Date: Sun, 23 Feb 2003 21:16:33 -0600
Reply-To: Stan Wilder <wilden1@JUNO.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Stan Wilder <wilden1@JUNO.COM>
Subject: Re: I4 engine/vibrations
Content-Type: text/plain; charset=us-ascii
I have been following this link with some interest because I've had
persistent problems keeping the 4 rear engine mounts in my air cooled.
That withstanding I've seen very effective thrust / torque limiter rods
on various Dodge, Lexus and VW Sirocco engines. Most have a rod with a
round loop with a rubber dampener in both ends. This devise accommodates
the torque generated on fast take offs, heavy torque of climbing hills or
a variety of situations that would otherwise compress or stretch engine
mounts to a failure state.
Under normal operations these mounts are passive unless the engine mounts
have failed and pre loaded them by mis alignment.
I considered the VW engine mounts on my air cooled (same as Wasser boxers
of all years) to be fairly rigid although they never appeared to be
substantial in my estimation.
Having run several engines on my test stand with 4 new motor mounts the
loading and displacement of the mounts is very visible to the naked eye
each time the engine is revved. I don't have the ability to load the
engine on the test stand but I've got a vivid idea of how these engine
mounts deform and load if you have a wheel spin on wet streets.
The alternator in the VW Dasher has rubber vibration dampeners in the
mounting frame (had one on my 71 MG Midget). This might be an option for
alternator vibrations.
In working with GM vehicles the Astro Van V6 has a very good idler on the
serpentine belt that might be of use in reducing vibrations. The Chevy V6
has low rpm vibration problems and cycles through several critical rpm
ranges that give the feeling of strain on the drive line. The Chevy idler
has an internal spring that is dampened with cast in rubber.
I've had a fair number of InLine 4 cylinder vehicles and vibration was
pretty much an accepted feature of having a 4 cylinder. I believe that
because of the weight of the Vanagon the vibration is enhanced by heavily
loading the engine mounts far in excess of the intended vehicle weights
of 1800 to 2200 pounds.
Adapting engine mounts from a heavier engine or application might be a
solution to consider. (Frank Grunthaner "All manufacturers (VW. Porsche,
Audi, Mercedes, SAAB, Volvo to name a few Euro's) adopt one of two
solutions: Addition of a balance shaft to the engine or the use of
hydraulic (actively damped) engine mounts. I have adapted the SAAB
hydraulic mount to the VW Vanagon diesel mounting system (refers to the
'82 design only since this is what I play with)".
BMWs rear wheel drive often use a rubber torque drive that equates to a
big rubber biscuit that replaces the conventional U joints.
I have noticed on several vehicles ............. flat bars with steel
weights dampened with rubber bushings to reduce harmonic resonance. 63
Porsche for one.
Stan Wilder
| 
