cc_rider

Just a follow up.
My orginal question was how to get the data to calculate grade. The math part is easy.

August last year I bought a "Sky Mounti" inclinometer.
https://www.velimpex.com/about_inclin...t_inclinometer
Totally unnecessary purchase but a fun gadget to have. Cheap, simple and easy to install. Doesn't give me the average grade of a hill, but it gives the actual grade at any given point. Would be a good supplement to a GPS with altimeter. Couple minor disadvantages: it only reads to a 20% grade, and if I am wobbling and bouncing too much the bubble jumps around (that has helped me to ride steadier.)
Generally easy to use. Accurate enough for my purposes.

On the first time out, I used it check Hog Back Mountain near Leesburg, VA. Turned out it wasn't as steep (or as high) as I thought, between 12% and 15% for 1/4 mile and 10% to 12% for another 1/4. Later I confirmed it with topo maps. Gave me a better appreciation of the cyclists who tackle the "real" mountains.

GuitarWizard

My Ciclosport CM434 seems to work fairly well in the atltimeter/% grade department.

ericgu

This is a bit of a hobby of mine.

There are a number of ways of getting data:

1) Altimeter-based cycling computer (like a Polar 720, which I have). You can get a rough idea, but the resolution of the computer isn't very great, so the results won't be great.

2) GPS-based cycling computer. Better than the altimeter, *but* elevation is the least accurate of the GPS measurements, and it's easy to get in cases where you don't have a good view of the sky. If you can give your GPS a few minutes at the top and bottom, you will get better data. Collected in realtime, GPS data tends to be fairly noisy, and some gps units will interpolate if they lose signal.

3) Topo maps. I have TopoUSA from DeLorme, which is okay, though it has a terrible user interface and is slow. I have come up with similar data on it vs a gps-based cyclocomputer for a century - within at least a couple of percent. This will give you pretty good data on the overall climb *but* the road overlay may not be correctly aligned on the topo data *or* the road may be graded differently, so it's not great for trying to figure the maximum climb.

You could go to my website at https://www.bicycleclimbs.com, enter a climb, and then see what the statistics are. I pull elevation data from the USGS, which I think is the same source that delorme uses, with the same sort of problems. It's good at overall climbs and average gradient, not really worth much on maximum gradient. If you want to do this you'll need to create a login and then request the ability to enter climbs.

I have a couple of designs for building a direct-measuring instrument that would record the gradient the whole way up a hill, but I haven't gotten around to building them yet.

Silver Litz

I believe % grade is sin(x), as someone earlier said. A 45 degree angle will be a 70.7% grade and a 90 degree cliff would be 100% grade. This is NOT rise over run, that would be tan(x), tan(45degree)=100%. Grade, sin(x) is rise over linear distance travelled, or rise divided by the hyponeteus of the triangle. This makes sense as sin(x)*m*g is the vector component of the gravitational force with respect to the direction travelled.

bluecd

i go here https://www.gmap-pedometer.com/ to map out a particular climb im curious about. then i input the rise & distance here https://www.csgnetwork.com/inclinedeclinegradecalc.html and let it do the math for me.

cc_rider

Incorrect.
The industry definition of grade as used by traffic engineers, civil engineers, architects, etc. is RISE/RUN * 100 = % GRADE.
You can play with the angle if you want, but it won't be in accordance with the industry accepted standard. We have other definitions and standards that involve the angles.
PS I do this for a living. If I get it wrong, I can cost my clients big $$$ and could get sued.


Nice calculator. And good explanation. Thanks.
So ... how about that Woodburn Road

edzo

use Nasa worldwind, and zoom into your ride loop with
the 1 meter topo map overlay. then you have your rise and run
right at your fingertips. calculate and you're done.

