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Nose Gear Bolt Failure. Argh!

BillL said:
I must have missed something. How did Inconel bolts become the solution? I am surprised that a high temperature alloy is the answer to a reamed assembly and fitted bolt. The high strength, precision diameter NAS bolts listed earlier at $2.86 each.
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Not a solution in itself,but part of a system of solutions. Starting with the nose wheel bearing and axle issue,truing & balancing of out of round tires.The addition of the Anti-Splat brace,precise reaming of the socket for the leg.(chauffeuring)is too strong a word for the hole preparation I prefer "deburring" lightly as we do else where on the plane.Coating the socket and leg with a molybdenum grease and installing a close tolerance Inconel bolt with the help of a plastic hammer into a carefully reamed to sized hole. I would like to add here,the shoulder of this bolt should extend past the shear points,perhaps the self centering washers mentioned in earlier posts would be appropriate. This is what I taken away from this thread so far,Good thread keep it coming. IMHO
RHill
 
Mike S said:
So, has anyone asked the factory what they think of using a vastly stronger bolt in this location??

Anyone considered that this may be a designed in failure point to protect other parts of the airframe??

No idea one way or the other, just rambling.............but might be good to know;)
Click to expand...

Exactly the type of rambling that was going thur my head and I tend to agree with.
 
Mike S said:
So, has anyone asked the factory what they think of using a vastly stronger bolt in this location??

Anyone considered that this may be a designed in failure point to protect other parts of the airframe??

No idea one way or the other, just rambling.............but might be good to know;)
Click to expand...

In most cases I would agree, With the nose gear all bets are off,The factory has done all it can and will do.Anything happens to your nose gear its pilot error,you should have held the nose off the ground.If a $75 bolt saves a $7300 prop and a tare down inspection + parts,another $7K,well worth the risk.Chances are the nose leg will bend like a pretzel at the slightest provocation and hopefully you'll know something is a miss before the prop hits the ground.IMHO
RHill
 
Just a thought, if the fork 'Stop' was/is installed backwards (which I have seen) it limits the turning angle of the nose wheel significantly which could cause this problem.

In either case, stop installed correctly or not, if the fork is up against the stop but you continue forcing it around a tighter turn that it is able (tire is being pushed sideways) and the wheel cannot pivot anymore, all the twisting force is going to be applied to that bolt.
 
Walt said:
Just a thought, if the fork 'Stop' was/is installed backwards (which I have seen) it limits the turning angle of the nose wheel significantly which could cause this problem.

In either case, stop installed correctly or not, if the fork is up against the stop but you continue forcing it around a tighter turn that it is able (tire is being pushed sideways) and the wheel cannot pivot anymore, all the twisting force is going to be applied to that bolt.
Click to expand...

Interesting thought.... I asked the same question the morning the photos hit VAF.
It wouldn't necessarily be an issue on a single event, It could excessively load the bolt repeatedly until it fully failed.

I would like to see a photo of the leg/fork with the wheel fairing removed.

If the stop bracket is installed correctly, it shouldn't ever be able to side load the nose gear leg while locking one wheel for a pivot turn, the turn angle of the fork is slightly short of hitting the stop when making a turn pivoting on one wheel.
 
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More about Inconel

A little more info about bolt fatigue and the Inconel bolt I suggested in my earlier post. Since I don't have an "A" model airplane, I can still only see from the pictures there is only one bolt in the gear leg, similar to the individual legs on my -4. From an engineering standpoint, the failure of a bolt loaded in shear is usually from one of two things..either it is too weak, or there is some level of relative movement, which in time leads to fatigue/shear. Fatigue is hard to predict at design conception, but shows in service and can be aggravated by corrosion, torque values,ect. As I stated earlier, the big plane guys have utilized the Inconel BACB30US bolt as the most robust, durable and corrosion resistant bolt for high load/fatigue prone assemblies.High strength bolts installed in steel structure are seldom if ever installed in "interference" fit, as the bolt will gall and seize during installation unless frozen to well below what we can do at home. The installation should be "close tolerance",which is achievable using normal reaming processes.There are oversize US bolts available as well in the event a hole is buggered up. Van is a superior engineer, and I have no doubt he knows about Inconel bolts, but they are expensive and in design, they aren't really required for static and dynamic strength for the loads implied on an RV.I 'm not sure if he reads these posts, but it wouldn't hurt to inquire the factory.
 
