Landing gear bolt broke
Posted: Fri Mar 03, 2023 9:27 am
by Rofomoto
Just landed at home airport, as I turned off runway bolt broke and gear spins in mount. Easy fix with only wheel pant damage but going to change all gear bolts at each condition inspection.
Re: Landing gear bolt broke
Posted: Fri Mar 03, 2023 10:00 am
by GordonTurner
Bummer. Glad you’re ok. Glad you’re at home. How many landings so far, and all pavement or some mix? Sounds like it was upper bolt?
How’s that Corvair treating you? I’ve watched your videos, thanks for sharing those.
Cheers, Gordon
Re: Landing gear bolt broke
Posted: Fri Mar 03, 2023 1:36 pm
by Bryan Cotton
Billy, I’d also be interested to know how many hours and landings you have. I’m at 62 hours and maybe a couple hundred landings. I’ll have to check my logbook.
Re: Landing gear bolt broke
Posted: Fri Mar 03, 2023 1:46 pm
by rbarber
I have ~1200 hours, on the original bolts for mine (Stainless) . No slop or issues. FWIW, my landings are not pretty, as I always practice short steep approaches. So I am wondering what may be the cause?
R.
Robert E. Barber
N157SX, Gen 4 3300, ~1200 hrs
Re: Landing gear bolt broke
Posted: Fri Mar 03, 2023 3:38 pm
by daleandee
rbarber wrote:I have ~1200 hours, on the original bolts for mine (Stainless) . No slop or issues. FWIW, my landings are not pretty, as I always practice short steep approaches.
I don’t have near your amount of time (~300 hours) and I fly from pavement mostly but have a few grass fields I visit. So far no slop or issues.
I did replace the stainless bolts for cad plated steel per the Sonex bulletin (SNX-SB-006).
Dale
3.0 Corvair, Tailwheel
Re: Landing gear bolt broke
Posted: Fri Mar 03, 2023 3:48 pm
by Bryan Cotton
I see no slop yet. I had to teach myself how to fly a Waiex, and then taught my son. I’ve been pretty pleased with the durability of the airplane.
Re: Landing gear bolt broke
Posted: Fri Mar 03, 2023 9:15 pm
by Sonex1243
I installed cad plated steel as well per the SB. I have a little wiggle/slop on the lower end where the gear rod fits into the steel axle mount. Have you guys seen this and if so, what did you end up doing? I am thinking of bonding the two together with something to fill the cavity to stiffen it up but also enable removal if needed.
Re: Landing gear bolt broke
Posted: Fri Mar 03, 2023 9:18 pm
by Rofomoto
GordonTurner wrote:Bummer. Glad you’re ok. Glad you’re at home. How many landings so far, and all pavement or some mix? Sounds like it was upper bolt?
How’s that Corvair treating you? I’ve watched your videos, thanks for sharing those.
Cheers, Gordon
85 hours. Mostly hard surface.. 200 or so landings. Don’t forget I did 4 months of high speed taxi test. Lol
Corvair is perfect for this plane.
Re: Landing gear bolt broke
Posted: Fri Mar 03, 2023 9:36 pm
by Bryan Cotton
Sonex1243 wrote:I installed cad plated steel as well per the SB. I have a little wiggle/slop on the lower end where the gear rod fits into the steel axle mount. Have you guys seen this and if so, what did you end up doing? I am thinking of bonding the two together with something to fill the cavity to stiffen it up but also enable removal if needed.
My axles and both joints on my tailwheel had slop during the build. I used metlweld to bond them.
https://www.aircraftspruce.com/catalog/ … ckkey=6039
The ti legs in the motor mount sockets were tight and I didn’t bond them.
Edit:
viewtopic.php?f=39&t=578&start=410
Re: Landing gear bolt broke
Posted: Fri Mar 03, 2023 11:27 pm
by Skippydiesel
Rofomoto wrote:Just landed at home airport, as I turned off runway bolt broke and gear spins in mount. Easy fix with only wheel pant damage but going to change all gear bolts at each condition inspection.
Hi Bryan - please elaborate what/which bolt (s) is this? Photo/sketch might help.
Re: Landing gear bolt broke
Posted: Sat Mar 04, 2023 2:01 am
by Kai
We have had some experience with broken upper gear leg bolts up here as well. When this happened the first times, we stuck to the SB and replaced the stainless bolts with AN types. In addition, we safetied the bolts in such a way that the lower part of a broken bolt could not fall out (for some reason the bolts always seem to break in the middle). This would bar the titanium leg from rotating and cause a calamity.
