it is often misinterpreted…the radius should perhaps be applied to the pattern before bending.
Similarly, at the bottom tab, we also have irregular continuity as shown at #2.
I rebuilt this model to address these issues and you can see how a small change in modelling technique can obviate some of these issues.
The images show the developed pattern with the original cad model on the top and the new version on the bottom. At #3 the outline of the tab would be difficult to cut with the small taper before the fillet, whereas the lower profile at #4 is easier to cut with no stress points. Similarly for the base tab at #5 and #6. I should note that the bottom tab radius is not specified so I opted for the default minimum which fits nicely before the bend lines.
There are several ways to do this with the easiest being accomplished by using the Unfold command on a square flange and then applying the fillet before refolding. The option I have used here is first to draw an extended flange as part of the initial face sketch, create the first part of the model as a Face then apply the 5/32″ fillet before bending along a predetermined bend line sketch.
The sketched tab outline is a lot bigger than is required which of course can be trimmed once the tab is complete. You can see the extents of the tab on the initial sketch…you only need to add a plane at that point to trim. The resulting fillet is a smooth continuity with no obvious stress points.
Understandably the designers wished to increase the amount of material at the bend to maximise strength so it is advised to try to achieve those goals. As I said before, for a cover like this it is probably not too critical if we only applied a small fillet but for framing and structural elements, it may be critical.
One quick note on the 2 vertical flanges…the drawing specified an internal radius of 5/32″ which to be honest is unworkable as the resulting bend would overlap the bottom tab…in this case, I opted for the minimum specified.
At the end of the day, it is down to the interpretation of the designer intent. For the majority of sheet-metal drawings, they often do not include developed flat patterns but may contain information that is actually applicable to the flat pattern and not necessarily the finished folded profile.
Today I had an interesting conversation with a University lecturer on utilising historical blueprints as a resource for learning 3D CAD. I have been involved in similar discussions in the past and I do think they are an ideal source for those that are beginning this journey. I once helped a college to develop a curriculum for their students learning CAD on the principle that they would be more engaged in the learning process if they were developing a real-world object that they could actually relate to.
It does make a lot of sense and I would encourage new users to seriously consider the many benefits of using blueprint resources for learning. A typical aircraft design covers complex mechanical items, hydraulics, electrical, sheet metal, moulds, integration with external resources such as Excel spreadsheets as well as familiarising the end-user with tolerance application. Never mind the added benefit of how to prepare quality, fully dimensioned 2D drawings. All disciplines in one package!
I work with a lot of different CAD systems, not just Inventor, though the main reason for using Inventor is because it is accessible as a trial product more so than many others and that this industry is not one normally associated with Inventor…so it is a nice challenge. Occasionally, particularly with other CAD systems, I tend to evaluate them using the blueprints as source material to cover the many aspects of their functionality.
The blueprint archives are not expensive when you think that you could get 10000 blueprints for a small amount of money. The downside of having so many blueprints is finding what you need to help with your learning task. The P-51 Mustang blueprints come complete with a fully detailed drawing list which helps enormously. The P-39 blueprints are roughly sorted into categories which helps in this respect. The Fw190 and Bf109 sets are also very good but as they are in German this sometimes can be counterproductive if it is not your first language.
I am currently putting together a free random collection of a dozen or so blueprints from the various Aviation archives that will give you an introduction to real-world applications and a head start on your project. Just drop me a line at hughtechnotes@gmail.com.
The updated revision C version for the rear fuselage and tailfin is now available in the P-51 Mustang CAD/Ordinate package as both a DWG and DXF format.
Incorporates additional curve data, dimensions and general revision.
As usual, all inquiries to hughtechnotes@gmail.com.
I’m back after a few months dealing with a difficult period of my life. I would like to take this opportunity to thank those that stepped up to the challenge and supported me through this time.
Many moons ago I developed a series of CAD models for the P-51 Mustang Tailwheel mechanism initially to study the mechanical operations and also to clarify an otherwise obscure area that is not clearly defined on the NAA drawings.
At the beginning of 2021 I had the good fortune to obtain an Elegoo Mars pro 3D printer which just sat in the cupboard until now. Getting my life back on track I unboxed this and setup for my first print which invariably had to be one the many CAD models from my research. The part selected is the Housing for the Tailwheel spindle. Part # 73-34004.
These parts are accurately modeled from the NAA drawings so I was unsure how well they would print at 1:4 scale particularly the thin wall elements.
The first image shows the preparation using the Lychee Slicer program with the layers set to 0.05mm. I added a generous amount of supports to maintain the print integrity using the Auto support feature with a few manually added for good measure. The Resin I used was the Elegoo Water Washable Green which has worked very well. I am rather pleased with this print as I had read many horror stories of problems that folks encountered with this type of immersive printing which made me a tad anxious before I eventually decided to take the plunge.
This printer is capable of printing with a layer height of only 0.02mm which is quite extraordinary but as it took 4 hours to print this model at 0.05mm I doubt if I will venture to printing at a finer pitch as the time would be excessive. I don’t plan to print all the Tailwheel components as my budget for resin is limited but I will print a few more to determine the limitations; if any; of resin 3d printing.
Talking about the future I should note that I am currently sourcing new material for the P-51 Mustang and hopefully to start a brand new project for the F7F Tigercat.
If you are interested in the Tailwheel models check out the bottom section of thispostfor details.
On a personal note it is good to be back working on these projects and please do not hesitate to comment or drop me a line with any queries. hughtechnotes@gmail.com.
Technote: Autodesk Inventor 2022 Part Model States
In a previous Technote I briefly introduced the work method for Derived parts that provide the capability of managing model states i.e. from Forged part to machining; as separate part files. This was included in a discussion on the P-51 Mustang Tail Wheel down position modeling.
Inventor 2022; just released; now has a feature called Part Model states which will enable you to manage manufacturing operations, dimensional variations and simplified representations all on one part file.
Check out the introductory video on The Autodesk website for more details on this feature as well as more information on the latest release of Autodesk® Inventor®. This is packed with user-requested updates and enhancements to help manage your design process, speed up your connected engineering workflows and reduce repetitive tasks.
Whilst Autodesk Inventor is not normally associated with the Aviation industry it has a very advanced 3D toolset that adapts well to this industry as I have demonstrated in the many Technotes throughout this blog. So do checkout my previous articles on using Inventor in this environment and drop me a line or comment below. More information on Inventor 2022 and specific tutorials on utilizing the host of features within Inventor will follow.
Recycling Project: Repurpose Construction Site Waste.
I haven’t posted for a while due to research for a number of environmental and recycling projects. The projects involve researching design options to see how we can repurpose/recycle Construction Waste materials like timber, insulation, paper etc.
This post is just to let everyone know that I am still here and working away in the background and also as an introduction to my new project. Aviation projects of course are still work in progress.
Anyway getting back on subject: The Recycling or Upcycling project is based on maximising usage of material that would otherwise not be considered for alternative purpoes. As the typical timber waste from sites vary considerably it is critical for the new designs to be able to utilise the smallest offcuts that would not otherwise be a consideration.
I can’t go into too much detail right now but the essential elements will comprise unique lattice structural forms as well as composite design features to maximise strength and practicality. Historically, recycling construction waste is actually fairly common however it is mostly restricted to creating furniture and small garden utilities. The principal idea of repurposing for garden buildings or offices is not so common due to the technical challenges of effective use of small sized materials…until now.
I plan to crowdfund the construction of a number of these designs shortly. If anyone is interested in supporting these projects please drop me a line.
The Work in Progress aviation projects include datasets for the L23 and L33 gliders…watch this space.
Aviation CAD TechNotes 