List-Post: [email protected] Date: Apr.7,2015 Subject: original or-2 retractable landing gear modifications
Mike; I am the owner of N54PB here in Henderson Nevada. I too had problems with the original design of the retractable landing gear as per the plans supplied by Rand Robinson. The following information is furnished as to how I solved the problems; Dec. 7, 1991 the first flight of N54PB from the Eldorado dry Lake south west of Boulder City Nevada. First flight went fairly well, a little pip, and early take off while doing high speed taxi test due to an unforeseen hole someone had dug in the dry lake in my path. Landing on the dry lake was uneventful. Second flight same day, landed at Boulder City airport runway 090 due to high gusty winds, had to go around four times but finally was able to touch down on the fourth try but thats when the trouble started. When the right gear touched the runway the whole assembly i.e.. gear leg, wheel, and brake lines came off. This caused the left gear to twist off and come up through the left stub wing, in the process of running the prop and doing lots of damage to the belly of the aircraft. Cause was later found to be to small of gear attach bolts as per the plans, they were AN3 bolts (3/16 diameter) these bolts are way to small for the loads. A friend of mine, Ken Mintz, owner builder of N86KM (Vari-Eze and an A and P) sent in a notification of defect to the FAA identifying the defect, this was after we verified that the plans were in error. I installed a thicker spring bar, went from 3/4 to 1? spring bar and AN5 bolts to attach the landing gear legs to the spring bar. This modification solved the initial landing gear failure. Apr.8,1998 flew out over the Amorgossa Valley, North West of Las Vegas, and back to Boulder City Nevada. Started practicing touch and go landings, wind completely calm. I was attempting to find the perfect three point landing speed by slowing down 5 mph per round until I found it. The last approach I was slightly slow and the tail wheel touched down first resulting in a very slight bounce of the mains, I added a little power and finished the landing as a wheel landing, tail up. upon rolling out and as I applied the brakes prior to crossing runway 27, the gear suddenly retracted into the wheel wells. The engine was still running with a greatly reduced prop length, the aircraft rolled to a stop on the wheels (retracted) and the air intake of the engine cowling. Cause, the Rand Robinson gear lock design allowed the locks to pop up even with double down lock springs and when the brakes were applied the locks slipped off the little aluminum box on top of the spring bar. Solution to this problem was to redesign the gear locks to ensure no more problems like this occur again. The new gear lock consists of a steal arch attached to the main spar, using the center hinge mounting bolts, and the other end is attached to the floor. The arch has a half inch hole at the top and the bottom of the arch, this hole is for a half inch steal pin that goes through the hole to hold the gear down in the down position and hold it up when retracted. The pin is attached to the spring bar and is spring loaded to push the pin through the holes when lined up in which ever position the pilot is moving the gear to. The pin assembly mounted to the spring bar arches as the gear is moved and aligns with the steal arch and its corresponding half inch holes. These two modifications were done to my KR-2 and everything else is pretty much exactly to the original plans, however I have made my bird into a single place bird due to keeping the gross weight down below 1150 lbs, me 200 lbs, 20 + 20 gal fuel, 1835 turbo charged VW. Hope this information is helpful, if you need more info or drawings, contact me off site at my address below. Thanks Parley Byington N54PB Henderson Nevada 89015 byington1954 at embarqmail.com On Apr 6, 2015, at 15:08, Mike Stirewalt via KRnet <krnet at list.krnet.org> wrote: >> "I just finished KR-2 and received the Airworthiness certificate. I > have the original landing gear.Tell me please, which bolts collapsed, > wheel center or at the spring bar or else? > Which bulletin (you mean surely the "News Letter")shall I look in? > Which gear(retractable?)did John Schaffer use??? before my gear collapse. > > >> My gear retracted while taxi run, in Oct., the prop was broken and the > crankshaft got off center,I`m waiting for the engine done next week, so, > I am desparate to avoid another collapse!!!" > Snip
