Subject: Re: Loopframe Wobble
Author: dbjo-@bellatlantic.net
Date: Sep 8, 2000, 4:37 AM
Post ID: 1702357301
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Tim,
Here's one story for you. It's long, sorry. I have been a sportbike
rider all my life, and have enjoyed going faster than I should on a
routine basis. This year, I took my 1973 Eldorado to Moto Guzzi Day in
Angier, NC from my home in the Pittsburgh, PA area. The ride down was
with 6 other riders, and was fairly civilized. On the way home, I
hooked up with 3 other riders, and the lead two guys were on SP1000's
and the other on an SPIII. The lead two guys are riding partners, and
have travelled tens of thousands of miles on Virginia and West Virginia
backroads, and know them well. We spent our first day of our return
trip riding through North Carolina and most of Virginia, stopping for
the night in northern VA. The next day we set off for home, and these
guys were flying. We crossed the Virginia border into West Virginia,
and began travelling the WV coal roads, which are tight, twisty, and up
and down hills. These guys were passing cars and coal trucks on tight
turns , sometimes 2 cars and a coal truck at a time. The Eldo simply
doesn't have the horsepower or brakes to keep up, but I was riding the
bike hard, and pushing it to its limits. By the time this ride was
over, for instance, the tang that puts the sidestand down was ground
literally to a razor's edge. Many times in the course of this ride, I
would enter turns, particularly downhill turns, or turns with uneven
pavement, and the Eldo would oscillate the front end, or just headshake
a bit, but would settle down and I would ride through it. I was having
to ride the Eldo like the old superbikes, sliding up onto the tank to
weight the front end in some turns, and to slide off on one side or the
other to allow myself more ground clearance. Yea, I know I'm nuts.
Anyhow, these guys made one pass on two SUV's and a coal truck on an
uphill blind righthander that I simply couldn't make because of the
limits of acceleration on the Eldo. So, I was fairly well behind when I
finally passed these three vehicles and set off to catch up. I entered
a slightly downhill, high speed sweeper. As usual, the Eldo set up nice
and we were travelling some 75mph through this lefthand sweeper. At the
exit of the turn was a long straight of about a mile that went slightly
downhill and then slightly uphill, so it was a long, clearly visible
straight. The other guys were almost out of sight. As I came to the
exit of the sweeper, with the Eldo tracking beautifully on smooth
pavement, I began to straighten up the bike. The front end started one
of these slow oscillations, just like it had 10 times before on this
ride. I held steady throttle as the bike came upright. The oscillation
continued. I kept the throttle steady. The bike began to headshake
more. I rolled on a little more throttle, as conventional logic is
NEVER shut off when a front end problem like this starts. The headshake
kept amplifying at a rapid rate. In the space of maybe 2 seconds, the
bike had gone from a mild oscillation to a vicious tankslapper. It was
so violent that the bars were going stop to stop, and would yank free of
my grip sometimes. I knew I was going down, but tried to stay with the
bike as long as possible to scrub off some speed. It became so violent
and was such a bigtime tankslapper that the rear wheel had broken loose
and was leaving black streaks back and forth as the front swapped side
to side. At some point, when the rear slid to the bike's right, I layed
it down, going perhaps 70mph. The bike slid for a long time (measured
137 paces) but it slid straight down that aforementioned long straight,
and so did I .
As a post mortem of this accident, the riders who were with me and I
thought about what had happened. Admittedly, I was riding this
loopframe waaay too aggressively for it's intended purpose, and this
accident was my own doing. However, it WASN'T because of rider error,
like taking it too fast into a turn and losing traction, etc. Something
happened with the bike, and overtaxed its limits, because we were going
too fast. I hope you understand the distinction I am trying to make.
