The project came with two landing gear legs, which sort of fit the fuselage attach points, but I had no history of these legs and in light of recent gear leg failures on several other Monocoupes, I opted to have a new set of gear legs made. NC12350 was delivered with the Type F Racing Landing gear and we fabricated a new set per the original Monocoupe drawing.
New main gear legs, fabricated from 1.5” OD, 0.095 wall thickness 4130 tube, mandrel bent to specs on Monocoupe drawing, new solid axles, etc ready to jig in assembly with the fuselage. At this point, the reinforcement patch, on the inside gear has been welded in place, along with the tabs for the tie rods.
I made a steel jig to clamp the gear legs in position, dropped plumb lines front and back, drew a center line down the shop floor, measured diagonals front and back to within 1/32”, leveled everything up. Next step was to cut and fit the rear gear leg, along with the attach bushings. The photos below show everything in place and ready to tack weld.
The attach bushing is a piece of 3/4” OD, 0.065, 4130 tubing, which after welding gets reamed to accept a 5/8” OD, 1/2” ID bushing. The attach bushing gets covered with a 0.095” x 1-3/8” 4130 strap. As you can see in the cut out from the drawing, on the left, this strap has to wrap around the bushing. Here is how I made this piece. Started with a piece of 4130 strap, 1-1/2” wide, which is a little over-width, about 11.5” long. The bushing is not perpendicular to the gear leg, so as the strap wraps around the bushing, it wants to wander off center. So, the extra width allows me to correct for that. There are a series of photos in the photo gallery at the bottom of this page which show how this strap was fabricated.
I fabricated a new tail wheel from the Monocoupe drawing. Cut out patterns from a copy of the drawing, lay it out on steel plate for cutting. Instead of the caster commonly used on these tailwheels, I’m using the 4” solid rubber wheel used on the Aviat Pitts Special. So, I did a test fit and bend of the side plates out of aluminum, due to ease of cutting and bending for the prototype. Once I was happy with the results, everything was cut out.
The I took all the pieces over to Shawn Jarrell at Jarrell Custom Aero Fabrication in Scottsdale for final welding. Sand blast and primed the assembly looks great and I think it is going to work just fine. More detail on the tailwheel in the photo gallery below.
DJ Short has been helping me with the Cleveland wheel and brake conversion. This uses 6.50 x 10 Cleveland wheels part number 40-40A, brake assembly part number 30-56, and brake disc part number 164-30615-1. The wheels are 10 inch diameter (as per original) and the brakes are 6 inch diameter, more than sufficient to brake an aircraft of 1610 lbs gross weight (these brakes are used on Cessna 182’s). The brake disc was selected to be of minimal height, which allows the whole setup to be tucked inside of the wheel and thus inside of the wheel pant. The pictures to the left show this.
You can see the holes for the bolts that hold the wheel halves together, I only have two bolts in now. That is where the bigger 10 inch brake disc attached. See how the smaller 6 inch brake disc fits inside the wheel? That small flange area of the brake disc is where the wheel needed a small amount of machining and the three bolt holts drilled. DJ Short machined the wheels.
Notice how the 6 inch brake disc and the brake caliper just fits inside of the 10 inch wheel.
I ended up having to make a second front half of the tailwheel. There wasn’t enough pivot for my liking, and when I went to install the tailwheel spring, I couldn’t get enough edge distance for the attach bolt without the tailwheel spring hitting the rear half as it pivoted. The new front half only extended the pivot axis aft by about 3/16 of an inch. I added the steering arm per the Monocoupe print and the 1/4” shock cord for steering. Everything seems to work as it should and there is no interference or rubbing anywhere.
Bob Coolbaugh posted the following information on the Monocoupe Aircraft Group on Facebook about how to “serve” the bungee cord on the tailwheel:
“Pull the two loose ends together with about 3″ of overlap, stretching the bungee about 10%. Use needle nosed vise grips to clamp both ends of the overlap. I start in the middle and work two sets of rib cord toward each end of the overlap, using half hitch knots out about 1″ each way. Double knot at the end and wrap with black cloth electric tape or heat shrink tubing (if you are smart enough to get the tubing in place first). That’s how I serve the joint. Have to replace the bungee about every 2 years, when it gets too stretched.”