Getting Started on Rollers

Ewoud Dronkert says...

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And notify the downstairs neighbours that, no, you're not building a jet
engine.

You don't build jet engines at home? Whaddya do with all your time? Ride
rollers and watch TV?

Bob Schwartz says...

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- You won't shoot out the picture window if you don't ride
with a gun.

Something you have experience with, eh Bob?

Quoted message said:

- Wiping out on rollers is more embarrassing than painful.

Just don't high side. Those slow crashes can be painful and even serious.

Quoted message said:

- Mad Dog is full of [censored].

Open wide, I've got another mouthful for you, Bobby!

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- They won't do anything for your spin.

I'm not so sure that's true. I do agree that spinning isn't an important aspect
of road racing, but efficiency is a nice thing to have. Some folks at least
think they benefit from spin training in that it teaches them to relax better
and a relaxed rider is more efficient.

Quoted message said:

- Rollers have largely been replaced by resistance trainers.
There are reasons for this.

I think the main reason is that you don't have to worry about falling off! Look
at all of the roller stands out there. One of the older dudes at the local
Performance shop says for every 10 rollers they sell, they sell 8 stands at the
same time and often see one or 2 of the others come back later for a stand. I
sold my rollers long ago and switched to a fan resistance model, then a mag and
finally to a Cateyemate. The old style fan units were loud and the load was
weird - not at all like the road. The good trainers now have a fairly heavy
flywheel - much nicer load. But it's even better do get something that spits
out numbers like watts, HR, etc. I'd like to get the Powertap if only it wasn't
so pricey...

Bob Schwartz says...

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No it isn't. Give it up.

Yes, it is.

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If no one here had ever crashed on rollers you might
be able to pass off this [censored]. But that's not
the case so give it up.

No. Not [censored]. Period.

don vescio says...

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Make sure that a plumb line dropped from the center of your front axle
is centered (or slighly) behind the axle of your front roller's axle.
Lots of wheel speed seems to help.

Don, Bob says that spinning bike wheels don't have any angular momentum, so you
must be wrong.

Colin Campbell says...

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Bob,
Is it just an old wives' tale that trainers wear rear tires quite rapidly?

Colin, it must be a lie. There are no forces generated when pedaling on rollers
or a trainer. Bob has proven this conclusively.

Move along, nothing to see here.

Mad Dog said:

Robert Chung says...

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Tom Compton collected these data on the speed-power relationship on
rollers:
http://www.geocities.com/almost_fast/trainerpower/tr_compton.gif

Quoted message said:

(That graph comes from this page:
http://www.geocities.com/almost_fast/trainerpower/ )

The roller numbers stop too low to extrapolate
a sprint velocity with much accuracy.

Looks pretty linear.

Mad Dog said:

William Asher says...

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He does claim to be pedaling at approximately 60+ mph.

Actually, the bike had no forward velocity until it came off the
rollers.

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Who knows, maybe the stripe was caused by relativistic effects.

No, no, no! Get it right - the sparks were caused by relativistic
effects. The stripe was caused by fear.

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I should have said: "I don't shoot off because a) I don't find riding
rollers all that erotic,

Trying to troll H2?

b) I don't pedal all that fast to begin with,

No wonder you're such a mellow guy...

Quoted message said:

and c) when I do fall off I have enough sense to stop pedaling and
look for something soft to land on.

Your mommy didn't let you play with the fun kids, did she?

If the stripe was caused by fear, it seems you invented the bicycling
version of a Cleveland Steamer. Maybe it could be named after you, the
Mad Dog Steamer.

I vaguely recall that h2 lives in Seattle and if that is so, I also
strongly suspect I have actually seen her in person on the BGT. Not that
has anything to do with anything here, I just wanted to point that out. It
is a sad fact that the only person I succeeded in trolling was you, which
is sort of like catching a cunner when you are going for bluefish.

The fun kids didn't want to play with me regardless of my mom's wishes, but
they're mostly fat and bald now so in a small way there is some justice in
the universe.

--
Bill Asher

Mad Dog said:

Your "no forward motion whatsoever" claim doesn't make physical sense. If
you're in a big gear and spinning, it's not unreasonable for the wheel to be
going at the equivalent of 40 mph and most folks I know can easily maintain 25
mph on rollers with no load unit strapped on. That's a fair bit of angular
momentum on the average bike wheelset. Are you saying that the angular momentum
of two spinning wheels just evaporates when you go off the rollers? It's gotta
go somewhere. Or did you develop a process to convert it into pizza? If so,
send me a veggie deluxe, light on the cheeze, very heavy on the garlic and
jalapenos because it's gettin' deep here and I want to contribute to the stench.