RV6_flyer said:
This is not the first nose gear bolt to break. We had one a couple of years ago at the Capital City Air Show on one of the show formation aircraft (RV-6A). The nose gear bolt broke without the engine running while moving the aircraft if I remember correctly. It was fixed in less than an hour. The aircraft did fly in the air show after the fix. Since the engine was not running, the prop did come in contact with the ground.
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Yea, that was me- engine was running and heard the "pop" after a flank turn.
No Prop strike- the front leg stayed in position sorta since I held the brakes and shut it down. Replaced the bolt at the show- Then machined to one size larger for a close fit later. I would recommend the larger size in close tolerance. OR the Inconel bolt route- that is probably best. The sharp(flank) turns is probably the stress point for these bolts. Replace every 750 hours probably a good procedure if doing formation flank turns.
 
rvbuilder2002 said:
If the stop bracket is installed correctly, it shouldn't ever be able to side load the nose gear leg while locking one wheel for a pivot turn, the turn angle of the fork is slightly short of hitting the stop when making a turn pivoting on one wheel.
Click to expand...

When the nose gear fork is deflected, the normal force at the tire contact patch is offset a significant distance (10 inches?) from the center plane, creating a twisting moment about the axis of the gear leg socket and generating high shear loads on the bolt, even if the fork isn't against the stop.
Roger
 
BillSchlatterer said:
And, that particular bolt doesn't really set up correctly because it's a flat head on a round surface which means it only has two bearing/pressure points under the bolt head and on the nut as well. It might be that one of those special washers with a flat surface on one side and the other matched to the nose gear barrel might help ? I think if you look at the picture, it sort of looks like a stress failure and not shear but it's hard to tell ?? It had to shear somewhere otherwise it wouldn't spin in the barrel but I wonder which happened first ?

Just thinking someone might offer an expert opinion :confused:
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I'm not an expert but i noticed a little play in my 7 main gear after about 200hrs. When I replaced the bolts I also had washers made as you described, contoured on one side. Now 400hrs later the leg gear has remained tight. This is a tail dragger,however.
 
RKellogg said:
When the nose gear fork is deflected, the normal force at the tire contact patch is offset a significant distance (10 inches?) from the center plane, creating a twisting moment about the axis of the gear leg socket and generating high shear loads on the bolt, even if the fork isn't against the stop.
Roger
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I agree (though because of the pivot angle stops, I think the offset is more on the order of 6" at max deflection, but I have never measured it) .
I was speaking in the context of normal operation and an acceptable level of load... I.E. not adding extra side (torsion) load on the nose gear leg than is normally experienced by A model RV's .
We all know that there is some level of load induced on the leg; otherwise all that would be needed to hold it in place would be an allen set screw.

As has been mentioned countless times here in the forum (by many, not just me), do not loose sight of the big picture.

There are thousands of A model RV's flying with this style of nose gear attachment. Of those, I am only aware of 2 bolt failures that occurred during seemingly benign ground operations. That small a number... in thousands currently operating, indicates (to me at least) something specific about those two airplanes.
I have not crunched any numbers, but to me it is doubtful that in these two instances, the bolt failed as a result of a single load event, or even multiple events of the normal expected loads (see my comment above about thousands of "A" models flying).
I would be very interested in seeing close up high res. photos of the bolt ends.
I am pretty confident that it would show evidence of progressive fatigue failure through a major portion of the cross section, with the final flank turn finishing it off.
There is a lot of different issues that could induce a fatigue failure, but a couple of prominent ones would be a loose fit of the bolt in the bore, and nose wheel shimmy. Add those two together on a single airplane and it would be that much worse. Throw flank turns into the mix on regular basis and it is worse still. Then there is still the possibility of an incorrectly installed fork pivot stop bracket. Hopefully everyone here knows that the "T" portion of the bracket is supposed to be pointing fwd. It would be interesting to here how many people check and find theirs pointing aft.