When I exited this long sweeper, which was lined with trees, there was
meadow on each side. One of the riders speculated that perhaps a cross
wind collected my police windshield and started this problem. For those
of you with loopframes, have you ever loaded your bike down pretty well,
with saddlebags and maybe a load on a tail rack and felt the front end
become light at low speed and oscillate then? I don't know if that
behavior has some relationship to these high speed wobble problems that
have occurred with some loopframes or not. Anyhow, when I ride my Eldo
without a lot of gear on it, and I ride it briskly but sensibly, it is
just fine. However, I did have this one problem, and it was a VERY
scary episode, because it came without warning when the bike was
otherwise performing beautifully in that long sweeper. As I recall from
either Greg Field's book or other stories, there was at least one test
rider killed in Italy and one cop killed in the States due to these
wobbles. I am sure they were pushing the bikes pretty hard, as I was,
and perhaps this wouldn't have happened to them or me if we were riding
within the bike's envelope. As I also recall from Greg's book, they
used to ship these wobbler frames back to Italy and they were destroyed,
as I remember. Anyhow, that's my story for what it's worth.
Dennis Jones
Bethel Park, PA
Tim wrote:
| I read in Greg Fields book, and just had a reminder in the latest newsletter, about the strange trouble that a few of the Ambo/Eldos had with a high speed wobble. Since I am new to Guzzis, did anyone ever figure out what caused this, and is there any fix? How common was this? Also, being as I am getting my Eldo ready for the season, is there anyway to tell if my bike is one of the wobblers without getting into trouble? Is the wobble similar to a tank slapper, or is it more subtle? Thanks,Tim --- Sponsor's Message -------------------------------------- Get email and like it! Upgrade your brain with informative newsletters from IDG. From hot products to high-speed LANs, Linux to Novell, we've got the email you want--FREE at Topica! http://click.topica.com/aaaaBHb1dfltb1mSObc/PCWorld ------------------------------------------------------------ ___________________________________________________________ T O P I C A The Email You Want.http://www.topica.com/t/16 Newsletters, Tips and Discussions on Your Favorite Topics |
Dennis Jones
Bethel Park, PA
1973 Moto Guzzi Eldorado
1976 Honda CB400F - Red Rocket
1987 Moto Guzzi LeMans IV
1996 Ducati 900CR
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Tim,
<br>Here's one story for you. It's long, sorry. I have been
a sportbike rider all my life, and have enjoyed going faster than I should
on a routine basis. This year, I took my 1973 Eldorado to Moto Guzzi
Day in Angier, NC from my home in the Pittsburgh, PA area. The ride
down was with 6 other riders, and was fairly civilized. On the way
home, I hooked up with 3 other riders, and the lead two guys were on SP1000's
and the other on an SPIII. The lead two guys are riding partners,
and have travelled tens of thousands of miles on Virginia and West Virginia
backroads, and know them well. We spent our first day of our return
trip riding through North Carolina and most of Virginia, stopping for the
night in northern VA. The next day we set off for home, and these
guys were flying. We crossed the Virginia border into West Virginia,
and began travelling the WV coal roads, which are tight, twisty, and up
and down hills. These guys were passing cars and coal trucks on tight
turns , sometimes 2 cars and a coal truck at a time. The Eldo simply
doesn't have the horsepower or brakes to keep up, but I was riding the
bike hard, and pushing it to its limits. By the time this ride was
over, for instance, the tang that puts the sidestand down was ground literally
to a razor's edge. Many times in the course of this ride, I would enter
turns, particularly downhill turns, or turns with uneven pavement, and
the Eldo would oscillate the front end, or just headshake a bit, but would
settle down and I would ride through it. I was having to ride
the Eldo like the old superbikes, sliding up onto the tank to weight the
front end in some turns, and to slide off on one side or the other to allow
myself more ground clearance. Yea, I know I'm nuts. Anyhow,
these guys made one pass on two SUV's and a coal truck on an uphill blind
righthander that I simply couldn't make because of the limits of acceleration
on the Eldo. So, I was fairly well behind when I finally passed these
three vehicles and set off to catch up. I entered a slightly downhill,
high speed sweeper. As usual, the Eldo set up nice and we were travelling
some 75mph through this lefthand sweeper. At the exit of the turn
was a long straight of about a mile that went slightly downhill and then
slightly uphill, so it was a long, clearly visible straight. The
other guys were almost out of sight. As I came to the exit of the
sweeper, with the Eldo tracking beautifully on smooth pavement, I began
to straighten up the bike. The front end started one of these slow
oscillations, just like it had 10 times before on this ride. I held
steady throttle as the bike came upright. The oscillation continued.
