Hot answers tagged

35

CO2 charger cartridges are used for bike tire inflation because they are a common, inexpensive product that has been around since the 1950s. Their other uses include powering air guns and inflating life vests. They were originally developed by the Crosman Corporation and marketed under the name "Powerlet". Powerlet cartridges are filled with CO2 presumably ...


26

I believe you will find these articles informative: The hidden life of a CO2 cartridge [PDF] The CO2 Cartridge … an Under-Appreciated Marvel of Technology! — George Fox Lang [PDF] At room temperature (below the 31°C/87.8°F critical temperature) a CO2 bottle is to a practical extent self-regulating. This is not possible with simple compressed air. You ...


21

Physics! Landing big jumps is all about dissipating the inertia that pesky old gravity has created on your trip back to earth. The better you dissipate that inertia, the better the chance that you wont kill yourself. There are several factors in play here: The Transition of the Landing.The landing is almost always sloped downwards. Combine forward momentum ...


17

Get an inclinometer. They're not particularly accurate, but readout is instant and the price is right.


17

The increased weight of the larger wheel (if indeed it does increase) will of course add weight to the bike, but additional weight adds very little rolling resistance (though it does of course affect hill climbing). It is a myth that "rotating mass slows you down". In terms of top speed there's no difference between weight on the wheel rim and weight ...


14

The three-foot extension noodle is absolutely obnoxious and a genuine safety hazard (for starters, how is another cyclist supposed to safely pass her?). The original point of these noodles, as I've seen them, is to cut one as wide as the widest part of your bike so cars could better gauge how much distance they needed to pass you. Perspective distortion and ...


12

Assuming you want the center of gravity of the bike alone (not with a rider), there is a very simple procedure you can perform yourself, as long as you have some bike (you could borrow one): For simplicity, strap the front wheel to the down tube of the bike, so the handlebars won't turn; You could also strap the brake levers in the "full braking" position; ...


12

You don't quite supply enough information in your specific question (that is, "50RPM for 10 minutes with 39x23 with 10% hill") to provide a full answer in absolute terms but, if we assume you're riding a standard sized 700c bike there's enough information to make a good estimate in relative terms. First I'll give a short answer, then a rule of thumb that's ...


12

The answer is "both, depending." The majority of current bicycle cyclometers use a reed switch and timer, and measure the time between successive triggerings of the switch as a magnet passes by. An advantage of this method is its simplicity and low cost, though if the magnet is ill-positioned or if the rotational speed of the wheel is too high, the reed ...


11

Most of the Garmin Edge series GPS cycling computers can display grade. The Edge 500 and Edge 800 (not the Edge 200) have barometric altimeters to determine altitude. You can then change or add a display data field to show the current grade. Funny you ask as I just put added the grade as a display field this morning on a hilly ride. It updates the grade ...


11

You can do it, because your bike is connected to the ground. The work done when moving an object is proportional to distance and resistance force (which consists of air resistance and rolling resistance for bikes). The air resistance depends on air speed (ground speed + wind speed), but distance depends only on ground speed. Going slower reduces the energy ...


9

Your opening claim: Everyone knows (citation needed) that (at fixed rim diameter) tyres with smaller section require less effort to move around (at least on a paved road). Is actually not true. Your next claim isn't true either. The contact patch area for a tire will be nearly the same regardless of what width tire is used, for a given pressure. If I ...


9

After reading the answers here and becoming more curious, I found this article, which agrees with @Daniel. to briefly summarize it, they found that at the same tire pressure the narrower tires deflected more and had a lower stiffness (force over displacement) A curious finding is that a difference of 1 bar (14psi) makes more of a difference that a 5mm tire ...


8

You can do this because of the gearing of the bike. When you're riding at a slower ground speed, if you shift to a lower gear to keep your pedal RPM the same, then the same force on the pedals produces a higher thrust at the tire. Even if you do not shift, it is easier to produce higher force on the pedals at lower RPM. The strength of a cyclist is ...


8

Yes, there has been tons of in depth analysis on this, and the equations are rather simple so you can answer the questions for yourself given different scenarios using the Equations of motion for cyling Assuming you are on a road bike, on a flat road, with reasonable tires, the vast majority of energy is overcoming aerodynamic drag, about 70-80% After that,...


8

This explains part of the reason in what may be too much detail:http://chemed.chem.purdue.edu/genchem/topicreview/bp/ch4/deviation5.html If you're going to read any of it, read the material starting after the table listing "van der Waals Constants for the Various Gases". It calculates that compressing CO2 from 1 Liters to 0.2 Liters using the Ideal Gas Law (...


