[email protected] wrote in message news:<
[email protected]>...
> JP writes secretively:
>
> >> Over the course of most rides, most of your energy goes toward overcoming air resistance, (or,
> >> when riding uphill, to lift yourself and the bike). Acceleration isn't as important as a lot of
> >> people make it out to be.
>
> > Why is it easier to accelerate a mass in a weightless state (almost the same as a level surface)
> > than it is to accelerate it up a hill? I don't think anyone would argue that the same effort is
> > required.
>
> It isn't and it isn't. Linear acceleration is the same regardless of whether it is horizontal,
> vertical or any other direction. If there is an additional burden, such as wind or weight, in the
> case of an upgrade, that takes part of the effort.
I didn't say otherwise; in fact it is implied in my statement about the similarity of accelerating a
mass in a weightless state versus a level surface.
Weight, I guess you know, is an acceleration applied to a mass.
> > The fact is that gravity itself is an acceleration, and riding up a hill at a steady pace is
> > essentially a constant acceleration in terms of the impact of a bicycle's mass: your power
> > output doesn't only work to accelerate the mass of the bicycle, it also works to counteract the
> > acceleration of gravity against its mass and yours.
>
> I think you have accelerations confused.
I don't think so, but maybe you do. My point is that mass is a factor in acceleration, whether it is
level in the spin up of a sprint, or gravity acting on a bicycle wheel while *climbing*.
> Bicyclists do not accelerate rapidly enough in road riding to have any effect from small changes
> in peripheral weight on a wheel.
I didn't say they did, but define small. I did say that a .5% advantage is significant, implying
that .5% decrease in the mass of bicycle/rider combination could be decisive. In fact I will go out
on a limb and say that much smaller advantages in total mass could be decisive.
> This is especially true when hill climbing where no net acceleration takes place.
Not exactly. The cyclist going up a hill is being accelerated by gravity in opposition to the
direction of travel for the entire climb. The combined mass of the bicycle and the cyclist is a
factor. I am not saying that rotational inertia is a significant factor.
> As I mentioned, the flywheel effect of extra heavy wheels would enhance time trial speeds on the
> flat although carrying the weight up hill would be a detriment.
But since we are talking about *climbing* wheels, I guess your point is not evident to me. I guess
you are saying that a heavy wheel is bad on a climb? I agree.
> > I tend to think that a .5% difference is fairly significant at any level of competition, or to
> > look at it another way, if your conditioning is fairly evenly matched with your competitors, I
> > don't think you would want to give away .5% in your bike. If you have ever won a sprint by a
> > tire, no matter what the level of competition, you have won by a margin much smaller than .5%.
>
> Do you tend to think or do you think so? Don't beat around the bush.
I think I was pretty clear. I think that you pretend otherwise as a debate tactic. But since you
seem to like this sort of thing, let me be clear about it: there are a lot of things that seem
apparent to me but I am not so stupid as to extrapolate certainty about them in every circumstance.
> If you ride much you may have noticed that sprinting over a hill that is just a bit too long makes
> clear that almost no acceleration takes place as speed from the flat is maintained, it is a matter
> of power to maintain the speed. Speed change, if any, progresses at rates that demand minimal
> additional effort in comparison to the rate of climb effort. Acceleration is not even visible to
> an observer. When a rider pulls away on a hill, the rate of separation from the pack is
> essentially constant once the effort is begun. It is not one of accelerating.
The cyclist is counteracting acceleration- the acceleration of gravity, which makes mass an issue
for the entire climb, exactly the same as if the cyclist were accelerating the entire time.
The point is that there is no difference between riding up a hill at a constant speed and
accelerating on level ground. The effect of the mass of the cyclist is *exactly* the same, dependent
on the magnitude of the acceleration.
> > Regardless of the impact of rotational inertia, even small differences in wheel weight can be
> > significant in a climb.
>
> Hold it! That's putting the cart before the horse. That is the initial contention.
There was not an initial contention, there was an initial question- what makes a climbing wheel? The
answer is low mass.
> Repeating it without supporting evidence doesn't do much in supporting it other than making it a
> repetitious mantra.
I think gravity has been sufficiently supported that we can treat it as a given.
We frequently talk in this sport about how a small change in drag will affect the theoretical
outcome of a time trial. Well, the same effect is present with mass in a ride up a hill. I don't
think I have to perform the calculations for us to understand that a small change in mass will be
decisive in a climb, all other things being equal. That's why small improvements are important-
competitive cyclists who are very closely matched physically know that a few ounces may be the
difference between winning and losing.
I personally suspect ("tend to think") that rotational inertia is a factor in climbs because there
is a micro acceleration and deceleration with each pedal stroke on a climb, depending on a variety
of factors, such as grade, speed and riding style. It could conceivably be a significant factor in
the overall fatigue factor at the end of a long ride up a hill. It *might* be why LA's spinning
climbing style has an advantage (if it really is an advantage), but that's just speculation.
All in all, I would guess that the effect of rotational inertia is relatively small but measurable
in competitive cycling. I would certainly not dismiss it altogether without strong evidence that it
is insignificant, let alone your mere insistence that it is insignificant just because it *is*
small, if I were competing at an elite level.
JP