whee wrote:

River rat wrote:I've heard that a cessna 337 rear engine mount bolts right up to a cessna 170, not a bearhawk I understand but it might be a good place to start. Hey it's experimental, get the saws all!

Another Bearhawk builder did just that. He got a rear 337 mount cheap and used it as a starting point. I've been watching for a donor mount but the going rate seem to be ~$800. I'm not doing that.

Been there done that....trying to make a Bearhawk Avipro O470 mount fit an IO520.... Didn't work. $400 spent to recover four 1-1/2" tubes with big washers for the motor mounts. I wound up making an adjustable engine stand bolted to the oil pan. The feet were height adjustable. Used a rotary laser to set the thrust line. Then built the motor mount starting at the rubber lord mounts...have pics....going to build another....a swing mount to have access to the starter drive, injection pump......

Are the "B": designated cases different than the cases without the "B," ie "D" vs "DB" "K" vs "KB"? The "B" crankshafts (big bearing crank) have one 6th order damper and one 4.5th order damper. The regular crankshafts have two 6th order dampers. In order to run a 82" C203 I need "B" crankshaft. I'm wondering if I can install big bearing crank in a case that had a regular crankshaft.

Not a clue. If journal diameters are the same but the crank shaft assemblies have different part numbers.... The difference might be the counter weight bushing arrangement.... Alaska aircraft engines might have the answers your looking for.

The case has to be bored to fit the the big bearing crank. Aircraft specialties can take care of the machine work. New rods are required too.

Reman cranks have proven impossible to find. A new crank from TCM is $6600.

You can run the 82" c203 prop on the non B cranks. There is an STC for it on the Stinson, and a number of field approvals on Maules.

chetharris wrote:You can run the 82" c203 prop on the non B cranks. There is an STC for it on the Stinson, and a number of field approvals on Maules.

Glad you finally chimed in. It is true that you don't need a B crank to run the C203 because some of the regular cranks have one 6th and one 4.5 order dampers. I should have stated that but my mind was focused on the IO360-D which has two 6th order dampers while the DB has one 6th and one 4.5.

From the IO360 TCDS:
Models IO-360-AB,-AF,-CB,-DB,-ES,-HB,-G,-GB,-H,-J,-JB,-K, and-KB incorporate crankshaft with one 6th and one 4 1/2 order damper

I have yet to determine if there is STCs or field approvals that allow the use of the C203 on engines with two 6th order dampers.
EDIT: The STC for the 170 allows the 80" C203 on these engines some of which have two 6th order dampers: IO360 A, C, D, G, H, J, AB, DB, GB, HB, & JB

Not sure that anyone cares but thought I'd document my learning here.

I asked about having a airmelt (non VAR) crankshaft inspected for cracks and returned to service in an experiential application. This could be acceptable and there in nothing really wrong with it other than completely ignoring an AD. It is note worthy that the TCM determined failure rate of the airmelt crankshafts is 1 in 14 and the VAR crank shafts have a failure rate of 1 in 40. Pretty substantial difference.

Also, in all of my research I somehow missed that the IO360 was on the crank case TCM service bulletin. Basically a phase 1 case (casting number starting with 629) is junk, a phase 2 case (casting number starting with 640) is ok, and a phase 3 case (casting number starting with 642) is the one you really want to get,

First Wee, I appreciate your gathering this information in one place.

I think the heavy, hump backed case is makes sense.

I am skeptical on the crank. I am particularly skeptical of Continental's data on this. If you have not read the AVWEB article by Mike Busch entitled "Who Benefits from Airworthiness Directives?", I recommend it: http://www.avweb.com/news/atis/184427-1.html .

The article suggests Continental makes some interesting claims, but the Aeronautical Repair Station Association (ARSA) says not all of the data was presented or considered. Arsa teamed up with the Aircraft Owners and Pilots Association, the Cessna Pilots Association, and the National Air Transportation Association and analyzed the FAA's Service Difficulty Report (SDR) database as well as their own repair data. Below is a quotation directly from the article relating what the combined groups found.