However, the problem persisted as discovered during periodic maintenance. It appeared that the suggested 1/4 inch bolts just could not handle the torque loads imposed on the gear legs by the wheel geometry. What we then did was to ream out the upper holes in gear leg and engine mount to 5/16 inch (8mm), and replace the AN4 with Unbrako 12.9 class bolts and long nuts. The whole assembly was torqued up to a considerable pre load on the bolts (12.9 class bolts are extrmely strong!)
After this, the issue went away, and we have been flying happily the last years. Remains the question why the original bolts would break in the first place. We can only speculate that for some reason we could not get the wheel geometry aligned exactly to plans, and that his imposed excessive loads on the bolts.
Re: Landing gear bolt broke
Posted: Sat Mar 04, 2023 2:36 am
by Bryan Cotton
Skippydiesel wrote:
Rofomoto wrote:Just landed at home airport, as I turned off runway bolt broke and gear spins in mount. Easy fix with only wheel pant damage but going to change all gear bolts at each condition inspection.
Hi Bryan - please elaborate what/which bolt (s) is this? Photo/sketch might help.
That was Billy’s post. I assume it is the bolt that goes through the top of the gear leg in the motor mount. Others have busted this bolt before. Sometimes just one side and they find it during maintenance.
Re: Landing gear bolt broke
Posted: Sat Mar 04, 2023 7:46 am
by GraemeSmith
At my Condition Inspection this year I replaced a bottom axle bolt due to some slop developing and replaced the other axle bolt because I was changing an axle (the little tang to hold the brake shoe mount had cracked). With both bottom ones done - I replaced the tops leg retaining bolts while I was at it. Both showed very slight wearing off of the CAD plating on the AN bolts (builder skipped stainless and went straight to AN).
620 landings by me
??? landings by builder in first 185 hours.
564 hours TTAF
Re: Landing gear bolt broke
Posted: Sat Mar 04, 2023 8:05 am
by Skippydiesel
Bryan Cotton wrote:
Skippydiesel wrote:
Rofomoto wrote:Just landed at home airport, as I turned off runway bolt broke and gear spins in mount. Easy fix with only wheel pant damage but going to change all gear bolts at each condition inspection.
Hi Bryan - please elaborate what/which bolt (s) is this? Photo/sketch might help.
That was Billy’s post. I assume it is the bolt that goes through the top of the gear leg in the motor mount. Others have busted this bolt before. Sometimes just one side and they find it during maintenance.
My apologies Billy/Bryan - would still like an image or two to clarify where the problem(s) occurred.
Re: Landing gear bolt broke
Posted: Sat Mar 04, 2023 9:15 am
by GraemeSmith
Skippydiesel wrote:My apologies Billy/Bryan - would still like an image or two to clarify where the problem(s) occurred.
If you see this post in the Sonex Forum on FB You can see Day 5 of my just finished Condition Inspection where I cover replacement of those top bolts (with pictures). Pretty sure those are the ones they are talking about.
https://www.facebook.com/photo/?fbid=10 … 3445473443
Re: Landing gear bolt broke
Posted: Sat Mar 04, 2023 10:37 am
by Rofomoto
The top bolt sheared both ends off of the AN4 bolt. When I removed the titanium rod, the center of the bolt slid out.
The plans call for tightening bolt and then backing off a little with a castellated nut and Cotter pin. I looked at B model plans and the call for elastic nut.
Re: Landing gear bolt broke
Posted: Sat Mar 04, 2023 11:22 am
by mccool
It was my understanding that Cad plated bolts should not be used in the Titanium gear legs
Re: Landing gear bolt broke
Posted: Sat Mar 04, 2023 1:43 pm
by tps8903
mccool wrote:It was my understanding that Cad plated bolts should not be used in the Titanium gear legs
I use exclusively grass fields. I think I’ve been convince to ream to 5/16" during my Condition inspection and use the stronger NAS6605 series Bolts. I might even do it sooner time permitting. I just changed the Stainless ones out last month before my first flight. So hopefully they will be good for a few hours. Think I’m just going to drill through the firewall, use 3 washers on the backside for the tight space then seal it with RTV before tightening.
Re: Landing gear bolt broke
Posted: Sat Mar 04, 2023 6:35 pm
by Skippydiesel
GraemeSmith wrote:
Skippydiesel wrote:My apologies Billy/Bryan - would still like an image or two to clarify where the problem(s) occurred.
If you see this post in the Sonex Forum on FB You can see Day 5 of my just finished Condition Inspection where I cover replacement of those top bolts (with pictures). Pretty sure those are the ones they are talking about.
Thanks for the try Graeme - not on “FB” Trying hard to stay not connected. Being addicted to this Forum is more than enough:)
Re: Landing gear bolt broke
Posted: Sun Mar 05, 2023 7:36 pm
by n502pd
Kai wrote:We have had some experience with broken upper gear leg bolts up here as well. When this happened the first times, we stuck to the SB and replaced the stainless bolts with AN types. In addition, we safetied the bolts in such a way that the lower part of a broken bolt could not fall out (for some reason the bolts always seem to break in the middle). This would bar the titanium leg from rotating and cause a calamity.