Physics Boy,
Okay, let's work out this "angular momentum" thing. Suppose my
wheels (both of them together) weigh 2.5 kg. Of that maybe 0.8 kg is
at the hubs and has negligible angular momentum. Let's treat the
remaining 1.7 kg as if it was all at the edge (rims and tires) at
0.33 m radius. Suppose I'm roller-riding at the equivalent of 30 mph
(13.4 m/s). The angular momentum in my wheels is, L=mvr =
1.7 kg * 13.4 m/s * 0.33 m.

Now I bunny hop off the rollers and onto the floor. Assume that
I stop pedaling, but my tires instantly grab the floor with perfect
traction, meaning no skidding, and convert that angular momentum
into linear momentum. This is unrealistic (there would surely be
skidding) but gives the maximum possible forward velocity.
The linear momentum is P=L/r = 1.7 kg * 13.4 m/s. But this
has to push the weight of me and the bike, say that's 85 kg.
I go flying forward at ... 0.27 meters/sec. That is 0.6 mph. At
this ferocious speed, I'd better be a damn good bike handler to
stay upright long enough to crash into the wall 7 feet away.

Robert Chung said:

William Asher said:

He does claim to be pedaling at approximately 60+ mph.

Tom Compton collected these data on the speed-power relationship on
rollers:
http://www.geocities.com/almost_fast/trainerpower/tr_compton.gif

(That graph comes from this page:
http://www.geocities.com/almost_fast/trainerpower/ )

So then 180 RPM for a 50x11 gives something on the order of 100 kph wheel
speed which looks to be around 1 kW.

Figure a 3 kg wheel and there are two of them going 100 kph and all the
mass is in the rim. I think that gives a total momentum of 600 kg-km/hr so
that if all that momentum were transfered to a 70 kg rider, he would be
going around 9 km/hr (5 mph). That's around 2.5 m/s, meaning it would take
about 2 s to lay down a 7 foot long skid mark.

mississippi-1 mississipp-2

That's plenty of time to figure out something was a little off and stop
pedaling.

--
Bill Asher

Mad Dog wrote:
[snip]

You know, you're starting to remind me of someone else.

Bob Schwartz

Mad Dog said:

Quoted message said:

I want to contribute to the stench.

To which Ben replied:

Quoted message said:

Physics Boy,
Okay, let's work out this "angular momentum" thing. Suppose my
wheels (both of them together) weigh 2.5 kg. Of that maybe 0.8 kg is
at the hubs and has negligible angular momentum. Let's treat the
remaining 1.7 kg as if it was all at the edge (rims and tires) at
0.33 m radius. Suppose I'm roller-riding at the equivalent of 30 mph
(13.4 m/s). The angular momentum in my wheels is, L=mvr =
1.7 kg * 13.4 m/s * 0.33 m.

Now I bunny hop off the rollers and onto the floor. Assume that
I stop pedaling, but my tires instantly grab the floor with perfect
traction, meaning no skidding, and convert that angular momentum
into linear momentum. This is unrealistic (there would surely be
skidding) but gives the maximum possible forward velocity.
The linear momentum is P=L/r = 1.7 kg * 13.4 m/s. But this
has to push the weight of me and the bike, say that's 85 kg.
I go flying forward at ... 0.27 meters/sec. That is 0.6 mph. At
this ferocious speed, I'd better be a damn good bike handler to
stay upright long enough to crash into the wall 7 feet away.

Thank you Dr. Science. I read this morning about the $871M in bonuses that
the UC system is distributing to good employees. I hope you are getting some
of that. Tax dollars well spent IMHO!

Mad Dog said:

Mark Fennell says...

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I don't think physics is MadDog's strong suit.

Just shows how flawed your thinking is - or rather, it exposes your
inability to
think in a reasonably coherent manner.

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Remember, he's the one who says shaving a few grams of wheel weight will
save a couple minutes on an hour-long climb.

Numbers are apparently your weakness.

Ha! That's *exactly* what my math professors used to say! It must be true.

Quoted message said:

And anyone
that knows anything about the effect of wheel+tire weight on significant
climbs
goes for light wheels if they have the means.

Personally, I'm not that in to climbing, so I don't really care anyway. But
thanks for the info nonetheless!

William Asher said:

mississippi-1 mississipp-2

That's plenty of time to figure out something was a little off and stop
pedaling.

