Prop torque

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jesse

Touchdown! Greaser!
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Jesse
In order to remove my cracked exhaust from the Flybaby I had to remove the nose bowl to get to the number 4 cylinder. This meant the prop had to come off. I drew some lines with a pencil to ensure I could install it again the same way.

The prop was held on by lock nuts. What should these be torqued to during the reinstall? The engine is a Continental A75 with a metal prop.

There is nothing of note in the engine overhaul manual since that would generally be in the airframe manual. There is nothing in the Flybaby plans about it..a lot of the engine decisions are up to the builder.

I imagine the most reasonable thing would be to check the airframe manual for a Piper Cub or something with the same engine...but I don't have access to such data.

Thoughts?
 
My shop won't re-use prop nuts. Not sure about your plane.

jesse said:
In order to remove my cracked exhaust from the Flybaby I had to remove the nose bowl to get to the number 4 cylinder. This meant the prop had to come off. I drew some lines with a pencil to ensure I could install it again the same way.

The prop was held on by lock nuts. What should these be torqued to during the reinstall? The engine is a Continental A75 with a metal prop.

There is nothing of note in the engine overhaul manual since that would generally be in the airframe manual. There is nothing in the Flybaby plans about it..a lot of the engine decisions are up to the builder.

I imagine the most reasonable thing would be to check the airframe manual for a Piper Cub or something with the same engine...but I don't have access to such data.

Thoughts?
Click to expand...
 
ATTACHING BOLT DIAMETER RECOMMENDED WRENCH TORQUE​
3/8 inch 23 to 25 lb-ft (280 to 300 lb-in)
(31.6 to 33.9 newton-meters)
7/16 inch 40 to 45 lb-ft (480 to 540 lb-in)
(54.2 to 61.0 newton-meters)
1/2 inch 60 to 65 lb-ft (720 to 780 lb-in)
(81.3 to 88.1 newton-meters)​
This from the Sensenich web site
 
wabower said:
My shop won't re-use prop nuts. Not sure about your plane.
Click to expand...

Curious, what does not reusing mean. Since I have a wooden prop, the nuts have to be re-torqued regularly. It would be pretty expensive to change them each time. MT prop, they come from Germany and are apparently made of specially treated platinum:wink2:. I re-torque every 25 hours after the first 10.

Edit: Ok I do know what not reusing means. The question is e circumstances do you not reuse.
 
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Dunno. I have a bag-full of nuts that have been removed if you need them.

ebetancourt said:
Curious, what does not reusing mean. Since I have a wooden prop, the nuts have to be re-torqued regularly. It would be pretty expensive to change them each time. MT prop, they come from Germany and are apparently made of specially treated platinum:wink2:. I re-torque every 25 hours after the first 10.
Click to expand...
 
pmanton said:
ATTACHING BOLT DIAMETER RECOMMENDED WRENCH TORQUE​
3/8 inch 23 to 25 lb-ft (280 to 300 lb-in)
(31.6 to 33.9 newton-meters)
7/16 inch 40 to 45 lb-ft (480 to 540 lb-in)
(54.2 to 61.0 newton-meters)
1/2 inch 60 to 65 lb-ft (720 to 780 lb-in)
(81.3 to 88.1 newton-meters)​
This from the Sensenich web site
Click to expand...

These specs will be fine Jesse.

Just look at the nuts and see if they are used and abused, replace them as needed. Typically, replace them after 3-6 times. Rechecking torque doesn't count. Check torque once a year on a metal prop.

It's experimental. You can do what you think is best.
 
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ebetancourt said:
Edit: Ok I do know what not reusing means. The question is e circumstances do you not reuse.
Click to expand...

There's a heck of a difference between continuing to torque a lock nut and backing off a lock nut and then re-using...
 
I typically do not reuse fiber locking nuts, but will reuse a steel locking nut after 1 or 2 removal and reinstalls.
 
If there is no direct reference then use standard torquing procedures for the size nuts. AC43.13 should help u.


Sent from my iPad using Tapatalk HD
 
I would like to know what prop you have and the type of hub and nuts, show pictures if you can.

Does your prop come off with the hub attached?

or does it attach to the crank flange, by bolts thru the flange?
 
Also, may same nit picky but the first thing you learn in A&P school is that you never use a pencil to mark things on an airplane. :yikes:
 
I think Sensenich will have recommended torque values for your specific prop. They vary depending on the bolt size you are using. For my wood prop & A-75 it is 200 inch-lbs...a metal prop will vary significantly from wood.

Fiber locking nuts are the ones you want to replace periodically. The locking material loses its properties over time or with repeated removal.

Also, if you use fiber locking nuts, be sure to add the fiber drag to your torque value. With AN6 (3/8") bolts on my prop, fiber nuts add nearly 50 inch*lbs.
 
