Road Cycling - Gradient of a climb

I'm not sure if there's a real answer for this, but here it goes:
There are two main hills around my house. One I'm mashing at 45rpm on my 39-23 config, and the other I'm spinning at 60rpm on that config. My speed is constant. Is there a way to find the gradient of those climbs.

You need to know altitude at top/bottom of the climb and the distance up the climb, or topo map,and figure it manually... or a bike computer/hrm that tells you the avg gradient on the fly..

cheers-
Jim

Check out the topo maps at http://terraserver.microsoft.com/advfind.aspx calc grade with distance and elevation

you can buy a small level from home depot or something, tape it to your bike -- making sure you're on level ground (garage, living room) and make sure the level is level at the time of rigging.

:)

I wouldn't do that cuz it'd be demoralizing on many of the climbs around here. I don't need to know that' it's 9% at the middle of a 20 miles climb :eek:

How would one determine the percent grade from the location of the bubble in the yellow water? Those little lines are just a reference, are they not? Most of the climbs I've done would send a bubble on most levels I've used to the top of the water in no time.
Were you even being serious?

Cole

How would one determine the percent grade from the location of the bubble in the yellow water? Those little lines are just a reference, are they not? Most of the climbs I've done would send a bubble on most levels I've used to the top of the water in no time.
Were you even being serious?

Cole
I've never done it, so I'm not sure, but I know there are levels on the market that will give that sort of info... some guy last weekend on the Copper Triangle ride had it.

I use National Geographic's Topo software to get info about my rides.

Here's (http://www-graphics.stanford.edu/~lucasp/bike-grade.html#Build) a link to a set of instructions on how to build your own gradiometer.

On the subject of National Geographic software, is it easy to put waypoints in and calculate pretty good distances, gradients, etc? I've been thinking of buying that software but wasnt sure if it does what I want it to do. Too bad you cant try it before you buy it.

cheers-
Jim

NG Topo... it's a pain in the butt to draw each path. I've not explored it much, but I've found no easy way to plot.

take the integral of the curve from one point to another. Find the derivative at any given point. That's the tangent of the slope.

I'm kiding.

Take the feet of the climb, divide that by number of miles, divide that by 5280 (feet in a mile)

So, if you're doing 2100' over five miles, that's roughly an average grade of 8%.

2100/(5*5280) = 7.9%

I just use: 50' of climb per mile = 1%. The numbers are easy enough to do in your head, for some people anywho.

There have been some interesting responses to this. I know this seems obvious, but you've got to be able to measure one at least two different things to calculate the gradient. The most direct would be to measure the distance in linear feet traveled and the difference in altitude between your starting point and your ending point. Your odometer function can provide you you linear feet, but then you'd nee a rather sensitive altimeter to get the second measurement. Another approach is to used the Euclidian geometric Angle-Side-Angle or Angle-Angle-Side functions. What you need to make the calculation this way is:
1. Standing at the bottom of the incline use whatever method available to you to estimate the angular degree of the slope. If you have access to an inclinometer it makes things a bit easier and more accurate. You could improvise one by using a school childs compass. Prepare the compass by turning it curved side down and directly across from the 90 degree point afix the string. Weight the string. Actually, nylon fishing line might be better. When the compass is held upside down, and level, the string should be hanging straight down and in line with the 90 degree mark. Now if you sight along the flat edge of the compass and raise the angle of the compass so the it is pointing directly at the summitt of the inlcine, have a friend note the number of degrees that have changed from the 90 degree mark. That is the approximate angle of the incline.
2. Measure the linear distance from the bottom up the inclined plane. Use anything with an odometer and just convert to feet.
3. Now the change in altitude can be determined by the A-A-S geometry.
In the equation altitude is 'c' (this is what we've got to calulate)
The measured incline will be 'C'
The distance you measured up the slope is 'a'
And the base angle is 'A' (which is 90-C)
(a)* sin (A)
c = -------------
sin (C)

After calculating 'c' simply divide it by a to get the gradient. Multiply the result by 100 to convert it to the more familiar percentage.

Example: Suppose you approximate a 5 degree slope using whatever method you choose. You measure the linnear feet to the top, it's 380ft.

The equation is 380 * sin A (A=85, that's 90 minus the 5 degerees measured)
divided by sin (C). So we have

380 * .17608
------------ = 66.771 (thats 66.771 feet of altitude change)
.95898

66.77 divided by the 380 linear feet of the slope gives a gradient of 18%

I guess either you can use the method outlined by Don, or if you are able to get the topographical map of the area (and hence altitude), you can use this nifty java Calculator (http://www.csgnetwork.com/inclinedeclinegradecalc.html)

How about using one of those watches that tells altitude? Never had one, don't know how accurate they would be. Does anyone know? I think Nike makes one marketed by LA.

if you're gonna spend money on an altimeter, you should put it towards a mountable GPS that can upload the ride data into your PC.

http://www.bikeforums.net/showthread.php?t=16264

I just installed a Specialized Turbo Pro Computer on my bike and it has an inclinometer built in. It's pricey (at about $95.00) but besides normal functions, it also has in therometer, altimeter and a digital readout thats large enough to see without my bi-focal glasses.