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General
Questions:
What about MY bike?
If you have a bike that is not mentioned in the application
finder, call me at 763 234 7242 to discuss it. I may already
fit your bike but not know it. I may be interested in working
with you to make a product to fit. That normally comes under custom
work, but for the more popular applications, I would cut you a
special deal, since I want the opportunity to fit the bike
anyway. PLEASE let me know if you would like these weights,
but have an application they will not fit. I will come out with new
flavors in the order of these requests.
Why so nervous about aluminum handlebars?
Fatigue resistance of the metal. Steel has nearly infinite
fatigue resistance within its elastic limits (meaning as long as
the vibration never bends it so hard it can't spring back.) We made
our weights as heavy as we could, while sticking out minimally,
looking good, and above all, not overstressing any other part of
the bike. We are confident that steel bars can handle the added
stress. Aluminum is another story. Aluminum has a finite fatigue
resistance. This means that persistent vibration anywhere near the
elastic limits, will eventually cause the piece to crack in two at
the place with the most severe flexing due to the vibration. For
this reason, Aluminum structures that are subject to vibration, or
other repetitive dynamic loads, must be dramatically overbuilt, to
keep the flexing way down. I am sure the OEM's have done the
extensive testing and sophisticated modeling to determine that
Aluminum handlebars will not crack off in normal use. However, our
line of weights is pretty extreme. In some applications, you can
feel that the tips of the bars vibrate less than the instrument
pods. This means that the handlebars may be flexing MORE in some
places, than they do without weights, just to take the vibration
away from your hands. Thus the risk of metal fatigue goes up. It
MAY be safe on Aluminum, anyway. But we have not done the testing,
modeling, or calculations to determine whether it is, or not.
How do they work?
AAAAAyyyyy!!! Bar-end weight theory: As your motorcycle runs,
the handlebars form a resonant mechanical system. That is, the bars
tend to shake at certain frequencies, in certain ways. The lowest
frequency, or fundamental, is a motion you could call, "flapping."
This is where the center of the bars, between the clamps, is
motionless, and the tips of the bars are vibrating most. This is
typically the strongest mode of vibration, and the first one you
should attack. If this frequency is any component of the
characteristic frequency spectrum of your motorcycle, then the bars
start to flap away, bothering your hands. There are three ways to
solve the problem.
- Stop the vibration. Many aspects of motorcycle design can come
into play to check vibration at the factory. Details of crankshaft
design, firing order and angle, mounting location, and
counterbalancers can be used in concert to make for smooth running.
If the engineers who designed your bike were skillful and careful
about these factors, as they affect vibration, you can stop reading
now- you don't need this product.
- Dampen the vibration. From an engineering standpoint, dampening
means eliminating the resonant frequency of the handlebars. The
proper way to do this is with a precisely designed flexible
attachment between the vibrating part and a solidly mounted part,
in other words, a shock absorber. The flexible attachment must be
tuned to exactly oppose the specific frequencies of resonance, so
vibration put into the bars will not be allowed to build up in them
and hurt your hands. Unfortunately, there is no proper way to
dampen the handlebar motion, without a mechanical linkage from the
outside of the bars to the frame of the bike, other than the bars.
There are products out there which purport to dampen handlebar
motion, but they can't technically "dampen" the fundamental
frequency, since there is no linkage between the bar ends and the
frame. That is not to say they don't "work." I haven't tried them,
but I know many who are quite satisfied with them. Why, if they
aren't dampening the bars from flapping? The higher-order harmonics
of the resonant frequencies should be effectively reduced by, say,
inserting a combination of weight and viscoelastic material into
the bars. Due to the physics of the situation, the higher the
vibrational frequency, the less weight is required to disrupt the
motion, and the less solid the mounting point of the dampening
system needs to be. So having a heavy elastomer all the way through
the bars would be great for the higher harmonics, with the internal
motion of the elastomer discouraging the formation of standing
waves in the bars. But that lowest resonant frequency, the flapping
motion, is typically the strongest. For that motion, all that
elastomeric stuff in the bars is only as good as its mass. In other
words, it operates just like plain weights- it lowers the resonant
frequency, and discourages the tips of the bars from changing speed
quickly. This brings us to the last means of vibration
control.
- You could change the resonant frequency. When operating in this
mode, the closer the weight is to the tips of the bars, the more
effective it is. Solutions that involve equal mass throughout the
length of the bars, have only a fraction of their mass working for
the cause. The rest is dead weight. As a rule of thumb, any mass
between the first two curves of the bar from center, is dead
weight, and any mass at the tips of the bars is fully effective.
That's why our bar-ends are designed to maximize weight just
outboard of the bars. They are 12.5 oz. per side or more, and every
ounce hits home.
How do bar-end weights change the resonant frequency and reducevibration?
Resonant frequency is the frequency at which an object "rings"
if it is moved. When you hit a tube with a hammer, and listen at
the end of the tube, you are hearing the audible portion of its
resonant frequency spectrum. The "fundamental" is the lowest note.
In handlebars, this is the frequency made by the bars "flapping."