I hope I don't sound like I am downplaying the event. It is sad to see any RV get damaged, and have the owner have to deal with the cost and trouble of repairs. Just pointing out that 2 out of 2000+ (<.1%) is a very small #, that is likely preventable by just making sure the standard AN bolt is a tight fit when installed. Then doing regular inspections to make sure it is staying that way. Any amount of looseness is cause for concern. Also consider any level of nose wheel shimmy a serious event and unacceptable.
 
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I did read through this thread rather quickly, but what I took away from some of the back-of-the-envelope calculations is that it seems a wheel turned 90 degrees and pushed on with a 500-600lb force would be adequate to shear the bolt... did I get that right?

I'd be surprised if that doesn't happen quite regularly in many nosewheel RV's. Start a sharp turn, get part way around, and then need to stop quick for some reason. Both brakes, your nose dips, and your forward momentum loads up that nosewheel something fierce as you come to a stop. A formation team that does a flank turn (as someone mentioned) may do this on every other flight.

Someone pointed out that the forces shouldn't get that high on an 1100lb plane... But it's really an 1800lb plane when loaded, right? Someone else said that their static nosewheel load was 300lb. You could easily double that with only light braking... I could easily see the load getting spread 600lb to a wheel if you stopped quick.
 
rvbuilder2002 said:
I agree (though because of the pivot angle stops, I think the offset is more on the order of 6" at max deflection, but I have never measured it) .
I was speaking in the context of normal operation and an acceptable level of load... I.E. not adding extra side (torsion) load on the nose gear leg than is normally experienced by A model RV's .
We all know that there is some level of load induced on the leg; otherwise all that would be needed to hold it in place would be an allen set screw.

As has been mentioned countless times here in the forum (by many, not just me), do not loose sight of the big picture.

There are thousands of A model RV's flying with this style of nose gear attachment. Of those, I am only aware of 2 bolt failures that occurred during seemingly benign ground operations. That small a number... in thousands currently operating, indicates (to me at least) something specific about those two airplanes.
I have not crunched any numbers, but to me it is doubtful that in these two instances, the bolt failed as a result of a single load event, or even multiple events of the normal expected loads (see my comment above about thousands of "A" models flying).
I would be very interested in seeing close up high res. photos of the bolt ends.
I am pretty confident that it would show evidence of progressive fatigue failure through a major portion of the cross section, with the final flank turn finishing it off.
There is a lot of different issues that could induce a fatigue failure, but a couple of prominent ones would be a loose fit of the bolt in the bore, and nose wheel shimmy. Add those two together on a single airplane and it would be that much worse. Throw flank turns into the mix on regular basis and it is worse still. Then there is still the possibility of an incorrectly installed fork pivot stop bracket. Hopefully everyone here knows that the "T" portion of the bracket is supposed to be pointing fwd. It would be interesting to here how many people check and find theirs pointing aft.

I hope I don't sound like I am downplaying the event. It is sad to see any RV get damaged, and have the owner have to deal with the cost and trouble of repairs. Just pointing out that 2 out of 2000+ (<.1%) is a very small #, that is likely preventable by just making sure the standard AN bolt is a tight fit when installed. Then doing regular inspections to make sure it is staying that way. Any amount of looseness is cause for concern. Also consider any level of nose wheel shimmy a serious event and unacceptable.
Click to expand...

If I remember correctly, the other bolt failure was at the threaded portion suggesting the bold was not long enough. I don?t have enough technical knowledge to know the bolt sheer strength at the threaded portion verses the grip portion but when I replaced mine, I made sure the grip was just visible with the use of washers to ensure the nut is not bottoming out.
 
