REFLECTOR: main gear pivot bolts
John Dibble
aminetech at bluefrog.com
Fri Feb 9 14:21:21 CST 2007
I'd like a picture of the plate.
I'm having trouble deciding on grade 5 or grade 8 bolt. So maybe the
grade 5 bolt is better so the bushing doesn't get torn out? Or, maybe
the standard gear leg w/o carbon allows enough give so a grade 8 is ok?
It would be nice to have some type of shock absorbing device, but I
suppose that would be too complicated.
John
davedent at comcast.net wrote:
of the 5/8" bolts on my right gear of my XL/RG. The first one was a grade five and the last two wear grade eights. They all got bent. So I have spent a lot of time trying to find out why.
Finally I found out that the moment on the pivot point was way to long. So I built and added a plate to the fwd main gear bulkhead. Much like the one on the nose gear pivot but a 3X4" plate with inbeded bushings. This plate is sandwiched on the bulkhead with four #10 bolts and flox to even off the surfaces. If anyone wants pictures, send me you address and I'll send it. I can't put them in these emails. I tried the picture of the new Vesta prop and it wouldn't go through. By the way the prop weighs in at 67lb with spinner.
I also made new captivators out of eight plys of carbon and added a web to the fwd side of the captivator to beef up the fwd torsional loading that is applied on each landing.
I found out that I had a tire that had got out of balance and caused the gear to vibrate so much that it bent the bolt and wiped out the fwd main gear bulkhead bushing. Actually tore the bushing out of the bulkhead. It's just floxed in remember. This is the gear I completely covered with all cabon instead of the uni E-glass. It ended up way to stiff. So doing transferred all the loads to the bolt and pivot points. Lesson learned here as well.
The next one got taken out because the brake line to that gear had a slight kink in it, because of being removed and not noticing it. This caused the brake not to release fast enough causing the gear to take a beating again. So doing bending the bolt again. On just one landing it took out the brake pads and the bolt. So make sure the brake lines, NylaFlow type, are in so that no kinks can happen. Something simple like that can get you, BAD.
Related to the bending of the bolts, if you haven't checked lately, I would do a rotational check on your bolts. If you can't rotate them by taking a 15/16th wrench and rotating it at the head of it, it is bent. If it is bent just a little and I mean just a little it can cause the whole alignment to be off. So doing can prevent proper travel and failure to have it come up in the well right and hang up in the well. Believe me, it don't take much. I have seen some wells that if you just change a tire, it wouldn't fit up in the well. Now add this miss alignment to it and you can see what can happen.
One one occasion on the way home from OSH, last summer, it got bent just enough so the gear linkage went up about one inch higher, it don't take much remember. During the next retract it caught on the overhead vent drain line and prevented the gear from going all the way into the lock position. The drain line actually caught in the notch in the overcenter link. This allowed the gear to become unlocked and pulled the one gear back up into the well, so doing the plane came to a stop with two legs down and one leg up. A real bad day.
This bent bolt was caused by a hard landing the flight before this onto an major down hill short runway by my partner. No fault of his, just not prepared for such a runway. The bolt should have been able to take it. This was the grade five bolt also. I'm sure if it had been the grade eight it would torn out the fwd bulkhead bushing as well. It is only floxed in as you know and with that long moment arm you can see what it could do. That's why I did the extra beefing up in that area. By adding the plates and shear web on the captivator.
I know I have gone on a long time on this subject but I think you all should know what I have found and did. Learn from others, and don't think it won't happen to you. IT WILL>
By the way I buy my grade eight bolts from Fastinal. They are all cirtified and will give you papers if you ask for it a head of time.
Dave
-------------- Original message ----------------------
From: Scott Derrick <scott at tnstaafl.net>
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> Subject: Re: REFLECTOR: main gear pivot bolts
> Date: Fri, 9 Feb 2007 13:13:44 +0000
> From: Scott Derrick <scott at tnstaafl.net>
> To: Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
>
> mines a STD.
>
> Joe Ramsey wrote:
>
>> Main bolts on the XL-5's are 5/8" * 10".
>> On 2/8/07, Scott Derrick <scott at tnstaafl.net> wrote:
>>
>> No, I think the old ones were 3/8 and the new ones 1/2
>> inch..
