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From: David T. Ashley on 7 Apr 2010 12:35
2006 Honda Shadow 600 ...

The other day I was maneuvering the motorcycle at the gym (turning it around
by forward-reverse-forward-reverse-repeat) and nearly ran into a brick wall
going forward at maybe 1/2 MPH. I was on the brake at about the same time,
so I stopped about 1 cm short. But I thought ... what if I had hit the
wall?

Other times I've been slow on the brakes and hit a parking stop (those silly
cement things about 4-6 inches high) at well under 1 MPH. Essentially I was
coming to a stop just as the front wheel touched.

Other times I've taken the motorcycle over a curb by positioning the front
wheel against the curb, standing on the pavement with my but off the seat,
and then applying power and walking with the bike to get first the front
wheel then the rear wheel over the curb.

I was just curious about a few points ...

First, what are motorcycle front ends stressed for? What do you have to do
to do damage? My common sense tells me that the activities listed above
wouldn't do any damage because they don't generate as much stress as braking
hard and/or hitting a pothole with the front wheel.

Second, when is it wise to inspect things? How bad does it have to be
before you'd want to look at things carefully?

Third, what is the inspection protocol for front ends? What do you look
for?

Fourth, is it possible to have invisible damage where you have to remove the
steering stem and have a look? Looking at the mechanical system, it looks
like (because you have upper and lower bearings) that any overstressing
would get the welds near the steering tube first, then the fork holders
second, and that you wouldn't succeed in doing invisible damage internally
where you had to tear things apart. What goes first? Can anything be
invisible?

Sooner or later I will bump something harder than I'd like ... so just
curious.

Thanks.

From: Aham Brahmasmi on 7 Apr 2010 13:06
On Apr 7, 9:35 am, "David T. Ashley" <dash...(a)gmail.com> wrote:


> First, what are motorcycle front ends stressed for?

Space frames are designed to withstand about 6 or 7 g's in *bump*
without permanent deformation to the steel structure, but the steel
fork stanchion tubes can probably withstand about 10 g's without
bending permanently.

> What do you have to do to do damage?

Running into an imovable object at 35 to 40 mph should bend the fork
stanchion tubes quite visibly, and might bend the steering head
backwards enough to cause paint to flake off the frame tubes.

> My common sense (snip)

ROFLMAOSTC!

> tells me that the activities listed above
> wouldn't do any damage because they don't generate as much stress as braking
> hard and/or hitting a pothole with the front wheel.

My friend who rides a 1988 or 1989 FZR1000 bent his front rim from
hitting a pothole too hard, that was probably around 6 or 7 g's.

> Second, when is it wise to inspect things?

After you've returned home from the hospital.  

> How bad does it have to be before you'd want to look at things carefully?

It's obvious that you've hit something too hard when you look the
handlebars while going straight and one grip is noticeably closer to
you than the other.

> Third, what is the inspection protocol for front ends?

Take your machine to a place that can do laser alignment, if there's
one in your area. I think it's called "Computrack."

Otherwise, the protocol is to remove the seat, side covers, gas tank
front fender, front wheel, front forks instrument cluster, and
headlight and place the chassis (with engine and  rear wheel still in
place) on a surface plate so the steering head alignment can be
checked with protractors and various special tools that old time frame
shops like Buchanan's use.

> What do you look for?

The paint has flaked off and the gussets have bulged out sideways. The
engine cradle tubes and the backbone may be noticeably bent, but the
steering head tube itself might not show any damage.

> Can anything be invisible?

Brahman pervades the universe and all beings but cannot be perceived,
except by the sages.

"No one can grasp Him above, across, or in the middle. There is no
likeness of Him. His name is Great Glory (Mahad Yasah)." ---
Svetasvatara Upanishad, Chapter III, verse 19
From: Road Glidin' Don on 7 Apr 2010 14:46
On Apr 7, 10:35 am, "David T. Ashley" <dash...(a)gmail.com> wrote:
> 2006 Honda Shadow 600 ...
>
> The other day I was maneuvering the motorcycle at the gym (turning it around
> by forward-reverse-forward-reverse-repeat) and nearly ran into a brick wall
> going forward at maybe 1/2 MPH.  I was on the brake at about the same time,
> so I stopped about 1 cm short.  But I thought ... what if I had hit the
> wall?
>
> Other times I've been slow on the brakes and hit a parking stop (those silly
> cement things about 4-6 inches high) at well under 1 MPH.  Essentially I was
> coming to a stop just as the front wheel touched.
>
> Other times I've taken the motorcycle over a curb by positioning the front
> wheel against the curb, standing on the pavement with my but off the seat,
> and then applying power and walking with the bike to get first the front
> wheel then the rear wheel over the curb.
>
> I was just curious about a few points ...
>
> First, what are motorcycle front ends stressed for?  What do you have to do
> to do damage?  My common sense tells me that the activities listed above
> wouldn't do any damage because they don't generate as much stress as braking
> hard and/or hitting a pothole with the front wheel.
>
> Second, when is it wise to inspect things?  How bad does it have to be
> before you'd want to look at things carefully?
>
> Third, what is the inspection protocol for front ends?  What do you look
> for?
>
> Fourth, is it possible to have invisible damage where you have to remove the
> steering stem and have a look?  Looking at the mechanical system, it looks
> like (because you have upper and lower bearings) that any overstressing
> would get the welds near the steering tube first, then the fork holders
> second, and that you wouldn't succeed in doing invisible damage internally
> where you had to tear things apart.  What goes first?  Can anything be
> invisible?
>
> Sooner or later I will bump something harder than I'd like ... so just
> curious.
>
> Thanks.