I kept the throttle steady. The bike began to headshake more.
I rolled on a little more throttle, as conventional logic is NEVER shut
off when a front end problem like this starts. The headshake kept
amplifying at a rapid rate. In the space of maybe 2 seconds, the
bike had gone from a mild oscillation to a vicious tankslapper. It
was so violent that the bars were going stop to stop, and would yank free
of my grip sometimes. I knew I was going down, but tried to stay
with the bike as long as possible to scrub off some speed. It became
so violent and was such a bigtime tankslapper that the rear wheel had broken
loose and was leaving black streaks back and forth as the front swapped
side to side. At some point, when the rear slid to the bike's right,
I layed it down, going perhaps 70mph. The bike slid for a long time
(measured 137 paces) but it slid straight down that aforementioned long
straight, and so did I .
<p>As a post mortem of this accident, the riders who were with me and I
thought about what had happened. Admittedly, I was riding this loopframe
waaay too aggressively for it's intended purpose, and this accident was
my own doing. However, it WASN'T because of rider error, like taking
it too fast into a turn and losing traction, etc. Something happened
with the bike, and overtaxed its limits, because we were going too fast.
I hope you understand the distinction I am trying to make. When I
exited this long sweeper, which was lined with trees, there was meadow
on each side. One of the riders speculated that perhaps a cross wind
collected my police windshield and started this problem. For those
of you with loopframes, have you ever loaded your bike down pretty well,
with saddlebags and maybe a load on a tail rack and felt the front end
become light at low speed and oscillate then? I don't know if that
behavior has some relationship to these high speed wobble problems that
have occurred with some loopframes or not. Anyhow, when I ride my
Eldo without a lot of gear on it, and I ride it briskly but sensibly, it
is just fine. However, I did have this one problem, and it was a
VERY scary episode, because it came without warning when the bike was otherwise
performing beautifully in that long sweeper. As I recall from either
Greg Field's book or other stories, there was at least one test rider killed
in Italy and one cop killed in the States due to these wobbles. I
am sure they were pushing the bikes pretty hard, as I was, and perhaps
this wouldn't have happened to them or me if we were riding within the
bike's envelope. As I also recall from Greg's book, they used to
ship these wobbler frames back to Italy and they were destroyed, as I remember.
Anyhow, that's my story for what it's worth.
<br>Dennis Jones
<br>Bethel Park, PA
<p>Tim wrote:
<blockquote TYPE=CITE><style></style>
<font face="Arial">I read in Greg
Fields book, and just had a reminder in the latest newsletter, about the
strange trouble that a few of the Ambo/Eldos had with a high speed wobble.
Since I am new to Guzzis, did anyone ever figure out what caused this,
and is there any fix? How common was this? Also, being as I am getting
my Eldo ready for the season, is there anyway to tell if my bike is one
of the wobblers without getting into trouble? Is the wobble similar
to a tank slapper, or is it more subtle?</font> <font face="Arial">Thanks,</font><font face="Arial">Tim</font>
<pre>--- Sponsor's Message --------------------------------------
Get email and like it! Upgrade your brain with informative
newsletters from IDG. From hot products to high-speed LANs,
Linux to Novell, we've got the email you want--FREE at Topica!
<a href="http://click.topica.com/aaaaBHb1dfltb1mSObc/PCWorld">http://click.topica.com/aaaaBHb1dfltb1mSObc/PCWorld
</a>------------------------------------------------------------
</pre>
<pre>___________________________________________________________
T O P I C A The Email You Want. <a href="http://www.topica.com/t/16">http://www.topica.com/t/16
</a>Newsletters, Tips and Discussions on Your Favorite Topics</pre>
</blockquote>
<p>--
<br>Dennis Jones
<br>Bethel Park, PA
<br>1973 Moto Guzzi Eldorado
<br>1976 Honda CB400F - Red Rocket
<br>1987 Moto Guzzi LeMans IV
<br>1996 Ducati 900CR
<br>
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