structural aircraft Mech or A&P HELP!

Bhunt

Member
Note: this is a repost I put it in the case forum but I'm more likely to find someone here who can help me sub a part.
Trying to find the flywheel bolts part # 08530AB it a 7/16-20 bolt its interference fit. Bolt Diameter is.435-.436 same as an aircraft bolt or Hiloc. I followed the torque specs in the Manual it says torque flywheel nuts 50 foot pounds the book is WRONG stripped at least 3. I thought the bolt was turning in the crankshaft went to hold it with a wrench and it wasn't moving. I need to replace them all. I checked the torque by bolt Diameter torque should have been closer to 36 ft lb . I used a 1/2 snap-on torque wrench not a cheep one. I need to find a place to get 6 replacement bolts and nuts. New used whatever any help would be appreciated. Any input would be welcome as well. Heres a link to the bolts
http://partstore.caseih.com/us/parts-search.html#epc::mr66945ar131481

STRUCTURAL AIRCRAFT GUYS question what Nas bolt can I sub for this or is there a better sub? I cant use the high head 12 point bolt not enough room the bearing carrier is in the way it's a 14 dia bolt grip length is 13. They may just have 7/16-24 which would be ok
I dont have access to a manual Im retired maybe a Protruding head tension hilok titanium or steel would more than likely be ok with a tension nut I need the greatest tension and shear strength. Any help would be appreciated. what I really need is a part number.
Thanks Byron
 
I don't think your flywheel bolts are grade 2, they should be grade 8, or better. If the bolts you had were grade two, there's no wonder they stripped out. That said, your right in that a 7/16 grade 2 bolt shows a max torque of 24 ftlbs, but the grade 8 is 58 ftlbs.

I notice you mention a standard size 7/16, but also talk about 13 and 14 like your talking about something metric. Could it be someone tried to use metric bolts in a standard hole? There are many standard sizes that will screw into metric threaded holes, and 'feel good' until you try to tighten them.

In any case, insure your size 100% and then hat said, check out McMaster Carr to find the bolts you need. They should have whatever you need, be it standard, metric, flange head, 12pt, locking, etc, etc. .
Torque chart

McMaster Carr
 
NAS bolts are difficult to come by. AN bolts are 125,000 psi tensile strength and readily available from Aircraft Spruce or Wicks.
 
(quoted from post at 05:23:42 10/10/16) I don't think your flywheel bolts are grade 2, they should be grade 8, or better. If the bolts you had were grade two, there's no wonder they stripped out. That said, your right in that a 7/16 grade 2 bolt shows a max torque of 24 ftlbs, but the grade 8 is 58 ftlbs.

I notice you mention a standard size 7/16, but also talk about 13 and 14 like your talking about something metric. Could it be someone tried to use metric bolts in a standard hole? There are many standard sizes that will screw into metric threaded holes, and 'feel good' until you try to tighten them.

In any case, insure your size 100% and then hat said, check out McMaster Carr to find the bolts you need. They should have whatever you need, be it standard, metric, flange head, 12pt, locking, etc, etc. .
Torque chart

McMaster Carr

No telling what bolts were in there no numbers on them but because of there unique makeup & Design I believe them to be original. A standard 7/16 grade 8 bolt is .429 diameter and would be to small for an interference fit hole hence the note to aircraft mechs. Aircraft fasteners are a little bigger Dia. Now the 14 I spoke of is the diameter of the bolt or Hi loc in 32nds 14/32 is .4375 or 7/16 it is aircraft terminology for fasteners so you may have a Hi loc part number that is
(HL20 14-13) HL 20 is the head and makeup Design, 14 is the Dia. and 13 is the grip length in 32nds of an inch that is the length of the shank only not counting the threads.

I do appreciate you taking the time to help .
Thanks Byron
 
Thanks Ill check it out I know they should have it in 7/16-20 if I remember right the thread length on those is a little longer than normal aircraft bolts Ill give em a call on it
Thanks for your time Byron
 
I agree with Mark, check with Aircraft Spruce. The wing mount bolts on my Piper Cherokee are interference bolts. When I worked on it, I got some new ones from Aircraft Spruce. At the time, I had all those letters and numbers in my head, now its all gone! All I can recall is that they are nominally 3/8" bolts.
 
Why worry about an interference fit on a flywheel bolt? I've built several dozen engines over the years, from those in skidsteers to a big one in a D9 CAT, and I have never seen a diesel engine, used in a piece of machinery, built with 'special' clearance fasteners on the flywheels. Granted they might be an odd thread length, odd shoulder length, etc, but even then I've seen factory bolts replaced with 'regular' ones many times over. Beyond the absolute need, by design, for something special like an oversized shoulder, undersized head, etc there should be no need for anything to be special about the thread engagement as long as they stay in the hole. To facilitate that, insure they are of at least a grade 8, are of the correct length, or a length that will work, and install them with a drop of two of red Loc-Tite. This will work just fine for a flywheel bolt whether it's an interference fit or not.
 
Your flywheel is attached with studs and fine thread nuts. The torque on the nuts should be 51#ft. Your nuts were the wrong ones.
You are working on an old pre 50s tractor, they wern't that precise back then, and I doubt that you plan on turning 4000rs with this motor.
a239745.jpg

a239746.jpg
 

It a 52 and you may be spot on with the nuts they were a thinner lower case nut fine thread 7/16 20 but that's what I took off it. The fine thread should be stronger but your Probably right the thin nuts could not take the torque. Here's a pic of the bolts and nuts.
41277.jpg
41281.jpg
41282.jpg


Thanks Loren I think you nailed it
 

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