I'm an experienced crankshaft breaker. When I started racing, I fitted the
narrow V-belt conversion together with the MGB crankshaft pulley/dampener.
This is the dampener sold by Moss Europe and also by Rimmer Bros UK, neither
of these companies are giving any explanation about the rpm range. Dampers
have their own natural oscillation, but it seems no one can tell what this
rpm is for this pulley.(Maybe this rpm is getting lower with the aging and
deteriorating of the bonding material). After some 10 races with this MGB
dampenenr, my standard, balanced but not nitrided, crankshaft broke at the
usual spot : the rearmost web near the 4th big end journal ( John Hasty has
sent a photo to Chris Marx, showing a crank broken at this spot). Then I
bought a billet steel crankshaft and raced it with the same MGB dampener :
this crankshaft broke after 5 race week ends (about 7 race hours) at the
same spot. I bought this steel crank from TR Enterprises, but the original
dealer is a german race parts supplier, who is trying to keep prices low,
sometimes this policy goes wrong : I know of 3 other failures of this same
make of steel cranks, one on an engine of Jo Willems, fitted with a damper.I
don't know if the 2 other broken cranks were raced with or without a damper.
In the meantime, TR Enterprises was aware of the bad quality of these
cranks, and I got free parts from them as a partial compensation, after the
german supplier had to agree that the crank was faulty. I appreciate a lot
what TR Enterprises(UK) has done.
Since 2007, I have a billet steel crank with dummy mains and 8 counter
weights in order to have the 4 cranks balanced on their own. After about 100
races, the crank is in best shape, notwithstanding the use of the MGB
dampener. A Mr Nuyts of Antwerp, Belgium, has made this crank for 1675 Euro,
a little more than half of the price of the german steel crank.
After reading all the comments, and the experience of Kas Kastner who did
not fit damper pulleys on his countless engines, without bad consequences,
I'll remove the MGB damper on my race engine and will fit the small
aluminium Gilmer pulleys, saving at least 4 lbs.
Marcel, Belgium
-----Oorspronkelijk bericht-----
Van: fot-bounces@autox.team.net [mailto:fot-bounces@autox.team.net] Namens
MadMarx
Verzonden: vrijdag 6 december 2013 22:04
Aan: fot@autox.team.net
Onderwerp: Re: [Fot] aftermarket crank dampeners and pullies for TR4's
You are right with your statement but let me add this.
With nitrate hardening you insert nitrate to the surface to make it harder.
As you notice your bearings grow from that.
I cant explain it properly:
You get an pushing pressure along the surface. If the crank bends the
pulling pressure on the surface is delayed by the pushing pressure caused by
the hardening. You use the same affect with shot peening.
That makes the crank more resistant against cracks.
Simple, isnt it?
Cheers
Chris
Von: Tony and Annie Garmey [mailto:horizonracing@msn.com]
Gesendet: Freitag, 6. Dezember 2013 21:56
An: Chuck Gee; MadMarx
Cc: fot@autox.team.net
Betreff: RE: [Fot] aftermarket crank dampeners and pullies for TR4's
I may be incorrect here, but isn't nitriding a surface harding? It helps
with wear on the Bearing surfaces. The best precaution I have found
regardless if its a stock crank or billet, is making sure the radius at the
bearing Journals are as big a radi as you can. Even if you have to chamfer
the bearings. Shot penning a stock crank will also help smooth the edges.
Not Always, but a crack will start at a Corner or sharp edge.
Tony G.
> Date: Fri, 6 Dec 2013 11:59:23 -0600
> Subject: Re: [Fot] aftermarket crank dampeners and pullies for TR4's
>
> And nitride it to try and keep the crack from starting in the first place.
>
> Chuck
>
> > On Dec 6, 2013, at 11:39 AM, "MadMarx" <
> >
> > 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'
> > 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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