MLG Width Adjustment

After a few days of work at my regular job, I was glad to get back to Bearhawk preparations. I installed batteries in the ELT and armed it. I set up to make the adjustments to the landing gear width as instructed by Bob. First, I tied a rope around the bottom of one axle, so that it would not be able to slide up the axle. Then, I connected a heavy-duty ratchet strap to the other side. Bob suggested a come-along, but I didn’t have one handy, and the ratchet strap is larger than usual, with 2″ webbing. I connected the strap to the rope and applied tension until the shock struts seemed to be neutral. I had to roll the plane back and forth a few inches to let the gear slide in. Once the tension was off of the shock struts, I could remove the lower bolts, then remove the bottom end of the strut. Then I could rotate the whole strut to change the thread engagement of the bearing at the top. I spent a while trying to figure a few things out, and I had to call Bob for a little bit more clarification, but eventually I was able to get the gear set up correctly. Here are a few tips. First, I used a second ratchet strap between the gear leg and the rope. This allowed me to set the second strap so that it was a few inches longer than the first. When I needed to let a little bit of tension out, I would release the first strap and let the second take up the load. Next, let me elaborate a little on how the gear is supposed to be configured. If the gear is built to plans, then the axles will be coliniar when the tread width is 72″ at the center of the axle. Since the tires are not perpendicular to the ground, I was measuring the tread width from the center of one tire to the center of the other, with my measurements happening in the vertical center of the tire, in the front of the tire. I found that I had to have the rod end threaded pretty far out to get the width wide enough. Bob says that the minimum thread engagement should be 1/2″ to 5/8″, with his preference being 5/8″. He said if the threads were really tight, then 1/2″ would probably be ok. He pointed out that since the thread pitch on the bearings is 20 threads per inch, then one could be sure about the engagement by threading the bearing all the way out and counting the turns. The overall thread length of the bearing is 1.5″. Bob suggest 68″ from center to center with no load on the shock struts, and requires no more than 74″ width at max gross weight. There are several things that occur to me here. One is that I’m not positive that the center of the tire is coincident with the center of the axle. The other is that until I load the airplane up to max gross weight, I won’t have any way to verify that I haven’t exceeded the 74″ limit. When I get to that stage, I’ll be sure to measure again. When the gear is splayed beyond the 72″ neutral point, then the gear is toed out. When it is narrower than 72″, it is toed in slightly. This caused a minor short term panic, because after I finished the adjustment I rolled the airplane forward and backward to check for changes in the width. I found that at the empty condition, the wheels were toed in a little. I was under the impression that any toe-in was bad, and had flashbacks of the complicated job of aligning the gear all over again. Fortunately, it turns out that because my tread was so narrow in the empty condition, the gear is supposed to be toed in a little. Bob says that this is the way he likes it, and that upon rolling backwards, the gear width shouldn’t change by much more than an inch or inch and a half. After setting all of that up, I added cotter pins to the bottom of the shock struts. I made the new aileron cables out of the new stuff that came in, but I left the dead ends long until I finish the rigging completely. I don’t want to wait yet another week for replacement cable!