MKII nose forks and rollovers / collapses

aviator1978 · #1 05-21-2008, 09:30 AM

I don't want to beat a dead horse.....but,

How have the new nose forks been holding up in service? Any failures?
Please leave any pilot technique comments out.

David-aviator · #2 05-21-2008, 12:35 PM

Quote:

Originally Posted by aviator1978

I don't want to beat a dead horse.....but,

How have the new nose forks been holding up in service? Any failures?
Please leave any pilot technique comments out.

Mine has been installed about 2 months with perhaps 10 flights. No failures here.

Little_Richard · #3 05-21-2008, 11:16 PM

I have been able to 'see' a large percentage of the failed gear legs and have not seen any of the new gear legs fail.

drmclaws · #4 05-22-2008, 11:20 AM

Made the change in December and have dozens of flights without a problem. Also my nose wheel shimmy seems to have died down a great deal. Wasn't that bad before but between 15-20 mph I would get a transitional shimmy. I believed it was in the nose and since the mod. have felt much much less.

Ivan McLaws RV-6A

AlexPeterson · #5 05-22-2008, 01:28 PM

My only complaint is that there is "stiction" when it steers. Meaning, as it swivels, it makes a series of "clicks" as the torque builds up, it lets go, torque builds up, it lets go and so forth. The breakaway force is identical to what I had before, and I'm ignoring it. All greased up, same belleville washers, etc..

aviator1978 · #6 06-15-2008, 10:32 AM

Does anyone know if the latest 9A nose collapse in San Diego occured with the MKII fork (the latest generation design)?

I am reviving this thread because I do not want to hijack the other discussion.

az_gila · #7 06-15-2008, 10:44 AM

Quote:

Originally Posted by aviator1978

Does anyone know if the latest 9A nose collapse in San Diego occured with the MKII fork (the latest generation design)?

I am reviving this thread because I do not want to hijack the other discussion.

...it was the latest leg design with the "angled yoke"

RV7Guy · #8 06-15-2008, 12:25 PM

Quote:

Originally Posted by az_gila

...it was the latest leg design with the "angled yoke"

After reading the entire thread on the 9 nose gear collapse, I believe there may be more to the story. I cannot believe there would be a lip between intersecting runways or taxiways at that airport large enough to cause this problem, especially on the new fork.

What was the pilot time? Time in RV's? Training etc???

rtry9a · #9 06-15-2008, 01:34 PM

I wonder if the shimmy problem is due to putting the fork pivot in front of the wheel. If the pivot were placed above and forward, turning the wheel might involve lifting the nose up a fraction of an inch, dampen the shimmy, and move the nut out of harms way.

If the problem is axle torque, any "breaking" action would force weight forward, spring the strut back where the geometry would likely lower the nut closer to the pavement.

Im assuming that the real problem involves the nut either contacting something or digging into turf; the weight of the plane then continues forward until the strut bends under, sideways, or springs the plane onto its back.

IMHO, the fix involves one or more of the following: 1. lifting the fork pivot (and nut) higher, 2. a larger front wheel, 3. smoother bearings, 4. a redesign of the strut where it is shorter and stronger (less "springy") and pivots closer to the prop with some type of dampening (shock, rubber donuts).

Any other potential solutions to consider (Im not interested in a tail dragger, and there is obviously something more involved than pilot technique when the gear collapses at taxi/parking speeds)?

az_gila · #10 06-15-2008, 02:44 PM

Quote:

Originally Posted by rtry9a

......
If the problem is axle torque, any "breaking" action would force weight forward, spring the strut back where the geometry would likely lower the nut closer to the pavement.

Im assuming that the real problem involves the nut either contacting something or digging into turf; the weight of the plane then continues forward until the strut bends under, sideways, or springs the plane onto its back.
......

I just had a chance to closely look at the San Diego nose strut (only light tapping was needed to remove it from the mount) and one very interesting thing became obivious.

The nut and lower forward portion of the yoke were totally undamaged! Not even scratched.

There must have been enough fore and aft oscillation (hit resonance?) that the edge of the lip hit at a bad point in the travel and the nose gear contacted on the lower bend.... and then the gear folded under.

The nose tire showed no scuffing, cuts or any other marks.

The grass effect (potholes, etc.) of the nut hitting the ground may be different from the hard surface effect which may be more related to fore and aft resonance - which cannot be felt by the pilot, but can be observed by outside spectators. This effect may be related to axle/bearing drag.

There may be two different effects in play....

gil A