Yeah my break with the common MGB style dampner sold today was also just
behind the front main. One weekend on the crank and it broke on the warmup
lap!
So much work put into that crank...it was artwork. So much so that I still
have it ensconced in its own little display in the shop.
from an old crank...
Nick in Nor Cal
-----Original Message-----
From: MadMarx <tr4racing@googlemail.com>
To: fot <fot@autox.team.net>
Sent: Fri, Dec 6, 2013 9:56 am
Subject: Re: [Fot] aftermarket crank dampeners and pullies for TR4's
Unusual spot to break because the torque rises from front to rear. So the
first spot to break is the rear end with the highest load.
I'm a civil engineer, so I have a small clue about forces.
If the crank has no flywheel and not pulleys, just the crank with rods and
pistons it can freely bend on high load like a two field beam.
A flywheel stops bending because the flywheel don't like to wobble, it likes
to run straight so the cranks rear end is forced to run straight, while the
parts between the mains swing. That induce forces into the last counter
weight and maybe lead to a crack.
The same with a damper on front. It reduces the swing in the middle between
main 1 and 2 but it rises the force on the counter weight.
As a civil engineer I would say, let it swing and make the flywheel and
clutch as light as possible and you get the most out of the crank.
Cheers
Chris
-----Urspr|ngliche Nachricht-----
Von: fot-bounces@autox.team.net [mailto:fot-bounces@autox.team.net] Im
Auftrag von John Hasty
Gesendet: Freitag, 6. Dezember 2013 15:54
An: 'Michael Porter'; 'Randall'
Cc: fot@autox.team.net
Betreff: Re: [Fot] aftermarket crank dampeners and pullies for TR4's
For what it is worth, we got 10 race weekends on our last rebuild running a
damper from BFE. The crank broke between # 1 rod and front main on last
race, last lap, last turn while running 1st. in EP. I regularly turned 6500
in 2nd, 3rd, 4th and 6200 in OD. The motor always ran smooth with no
vibration I could feel even with the front engine plate bolted directly to
the frame
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