Wing Box Frame and Jigging Fixtures
April 2014
We have started the manufacturing of the fuselage frame for prototype #2 and #3. We have put a considerable amount of effort into designing this frame so that it can be manufactured by the builder. In this blog segment we will take a look at the procedure used in manufacturing this frame. These are only a glimpse of the process used and we are currently in the making of the assembly manual for the fuselage which will go into this process in much greater detail. We are simultaneously manufacturing the frame and making the manual on prototype #2 and on prototype #3 we will be building that frame directly from the manual.
There are a few critical elements on the frame that will require the use of fixtures in order to ensure accuracy in the alignment of the 4130 steel tube frame members. All of these fixtures are designed with drawings that can be downloaded and manufactured from a 3/4″ MDF. In addition those that have purchased a serial number will have access to DXF drawing files that can be taken to a local cabinet shop and have all of the fixtures CNC manufactured. That being said the there is no necessity for these components to be CNC manufactured. They have been designed in such a fashion that common shop tools like a band saw, a table saw, or a jigsaw can be used to build the components accurately enough to manufacture the frame fixtures.
The fuselage frame assembly manual is being laid out with very specific step-by-step instructions on how to manufacture the fixtures.
We begin the process of manufacturing the wing box fixture. Once the individual components are placed precisely in their locations they can be either glued or screwed together making it easy to disassemble. We anticipate that there will be a significant number of people building these frames and that they will want to share or sell their fixtures.
Simple easy to duplicate drawings for each component on the fixture make it relatively simple to build. This is the most complex of all the fixtures on the airframe. Most of the other fixtures simply involve screwing a couple of boards onto a piece of plywood or MDF in order to properly position the tubes for welding.
In this picture we see the initial setup of the wing box frame within the fixture. Once the components have been cut and placed in their proper location each tube simply gets tack welded. After the tack welding has been complete the top of the frame is unscrewed and the frame can be removed for easy access to all of the weld locations.
In this picture we see the wing box completed. Buy welding each one of these components individually it becomes very easy to have access to all sides of each weld. Once the individual subassemblies have been completed on the frame most all of the welding has been accomplished at that point and then the subassemblies are joined together for the final welding phase.
In this picture we see the wing box completed. Buy welding each one of these components individually it becomes very easy to have access to all sides of each weld. Once the individual subassemblies have been completed on the frame most all of the welding has been accomplished at that point and then the subassemblies are joined together for the final welding phase.
Wing Box Frame Templates
For each and every tube on the airframe we have created a template that can be used to Mark and cut each tube individually. These drawings are designed to be able to be printed as an A size drawings printed on a home computer at 100% scale. The prototype aircraft and the production prototype #2 and #3 are being manufactured using this system in order to ensure the accuracy of our drawings and the process of an individual manufacturing their own frame. We have engineered out any of the difficult tasks making this a simple process that the average person with good welding skills can complete with ease. On the template is labeled the diameter and wall thickness and the length for each tube. The honeycomb sections are simply cut out of the template and then marked for the intersections of the other tubes in the assembly. This makes for accurate assembly reducing the amount of fixtures necessary to ensure proper location of each tube.
The templates are printed off of a standard inkjet printer. We use in OfficeJet 6700 from Hewlett-Packard that costs $99 from Costco. The templates contain markings that are used to measure and check to ensure that the printer is set to 100% scale before the cutting process has begun.The next step is to simply cut out the template using a straight edge and X-Acto knife. The edges of the template have alignment marks to ensure that the template is wrapped around the tube cylindrically and has no distortion.
Each tube requires a reference mark upon which to line up the template. We have found a very accurate way of marking a round tube, by taking a piece of aluminum angle placing it face down on to the tube which orients and aligns it parallel with the tube at which point we simply make a sharpie marking on the tube that will become the reference from which all of the other alignments of the template will be made.
In this picture here you can see the mark made by the sharpie and the alignment marks placed precisely on the reference mark made the on the length of the tube.
Once the template’s placed correctly on the tube all of the cutout marks as well as the tube intersection marks can be marked using a sharpie. We use a black sharpie most of the time but of also found that the silver metallic sharpie’s contrast really nice against the black patina of a tube as it comes from the manufacturing process.
Because the tubes are cut to a very specific length before they are marked the amount of material needed to be removed is relatively small. We have found that a small bench grinder works wonderfully for grinding the tubes to their specific shape.
Another method which we use on occasion for small adjustments to tube shape and size is to use a die grinder with a carbide bit.
This process works so wonderfully that we very seldom end up with a tube that does not fit the profile perfectly. After we have tack welded some of the tubes in place there will be areas where the previous tube has been welded that will require some additional trimming of the tube but it is a far cry from the old days of cut and fit, cut and fit, cut and fit.
The picture below we see the wing box removed from the base plate and flipped inverted to add some additional tack welds before we remove it from the fixture. Even with most tack welds the MDF really doesn’t get hot enough to do anything other than char the wood in specific areas.
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