Thorp Air Command - T18.net

Took my gear off again yesterday to make the repair. Got it back this afternoon. tHe patches aren't quite placed the way James Ball did it, but close enough.

Another picture.

Wait and see,but my guess it will still crack at the crotch

I'm more optimistic, Bill.

The way I see it is that the original weld design could have been better. The cracks initiate at the inboard end of the weld bead... a spot where the bead is spanning a relatively large gap between the round gear leg and the thin flat reinforcing plate. As has already been discussed, the bead is also across the line of stress. One a crack initiates, it will propagate easily.

This patch design does three things:
1 It rounds out the inside corner, which is much more resistant to fatigue.
2 It adds a lot of material section to the problem area, which lowers stress, which is also better for fatigue.
3 It turns the transverse weld into a longitudinal weld, which is a better way to weld something under stress.

Personally, I think if the reinforcement plate design had originally incorporated a shape like this, we wouldn't see gear cracks in the fleet.

Time will tell.

D

Dick,
You need to make sure that surface is flat enough to handle the accompanying hardware. Side loaded bolts in that area would not be a good idea.
Cubes

Not a factor, Jim.

I understand the doubler plate on the front, this area is under tension when landing etc.
I don't understand the need for the plate on the back, this area is under compression and does not have a history of cracking?

_________________
Scott Emery
EAA Chapter 326
T-18 N18TE

Yeah, I thought the same thing, but trust me, they crack on the back too. It'd just a poor weld design.

In theory, theory and practice are the same, but in practice they're not.

DW