The International Cessna^® 170 Association

After studying the Pponk design and the normal installation. I see no detriment to the gear if the Pponk is installed. What I did see is that without the Pponk gear the gear leg bolt would fail during a side load operation quite easily. With the Pponk install it would make it more rigid. Either way the nemisis is the side loading of the gear is what causes the failure of the gear in both cases. The Pponk is more forgiving but in either case if the gear leg was to fail, there would be considerable damage to the fuselage. If you actively fly crosswinds in excess of 9 knots cross wind component you will benefit from the Pponk installation. The Pponk is installed on our 170. D

ghostflyer wrote:That's why I do not want P Ponk fitted to my aircraft . When things go wrong ( a real bad day) I want bits that stick out to Break away cleanly and try to keep all the nuts and bolt ,rivets aligned. Energy absorption should be taken over a wide area as much asossible. The cabin area should be remain intact as much as possible .

That way, only a minor error/mishap can become a total insurance write-off, instead of it taking major error to do that, heh?
Tell me how hard you intend to hit the brick wall or to ground loop....and I'll tell you if you'll need
Seat belts.....or P-ponk.....
I endorse the use of both.

Any mass when in a moving state has a certain amount of kinetic energy , to bring this mass to a stop it's best to spread the load (kinetic energy) over the greatest area as possible . If there is impeding stoppage , structures (P Plonk) that concentrate the load factors to a central point and the energy is absorbed in this area the most damage will occur in this area . If this area survives with the P Plonk fitted some of the other structure must absorbed the kinetic energy and the question has to be asked ,has it been designed to absorbed extra kinetic energy and has it deformed or failed . Energy can't be destroyed only changed in shape or form .
Most race cars(formula 1 cars as a example ) have this concept designed in . While the Cessna cabin is not the perfect safety cell ,it's one of the better one around . If the area under discussion (gear box) had a inherent problem I am sure Mr. Cessna would have fixed the problem with the rest of his models.
I check the "Jesus bolt " on a regular basis for elongation or distortion and every 500hrs it's changed . The bolt that I am referring to is the main attach bolt that attaches the undercarriage to the airframe.

I have tried using visqueen or garbage bags instead of grease plates and have never found them a accurrate as grease plates.

As far as changing the "Jesus" bolts is concerned, a 5000 hour airpane would have gone through 200 bolts in its lifetime. Seems like a hell of a lot of overkill to me.

not at all uncommon for a Cessna spring gear leg to be deformed... be a shame to do all that work & still have bent gear. easy to check when you go on floats.... not so easy if you stay on wheels unless it's obvious (some are). mebby you can borrow some legs. there are several places that will inspect, re-arc and heat treat them. Seaplanes North is one... I know theres others the states but names escape me... somebody in Seattle for sure. XP Mods used to do them too

Someone asked me to post pictures of the gear on the 170 in question

Here is one of the main gear - And one of the tail wheel assembly - And a side view of the plane - Regards
Jim

Jim, I see your tail wheel problem. That wheel is mounted backward.

Ok, no obvious problems that I see with the tail wheel setup. It actually has all the parts assembled correctly. Not uncommon that this is not the case. Probably needs to be disassembled and cleaned. shouldn't really be any grease between the brass friction plates. Reassembled and the king pin nut adjusted.

It's probably a illusion but the first photo of your front right gear looks like the tire has bad tow out.


Thanks for posting the pictures.

Bruce

Jim, okay, from this perspective it looks like the tailwheel kingpin is leaning forward. It is probably parallax, but it would help if you got on the ground level and took a profile picture of the tailwheel again. This is what you are looking for. If the Kingpin is leaning forward at the top, a few different things can be wrong. You either have an improper torqued or stretched tailwheel bolt, or you have a fatigued tailwheel main spring. The bottom longest spring in the stack.
Your right main tire looks like normal wear. What does the left main look likeD

So............................

I'll really test the patience of this group by asking more about the powerplant part of my initial question. After some rough running engine experience resulting in a quick return to point of origin, a local mechanic presented me with the following punch list:

1. Compression check showed #5 cylinder with a leaking exhaust valve. This means a rebuilt cylinder at minimum.

2. Carb appears to have about 50 years since overhaul

3. Mags same as carb (actually was redone in 1981)

4. Ignition harness old

5. Exhaust system worn and leaky

6. Intake hose rubber old an cracked.

The carb almost certainly has a dozen or so Service Bulletins that need compliance. Depending of if the mags were done, and where, they almost may have outdated parts in them. Exhaust system could stand to be replaced, but probably isn't critical at this point. Intake hoses are cheap and relatively easy, but probably not a primary part of your problem.

