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rws327-Landing Gear
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Tail wheel assembly
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I started the tailwheel Saturday, 15 Jan 00
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A 1 1/2 ton floor jack with a block of rounded oak in the cup of the jack to help with the radius. There are also block on the sides to protect the AL bar. The pipe is to help line things up and give the jack something level to sit on. I had to move the chain out because the jack couldn't do with the chains closer. I had to do several tries because it sprang back a bit and I didn't want to go to far. |
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The end that connects to the fuselage. |
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The shopping cart wheel, |
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When I drilled the hole for the shopping cart wheel, I had plan for the alignment splines
on the shaft of the wheel. I drilled three small holes at the correct spacing, one as a
pilot for the main hole and two to align with the splines. Then enlarged the center hole
to the correct size with it meeting the spline holes. The wheel slipped right in. |
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Complete except for welding the steering horns and rounding the ends of the spring. |
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The steering horns are now attached and drilled.
Tail wheel assembly 2 hours. Completed 29 Jan 00
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Main Gear
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I started the mains Thursday, 20 Jan 00. The original the special gear design it
planned to be simple and uses bolts and brackets to avoid welding, so anyone can build it. I prefer welding as I think it has a cleaner look and I have equipment available. My gear is a mix of several people's designs (much thanks to David Morrow), but most closely resembles the gear on the KitFox Lite by SkyStar.
Parts List:(4130 steel unless otherwise noted)
Main A-frame tube 7/8 .035-
rear A-frame tube 5/8 .035
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A-frame cross tube 3/8 .035
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Tubing for pivot points 3/8 .035
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Axle socket tube 3/4 .058
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wrap-a-round gusset .063 plate
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Gusset/brake bracket .125 plate
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Axle 5/8 X 8 grade 5 bolt with castle nut
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Upper/outer spring strut 3/4 .058
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Lower/inner spring strut 5/4 .058
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Lower end plug 1/2 rod
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Cross-over tube 7/8 .035
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Cross-over wrap-a-round bracket .063 plate
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Cross-over ends 1 x 1 1/4 x .125 channel
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Spring 1.5 OD x .75 ID x 4 "Heavy Duty" Die spring rated @950 #s at 25% compression.
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Spring stop .125 washer
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Spring retainer 3/4 flanged nut grade 5 bored inside to slide over tubing.
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For welding I followed the directions for oxyacetylene welding 4130 in:
Welder's Handbook : A Complete Guide to Mig, Tig, Arc & Oxyacetylene Welding
by Richard Finch.
Mr. Finch is an EAA Technical advisor and a fair amount of the book talks
aircraft welding.
Amazon link:
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Tubing ends where heated and smashed in a vice with a wood block at the bottom that was the correct thickness, to prevent over smashing. When smashing I made sure to get the correct angle. Then I notched for 3/8 OD tubing ends.
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Tubing and welding jig.
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Dry fit assembly using a 1/4 rod for alignment.
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Aligned for tack welding, I used 5/16 bolts so it would be a truer alignment.
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Front and rear of the "A" frame in the jig. There is also a cross piece not shown, see it below.
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Wrap-a-round gusset in place prior to tacking.
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Wrap-a-round gusset welded and the main tube cut. The 5/8 I.D. axle sockets
and gussets/brake mounting brackets are shown too.
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Upper spring strut and cross-over parts. For the spring sliders I used grade 5 3/4" flanged nuts. I drilled out the threads with 3/4" drill and then oversized the hole with a cylindrical stone in my Dremel. Washers are .125 drilled and ground to size. They will be welded to the outer/upper tube.
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First try at cutting the slots for the slider. The drill bit is to help make sure the drilled holes are vertical. The wood block has a "V" cut in it. The saw unit is locked in place and I was lowering the blade down into the tubing. This would have worked fine but I couldn't cut all the way through before I reached each of the holes. See the better way below.
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This is how I got a straight line with which to drill my holes and to cut between the holes for the slot. Just use a flat block that is about 1/2 the tube diameter in thickness. I used my Dremel with a small cut-off wheel, Its smaller diameter and finer cut is much easier to be accurate with. I used several wheels to get both slots cut.
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The upper line is the cut from the Dremel tool, the lower is a pencil line for the next cut. I cut the slot about 10/100ths to small and filed through both sides to the final size.
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This is the upper cross member (replaces the U-channel) It's made of 1/8 4130 U-Channel ends with 0.90 x 1.0 4130 strap cross-piece and 7/8 x 0.035 tubing. The center bracket is 0.068 with 0.125 disks welded in at the places were the spring strut bolts pass through. (The strap is straight, it just looks bowed in this picture.)
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A closer look at the end of the cross member. the U-channel ends are welded on with a "V" joint to get a longer weld. The tube around the bolt will be trimmed down and the corners of the U-channel rounded before installation.
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The lower end of the spring strut tube has a 2" piece of rod slid inside that is held in place with a rosette weld. The bolt holds drilled and then it is slotted to allow the 0.125 axle gusset to fit inside, this will give a larger bearing area for the bolt.
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Contouring the axle gusset does three things:
1. Defocuses the stress.-
2. Allows the spring strut to pivot more freely.
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3. Lightens.
I will cut down the brake bracket once I get the brake drums and bands. Another way to do this would be to put two 0.063 gussets, one on each side of the spring strut tube.
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Joint of the last two photos.
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Nearly done, brakes and a little clean up left.
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I have personally done no engineering study on this gear, I just copied
what others are doing that seems to work.
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This RagWing WebRing
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