By flapping I mean that the bar clamps stay put, while the tips
move most. This fundamental frequency is typically the strongest
frequency, thus the first one to attack. Weights on the tips of the
bars reduce vibration by moving the resonant frequency lower, away
from the frequencies generated by the engine. This happens for the
same reason that a heavier guitar string sounds lower, under the
same tension, than a lighter one. Because the effectiveness of a
weight in reducing vibration this way reduces to zero as the weight
approaches the bar clamp, I was careful to keep as much weight
outboard of the bar ends as possible. All the weight is
concentrated where it is most effective- right near the bar-ends.
All the weight is within 2.5" of the bar ends. There's no dead
weight as with solutions that go all the way through the bars. By
moving the resonance lower, it typically moves further from the
frequency of the engine, which reduces the build-up of vibration in
the bars dramatically. The other way to look at it is in terms of
inertia. By solidly mounting the weights to the ends of the bars,
the bar-ends gain a great deal of inertia, which means that they
are much more reluctant to change speed. Since the flapping motion
involves the bar ends accelerating this way and that in rapid
succession, any weight on the ends reduces this motion. When you
are trying to contain vibration by changing the resonant frequency,
solid-mounting is the way to go. Any flexibility to the mounting
muddies the effect of the extra weight, hurting the cause.
Will all that weight on the bar ends slow down theresponsiveness of my bike?
Theoretically, yes, a little. However, people typically report
that responsiveness is not affected by measures like these. I have
even heard of people pouring molten lead into their bars, filling
them to the brim, (a few times the mass of our bar-end weights) and
saying their handling was unchanged. Why wouldn't you notice a
slow-down in turn initiation? A way to understand this is with the
concept of resonance, and its effect on the ability of the bar ends
to change speed, discussed above. The fundamental frequency of the
engine (67 Hz, for a single, operating at 4000 RPM) is at least
130x the frequency of a rider's steering input. (0.25 - 0.5 Hz.)
That means that a weight which is sufficient to seriously
discourage the engine resonating with or flapping the bars, is
inconsequential to the much lower frequency involved in steering
the motorcycle.
Can't I just tough it out and save money?
Maybe. If you are lucky, you have very good circulation,
well-routed nerves, strong wrists and hands, and you can tough it
out. But long days in the saddle can wear you down, and in the long
run, it's best to take care of yourself. Depending on you and the
bike, vibrations can get seriously harmful to your health.
Vibrating bars can worsen carpal tunnel syndrome and arthritis,
aggravate circulatory problems, cause numb or tingling hands, etc.
If this happens to you, take it seriously. Most of these problems
get aggravated more, the more they get aggravated. Give your wrists
a break! See our article about Hand Trouble for more
information.
What is different about the Smooth City tm series bar-endweights and throttle locks, compared to the original designs?
On the good side:
-We can fit many more bikes, with more finishes and more
options. -It is easier to fit yet another bike.
-Weights and throttle locks have internal clearance adjustment
features, to ease installation and reduce the need for fiddling
with the rest of the bike to make them fit.
-Our Pounders tm heavy weights are a fresh new design, replacing
the older Dragonfly tm design for our one-pound units.
On the bad side:
-Hollow-Tube fitments are slightly harder to tighten down.
-Hollow-Tube fitments are not as super-tough as the original
ones, as their bending strength is now limited by the tensile
strength of the screw that goes through them, rather than the stout
machined nose that goes into the bar. but they are still
stronger than some of the bolt-On fitments for some OEM
designs.
-There are more pieces in a kit.
I ran out of shims, or the screws that came are the wronglength. What do I do?
You can steal a few shims on the left side, since no clearance
is necessary between the left grip and the weight. Otherwise
call me, 763-234-7242, and I will set you up. I will want to
know details, to judge whether I should change what is in
the kind of kit you bought.
Do you sell spare parts?
Yes, to returning customers. We make sure to carry
all consumable things, like expansion nuts, and your odds with old
hardware are good. No guarantees about any pre-Smooth City
bar-end weights, we have been liquidating them. Call our
sales line to order 612-868-9881
Do you sell your nice screws alone?
No. Right now we cannot do that gracefully on an
administrative level. Maybe someday we will be prepared to do
it, but we need to concentrate on the core business now.
However, we go to a great deal of trouble to see that customers are
satisfied with their installations, and this can mean shipping odd
screws and other parts for their unusual bikes. If our
application chart indicated that we could fit their bike, and their
Handlebars are OEM, we do not charge for this extra effort.
I have aftermarket "HotGrip" heated grips. I currently need toreplace them (due to age/wear) and would like to add Salamanderends. I am assuming installation will require cutting ends of gripsopen. Do you forsee an issue with these particular grips (theyrequire epoxy onto handle bar and throttle sleeve)?
You can cut a hole in the ends of Hot GripsTM grip
heaters no problem. Just don't cut off the
end. Generally, any heated grip with an inboard power feed
(that doesn't feed out the end of the handlebar) is fine with our
products.
Hot GripsTM have been available for several years
with open ends, and those are ideal for our products.