The mechanic stated that he could probably get the O-300 back in shape for $4-5k, but you never know what the bottom end of the engine, cams, etc. will look like after the engine comes apart after 50 years. The engine is very weak and I don't know if that can really be explained by a leaky exhaust valve. The engine was overhauled in 1963.

So the questions.... I am also considering installing an O-360 probably not constant speed - thoughts and experiences? Should I spend the $5k to patch it up and fly for a year and then do the engine swap? Are there bogeys to watch out for when working these old powerplants over?

Again - I very much appreciate getting the benefit of the wisdom, experience and maybe most of all patience of forum participants

Regards

Jim

Jim, you will be receiving a lot of good suggestions from some knowledgeable folks on this forum. There is a lot of experience here. I am not making any of those suggestions, but will give you my $.02 worth. Certainly $4-5k to get your engine back into running shape is much less than the $30k+ you are likely to spend with the O-360 conversion. However you may be rolling the dice with the $4-5k investment as there could be lots of other gremlins ($$$$) hiding in there. Why not put that money into the conversion? Aside from the expense I would wonder why, when you do your conversion, you wouldn't add a cs prop? Good luck with whatever route you choose. Keep us in the loop with your progress.

jimnh20 wrote: 1. Compression check showed #5 cylinder with a leaking exhaust valve. This means a rebuilt cylinder at minimum.

A leaking exhaust valve doesnt mandate a rebuilt cylinder. Have you tried staking the valve with a malette? If the airplane is airworthy, go fly it hard and leaned out for an hour and re-check compressions.

jimnh20 wrote: 2. Carb appears to have about 50 years since overhaul
3. Mags same as carb (actually was redone in 1981)
4. Ignition harness old

My mags were from 1972 with about 1500 hours on them along with the harness and I still made static runup. I swapped them out for peace of mind because I had the cash else I'd still be flying them. My carb was last done in 1993 and I'm now starting to have an issue with idle-cutoff so I'll be picking up a rebuild kit this winter.

jimnh20 wrote: 5. Exhaust system worn and leaky

The gaskets and clamps are easy to replace. Cracks can be welded.

jimnh20 wrote: 6. Intake hose rubber old an cracked.

Mine are old and cracked on the ends as well. But they still seal. Spray some WD40 over them while the motor is running and see if you notice an RPM change. If not, they are fine.



If you have the money, swap out to an IO-360 and don't look back.

If not, find a mechanic that knows how to work on old airplanes (a leaky valve does not mean an overhauled cylinder).
So long as it's making rated power in a static runup and isnt making metal, I'd keep flying it.

This decision will probably be driven by available cash more than anything.

I'm sure this will spark a lively debate, but the reasons that I would not opt for the c/s with the O-360 conversion are: expense; simplicity of operation and maintenance; and my opinion that the c/s is not really needed given the additional horsepower on the light airframe and the usual short haul missions.

I'm all ears

Jim

You could put a pretty coarse fixed pitch prop on there that would help a lot in cruise and your takeoff performance would still be better than it is right now.

My $0.02
If I was to swap to a 360, that means that money isn't an issue. (if it was, I'd be working on keeping the O300 flying).
I'd put the CS prop on there. Possibly the MT electric prop. What's another $10,000 on a $40,000 upgrade??

jimnh20 wrote:I'm sure this will spark a lively debate, but the reasons that I would not opt for the c/s with the O-360 conversion are: expense; simplicity of operation and maintenance; and my opinion that the c/s is not really needed given the additional horsepower on the light airframe and the usual short haul missions.

I'm all ears

Jim

Jim, that is very reasonable. It also adds 70 lbs to the nose. Not worth the performance trade off.

Jim,

You really haven't told us much about this engine. What is it's recent history?

Sounds like you have some log book investigation to do. A 50 year old carb that is working has only one Ad to comply with that I can think of and that is the two piece venturi. And this is just a 100 hour inspection unless the venturi is loose. There were float and needle ADs which you need to review but I believe those all resolved themselves eventually that the original stuff was ok. But again you need to do do diligence and review your log history and the course of each AD. You can do this yourself and present a detailed history and findings to a mechanic and save him some time.

The mags will also need to have a log investigation. You did not say what mags you have. Makes a difference when it comes to ADs. The Scintilla (Bendix) SF6LN-12 have no ADs the much more popular Bendix S-20 series have a few and some that have come and gone. Certainly if no one has looked inside the mags since 1981 it is due.

Harnesses can be tested and leads replaced as necessary. You don't even have to remove the cylinder to fix a leaky exhaust valve if you find the right mechanic and intake hoses always look worse than they are.