fixing axle camber

[Drew Swenson]

I am about to fix my axle camber---it is about 10 degrees off. The builder installed incorrectly (my guess---he wanted the gear to be straight up and down but did not account that the weight would spread the gear.

 

It is enough of an adjustment to where I cannot use the same holes through the leg.

 

My thought was to slightly overdrill the original holes to make sure that any slimy gunk/dirt was removed. Fill with wet flox. Sand the original flox pad off. Remount and redrill---the holes would more or less go in the same spot--just at a slightly different angle.

 

Thoughts?

 

Also, I need to get both wheels off the ground at the same time to check the toe in while I am remounting the axles. I have electric nose gear---so I can put saw horses either under the spar or the bottom of the fuselage and let the nose do the work. Looking to see if anyone has a good picture of this evolution---don't want to crush anything.

[Marc Zeitlin]

My thought was to slightly overdrill the original holes to make sure that any slimy gunk/dirt was removed. Fill with wet flox. Sand the original flox pad off. Remount and redrill---the holes would more or less go in the same spot--just at a slightly different angle.

Should work fine.

I have electric nose gear---so I can put saw horses either under the spar or the bottom of the fuselage and let the nose do the work.

I built two tall sawhorses, put 4" thick blue foam on top of them, slip them under the end of the main spar/strake/wing, and then lift the nose. I can get both tires about 1" off the ground using this exact methodology. IIRC, it was John Slade who gave me this idea (giving credit where it's due).

[Drew Swenson]

Thanks much!

[Wayne Hicks]

Drew:

 

I have tall saw horses and I have these things. (See 3rd and 4th picture on that page.) They're essentially wooden jack stands without the jacks. As Marc says, with the plane parked on its nose I place the stands under the main spar. Deploying the nose gear raises the mains off the ground. The jack stands were easier to make than the saw horses. Just a sheet of 3/4-inch plywood. Email me if you need details.

[Drew Swenson]

Almost done with the fix. With the plane sort of mid loaded---the axle camber was 7 degrees in the wrong direction---and had toe out.

 

I measured all the angles with the plane mid loaded---then jacked it up to measure the deltas with the gear sprung back in to its natural position.

 

What i found is that the camber with the weight off was exactly zero on each side. Hmm---so that is what the original builder did. Once again---another builder trying to out-think the plans...

 

I needed to get 7 degrees of correction---and I have it another degree just in case. In case you are wondering, this is a BIG correction---shims won't work.

 

I got great advice via email from several builders---thank you. Most of the advice centered around how to measure---and reset to the desired values. This information was MOST helpful.

 

For actually resetting the position, here is what I did:

-Removed the old flox pad with a dremel.

-Overdrilled the existing axle bolt holes until I could move the axle enough to get the angles that I was looking for.

-Dry fit the axles with washers as shims to get me sort of close.

-Once I was satisfied, painted a coat of epoxy on the gearleg where I was going to mount the axle.

-Loaded up a big glob of flox

-Bolted the axle (with grey tape release) to the gear leg with the correct number of shims---then adjusted bolt pressure to get the angles that I was looking for. Camber was easy----toe in much harder since we are talking fractions of a degree.

-Once dry, removed the bolts. Bolts had to be twisted to break the bond---then pounded out. Not difficult---but I was hoping that the axles would remain attached---but did not.

-Redrilled the overdrilled holes--since they were partially filled with flox from the mounting

-Used a Q-tip to coat epoxy inside all the holes. Then filled the holes with flox---then let it dry.

-Cleaned up all the boogers. Mounted the the axles with clamps, then drilled the proper sized holes with a really long drill bit.

-Removed the axles and clamped on new backplates and drilled.

 

The plane is now sitting on the gear. The camber is between zero and 1 degree (in the good direction). I'll be checking on toe-in today. The toe-in is hard to get. If I am off a little, I may use the shims that Spruce sells (I think they are only in 1/4 deg incs though. But if I am off, that is all that I will be off. I am shooting between 0 and .5 toe-in. However, I want both to be the same---so if different, hopefully only a 1/4 deg will be needed.

 

While I was at it, the axles had a custom connection point for the wheel pants. Never liked it---it always broke. Bought new axle nuts that already have an offset for the wheelpant incorprated. I like it---but can't get it on enough to get the cotterpin holes to match. Will be looking at solutions this week---involve machining or grinding off some of the base (which would match the regular axle nut better)---or elongating the holes.

 

Also, the wheelpant fit differently since all the angles changed. Just have to move one bolt location (the one that attaches to the axle nut). Also had to carve up the wheel hole---looks good. Just keep in mind that the wheel massively sits differently in the wheel pant.

[Ron Springer]

I don't think that the camber problem is the fault of the builder. It is just a result of the plans methodology.

 

In the plans (and my direct experience is with a Cozy), the toe is precisely set but the camber just happens. The axle flange is bolted to the gear leg flush (in the vertical sense), so the gear leg angle becomes the camber angle. A flox pad is used to adjust the toe. Since the axle is usually mounted early in the build, the builder can't take into account any changes in camber due to loading. They only have an incomplete tub at that point and it is upside down on sawhorses.