Tom-D said:
I would like to know what prop you have and the type of hub and nuts, show pictures if you can.
Click to expand...
Here is some info on the Prop, receipt of when it was last worked on:
http://i.imgur.com/HCgCA.jpg

I don't have a picture of the nuts but will take some tomorrow.

Tom-D said:
Does your prop come off with the hub attached?

or does it attach to the crank flange, by bolts thru the flange?
Click to expand...
Picture:
66361_3794393539784_1589030453_n.jpg
 
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Silvaire said:
Also, may same nit picky but the first thing you learn in A&P school is that you never use a pencil to mark things on an airplane. :yikes:
Click to expand...
Could you please educate me as to why?
 
If I could not prove the age of the prop bolts and nuts I would order new ones and use the torque given by McCauley,
Sensenich uses a bolt they have given a special part number.

most E-AB I see have a grade use an AN 174A- XX and AN 363 nuts.

Your prop is metal, so it does not require retorquing at a set period, torque it right and check it at 10 hours and for get it.
 
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jesse said:
Could you please educate me as to why?
Click to expand...

Something about graphite getting into micro-crevices in the aluminum, impossible to clean off and facilitating corrosion. It's been awhile but I think that was the gist of it. All I know is that they made a big point of it, enough so that you'll never see an A&P marking stuff on an airplane with a lead pencil. we all use Sharpies. :)
 
Silvaire said:
Something about graphite getting into micro-crevices in the aluminum, impossible to clean off and facilitating corrosion. It's been awhile but I think that was the gist of it. All I know is that they made a big point of it, enough so that you'll never see an A&P marking stuff on an airplane with a lead pencil. we all use Sharpies. :)
Click to expand...
I see. I suspect you'd need something else to interact with the graphite for it to corrode and also suspect that it's mostly theory than an actual problem. I've made many pencil marks on aluminum over the years and cleaned it off later without issue.

That said..I'll use something else in the future..I suppose that explains why half the airplane seems like it's covered in Sharpie marks :)
 
jesse said:
I see. I suspect you'd need something else to interact with the graphite for it to corrode and also suspect that it's mostly theory than an actual problem. I've made many pencil marks on aluminum over the years and cleaned it off later without issue.

That said..I'll use something else in the future..I suppose that explains why half the airplane seems like it's covered in Sharpie marks :)
Click to expand...
Theory maybe, but here is where it comes from. I suppose there is something behind it. FWIW.

AC 43.13-1B, ACCEPTABLE METHODS,
TECHNIQUES, AND PRACTICES - AIRCRAFT
INSPECTION AND REPAIR.
Section 6, Para 6-91.
c. Do not mark on any metal surface with
a graphite pencil or any type of sharp, pointed
instrument. Temporary markings (defined as
markings soluble in water or methyl chloroform)
should be used for metal layout work or
marking on the aircraft to indicate corroded areas.

d. Graphite should not be used as a lubricant
for any component. Graphite is cathodic
to all structural metals and will generate
galvanic corrosion in the presence of moisture,
especially if the graphite is applied in dry
form.

This Caution is in para 8-49, referring to marking on exhaust components:

CAUTION: Marking of exhaust system
parts. Never use lead pencils,
carbon based pencils, etc., to mark
exhaust system parts. Carbon deposited
by those tools will cause cracks
from heat concentration and carbonization
of the metal. If exhaust system
parts must be marked, use chalk,
Prussian blue, India ink, or a grease
pencil that is carbon-free.
 
jesse said:
I see. I suspect you'd need something else to interact with the graphite for it to corrode and also suspect that it's mostly theory than an actual problem. I've made many pencil marks on aluminum over the years and cleaned it off later without issue.

That said..I'll use something else in the future..I suppose that explains why half the airplane seems like it's covered in Sharpie marks :)
Click to expand...

nah the rest of the airplane is covered in sharpie because that is all Matt had handy at the time.
 
Silvaire said:
Something about graphite getting into micro-crevices in the aluminum, impossible to clean off and facilitating corrosion. It's been awhile but I think that was the gist of it. All I know is that they made a big point of it, enough so that you'll never see an A&P marking stuff on an airplane with a lead pencil. we all use Sharpies. :)
Click to expand...

no, it is an old wives tale, because the old pencils were lead. left over from the olden days long gone.

Sharp pointed scribes will leave a scratch that will become a stress riser.
 
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flyingmoose said:
Theory maybe, but here is where it comes from. I suppose there is something behind it. FWIW.

AC 43.13-1B, ACCEPTABLE METHODS,
TECHNIQUES, AND PRACTICES - AIRCRAFT
INSPECTION AND REPAIR.
Section 6, Para 6-91.
c. Do not mark on any metal surface with
a graphite pencil or any type of sharp, pointed
instrument. Temporary markings (defined as
markings soluble in water or methyl chloroform)
should be used for metal layout work or
marking on the aircraft to indicate corroded areas.

d. Graphite should not be used as a lubricant
for any component. Graphite is cathodic
to all structural metals and will generate
galvanic corrosion in the presence of moisture,
especially if the graphite is applied in dry
form.

