PPonk STC

[davevramp]

I have a 54b that I am going to do the PPonk STC on. My plan is to remove the gear ledges clean strip and if I can, Magnaflux paint and reinstall. Is there any thing else that I should do while it is apart.?
Thanks
Dave

[mrpibb]

Just take a good look at your inboard and outboard castings for corrosion and check for any pulled fastners. So far out of the half dozen of pponks that my friend has done 4 of them had some form of problem or another. Dont forget to retorque the gear wedges after 20 or so hours.
heres a casting from a what started as a pponk mod that turned into a gearbox repair.

[davevramp]

I am putting the landing gear back together after the PPonk installation.
With the gear in place and all bolts snug but not tight and the shims out, I can mover the landing gear back and forth in the gear box. What locates the gear in the gear box? What do you do for alignment? What position do you put gear in to tighten the shims?
Thanks
Dave

[lowNslow]

Dave, here is note from Pponks old web site that might help, it's for a 185 but still should apply.

Main Gear Installation on a 180/185

By  Steve Knopp

March 15, 1999

Question:
I am installing 185 main gear springs on my 57 180. There is a slight amount of play fore and aft in the outer casting. In the service manual they don't show any shims in this area. If I were to shim the gear to prevent movement fore and aft at the outer casting should I shim the front or rear of the gear?

Answer:
P. Ponk Aviation manufactures a beefed up version of Cessna's outboard gearbox bracket. Many of our parts are purchased by consumers because wedges and shims were improperly installed. They were driven in too far and too hard, damaging the upper portion of the original casting by reforming the metal into a sharp edge, causing stress fractures on the upper portion of the original bracket. In my 30 some years experience, I have inspected hundreds of brackets damaged in this manner.

The wedges and shims are intended to take up any slack and hold the gear to the bottom of the bracket, and will hold the landing gear from moving forward after landing when you set the tail on the ground. They will not hold the gear from moving aft under the load of landing and braking, no matter how hard you POUND them in.

Steps to Installation

1) Hoist the airplane.

2) Install your gear in the aft position. This should leave you 1/16th to 3/32nds inch gap between the gear and the front of the bracket. If the gap is larger than this, check the rear portion of the bracket that touches the landing gear to see if it has compression damage due to years of use and striking objects with the landing gear. (Inspect for stress fractures and cracks in any compressed areas.) A symptom of "too large a gap" is a chronic "clunk" when you land or take off. Tightening the shims is only a temporary fix for the problem...the "clunk" usually comes back.

3) Install the wedges and shims so that they do not push all the way in and bottom out. If they bottom out, install an extra shim. (Parts Manual allows more than one shim. You also may need a thicker wedge.) There are 2 sets of shims and wedges holding each set of gear in place.

4) Tap the forward wedge lightly with an aluminum punch and hammer to set the wedge. Screw your 1/4" bolt up snug to the wedge.

5) Repeat this procedure for the rear wedge.

6) Tap the forward wedge again lightly with a punch and hammer to reset the wedge, and again snug up the 1/4" bolt.

7) Repeat this procedure for the rear wedge.

Note: Do not over tighten this bolt...it is there only to keep the wedge from backing out. DO NOT POUND IN THESE WEDGES, THINKING YOU WILL KEEP THE GEAR FROM MOVING. You only will damage the outboard brackets (and keep me in business).

For those of you who are reading this, if you are interested in seeing how your landing gear is installed in your aircraft, go to our web site http://www.pponk.com and click on the picture of the outboard gear box bracket(it takes some time to load...just wait for it. It is worth it. This is an exploded view of the landing gear box.

Steve Knopp

P. Ponk Aviation

[GAHorn]

This why I am a proponent of the Pponk beef-up kit. If all the parts illustrated in Steve's kits are utilized the durability and strength of the landing gearbox is considerably improved, not only from a physical-support standpoint, but also from a materials standpoint.

Anytime someone is considering an aircraft purchase and making comparisons between potiential aircraft.... give extra value to a Pponk modified airplane, especially if the outer brackets are replaced along with the inner beef-up bracket. That was worth another $1,000 to me when I bought my airplane.

