From: alwick@juno.com Date: Mon, 8 Jan 2001 09:06:10 -0800 Subject: COZY: Mech retract design flaws My ground testing verified a theory I had on why the gears strip. Just wanted to share with those yet to build. Since my computer gives me instant feedback when things go wrong, I can say with confidence that my gear were full down before I hit the little reflector in the taxi way. After that little bump, the gear nudged off of the stop location. This instantly applies load to the gear itself, instead of to the stop feature. This is a problem because the tooth engage area on the gear is too small. Failure eventually occurs. Basically, when you hit a bump, the gear momentarily unload and the spring applies a load in the opposite direction. This moves the gear off of the stop location. It only occurs at certain size bumps. So, there are at least three design flaw in the stock gear sys. 1) the down stop rotation angle is too small (doesn't go over center far enough). There is not enough moment on the gear at down stop location. This allows the gear to rotate off the stop when you hit certain bumps, at certain speeds. There are a lot of ways to improve this. One way would be to remove material from the down stop so it can rotate further. Increasing mechanism drag, locking the handle are good to consider too. 2) Poor tooth engage area puts high load on teeth. There are many unusual conditions during your planes life when the gear will be absorbing loads. It's pretty obvious it can't handle any but minimal loads. Thus a high failure rate. 3) With the above flaws, there is no way anyone should tolerate a non-locking gear handle. It should be part of the plans. Hope this helps those yet building. What are some good ways to lock the handle? -al wick Artificial intelligence in cockpit, Cozy IV powered by Subaru 2.5 Ground testing, preparing for first flight. N 9032U ________________________________________________________________ GET INTERNET ACCESS FROM JUNO! Juno offers FREE or PREMIUM Internet access for less! Join Juno today! For your FREE software, visit: http://dl.www.juno.com/get/tagj. From: SWrightFLY@aol.com Date: Sat, 3 Feb 2001 09:31:19 EST Subject: Re: COZY: Electric noselift In a message dated 2/2/01 9:23:08 PM Central Standard Time, cdenk@ix.netcom.com writes: << What I remember, most if not all the failures of the electric nose gear have been attaching to the electric accuator, or electrical failures, etc. and not the jack screw mechanism. >> We have never had a mechanical failure of the Nose Lift system that I know of and we are still looking for the mechanical weak link. Carl is correct that a few that were made by individuals from the old CSA plans that did fail at weld joints. Ever now and then a bad solder joint fails on our older systems which is why we converted to a mostly electricals that plugs in. We have shipped over 200 and have about 100 Nose Lifts flying and have replaced several manual overrides that are designed to break at 15 ft.lbs.if the unit starts up while your hand is on it cranking (so your hand doesn't break) ....Like Nat says - any design will fail if you operate it in a manner that the designer did not intend.- and the Nose lift is no exception. Steve Wright Wright Aircraft Works (Electric Nose-Lift) Stagger EZ N700EZ (under construction) Sponsor- Canard.com From: "Nat Puffer" Subject: COZY: Electric nose lift loads Date: Sat, 3 Feb 2001 09:18:01 -0600 Builders, The Varieze, Long EZ, Cozy III, and Cozy IV were all designed before the advent of the electric nose lift. When Jack Wilhelmson made a stress analysis of the nose gear linkage in preparation for designing his own electric lift, he calculated that with 400 lbs in the front seat, the bending load on the fork and NG-15 would be 500 lbs, and the force applied to NG-3 and NG-4 and NG-6 would be 3,000 lbs. If the main gear would be just a little aft of the design location, these loads would even be greater. These are tremendous loads to put on the nose gear components and the nose gear structure. Even though the ball screw is rated at 3,000 lbs, the rest of the components were really not designed for these loads. Although there haven't been any structural failures to our knowledge due to the electric lift, it is strongly recommended that you don't attempt to raise or lower the nose with more than one person in the front seat. Please ignore any claims that the electric lift will raise the nose when the aircraft is fully loaded with people, fuel, and luggage. Regards, natp PS: I never raise the nose of my Mark IV with more than one person in the front seat, and that one person is substantially less than 200 lbs.