Play in nose gear assembly

[bjdecker]

For the hive mind --

I'm helping a friend with his RV-14A and see two issues with the nose gear.

1. With aircraft on jacks, the nose wheel/gear has at least an inch of "free play." (fore/aft) -- the amount of movement between neutral/unloaded and starting to compress the elastomer donuts. The SB-00027 appears to have been complied with as there is a large washer between the MS21045-6 nut and U-01420 spring cap, instead of the xxx0632 (nee AN960-06L)
2. There is 1/16" or so of slop in the bushings & bolts in the U-01407, U-01406, and U-01416 pieces and their attachments to the motor mount.

SInce the excess movement is up/down, I don't think cranking down on the bolts/castle nuts is going to solve the issue. It almost seems like the bushings are undersized.

How much wiggle is acceptable here?

Thank you in advance!

 

[rvbuilder2002]

For the hive mind --

I'm helping a friend with his RV-14A and see two issues with the nose gear.

1. With aircraft on jacks, the nose wheel/gear has at least an inch of "free play." (fore/aft) -- the amount of movement between neutral/unloaded and starting to compress the elastomer donuts. The SB-00027 appears to have been complied with as there is a large washer between the MS21045-6 nut and U-01420 spring cap, instead of the xxx0632 (nee AN960-06L)
2. There is 1/16" or so of slop in the bushings & bolts in the U-01407, U-01406, and U-01416 pieces and their attachments to the motor mount.

SInce the excess movement is up/down, I don't think cranking down on the bolts/castle nuts is going to solve the issue. It almost seems like the bushings are undersized.

How much wiggle is acceptable here?

Thank you in advance!

Is this on a new not yet flown airplane or one that has some hours on it?
It is described in the manual somewhere that the elastomers compress after a while and installation of a spacer washer can be required to remove all the play when fully tightening the nut to wear it bottoms out on the threads is not doing so.
To put it another way, the elastomers or donuts as you call them are supposed to always be under at least a slight amount of compression, even with no weight on the nose gear leg
The play that you have described is probably from that. The small amount of play at the pivot points of the leg is not a concern for that amount.

 

[Draker]

For the hive mind --

I'm helping a friend with his RV-14A and see two issues with the nose gear.

1. With aircraft on jacks, the nose wheel/gear has at least an inch of "free play." (fore/aft) -- the amount of movement between neutral/unloaded and starting to compress the elastomer donuts. The SB-00027 appears to have been complied with as there is a large washer between the MS21045-6 nut and U-01420 spring cap, instead of the xxx0632 (nee AN960-06L)
2. There is 1/16" or so of slop in the bushings & bolts in the U-01407, U-01406, and U-01416 pieces and their attachments to the motor mount.

SInce the excess movement is up/down, I don't think cranking down on the bolts/castle nuts is going to solve the issue. It almost seems like the bushings are undersized.

How much wiggle is acceptable here?

Thank you in advance!

Mine is a -7A, but with the elastomer nosegear, and I also had "free play" in the gear. See my build's thread starting with this post. Long story short, I did not tighten the MS21045-6 nut to the point where the spring was fully compressed, leading to extreme free play (the gear hung down noticeably while in flight).

EDIT: You're actually in that thread, so you might remember it

From your post it looks like you did crank down the castle nut all the way, so maybe this isn't your problem. Something to double check though.

 

[bjdecker]

Is this on a new not yet flown airplane or one that has some hours on it?
It is described in the manual somewhere that the elastomers compress after a while and installation of a spacer washer can be required to remove all the play when fully tightening the nut to wear it bottoms out on the threads is not doing so.
To put it another way, the elastomers or donuts as you call them are supposed to always be under at least a slight amount of compression, even with no weight on the nose gear leg
The play that you have described is probably from that. The small amount of play at the pivot points of the leg is not a concern for that amount.

