BC12-D prop question

[T-Rex]

Re: BC12-D prop question

Yes, I removed the prop. I ran it for a few hours and switched to the MAC 1B90CM 71-42. I am on floats now, Baumann BF1420, and the combo really seems to work great.

[barnstmr]

Re: BC12-D prop question

I don't like or want to run it because of the fear of doing unseen harm to the internals of the engine.

T-Rex...
Did you remove this prop? If not, you should. - FYI - In general the aluminum blades will fail due to fatigue far sooner than the Steel internals of the engine whenever there are adverse harmonics involved.

[TonyL]

Re: BC12-D prop question

Hi LPS corrosion inhibitor is LPS3

[TonyL]

Re: BC12-D prop question

Hi LPS corrosion inhibitor is LPS3.

[jim cooper]

Re: BC12-D prop question

I have a wooden sensich prop on the T-Craft I recently purchased. It is supposed to be a climb-seaplane prop. I meant to write down the number but forgot. It looks like brand new (as does the rest of the BC12D). Has anyone had experience with this type of prop? I seem to remember the length seemed quite short. JC

[astjp2]

Re: BC12-D prop question

I use LPS corrosion spray can...cant remember the number though. Tim

Re: BC12-D prop question

In this years annual ( 2010)I would like to remove and reinstall the propp hub on my A 65 just to make shure it dues have any corosion on the taper.
I dont see a requirment for it but as my plane is stored out side I think it would be good to check it.
Any suggestions as to what rust inhibitor to use. When I installed this engne 3 years ago we used CRS or similar.
Len

I use anti-seize compound and occsionally have coated the parts with small amounts of oil, grease or bees wax before coating with anti-seize. But antisieze is the constant.

The excess will fly out when you start the engine. My hub always comes of easily (usually after a few years of being installed). My plane was outside until 10 months ago.

Dave

[Len Petterson]

Re: BC12-D prop question

In this years annual ( 2010)I would like to remove and reinstall the propp hub on my A 65 just to make shure it dues have any corosion on the taper.
I dont see a requirment for it but as my plane is stored out side I think it would be good to check it.
Any suggestions as to what rust inhibitor to use. When I installed this engne 3 years ago we used CRS or similar.
Len

[cropduster]

Re: BC12-D prop question

Dano, You are right. The 76AK-2-40 prop I am running on the C85, is a stroker!

[Forrest Barber]

Re: BC12-D prop question

THE prop for the A-75 is the 70-38 according to the 337's we ahve here on file. the A-75 has to turn faster than the A-65 check the TC.

[jim cooper]

Re: BC12-D prop question

Quick answer? Those who can tell you quick are either North East propeller in Lancaster Pa. Sensich dealer or Leavens prop in Toronto. Or look up closest Sensich dealer on internet. JC

[Dano"T"]

Re: BC12-D prop question

I have 2 BC12D's....one with C90-12F and one with C85-8. The C90 has a Sensenich 76AK-2-40...works great....I tried it on the C85 though and barley got off the water....would only make 2150 or 2200 rpm...It's a great running C85 with only 200 hrs SMOH...I use a McCauley 71-42 on the c85 and it is a real performer....105 cruise and awesome takeoff. I'm surprised anyone could use a Sensenich 76AK-2-40 on a C85 unless it's a stroker.

[NY86]

Re: BC12-D prop question

...The 90hp champs generally use a M76AK-2-42 for floats and they work great, keep in mind 95 takeoff horsepower...

This is another "urban myth". The only way you can get 95 HP is if you can turn the engine up to 2625 RPM. The only setup that is certified to do that that I am aware of is the Beech-Roby controllable prop. All fixed pitch installations are limited to 2475 RPM and won't go higher in climb anyhow.

It does not make sense to me that prop can turn 2700 RPM on an O200 but cant turn 2575 safely on the c85.

Many significant differences between the two. The rods and crank throws are longer so the resonant frequency is different and the two engines produce like power at different RPM's, so the force of the hammer blows is different.

[cvavon]

Re: BC12-D prop question

I wonder if any one has looked in to harmonic balancer's like automotive engines Cummins diesel will brake crank shafts if the balancer goes bad also would act like a fly wheel and i think that would make more tork

[T-Rex]

Re: BC12-D prop question

This does not answer the original question but may help? I went through the whole prop search for T-Rex c85-12 just over a year ago. I wanted climb for floats but did not want to sacrifice to much in cruise speed. I tested a few different props. I had a Sen M74CK40 field approved and it worked great. Cruise just above 90 and great takeoff. This prop has no legal business being on this engine because of the harmonics it produces but the FISDO approved it anyways. I don't like or want to run it because of the fear of doing unseen harm to the internals of the engine. There is no installation where this prop is approved at this length on this engine on any TCDS that I have been able to find. IF you want to run a 74" Sen on a C85 Use the M76AK-2-38 or 40. It has a much larger/ beefier hub (center) section and a completely different blade profile. The chord is longer and is also thicker. This prop is approved on the C85 TCDS and is also approved on Cubs, Cessna 120 and 140's with the C85. In my opinion the Sen AK series do not spin up as good as I would prefer for float opps. where RPM on takeoff is king. The 90hp champs generally use a M76AK-2-42 for floats and they work great, keep in mind 95 takeoff horsepower. What I decided on was a Mac 1B90 CM71-44. Not a climb prop but not a cruise prop When light takeoff performance is in the 200 to 300 foot range with a 100mph cruise at 2400 RPM. At 2300 I get about 95mph, GPS confirmed. I looked into running the Mac 1B90 CM 74-38 or 40 but once again I came into the problem of harmonics and no instances of the being used on the C85 anywhere. It does not make sense to me that prop can turn 2700 RPM on an O200 but cant turn 2575 safely on the c85. I talked to Butch at Maxwell propeller repair at length about using one of the longer unapproved props and even in good old boy conversations he did not recommend it because of harmonics and vibration. IT is just the differences in the engine that make it work on one and not another.