However, the problem persisted as discovered during periodic maintenance. It appeared that the suggested 1/4 inch bolts just could not handle the torque loads imposed on the gear legs by the wheel geometry. What we then did was to ream out the upper holes in gear leg and engine mount to 5/16 inch (8mm), and replace the AN4 with Unbrako 12.9 class bolts and long nuts. The whole assembly was torqued up to a considerable pre load on the bolts (12.9 class bolts are extrmely strong!)
After this, the issue went away, and we have been flying happily the last years. Remains the question why the original bolts would break in the first place. We can only speculate that for some reason we could not get the wheel geometry aligned exactly to plans, and that his imposed excessive loads on the bolts.
Do you have the part numbers for the 12.9 spec hardware you used? I have looked at the Unbrako catalogue, and there are quite a few different ones. I have complied with the SB from sonex before first flight, but the rough grass strip has me worried now!! this inspection I will investigate bolt integrity, and if I can get the stronger bolts, I shall get them in place. Otherwise, I have had zero problems in this area, and am now at a 9000ft hard surfaced ex USAF base! Kind of neat just because of that. Any help with the bolts would be appreciated! Thanks much!
Re: Landing gear bolt broke
Posted: Mon Mar 06, 2023 4:31 am
by Kai
Joe,
We used ordinary Unbrako class 12.9 capscrews with mm thread. Our selection was based on our reaming out the holes in the engine mount and the gear legs to ø8mm (mind you, not cleared by Sonex tech, but we felt we had to do something). The thread length of the smaller dimension Unbrako´s is 28mm. For a 50mm shank, this would indicate a M8x1.25x80 capscrew bolt. According to the US Unbrako datalog, this carries part# 103070. You will have to check your engine mount for the exact shank length of the bolt.
Re: Landing gear bolt broke
Posted: Mon Mar 06, 2023 10:13 am
by DCASonex
While building, I noticed what i thought was a bit too lose a fit for my bolts and after contacting Sonex, enlarged the holes for a tight fit on 5/16" bolts. No hint of any loosening despite many not very pretty landings. Info from Sonex at the time they changed to plain cad plated bolts, was that they initially followed the advise that Cadmium should not be used with Titanium, but on further investigation, when broken bolts started showing up, was that Cadmium with Titanium is only a problem at elevated temperatures.
David A.
Re: Landing gear bolt broke
Posted: Tue Mar 07, 2023 1:11 am
by peter anson
mccool wrote:It was my understanding that Cad plated bolts should not be used in the Titanium gear legs
Yes, the various standards say it’s a no-no although it’s mainly a problem at higher temperatures. I was not happy about using cad plated bolts so used 1/4" 12.9 Unbrakos. Had to use pretty long ones to get enough unthreaded shank. I changed them recently after more than 800 landings. I think it’s worth gluing the joints too. On original assembly I used PR1422, a rubbery fuel tank sealant which despite its purpose of only sealing fuel tanks is enormously strong. When I recently reassembled things I used Loctite because that’s what I had in the tool kit. Some types of Loctite can fill fairly big gaps.
Peter
Re: Landing gear bolt broke
Posted: Tue Mar 07, 2023 3:28 am
by Skippydiesel
I am not the origional builder and may have my “wires” crossed but think I may have a Grove undercarriage - do these bolt concerns include Grove?
Re: Landing gear bolt broke
Posted: Wed Mar 08, 2023 4:54 pm
by n502pd
Kai wrote:Joe,
We used ordinary Unbrako class 12.9 capscrews with mm thread. Our selection was based on our reaming out the holes in the engine mount and the gear legs to ø8mm (mind you, not cleared by Sonex tech, but we felt we had to do something). The thread length of the smaller dimension Unbrako´s is 28mm. For a 50mm shank, this would indicate a M8x1.25x80 capscrew bolt. According to the US Unbrako datalog, this carries part# 103070. You will have to check your engine mount for the exact shank length of the bolt.
Thanks much! come condition inspection time I will take a real close look at my original bolts for indications of movement. question, where did you get the reamer?
And another question.. did you also do the axel bolts to 5/16Th too? TKS!
Re: Landing gear bolt broke
Posted: Wed Mar 08, 2023 8:49 pm
by Skippydiesel
Skippydiesel wrote:I am not the origional builder and may have my “wires” crossed but think I may have a Grove undercarriage - do these bolt concerns include Grove?
I did get my wires crossed - my Sonex has Tracy O’Brien legs - however question still valid.
