George Lendich wrote:

. One other question I have is. If titanium is not the material to use

what

is ?

                      Respectfully, Tony

Good question. One of the steels obviously. Starting with 4130 heat

treated,

shot peened and rolled threads.  Perhaps 4130 is not optimum. Also

you

want

to make a distinction between a bolt and a stud. A bolt has exposed

threads

unlike a properly installed stud. Makes a difference if you are

putting

a bending load on the stud or bolt. The bending loads come from

the long

bolt vibrating in the over size housing bores.

Paul Lamar

Paul,
I guess I will have to look at this for my single rotor, so this

discussion

is timely for me.
So I would be happy if someone told me what the current bolts are

made of,

and what characteristics I have to look for.

Perhaps 4340 might be a good material,s it is extremely tough.
George ( down under)

I am not sure I understand the reasons why titanium is not good. Unlike
aluminum It has decent fatigue strength.
6-4 titanium alloy  it is almost as strong as 4130 at ~50% weight.  The
only bad feature discussed in literature is bad friction property,
titanium parts freeze very easy. But there is no motion in these bolts.
Could  someone discuss the issue deeper?

Jerzy

According to Vance (retired rocket scientist.) titanium is notch sensitive.
In other words a crack could start at the base of the threads and you would
have no way of detection it without disassembling the engine.

Paul Lamar

Doug Mueller wrote:

Paul,
What Vance failed to mention was that the notching requires 210,000psi with
the Titanium used. In order to notch this material that these studs are made
of, a stress could be incurred but Highly unlikely. Vance also did not mention
that there is 32 different types of titanium. The material used is quite strong.
I made the same recommendation to Tony as Paul did. He is giving a set to
MazdaTrix to try in their car. Their complaint of breaking bolts after a race
would be the perfect test bed and cheapest insurance policy to verify the
integrity of these things. These bolts may not be cost effective to most.
Production costs will cause a set of these things to come to close to $450. FYI
Doug Mueller
RX-6 13BT
N900DM
Boulder CIty, NV

The stock tension bolts average $18 each and there are 18 for a total of $324.

Paul Lamar
 
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