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lynchr -> RE: ID Kit ¼ Super Decathlon, need advice + rebuild start (3/9/2009 6:12 AM)
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Wheel pants attachment modification
As I mentioned in earlier post, I do not like the idea of using 5 mm bolts (supplied in kit) for wheel axles. I really feel they would bend on landing. Here is what I did. BTW – This method would work with any model using aluminum gear legs and wheel pants (plastic or fiberglass).
I used DuBro 3/16” axles and drilled the legs to 5/16” to mount them. To save wear and tear on the elastic stop nuts that come with axles, I used 5/16” SAE fine thread nuts for temporary use until final assembly. I also marked the gear legs Left and Right so as to not get them backwards. They are different.
With the axles mounted, turn each nut so that a point is lined up with a bottom corner of the leg (see left side in picture) and mark where the point is. Now draw a radial line from axle hole to corner of leg. Mark point in the middle of radial line and center punch. There isn’t a lot of room for error here. Turn nut point to other corner and repeat. The third hole on each leg is halfway between nut and bend in leg – not critical location. When all 3 holes are center punched on both legs use a #44 drill bit in a drill press to drill the holes.
Cut wheel pants from vacuum forming sheet and trim until the halves fit together with no gaps but do glue them yet. Rough cut the wheel openings but be sure and leave enough material to trim after they are glued together.
On each inside half of pants, glue ½” wide 1/32” plywood strips to fill the step vacuum formed as gear leg guide on outside of pant. Next, glue 1/8” lite ply over the ply strips and leg area. Medium CA works great. Drill the axle location (indent in pants) with small drill bit and us progressively larger bits to 1/4 “. I used a reamer to open the holes to 5/16” so that axle bolt will just fit. (You can continue with drill bits if you want but be careful not to let bit grab pants.)
Now mount the inner wheel pants to the legs with the axles. Even though the pants have the indentions for leg location, I put the wheels on and installed on fuselage with tail gear in place to make sure the pants were at the same angle when mounted. If satisfied, remove legs from fuselage, lose the wheels and use the #44 drill bit again (in hand drill) to drill the 6 holes from leg side through the pants and lite ply backing plates. Take the axles off and drill just the pants with 1/8” drill bit. Assemble pants to legs again with axles and then use 2-56 allen head screws to seat T nuts inside pants.
Next thing is to take ‘em apart again and open up the 5’16” holes in pants so the axle bolt head will clear the pants see picture). I used a 12mm prop reamer to open holes and then rolled up sandpaper to finish to size. Now the pants can be attached to the legs independent of the axles.
Moving on – I used scrap outer tubing from Sullivan push rods as spacers on the axles, followed by 3/16” wheel collar – set screw not required (or use flat washer instead of collar as a bearing) to adjust wheels in center of pants. Get as close as possible but adjustments are easy by sanding nylon spacer or cutting a longer one. Mark each axle for side ( L or R).
Take the pants off again and glue the halves together. I use one clamp behind the wheel opening to hold them while glueing. For the cowl and wheel pants, I used Acetone and a #3 paint brush to join the pieces. It works extremely well, sets almost as fast as CA, and actually welds the plastic together. It also doesn’t mar the surface of the plastic if some runs out of the seam.
Almost done – Assemble axle with spacer, wheel collar, wheel, and another wheel collar. Using a extra fine Sharpy pen, mark the axle at the outer wheel collar. Do other side. Now bolt axle to leg with inner spacer and collar in place. Insert axle through hole on pant, put tire on axle, slide down and screw pant to leg. With the assembled pant check to see if wheel is correctly centered in pant. If not, adjust the inner sleeve as required and then remark outer end of axle as described above. Unscrew pant, remove wheel, and put pant back on. There is a very faint dimple on outer wheel pant where Pilot would have you drill a hole for 5mm bolt. Picture shows where I marked the bottom of the pant in line with this dimple. Measure the distance from the line you marked on the axle to the inside face of the outer pant. Cut another spacer this length.
The kit has vacuum formed reinforcements on the wheel pants sheet. Before cutting them out drill a hole through the center that matches the OD of your spacer tubing. Use a caliper to measure the tube OD and use the same, or slightly smaller size, drill bit. The tube should be a sung fit in the plastic. Note – If you are doing a different plane, or don’t have the reinforcement pieces from the kit, use a circle about the size if a quarter cut from 1/8” lite ply.
Press your last cut spacer into the reinforcement, take the pant screws out, lift up the pant just enough to slip a wheel collar and the spacer over axle and screw pant back to leg. Reinforcement should be against outer pant, axle lined up with dimple mark, and wheel spin freely. If there is no side play in wheel, sand end of outer spacer to adjust.
Take the wheel and collars off the axle and put pant back on leg. Slide reinforcement against outer pant and weld in place with Acetone.
Repeat above for other side.
With the pants modified this way, I do not feel it is necessary to add any kind of glassing or such on the inside. You will find that they are very ridged. The outer wheel collars are the only ones that need the set screw used (with flat on axle).
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