Re: Landing gear bolt broke
Posted: Sat Mar 11, 2023 10:56 am
by mike.smith
Nearly 600 hrs on my airframe. No issues with the gear bolts. Cad plated per Sonex. Cad plated and titanium is a non-issue at the most severe temperatures human being and airplanes are exposed to.
Re: Landing gear bolt broke
Posted: Sat Mar 11, 2023 11:32 am
by Bryan Cotton
I’m curious why some people have issues and some don’t. Is it a bolt fit issue? For those with broken bolts, how easy are those bolts to put in? Same question for the guys with higher hours on one set of bolts.
I think I had to tap mine in with the light plastic hammer. Snug fit.
Re: Landing gear bolt broke
Posted: Sat Mar 11, 2023 3:03 pm
by Kai
n502pd wrote:
Thanks much! come condition inspection time I will take a real close look at my original bolts for indications of movement. question, where did you get the reamer?
And another question.. did you also do the axel bolts to 5/16Th too? TKS!
Joe,
This is Europe- getting your clammy hands on a ø8mm metric reamer, is not rocket sience. And no, we did not do the axle bolts, although we replaced the original stainless ones with AN4 as suggested by Sonex SB, which were again substituted with 1/4 in Unbrako 12.9.
Kai
Re: Landing gear bolt broke
Posted: Sat Mar 11, 2023 3:22 pm
by Kai
Bryan Cotton wrote:I’m curious why some people have issues and some don’t. Is it a bolt fit issue? For those with broken bolts, how easy are those bolts to put in? Same question for the guys with higher hours on one set of bolts.
I think I had to tap mine in with the light plastic hammer. Snug fit.
Bryan,
I already aired the same in a previous post. Although I can´t be sure, my gut feeling is that this is not a bolt fit issue. I am looking more towards the way the axles are oriented in the airframe. Pure speculation from my side, but I would expect excessive induced gear leg torque issues if the axles are not aligned exactly according to instructions in the drawing. I don´t know, I am still on the same set of anno 2006 Aerotrainer tires: wear is minimal.
This is in direct contrast to comments from Kerry. When he learned that we were operating on fairly rough grass fields, he maintained that while operation on a flat and even grass surface was certainly within the design capabilities, the plane had never been intended for operation on rough grass surfaces.
Whatever the cause- after we went Unbrako 12.9 the issue went away.
Kai
Re: Landing gear bolt broke
Posted: Sat Mar 11, 2023 4:53 pm
by rbarber
I had to tap them in (they were snug), but otherwise done as the original specifications. I did take more than a little care getting the 0.7 degrees of toe in correct. I land on both grass and pavement, and anyone who has seen my landings would laugh hard if someone accused me of good landings. It may be worth mentioning that my gear legs are slightly longer than the specified length, less than an inch, IIRC. I doubt that would make any real difference. The mystery remains…
R.
Sonex 271, N157SX (Sexy Hexy)
1200 hrs (and a lot of crappy landings) on the original SS bolts.
Re: Landing gear bolt broke
Posted: Sat Mar 11, 2023 10:37 pm
by n502pd
Thanx for the update! axel bolt upgrade was what i was mostly interested.
Re: Landing gear bolt broke
Posted: Mon Mar 13, 2023 6:07 pm
by Skippydiesel
Skippydiesel wrote:
Skippydiesel wrote:I am not the origional builder and may have my “wires” crossed but think I may have a Grove undercarriage - do these bolt concerns include Grove?
My Sonex has Tracy O’Brien legs
Is there a well informed Sonex person, who might tell me if the central topic of this thread/conversation, includes TO’B legs ???
Re: Landing gear bolt broke
Posted: Tue Mar 14, 2023 12:41 am
by sonex892.
Skippydiesel wrote:
Skippydiesel wrote:
Skippydiesel wrote:I am not the origional builder and may have my “wires” crossed but think I may have a Grove undercarriage - do these bolt concerns include Grove?
My Sonex has Tracy O’Brien legs
Is there a well informed Sonex person, who might tell me if the central topic of this thread/conversation, includes TO’B legs ???
I dont know about well informed. The one thing I do know for sure is he sold welded axles to fit on the titanium legs. These are virtually the same as sonex, except they had hollow axles and were made for their wheels and brakes. I think they also sold complete steel gear legs that would bolt to the engine mount the same as the standard titanium rod but the axle bolt is ommitted as it is part of the gear leg.
So do you have titanium legs with a 1/4" bolt in the axle and one 1/4" bolt in the engine mount? If yes. “It is the same as a Sonex”
Do you have steel legs with a 1/4" bolt in each leg in the upper engine mount? If yes. “Should only have to worry about the top bolt”
Steve