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Jan
7
comment Does gear ratio affect Power?
Welcome to bicycles.stackexchange. Your answer applies only instantaneously. For climbs of nontrivial duration, power is limited by metabolic processes (mostly, aerobic). That is, what you've written is true for maximal instantaneous power but when climbing any nontrivial hill your power output will be decidedly submaximal. There are still boundary values on gearing that will limit power production but and long as you are reasonably far from those boundaries your limitation is metabolic, not either force-limited nor limited by the speed of msucular contractions.
Dec
25
comment Should flywheels on stationary trainers be replaced periodically to avoid catastrophic failures caused by fatigue?
The flywheel replacement from Computrainer is free. Replacing the flywheel is definitely a more economical option.
Dec
4
comment Will this power2max power meter be compatible with Cannondale Synapse?
Was this for a BB30 version of the Type S? The difference between the BB30 and the BB30A is that the "A" has 5mm of extra width on the left side BB shell. Check for clearance there.
Dec
3
comment Will this power2max power meter be compatible with Cannondale Synapse?
I presume you asked Power2Max? What did they say?
Nov
8
comment Should I be able to peel off a glued tire patch?
Regular glue contains no "vulcanizing" components. Vulcanizing occurs under high pressure and temperature (normally, around 170 deg C., or about 350 deg F). Regular patches adhere well because the adhesive is better. If actual chemical vulcanization were occurring, the adhesive and patches used for latex tubes would be different from the adhesive and patches used for butyl tubes since latex and butyl are chemically different.
Nov
1
comment Is rubber cement in stationery stores the same as in tire patch kits?
If actual vulcanization had occurred, you would not be able to peel a patch off a tube.
Nov
1
comment Is rubber cement in stationery stores the same as in tire patch kits?
Not exactly. There often is real latex in rubber cement, and the solvent keeps it in suspension. The solvent volatilizes away leaving the adhesive and the rubber behind. You can use the same rubber cement whether your tube is butyl or latex; different formulations of rubber cement will include different amounts of rubber and different adhesives but no chemical vulcanization occurs.
Oct
31
comment Is rubber cement in stationery stores the same as in tire patch kits?
See my comment above to the other answer about vulcanization. "Rubber cement" is an adhesive that creates an airtight bond, so it's the cement that holds air in the (butyl) tube, not the patch. The patch is there to hold the cement in place around the hole and to protect the cement from abrasion. The molds used in manufacturing are sprayed with a "mold release" (think: Pam cooking spray) so you can peel the tube out of the mold. That's what you're trying to remove when you abrade the tube with sandpaper before applying glue and patch.
Oct
31
comment Is rubber cement in stationery stores the same as in tire patch kits?
Vulcanization does occur in natural rubber when exposed to sulfur and results in a cross-linked polymer but 1) most inner tubes are made of butyl, which is a synthetic rubber made from petroleum (which is why ExxonMobil is one of the major producers of butyl rubber) and isn't cured with sulfur and 2) vulcanization of natural rubber occurs under both pressure and heat. A typical vulcanization process using natural rubber and sulfur (with accelerants) is done at around 170 deg C. (~350 deg F).
Jul
31
comment How much speed can I buy
If money were no object, you could spend it on a streamlined vehicle like the Delft VeloX. It has CdA < .02 m^2 and special $400 tires (that are good for perhaps 20 km of use) with Crr < .002. On a flat road and zero wind, at 140 watts and a total mass of 105 kg you ought to be able to achieve ~ 80 km/h.
Jul
31
comment How much speed can I buy
We have long known what it takes to go faster: either increase the power you can make or reduce the power you must make. If your power output is fixed, you're looking at reducing the power needed to overcome drag. That means reducing rolling resistance, aerodynamic drag, and efficiency losses. Compared to typical tires/tubes the best can reduce the coeff of rolling resistance from perhaps .006 to perhaps .0025. Drivetrain efficiency can be improved from typical 95 or 96% up to maybe 97%. Aero drag on a standard bike can be reduced from perhaps .4 m^2 to under .3 m^2.
Jul
28
comment Are Osymetric chainring and power2max Classic power meter compatible?
That was just an example -- there are other times when absolute accuracy matters. It's just that training typically isn't one of the uses for a power meter that requires very high data fidelity; that's why people have been able to train effectively without one. There are, however, things that would be very difficult to do without a power meter, and these generally require accuracy. An example is VO2Max testing with a ramp protocol, since the ramps need to be of known and equal size.
Jul
28
comment Are Osymetric chainring and power2max Classic power meter compatible?
Absolute accuracy (rather than relative accuracy) can matter depending on what you're doing. For example, if you are trying to estimate aerodynamic or rolling resistance, you'll need absolute accuracy across the range of speeds you're likely to experience.
Jul
20
comment Descending without braking: where's the sweet spot?
@StephanMatthiesen In almost all cases what matters is CdA rather than the separate components Cd and A. In general, you measure the total drag in Newtons or lbf, then convert that to CdA, then if you're really interested you measure A and divide to get Cd.
Jul
18
comment Is there a standard equivalent for effort between distance and elevation?
@TomSterkenburg We discussed how to calculate drag resistance in this stackexchange question: bicycles.stackexchange.com/questions/9938/…
Jul
16
comment Why are so many technical aspects of cycling so subjective?
There is testing but mostly it's not widely known. For your particular example, see here and here.
Jul
10
comment Swain Power-HR relation
Exactly, though you'll want to exhaust your anaerobic capacity or else you'll overestimate VO2Max. That's why VO2Max tests are usually done with a ramped protocol, and the estimates are done off the final step before failure. In your example, you don't want to use the average of 97kJ for 5 minutes, instead you might want to use the max power over the last minute of a ramped protocol (or another similar protocol where you've exhausted the anaerobic component).
Jul
10
comment Swain Power-HR relation
Ah, okay. The issue is that even if you have HR, you don't have stroke volume which is what you need to get cardiac output. However, if you know metabolic efficiency (net or delta or work efficiency are better than gross efficiency, but sometimes all you have is gross efficiency) you can go from work to get L of O2 consumed, so if you have total mass you can estimate VO2Max. So you don't really need HR -- Swain was using that because he didn't have power, but you do. So do a VO2Max-level power effort and convert directly to estimate VO2Max.
Jul
10
comment Swain Power-HR relation
Can you clarify your question? The Swain model is used to estimate power when you know heart rate, VO2Max, and metabolic efficiency. You appear to have power and HR. Are you trying to go backwards to estimate VO2Max, or metabolic efficiency, or something else?
Jul
3
comment Is there a standard equivalent for effort between distance and elevation?
It's complicated but not terribly so if you know power and speed. That's the basis for the "virtual elevation" approach for estimating cycling drag -- it converts effort (in terms of power and speed) into elevation gain.