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  #11  
Old 08-20-2021, 09:33 AM
rvbuilder2002's Avatar
rvbuilder2002 rvbuilder2002 is offline
 
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Location: Hubbard Oregon
Posts: 9,660
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When comments first arose about different taxi steering response after replacing the nose gear on an RV-12, we invested the time to measure some nose gear legs and find a couple that were at the extreme of the allowable tolerance range for bend angle, and install them for testing on our RV-12iS.

We weren't able to detect a discernable difference in the steering quality with those legs compared to the original.
To assure no customer received a leg that was outside of the specified tolerance range we also implemented additional quality control checks.

The most common cause of poor steering performance (and likely the case for the O.P. for this thread) is improper lubrication and/or break out force adjustment.

As a side note, modifying an SLSA from the certified standard configuration is not allowed without manufacturer approval, and doing so technically makes the aircraft no longer airworthy (so suggesting adding a grease zerk to the nose fork on an SLSA RV-12 is not helpful.

It is our experience (literally many thousands of hrs operating and maintaining airplanes with free castoring nose wheels), that just pumping some grease into the nose fork is never a proper resolution for a stiff nose fork.
We recommend regularly disassembling them, cleaning, checking for rusting on the pivot shaft portion of the nose gear leg (common if it isn't being maintained regularly), then reassembling with all of the parts well lubricated with a water proof grease.
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Opinions, information and comments are my own unless stated otherwise. They do not necessarily represent the direction/opinions of my employer.

Scott McDaniels
Hubbard, Oregon
Van's Aircraft Engineering Prototype Shop Manager
FAA/DAR
RV-6A (aka "Junkyard Special ")
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  #12  
Old 08-20-2021, 09:50 AM
seagull seagull is offline
 
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Location: San Bernardino
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Quote:
Originally Posted by rvbuilder2002 View Post
When comments first arose about different taxi steering response after replacing the nose gear on an RV-12, we invested the time to measure some nose gear legs and find a couple that were at the extreme of the allowable tolerance range for bend angle, and install them for testing on our RV-12iS.

We weren't able to detect a discernable difference in the steering quality with those legs compared to the original.
I waited 3 months for Vans to test and finally decided my leg was out of spec. I am sure COVID was a factor in the delay. As I recall 1 degree on the bend was allowable but it wasn't clear if that was a total of 2 degrees since there are two bends.

Even if Vans determines it causes no problems with ground handling how is a person to level their nose wheel faring that previously was level on the original leg? My faring required a stack of washers .450" under the back screws to raise the tail of the fairing to level. I don't think a stack of washers is allowable on an S-LSA.
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Last edited by seagull : 08-20-2021 at 10:30 AM.
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  #13  
Old 08-20-2021, 11:01 AM
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Tony_T Tony_T is offline
 
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Location: Lacey, WA
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Having just replaced my nose leg I can report there is a difference of XX degrees fairing angle between the old and new. Unfortunately I did not make a measurement with my digital level of the old before doing the change so I have no real data.

The fairing mis-alignment to the airstream is noticeable:


And the gap between the leg fairing and the wheel fairing is greater than it was but again I don't have an actual measurement:


I have flown the airplane several times since the change and can report that there is no nose wheel shimmy or jerkiness. Have taxied it as safe a high speed I was comfortable with and it feels the same as the old nose leg did. We also did another 12 here and it taxies fine as well. Break out force on both ships set to 18 lbs.

Lately, I have been flying without the wheel pants. I'm doing short local flights less than 100 miles, lots of landings, small airports, and like being able to visually check the brakes, bearings and easily put air in the tires.

I agree with doing regular servicing of the the nose fork. Grit and water can work into the brass bushings and it needs to be disassembled cleaned and relubed with waterproof boat trailer grease, at least on annual CI. It is easy to do.
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  #14  
Old 08-20-2021, 11:08 AM
DHeal DHeal is offline
 
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I concur with Tony T's observation that there is a noticeable angular difference between my original nose wheel strut and the new strut. I too have had to add some washers to level the nose wheel pant.
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  #15  
Old 08-20-2021, 11:48 AM
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rvbuilder2002 rvbuilder2002 is offline
 
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Please note that I wasn't meaning to start a debate on whether the new version nose gear leg might have a slightly different bend angle....

