Author Topic: Bent Bolts  (Read 946 times)

eschrom

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Bent Bolts
« on: Sep 01, 2017 »
These are the 5/16" bolts that hold the gear to the fuselage - all four are bent to some degree. This after 140 hours and, truth be told, one or two hard landings. If I had it to do over I'd use the strap method instead of through bolts. Either that or make only smooth landings. :D

Ed
2LS

wbpace

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Re: Bent Bolts
« Reply #1 on: Sep 01, 2017 »
Thanks for sharing that, Ed.  I originally welded in bushings for the thru-gear mount, per plans.  Then a few months ago I saw a post that indicated there was the strap option available for the IILS.  I had missed that when reading through Fred's newsletter archive.  I went back and welded in new bushings.  You make me glad I did this.

O'Bill

schines

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Re: Bent Bolts
« Reply #2 on: Sep 02, 2017 »
So Ed, are you going to just replace the bolts and fly on, or will you convert to the strap version?
Scott

eschrom

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Re: Bent Bolts
« Reply #3 on: Sep 04, 2017 »
Replace the bolts and fly. To convert means welding, which means fabric repair, which for me means probably another six months in the garage. I've already lost the summer and really want to fly it this fall.

Ed

Speed N976DH

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Re: Bent Bolts
« Reply #4 on: Sep 04, 2017 »
Your bent bolt thread is very timely to me as I found a landing gear problem with my 2L.i have an OLD set of Monnett abs cockpit side panels that I pulled out to put upholstery on them. When I pulled the two front panels the landing gear attach bolts are fully exposed, so I gave them an inspection. I saw the green epoxy primer covering the mount bushings appearing to peel. As I felt the "peel" areas with my thumbnail,I realized I was looking at a crack where the bushing was welded to the longerons. The two left ones each had one crack and the right fwd one had one also. The bushings are attached as per the 2LS with 4 through bolts.the only way I was able to repair this was to weld the cracks and then 040 steel plate to the longerons ,fore and aft cross members, and notching the plate to fit around the bushings as well. I've been finishing details before I schedule for an FAA inspection, and have been taxiing the plane a lot. I operate out of Hinckley airport, Illinois , which is sod . Had I been taxiing on a hard surface this may not have happened. I shielded both attach areas with galvanized sheet and used a wire welder.  It seems rigid now but time will tell. One of my hangar partners has a 2LS on the gear but not covered, and I told him to weld in that reinforcement plate before covering. It might be prudent for anyone with this attach configuration to give your gear a close inspection. After 30 years as an airline mechanic, my inspection eye paid off big time!

eschrom

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Re: Bent Bolts
« Reply #5 on: Sep 05, 2017 »
You've given me something to think about, Speed. When I get back to it I'm going to double check all the welds for cracks. Just to be sure.

Thx,
Ed

wafer

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Re: Bent Bolts
« Reply #6 on: Sep 07, 2017 »
I have an LTS, which uses the same gear mount configuration per plans as the LS.  After 125 hours of flight and some ~200 landings, the longerons have failed at all 4 mounting locations.  I have theories on the failure, and am identifying a repair process.
 
I do not want to hijack this thread with my situation, but do urge a good look at the welds and longerons in this area.  Mine started with loose forward bolts, and the situation progressed from there. 
Mike "Wafer" Then
SII LTS

Speed N976DH

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Re: Bent Bolts
« Reply #7 on: Sep 07, 2017 »
No hijacking at all, I think everyone should chime in on this as its a definite design flaw that needs addressing . Any and all comments and fix ideas are welcome.This is what this site is for , to look out for our brethren .
« Last Edit: Sep 07, 2017 by Speed N976DH »

mhflyit

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Re: Bent Bolts
« Reply #8 on: Sep 07, 2017 »
Through bolts Wafer or steel straps?
Matt

wafer

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Re: Bent Bolts
« Reply #9 on: Sep 08, 2017 »
The LS and LTS (and I assume LT) plans call for 4 through bolts; 2 per side. 

The location of the gear in the nose dragger config is so close to the main spar, there is not enough room to mount the gear in a strap configuration.
Mike "Wafer" Then
SII LTS

mhflyit

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Re: Bent Bolts
« Reply #10 on: Sep 08, 2017 »
Ah, yes...for the nose dragger. Mine was originally in this configuration with 80hrs. I sand blasted the the frame during the restoration and witnessed no cracking in this area...another point of reference. I restored the plane to a tail-wheel configuration.
Matt

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Re: Bent Bolts
« Reply #11 on: Sep 08, 2017 »
Wafer, exactly where are the cracks?  In the longeron tubes, along the bushing weld lines (vertical and/or horizontal), or in the mounting bushings?  In what direction do they seem to be progressing?  Do you have any pictures?

One of the concerns I had with the thru-gear method is that the bushings really need to be filed exactly flush with the reinforcement plates.  If not, then the gear would not be making firm contact with the bottom of the reinforcement plates so the landing loads can be transferred along its entire face.  If the bushings stick out even a small amount, then excessive landing loads are going through the bushing & weld, before being transferred to the longerons (resulting in a torsional load to the vertical welds).  The bushings & bolts really should just keep the gear from falling off, not taking on the (vertical) hammering that occurs during even the best landing.

O'Bill
« Last Edit: Sep 08, 2017 by wbpace »

wafer

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Re: Bent Bolts
« Reply #12 on: Sep 11, 2017 »
In the tubes mostly, not the bushing themselves.  .035 is not thick.
Mike "Wafer" Then
SII LTS

Chucker

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Re: Bent Bolts
« Reply #13 on: Sep 15, 2017 »
Just to round-out this discussion....can anyone tell me if the strap configuration suffered any similar problems?

I am building a mid-wing and the gear is held on with 1/4" straps.  It appears that the straps will accept some of the bending forces when the gear is flexed.

1.  Is the strap flex enough to prevent the bending of bolts and cracking of bushings and welds?
2.  Would it be advisable to only tighten the clamping bolts to a snug fit and avoid preloading the straps?
3.  The Original plans call for drilling only one of the two straps.  I assume that hole is for an alignment bolt.  I don't understand why you would not want an alignment bolt on each side.  If there is only to be one alignment bolt, then the straps would need to be tight enough to prevent sliding fore and aft.  Are people using alignment bolts on both sides?


Soneraifred

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Re: Bent Bolts
« Reply #14 on: Sep 15, 2017 »
My original IIL has 1/4" 4130 straps securing the gear to the fuselage. It now has more than 1550 hours over 31 years of flying, and probably over 2000 landings, many on grass.  There are no problems with the attachment points on the fuselage.  The bolts are torqued to the standard spec.  The single AN3 bolt thru the LH strap and the gear is there to prevent the gear from sliding sideways when the gear is side loaded.  Only one is needed.
Fred Keip
Owner-SoneraiWorks LLC
Sonerai Newsletter Editor-Retired
Sonerai IIL, N99FK

 

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