Snowflake said:
I did read through this thread rather quickly, but what I took away from some of the back-of-the-envelope calculations is that it seems a wheel turned 90 degrees and pushed on with a 500-600lb force would be adequate to shear the bolt... did I get that right?

I'd be surprised if that doesn't happen quite regularly in many nose wheel RV's.
Click to expand...

If that were the case, and it did happen regularly on "A" model RV's, then the VAF forums would be full of threads like this one.
 
Bavafa said:
If I remember correctly, the other bolt failure was at the threaded portion suggesting the bold was not long enough. I don?t have enough technical knowledge to know the bolt sheer strength at the threaded portion verses the grip portion but when I replaced mine, I made sure the grip was just visible with the use of washers to ensure the nut is not bottoming out.
Click to expand...

I don't remember any details, but if that was the case, the bolt may not have been tight in the bore at the shear zone at the nut end. The diameter of aircraft grade bolts starts to reduce slightly, before it gets to the threaded zone.
 
Bavafa said:
If I remember correctly, the other bolt failure was at the threaded portion suggesting the bold was not long enough.
Click to expand...

That is what I remember also.

Tried to find the old thread, but no joy-----but then I did not put in a lot of effort either.
 
My Feb 2014 bolt failure

Same thing happened to me in Feb as I was finishing a 180 degree pivot on a taxiway. I did talk to Vans guys at Osh this year and brought it up at a Mike Busch seminar. Busch said since I was at idle he would have recommended a temp prop replacement and fly it home for full repairs.

c5c28ee6e806d3284c01fe0471d20646_zps8e09ffcd.jpg


8e0dcf7af5be32d31e357407e8f0b025_zps82cfa064.jpg


Here is the picture from my nut end of the AN5. The nut was sitting on the taxiway.

a440727f000b2f8fc49212172472066d_zpsd1d29995.jpg


09bb0fe43c6ed111f588d7bfe341b81e_zpsa3e076be.jpg


The head of the bolt had departed sometime/somewhere earlier.

647b316a4545078833dab0cfc09065b8_zps0fa44c73.jpg


It broke in Feb and I'm almost done with the repairs.
 
Flytoday, thanks for posting those pictures, and I'm glad you are almost back in the air.

It does appear that the travel limit weldment was on backwards on your plane, which is a likely cause of bolt fatigue as mentioned by Scott in an earlier post. Perhaps compounding the problem is that the thread area of the bolt was involved in the shear area (unless a stack of washers was used under the nut). It is important to use a length of bolt long enough to insure that no threads are in the gear socket.

Regarding the reply which tried to refute what I wrote in a previous post in this thread, I would encourage a more careful reading of what I wrote, both in this thread's earlier post and in posts from quite some years ago about this topic.
 
flytoday said:
Same thing happened to me in Feb as I was finishing a 180 degree pivot on a taxiway.

It broke in Feb and I'm almost done with the repairs.
Click to expand...

Ouch. A two-dollar bolt can ruin an entire flying season. Thanks for the detailed photos. I have been warned. Still need to implement a significant, reasonable fix.

Just to clarify, FlyToday, are you the second or the third occurance reported in this thread? How many hours on that bolt?
- Roger
 
RKellogg said:
Ouch. A two-dollar bolt can ruin an entire flying season. Thanks for the detailed photos. I have been warned. Still need to implement a significant, reasonable fix.

Just to clarify, FlyToday, are you the second or the third occurance reported in this thread? How many hours on that bolt?
- Roger
Click to expand...

Third RVA + one KIS in this thread. If you have an A ,have someone hold the tail down and give the NGL a shake before your next flight.Its less work than opening the fuel cap and looking to see if you have any!
RHill;)
 
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rhill said:
Third RVA + one KIS in this thread. If you have an A ,have someone hold the tail down and give the NGL a shake before your next flight.Its less work than opening the fuel cap and looking to see if you have any!
RHill;)
Click to expand...