"They also pointed out that the FAA elected to ignore its own SDR database (which did not support the need for the proposed AD), and also ignored the analysis submitted by ARSA in February, 1994. ARSA's analysis was based on the results of ultrasonic testing of crankshafts required by AD 87-23-08 by TCM-authorized inspection facilities throughout the U.S. The ARSA data showed that companies had detected 27 subsurface fatigue failures out of 3,821 airmelt crankshafts subjected to ultrasonic test, for a failure rate of .707%, and had detected 5 failures out of 488 VAR cranks tested, for a failure rate of 1.025%. ARSA pointed out that these failure rates are statistically equivalent.

Furthermore, the joint Association response points out that the FAA's own supplemental notice 'exhibits a lack of confidence in the superiority of VAR crankshafts.' The proposed AD requires that VAR crankshafts undergo ultrasonic testing at every removal, so that 'clearly the FAA recognizes that VAR crankshafts are subject to the same unsafe condition as airmelt crankshafts. The FAA has offered no evidence to conclude that unsafe conditions exist in airmelt crankshafts that do not exist in VAR crankshafts. The two types of crankshafts should be treated in a comparable fashion.' "

I have read that the long term analysis shows that the airmelt cranks ended up failing less often than the VAR cranks. I do not have a source for that claim. If I was experimental, I might consider running the airmelt, but I would want to confirm reliability reports and not just Continental's claims.

Chet

Thanks Chet. I have not read that article but I will.

I image most have surmised that I have purchased a core engine for my BH. I knew the engine had an airmelt crankshaft but I did not know about different cases until today. Guess when the engine arrives next week I'll find out if I'll be shopping for a new case...pretty sure I will be. I'll either send the airmelt crank to Lycon to get checked out or I'll go with a VAR DB crank and have the case linebored to fit the crank. I have a while before any of that needs to happen. It will be nice to have a complete engine I can use to build a motor mount and cowling.

whee wrote:I image most have surmised that I have purchased a core engine for my BH. I knew the engine had an airmelt crankshaft but I did not know about different cases until today. Guess when the engine arrives next week I'll find out if I'll be shopping for a new case...pretty sure I will be. I'll either send the airmelt crank to Lycon to get checked out or I'll go with a VAR DB crank and have the case linebored to fit the crank. I have a while before any of that needs to happen. It will be nice to have a complete engine I can use to build a motor mount and cowling.

Sorry to hear you might be up for a new case.... fingers crossed you're not.
Not a big problem, but certainly a headache you would have been happy without during the build.

whee wrote:..... It is note worthy that the TCM determined failure rate of the airmelt crankshafts is 1 in 14 and the VAR crank shafts have a failure rate of 1 in 40. Pretty substantial difference.....

And the VAR cranks are considered good ??? with a 1 in 40 (2.5%) chance of failure?

That article from Mike Busch makes the airmelt AD seem like a bunch of hogwash. Just makes things more confusing.

From the reading and talking I've done it seems that if I'm going to comply with the AD I should just upgrade to a B crank and have the case line bored to fit the bigger crank. The cranks cost the same and the case work is only $850 including the overhaul and line boring.

I've been trying to research the airmelt vs VAR crankshaft AD and the crankcase SB as best and objectively as I can. Honesty, staying objective has been difficult because I have a airmelt crank and a phase 1 case and I want my research to prove using them will be fine. Obviously I've spent a lot of time on Google but I've also called as many shops as I can think of to get options and answers. I haven't called TCM because it seems obvious what they will say.

On the crank; I think I'm going to get it inspected and if it's good I'll use it. No one has said it is really bad and it will for sure fail. Most places I called did advise me to get a VAR crank but it seemed they mostly said that out of liability concerns. Lycon will inspect it and overhaul it if I ask them to.

