The change from '56 to '57 C182 gear legs was accomplished via field approval from the Seattle FSDO. Advocating for a lower, wider & stiffer gear ('57) was easy and I'm not sure if going the other way would be.

What grade steel is currently used in the gear legs?

No clue about the grade, just that it's referred to as "spring steel." In '56 it was 11/16" and later ('57 and on) was 3/4". The same changes were made w/the 180 gear legs, though I don't know the years the changes were made.

I'm about to do the spectrographic analysis on a bent 1962 172 gear next week, so I'll know what it is for sure. Probably 6150 or a modification thereof, from what I've found online. But I have to be able to show the FAA what is is, before I can have an engineer say that XYZ is better.

Littlecub is right unfortunately, we're definitely not in a growth phase in aviation. But I'm not going to roll over and die, or get rolled over by someone else's agenda, "without a dandy fracas" as an old saying goes. It may turn out that my STC customer base winds up being people in Alaska who have a niche for a less expensive, lighter duty bushplane... or people who had to sell their beloved 300HP 185 because they could no longer justify the expense and insurance... I don't know.

It has not escaped me that I'm embarking on a program to develop something for what are basically 55 year old airplanes. What I do know is there are a few thousand of these airplanes out there, and if a small percentage of them can see the value of making their trainers or family sedans into more capable adventure machines that perform slightly better and carry slightly more... at an Obama economy price... I have a fighting chance at making a go of it.

Maybe this recession and "doom & gloom" will play out like a smaller version of the Great Depression, there will be an end to it, and just maybe the world isn't coming to an end after all. If we were all hanging out on an internet discussion board in 1935, we'd be crying that all of our fun and frolic we remembered from the roaring 20's will never be back and our way of life is doomed. As mentioned, the problems of the 1970's caused a similar panic.

I dunno... I'm kinda worried too, but I also don't have anything else right now that has any greater potential to pursue. If I happen to invent the As Seen on TV geothermal powered electric Lobster Shell remover tomorrow, and Ron Popeil wants to hire me to develop it with him for $25K per month.... then the 172 tailwheel conversion may get postponed slightly Till then I'm not quitting my part-time day job, and my cash cow airplane modifications empire is still chugging along in full world domination mode

EZFlap wrote:6150 or a modification thereof

6150 would be an expensive choice, but it is easy to work with.

Congrats on the new project. Just remember, like several folks already said, the swept back tail just doesn't have enough rudder authority for the conversion. As they also say, been there and done that, and it didn't have enough authority. Before we could put a square tail on it, I ground looped it and it now lives in the Calgary area. But then again, it got me into the 182 so it wasn't all bad..... The converted 172A is in my photo gallery from before it looped on me. It was called "The Buzzard"

lesuther wrote:
6150 would be an expensive choice, but it is easy to work with.

If you have significant experience in this area, I'd be very happy to have your opinion on what other alloys would perform equal or better, which would be less expensive... if that exists.

AKGrouch wrote:
As they also say, been there and done that, and it didn't have enough authority. Before we could put a square tail on it, I ground looped it and it now lives in the Calgary area.

Howdy 'Grouch, did you try the VG's on the swept tail to see if that gave you back any of the rudder?

EZFlap wrote:
Howdy 'Grouch, did you try the VG's on the swept tail to see if that gave you back any of the rudder?

Nope. Never did. Looped the bast#$* first. It had a definite xwind problem and always tried to go left on a wheel landing. Something was tweaked but we couldn't find it to correct it. I tried to deal with it 2 summers and it finally bit me hard and I walked away from it. Hope to see you again this Spring at the trade show in Anchorage.

AKGrouch wrote:....Looped the bast#$* first. It had a definite xwind problem and always tried to go left on a wheel landing. Something was tweaked but we couldn't find it to correct it.......