6

Think of a cyclocomputer as a hardwired combination of a calculator, a quartz-clock, and a dedicated CPU working with a buffer. EDIT TO A MORE PLAUSIBLE ALGORITHM: Each time the magnet closes the reed-switch, a request is sent to the clock to capture a time-stamp, a time-stamped event is sent to a buffer, and the wheel circumference is added to the current ...


6

You are going at constant speed when the driving force from gravity Fg is equal to the drag (air resistance) Fd plus friction (rolling resistance) Ff: Fg = Fd + Ff When coasting down a hill, the driving force is the component of the gravitational force parallel to the road: Fg = m g sin(a) Here, a is the slope (angle with the horizontal), m is the mass ...


6

The loss is friction in deformation of the rubber of the tire. When you flex the tire from round (when not on the ground) to flat (when touching the ground) there is heat generated. If the tire is narrower and the pressure is higher, there is less rubber involved in the flexing. It is true that higher pressure means less contact patch, but that is not ...


6

The answer to your title question is "moving air exerts a force on obstacles", and deep section front wheels have more area affected by side winds so there's more force. In any crosswind there will be some side force that applies a turning torque on the front wheel of almost any bike (viz, zero rake bikes have been made, but they have less trail than is ...


6

Yay! Another physics question. Restating the question: if the rider power input is constant, does the bicycle velocity change if the drive-train gear ratio is changed? Let's assume the road surface, wind speed, gravity etc. all remain constant. Bike and rider are on a surface with no gradient. Short answer is that constant power results in constant ...


6

There are, but measurements typically will be protocol-dependent (and vary slightly between different wind tunnels). For example: Here is a link to a comparison done at the A2 Wind Tunnel in North Carolina almost a decade ago, on bicycles standardized to frame and wheels, but without saddle or handlebars. Other protocols may include saddles, handlebars, ...


5

You can use the calculator at http://bikecalculator.com, which will give you a reasonable estimate if you know the average grade of the hill, the day's temperature, and the wind speed/direction (probably not so relevant on a hill). A similar calculator is here so you can compare two methods. The website http://www.cyclingpowermodels.com has a host of ...


5

Wheel size is a trade off. In some ways, you want the wheel as small as possible, in other ways you want the wheel as large as possible. There is no "right" size really, except that it's handy to have the same size as everyone else so standards have risen up. The benefit of a smaller wheel is they are cheaper (less materials to make them), they have less ...


5

The answer is simple but the explanation behind the answer may be instructive. The simple answer is: the x-axis label should be read as (m/s)^2, not m/s^2. The longer explanation is related to this bicycles.stackexchange answer. The power needed to ride at steady speed on a flat road under calm wind conditions is Watts = Crr * kg * g * v + 0.5 * rho * CdA ...


5

Your question really seems to boil down to: Is using such a noodle illegal? What are possible outcomes if a driver still passes me too close? My answers to this; We don't know. This is something that most likely will be dependent on the laws of your country. So I would suggest you to find out something about "allowed transport techniques on a bicycle" ...


4

Another approach is roughly guestimate the CM, then tie 3 short cords to 3 points each roughly 120 degrees apart in a rough circle. Tie the other ends of the cords to a ring or whatever and hang so the bike is essentially on its side. Adjust the 3 cords on the ring -- looser or tighter -- until the bike hangs perfectly level. The central rope will then be ...


4

Others have already discussed GPS and GPS-enabled phones, altimetric barometers, and inclinometers. Bubble inclinometers (such as the Skymounti shown elsewhere among the answers) can be affected by acclerations so to get the best readings you should be stationary. dGPS (differential GPS) is used in surveying instruments to measure grades, but these are ...


4

Cell phones, usually not. Some applications will attempt to massage the data using elevation information provided from third-parties, but its a crapshoot at best. A dedicated GPS with a barometric altimeter is probably your best bet. I can't really speak to their level of accuracy, but it's certainly better than other practical options. If you just want ...


4

You mentioned KINETIC ENERGY, which obviously have to go somewhere. Sometimes you have reception, and the bike comes at speed, but sometimes, like in bike trial, the bike lands "flat" on plain concrete. Sometimes, too, freeriders land on flat concrete at speed, and at least the vertical component of the drop's kinetic energy disappears. I would say there ...


Only top voted, non community-wiki answers of a minimum length are eligible