Subject: [Fot] TR4 crank

From: [email-masked]
Date: Wed, 2 May 2012 16:23:03 -0700 (PDT)

FOT,
I am having the engine in my TR4A race car rebuilt.  Are there any
alternatives 
to a billet crank?  We are looking for about 150hp (not a super
powerful 
170-190).
Thanks.
Western Eagle Racing/Ron Jacobs
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From: Joe Alexander <[email-masked]>
Date: Wed, 2 May 2012 20:20:41 -0400 (EDT)

We ran 19 years without having a broken crank.

Without any special preparation.

Now we have a billet crank, but only because we came into a 'cracked' billet
crank. I was going to make another end table out of. It sat unprotected on a
pallet in a storage shed for about 4 years, when I decided to get a 'second
opinion'.

It was pronounced 'good' AT TWO DIFFERENT MACHINE SHOPS.  Otherwise we would
still be running a stock crank.

Joe Alexander
A. R. E.
645 1st Street
Jesup, Iowa 50648
319.464.4711  (cell)
[email-masked]

-----Original Message-----
From: westerneagleracing <[email-masked]>
To: fot <[email-masked]>
Sent: Wed, May 2, 2012 6:52 pm
Subject: [Fot] TR4 crank

FOT,

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From: Tony Drews <[email-masked]>
Date: Wed, 02 May 2012 21:42:19 -0500

As I understand it, the stock crank will live pretty much forever if 
you shift at 5,000 RPM.  If well prepared (good radius between 
bearing surfaces and the rest of the crank, possibly nitrided as 
well), it will live a number of seasons shifting at 5,500 RPM.  When 
you start running it to 6,000 RPM, that's when the longevity drops 
pretty quickly - a season or two is about it before the #4 journal 
section goes.  Some last longer than others.  Sometimes when it goes 
it doesn't take out much else, sometimes it kills the block and a rod or two.

Tony Drews

At 06:23 PM 5/2/2012, [email-masked] wrote:
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From: "TeriAnn J. Wakeman" <[email-masked]>
Date: Wed, 02 May 2012 21:29:17 -0700

On 5/2/12 7:42 PM, Tony Drews wrote:
> you shift at 5,000 RPM.  If well prepared (good radius between bearing 
> surfaces and the rest of the crank, possibly nitrided as well), it 
> will live a number of seasons shifting at 5,500 RPM.  When you start 
> running it to 6,000 RPM, that's when the longevity drops pretty 
> quickly - a season or two is about it before the #4 journal section 
> goes.  Some last longer than others.  Sometimes when it goes it 
> doesn't take out much else, sometimes it kills the block and a rod or 
> two.
>
> Tony Drews
I don't remember the RPMs and I can't find them in my notes so my 
numbers will be a little iffy.

The way I heard it is that stock granks hold up well below the 5000 RPM 
red line. A little above 5000 RPM (5200ish?) there is a strong harmonic 
that tends to break the crank at the base of the flywheel mounting 
flange.  The common way to tame this harmonic is with an aftermarket 
harmonic dampener.  At full acceleration I commonly shift at 6000 RPM.  
My crank has a dampener & is nitrided and has held up well so far.

It is my understanding that there is a second major harmonic around 6200 
to 6400ish RPMs that wants to break the crank in the middle. I stay away 
from that harmonic because I don't think even a nitrided crank would 
hold up to that one for long.

Wishing I could find my notes on the subect,

Teriann

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From: "Greg Solow" <[email-masked]>
Date: Wed, 2 May 2012 22:22:41 -0700

Yes, a properly prepared, nitrided, stock crank is good for 6800 rpm and 160 
hp for a long time with light rods, pistons, and an aluminum flywheel with a 
diaphragm clutch. It does not need a damper on the front. It does need nice 
radiuses on all of the journals, a good balance, and nitriding is essential.
                                                                             
                        Greg Solow

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From: "Peter Vucinic" <[email-masked]>
Date: Thu, 3 May 2012 16:00:52 +1000

TeriAnn,
You are absolutely correct about wanting to stay away from any crankshafts
natural frequency. 

Operating in this range will induce crankshaft 'whip' and severe bending
moments into the crankshaft. Breaking the crank somewhere in the middle is
quite typical of this failure mode as the nose of the crank and the rear of
the crank are bending 180 degrees out of phase with each other. Flywheel
bolts that shear as a result of stretching is another indicator you are in
the natural frequency zone. No amount of nitriding or any other surface
treatment known to mankind will stop it breaking.

Lots of racing boat people learn this lesson quickly! Trying to run at a set
RPM range that coincides with the cranks natural frequency! Extremely
expensive mistake when it can be avoided by operating a few hundred RPM
higher or lower!

Cheers...

Kind Regards
Peter Vucinic
TR-4

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On
Behalf Of TeriAnn J. Wakeman
Sent: Thursday, 3 May 2012 2:29 PM
To: [email-masked]
Subject: Re: [Fot] TR4 crank

> doesn't take out much else, sometimes it kills the block and a rod or 
I don't remember the RPMs and I can't find them in my notes so my numbers
will be a little iffy.

The way I heard it is that stock granks hold up well below the 5000 RPM red
line. A little above 5000 RPM (5200ish?) there is a strong harmonic that
tends to break the crank at the base of the flywheel mounting flange.  The
common way to tame this harmonic is with an aftermarket harmonic dampener.
At full acceleration I commonly shift at 6000 RPM.  
My crank has a dampener & is nitrided and has held up well so far.

It is my understanding that there is a second major harmonic around 6200 to
6400ish RPMs that wants to break the crank in the middle. I stay away from
that harmonic because I don't think even a nitrided crank would hold up to
that one for long.

Teriann

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