Did you ever check the wheel alignment? Incorrect castor (aka toe-in/toe-out) has caused many a groundloop. I beieve it is the main reason for the Pacer's bad reputation. I have flown Pacers with the castor set correctly and they were a joy to land. Excessive toe-in or -out is easily corrected on a Cessna using the factory tapered metal axle-mounting shims, although it can be a lengthy trial-and-error process. Lack of wierd or excessive tire wear is not proof that the toe-in/out is set correctly.

hotrod150 wrote: Did you ever check the wheel alignment? Incorrect castor (aka toe-in/toe-out) has caused many a groundloop. I beieve it is the main reason for the Pacer's bad reputation. I have flown Pacers with the castor set correctly and they were a joy to land. Excessive toe-in or -out is easily corrected on a Cessna using the factory tapered metal axle-mounting shims, although it can be a lengthy trial-and-error process. Lack of wierd or excessive tire wear is not proof that the toe-in/out is set correctly.

Yep we checked it. We finally determined that the problem was likely a bit of twist in that the vertical was maybe a bit off center. When we did the weight and balance, the left main weighed 103 lbs. more than the right....never could find the bucking bar.....lol. No, the bird had a tweak in it apparently back in the tail. The mains were spot on in their setup. I have no regrets though. Got the restore/custom rebuild, 337 to the max bird, conversion from trike to conventional and bush bird, etc. out of my system. Never did and will never figure out just how much it all cost. I'm happy with my little Cessna truck on 8.00's even though that 180hp 172 with the manual flaps sure did get up and go quickly. The 182 will get me anywhere I want to go such as back country strips, gravel bars, etc., and quite a few places I shouldn't....lol.

I have a few questions for experienced Cessna operators, rebuilders and mechanics:

In studying the 180 landing gear box parts I got from a junkyard in Canada, and after researching a few steel landing gear failure analysis papers, I have three questions ... thanks in advance. Your assistance will result in more/better/cheaper PMA replacement parts in the field applicable to 170/180's.

First question... There are shims that get tightened into the gap above the landing gear leg, in the outboard "slotted" gear bulkhead. These shims are obviously there to take up any up-down play or wear after years of landings. Clear enough. But there are no shims at the forward and rearward edges of the slot in the outboard bulkhead. So any play or wear at the front and rear of the slot would simply get worse, and allow the gear leg to move fore and aft. in the slot, with the gear leg "rotating" around the inboard vertical attach bolt.

So my question is whether the Cessna design simply relies on a tight fit as you slide the gear leg into position, and allows the edges of the steel gear leg to pound on the edges of the slot. Or is there some shim or other "centering device" that I did not get in my goodie box form the junkyard?

Second question for those with experience... if you were going to make up a new gear box for the 170/180, what would you do different than Cessna did?

Third question. Can anyone on this forum provide me with accurate dimensions and/or a copy of the drawings for the late 170 "Lady Legs" and/or the early 180 gears? I know I can ask Cessna for the drawings, and they will either tell me to pound sand or pay a large amount of money. I'm tryin' to get around that problem without too much re-distribution of wealth

EZ, I have a set of early 180 legs off of our 54 180. Let me know what you need, and I will do my best.

EZFlap wrote:I have a few questions for experienced Cessna operators, rebuilders and mechanics:

In studying the 180 landing gear box parts I got from a junkyard in Canada, and after researching a few steel landing gear failure analysis papers, I have three questions ... thanks in advance. Your assistance will result in more/better/cheaper PMA replacement parts in the field applicable to 170/180's.

First question... There are shims that get tightened into the gap above the landing gear leg, in the outboard "slotted" gear bulkhead. These shims are obviously there to take up any up-down play or wear after years of landings. Clear enough. But there are no shims at the forward and rearward edges of the slot in the outboard bulkhead. So any play or wear at the front and rear of the slot would simply get worse, and allow the gear leg to move fore and aft. in the slot, with the gear leg "rotating" around the inboard vertical attach bolt.

