Very cool. Most of the things we think we know about mechanical stuff are
really approximations based on static measurements. Not just for wildly
dynamic stuff like rapidly moving gas columns, but even mundane mechanical
things like cam timing with chain stretch and tensioner movement and the
stroke of an engine varying considerably with RPM for example.
Bill Babcock
Babcock & Jenkins
-----Original Message-----
From: owner-fot@Autox.Team.Net [mailto:owner-fot@Autox.Team.Net] On Behalf
Of Larry Young
Sent: Wednesday, January 12, 2005 12:50 PM
To: fot@Autox.Team.Net
Subject: Re: TR4 rocker ratio
This question was raised a couple weeks ago. I thought is was time for a
technical discussion. A couple years ago I decide to measure the rocker
ratio. Using a dial indicator and degree wheel, I measured the lift curve
at the cam (no rocker assembly). Then I installed the rocker assembly and
measured the lift curve at the valve. I took the ratio of the two curves
and got the graph at http://home.swbell.net/cartrip/RockerRatio2.gif . I
was surprised and confused by the fact that I did not get a horizonatal
line. Later I realized I'm looking at compression of the valve train.
After measuring the valve springs constant and installed spring pressure, I
was able to estimate a valve train stiffness of about 60,000 lb/in. Sounds
like a big number, but with 100 lbs of seat pressure (150 lbs at the cam),
you get 2.5 thousandths deflection. I guess this sort of thing is common
knowlege in mechanical engineering circles, but it was news to me. So, even
though the rocker ratio is 1.49 you don't see that much more lift at the
valve.
EDWARD BARNARD wrote:
>My documentation is showing two different numbers for the stock ratio.
>One is 1.49/1 the other is 1.5/1. Hope that is some help. - Ed
>
>Stutzman <stutzman@adelphia.net> wrote:what is the TR3/4 stock rocker
>ratio? I always thought it was 1.4 but I can't find it in the manuals.
>bruce stutzman
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