On the crankcase; I just don't know. It seems the case does have issues and it would be best to have a phase 3 case. The places I talked to said it would be better if a got a new case. I agree but mostly because I can't find much info saying using it would be ok. I have read forums where guys are running phase 1 cases and airmelt cranks way past TBO because they don't want to buy a new crank. I don't put much weight in things I read on a unfamiliar forum but it is interesting.

When we came up against decisions like this, my wife and I discussed the following:

In 5 years time, when you are flying over inhospitable terrain with all the family aboard, will you be happy with the decision you made now?

We always ended up going the more expensive route, as a consequence.

In fact, maybe don't have that discussion

That's exactly what is going through my head. I've had the experience of engine trouble while flying over terrain with my family aboard. It almost made me quit flying. I would spend lots of money to make sure that doesn't happen again. But I also don't want to spend money needlessly.

Is this phase 1 vs 2 vs 3 case and airmelt vs VAR crank business specific to the IO-360, or is it applicable to all big Continentals? My C180 has an O470K that was factory remanned back in 1993 or so, and I haven't seen any SB or AD telling me to replace or even inspect the crank and/or case. Are some cases & cranks really no good, or are some just more highly sought after than others? I know people who say "if it's a J, walk away", and others who took that advice at OH time and upgraded to a K or R in their old C180. But some people I know (including at least one who "walked away") ran their old J engines to TBO and in some cases well beyond without any real problems. So don't believe everything you hear.

The O470 is not affected by the crankshaft AD nor the crankcase SB. The other big continentals are. I don't know the answer to your other question.

Took the engine to a friends shop where he has a flat bed scale. Placed the engine as pictured on it including the pallet and a few feet of chain. Total weight was 452lbs. Figure the pallet weighs 30lbs and there is at least a couple lbs of chain there so 420lbs for the FWF minus prop.

Untitled by Jon Whee, on Flickr

whee wrote:....On the crank; I think I'm going to get it inspected and if it's good I'll use it. No one has said it is really bad and it will for sure fail. Most places I called did advise me to get a VAR crank but it seemed they mostly said that out of liability concerns. Lycon will inspect it and overhaul it if I ask them to.

On the crankcase; I just don't know. It seems the case does have issues and it would be best to have a phase 3 case. The places I talked to said it would be better if a got a new case. .....

I'm afraid to even ask what a new crankcase would cost, but have you investigated a used serviceable crankcase of the style you want? The C145 in my old C170 broke a connecting rod about 13 years ago, and what was left of the rod punched a hole on the case. I don't recall the exact price, but a serviceable used replacement case was surprisingly inexpensive.

hotrod180 wrote:

whee wrote:....On the crank; I think I'm going to get it inspected and if it's good I'll use it. No one has said it is really bad and it will for sure fail. Most places I called did advise me to get a VAR crank but it seemed they mostly said that out of liability concerns. Lycon will inspect it and overhaul it if I ask them to.

On the crankcase; I just don't know. It seems the case does have issues and it would be best to have a phase 3 case. The places I talked to said it would be better if a got a new case. .....

I'm afraid to even ask what a new crankcase would cost, but have you investigated a used serviceable crankcase of the style you want? The C145 in my old C170 broke a connecting rod about 13 years ago, and what was left of the rod punched a hole on the case. I don't recall the exact price, but a serviceable used replacement case was surprisingly inexpensive.

Hmmm, thought for sure I responded to this. New case is ~$9.5K. I have yet to find a serviceable replacement case but I haven't looked very hard.

Anyone know if aside from the crankshaft would all the other parts off the core I have fit a phase 3 big bearing case? I've been studying the part manuals on the TCM website and it appears the camshaft, cylinders, and a few other parts I've checks have the same part numbers. My current thought is to find a new crank and case and put together one good engine.

So if you're looking at 9.5 for a case 6+ for a crank and probably 6+ for cylinders, plus the rest, have you considered going with a factory reman and turning in what you have as a core? The factory reman may or may not put your mind at ease down the road over the mountains. Just a thought, I haven't done the numbers.