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Direct drive vs wheel-on smart trainers - is it "worth it" to spend more?

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Direct drive vs wheel-on smart trainers - is it "worth it" to spend more?

Old 05-26-24, 04:00 PM
  #76  
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Originally Posted by himespau

In Zwift, not all people using Zpower have the semi-transparent trainer attached to their wheel. They just lack the lightning bolt next to their name in the nearby riders list, but there are fewer of them (why Zwift finally decided it wouldn't hurt their bottom line to remove them from the Zwift-run races - community races can have hardware requirements or not).
The only time Iíve ever seen the semi-transparent trainer is on the start line before a race. Is that what we are talking about? I just check for the lightning bolt ⚡️to make sure Iím not smashing myself racing a Z-Power rider 😂
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Old 05-26-24, 04:46 PM
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Originally Posted by PeteHski
The only time Iíve ever seen the semi-transparent trainer is on the start line before a race. Is that what we are talking about? I just check for the lightning bolt ⚡️to make sure Iím not smashing myself racing a Z-Power rider 😂
I actually wasn't aware that transparent trainer was a notation for zPower until RChung said it. I've seen it drug around the roads a few times, but very rarely.

Since I'm a C, I'm not as worried about ZPower racers at my teammates who are As who will see them go off the front at crazy sustained power (I did an A race once because my team needed finishing points and the guy who "won" it held 6 W/kg pretty steadily for the whole 45 minutes and was gone off the front after the start - he didn't seem to understand it was a points race, or couldn't push harder than that with his trainer, so I actually took some segment points from him). At the C level, if you go over power (whether that's real or pretend), you will cat up before too long and I don't have to race you anymore. Unless there are series points on the line for my team, I am just racing pixels. Cheaters (or bots in the case of indieVelo) or real people putting out real efforts, either way, it's a jersey in front of me to chase down. As long as I'm in a race with Cat Enforcement, there aren't quite as many sandbaggers blowing up the front of the race (and making me blow myself up chasing them).
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Old 05-26-24, 07:07 PM
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Originally Posted by himespau
I actually wasn't aware that transparent trainer was a notation for zPower until RChung said it. I've seen it drug around the roads a few times, but very rarely.

Since I'm a C, I'm not as worried about ZPower racers at my teammates who are As who will see them go off the front at crazy sustained power (I did an A race once because my team needed finishing points and the guy who "won" it held 6 W/kg pretty steadily for the whole 45 minutes and was gone off the front after the start - he didn't seem to understand it was a points race, or couldn't push harder than that with his trainer, so I actually took some segment points from him). At the C level, if you go over power (whether that's real or pretend), you will cat up before too long and I don't have to race you anymore. Unless there are series points on the line for my team, I am just racing pixels. Cheaters (or bots in the case of indieVelo) or real people putting out real efforts, either way, it's a jersey in front of me to chase down. As long as I'm in a race with Cat Enforcement, there aren't quite as many sandbaggers blowing up the front of the race (and making me blow myself up chasing them).
Iíve never seen anyone actually dragging one of those trainers along the road in the 4 years Iíve been using Zwift. Itís the kind of thing I would notice!

Iím a middling Cat B rider, which is a bit frustrating because I have zero chance of winning a Cat enforced race. Iím not a sprinter or a lightweight climber either, so I get well beaten over pretty much any course profile. I agree about racing pixels too. I donít really care if the guy Iím racing neck and neck is lying about their weight. But I try to ignore those who are really taking the piss!
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Old 05-26-24, 11:51 PM
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Originally Posted by himespau
IndieVelo has always required smart trainers as the source of power for ranked races (power meters are allowed as primary for unranked races) because it's so easy to cheat with a powermeter (just change the listed crank length or mess with the gain among other things for pedal-based for example). indieVelo has dual record on by default (I just connect both my trainer and my Assioma Duos and they both show up with all the extra data from the Duos displayed). MyWhoosh, after getting the UCI esports championships is getting a bit more serious about cheating, so that's why I've heard they're moving that way too.
That's interesting. So they allow Snaps but not on-bike PMs even when the latter can be validated. I guess it's obvious that I'm not au courant, and my interests in power data aren't the same as theirs.
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Old 05-27-24, 12:05 AM
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Originally Posted by PeteHski
Well you could also get a used Snap, which is a more fair price comparison against other used gear. It comes down to whether you want more consistent power data or slope simulation. The value proposition for a Snap is still as a relatively low cost Smart trainer, if you want the resistance control.
A friend was recently looking for a used Snap and at least on local sites and the fleabay he was seeing around $200. I just bought a spare Powertap for $150 from someone who was switching to pedal-based power. I've seen dumb trainers for $25.