One must remember how the AC became what it is. The FAA put out the word for every one to place their inputs, and that information became the AC.

much of the input came from material written in the 30s.
This Caution is in para 8-49, referring to marking on exhaust components:

CAUTION: Marking of exhaust system
parts. Never use lead pencils,
carbon based pencils, etc., to mark
exhaust system parts. Carbon deposited
by those tools will cause cracks
from heat concentration and carbonization
of the metal. If exhaust system
parts must be marked, use chalk,
Prussian blue, India ink, or a grease
pencil that is carbon-free.
Click to expand...

In order to make any change in material that would result in a crack, you would be required to raise the temp to critical temp of the metal, doing that would require temps higher than developed in the fuel burning process.

It is a good theory, but in practical every day usage of exhaust systems it doesn't matter.
 
. . . and cut it with a chain saw.
 
Tom-D said:
no, it is an old wives tale, because the old pencils were lead. left over from the olden days long gone.
Click to expand...

I had no idea old wives were writing the FAA Advisory Circulars. :lol:
 
22 years of turning wrenches in the field of Naval Aviation. Never use a lead/graphite pencil to mark anything on a aircraft. Never scrath a line, causes stress risers cuausing cracks. Never re-use any self locking Nuts/Bolts.
 
A threaded fastener that has been torqued to its limit will have some of the threads loaded to plastic deformation. That is the source of the requirement not to reuse bolts and nuts. The application may not call for being torqued to the limit of the fastener. The load is not uniform on the threads. The threads closer to the loaded part of the bolt are more heavily loaded.
 
P3CNTRSEAT said:
22 years of turning wrenches in the field of Naval Aviation. Never use a lead/graphite pencil to mark anything on a aircraft. Never scrath a line, causes stress risers cuausing cracks. Never re-use any self locking Nuts/Bolts.
Click to expand...

you never paid the bills either.
 
Tom-D said:
no, it is an old wives tale, because the old pencils were lead. left over from the olden days long gone.

Sharp pointed scribes will leave a scratch that will become a stress riser.
Click to expand...

Modern pencils are graphite based, graphite is the concern because it can react with metals and prevent corrosion treatments (eg alodine) from properly adhering to the metal. When I worked for Beachcraft you would be chased out of he assembly line if you were just carrying a pencil.
 
jrollf said:
Modern pencils are graphite based, graphite is the concern because it can react with metals and prevent corrosion treatments (eg alodine) from properly adhering to the metal. When I worked for Beachcraft you would be chased out of he assembly line if you were just carrying a pencil.
Click to expand...

Yep, that's why we use so much Graphite lube, like mollyB greases.

Beech makes the major portion of their aircraft from Magnesium, you don't use alodine on MAG.
 
For future reference Jesse, I don't think you even have to remove the nuts and bolts to remove that prop. That engine has a taper shaft crank and the entire prop hub can be removed without unbolting the prop. It's a pretty slick deal. Some old timer around there can show you how.
 
jrollf said:
Modern pencils are graphite based, graphite is the concern because it can react with metals and prevent corrosion treatments (eg alodine) from properly adhering to the metal. When I worked for Beachcraft you would be chased out of he assembly line if you were just carrying a pencil.
Click to expand...

Is that Beechcraft's boat manufacturing branch?

Sent via teletype
 
wby0nder said:
For future reference Jesse, I don't think you even have to remove the nuts and bolts to remove that prop. That engine has a taper shaft crank and the entire prop hub can be removed without unbolting the prop. It's a pretty slick deal. Some old timer around there can show you how.
Click to expand...

oh sure, NOW you tell him
 
Tom-D said:
Yep, that's why we use so much Graphite lube, like mollyB greases.
Click to expand...

Molybdenum and graphite are two different things. Graphite is just carbon (element number 6 on the periodic table) and Moly is 42, a metal. Molybdenum disulfide is what we find in Moly greases, not carbon.

Dan
 
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wby0nder said:
For future reference Jesse, I don't think you even have to remove the nuts and bolts to remove that prop. That engine has a taper shaft crank and the entire prop hub can be removed without unbolting the prop. It's a pretty slick deal. Some old timer around there can show you how.
Click to expand...

It can be a bear to get it off. The hub's taper wedges really tightly onto the crank. You take out a small screw and nut in the front of the hub (it's the safety to prevent the big nut from coming loose), and put a stout bar through the holes in the nut and back it off. Then you keep turning it until the nut's inside flange comes up against the fat square-section snap ring inside the hub's front bore, and further turning of the nut should pop the hub loose from the crank.

But if it's been on there a long time, it will want to stay there.

Dan
 
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