>>
>> Scott
>>
>> Mike Dawson wrote:
>>
>> > I thought Velocity went to 5/8 bolts and the old ones
>> > were 1/2 inch?
>> >
>> > Mike
>> > --- Scott Baker <sbakr at comcast.net>
>> > wrote:
>> >
>> >
>> >> Most of the Grade-8 bolts that Velocity receives
>> >> from suppliers are not
>> >> perfectly straight. I've noticed a bend in the
>> >> bolts with enough sweep to
>> >> cause friction inside the steel main gear leg insert
>> >>
>> >> bushing. The friction
>> >> is such that a very light tapping with a hammer
>> >> easily pushes it through the
>> >> bushing. This may or may not speak to what you
>> >> describe.
>> >> I have notice that most of the main gear bolts seen
>> >>
>> >> in the Velocity Service
>> >> Center require a hammer and punch to remove. This
>> >> leads me to believe that
>> >> small bends in the main gear bolts are common place.
>> >> SB
>> >>
>> >>
>> >> ----- Original Message -----
>> >> From: "Scott Derrick"
>> >> <scott at tnstaafl.net>
>> >> To: "Velocity Aircraft Owners and Builders list"
>> >> <reflector at tvbf.org>
>> >> Sent: Thursday, February 08, 2007 10:44 AM
>> >> Subject: REFLECTOR: main gear pivot bolts
>> >>
>> >>
>> >>
>> >> > I pulled my main gear off yesterday and was
>> >> >
>> >> disappointed that the 1/2"
>> >>
>> >> > pivot bolts were slightly bent. I only have a
>> >> >
>> >> couple hundred hours on
>> >>
>> >> > this set of bolts and I don't think I'm that bad
>> >> >
>> >> of a pilot when it
>> >>
>> >> > comes to landing the thing. Maybe its all a
>> >> >
>> >> matter of perspective
>> >>
>> >> > though. :-)
>> >> >
>> >> > The bolts weren't bent a whole lot, and came out
>> >> >
>> >> with light persuasion
>> >>
>> >> > from a rubber mallet, but they are bent enough
>> >> >
>> >> that I don't want to
>> >>
>> >> > re-use them. The gear also retracted fine prior to
>> >> >
>> >> removal which is my
>> >>
>> >> > usual test to verify all is well as the clearance
>> >> >
>> >> is fairly close for
>> >>
>> >> > the legs and wheels up in the wings. A leg with a
>> >> >
>> >> really bent bolt won't
>> >>
>> >> > retract or will bind somewhere, ask me how I know!
>> >> >
>> >> > I realize a redesign of this part of the system
>> >> >
>> >> would be a lot of work,
>> >>
>> >> > but every A&P that I have shown this pivot bolt
>> >> >
>> >> system too has not liked
>> >>
>> >> > it. Its a lot of bending forces on a long bolt
>> >> >
>> >> that is not supported in
>> >>
>> >> > the middle very well. Maybe the fix is to use a
>> >> >
>> >> thicker sleeve in the
>> >>
>> >> > leg to provide more support in the middle which is
>> >> >
>> >> where the bolt always
>> >>
>> >> > bends? Or possibly a better(stiffer) alloy steel
>> >> >
>> >> for the sleeve?
>> >>
>> >> > Anybody else with hundreds of hours on there V
>> >> >
>> >> that has had to R&R the
>> >>
>> >> > main gear experience what I am? Bolts always
>> >> >
>> >> just a little bent?
>> >>
>> >> > Scott
>> >> >
>> >> > --
>> >> >
>> >> > -
>> >> >
>> >> > I worry about my child and the Internet all the
>> >> >
>> >> time, even though she's
>> >>
>> >> > too young to have logged on yet. Here's what I
>> >> >
>> >> worry about. I worry that
>> >>
>> >> > 10 or 15 years from now, she will come to me and
>> >> >
>> >> say 'Daddy, where were
>> >>
>> >> > you when they took freedom of the press away from
>> >> >
>> >> the Internet?'
>> >>
>> >> > Mike Godwin, Electronic Frontier Foundation
>> >> >
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>> --
>>
>> -
>> Those willing to give up a little liberty for a little security
>> deserve neither security nor liberty.
>>
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