Subject: [TR] Thanks for the help on Spit vertical link

From: Bud R <[email-masked]>
Date: Sat, 27 Sep 2014 11:00:08 -0600

List, thanks for all the help with questions about my Spitfire vertical link.
On my second try with a heli coil I got the caliper bolt to hold with the
recommended 65 ft/lbs of torque. The first time I followed the hell coil
instructions and counter sunk the hell coil just a bit. As it turns out the
caliper bolt need those few extra threads at the very top of the hole. I set
the hell coil at the top and there was enough threads to hold the needed
torque. I painted a red stripe on one flat of the bolt head/caliper to easily
check for any movement.

Dont know what got into me with reading and following the hell coil
instructions. That usually doesnt happen.

Love this list,
Bud Rolofson

Extreme Parts Racing (more than just a haircut)

71TR6 CC57365 (Good 6)
71 Spitfire MK IV Race Car #3
69 Spitfire MK III (back up FE engine/dinghy car)
93 Minnie Winnie Race Support Vehicle
77 Z-50A Hardly Davidson Honda Mini-Trail Bike (Triumph Pit Bike)

** [email-masked] **

Archive: http://www.team.net/archive

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From: "Randall" <[email-masked]>
Date: Sat, 27 Sep 2014 12:42:36 -0700

> recommended 65 ft/lbs of torque. 

Uhm, so what happens when you jump on the brakes for a panic stop and the force on the threads goes up?  The force on the caliper is
going to be somewhere around 1/3 to 1/2 the weight of the car.

Randall

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From: Me <[email-masked]>
Date: Sat, 27 Sep 2014 15:11:34 -0600

Most of the force will be shear force on the bolt not pull force on the
threads. That was how it was explained to me.

Sent from my iPad

> On Sep 27, 2014, at 1:42 PM, Randall <[email-masked]> wrote:
>
>
> Uhm, so what happens when you jump on the brakes for a panic stop and the
force on the threads goes up?  The force on the caliper is

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From: "Randall" <[email-masked]>
Date: Sat, 27 Sep 2014 14:36:41 -0700

> threads. That was how it was explained to me.

Quite true, the threads only get a fraction of the force.  How big is a fraction of a half ton?

Randall

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From: Me <[email-masked]>
Date: Sat, 27 Sep 2014 16:14:27 -0600

Apparently less than 65 ft/lbs.

Sent from my iPad

On Sep 27, 2014, at 3:36 PM, Randall <[email-masked]> wrote:

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From: "Randall" <[email-masked]>
Date: Sat, 27 Sep 2014 16:55:01 -0700

> Apparently less than 65 ft/lbs.

Ok, I'll buy that.  So the force nearly doubles during panic breaking.  Is your new joint twice as strong as the old one?

Randall

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From: Me <[email-masked]>
Date: Sat, 27 Sep 2014 20:18:12 -0600

I trust that Standard Triumph engineers designed brake systems and
specifications to include the possibility of panic braking. We should park
them if they didn't.

Bud

Sent from my iPad

> On Sep 27, 2014, at 5:55 PM, Randall <[email-masked]> wrote:
>
>
> Ok, I'll buy that.  So the force nearly doubles during panic breaking.  Is
your new joint twice as strong as the old one?

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From: "Randall" <[email-masked]>
Date: Sat, 27 Sep 2014 22:28:05 -0700

> specifications to include the possibility of panic braking. 

Well, perhaps I misunderstood.  They also did not design critical bolted joints such that missing one or two threads would cause
them to fail.  You posted 
"The first time I followed the hell coil
instructions and counter sunk the hell coil just a bit. As it turns out the
caliper bolt need those few extra threads at the very top of the hole.  As it turns out the caliper bolt need those few extra
threads at the very top of the hole."

I'm just suggesting that there might be something else going on, that's all.

Carry on,
Randall

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From: Me <[email-masked]>
Date: Sun, 28 Sep 2014 00:42:51 -0600

The important thing is if the bolt can be tightened to 65 ft/lbs. That's the
design spec with or without a heli coil. One way worked one didn't.

Unlike some I do like my car to be safe. I'm ok with the bolt at 65 ft/ lbs
with a heli coil.

Sent from my iPad

> On Sep 27, 2014, at 11:28 PM, Randall <[email-masked]> wrote:
>
>
> Well, perhaps I misunderstood.  They also did not design critical bolted
joints such that missing one or two threads would cause
> caliper bolt need those few extra threads at the very top of the hole.  As
it turns out the caliper bolt need those few extra

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From: "Randall" <[email-masked]>
Date: Sun, 28 Sep 2014 02:35:43 -0700

> The important thing is if the bolt can be tightened to 65 
> ft/lbs. 

I guess we all have our priorities.  Mine would be that the bolt not rip out when I pounce on the brakes.

Randall

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From: Bud R <[email-masked]>
Date: Sun, 28 Sep 2014 10:59:29 -0600

I dont understand why you think that would happen. Is there some information
about hell coils not working that youre not referencing?

Bud Rolofson

71TR6 CC57365 (Good 6)

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From: "Randall" <[email-masked]>
Date: Sun, 28 Sep 2014 10:50:11 -0700

> about hell coils not working that youre not referencing?

No, Heli-coils are fine.  But the joint should not have failed just because
you left out the last turn of Heli-coil (as directed).
There is likely something else going on.

My point is that the maximum stress on those threads is more than just the
initial 65 ftlb.  So just because it held when you
torqued the bolt down does not mean it will hold in service.

Randall

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From: Jeff Scarbrough <[email-masked]>
Date: Mon, 29 Sep 2014 10:04:48 -0400

On Sat, Sep 27, 2014 at 1:00 PM, Bud R <[email-masked]> wrote:
> The first time I followed the hell coil
> torque.

Unless the bolt is too short for some reason, I don't see how this
could be the case.  I would expect a Heli-Coil to work fine in any
application where it's installed according to directions.  The only
time I've had one fail is when the underlying material is too weak
(usually due to insufficient thread depth in the oversize hole), and
the insert pulls out under torque.  This doesn't sound like your case,
since you found that less insertion leads to a better joint.  Perhaps
it went all the way through the underlying piece the first time?

Bear in mind that most Heli-Coils of a given diameter come in several
different lengths...

Jeff Scarbrough
Corrosion Acres, Ga.