The International Cessna 170 Association

jrenwick wrote:

4517C wrote:...Also consider using the "heavy" AN 363 nut on the single bolt attaching the gear to the airplane. That nut has failed in the past with an axial load and the AN363 is considerably stronger than the AN 365. Jake

Or install the Pponk "beef-up" kit, if you don't already have it.

If one is going to use NAS bolts because of higher-strength on the axle...why not at the upper gear-leg? (And while you're at it...why not use a NAS nut on a NAS bolt? (AN365 = NAS1021N, AN363 = NAS1021A)

I agree that the best solution for upper gearleg failure concerns is the Pponk mod.

4517C wrote:... the AN363 is considerably stronger than the AN 365. Jake

Looking at this chart on pg. 52 it appears that the AN 363 and 365 both have a tensile strength of 125,000 psi. Maybe you engineers could tell us why not use H29248-5 and BACN10HR6 nuts which are rated at 220,000 psi tensile? They are available here for a little less than $4.00 each. Edit: Coast Fabrication was bought by Clarendon Specialty Fasteners, Inc. As long as we're going overboard why not use MS21250-05018 and MS21250-06018 bolts to attach the axles? They are rated at 180,000 psi tensile and have a min. shear rating of 108,000 psi. Compare this to what Cessna calls out for the ski axle bolts. NAS 145/NAS 146 bolts=MS20005/MS20006 are 160,000 psi tensile and 96,000 min. shear. The NAS 145 bolts are over $37 each at General Aviation Hardware while the stronger MS21250 bolts are between $7 and $10 each from Coast Fabrication. All of these require the use of special washers as discussed elsewhere. A good reference is this catalog from Coast Fabrication.

n2582d wrote:Looking at this chart on pg. 52 it appears that the AN 363 and 365 both have a tensile strength of 125,000 psi.

That just means that both are made out of 125,000 psi tensile strength material. The psi stands for "pounds per square inch". The AN363 nut design has more "square inches" for a given bolt size than an AN365, and is therefore stronger. Of course, for a given design, a nut made out of 220,000 psi material will be stronger than one made out of 125,000 psi material.

Cessna170driver has pointed out the the AN363 nut has more square inches in shear since the metal fingers have structual strength. The first people that I know of who swiched the nuts were the mechanics for Maine Fish and Game. They had experienced some failures with 180s and 185s and reasoned that switching nuts might be might be a easy, fast cheap solution. The bottom line is that it worked out.
When nuts and bolts are specified by designers they usually are not searching for the strongest fastener available but also must look at toughness and fatique. Very strong bolts with higher hardnesses are more brittle. In the case of the axle attachment bolts that I referred to in a previous post, the bolts were stretched out, but the plane was upright still sitting on its skiis. Jake

n2582d wrote:Scott,
In cleaning out my inbox I found the information you were asking about. Titanium axles are available from Erik van Veenen. Eric's e-mail is pent-ax-5dATt-online.de (replace the AT with @). The lead time is 8-10 weeks as they only make small batches at a time. Now, are you sitting down? The price is $1150/axle. I'd want to see a PMA or STC for that price. On the other hand Cessna wants $1067 for their steel axles (p/n 1441003-1), what's another $83 to get titanium?

Titanium Axle.jpg

Recently came across this older post…and recalled a warning against using CAD plated hardware with Titanium.

MIL-S-5002 prohibits all contact between titanium and cadmium on military programs." Cadmium plated clamps, fixtures, and\ jigs should not be used for the fabrication or assembly of titanium components or structures.