Prop question

[allen]

Getting familiar with my new plane and trying to learn everything that I can about it. According to the logs I have a Great American propeller hanging off the back. It's a 64x72. I would like to learn more about it, I cannot find a website on Great American. In a few hours I’m heading down to the hanger to change the oil. While I’m there I want to retorq all of the prop bolts since I moved the plane from Florida to Virginia and there is a big change in humidity. I need to know the correct torq values.

Who makes my prop and where can I go to read more about it and the company?

The previous owner of this plane had had two incidences’ of cowling fasteners getting loose and hitting the prop. He sent it off to Velocity to repair, balance and paint. They also placed a leading edge fiberglass covering on the prop to protect against future fights with all things hard. So far I have not had any issues with this prop; seems tough as nails and I cruise at about 155-160kts without pants turning 2450-2500 rpm, so no complaints. Just want to learn.

Also, any recommendations about removing the spinner and getting it back on exactly right would be most helpful.  :wink:

[Drew]

This may work for you:

http://www.sensenichprop.com/sen_html/aircraft_cet/install/cf-a.pdf

[GlennBob]

Thanks Drew,

This is some info that many including myself may find helpful ! !

Glennbob

[allen]

Thanks Drew,

   Perfect timing too. I had the spinner off when I read this. The guys ar Velocity had torq'd the prop to about 300 inch pounds. About 100 over. There were some signs of damage to the hub. Small cracks about the size of a hair were in the paint radiating out from the hub about 5cm. The prop itself looks good though.

    We moved the transducer for the EI Oil temp/pressure gauge. It had been located in a position that had the oil line going to it completely stretched and under tension. We relocated it to the fire wall and replaced the oil line since the old one showed since of damage.

   Last night I tok it up in the pattern to do a shake down flight. I noticed that under full power after a random amount of time my oil pressure would indicate a drop from 80ish down to 40. If I pull back poser for a second or so the pressure would come right back. Advance the throttle to 100% again and the pressure would remain at 80. After a few minutes, it would drop again.

    This would only happen at full throttle, and it is random as to time. But it does return to full pressure again after I retard the throttle about 500rmp.

   I'm off to the airport right now to do a little investigating.

[Drew]

mmm.  300ish seems about right.  What size AN bolts do you have?

Also---there are some material differences where people use different torque settings.  If you can find the manufacturer specs, that would be better.

Take a look at the Saber sight (prop extensions)----they have good info too.  Make sure that your crush plate is properly sized for your engine size.  The friction of the crush plate on the hub is what is holding your prop on.  If it gets too loose, it will shear the bolts.

Only use the special bolts made for props----very expensive---and worth it.  Don't use AN bolts of the same size that are not meant for props.

My prop (Prince) has the torque printed on the hub.

[allen]

According to the site you gave me the recommended torq is between 175 and 225 for an AN-6. We compared an AN-5 and AN-7 bolt to the ones in my prop just to be certain. I feel confident that it is an AN-6. Based on that we re-torq’d all of the bolts according to table 1 and safety wired them. Naturally I’ll be pulling the spinner within the first few hours to confirm that everything is cool. Plus I need to put a cork in the hub. I want to shoot a touch of paint as well just to seal up those tiny cracks. I photographed them for later comparison. This way I can have definitive proof that they are not advancing.

I spoke with my A&P this morning about the iol pressure issue. He feels that the transducer is to blame. A local MD has an RV6 that Jeff recently put EI gauges in and he is running the same E.I OPT-1 guage that I am. Jeff said that the RV has had 2 transducers fail, but those were attributed to how they were mounted. (i.e right on the motor, then on the motor mount. Both no-no’s. Mine was on the motor mount as well.)
This morning I’ll give the guys at EI a call and talk it over with them. A new transducer runs $165. Bummer, but well worth it if its really the issue here.

[LongEZDaveA]

My first prop was a Great American and they specified a max torque of 300 in-lbs for the multi-laminate props only.

I'm not aware of "prop bolts" being anything different than standard aircraft bolts.  Please note that I'm not arguing - I just don't remember hearing of that before.  What is different?

[Drew]

From Saber:

While the bolts we stock are not "aircraft-certified", they have been appoved for use on certain FAA certified aircraft. They have superior toughness and ductility compared to the standard AN aircraft bolts. They are machined to close tolerances, and heat treated under strict control so that their high tensile strength does not result in brittleness.  AN bolt tensile strength is 125kips and our bolts are 180kips.  Over 20,000 of these have been in use on experimental and certified aircraft for the past 20  years with a perfect safety record.  The heads are single-drilled if required by your application.

Most importantly, these engine and prop bolts have a shorter grip and a LONGER THREAD, which provide a much greater safety margin against bottoming out the threads. This is critical because each time you re-torque your wooden PROPELLER, you may use up more of the available thread, and risk bottoming out the bolt prior to achieving proper grip between the extension face and prop face. This is also important because some engine models have lugs installed which have unusually long thread length which can allow a standard bolt to bottom out prior to reaching proper extension face to engine face grip.

[Bruce Hughes]

Hi Group

I was not aware of Saber's claim about superior bolts.   If I
had been, I would have ordered from Saber.   I am now using
AN76 bolts from Aircraft Spruce.

Read VERY CAREFULLY the Saber claim of longer treads.   That
feature is VERY important.   I damaged a O-235 by torquing to
the point where the shoulder hit the threads.   One more turn
and the threaded propeller insert started turning on the
propeller flange.   You cannot get the bolt out without a special
tool.   And you cannot put in bolts or torque bolts without a
special tool.   VERY serious problem.

The ONLY way to fix it is to put in an oversize insert.   I do not
have the equipment to do that.  I want to sell the engine as I
now have a O-320.   However NOBODY is going to buy it until
the insert problem is fixed.

It is POSSIBLE to rent a tool for putting in inserts.    I did
that (converting the SAE #1 engine to a SAE #2) before I created
the problem but those were standard sized inserts.   I do not
know if I could have done that with an oversized insert.

BEWARE.    

Bruce Hughes

[robert mencl]

Hi Bruce, I put my insert nuts in the crank flange by freezing and greasing them, and sucked them in with a long thread 5/16" bolt and impact wrench, with a half inch drive socket over the outboard end of the insert. (there is no stres on the crank) I have had good success with nuts that spin by knurling them with a cold chisel, and epoxying into crank flange. Good luck, R.

[srothert]

Allen,
I have an 0-320, 160 HP Lycoming on my Long-Ez and have a Great American prop that I bought new and currently use as backup.  I bought it new many years ago.  Great American is long gone.  You need to determine whether you have the 3/8 or the 7/16 inch diameter prop bolts. The documentation I have from Great American says to torque the bolts as follows

3/8"  240 in lbs
7/16"  420 in lbs

I live in northern Virginia and you can give me a call if you have any questions 703-698-9576

Steve Rothert

[rglos]

Whoa Whoa, slowdown a minute

The Great American prop had multiple laminations and would take the extra torque.

It is not the bolt size that determines the torque, remember you are tightening against wood, not steel.

I have two props as well. On the Great American I tighten to 25 ft/lbs.
I also have a prop with only six laminations. This, I tighten to 18 ft/lbs.
Any more and you will start to crush the wood.

Do this in 5 ft/lb increments and lube the threads with wax. Make sure the bolt turns easily in the bolt hole.

Great American said no more than 300 in/lbs, no matter what the diameter of the bolt is.

[b-dog]

Check with Beagle, (David Orr)
He has a great DVD on Great American Props.
Shows Install and Torque. Cheap investment!

Bill