Or better yet, see if the nose wheel travel limit weldment is on correctly.
 
Flytoday Reply - my bolt fail

RKellogg said:
Ouch. A two-dollar bolt can ruin an entire flying season. Thanks for the detailed photos. I have been warned. Still need to implement a significant, reasonable fix.

Just to clarify, FlyToday, are you the second or the third occurance reported in this thread? How many hours on that bolt?
- Roger
Click to expand...

The plane was first flown in 1995. I'm the third owner, 750 hours when I purchased it in 2011, and now it's got about 1200 hours TTAF. I think I'll replace this bolt regularly.

I've had the engine torn down (no damage noted from prop strike), and I'm going to a Catto 3-blade. Constant speed replacement was out of my budget.

I'm the incident that BillR referred to on page 2, and he helped me get back to the hanger at my home field. Thanks Bill and Lone Star Squadron! Really blessed this didn't happen on a cross-country!

Here is the link to the thread from earlier this year.
 
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flytoday said:
The plane was first flown in 1995. I'm the third owner, 750 hours when I purchased it in 2011, and now it's got about 1200 hours TTAF. I think I'll replace this bolt regularly.

I've had the engine torn down (no damage noted from prop strike), and I'm going to a Catto 3-blade. Constant speed replacement was out of my budget.

I'm the incident that BillR referred to on page 2, and he helped me get back to the hanger at my home field. Thanks Bill and Lone Star Squadron! Really blessed this didn't happen on a cross-country!

Here is the link to the thread from earlier this year.
Click to expand...

Interesting timing. My KIS had 1100hrs TTAF when I had the nose gear bolt failure. I wonder how many hours were on the other aircraft when they had the failure.

I also went with the CATTO 3 bladed composite propeller which is 20lbs lighter than the Sensenich aluminum prop it replaced. This takes some weight off the nose gear, and in my case, moves the CG 5/8" further aft helping the CG location which was slightly nose heavy. Under some circumstances I would actually run out of nose up trim just before landing.

:cool:
 
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My RV-6A drawings say

AN5-20A bolt, AN960-516 Washer, and MS21045-5 All-metal lock nut --- is there agreement that this is the correct setup? If so, in the middle of my condition inspection and will change out the setup.

Ron

EDIT: - I got this info from the plans CD I recently received from Van's ----
 
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Latest drawing?

RONSIM said:
AN5-20A bolt, AN960-516 Washer, and MS21045-5 All-metal lock nut --- is there agreement that this is the correct setup? If so, in the middle of my condition inspection and will change out the setup.

Ron
Click to expand...

I think the latest -6A gear drawing is a REV 3, and it's out at my hanger. So I'm not sure if you are quoting the latest rev....
 
flytoday said:
The plane was first flown in 1995. I'm the third owner, 750 hours when I purchased it in 2011, and now it's got about 1200 hours TTAF. I think I'll replace this bolt regularly.

I've had the engine torn down (no damage noted from prop strike), and I'm going to a Catto 3-blade. Constant speed replacement was out of my budget.

I'm the incident that BillR referred to on page 2, and he helped me get back to the hanger at my home field. Thanks Bill and Lone Star Squadron! Really blessed this didn't happen on a cross-country!

Here is the link to the thread from earlier this year.
Click to expand...

Hopefully you noted the previous post by someone mentioning that in the photo you posted, the nose fork stop bracket is installed wrong. This likely had some level of influence in the bolt failure.
 
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RONSIM said:
AN5-20A bolt, AN960-516 Washer, and MS21045-5 All-metal lock nut --- is there agreement that this is the correct setup? If so, in the middle of my condition inspection and will change out the setup.

Ron

EDIT: - I got this info from the plans CD I recently received from Van's ----
Click to expand...

That is what my 9A plans call for (DWG 46A with R1 dated 4/3/01). I substituted the AN bolt with a NAS6605-26 close tolerance bolt (sourced from Genuine Aircraft Hardware). It required an extra washer.

