It's been done.

Same with bicycles, just more weight and speed.

http://kreitler.com/images/fork_stand_bmc_3.jpg
Is the belt necessary in this setup?

Why? What is holding the wheels on the rollers? Whats stopping the back wheel from going down to the floor and the front going up over the top of the front one? If you remove the middle roller, thats what you'd get. the 3rd one holds the wheel in place front to back so that doesnt happen. You seem to assume that the bike will not tip up or down at all.

No, I don't think so. Theres some resistance of the front roller, but thats about all. I'd think removing the band would net about a 0 change. (A loose bike on a roller is different tho)

What is the "it" that has been done? (What are you driving at? What conclusions should be drawn from that video and applied to this topic?)

The front and back rollers have to spin at equal rates in order to have balanced angular momenti which allow for you to remain upright. Duh.

Steering is not the key to balance, it's absolutely the gyro effect. When I'm trying to track stand, I can turn the handlebars and shift my weight all I want, I'm still going down. That doesn't happen when the wheels are in motion.

But steering is key to the dynamic stability of which you speak.

In the configuration where the fork is secured, your balance is also secured, so no, the connection is unnecessary. It may mess with the power output, however, because you will only be turning 2 rollers instead of 3.

fixed

How much so? 1/3 less? Please elaborate. Not just you, anybody...

Small rollers have more resistance because they deform the tires more.

Is this an attempt at subtle humor, or are you serious?

Well, you're turning 2 rollers instead of 3, no front wheel tire friction or spoke wind resistance .... so it will be less resistance. Doesn't really matter though. Ride it and get a workout, and adjust your gears as you see fit.

I would expect 1/2 to 1/3 less power. I think most of the resistance from rollers is due to the deformation of the tire on the roller (thus, why small-diameter rollers offer greater resistance).

From Kreitler:

As the drum diameter decreases, the amount of resistance increases. This is due to bearing friction and tire friction. For a given wheel speed, smaller drums rotate at higher RPM’s than larger drums, producing more friction in the sealed cartridge bearings. Smaller drums also create more tire friction because the roller has a smaller contact patch and indents the tire more.

The 4.5 drums have relatively low resistance. Most riders can ride in larger gears and keep the wheel speed high with relatively low effort on the 4.5 drums. Higher wheel speed enhances balance and provides a greater coasting effect if you stop pedaling momentarily.

Combined with the Headwind Fan, the 4.5 models provide the widest range of workload of any other roller combination. For easy spinning or intense interval workouts, you can do it all with the 4.5 drums combined with the Headwind Fan. The 4.5 drums are the easiest for learning to ride rollers, too.

The 3.0 drums provide approximately 40% more resistance compared to the 4.5 drums, making harder workouts possible without the addition of the Headwind Fan but not allowing the easy spinning that the 4.5 rollers offer. The 3.0 rollers are a good choice when higher resistance is desired, and at a lower cost than the 4.5’s w/Headwind Fan combination. Some smaller, but strong riders (under 120 pounds) may still find that the 3.0's have too much resistance for warming up or for less intense rides. Higher weight riders have an easier time on the smaller drums because the inherent resistance of the drums is lower, relative to their power output.

The 2.25 drums have approximately 90% more resistance compared to the 4.5 drums. Only the strongest of riders are able to ride the 2.25 drums. The 2.25 rollers were originally designed for the USA Cycling Team when they were looking for smaller rollers for travel that also provided enough resistance for interval workouts or sprint warm-ups. If you do not routinely average over 20-25mph on your solo road rides, look to the 3.0’s or 4.5’s. Also, if you are a lighter weight rider (under 120 pounds), you may find the 2.25's too hard, regardless of your speed outdoors.

For a numerical comparison of the different Kreitler Drums and accessories, please refer to the Wattage Chart (will open in a new window). The Wattage Chart is for comparison purposes only. Your actual wattage produced will vary depending on body weight, tire pressure, wheel aerodynamics, and other factors.

And I stayed in a Holiday Inn a couple weeks ago. Interestingly, I feel that leaves me qualified to say that you're incorrect, especially as lean would change nearly nothing if you welded the headset strait (I'm also a year into a master's thesis on this topic).

No, but I've seen road bikes on the skinny side of 2x4s, that's pretty impressive. I know a few guys who don't do tight ropes, but do slack lines, maybe I can get one of them riding (not likely).

Point being, they don't turn for balance.

Now if you really want to have fun with your buddy....put a figure eight in your friends belt and get ready to run when they try to ride it......and go flying off to the left when they turn the wheel right. ;)

How do they do it? Is it tricky?

Are you saying that Fajens and the articles on his site are incorrect? Will you provide a link to your thesis when you publish?

there are two types of bicycle riders

those who countersteer and know it

those who countersteer and don't think they are doing it

They do both turn and lean for balance. It's done at a very low speed so turning mixed with leaning causes a lateral shift in your CG.

I suppose I can link my thesis if I can remember. I believe that Fajans is correct, what I disagree with is the conclusions of AngryScientist from those papers. Comments like the one about riding a bike with a welded headset are incorrect. Saying that you can ride without hands is very different from saying that you can ride with a welded headset. Without your hands your front wheel is still rotating a bit, even if it isn't your hands causing the rotation.


If you want to get a good primer on stability find either the work of Dr. Jim Papadopoulos (Cornell) (http://ruina.tam.cornell.edu/researc..._and_links.htm) (note, VERY DENSE) or Chronicles of the Lords of the Chain Ring (Dr. William Patterson, CalPoly SLO).

Comments like the one about riding a bike with a welded headset are incorrect

+1. Hogwash and off topic to boot.

I saw a bicycle tightrope rider on youtube. He had a really long 40 pound pole for balance. So I think he was mostly balancing himself and the bike with the pole.

I think you misinterpreted his post (#11). I think he read up on Fajan's site and it changed his mind.