Sonex 759 Update

[Corby202]

There is an article in the local magazine here that might be of interest
https://members.raa.asn.au/storage/58-june-2016-w.pdf

Took my first passenger up today, my 80kg mate Eddie. The plane flew ok with the extra weight, the climb rate was down obviously and the other thing of note was the fact I could not get enough down on the dial a trim during climb out so I might retension the springs. The other thing I have just done is to realign the wheels. I didn't like the constant shudder from the gear legs on landing. I thought I had them set good during construction using the method shown in the plans but this time I set them using a laser from the axles pointing back towards a marker board 60" from the axle, I couldn't believe how far out I had them. The RH was 3 deg toe in the LH was 1/2 deg toe out. Reset them to as close as I could to .7 deg. Flew the plane, shudder gone. Still shudders under braking but thats a different issue and its not that bad.

[LarryEWaiex121]

Phil,

I did something similar on Waiex 121YX. I built as close as I could using the plan instruction. Not good enough. Used up my right side tire in just over 80 hrs.
Took matters into my own hands and while I had the tires off the wheels; I used two long carpet layers straight edges(12 feet long), against the bare wheels. Extended the center line forward about the 12 foot and used the straight edges to put the .7 degree or whatever you say the plan called for.
I did this so long ago I've forgotten the exact number but it ended up being toed in about 1" each side, at the end of the 12' straight edge. In the end it was perfect. Now my tires go over 150 hrs. I do corner too hard and taxi too fast.
The tires are basically junk tires to begin with and they're being used well beyond their intended range I feel. I have to say though, I've never had a flat or slid one on the bead and ripped off a valve stem. I keep mine pumped to 50psi.

Larry
Waiex 121YX, Camit 3300
These planes are not optimized for long taxi runs. That's is probably the hardest thing on these tires. Especially if one is at full weight and the weather is hot hot.

[Corby202]

I was actually rolling the tread on the tires so I new there had to be something wrong. Strangely enough on the few occasions I have landed on grass everything has appeared fine.
One thing I remember from school is the 1 in 60 rule for degrees so that's why I had the marker board 60" away from the axle.

[peter anson]

Hey Phil, well done getting the article printed. It's great.

Regarding measuring toe-in, I have done that twice now but I was never very confident it was right. It must be OK because I have done 250+ hours and 470 landings and the tyres are only just due for replacement, but I think that was more good luck than good workmanship. How did you attach the laser to the axle? I have a small Bosch laser level that produces a fanned beam which I think would be suitable so long as the fan was vertical.
Any photos of your set-up?

Peter

[Corby202]

No pictures Peter, sorry. All I did was to attach a laser pointer to a spirit level and set that up on the bench first to get the dimensions (laser point distance away from the bench) and to make sure the laser pointed parallel to the bench. At the hanger with the fuselage supported by a frame I removed a tire from one wheel and used the wheel as the square to the axle, the spirit level I just held against the wheel and pointed it to the board I had set up. I thought the less then perfect wheel might have changed the geometry but rotating the wheel changed the laser point very little surprisingly. The annoying part was having to drill some new holes in one of the wheel pants to get it square again.

[jowens]

I'm close to drilling the gear legs and axles. When members are referring to resetting the toe are you using the play in the axle/gear leg bolting or replacing the axles? Some type of shim system?

[Corby202]

To move the axle say from +1 to -1 deg is a very small movement. I used shims inside an elongated hole. These axles are glued on also. If I had to move them more then a few thou I think I would weld tight fitting washers on the outside in the new position.