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Originally Posted by Dalai
(Post 18517718)
No mention if compatible with track cranks - only road and MTB cranks in the compatibility list.
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I could "measure" your power output by watching your effort. That doesn't mean it's precise, accurate, or repeatable.
Just because it has the words "Power" and "Meter" in the product name doesn't necessarily mean it does what you think it does. |
Originally Posted by carleton
(Post 18517822)
I could "measure" your power output by watching your effort. That doesn't mean it's precise, accurate, or repeatable.
Just because it has the words "Power" and "Meter" in the product name doesn't necessarily mean it does what you think it does. Does anyone know if the 4iiii power meter is a supply your own crank-arm business model. I ask this since there doesn't seem to be price differentiation for the Shimano 105 vs. the Dura Ace. |
Originally Posted by dunderhi
(Post 18518247)
Are you words of warning for all power meters, crank arm power meters, or 4iiii's power meter?
Does anyone know if the 4iiii power meter is a supply your own crank-arm business model. I ask this since there doesn't seem to be price differentiation for the Shimano 105 vs. the Dura Ace. |
Was designed with the intention you could self install, but at the moment you need to send in your left crank arm for a factory installation...
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Originally Posted by dunderhi
(Post 18518247)
Are you words of warning for all power meters, crank arm power meters, or 4iiii's power meter?
Does anyone know if the 4iiii power meter is a supply your own crank-arm business model. I ask this since there doesn't seem to be price differentiation for the Shimano 105 vs. the Dura Ace. Remember, there is a Power Meter that measures wind and calculates the power output :D |
Originally Posted by carleton
(Post 18519133)
Remember, there is a Power Meter that measures wind and calculates the power output :D
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Originally Posted by dunderhi
(Post 18519150)
I'm new too all of this power training stuff, so I wasn't aware.
Track events are (obviously) much shorter. So, you want more accurate data more often. This is why the SRM is the gold standard for track. It samples (or used to) as fast as twice per second, for the not tech folks. So for a Flying 200 or 1K, you get a lot better sets of data than you would with others. Also, I don't like the 1 crank arm power meters. Yeah, on the road, you can assume that the output will average out. But, on the track, during a standing start, you are getting half of the data. If you can afford it, get a PM that measures from the crank spider. I'm not sure what the word is on pedal power meters these days. Are they getting better? On paper, they are superior to crank spider PMs because they are closer to the source of the power (your legs) and they are measuring left and right data independently. Plus they are easy to swap to other bikes. |
Originally Posted by carleton
(Post 18519821)
Also, I don't like the 1 crank arm power meters. Yeah, on the road, you can assume that the output will average out. But, on the track, during a standing start, you are getting half of the data.
Crank based ones to allow you to use any wheel you want. |
Originally Posted by taras0000
(Post 18519869)
SRM is a one crank PM. What's the difference if you measure at the crank or spider? Hub based in theory should be the most accurate. Also lots of room to house internals, therefore more complex computer, therefore higher sampling rate.
Crank based ones to allow you to use any wheel you want. The right crank arm mates with the spider with 3-4 screws (depending on your model): http://store.srm.de/media/catalog/pr.../1/5/159_3.jpg http://store.srm.de/media/catalog/pr.../1/5/159_2.jpg But, I see what you mean. The left crank arm moves torque through the bottom bracket then over to the right crank arm which then turns the spider. (these aren't exactly track parts, but they work for the illustration) SRM Crank arms: https://c2.staticflickr.com/6/5122/5...a7732e53cd.jpg Plus bottom bracket: http://www.velodromeshop.net/images/...bktshi2700.jpg Plus SRM spider: http://cdn.mos.bikeradar.com/images/...p82-500-70.jpg Equal: SRM Power Meter |
Originally Posted by taras0000
(Post 18519869)
SRM is a one crank PM. What's the difference if you measure at the crank or spider?
Crank arm photo on the scales is my photo Carleton :) |
Originally Posted by carleton
(Post 18519821)
If you can afford it, get a PM that measures from the crank spider.
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Originally Posted by Dalai
(Post 18520077)
Crank arm photo on the scales is my photo Carleton :)
Originally Posted by Banchad
(Post 18520093)
I can't, so I'm making one(for my dissertation).
