Prop Bolts

PB · Post by PB » Fri Mar 21, 2008 11:34 am

The definitive text on all things nuts-and-bolts is usually regarded as, “An introduction to the design and behaviour of bolted joints” by John H Bickford.

At just shy of 1000 pages it’s not exactly light reading. Even in this book, the author regularly states that industry best-practice often remains the best guide and that exact science is not always available.

There is lots of surprising stuff, for example, how poor even calibrated torque wrenches are at setting bolt tensions. In the context of aircraft industry practice, the one really big surprise is the author’s view that locking-wire is really only any use to stop nuts and bolts falling out once they have become loose.

Rob Swain · Post by **Rob Swain** » Thu Mar 27, 2008 12:01 pm

PB wrote:the one really big surprise is the author’s view that locking-wire is really only any use to stop nuts and bolts falling out once they have become loose.

I have to say I am not surprised by this.

I've never had any bolt ever come undone in service on any car or motorcycle I've ever owned. Often the cursing from the garage is because of bolts / screws that should come undone that don't!

I'll still be wirelocking my prop bolts though.

Jonathan Wilkins · Post by **Jonathan Wilkins** » Thu Mar 27, 2008 10:33 pm

Hi guys, sorry for not replying to all your very useful advice. Actually just reading through your comments especially those of "PB" i feel much more in the picture and am realising that owning an aeroplane is quite an exciting learning curve.
As for the bolts........Robin Aircraft at Dijon have come to the rescue, having exactly the correct dimention 8.8 metric bolts which should be with me in a couple of days, thanks to our Robin experts here at Headcorn.

Trevor Lyons · Post by **Trevor Lyons** » Sat Aug 30, 2008 8:11 pm

FWB Products Ltd of Whieldon Road, Stoke-on-Trent, ST4 4JE, have in stock almost any fixing you can think off, and they're cheap.
(Yesterday, I bought 8 Allen headed H-T bolts of 12.9DIN for £2.15!)

FWB's contact details: Tel : +44 (0)1782 744333 | Fax : +44 (0)1782 744577 | [email protected]

See also: http://home.jtan.com/~joe/KIAT/kiat_2.htm

Jonathan Wilkins · Post by **Jonathan Wilkins** » Sat Aug 30, 2008 10:50 pm

Thanks for that, it keep that info for future reference.

Charles E Taylor · Post by **Charles E Taylor** » Tue Sep 09, 2008 1:17 pm

Hello

For further reference and interesting background.

http://www.arp-bolts.com/Tech/Tech.html

Charlie

Matt Dovey · Post by **Matt Dovey** » Sun Oct 26, 2008 8:13 pm

Just as an aside.You guys probably know this any way.As an apprentice I was tought that 1.5 threads should be showing through any nut,insert or fastening device in the aviation industry.1.5 thread general good practice.In the states they use 1 thread as stated in AC43.13-1B.
Have seen a fair few props fitted with the incorrect AN bolts.When a standard AN bolt is fitted the thread is about 1/8 inch below the end of the threaded insert on the prop boss(Lycoming engines).The correct length prop bolts have a longer thread and therefore protrud through the insert the correct amount.
Also have seen a few bolts with the only thing keeping them in postion is the wire locking.A couple of sump plugs to.Which was worrying.