Landing Gear Axle Alignment Technique

[N111YX]

I found the methodology of the plans method of axle alignment difficult to do with precision. I thought that I had done a perfect job on my first attempt only to find that when I removed the jig, my alignment was off. The problem for me was the use of clamps that did not hold things well enough when drilling the titanium. The method described below provided an accurate alignment as my first set of tires lasted 350+ landings. The big difference with this technique is that the structure to be drilled is held much tighter than the clamping method with the added benefit of precise alignment.
The idea is to use the weight of the airplane to assist the axle alignment process rather than clamps. You will need a hydraulic jack or something similar that will allow the airplane weight to be partially applied.

First, drill the upper gear leg holes and install the legs and bolts.
Using six 2X4's about six feet long, nail or screw them together into a "U" configuration as "channels".
The channels will dimensionally accept the stock tires and is the key to make fine adjustments to the alignment as well as hold the assembly tight while drilling.
Level the fuselage (nose to tail) then slide the wheel/tire assembly on the axles and place both wood channels near the wheels, parallel to the fuselage, centered at the wheels (three feet in front of the wheels and three feet behind). Next, jack up the airplane, slide the channels under the tires. Lower the airplane so that both tires settle into the wood channels with enough weight to lock the axle movement snugly but without excessive weight as the rigging is supposed to take place without significant load on the gear.
You are now able to rotate the wood channels left and right to provide correct alignment with great accuracy using the arm of the channels.
Begin by setting straight wheel alignment with the fuselage centerline by using the tecnique described in a post below. Use a hammer to lightly tap the ends of the channels for small adjustments.
After final measuring and adjustments are complete, proceed to drill the axles. I found that using three of four drill sizes in succession is better than the one final size...

[Sonex1517]

Kip

Great tips - thanks! Do you have any photos? I am having trouble with the visualization of the 2 x 4's

Much appreciated post

[N111YX]

Robbie, sorry that I did not take pics. I amended the shape of the channels. Just picture a capital letter "U". I'll re-create the rigging with some pics later next week...

Kip

Great tips - thanks! Do you have any photos? I am having trouble with the visualization of the 2 x 4's

Much appreciated post

[Rick524]

I used your method Kip and added one more thing. I screwed 2 drywall T squares to the inside 2X4s, at the center, directly under the axles. The 4' side of the squares face inward. When the squares overlap perfectly, you have zero toe in. To get .7 deg toe in you simply pull the squares back to .354" back at the center, which for me was at the 30" mark.
Hope this makes sense.

Good luck with your projects!
Rick
Sonex 524

[N111YX]

That's great, Rick and a good idea, too. I hope it went well and I'm always happy to hear that this technique worked for someone else... :D

I used your method Kip and added one more thing. I screwed 2 drywall T squares to the inside 2X4s, at the center, directly under the axles. The 4' side of the squares face inward. When the squares overlap perfectly, you have zero toe in. To get .7 deg toe in you simply pull the squares back to .354" back at the center, which for me was at the 30" mark.
Hope this makes sense.

Good luck with your projects!
Rick
Sonex 524

[N111YX]

OK, here are some pics courtesy of Andy Walker. Andy and I spent about six hours drilling his tri-gear legs and we managed to streamline the process a bit.

You'll see the 2X4's used as "channels" to hold the wheels/axles securely in place for drilling. Note that the 2X4's don't necessarily need to be as long as six feet but such length does aid in making precicse measurements as the arm length is greater.

The first step is to set the wheel alignment perfectly straight (zero toe-in). We did this by plum-bobbing the centerline of the fuselage and drawing that line on the shop floor a distance that is at least three feet fore and aft of the axles. Next, we measured left and right from the centerline to both sides of the fuselage to within about six inches from the inboard face of the tires. These lines are then used, with a square, to align the sides of the tires with the centerline of the fuselage.

The toe in was set as described above, by simply tapping the front of a "channel" inwards the appropriate amount. For reference the 0.7 degree toe-in is the equivalent of moving the outer surface of the tire inwards a distance of about 1/16th of an inch. Rick found this distance to be .354 inches at a 30 inch arm and if you are good at math, you can use whatever arm distance you like. However, using 1/16 inch at the tire is probably well enough.

[N111YX]

Pics II

[Andy Walker]

Thanks for all your help, Kip!

I highly recommend Kip's technique if you have not toed in your gear yet. It seems much more accurate and less prone to error than the method in the plans. I still have to updrill the holes (we ran out of time to finish that up), but the pilot holes are drilled so that the geometry is set, and it looks great.

Also, Tricycle gear seems a lot more complicated than the conventional gear setup. The mounts are a hassle and the brake cables have to go through the spar carry-through, creating a lot of added complexity. If I had to do it over, or I end up doing another one (Onex?), I'd just do a tail dragger and learn to fly it.

[Mike53]

Thanks for all your help, Kip!

I highly recommend Kip's technique if you have not toed in your gear yet. It seems much more accurate and less prone to error than the method in the plans. I still have to updrill the holes (we ran out of time to finish that up), but the pilot holes are drilled so that the geometry is set, and it looks great.

Also, Tricycle gear seems a lot more complicated than the conventional gear setup. The mounts are a hassle and the brake cables have to go through the spar carry-through, creating a lot of added complexity. If I had to do it over, or I end up doing another one (Onex?), I'd just do a tail dragger and learn to fly it.

Andy the Onex landing gear is a flat gear ala "Cessna 150" and is simplicity as only Steve Whiteman could have come up with,so don't throw out the idea of the getting a nose dragger should you ever decide to build the Onex.

[Andy Walker]

Thanks for all your help, Kip!

I highly recommend Kip's technique if you have not toed in your gear yet. It seems much more accurate and less prone to error than the method in the plans. I still have to updrill the holes (we ran out of time to finish that up), but the pilot holes are drilled so that the geometry is set, and it looks great.

Also, Tricycle gear seems a lot more complicated than the conventional gear setup. The mounts are a hassle and the brake cables have to go through the spar carry-through, creating a lot of added complexity. If I had to do it over, or I end up doing another one (Onex?), I'd just do a tail dragger and learn to fly it.

Andy the Onex landing gear is a flat gear ala "Cessna 150" and is simplicity as only Steve Whiteman could have come up with,so don't throw out the idea of the getting a nose dragger should you ever decide to build the Onex.

I noticed that Sonex seems to have realized the expense and difficulty of dealing with titanium is not worth the weight savings and "cool" factor over using simple steel gear when they designed the Onex. I was actually already thinking my next build would be a tail dragger, so the Sonex gear hassles are just titanium frosting on that cake. ;)