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Originally Posted by Dalai
(Post 18520077)
Sensors on the left crank only deforms the strain gauges when pressure is applied to the left pedal. With the sensors on the spider, pressure on both pedals deform the strain gauges on the the spider - hence measures deflection from both pedals.
Crank arm photo on the scales is my photo Carleton :) |
Originally Posted by taras0000
(Post 18522476)
This just brought about a big face-palm for me. It's so obvious. I don't understand how I didn't figure this out myself. Frankly it's just as accurate as a hub based PM, it just doesn't take into account the minimal losses from the chain.
This is why SRM is considered better than PowerTap (measures at the hub). This is also why the promise of pedal sensors was so high, because they were closer to the body than crank arm, chainring spiders, and hubs as a measuring point. Then there was the PM that measured in the cleat. I think the cleat is as close as you can get and reliably measure force in 2 directions (downstroke and upstroke). The Power Meter shoe could work. But it would be undermined by the straps that sprinters use. Because when you use straps, the force added is applied to the bottom of the pedal. Not sure how a shoe power meter could measure that. |
Hmm, I need to draw the system to really think this through, but assuming negligible damping, I don't think deflection of any component changes measured power enough to matter, since everything is deflecting at the same time. The reason you get lower readings for a power tap vs crank based pm is fiction losses in the chain. Probably tiny for a track bike. Power taps do have some aliasing effects because they measure time based instead of event based. Not sure how much it matters for sprinters, but it's basically negligible for enduros.
Eta: by same time I mean the time effects are too small to matter for classical mechanics. |
Originally Posted by taras0000
(Post 18522476)
This just brought about a big face-palm for me. It's so obvious. I don't understand how I didn't figure this out myself. Frankly it's just as accurate as a hub based PM, it just doesn't take into account the minimal losses from the chain.
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Originally Posted by carleton
(Post 18520260)
Good luck! Can you talk about it? What style? Where are you placing the strain gauges?
Predator circles its prey with new Major Track one-piece carbon handlebar & stem - Bikerumor What do you all think of these? |
Originally Posted by Banchad
(Post 18523111)
Predator circles its prey with new Major Track one-piece carbon handlebar & stem - Bikerumor
What do you all think of these? They solve a problem that already has better solutions. a price around $750 to $800, give or take. You’ll likely have stem length and bar width options since they’re all handmade. This is the equivalent of having a fixed, rigid car seat drilled into the floor of the car. No sliding, no tilting, no adjustments of any kind. |
Originally Posted by carleton
(Post 18523183)
A waste of engineering and money.
They solve a problem that already has better solutions. Why would you pay 2.5-3x the price of a comparable top-tier stem/bar setup to have no angle, reach, or bar tilt options? It's a bad idea. They introduced these back in like 2011. They are not popular for a reason. This is the equivalent of having a fixed, rigid car seat drilled into the floor of the car. No sliding, no tilting, no adjustments of any kind.
Originally Posted by carleton
(Post 18523183)
A waste of engineering and money.
They solve a problem that already has better solutions. TC |
Originally Posted by Banchad
(Post 18523111)
I can talk about it but I'd rather not until I actually know whether I'll be able to finish it for my dissertation deadline.
Predator circles its prey with new Major Track one-piece carbon handlebar & stem - Bikerumor What do you all think of these? if i was made of money i'd be all about those, for the cool factor. but i'd want to test out the shape of the bar, first, to see if i'd be happy with the sphinx position; i'd also probably wind up having different handlebars to travel with, since those might not fit into my travel bag; i'd also probably wind up maybe not using them on my next bike, since obviously you can't tweak the stem length and angle. i know a few custom carbon dudes who will wrap a Scatto bar to a carbon stem and smooth out the juncture. that's cool too. but in general, there's a reason that one-piece bar/stem combos haven't really caught on. if they were making sprint bars, madison bars, and road bars, they'd probably be a bit more successful. |
[MENTION=399402]Banchad[/MENTION] - looking forward to hearing more about it when you are able to talk.
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Originally Posted by Dalai
(Post 18523889)
[MENTION=399402]Banchad[/MENTION] - looking forward to hearing more about it when you are able to talk.
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Those predators will look nice, but Im sure will flex like crazy. They are aiming for 350g, when scattos are 380g for a narrow 37cm bar only. Not to mention all other issues with fit, however once you have all that set its not like it changes much.
But I bet they would look cool |
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