# Feedback for my Science experiment

Discussion in 'Road Cycling' started by JessicaJ, Nov 13, 2011.

1. ### JessicaJ New Member

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I need your help and feedback....Please....I am conducting a science experiment about riding a bike up a 35 degree hill for 1/8 th of a mile. Which of the seven gears on your bike do you use on this type of moderate hill? How long does it take you?

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2. ### alienator Well-Known Member

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That would be an impossible hill for any rider, even a professional rider. When cyclists discuss how a steep a road is, we discuss like the engineers who design roads, that is to say that we discuss it in terms of slope. Slope is calculated a couple of different ways. Look at this drawing:

Consider the side c to be the road surface. Technically slope is the length of side a divided by the length of side b, or a/b. Now, you'll have to forgive me but I don't know what grade you're in or what math you've taken. Slope is related to the angle, in this case angle A, by something called tangent, where tangent(A)=a/b. Sometimes cyclists and other can get away with calculating slope as a/c, and that value is related to the angle A by sin(A)=a/c. For small angles the different calculations are reasonably similar up to angles of about 25Â°. Slope in terms of roads is typically given as a percent so, to get that you'd use either (a/c)*100 or (a/b)*100.

For road cyclists it's hard to say where things start to get real difficult since that depends on the rider, but let's say it starts at 8%. An 8% slope gives a road angle of 4.6Â°. At a slope of 15%, the vast majority of us are saying very unkind things about the road engineers and why they had to make a road so steep. The angle for 15% is 8.5Â°. The steepest road in the world according to the Guinness Book of World Records is Baldwin St., in Dunedin, New Zealand. It's slope is 35% which is a road angle of 19.3Â° Canton Avenue, in Pittsburgh, Pennsylvania does hit 37% (an angle of 20.3Â°) but that's over a very short distance compared to Baldwin St.

An angle of 45Â° would give a slope of 100%. An angle of 70Â° would give a slope of 274.7%. Not only do we not have gears low enough for such slope, but because of the high angle the rider would fall down the slope.

To give you some perspective, a 70Â° mountain side is one on which most mountain climbers use ropes to protect from falls and special equipment to make it up the slope.

3. ### JessicaJ New Member

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what I meant was if a right angle is ninety degree than a hill that is about 1/3 of that. I mean I am only a sixth grader and I really do not understand you. Your triangle to me would be a 45 degree hill. But thanks at least you replied. I need at least four people to give me an answer my test have been in 2nd, 3rd and 4th gear and my results so fat in 4th .

4. ### alienator Well-Known Member

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I'm sorry.

I would use 7th gear, the easiest one to pedal.

5. ### kdelong Well-Known Member

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I understand what you are asking now. For a small incline like that, I normally ride in the middle of my gears. The bike that I usually ride has more than 7 gears, but if that is what I am limited to, I would say 3rd gear. It takes me about 4 minutes.

6. ### davereo Well-Known Member

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7th gear five minutes.
Good Luck Jessica

7. ### maydog Well-Known Member

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Alienator was spot on with his analysis of slope. It sounds like you are asking about a 30 degree angle or greater than a 50% grade. I found some references for you on slope and what a 30% grade looks like.

http://en.wikipedia.org/wiki/Baldwin_Street,_Dunedin

Moderate hills are much less steep. The killer hills around me have an average 6% grade or about 3.5 degrees.

Riding 660 feet (1/8 of a mile) on a 30 degree incline amounts to almost 400 feet of climb. Four hundred feet is about the tallest climb I can find where I live. I have climed 400 feet in around 7 minutes - for your hill I would be in the lowest gear possible or probably get off my bike and take the stairs.

8. ### swampy1970 Well-Known Member

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What alienator was pointing out was that there is a difference between measuring the angle of the slope, say 8.5 degrees or the measurement that people commonly refer to when they're out driving or riding which is the "gradient" or grade - for that 8.5 degree angled slope you'd often see a sign on the side of the road somewhere that says 15% grade.

The only place you'll likely find something as steep as a 45 degree angle with something that resembles a ridable path is where the motorcross motorcycle guys hang out. You'd probably stand at the bottom and think "oh, heck no." Then again, if you're in sixth grade you may not have learned the full extent of "risk[SIZE= medium]â‰ [/SIZE]bad but can lead to an unhappy ending" and combined with your lack of bodyweight will probably ride up the thing like a mountain goat trotting up the side of a mountain for lunch.

The velodrome in Manchester, England has a banking of 42degrees. A little steep, no? The dark blue section to the right is flat.

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10. ### Myosmith Member

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Assuming you are not using pre-existing momentum to aid in ascending the slope, you would have to use the lowest gear possible. As mentioned 35 degrees on a road is an incredibly steep slope. Many passenger vehicles would have difficulty climbing that steep of a grade. A "moderate" slope would be more like 5 to 8 degrees.

Great idea for a science project. I hope you do well.

For some extra points you might want to talk about the variables that affect a cyclist's climbing ability such as road surface (climbing a paved road is far different than climbing dirt, gravel or turf), wheel diameter and tires (mountain bikes designed for climbing generally have smaller diameter wheels and more aggressive tire tread) and gear ratios (seventh gear on a racing style road bike has a different ratio than seventh gear on a mountain bike set up for steep climbs). It would take a lot of data to actually cover all of the variables in your project but just expressing an understanding that they exist and how they effect the outcome will score big points at your grade level. Look up information on mechanical advantage of wheel diameters and pulley ratios (sprockets on a bicycle are really nothing more than pulleys modified to work with a chain). It sounds more complicated than it really is. The basic concepts are actually fairly easy to understand if you don't get hung up on the math right away.

11. ### An old Guy Member

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I like the term "modest hill."

For a modest hill I seldom shift and so gear 4 would be reasonable.

If the hill is the steepest hill around, I would use the lowest gear I had. That would be 1. I would use that gear because it would require less force to turn the pedals.

1/8 mile long hills around here take me 1 or 2 minutes or so to get over them.

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