But it's absolutely true that I value on-bike power data more because I live in a climate that allows me to ride outdoors the majority of the year, I don't do e-racing, I am interested in measuring actual CdA and Crr, and I do very little hyper structured training. So while I may not see the value proposition for a Snap, you've reminded me that others may very well be able to.
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Old 05-27-24, 02:59 PM
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I'm confused that they don't allow racers to use power meters. Is that because a crank based meter is going to read higher due to losses?
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Old 05-27-24, 03:26 PM
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Originally Posted by unterhausen
I'm confused that they don't allow racers to use power meters. Is that because a crank based meter is going to read higher due to losses?
I donít know if thatís the reason, but they do usually read higher. Mine did anyway by around 4-5%, which ties in with drivetrain losses. Enough to make the difference between being competitive and an also-ran in Zwift races.
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Old 06-15-24, 02:24 PM
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Originally Posted by PeteHski
I donít know if thatís the reason, but they do usually read higher. Mine did anyway by around 4-5%, which ties in with drivetrain losses. Enough to make the difference between being competitive and an also-ran in Zwift races.
Your crank power meter reads 4-5% higher than your trainer power meter?
My stages crank arm PM seems to be very close to my Snap (when calibrated w/ spin down). I've always assumed the crank arm power meter would be more accurate since there's fewer variables involved, and I just use that for Zwift and don't even hook up to the trainer PM.
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Old 06-17-24, 02:40 AM
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Originally Posted by msu2001la
Your crank power meter reads 4-5% higher than your trainer power meter?
My stages crank arm PM seems to be very close to my Snap (when calibrated w/ spin down). I've always assumed the crank arm power meter would be more accurate since there's fewer variables involved, and I just use that for Zwift and don't even hook up to the trainer PM.
Yes the crank power meter always read a little higher, as expected since my trainer (Elite Direto X) has an optical power meter measuring torque at the rear wheel. Drivetrain losses are typically in the order of 5% so it made sense to me.

In your case I expect your crank arm PM is more accurate and it's just coincidence that your Snap is reading a little high for power at the rear wheel.
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Old 06-17-24, 10:14 AM
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not being an mechanical engineer...wouldn't drive train losses be a constant? stating a % implies increasing losses as more power is provided by the rider.
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Old 06-18-24, 05:18 PM
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Originally Posted by spelger
not being an mechanical engineer...wouldn't drive train losses be a constant? stating a % implies increasing losses as more power is provided by the rider.
No. However, it's often convenient to treat them as *close to* proportional to power. For example, we think that drive train losses are close to proportional to chain tension, rather than proportional to the product of chain tension and chain speed (i.e., power). The "normal" range in chain tension is greater than the "normal" range in chain speed, so the relationship between power and chain tension tends to be higher than the relationship between power and chain speed, so using power as a proxy for chain tension is sorta kinda ballpark okay.
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Old 06-19-24, 07:48 AM
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Originally Posted by RChung
No. However, it's often convenient to treat them as *close to* proportional to power. For example, we think that drive train losses are close to proportional to chain tension, rather than proportional to the product of chain tension and chain speed (i.e., power). The "normal" range in chain tension is greater than the "normal" range in chain speed, so the relationship between power and chain tension tends to be higher than the relationship between power and chain speed, so using power as a proxy for chain tension is sorta kinda ballpark okay.
Ok, that makes sense. a more taut chain would exhibit more forces in the link bearings and require more power to overcome the increasing friction. thanks. (although i'm sure there is more to it than that.)
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Old 06-19-24, 08:59 AM
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As an aside, measuring chain tension and chain speed was the basis for one of the early on-bike power meters. The inventor originally used a pick-up from an electric guitar to measure the tension. Clever as hell. That power meter had problems but the idea was neat.
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Old 06-19-24, 01:26 PM
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I'm trying to imagine how a guitar pickup measures strain and failing. On a similar tangent, I was going to make a wheel dishing gauge that used a guitar string, pickup, and tuner. But I decided it was too silly.
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Old 06-19-24, 02:27 PM
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Originally Posted by unterhausen
I'm trying to imagine how a guitar pickup measures strain and failing. On a similar tangent, I was going to make a wheel dishing gauge that used a guitar string, pickup, and tuner. But I decided it was too silly.
In this case, when the chain passes by a magnetic sensor it generates a field that can reveal its vibration frequency. That frequency varies with tension.
https://patents.google.com/patent/US6199021B1/e
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Old 06-20-24, 05:33 AM
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Originally Posted by spelger
not being an mechanical engineer...wouldn't drive train losses be a constant? stating a % implies increasing losses as more power is provided by the rider.
As RChung explained, it is not a constant. Drivetrain losses are usually quoted as a percentage of power output in tests. My own simple testing of crank power vs hub power showed a pretty consistent percentage difference at different power levels. I measured the difference in power at 50W intervals from 100-500W.
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