Mine is a -7A, but with the elastomer nosegear, and I also had "free play" in the gear. See my build's thread starting with this post. Long story short, I did not tighten the MS21045-6 nut to the point where the spring was fully compressed, leading to extreme free play (the gear hung down noticeably while in flight).

From your post it looks like you did crank down the castle nut all the way, so maybe this isn't your problem. Something to double check though.

Ryan - Yes, I saw that in your first flight video and commented on it, along with CarlN (RV8JD). This is one of the issues that I can see with the gear assembly -- but --

I have the MS21045-6 nut bottomed out on the thread and there's still quite a bit (sorry didn't measure) of movement fore/aft before the elastomers compress. I've also now added two AN960-06 washers under the nut in addition to the fender washer and the U-01420 cap (this is about .226" between the bottom of the nut and the top of the U-01420, which is a pretty gross deviation from the stackup in the plans.)

The other issue is the aforementioned movement of the parts with the internal steel bushings in relation to the motor mount brackets.

Scott - Aircraft has about 70 hours on it.

 

[rvbuilder2002]

Ryan - Yes, I saw that in your first flight video and commented on it, along with CarlN (RV8JD). This is one of the issues that I can see with the gear assembly -- but --

I have the MS21045-6 nut bottomed out on the thread and there's still quite a bit (sorry didn't measure) of movement fore/aft before the elastomers compress. I've also now added two AN960-06 washers under the nut in addition to the fender washer and the U-01420 cap (this is about .226" between the bottom of the nut and the top of the U-01420, which is a pretty gross deviation from the stackup in the plans.)

The other issue is the aforementioned movement of the parts with the internal steel bushings in relation to the motor mount brackets.

Scott - Aircraft has about 70 hours on it.

Look in the nose gear leg installation section of the build manual
I am pretty sure that it mentions that in the future washers should be added to remove the static play from the strut for the nose gear leg.
The washer added, for the service bulletin was for a totally different purpose and just because it’s there it should not be considered to be sufficient. You add whatever washers are required to remove all the play.

 

[bjdecker]

Look in the nose gear leg installation section of the build manual
I am pretty sure that it mentions that in the future washers should be added to remove the static play from the strut for the nose gear leg.
The washer added, for the service bulletin was for a totally different purpose and just because it’s there it should not be considered to be sufficient. You add whatever washers are required to remove all the play.

<sigh> Been living and breathing the plans....

Section 40A-06, Step 6 and notes.

Yes, the plans say to add a second isolator washer on top of the first ("trimming is not required") -- this statement seems incorrect -- a "washer" will not fit under the spring and on top of the existing U-1002 without trimming.

Is the U-1002 the right "washer" to add under the spring or does simply adding a bunch of AN960's between the nut and spring keeper cap sufficient?

 

[rvbuilder2002]

<sigh> Been living and breathing the plans....

Section 40A-06, Step 6 and notes.

Yes, the plans say to add a second isolator washer on top of the first ("trimming is not required") -- this statement seems incorrect -- a "washer" will not fit under the spring and on top of the existing U-1002 without trimming.

Is the U-1002 the right "washer" to add under the spring or does simply adding a bunch of AN960's between the nut and spring keeper cap sufficient?

AN960’s under the nut to add sufficient thickness, so that a slight compression occurs in the elastomers and spring just before the nut bottoms out on the threads.

 

[RV10ING]

FYI, on the RV-10, there were oversize bushings available for the connection at the engine mount if it becomes excessive play. You can measure ID and have a machine shop turn bushings down to your specifications.
-Chris

 

[Bavafa]

<sigh> Been living and breathing the plans....

Section 40A-06, Step 6 and notes.

Yes, the plans say to add a second isolator washer on top of the first ("trimming is not required") -- this statement seems incorrect -- a "washer" will not fit under the spring and on top of the existing U-1002 without trimming.

Is the U-1002 the right "washer" to add under the spring or does simply adding a bunch of AN960's between the nut and spring keeper cap sufficient?

Yes that is the correct washer and up to two additional washers are acceptable (total of three) before we need to replace the elastomers.