You need to stop worrying. Normally, I'd suggest someone like you get
a motorcycle and ride it, but that doesn't seem to be helping in your
case.
From: David T. Ashley on 7 Apr 2010 15:07
"Road Glidin' Don" <d.langkd(a)gmail.com> wrote in message
news:c1c0188e-3374-465b-890f-85752f44f735(a)5g2000yqj.googlegroups.com...
>
>You need to stop worrying. Normally, I'd suggest someone like you get
>a motorcycle and ride it, but that doesn't seem to be helping in your
>case.

Hi Don,

Surprisingly, my little Honda Shadow is almost due for its 24,000 mile
maintenance. I bought it with 1,350 miles on it, so I have done a bit of
riding. : )

In all seriousness ...

I don't care much about car maintenance. I have it done, or course, but
there are four wheels and if one falls off ... not necessarily a huge deal,
especially the way I drive (like an old lady). I do whatever the dealership
recommends I do, and I don't think about it too much. I do pay close
attention to steering and brakes, naturally.

Motorcycles are a bit different. It hasn't escaped my notice that if a
wheel falls off, my life could get a lot worse very quickly.

So, I pay pretty close attention to structural issues. As you might
remember, I ordered a new rear axle a few years back and had the dealership
install it just so I could look at the old one. Between the dealership and
the helpful posters here, I satisfied myself that the thing was reliable.
The dealership also assured me that they've never seen an axle break in
service (although they have seen people strip the threads off them). Same
thing with the front axle. Last time I had tires put on and they had the
wheel off, I grabbed the front axle, wiped it off, and looked it over very
carefully (looking for any cracks, mostly).

Whenever I have the trim off near the steering tube, I look over the welds
very carefully. (I've also noticed that there are a lot of welds and that
Honda has welded additional material in there to add strength.)

After I had one of my mishaps (low-sided the motorcycle at low speed in a
parking lot), I brought it to a dealership and asked if there was anything
up front that needed to be inspected. They inquired about the character of
the mishap and whether I struck anything or just slid the bike for a few
feet. The service manager then explained that they are built well enough
that a low-side slide at parking lot speeds won't do anything (the speeds
need to be a bit higher or I need to strike something). I was satisfied
with his explanation.

So all of the questions in my post are relevant to me ... just curious if I
ever need to look anything over or how hard I need to whack something ...

I do ride it. It is just that I'm keenly aware that structural integrity is
important ...

: )

Dave.

From: The Older Gentleman on 7 Apr 2010 15:29
David T. Ashley <dashley(a)gmail.com> wrote:


>
> First, what are motorcycle front ends stressed for?

Lots, but there's always a limit.

> What do you have to do
> to do damage? My common sense tells me that the activities listed above
> wouldn't do any damage because they don't generate as much stress as braking
> hard and/or hitting a pothole with the front wheel.

You'd be surprised. Minor frontal impacts... well, I remember riding
into the back of a car, decades ago, because I wasn't looking where I
was going. The back end of the bike pirouetted neatly upwards. No
visible damage to anything, but it popped both fork seals.
>
> Second, when is it wise to inspect things? How bad does it have to be
> before you'd want to look at things carefully?

Check after any impact. Properly.
>
> Third, what is the inspection protocol for front ends? What do you look
> for?
>
> Fourth, is it possible to have invisible damage where you have to remove the
> steering stem and have a look? Looking at the mechanical system, it looks
> like (because you have upper and lower bearings) that any overstressing
> would get the welds near the steering tube first, then the fork holders
> second, and that you wouldn't succeed in doing invisible damage internally
> where you had to tear things apart. What goes first? Can anything be
> invisible?

Steering head bearings go first. Forks second. Frames themselves are
surprisingly resilient. Steel frames can distort, but can be jigged back
into position. Alloy frames can crack and break. Beams can develop a
'wrinkle'.

A good check is the lock stops - people can straighten frames, replace
forks, but it's damn hard to repair damaged lock stops without it
showing.



--
BMW K1100LT Ducati 750SS Honda CB400F Triumph Street Triple
Suzuki TS250ER GN250 Damn, back to six bikes!
Try Googling before asking a damn silly question.
chateau dot murray at idnet dot com
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