 

But, this is a good thing to keep in mind, and when I am done I will go back and check the camber.

[Jason Heath]

While there is nothing in the plans that has you check it, you can at least make sure the angle is the same on each side. I used the boards and clamps method to set the flox pad with a laser (and string and sight tube and you name it) which also allowed me to draw a vertical line on the wall and adjusted the camber and toe at the same time. There was a slight difference between the two sides when I was checking everything which I could have made alot worse if I hadn't been looking for it and just added flox and dealt with the toe.

 

Read Cozy NL# 64 "Main Landing Gear Spread" for some history on the subject. The camber change has already been taken into account in the design of the strut assuming a builder doesn't assume for themselves where the camber should be set.

 

ps, there is "Owners Manual Addition" in NL# 65 regarding camber.

[Drew Swenson]

Ron---if the builder just set a flox pad and set the toe-in, then I would not be going back to correct anything. The camber was set in a way that actually brought the brake disks very close to the gear legs---top of the wheels pointed in by 7 degrees (sitting on the ground). The natural state with no weight should show top of the tires pointed out (some where around 10 degrees with the bottoms pointed in).

 

Just to put things in perspective---when you are setting toe in, you are only shooting for 0.25 degrees by plans. If you just set that, you will be fine. I am not off by a fraction of a degree in camber---I am off by 7 degrees. You don't get that way by accident---you had to work hard to get there. With the wheelpants off, it looked like I had retract gear that had started to retract. It was very clear when the plane was jacked, that the builder intentionally set the camber for zero degrees suspended---but did not understand the impact of spreading gear.

 

Looking at a Velocity builder site where the builder was setting the toe-in---evidently, they shoot for 10 degrees downward camber while suspended. I was shooting for 8 degrees (7 deg + 1 for slop). Thought it was pretty interesting that the two numbers came out about right.

 

Small divergence: My aircraft is a very pretty airplane---and the builder did a good job. The builder incorporated a lot of mods---most of which I don't care for---and some are great:

Goods that came with the aircraft

-electric nose gear

-rose ignition

-internal sumps

-Nice air vents in the wheelpants

-Nice removable nose access door that has tiny springs incorporated. When you undo the screws, the panel sort of pops out and is easy to remove.

-electric speedbrake

 

Goods that I have put in the aircraft.

-Bluemountain EFIS lite G4

-Dynon engine monitor

-Strong electric trim

-solid state turn coord

-Infinity stick

-laydown master cylinders

 

OK--but not for me

-no center arm rest and map pockets removed on the other armrests to give more butt room. Since there is no center armrest,the throttle and mixture are push pull cables on the inst panel. I would rather have the room for the flying stuff than for my butt. The wideness of the seat should not really be a problem for anyone. However, the wider canopy and canopy frame would have been a most welcome mod.

-No step incorporated to get in the plane.

-Unique headrest system that is incorporated in the canopy frame itself. While it is pretty nice, the lack of a normal "passenger headrest triangle" does not lend itself well to a gas strut. My prior Longez (and other Cozys for that matter) had a mod for a gas strut. With the canopy closed or open, the gas strut was completely unloaded---and with the canopy closed, it had a nice downforce to it. Because of the geometry, the gas strut is only unloaded while open----and is exerting strong force while the canopy is closed. Also because of the geometry, the canopy has a tendency to blow closed when the wind is blowing. So the headrest system really "opened up" the cockpit---but had other unintended consequences.

 

Others

-tank drains located underneath aircraft (attached to internal sumps). I would rather have the drains in the normal location since that is where water will show up. Now I have to stand the plane up and wait a little while for the water (if any) to seek the new low.

-hard brake lines with internal diameter too small which made braking extremely difficult. This was not necessarily a mod---but the builder ignored the correct line to use---or did not understand what inside diameter you were supposed to use.

-nose gear was attached to the upper joint with hardware screws (like from ace hardware) instead of the ones called out in the plans. This resulted in the nose gear shearing off during a backfired start with the gear partially retracted---this crushed part of the nose

-breather tube inside diameter was way too small. This resulted in the builder blowing a nose seal and losing all his oil----forced landing----and a rebuild on his brand new engine. He put the same size line back on and put in a blow valve in the line. I removed it all and put in the correct size line.

-Lot of plastic type clamps within the engine bay---I removed them all---many were brittle and fell apart.

-axles were mounted in a reverse camber and an outward toe (now corrected). While the gear legs were wrapped in fiberfrax and heat tape, there were no heat shields (corrected).

 

For the most part, I am not big on mods---unless you have thought thru on the second and third order effects. And--while I consider my aircraft a really good aircraft, I have had to undo a bunch of stuff---and live with others (or live with it until I do something about it---I put off the gear legs for about 3 years---the dangerous stuff, I took care of right away.

[Ron Springer]

Ron---if the builder just set a flox pad and set the toe-in, then I would not be going back to correct anything. The camber was set in a way that actually brought the brake disks very close to the gear legs---top of the wheels pointed in by 7 degrees (sitting on the ground). The natural state with no weight should show top of the tires pointed out (some where around 10 degrees with the bottoms pointed in).

OK, that explains it!