REFLECTOR:Nose gear leg gussets

Jim Agnew reflector@tvbf.org
Tue, 6 Jan 2004 19:23:58 -0800 (PST)


Scott,

You say that all FG struts since DMO #187 were heat
treated.  That is not true since I have DMO-348 and the
strut was not heat treated and I can prove it.  So either
the quality control was poor or your statement is not true.
 Either way having a strut after DMO #187 is no guarantee
that the strut was properly heat treated based on my
experience.

I will be posting pictures soon that show the failure mode
and a description of how the strut progressively failed.

Jim

--- Scott Baker <sbakr@comcast.net> wrote:
> Hello Tom, All ...
> Trying to remember the root questions that started this
> thread - I think we are all wondering about two issues
> regarding nose gear struts (legs):
> 1.    Heat treatment ... When did it begin and how do I
> know if I have a heat treated gear strut? And
> 2.    Reinforcement gussets ... "old style v. new style"
> ... What does it mean to me and does it apply to fixed
> gear models?
> 
> Let's talk about heat treating.  If you have a RG nose
> gear strut, it is heat treated (since day #1).  If you
> have a fixed gear that shipped before January 1993
> (beginning with DMO #187) you probably have a nose gear
> strut that is not heat treated.  Heat treating adds
> "spring-strength" to the gear leg.  It is treated to a
> Rockwell hardness # between 46 to 48, which allows some
> bending before the gear leg breaks.  Non-treated legs
> bend under stress; treated legs bend a little, then
> break.  It's impossible to determine if a gear leg has
> been heat treated based on looks.  If you're curious if
> the leg has been heat treated, the most simple way to
> check is to try filing or drilling the leg.  If the leg
> files or drills "easily" it is not heat treated.  If it's
> difficult to file or drill (believe me, you'll know),
> then it probably has been heat treated.  If you have a
> gear that has not been heat treated, you can have it done
> at a local shop or send it to Velocity (we send it to a
> shop in Orlando).  All XL models have been shipped with
> heat treated nose gear struts.  So ... the question of
> non-heat treated gear applies to Standard, Fixed Gear
> models shipped before January 1993 with serial numbers
> preceding DMO#187.  Everyone else is unaffected.
> 
> Moving on to gusset reinforcements.  All RG nose gear
> struts were designed with single web lower gussets
> supporting the strut to the nose gear pivot bolt tube. 
> Fixed gear models (until recently ... more on this later)
> were designed without gussets.  
> 
> Scott Swing often uses the phrase, "Aircraft are not
> designed to withstand flutter".  The same holds true for
> nose wheel shimmy.  If the aircraft experiences nose
> wheel shimmy, expect for the welds at the gussets to
> break.  I don't know why this is, but we have been
> receiving an increasing number of calls from folks who
> have gone through a nose wheel shimmy episode.  To help
> strengthen the nose gear pivot tube assembly we recently
> introduced a double walled gusset (we call this a "taco
> gusset" because the gusset looks like a folded taco
> shell).  We think the taco gusset will help the nose gear
> survive "mild" shimmy episodes - but it definitely does
> not guarantee that the welds will not break during a
> violent shimmy.  Shimmy often causes damage to the nose
> gear pivot bolt bushings as well.  The stronger the gear
> leg, the more likely damage will occur to the bushings
> (following a shimmy episode).  Again, the gear system is
> not designed to withstand a violent nose wheel shimmy. 
> Please become familiar with the proper tightening of the
> nylon nut that applies compression force to the spring
> washers in the shimmy dampener assembly - and make it a
> regular pre-flight inspection item.  I know it's a hassle
> to lift the nose of the aircraft into the air to check
> the "swivel force" of the nose wheel casting ... but it's
> better to do this than to experience a nose wheel shimmy.
> 
> Posing the question: "Is the taco gusset support stronger
> than the single web gusset?"  The answer is "Yes" (of
> course) ... but we do not recommend a retro fit for
> customers who have a single web gusset.  The single web
> performs as it should for all normal flight operations. 
> The double walled taco gusset does this too, but goes a
> step further to help the welds at the gusset location
> from breaking during a nose wheel shimmy.
> 
> Taco gussets and fixed nose gear legs - As I mentioned
> earlier, Velocity has not (until recently) included
> gusset reinforcements for fixed gear aircraft.  We still
> don't for fixed-gear Velocity SE models.  We are,
> however, now including a taco gusset reinforcement for
> XL-Fixed Gear models because we recon the XL's will be
> holding two "Bubba's" in the front seat and that it
> "wouldn't hurt" to add the gussets.  Quite frankly, our
> machinist was welding taco gussets to a batch of RG gear
> legs and decided, "What the heck.  While I'm at it I
> might as well add them to the fixed gear legs as well". 
> And so the tradition was established and continues.
> 
> I have seen some gear legs with (4) gussets welded to the
> strut - positioned above and below the pivot tube. 
> Customers are cautioned from modifying or welding
> additional gussets to the nose gear without having the
> gear heat treated afterwards.  Welding (as you know)
> changes the temper of the steel.
> 
> Hope this info helps to clarify things.
> Best regards,
> Scott Baker
>   ----- Original Message ----- 
>   From: Tom Martino 
>   To: reflector@tvbf.org 
>   Sent: Tuesday, January 06, 2004 1:22 PM
>   Subject: RE: REFLECTOR:Nose gear leg gussets
> 
> 
>   So, in essence, those of us with RGs do not have to be
> concerned with the style of nose gear ... is that
> correct?  Or are there some RG struts that need updating?


=====
James F. Agnew
Jim_Agnew_2@Yahoo.Com
Tampa, FL
Velocity 173 Elite Aircraft Completed & Flying