So my question is whether the Cessna design simply relies on a tight fit as you slide the gear leg into position, and allows the edges of the steel gear leg to pound on the edges of the slot. Or is there some shim or other "centering device" that I did not get in my goodie box form the junkyard?

Second question for those with experience... if you were going to make up a new gear box for the 170/180, what would you do different than Cessna did?

Third question. Can anyone on this forum provide me with accurate dimensions and/or a copy of the drawings for the late 170 "Lady Legs" and/or the early 180 gears? I know I can ask Cessna for the drawings, and they will either tell me to pound sand or pay a large amount of money. I'm tryin' to get around that problem without too much re-distribution of wealth

Nope, you are not missing any pieces. The gear leg just slides in, not particularily tight.
The only other shims in the system are ones that go under the inboard end of the leg to level the wings within tolerance.

side slip wrote:
Nope, you are not missing any pieces. The gear leg just slides in, not particularily tight.
The only other shims in the system are ones that go under the inboard end of the leg to level the wings within tolerance.

THANK YOU for solving this mystery !

So am I correct to assume that since (per your post) it's not really a tight fit to start with, and landing wear & tear makes it worse over time, you could move the gear fore and aft a couple of degrees on most older 170's and 180's sitting out at the airport ? To my pea-sized brain, it sounds like a recipe for taildragger handling problems, toe-in and toe-out changing without warning, etc.

Thanks to the people offering assistance here, I really appreciate it... keep it coming!

The gear really doesn't move around, and I can't say I've ever seen any appreciable wear in the fore and aft parts ofthe gear box. Once the gear is installed and the shims are tightened down, the loads primarily become torsional in the box. Even under heavy braking, the box mostly see's twisting instead of aft drag load.
The shims to level the plane are installed between the gear leg and the top surface of the gear box @ the bolt, and no more than 3 can be used.
The whole system is surpisingly good, considering how many were built, and how rough they have been used over the years. Failures typically only occur during ground loops, when the gear gets rolled under the plane.
The pponk mod is great, and does make the box stonger, so if you are making all new parts, there is no reason not to include them too.

Thanks. I am planning on (hopefully) offering the PPONK reinforcement blocks along with my parts kit.

Update:

1) Congratulations to Mr. Kent Rhodes of Seattle, the first Fravel 172 tailwheel conversion customer since I took over the STC.

2) I have been made aware of an additional replacement parts source for Cessna OEM style main gear attach fittings, Mr. Bob Salyer from Tennessee. Bob is planning to produce PMA identical replacements for Cessna's outboard and inboard gear mount fittings. Bob Salyer 615 289 6400. Of course PPONK Aviation also manufactures an approved replacement outboard fitting. The Salyer parts (once they receive PMA approval) and the currently approved PPONK parts, would be usable as part of the tailwheel conversion STC, and for repair/replacement purposes.

3) The Fravel STC upgrade process continues, but there is still a ways to go. A new stronger tailwheel attach / rudderpost fitting has now been designed. Machined steel forming dies for the forward flanged bulkhead reinforcement have been fabricated, and are in the testing stages for hydroforming and Guerin Process Elastoforming (poor man's hydroforming). CAD modeling and drafting of the inboard and outboard machined billet gear attach fittings is nearing completion.

Hey Bill, Does your STC include 150"s?

The Fravel STC does not currently include 150's, and I have not yet looked into that possibility. The big question of course is how many years did Cessna use the same lower fuselage structure on the 150 as they did on the 140. What you can do is research this question, and positively identify if and when the lower fuselages are the same from 140 to 150.

If (and I say IF) it is anything like the 170/172 then there should be a 4 to 6 year period where the 150 is basically the same as the 140 in that area. The other thing is that you need to figure out whether the landing gear attach structure is common from the 140 to the 170 (because that would mean that my 172 PMA parts would fit in your airplane) . Check the 140 and 150 parts manuals, and if we are even close I can certainly talk to you about helping you go after a one-shot STC.