Tuesday, June 29, 2010

Velodrome News

First off, Boulder Indoor Cycling is selling off some of its demo bikes at crazy low prices.

Classes start up again on July 5th.

And track cycling will soon be "exposed" to us civilians. One of my favorite things about living in Boulder is the huge number of professional racers and bike industry bigwigs. Hopefully this event/series isn't too expensive or boring.

I also caught a rumor about another party at the velodrome for Bama's send off to Portland in a few weeks. Stay Tuned.

Saturday, June 26, 2010

Monday, June 21, 2010

Thursday, June 17, 2010

Thursday Night Ride

Hey everyone, the crew is riding dirty tonight. If you havent been in awhile, come tonight its going to be super prime weather, and sunny till like 9pm ! We meet at folsom field @ 7pm.

Im gonna have more fliers to give out, and any help spreading the word is greatly appreciated. BAC to the future Part IV is looking to be our biggest race ever, and weve recently added a ton of sponsors who are giving away a bunch of cool prizes.

Wednesday, June 9, 2010

BAC To the Future Part IV - Alley Cat Race - July 3rd

UPDATED - 06/17/10 (New sponsors IZZE, DVS, Snarfs) ; 06/18/10 (New Prize category, and Sponsor Baphomet Cycles)

Alley Cat Race, and Trix Competition

Race Starts at 2:30 SHARP so dont be late !!

Check back the night before for a map with all the checkpoint locations

Ohh and here is a link to the event on facebook so you can tell your friends



DVS - is giving away a pair of their new Cadence X DVS Shoe for the winner of the Race AND for the winner of the Trix competition.
The Top 10 races, and the Top 3 Trick riders are also getting prizes from DVS

Snarf's - (AKA best sandwich shop in boulder) is going to be giving away gift certificates to the top racers and the trix winner

IZZE Sparkling Juice - everyone who races gets a free IZZE courtesy of Action Marketing

Baphomet Cycles - New prize category added, the winner will be chosen at Bama's discretion. The prize is a pair of his new super durable no nonsense Pantagram knickers.

Meet at the Folsom Field Buffalo at 2:00pm

Fast Fucking Friday

Tuesday, June 1, 2010

Wheelbuilding Measurements etc

I recently re-read Jobst Brandt's book the Bicycle Wheel and it inspired to me make a wheel-related post (as well as hand-build some 36 spoke wheels with Mavic MA2 Rims). So I got on my computer and made some basic wheel building tools.

If you've ever built a wheel, you know that before you can begin, you need to calculate the length of spokes to use. I wrote some MATLAB code that calculates the spoke length you need for a given rim and hub combination. If you have MATLAB, then you can paste the following text into an m-file and run it as a spoke length calculator. Otherwise, if you are a computer nerd, I think that C & C++ are similar enough to MATLAB that you could modify the code to work as such.

%Peter's Spoke Length Calculator
disp('unless otherwise implied, all measurements are to be entered should be in mm, but typing "mm" afterward is not necessary')
disp(' ')
D = input('What is the Effective Rim Diameter? ');
disp(' ')
d = input('What is the Flange Diameter? ');
disp(' ')
WL = input('What is the Left Flange Spacing (Center of Hub to Center of Left Flange) ');
disp(' ')
WR = input('What is the Right Flange Spacing (Center of Hub to Center of Right Flange) ');
disp(' ')
S = input('What is the Flange Hole Diameter? (Usually 2.4mm) ');
disp(' ')
X = input('What is the Cross Pattern? (eg. 1 2 3 4; radial=0) ');
disp(' ')
N = input('How many Spokes? ');
disp(' ')
T = 2*pi*X/(N/2); %Spoke Angle
A = d/2*sin(T); %A = Spoke Position Offset
B = D/2 - d/2*cos(T); %B = Radial Component
C1 = WL; %C1 = Hub "Half Width"
C2 = WR; %C2 = Hub "Half Width"
LL = sqrt(A^2+B^2+C1^2) - S/2; %LL = Left Spoke Length
LR = sqrt(A^2+B^2+C2^2) - S/2; %LR = Right Spoke Length
fprintf('The Left Side Spoke Length Needed is %4.1f mm \n', LL)
fprintf('The Right Side Spoke Length Needed is %4.1f mm', LR)

The program works fine if you know all the measurements, and for most rims and hubs a quick google search will get you all the necessary dimensions if the manufacturer and model of rub and rim are known. But if you can't find the information online, or don't trust the source, then you must measure the rim and hub yourself. So I made a few metrics that show how to measure hubs and rims yourself, supposing you have an accurate set of calipers or a steady hand and a good ruler.

The flange diameter is measured from the center of a spoke hole on one side of the flange to the center of the spoke holes opposite that hole. So pick a hole and measure from the center of it to is opposite. To verify you are doing this accurately you should count 8 spoke holes between the two holes for a 36 hole hub, 7 spoke holes between the two for a 32 hole hub, 6 spoke holes between the two for a 28 hole hub, ... (N/4)-1 spoke holes for an N hole hub. The flange hole diameter is kind of hard to precisely measure so it is usually safe to assume it is 2.4mm.

A dimension that is particularly hard to measure, at least for rear hubs, is the distance from the center of the hub to the center of the left and right flanges. Here is one of many ways of measuring this:
Measure the OLD (over locknut distance -- which is usually 100mm for front hubs, 120mm for rear track hubs, 126mm for old rear road bike hubs, 130mm for modern road bike rear cassette hubs, 135mm for modern mountain bike rear cassette hubs, and can be all sorts of things for tandem & other unusual hubs), then measure distance "a" and distance "b," which is the distance from the end locknut to the center of the hub flange for both left and right sides respectively. The distance WL from the center of the hub to the center of the left flange is (OLD/2)-a and the distance WR from the center of the hub to the center of the right flange is (OLD/2)-b.

Another dimension that is particularly hard to measure is the effective rim diameter. The effective rim diameter is the diameter of the inner wall of the rim where the spoke heads sit. One way of measuring this is to drop a spoke nipple in the rim and measure the distance between the top of the nipple head and the outer rim diameter. I have done this by marking a spoke stuck down the hole into the nipple head then measuring the distance "x" from the end of the spoke to the mark. Subtracting this distance "x" from the outside rim diameter will give you ERD, the effective rim diameter.

Hope these are useful to someone.