Picture:
http://www.aclog.com/rv-9a/images/Fuselage/822d4de6ebc506e637cddc6b2d5dac4325663_0527001640.jpg
 
Main Gear vs. Nose Gear

The nose landing gear bolt callout (RV-9A, should be the same as RV-7A) is an AN5-20A and the main landing gear bolt callout is an AN5-22A, so the same diameter - 5/16".

At a gross weight of 1750 lbs, and a nose wheel weight of 325 lbs (per Van's Service Letter November 9, 2007, this leaves 1425/2=713 lbs per main wheel or almost 2.2 x the nose wheel weight.

The main wheels have approximately a 2-1/2" moment arm (visual inspection) from the center of the wheel to the axis of the leg, and react the main landing shock loads, as well as the braking loads. The nose gear leg boss where the AN5 bolt goes through is 1-1/4" diameter and the main gear leg boss where the AN5 bolt goes through is 1-7/16", so the bolt shear radius is not that much greater.

So it seems to me that the main landing gear AN5 bolt has at least as hard a job to do as the nose landing gear AN5 bolt.

I'm puzzled why the nose gear bolt is more prone to failure than the main gear bolt.
 
Another picture

moll780 said:
anyone have any pics of where this bolt exactly is?
Click to expand...

Here is a picture of my old (now replaced) RV-6A engine mount. This is the lower center of the mount. The nose gear strut inserts into the "collar" or "tube" in the center of the picture. The strut is held in place by a single AN5 bolt. The bolt hole is at the upper end of the tube, just below the battery cables coming through the firewall. The bolt goes through the "tube" and the strut inside the "tube". It is a challenge to get at!

f32cd25bfbb48aa220bb9c49c5120b0e_zps8453910a.jpg
 
flytoday said:
Here is a picture of my old (now replaced) RV-6A engine mount. This is the lower center of the mount. The nose gear strut inserts into the "collar" or "tube" in the center of the picture. The strut is held in place by a single AN5 bolt. The bolt hole is at the upper end of the tube, just below the battery cables coming through the firewall. The bolt goes through the "tube" and the strut inside the "tube". It is a challenge to get at!
Click to expand...

Hi Carl,
Sorry you had to go through all this and thank you for sharing.May I ask.Why the mount change? A switch to tail wheel? Was there an issue with the mount after the prop strike?
 
rvbuilder2002 said:
If that were the case, and it did happen regularly on "A" model RV's, then the VAF forums would be full of threads like this one.
Click to expand...
I agree... That suggests the situation doesn't arise that often after all, or there are other factors at play. It is odd that with the wheel at 90 degrees (as in a sharp turn) the bolt appears to only have a 2x factor of safety when just sitting still on the ramp. Hard braking could easily eat up that margin.
 
thank you for the guided explanation of where the bolt resides.


flytoday said:
Here is a picture of my old (now replaced) RV-6A engine mount. This is the lower center of the mount. The nose gear strut inserts into the "collar" or "tube" in the center of the picture. The strut is held in place by a single AN5 bolt. The bolt hole is at the upper end of the tube, just below the battery cables coming through the firewall. The bolt goes through the "tube" and the strut inside the "tube". It is a challenge to get at!

f32cd25bfbb48aa220bb9c49c5120b0e_zps8453910a.jpg
Click to expand...
 
Removing

On mine the head is down and nut up. For removal the orig builder has a small access plate on firewall, which to get bolt out. Odd.
 
drmax said:
On mine the head is down and nut up. For removal the orig builder has a small access plate on firewall, which to get bolt out. Odd.
Click to expand...

I suspect that is the case for most as there is very little room for the nut and too close to the FW.
 
Bavafa said:
I suspect that is the case for most as there is very little room for the nut and too close to the FW.
Click to expand...
What a pita. I'll sift back through this, uh, but had a better replacement come up yet? (not the airliner strength one) I'm just gonna replace the darn thing and move on.
 