[davevramp]

It is back together. Tracks well and is stronger than before. My main interest was to inspect the gear and gear box. The gear ledge need some paint. . Cleaning and painting took more effort than the PPonk installation. Thanks for the help, comments and advice. It really helps when you have things apart. If any one is thinking of doing this mod please feel free to contact me before starting.
Dave

[pojawis]

How did you hoist your a/c? I've had my kit for awhile, but haven't installed it for various reasons. One was finding a safe, easy way to hoist the a/c. I was thinking of using an automotive engine hoist hooked to the a/c engine, lift and leave one tiedown secured while removing the opposite gear leg and effecting the modification.

Caveats ?

[johneeb]

Pojawis,
When I did my PPonk modification I used tall jacks at the tie down rings. Subsequent to doing the PPonk mod I made the cradle shown in the link below and would try using it to do the PPonk mod however the cradle may interfer with access to the large bolt at the top of the gear leg.

http://www.cessna170.org/forums/viewtop ... it=jacking

[blueldr]

I've seen them hoisted with a shop crane or a chain hoist with straps under the two top engine mount legs at the firewall.

[GAHorn]

Using padded 2X4's (carpet works well) beneath the fwd wing-spar, immediately outboard of the strut, you can jack the aircraft with tall aircraft floor-jacks (like the type normally used on high-wing 210's etc.)

A cheap alternative is found at http://www.harborfreight.com/cpi/ctaf/d ... mber=41860 for about $60 (it telescopes and incorporates a screw-jack at it's top):

[cholzer]

Did an annual on a C-170A a few years ago that had the P-Ponk mod previously installed. Found the 7 rivets on the gearbox lip broken. Replaced them, and asked the owner if he had any idea how that may have happened? His reply was that he flew from a grass strip, and he liked to do touch and goes on the right main gear only. After paying me, he won't be doing that any longer. As a side thought, when an unmodified plane does a ground loop, hopefully, only the gear leg gets pulled away from the fuselage. On a modified plane, with the beefed up structure, the gear leg and part of the fuselage will most likely get ripped off. Any thoughts on this?

[Bruce Fenstermacher]

The thought in my mind is that today with the high cost of repair and parts becoming harder to come by any damage to the gear box is likely to total the airplane.

So by beefing up the structure to raise the threshold for any damage you are saving airplanes that would be lost. Of course once the threshold for damage is crossed with the beefed up structure the damage is usually greater but the plane would most likely have been lost with any damage anyway. Prevention of damage not repair is the goal here.

[voorheesh]

Re. further thoughts, that is a good reason not to use Pponk. My 170A is 59 years old and has survived without Pponk, why change now? I guess if you fly alot on rough strips it would probably make sense but for me I am sticking with original Cessna design.

[Bruce Fenstermacher]

Voorheesh that is fine. I don't have it either but would like to have a PPonk mod.

I can't help but think you missed my point. It's not the Cessna didn't have a good design. In fact you could say that 59 years ago when parts and expertise to accomplish the repair was readily available, it was a great design because repair could be accomplished in most cases.

A lot has changed in 59 years and parts and expertise are not readily available or cost prohibitive for the average owner. Today any damage to the gear box repairable or not is likely to total the airplane. So now we have to protect the system we have better because repair is not the option it use to be. It has also been said that an accident that causes damage to a Pponk modified airframe and totaling it would have also totaled the unmodified airframe.

Again I don't have a Pponk mod but would like to have one because I see the value of raising the threshold for any damage.

[voorheesh]

Bruce, I was not referring to your thought which makes sense. I was referring to the IA in the previous post who asked if P-Ponk could cause worse damage to the gear structure in a ground loop. The mechanic I work with talked me out of using P-Ponk because he believed he could repair damage from the gear simply being pulled out or bent. He believed that P-Ponk "could" destroy the airplane in a similar ground loop. This same mechanic was also very opposed to disabling the parking brake so it goes to show there are many diferent opinions in this business. Anyway, your point was well taken and I'm sorry for the confusion.