7A Nosegear Leg Stiffener?

hevansrv7a · #1 01-26-2009, 04:46 PM

I'm doing the Service Bulletin on my 7A's nose gear. I know this subject has been discussed at length, but I don't recall this question being addressed specifically..

Even with the new fork, it seems to me that with the same, small wheel, it would be easy to hit a hole or ridge such that the leg would begin to flex and the front of the fork would rotate downwards. If the top of the hole or ridge were below the line of the axle but still pretty high, it seems to me that one's chances of rolling up and out of it would be improved if the leg were to flex less, especially, perhaps, at the bend. So my question is whether it is reasonable to stiffen the leg by glassing on some wood such as spruce. Are there unforeseen bad consequences?

I've also been thinking about a skid as described in earlier posts, either metal or a lump of matrix, but this is a different issue, I think.

Opinions, expert and otherwise, gladly received. Thanks.

newtech · #2 01-26-2009, 05:14 PM

I have already cut the spruce stiffeners that will be glassed to my nose gear leg. Have the new fork and a Grove nose wheel. IMHO this puts me in the best possible scenario for a well behaved airplane. The second half of the equation is the pilot flying the plane to keep as much weight off the nose gear as possible. I will have to work on the second part :-)

Finley Atherton · #3 01-26-2009, 05:53 PM

I will put myself in the "otherwise" rather than expert category. I have not looked back at the photos in previous threads that show damaged, bent gear struts, but from memory, I think there is usually considerable deformation at the bend at the lower end of the strut. It would be very difficult to brace this area with a wood stiffener so I suppose that it would be the rest of the strut and not the bend area that would be typically braced. My concern is that the wood brace would therefore stiffen the leg above the bend and thus concentrate the impact forces at the bend. Might it be better to not install the brace so the forces are more evenly spread over the entire length of the strut??
You might want to consider cutting away, raising and reshaping the bottom of the nose cone in the area below the big nut to take advantage of the increased 1" clearance offered by the new fork. I have done this and have also reinforced this area so it should act as a skid. I have operated out of some rough grass airstrips and have been quite surprised that I have not even had a scratch on the lower nose cone area.

Fin
9A

Little_Richard · #4 01-26-2009, 06:48 PM

The wood does not really do much stiffening of the gear leg. If you compare the tensile strength of the wood (No matter what kind) to the tensile strength of the heat treated steel, you will see that the wood is FAR weaker than the steel.

However the wood is not entirely useless in some people's opinion. It does act as a dampener of sorts as it has a different resonant frequency than the steel and this is probably where the benefits come from.

As far as the gear legs that have bent, after seeing a couple, they definitely DO NOT bend right above the axle where there is already a bend from the factory, but rather they tend to create a big U shape about halfway down the gear leg.