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29

There are several different types of power meter on the market and each measures something slightly different in order to make their estimates. In addition, the way that they measure what they measure has implications for their accuracy. Below I discuss what the major models measure, how they measure it, and the implications for accuracy. Power is the rate ...


11

Presuming you are doing a standing start and coming to a complete stop at the top of the hill. The simple requirement is you need energy to move your from the bottom to the top. Most of the energy required will be to raise potential energy of the payload (you and the bike). Essentially you will be creating kinetic energy (moving the bike) by converting ...


6

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 ...


6

I found this image of the first SRM power meter interesting: The crank is rigged up like a lever (rotating around the spindle) - the more forcefully you push the pedal, the more the strain-guage bends, the output of which is used as part of calculating wattage (as is better described in the other answers!) Many modern power-meters are essentially ...


6

Your question is simple but a full answer is complex. The simplest answer is to point to Part 2 (especially chapter 4) of Wilson and Papadopoulos (2004), or the recent review by Debraux et al. (2011), or the paper by Martin et al. (1998). However, even these papers do not cover approaches that take better advantage of the data available from modern bicycle ...


6

Mountain bikers regularly run these low cadences for very short periods, often at much higher power output. The issue as to causing damage to knees is more about the duration of the climb and how strong your stabiliser muscles are. (Too much time mushing causes chronic overuse problems, while weak stabiliser muscles can allow injury to happen), however they ...


6

Aside from pacing better, if your cadence drops to 40rpm for too long and you are in your lowest gear at maximal effort for the expected duration, then you could probably use at least a gear 2/3rds or less than you currently have so you are likely to be able to sustain closer to 60rpm. That's possibly not feasible on your bike, but perhaps a 29 rear cog at ...


5

According to the FAQ on their website: Note: PowerTap hubs must be laced with a minimum 2 cross pattern to avoid damage to the hub and maintain the warranty." That suggests that making the non-drive side radial could lead to warranty issues. Radial lacing does stress the flange more than tangential lacing so many hub manufacturers do not allow it. To ...


5

If I on one ride add 1 kg of weight to the bike, how much slower (in time) will I be? Assuming that you and your bike mass 100kg (in round numbers), an extra 1kg causes a 1% increase in weight, i.e. a 1% increase in the potential energy associated with climbing the hill. If your power output is constant, that implies a 1% increase in time. However ...


5

First, get 'Training and Racing w/ a Power Meter' by Hunter Allen and Andrew Coggan. So incredibly helpful in learning about your device. Second, use WKO+ for analysis. I have been using it for 4 years and it is fantastic. In reference to you question, I typically use the 20 min time trial as a good way of setting my training zones. After a solid warm up ...


5

There are some bike hubs containing an electrical motor inside. If you google "bike hub motor" and take a look at the images, you'll get the idea. I think these ones are ideal since they require minimal changes to the overall bike structure, allowing for normal riding if the motor is not working, and they don't burn evil oil: you just plug the bike to the ...


5

The short and most direct answer to your question is to use your power meter to pace your ride optimally and Alex Simmons, who has given another answer to your question, was too modest to mention that he is an expert in this and has developed one of the most sophisticated power pacing models for variable conditions. A longer answer is, to paraphrase Prof. ...


4

There is a new website/download/software package called TrainerRoad that will allow you to train with Virtual Power for the price of a Trainer, ANT+ stick, Speed/Cadence sensor and $10/month subscription. Checkout the compatible hardware page (linked on the main page) to see if you already have a trainer on their list of known power curves. If not the Kurt ...


4

Fundamentally, power meters all work by measuring force (or torque) and a speed. http://en.wikipedia.org/wiki/Power_(physics)#Mechanical_power P(t) = F(t) * v(t) In other words: Power = Force * velocity A pedal or crank based power meter will be measuring either how much torque is applied to the cranks. That combined with your cadence gives you the ...


