Today I wrote up an excel formula to calculate moment of impulse of bike wheels.

I now have mathematical proof that B43's are boat anchors.

a math proof in excel? lets see matlab and latex

but I'm making it user friendly, so maybe you all can use it. Most people don't have matlab or mathematica, or the like.

Plug in values, get a number out, change the values, see how it compares. Provides a better understanding of which parts affect the resistance to rotation as much.

I know the majority of people don't care, but I like numbers behind things, rather than "oh, those are lighter."

paints a better picture for me.

my uncle is from Southampton,UK. had the annual 'burning of the Guy' for Guy Fawkes Day, with the Guy burned in effigy and fireworks.

of course my coworkers only remember the 'V for Vendetta' movie:

oh sorry, didn't realize that was your goal and i was mostly teasing. but that sounds cool. i'd be interested in seeing it.

haha silly matlab.

excel is just fun cause it looks insane.
had to configure a turbojet with afterburner analysis on it for propulsions.

i prefer matlab but most people have no idea of what you can do with excel lol

damn user friendly haha! its like using labview....meh.

im the same way, when someone (read: my gf) has a question and i answer it and explain why, they usually give me one of those "cool story bro" looks halfway through my explanation lol

today its fricken cold, idunno what happened after this hurricane, but this 41 feels a lot colder than the 33 i was in a few weeks ago.

also my iphone 5 is waiting for me at my house after a month of waiting and delays compounded by my stupidity and the 'cane

Don't worry about it, haha.

I'm cleaning it up a little, and making sure its computing properly. I'll probably post it as a google doc or something.

Last night was a birthday party for a friend at a local bar. Three hours of open bar. Poor life decisions...

Today I picked up a messenger bag at my school's bookstore.
http://bikeforums.net/attachment.php...hmentid=282191
Price tag was originally $80, picked it up for just under $20. Current backpack's main zipper is falling apart so I though, why the hell not?

We just started the momentum and impulse unit in physics ap haha

So you'll be able to make some sense of it, haha.

Done. Pretty interesting results. The actual numbers give it much more meaning.

Here's the link:
https://docs.google.com/spreadsheet/...pblZsZ1E#gid=0

I made it editable(I think, just download it, and let me know.), so plug in the various measurements of the fields asked to compare two different wheels.

Several assumptions were made, though they apply to both wheels, so the error would be proportional.

This doesn't consider spoke lacing patterns, some are minimally lighter/heavier. This actually assumes radial lacing for the sake of simplicity. If you aren't using weights you got offline, if you took the average of all your spokes and used that weight, the lacing wouldn't actually matter, and it would give you a correct value.

It simplifies the shape of the hub to be a cylinder with diameter equal to the hub flange diameter. This isn't too far from the truth, but as you'll if/when you play with the values, the hub has nearly no effect on the wheels resistance to acceleration because its so close to the rotation axis.

This also doesn't include tire weight, which actually has the greatest influence on the moment of inertia, point being, if you have a 500g wheelset, and then run thickslicks, you might as well run B43's and a decent tire. So this assumes you will use the same tire on both wheelsets, which in turn leaves it proportional, therefore negligible. The same goes for rimtape/veloplugs. It assumes you will use the same for both sets.


The numbers that I currently have in the form are pretty neat. I basically made the lightest wheel I could think of, and the heaviest wheel I could think of. A Kinlin XR-200 to a Novatec SL, with XL15 spokes, and alloy nipples, versus a 48h B43 to High Flange Phil with straight gauge spokes and brass nipples.

Results? The B43 resists acceleration as compared to the KinLin by nearly 100%.

Today I got 12-14 miles in before it got too dark. I miss daylight savings.

http://farm8.staticflickr.com/7123/8...d5b87078_z.jpg

Looks good Nagrom! yeah it would be pretty intense making it to where it was fully user friendly (such as drop down menus to choose each wheel set up and compare to an entirely other user chosen wheelset) but its still really good. damn those b43s.

my wheelset is probably average weight but my bontrager TR tubes and Ribmos dont help with my acceleration haha

Thanks.

But yeah, I chose the lightest and heaviest to give you guys something to compare to. If you're closer to .04, good stuff, if you're closer to .08, good luck.

Good stuff Nagrom

is it not 47% difference by the chart?

Thanks.

flip that ratio over.
That's saying the kinlins resist about half as much, meaning the B43s resist twice as much.

I just worded it differently.

Also, an interesting note: use whatever goddam hub you want, unless you're worried about overall weight. The resistance from the hub weight is nearly negligible in the grand scheme of things.

In fact, the spoke nipples make a lot more difference.

It's common sense, just put into numbers. The farther you get from the axle, the more you should be worrying about weight if you're worried about acceleration.

This makes a lot of sense.
Dura Ace and Ultegra wheels ride wonderfully and accelerate great- they have the spoke nipples at the hub.
It's another reason tubulars ride so well- the rim is lighter (and stronger).

Precisely. It's pretty amazing how much of a difference it makes.

20 alloy nipples, weighing .31g each, so... just over 6 grams, has over 3.5x the influence on the moment of inertia than a >260g phil wood hub.

But if you move them to the hub, bam, gone. nearly nothing.

Interesting choice of brake lever placement. How's that working for you?

really should be sleeping but i have to wait for my new phone to restore from the cloud

so i can play with it for god knows how long.

today i

http://farm8.staticflickr.com/7125/8...42a75b0133.jpg
Bike to vote. by miss_kaz, on Flickr