Bob Kuykendall
Well Known Member
Here's the thread where Steve Smith and I showed that it pays to use good hardware on the landing gear clamps.
624832 said:I had originally bought the Grove 2 piece airfoil gear but after spending a lot of time discussing the gear with Robby Grove I decided to return them and get the 1 piece gear. Robby and I spent a number of hours discussing the various issues and I really couldn't come up with any downsides to the 1 piece gear and there seems to be a lot of advantages.
My biggest concern is what happens when you side load the gear. As a low time pilot, I feel I am likely to do this and I wanted minimise any impact that might have.
In looking at the geometry of the standard gear, in a normal landing, the outside of the gear tower takes a compression load and the inside of the gear tower takes a tension load. The gear tower is designed to take these loads easily.
If you side load the gear, however, the outside of the gear tower takes tension load, which it can handle well and the inside of the gear tower takes a compression load. Imagine and old style beer can opener levering the inside of the gear tower with the outer mount point as the fulcrum. There have been a couple of instances where this has caused the inside of the gear tower to crumple.
Now look at the 1 piece gear. In a normal landing the outside of the gear towers still take the compression load and the centre of the gear flexes to absorb some of the impact. The inside of the gear towers are no longer involved. If you side load the gear, the outside gear tower of the loaded side gets tension load and the outside of the opposite gear tower gets compression load. Not a problem.
I believe that the best way to mount the gear is with the outside clamp bracket only as this allows the gear to flex in the middle as it is designed to. This takes the gear tower out of the picture. In fact you could probably remove much of the gear tower assembly if desired. I didn't as I had already built them when I decided on the 1 piece gear.
The only possible downside of the 1 piece gear which we could identify was that if you side load the gear to a great extent, especially if you were on 1 wheel at a high horizontal angle, that the upward force on the opposite side of the aircraft could cause the aircraft to roll since the upward force is applied on the far side of the fuselage rather than a few inches inboard as it would be with the standard gear. I doubt if this is likely though.
In addition to a number of discussions with Robby Grove, I also cornered Ken Krueger in the Van's booth at Oshkosh a few years ago. I asked his opinion of the 1 piece gear and we spent a few minutes drawing out the geometry and looking at the issues. Ken would not, of course, endorse the idea, but he also could not come up with any negative issues either which I took a a good sign.
One of the best aspects of the 1 piece gear is that it is very easy to align. I shot a laser line down the centre of the fuselage onto a wall about 20 feet away from the gear. I also mounted a laser on one of the axle mounting holes on each leg and aimed the at the wall as well. Then I only had to adjust the gear so that the distance from the centre laser dot to each of the others was the same.
For my brake lines, I had Robby put the fitting on the top of the gear in such a location that it comes up through a hole in the floor in the middle of the gear tower. My flexible brake line runs into the tower and screws right down onto the AN fitting. Very clean with no bending of tubing.
BTW Dans Maths is totally wrong. The stress increase (if any) is absolutely nothing like he incorrectly asserts!
...no knowledge of the Width and the Tapering, the Thickness at the Mid-Point, Radius of Bend (and therein the distortion angle) or the Flare of the Pneumatic Type Coupling or the Size of the Pneumatic Wheel
....fails to understand the Elasticity Mechanics of Material and Design and Kinetic Energy Disruption.....