4

The Flow appears to be quite consistent though, depending on the mode in which it is used, it can be quite inaccurate. Below is a plot of reported power for speed on the Flow, with each line representing a different "scale factor." All of these data were collected at a coast down calibration of 0, with the same tire, at the same ambient room temperature; ...


4

The Tacx Power measurement is accurate in terms of consistency, meaning 200w on Sunday is 200w on Monday, as long as your trainer is set up consistently. It is generally showing a higher number than most other Power meters. My Powertap and my Fortius, when run concurrently differ by about 10%. As for long term accuracy, I've had my Fortius three years. I do ...


4

I will presume you are asking about the types of trainers that one mounts one's own bike onto, and not a dedicated "bike" trainer such as a Monark ergometer or a CycleOps Indoor Cycle (ergometers such as these are used in exercise physiology laboratories and can be calibrated to be very accurate). Consistency and Accuracy of Speed Measurement Accurate ...


4

If you could find several long hills of different but relatively constant (and not too steep) slope, then determine the slope and your terminal velocity on each hill (assuming that velocity is below some safe speed), you should be able to do the math to determine aerodynamic drag (working on the reasonably valid assumption that rolling resistance is ...


4

I have actually used both 2 different sized solar panels and a lithium backup battery on Ragbrai. Whether any of these will work for you depends on: How many days long is your ride? How sunny will it be and how much time will you have to do a solar charge? How many devices you need to charge. For solar charging. The first lesson is you can not charge ...


4

The raw pedal force or torque data are difficult to work with but you can extract some information from them. First, note that Stages mounts the strain gages (or gauges) permanently to the crank, so the crank length is constant and they know what it is; that means that there is a one-to-one relationship between the kgf and torque columns. In this case, it ...


3

Jan Heine & crew at Bicycle Quarterly recently reported the results of their wind tunnel research. A summary is available online, but the full results are only available in the printed journal.


3

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 ...


3

The expense is usually due to the physical hardware needed. Somewhere along the way some device needs to measure the power output. But how? Well inside the hub seems like the most common version. Thus you need a wheel build around a 'heavier' hub to get this to work, and thus is never cheap. Polar had a power sensor I never could figure out how it ...


3

Given the same rider, same bike weight, and same climb-time, does your gearing affect power? Also assume that the climb is efficient, no slipping tires, normal pedaling, etc. Well, that depends on which "power" you are measuring :-). Obviously, the power exercised by the bicycle as a whole is the same - if it's moving at the same speed, it's ...


3

No, gear and gain ratios do not affect power. While you are correct in assuming that it would feel different to the rider, if the other three variables are equal, then the power rate will be the same. In this case, in an "easier" gear ratio, the cadence would require a significant increase to maintain the same climb time (speed) and if the rider is ...


3

Take a look at TrainerRoad.com to see if your trainer is on their list and you may be able to use a Speed/Cadence sensor with an ANT+ USB stick in your computer to use what they call "Virtual Power". They don't actually measure your power output, but based on known power curves of the trainer at given speed/cadence they run through some formulas to give you ...


3

MY first thought was MTFU and get fitter pedalling further. It might not be as hard as you think once you get used to it. However, for a 20k commute, definitely go with an electric hub motor. Loads available off the shelf. Easy to fit and use, very economical and reliable with low/no maintenance. Also nice and quiet.


3

Your weight is used for calculating your power to weight ratio (W/kg). Weight of bike/clothes/other gear is not taken into consideration. It is considered that these things weight about the same for every "pro" cyclist. So you should use your own weight because everybody else is doing that. This way you can compare your results with your competition.


3

Check out GoalZero, they make a bunch of portable solar products. While it's a little bit pricy they are quality products that will last. My buddy uses one when we are gone racing and have no access to electricity, and it works quite well for phones and other small electronics. I have also seen, but don't really know much about, people putting these on ...


3

At the time of this posting, the solar chargers out there aren't very robust, unless money isn't a factor. If you're going to be camping each night, try the biolite camp stove. I haven't found anything that can charge my iPhone faster and it's relatively cheap, much cheaper than a good solar charger. ...



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