[NSRCA-discussion] Mo'CF gear talk from AeroSlave

[glmiller3 at suddenlink.net]

I had an ES gear failure in Crowley two years ago- grass field and the landing was a 9 before the broken gear leg zeroed it.  The gear strut broke straight across  perpendicular to the long axis about half way between the fuse and wheel.  In a human bone, I would call this a "pathologic fracture" ie, implying an underlying pathologic defect.  I actually patched this gear by splinting it with a piece of carbon plate, wrapping it with carbon cloth, soaking the whole thing with epoxy and wrapping it up tight with celophane and tape.  It isn't pretty, but it is quite funtional.  Since it was one of my last long ES gears I'm still using it.  

No manufacturing process is perfect, and I think somehow there was a structural weakness that failed here.  However, not all the preceding landings were 10's, so I might have cracked it on an earlier landing and it failed later.

Interestingly enough I had a gear plate failure on that same airplane (E Pinnacle- Oxai).  the gear plate was made with carbon reinforcing the bottom of a light ply plate.  I had drilled it and put screws with large washers through from above and locknuts below.  As I flew, the gear would loosen as the washers were pulled into the light ply.  After several rounds of tightening, I noticed fatigue around the washers and upsized them, but eventually, (again in Crowley on a grass field) the screw and washers pulled through the plate...leaving nice holes in the plate which stayed attached to the fuse sides.  The carbon cloth pulled off the bottom and added no significant strength.    I repaired it with a hardply top surface and it never was a problem again. 

George
---- aeroslave at tx.rr.com wrote: 

=============
Dave

Concerning your earlier email

"I am not a fan of the typical 2 piece gear – where each half stops short of the middle, and a nasty bending load is created in the center of the gear plate (unless a spreader plate/joiner is attached between the two legs). "
--

Here's how I see the stress...

On a landing, hard or soft when the gear impact, the load will be tension on the bolt closest to the edge of the "Half gear". Bolts work really good in tension. The other load is the bending back of the bolts-a load at which bolts suck. So a rough landing using a two piece gear wants to either pull the bolt through its mounting  in the plane (cuz 11lbs ain't gonna tension fail the bolt) or its gonna bend the bolt heads ...resulting in a semi tension on the plane bolt mount, wanting to once again pull it through. What happens in reality is the bolts do not break, but the entire mounting plate is stress tension up front, compression in the rear until it find sthat weak "terminated area" and rips out at that point. My whole thinking here is that regardless of a 1 piece or two piece design, the weak link to failure lay elsewhere-so 1 or 2 piece does not matter. Speaking of failures.......

Anyone who has had a gear failure...please let me hear it. Describe the landing (wasn't a 10 now was it???? be honest)  describe the failure...bolts,  plane mount, fuse sides, gear break..whatever.

My landing are always scored about 9.24-9.56, which is why Lance is testing the prototype gear.

Gray 

AeroSlave Dude #2 (Lance is #1-I default to him) 

AeroSlave
4408 Elmhurst Dr
Plano, TX  75093
www.aeroslave.com
PayPal: aeroslave at tx.rr.com
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