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moll780 said:
thank you for the guided explanation of where the bolt resides.
Click to expand...

Happy to help moll780. As a non-builder I often need the big picture, and a close up from 3 inches away doesn't always guide me. I also struggle sometimes with the technical terms.

rhill said:
Hi Carl,
Sorry you had to go through all this and thank you for sharing.May I ask.Why the mount change? A switch to tail wheel? Was there an issue with the mount after the prop strike?
Click to expand...

Here's a picture of the bottom (underside) of the "tube" that holds the strut. So you are looking at the hole where the threads and nut sheared/fell off. This is why I changed the mount. I think the whole kit was approx. $1600. I'm rebuilding and continuing as a -6A.

edb32b1a8c24b7e77c6d0b6e810129e4_zps6c16f4ad.jpg


Carl
 
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Bevan said:
Generally speaking, bolts are installed with the heads up, or forward unless there is a reason to do it the other way around. Such as in this case.

Bevan
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This is true but in cases that there is simply not enough room or other reason, there is an exception made.

In this case, if insert from top, the threaded side of bolt does come very close to the firewall. If you insert the bolt fully first, there is no way of getting the nut in place so Vans suggest to have an access point made so the bolt can be inserted from bottom. Mine goes from top, you only need to keep the nut in place as the bolt exit the hole to get it threaded.
 
Bevan said:
Generally speaking, bolts are installed with the heads up, or forward unless there is a reason to do it the other way around. Such as in this case.

Bevan
Click to expand...

Yes, I understand that convention, I just thought the access hole was a good idea, and might allow torque wrench access.
Thanks!
 
Bevan said:
Generally speaking, bolts are installed with the heads up, or forward unless there is a reason to do it the other way around. Such as in this case.

Bevan
Click to expand...
Titanium bolt cut to length, precisely long enough to get a metal locking nut on bottom. Have not looked that close but I'd run with that.
 
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Bavafa said:
This is true but in cases that there is simply not enough room or other reason, there is an exception made.

In this case, if insert from top, the threaded side of bolt does come very close to the firewall. If you insert the bolt fully first, there is no way of getting the nut in place so Vans suggest to have an access point made so the bolt can be inserted from bottom. Mine goes from top, you only need to keep the nut in place as the bolt exit the hole to get it threaded.
Click to expand...
Good idea!
 
There are a number of reasons the bolt is specified to be installed from the bottom.....

- Make it possible to get a torque wrench on the nut so that the fastener gets torqued properly. On an interference fit fastener such as this, it is undesirable to turn the bolt in the bore when torquing the nut(actually, that should be avoided for all fasteners when possible).
- There is not enough clearance between the engine mount socket and the firewall in many instances, for the nut and proper number of washers under the nut.
- If the bolt is installed with the desired interference fit it needs to be driven out if dis-assembly is needed. With the bolt installed upside down, it provides for a means to drive it out without removing the engine mount from the fuselage.

Those are the ones I can think of at the moment. I am sure there are more....
 
rvbuilder2002 said:
There are a number of reasons the bolt is specified to be installed from the bottom.....

- Make it possible to get a torque wrench on the nut so that the fastener gets torqued properly. On an interference fit fastener such as this, it is undesirable to turn the bolt in the bore when torquing the nut(actually, that should be avoided for all fasteners when possible).
- There is not enough clearance between the engine mount socket and the firewall in many instances, for the nut and proper number of washers under the nut.
- If the bolt is installed with the desired interference fit it needs to be driven out if dis-assembly is needed. With the bolt installed upside down, it provides for a means to drive it out without removing the engine mount from the fuselage.

Those are the ones I can think of at the moment. I am sure there are more....
Click to expand...

And:
- Vans said to do it that way.
:D
 
Tapered Pin

I went with a tapered pin on my nose gear leg and engine mount.

IMG_3246-M.jpg


Search the forums here for various threads and details on the installation.
 
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