Building the Fokker D.VII Landing Gear
I made a tracing of the forward fuse on a sheet of Fokker paper and laid out the gear legs on top of it. The spreader bar has been fabricated, next is the brace wires.
The plans show AN43 eyebolts securing the gear to the lower longeron and serving as attachments for the gear brace wires. Robert Baslee advised me that the eyebolts have been replaced with steel tangs so larger cables can be installed when a heavier engine will be flown. I am upgrading to 3/16" cable and AN-4 bolts so the gear can be as strong as possible.
Two double tangs were in my gear kit so I cut them in half and drilled two 1/4" holes in each. A torch was used to bring them to cherry red and each 'half-tang" was bent ~45 degrees so they would align the brace cables in the right direction.
I am waiting on the 3/16" cable so the gear is braced temporarily for the shop. But it is great to see the fuse standing on its legs. Drilling the gear to the fuse is another major waypoint since it is critical to keep everything square and straight.
Couldn't resist the urge to climb into the D7 for the first time!
We will take a break from the fuse to build the Rudder. It is needed so the aft fuse deck, vertical stab and stringers can be built to fit with the rudder.
The tail wheel components supplied with the kit are designed around riveted construction and a bungee-sprung inline skate wheel. It appears to be fairly light in weight and no doubt has served well for many AA replicas.
However, I find a full swivel tail wheel to be invaluable for ground maneuvering both under power and during manual handling at the hangar. Because I'm familiar with the Vans RV tail gear, and because I also had an extra RV yoke and control arm, I decided to adapt the RV setup to the D.VII. Yes, it will be heavier than the standard AA design, but I suspect the extra weight will work in tandem with the O-200 and assist with CG location. I did decide to retain the light wheel since it should be fine for the lighter D.VII.
After considerable time staring at the fuse and mental gear grinding, here is the design as it is installed on the Fokker. The tail spring is standard RV but the yoke has been cut down to fit the 4" skate board wheel. The weldment at the top is my answer to the problem of how to adapt the RV set to the Fokker fuselage. I wanted the entire tail wheel rig to be easily removed from the finished D.VII without having to grope around the interior of the plane.
The tail spring must be rigidly mounted to inhibit side-to-side and up-down motion. A steel bushing was welded though a 1" 4130 tube to secure the forward end of the spring. A AN4-45A bolt secures the weldment to the lower longerons.
The aft end of the spring mount weldment inserts into the tailpost all the way up to the rudder hinge. Pulling the two bolts at the tailpost and through the forward bushing allows the entire assembly to drop free of the fuse in case service is needed.
By the way, also visible is how I attached the horiz stab brace tubes to the fuse. Instead of flattening the tubes and then bending them, I bolted the unbent tubes to a bracket that is bolted to the lower gusset. I have seen bent tubes crack under vibration and wanted to avoid this possibility.
Considerable time was spent measuring angles so proper geometry of the yoke could be attained. Here is the entire assembly mocked up with the fuse in taxi position. The RV spring yields good shock action and should be totally maintenance free.
Even though the spring mount is very stiff, an additional tube was added to prevent the possibility of flex at the lower longerons.
Due to concerns about how the skateboard wheel would tolerate operations on a grooved concrete runway, I replaced it with a 4" rubber wheel. I've used these type wheels on other planes and they hold up nicely on paved runways.
The D.VII has 21", heavy-duty spoked wheels. I purchased spun aluminum wheel covers because the original plane was so equipped. I'm still pondering various mounting schemes and should be able to finalize once the brakes arrive in a few days. The spun covers are beautiful items and fit quite nicely once a 2" hole is cut to fit over the axle bushing.
The axle was mounted on the bench while the wheel, brake, and cover interface is figured out.
The inside of the wheel has a stackup of wheel, cover, brake drum, spacer, brake backing plate, and axle bumper. The trick is to get everything running true. The inner cover will be trapped in place but the outer cover will need blind mounting hardware. Also needed is a brake torque arm that will attach to a gear leg.
The brakes are 5" drums sold by Tracy O'Brien. They were originally drilled for Azusa wheels but Tracy machines them for our spoked wheels with 1.25" axle. The wheels come with five holes in the hub for which the drums are drilled.
Building Log for Sam's