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#1
10-27-2009, 05:48 PM
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Spindle bolt torque
I am finding conflicting numbers for the (dry) torque value on my grade 8, fine thread spindle bolt. Also some have suggested using a grade 8 mechanical locking nut instead of the typical castle nut / cotter pin. Can anyone with experience advise me, as the 'search' function has been little help. Thanks, Mike.
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" Amaze Your Friends, Annoy Your Neighbors" 
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#3
10-28-2009, 06:03 AM
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Grant, my hardware was purchased from East Coast Aircraft Supply, with paperwork.
AN-8. There seems to be some conflict on past threads regarding the proper grade bolt for the spindle. My spindle bolt is a specific grip length, and was only available special order from ECAS. My rotor head is a Parsons.
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" Amaze Your Friends, Annoy Your Neighbors"
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#4
10-28-2009, 06:48 AM
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Mike Dad uses grade 8 bolt and a grade 8 nylock nut. He replaces the nut about once a year. Not sure what torque should be but, I can check.
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"You can try to educate the ignorant but, you can't argue with stupid" Mike Boyette Recreational Pilot Gyroplane Sunstate Wing & Rotor Board Member Pra Member #46553
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#5
10-28-2009, 06:52 AM
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Hey Mike, I would sure appreciate that torque spec, thank you. I read his thoughts regarding the nut, and took his advice. Interesting service interval. Mike H.
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" Amaze Your Friends, Annoy Your Neighbors"
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#6
10-28-2009, 08:22 AM
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Thats the first I've heard that you should change the spindle bolt nut once a year on a Dom? The estimated yield strengh of a grade 8 , 1/2 inch. bolt is about 19,000 lbs. Breaking strength is about 24,000 lbs.
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Edypaul Last edited by edypaul; 10-28-2009 at 08:29 AM.
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#8
10-28-2009, 11:43 AM
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Shirley, thats where part of the confusion is. My understanding is that AN hardware is graded differently than SAE. The AN-8, is roughly a grade 5 in SAE terms. Obviously the
-8 is the diameter in 16/ths. I think Ernie uses GRADE 8 on his machines, which is overkill as previously stated. THEN, there are other differences beyond me, like ductility, hardness etc. 
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" Amaze Your Friends, Annoy Your Neighbors"
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#9
10-28-2009, 11:44 AM
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Oh yah, I am still looking for the proper torque for this rascal...
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" Amaze Your Friends, Annoy Your Neighbors"
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#10
10-28-2009, 12:07 PM
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Grade 8 bolts have a spec sheet min tensile strength of 150,000 psi. AN8 (aircraft) bolts have a min tensile strength of 125,000 psi. The kicker is in the manufacturing process. Grade 8 bolts (may) have cut threads with a Class 2 fit. AN bolts WILL have rolled threads with a tighter (Class 3) fit, so the bolt/nut assembly of the AN bolt is stronger in tension, which is how a spindle bolt is loaded. In other words, the nut may pull off of a Grade 8 bolt easier than off of an aircraft quality bolt, even though the Grade 8 bolt is (maybe) stronger. Quality control is (presumably) higher in an aircraft bolt. AN8 twenty thread/inch bolts are torqued to 480 to 690 inch pounds, according to the Aircraft Mechanic's Handbook. All this information can be found on the web (that's where I got it!) I use AN bolts an all critical applications, and I consider the spindle bolt somewhat critical (DUH!) Also, if you are concerned about the torque changing in use, the MS17825 nut is a castellated nut with a fiber locking insert, which gives double safety, sorta like wearing a belt AND suspenders.
Dr. Rob Last edited by docrob; 10-29-2009 at 01:18 PM.
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#11
10-28-2009, 12:18 PM
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On the single seat Dominator, if the spindle bolt is the passes through the hub bar bearing and is an AN8-31, the torque is 480 to 690 inch pounds.
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#13
10-28-2009, 12:34 PM
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Quote:
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Pete Johnson
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