Axle Insert Reinforcement

[jaredyates]

Has anyone done the optional modification to insert a piece of tubing into the axle with Loctite? I'm wondering how to best prep the inside of the existing axle to make it the right size. The original notice suggests using a reamer, which I'd rather not have to acquire just for this limited use.

[whee]

I don't know how much cleanup the inside of the axle takes but what about renting a cylinder hone from the local auto parts house?

[bearhawk2015]

I honed mine, it didn't take that much work and the loctite is holding up good

[bestbearhawk1231]

I plan on using a flex hone when I do mine. A lot cheaper than a lathe or a reamer. Since I will be doing it on installation I am seriously considering rosette welding it in, even I though I have no doubt that locktite sleeve retainer would work just fine.

[alaskabearhawk]

Lots of info on this from the old group. I'll try to dig through my old archives tomorrow.

[Helidesigner]

I used a large drill. The inboard part of the axle tube was slightly undersized.The drill cleaned it up nice. The outboard section was good. It did not take much time. Be sure to lather up the reinforcement tube well. Once you tap it in it is not coming out.

Mark

[alaskabearhawk]

It seems like the drill would leave a sharp ridge on the inside where it stops, leaving a potential stress concentration point unless it was dressed out.

[Helidesigner]

The axle tube goes inboard past the vertical V support tubes. All the bending moment and resultant stress is at the outboard side of the vertical support tubes. The very inboard end of the axle tube is under very low stress.

[Wayne Massey]

When I did mine it fix just fine without reaming or honing: http://www.mykitlog.com/users/displa...=143980&row=90

[Wayne Massey]

Actually that was before any welding had been done so that might not work in an already welded axle

[DRLPatrol]

I'm working on a Patrol so I had to look up and read about what you guys were talking about. The patrol has the same 1.5"x .120 axle, but at less gross weight I guess its OK?

Doug

[alaskabearhawk]

Why the concern Doug?

[alaskabearhawk]

From the archives and BearTracks:

I just got this back from Kevin. It looks like the axles were more than up to the task. The failure was self inflicted. Maybe Bob will make a recommendation yet, but I suspect he will be satisfied with these results. The little things DO matter.

"On the axles, bottom line is the one had a working crack for quite some time. The crack propagated
from a stress riser where the weld bead was ground away on the brake caliper attach ring welded to the axle.
A bit of weld was ground near the bolt hole to clear and square up the surface so the bolt / nut would sit square. This created a sharp little notch that actually had just barely cut into the axle.
Given the event the cracked axle broke from overload on the remaining un cracked portion of the axle.

The other axle is free from cracks. The ripping off of the axle from the gear leg was a pure overload failure.
Rob Gaddy had a metallurgist he knows look at it. His thoughts are conveyed above. "

Pat Fagan

I just finished the axle reinforcement that was in the newsletter a couple of years ago. What a pain. I didn't have a 1.255" reamer laying around and I couldn't find one to buy that was long enough (besides it was $60). I bought a brake cylinder hone to clean up inside the axle (only $15). I honed so much the little stones are completely warn down and the reinforcement tube still wouldn't fit in to the proper depth. I shifted to a new strategy; I used one of those thick Sharpie pens to color the end of the reinforcement tube and put register marks on the axle and the reinforcement tube so I could get it in the same orientation each time. I shoved the colored tube in as far as it would go - then pulled it out and filed where the ink was rubbed off. I repeated this operation many, many times - re-inking the tube each time. Finally, the tube made it to the specificied depth. Before I secured the tube with the Locktite goo (I used Locktite 620) I mounted the gear back on the fuse along with the wheels and measured to see if they were parallel and lined up with the fuselage centerline. I didn't want to have to heat the gear after I used the Locktite. (I got 1-degree of toe in and declared that good enough) Back to welding stuff to the fuselage.

Good luck with your projects,

Jim Van Fossen #411

This mod is recommended for four place Bearhawks that are going to be operated extensively at over 2200 lb.
gross. The tube should be Loctited in place with Loctite #277 or #620 per Loctite instructions.

[DRLPatrol]

Why the concern Doug?

No reason, just wondering.

Doug

[alaskabearhawk]

You're good I'm sure. Besides, you can always add it later if you want...easy access.

[Battson]

The axle tube goes inboard past the vertical V support tubes. All the bending moment and resultant stress is at the outboard side of the vertical support tubes. The very inboard end of the axle tube is under very low stress.

How do you know that's where most of the stress-concentration occurs?

I also note the weld geometry is different on old vs new kit legs, so the stress risers will vary depending on that.