Torque Specifications
Posted: Fri Feb 17, 2012 5:39 pm
Hello Ian, I retrieved your question from the archives. Are you sending to the right address?, as not coming out as e-mail to the list!
I have built 9 Rebel wings ( the last one this past spring, with a new wing kit from Murphy) and have never seen a 1/4" bolt holding the spar caps in place! (The only 1/4 inch bolts in a Rebel wing are the 4 holding the front wing attach fitting to the front spar and the 4 that hold the wing strut attach fitting to the main spar.) These bolts should all be AN3 (3/16th) and you will find that you need a washer under the head and 2 under the nut on most of them to keep the nut from "shouldering"on the shank. Next size shorter bolts are to short. Torque Values for AN3 - 125,000 psi fine thread bolts are 20 to 25 inch-lbs. Note this is only 1.6 to 2.08 foot lbs!!!! Torque a few with the torque wrench and then using a 1/4" drive ratchet, get a feel for how much pressure it takes to turn the nut beyond the torque value. WHILE HOLDING THE HEAD OF THE RATCHET! Not the handle!!! Then you can do the rest with the ratchet or you can take the time to do them all with the torque wrench. As always, its your choice. For reference, fine thread 1/4" bolts are torqued to 50 to 70 in-lbs, 5/16 fine thread are torqued 100 to 140 in-lbs. and 3/8 fine thread are torqued 160 to 190 in-lbs.
When you get to the engine installation you will find 7/16 fine thread bolts and they jump to 450 to 500 in-lbs (37.5 to 41.6 ft-lbs.) and possibly 1/2 fine thread (O-360 prop bolts) and they are torqued 480 to 690 in-lbs.(40 to 57.5 ft-lbs).
I'm hoping that you just asked about the wrong size bolt and have actually drilled your spar caps 3/16th. If not please contact Murphy Technical Dept. to determine if the line of 1/4 inch holes versus 3/16 holes will weaken the main spar. I suspect it won't but the larger bolts will definetly add weight!
Hope this helps you out,
Wayne G. O'Shea
www.irishfield.on.ca
I have built 9 Rebel wings ( the last one this past spring, with a new wing kit from Murphy) and have never seen a 1/4" bolt holding the spar caps in place! (The only 1/4 inch bolts in a Rebel wing are the 4 holding the front wing attach fitting to the front spar and the 4 that hold the wing strut attach fitting to the main spar.) These bolts should all be AN3 (3/16th) and you will find that you need a washer under the head and 2 under the nut on most of them to keep the nut from "shouldering"on the shank. Next size shorter bolts are to short. Torque Values for AN3 - 125,000 psi fine thread bolts are 20 to 25 inch-lbs. Note this is only 1.6 to 2.08 foot lbs!!!! Torque a few with the torque wrench and then using a 1/4" drive ratchet, get a feel for how much pressure it takes to turn the nut beyond the torque value. WHILE HOLDING THE HEAD OF THE RATCHET! Not the handle!!! Then you can do the rest with the ratchet or you can take the time to do them all with the torque wrench. As always, its your choice. For reference, fine thread 1/4" bolts are torqued to 50 to 70 in-lbs, 5/16 fine thread are torqued 100 to 140 in-lbs. and 3/8 fine thread are torqued 160 to 190 in-lbs.
When you get to the engine installation you will find 7/16 fine thread bolts and they jump to 450 to 500 in-lbs (37.5 to 41.6 ft-lbs.) and possibly 1/2 fine thread (O-360 prop bolts) and they are torqued 480 to 690 in-lbs.(40 to 57.5 ft-lbs).
I'm hoping that you just asked about the wrong size bolt and have actually drilled your spar caps 3/16th. If not please contact Murphy Technical Dept. to determine if the line of 1/4 inch holes versus 3/16 holes will weaken the main spar. I suspect it won't but the larger bolts will definetly add weight!
Hope this helps you out,
Wayne G. O'Shea
www.irishfield.on.ca