Split Axles on Fly Babies

The question occasionally arises regarding the straight-across axle the Fly Baby uses on its landing gear.  People worry about whether the axle will "catch" on tall grass if they have to force-land, and the subject of split axles (as shown on page 2-14 of the plans) occasionally comes up in the discussion group.

Pete's opinion is pretty clear, in the plans:

"The designer is against the divided axle and includes it in these drawings only to show that it CAN be done." [Page 2-14].

"Those who worry about clearing obstacles on the ground seem to forget that anything high enough to snag the axle would also be a mighty unhealthy thing to hit with a wheel at takeoff or landing speed.  Grass high and dense enough to be a problem for the axle would also be a problem for the whole airplane." [Page 2-1]

"To be effective, the inner stub should be almost as long as the axle, largely nullifying the anticipated benefit of the divided axle...." [Page 2-14]

I don't think Pete thought the gear was less strong; I suspect he was just trying to steer people away from building something that was more complex but didn't have any real advantages.

Fly Babies have flipped on their backs when landing in tall grass, but it is a pretty rare event...and, like Pete says, grass that tall might just flip a split-axle plane as well.

My personal opinion is that they aren't necessary, but if someone prefers the look, they should at least recognize that it's going to take longer to build.

But allow me leave this topic with a great story on the subject from Harry Fenton:

I can relate one benefit of the split axle gear- tall grass clearance!!  A couple of summers back I landed at the airstrip on the family farm.  It had not been mowed for some time, and the clover was in bloom, so the overall height of the greenery was about 10-12 inches.  Being that it was the family strip, I gave it no thought as I knew it like the back of my hand.

The landing was a non event and I taxied back to take off.  Acceleration was routine, but a bit slow, something I would anticipate to be correct with the grass length.  The climb out was routine except for a noticeable buffet.  I headed the Fly Baby back to Cottonwood Airport, about 15 miles to the south.  As I chugged along, I was puzzled why my airspeed was pegged at 70 mph, a full 12 to 15 mph slower than normal.  I must have got some fuzz or something in the pitot tube, I reckoned and plodded back to the airport to land.

As I was flaring to land, I noticed that the Baby required just a tad more force to flare out.  What was really unusual was the small crowd of onlookers elbowing each other in the ribs and pointing to my plane.  The clearly puzzled expressions on their faces puzzled me even more.

I taxied up to the hangar, shut down, and hopped out.  It took about a second for me to understand the that the speed loss, flare pressure, and puzzled onlookers were all related to a common item- the hay bale of grass and clover wrapped around the straight axle!  I pulled two five gallon buckets of cuttings from around the axle that had formed about a 1 foot high bale across the axle.

Maybe a serrated edge on the axle would be a nice safety device!

Ron Wanttaja