Well, for most people anyway.

Mark Fennell said:

William Asher said:

mississippi-1 mississipp-2

That's plenty of time to figure out something was a little off and stop
pedaling.

Well, for most people anyway.

Ok, I think I found some relevant websites to explain what is really going
on:

http://www.open.org/davidc/index.htm

http://www.open.org/davidc/GITheory.htm

The explanation was right there all the time.

--
Bill Asher

Mad Dog said:

Colin, it must be a lie. There are no forces generated when pedaling on rollers
or a trainer. Bob has proven this conclusively.

Move along, nothing to see here.

If I told you that riders at constant power on a
velodrome accelerate in the corners, what would
you tell me?

Bob Schwartz

Bob Schwartz says...

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Mad Dog wrote:
[snip]

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You know, you're starting to remind me of someone else.

Is that your final answer?

William Asher says...

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Ok, let's up the difficulty, pedal at MadDog cadences, in the dark, on a
rolling ship, wearing VR goggles while playing Tony Hawk's Ultra
Skateboard Challenge.

Dammit Bill!! You force me to dock you 8 nanoseconds for not specifying the
tunes on your ipod playlist.

Mad Dog said:

Quoted message said:

Remember, he's the one who says shaving a few grams of wheel weight will
save a couple minutes on an hour-long climb.

Numbers are apparently your weakness. "Few" has been defined as between 3 and
9. I was talking about a much larger weight reduction than 9 grams.

Dumbass -

So, how many grams saved on the rim translates to 2 minutes?

just curious,

K. Gringioni.

[email hidden] says...

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That is 0.6 mph. At this ferocious speed, I'd better be a damn good
bike handler to stay upright long enough to crash into the wall 7 feet away.

No, no no! The skid mark was 7'. The crash site was 15'. If you're gonna get
all cutesy quantitative, the least you can do is read accurately.

You've made a few assumptions that skew your result to the down side. For
example, the combined body mass plus bike for me at that time was about 76 kg.
And although my solo on-road flat sprint max at that time was a bit under 40
mph, on rollers it was higher. But the big mistake your model makes is that
after my tires hit pavement, I was still pedaling intentionally (to generate the
7' skid mark), adding enough energy to the system to completely swamp your
flawed model. But if you look back, I never claimed a velocity and never
insinuated that it was like being shot out of a cannon.

I've also accidentally gone off rollers a couple of times - where I wasn't
intentionally trying to do a burnout or to ride away. I never managed to do it
without leaving some kind of skid mark (or carpet damage). Before I got exiled
to the basement, I put a skid mark on the kitchen vinyl floor. That was the
only reasonable place in that house to use a doorway to ride in. And realize
that this was long ago when I was using cleats and toe clips/straps. It's
totally different now when you can hit the brakes, pop a foot out and catch
yourself. 6 to 12" is not a long skid mark on a vinyl or painted cement floor,
even if you're not trying to leave one. I don't miss rollers, that's for
certain. Anyway, take your bogus model there, Physicus Fakicus, and shove it
where the sun don't shine.

Kurgan Gringioni says...

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So, how many grams saved on the rim translates to 2 minutes?

I'm not gonna take the time to go google out the sew-up discussion - do it
yourself. Look at it this way, though: many people that read here ride on wheel
sets that weigh over 2200g with tires - I see plenty of local people race on

Quoted message said:

2500g wheels. (All weights here without a cassette or skewers.) 2200g would

be like a Kycerium clincher with reasonably light tubes and tires. Swap to a
light set of climbing sew-up rims and tires and you could come in at about
1500g. I have a friend whose wheels plus tires weigh 1350g. So that 1500g
example is 700g less than 2200 and of that, the rim+tire weight loss is probably
on the order of 400 or more likely 500g. I'd have to go back and check, but
numerous people have ascribed a time penalty to static weight on long climbs,
but wheel weight is a greater penalty.

But you have to ask yourself a few questions about weight. First, is it dumb to
ride a superlight bike when you are carrying around a big wad of fat on your
gut? (Yes, if you want to go your fastest, it is.) Second, when guys like
Lance, Jan, Ivan, etc., go ride really light bikes, wheels etc., is it just to
advertise expensive items so dumbass racers will buy them? (That's not the only
reason - they ride them in part because there is a performance advantage to
weight reduction - and they see those advantages as being more important than
their potential disadvantages). And finally, do the guys and girls that diss
light weight bikes do it just because they are cheapscates? (And should they
therefore learn to steal wheels from Lance?)