Can you make them with depleted uranium instead? I might be able to solve my rear C of G problem at the same time!
Sadly, I doubt I'll be able install a fin on my bird; I don't think our regulator will take kindly to such a modification.
Moderators: Rick, Lance Murray
Can you make them with depleted uranium instead? I might be able to solve my rear C of G problem at the same time!
Bingo! I think you are right on Rich. Excellent analysis and proof of concept photos.Rich wrote: ↑Tue Jun 11, 2019 7:19 pm For the longest time I've been looking for the cause of the nosewheel not being stable in a position more aligned with the axis of the plane and I think I've found the main culprit - namely the fact that the lower end of the nosewheel pivot axis angles rearward. By my measurement, with the plane sitting on the gear, it's about 5 degrees. When the weight is off the gear after takeoff, the arm pivots downward and this angle actually increases.
Here is the side view of the nosewheel:
Nosewheel.jpg
Since almost all the weight (certainly the CG) of the nosewheel arm, wheel, and even the fairing is above the rotation of the axis, the structure is unstable. I simulated this with a hinge and vice-grips set at a 5-degree angle from vertical. Here it is sitting in a line:
Sim1.jpg
Looks OK, right? But disturb it even a little bit and the whole shebang flops around until something stops it. It can go to either side, depending on the disturbance. And remember it's actually also moving downward, due to the angle. Here's where it went of it's own accord:
Sim2.jpg
Depending on how the preload (i.e. friction) has been set, it takes more or less force to get it moving, but from there it keeps going until it either hits the stop on that side or there's enough relative airflow force to arrest it. Once it sets up, any correcting airflow force has to produce enough lateral force to actually lift the assembly, rotating it back in place and overcome the preload. Clearly the stock fairing isn't up to this.
No good deed goes unpunished, eh? I would guess uncertainties lie mostly with the "speed gear" and possibly the NG (there is an OSB for nose fairing replacement in conjunction with different versions of the nose gear).
Haha. For sure. Just excited and hopeful. Bret sent me a fin for a trial run on my 2004 and it was quite a bit different in curvature of the fairing and mounting screw placement. I would have offered up my fairing for drafting but I have a partner in the plane and we fly a lot and didn’t want to go without it for several long cross countries. So I’ve been hoping he found an available one located close to him. But I will say what he has so far is a solid design and looks sharp.