Silver Litz

Thanks cc_Rider. It is good to have a professional road engineer to give a definitive answer. The reason for my assumption of sin(x), not tan(x) was from the following from Swain, D.P. Cycling: Uphill and Downhill. In: Encyclopedia of Sports Medicine and Science; https://www.sportsci.org/encyc/cyclin...ngupdown.html:


"As indicated in the following equation, there are three primary forces to be overcome in bicycling: rolling resistance, air resistance and gravity:


W = krMs + kaAsv2 + giMs

where W is power, kr is the rolling resistance coefficient, M is the combined mass of cyclist and bicycle, s is the bicycle speed on the road, ka is the air resistance coefficient, A is the combined frontal area of cyclist and bicycle, v is the bicycle speed through the air (i.e. road speed plus head wind speed), g is the gravitational acceleration constant, and i is the road incline (grade; however, this is only an approximation, as the sine of the road angle to the horizontal should technically be used)."

The way i was used in the equation would imply that it is sin(x). Rereading this citation, the author hints that "grade" is just an approximation for "incline" (and is a reasonable approximation for low angles).

bluecd

woodburn is a good one. sunday rides include taylorstown rd then stumptown rd back to back (brutal) with woodburn towards the end. if you havent tried taylorstown & stumptown and you like to climb, you should try to check them out.

cc_rider

No prob.
Architect, not traffic engineer, but I've laid out major sites, like shopping centers, office parks, apartment complexs and RV campgrounds.
Spent yesterday morning with a client trying to figure our how to get ramps on the site of an existing warehouse so they could drive trucks in at the 4 ft high loading docks.


Yep. There's a lot of misinformation out there.
Looks right for physics of power consmuption, but he misses the technical definition of grade, conflates it with incline.
Bad scientist, no tenure.

cc_rider

Haven't done Taylorstown and Stumptown yet, but I've heard about them. Usuall take Milltown back to Waterford.
Woodburn is just so easy to get to, since I'm on Dry Mill anyway. And I like the ride back on Harmony Church. Learned that route a few Reston Centurys ago.

cc_rider

The Sky Mounti works well for most riding, but the 20% limit is a minor annoyance.

For hills over 20% I've got a device that measures angles accurate to 1/2 degree. Just a pro quality plumber's protractor, but I've added a chart with all of the common slopes and their angles. I use it at work to measure ramps, roofs, sidewalks, parking lots, etc.
Carry it with me when riding sometimes, but to use it I have to stop and get off the bike.

Here's my reference chart. Set it up graphically on CAD and just listed the angles. The number after the % grade is the angle of the slope.

1% 0.6
2% 1.2
3% 1.7
4% 2.3
5% 2.9
6% 3.4
7% 4.0
8% 4.6
9% 5.1
10% 5.7
11% 6.3
12% 6.8
13% 7.4
14% 8.0
15% 8.5
16% 9.1
17% 9.7
18% 10.2
19% 10.8
20% 11.3
21% 11.9
22% 12.4
23% 13.0
24% 13.5
25% 14.0
26% 14.6
27% 15.1
28% 15.7
29% 16.2
30% 16.8
32% 17.8
34% 18.8
36% 19.8
38% 20.8
40% 21.8
42% 22.8
44% 23.7
46% 24.7
48% 25.6
50% 26.6

bluecd

harmony church is one of my favorites also. especially the recently paved section. there are a couple long decents where you can really fly. it's getting a bit crowded with car traffic but it's worth it.

cc_rider

I like Milltown from Lovettsville to Waterford. The views are great, and there's not too much traffic.
Other favorites out there are Mountain Road to Irish Corner, and Lincoln Road to North Fork.

Is Taylorstown and/or Stumptown bigger than the Saint Louis Road at Goose creek? That's a BIG hill at the Notre Dame Academy.

NomadVW 

Anyone own that inclinometer that was listed before from Velimpex? Looking to find the mount diameter. Don't know if it will fit the oversized bars on the roubaix.

VW

cc_rider

Do you mean the Sky Mounti?
If so, then yes. I got mine last August. Velimpex is a distributor, but other people carry it too.
About $25. Doesn't take up much space. The mount is a 2-piece with 2 screws. Looks like it can fit over a pretty big bar, I have it on the fattest part of mine and still had to use the shim-pad.