Just stating that testing has been done and a different bend angle that is within the specified production tolerance wasn't found to cause any noticeable difference in ground handling / steering response.
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Opinions, information and comments are my own unless stated otherwise. They do not necessarily represent the direction/opinions of my employer.

Scott McDaniels
Hubbard, Oregon
Van's Aircraft Engineering Prototype Shop Manager
FAA/DAR
RV-6A (aka "Junkyard Special ")

Last edited by rvbuilder2002 : 08-20-2021 at 11:58 AM.
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  #16  
Old 08-20-2021, 11:56 AM
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rvbuilder2002 rvbuilder2002 is offline
 
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Quote:
Originally Posted by Tony_T View Post

And the gap between the leg fairing and the wheel fairing is greater than it was but again I don't have an actual measurement:

Tony, based on this photo, I would say that the angle of the wheel fairing hasn't changed at all.
If you look close at the gap to the nose leg fairing, it looks like it is constant.
That would indicate that the entire wheel fairing moved slightly lower relative to the nose gear leg.
If properly aligned, the angle of the wheel fairing should parallel the angle of the cockpit side rail when sitting on the ground. This will make the wheel fairing aligned with relative wind, between the nose and tail of the fairing in flight (I.E., the cockpit side rail is pretty close to level in cruise flight).
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Opinions, information and comments are my own unless stated otherwise. They do not necessarily represent the direction/opinions of my employer.

Scott McDaniels
Hubbard, Oregon
Van's Aircraft Engineering Prototype Shop Manager
FAA/DAR
RV-6A (aka "Junkyard Special ")
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  #17  
Old 08-20-2021, 11:57 AM
seagull seagull is offline
 
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Quote:
Originally Posted by rvbuilder2002 View Post
Just state that testing has been done and a different bend angle that is within the specified production tolerance wasn't found to cause any noticeable difference in ground handling / steering response.
Can you confirm what the production tolerance is. I thought I remember it being 1 degree but donít know if that is per bend = 2 degrees total or 1 degree overall.

The one I installed that had the shimmy was 3 1/2 degrees forward. The wheel pant was down in the rear about 1 1/2Ē.
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  #18  
Old 08-20-2021, 12:14 PM
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Piper J3 Piper J3 is offline
 
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RV-12 iS SLSA KBVS. Ooops... my bad. I didn't see you have S-LSA. I doubt your mechanical will add grease fitting. Modifications to S-SLA ares prohibited.
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Bought Flying RV-12 #120058 Oct 2015 with 48TT - Hobbs now 750

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  #19  
Old 08-23-2021, 09:26 AM
MVPILOT MVPILOT is offline
 
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Quote:
Originally Posted by JFCRV12 View Post
Sure sounds like breakout force isn't properly set. Have you or your mechanic checked the breakout force? Takes two minutes with nose lifted so worth a shot.
No the mechanic looked at it with the nose wheel elevated but asked me to learn what the breakout force is.
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  #20  
Old 08-23-2021, 09:30 AM
MVPILOT MVPILOT is offline
 
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Location: Mount Vernon, WA
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Quote:
Originally Posted by rvbuilder2002 View Post
When comments first arose about different taxi steering response after replacing the nose gear on an RV-12, we invested the time to measure some nose gear legs and find a couple that were at the extreme of the allowable tolerance range for bend angle, and install them for testing on our RV-12iS.

We weren't able to detect a discernable difference in the steering quality with those legs compared to the original.
To assure no customer received a leg that was outside of the specified tolerance range we also implemented additional quality control checks.

The most common cause of poor steering performance (and likely the case for the O.P. for this thread) is improper lubrication and/or break out force adjustment.

As a side note, modifying an SLSA from the certified standard configuration is not allowed without manufacturer approval, and doing so technically makes the aircraft no longer airworthy (so suggesting adding a grease zerk to the nose fork on an SLSA RV-12 is not helpful.

It is our experience (literally many thousands of hrs operating and maintaining airplanes with free castoring nose wheels), that just pumping some grease into the nose fork is never a proper resolution for a stiff nose fork.
We recommend regularly disassembling them, cleaning, checking for rusting on the pivot shaft portion of the nose gear leg (common if it isn't being maintained regularly), then reassembling with all of the parts well lubricated with a water proof grease.
Thank you for your sharing your experience. The mechanic asked me to learn what the proper break-out force is for my 2020 RV-12 S-LSA Where can I get this information?
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