Trainers



RapDaddyo said:
Can you create enough resistance to do L4-L6 intervals? I owned rollers a long time ago, but I had no ability to create resistance so it was good for spinning and learning to ride smoothly but not for simulating road resistance.
Absolutely and the "Killer" head wind/fan unit is required for resistance. I've the 4" Alloy rollers and there's little resistance without the fan unit. I got mine (with fan unit) at Velo Swap back in '95 (~$250) or so - they're in great shape.

RapDaddyo said:
Well, in general, I agree with you. But, I think a trainer at less than $300 can be a good solution to riding structured high-intensity efforts if one doesn't have a PM. And, that discounts the benefits of being able to train any time, any day.
I agree completely. We just need to balance structure with the "fun" part of training. After so many years of riding in the basement I felt that my mind had turned to mush.
 
RapDaddyo said:
Depending on where one lives (e.g., apartment), the noise can be an issue (e.g., neighbors). But, the primary goal is consistency of power/speed relationship for the duration of a typical interal (e.g., 20mins). Since my assumption is that the rider does not have a power meter, it is essential that the power/speed relationship remains constant. A 10min warmup is probably acceptable to most users, however. I'm really trying to arrive at a good answer to the question I am often asked, "I can't afford a power meter now, but I want to structure my training as precisely as possible. What can I do?" The answers now are HRM or RPE or a hill with constant grade. All three options are fairly error-prone. I'm trying to develop another option.

If someone is going to buy a trainer, the Kurt Kinetic fluid trainer is an option to consider. They are a little more expensive than some other fluid trainers, but have the advantage of 1) NEVER leaking - (they use a magnetic coupling)
and 2) publishing their power as a function of speed curve.

This function is derived by precisely measuring the power requried to turn the flywheel at various speeds with an electric motor - supposedly accurate to a couple of percent.

They even sell a cheap ~$50 power computer that does the calculation for you and has a real time display. Useful if you want to watch your realtime power while doing constant power intervals. You could also just print out a chart of speed vs. power and use it to figure out what speed you need to do a particular interval at to produce the wattage you are aiming for.

Another option for someone with a Polar 720 or similar logging computer is to hook up a rear wheel sensor to record speed, and then with a little work in Excel you could compute your power at the Polar's 5 sec resolution.

Granted this is not as perfect as a Power Tap or similar, but way cheaper than a high end power meter and way more accurate than trying to base structured power intervals than heartrate or RPE.
 
Red2000SS said:
If someone is going to buy a trainer, the Kurt Kinetic fluid trainer is an option to consider. They are a little more expensive than some other fluid trainers, but have the advantage of 1) NEVER leaking - (they use a magnetic coupling) and 2) publishing their power as a function of speed curve. This function is derived by precisely measuring the power requried to turn the flywheel at various speeds with an electric motor - supposedly accurate to a couple of percent.
Has anybody tested this with a PT or SRM? How accurate is their power estimate? Does this estimate assume the unit is warmed up?

Red2000SS said:
They even sell a cheap ~$50 power computer that does the calculation for you and has a real time display. Useful if you want to watch your realtime power while doing constant power intervals. You could also just print out a chart of speed vs. power and use it to figure out what speed you need to do a particular interval at to produce the wattage you are aiming for.
Again, has anybody tested this unit against a PT or SRM?

Red2000SS said:
Granted this is not as perfect as a Power Tap or similar, but way cheaper than a high end power meter and way more accurate than trying to base structured power intervals than heartrate or RPE.
Precisely why I am interested. Not for myself because I have a PT SL. But, for others who don't have a PM and can't afford one yet.
 
RDO, have you looked at the 1UP trainer? It uses a mechanical friction brake without any fluid. http://www.1upusa.com/bike_trainer.html

Also, I can send you many interval files from my Kinetic trainer. They claim to have the biggest heatsink, etc. to help keep the fluid stable, but you can judge for yourself if it meets your selection criteria.
 
frenchyge said:
RDO, have you looked at the 1UP trainer? It uses a mechanical friction brake without any fluid. http://www.1upusa.com/bike_trainer.html

Also, I can send you many interval files from my Kinetic trainer. They claim to have the biggest heatsink, etc. to help keep the fluid stable, but you can judge for yourself if it meets your selection criteria.
Cool. I think the KK is a good alternative, especially if the power readout device is relatively accurate. I'm especially interested to see if the power/speed relationship is (1) consistent from ride to ride and (2) consistent from the beginning of a 20min L4 interval to the end (assuming a 10min warmup before starting the interval). Is it sensitive to tire/tire pressure? How accurate is their computation of power equivalency at speed/resistance? Do you have the power readout device? So, you can either send me some files or just tell me your opinion, whichever is easier.:D
 
Consistency from ride to ride is going to be tough. I have seen some variation there, either from tire/contact pressure or starting ambient temperature (in my basement). I use the PT, though, so that's never been a worry for me. The amount of drift probably depends on the power of the intervals, too. A 350w interval requires the heat sink to dissipate that much more heat than a 250w interval. Below certain powers, the unit may be pretty steady if the sink can handle the load.

I don't have the power readout device. Maybe I need to do a ride with a 100-600w ramp, ride 5 min at 250w, then another ramp, and repeat for an hour. My kids are just the right age that they like to 'assist' with that kind of thing.
 
frenchyge said:
Consistency from ride to ride is going to be tough. I have seen some variation there, either from tire/contact pressure or starting ambient temperature (in my basement). I use the PT, though, so that's never been a worry for me. The amount of drift probably depends on the power of the intervals, too. A 350w interval requires the heat sink to dissipate that much more heat than a 250w interval. Below certain powers, the unit may be pretty steady if the sink can handle the load.

I don't have the power readout device. Maybe I need to do a ride with a 100-600w ramp, ride 5 min at 250w, then another ramp, and repeat for an hour. My kids are just the right age that they like to 'assist' with that kind of thing.
Cool. Which one gets to use the bullwhip?;)
 
Before PM and trainers that provide wattage, no one really knew if their wattages were consistent from interval to interval or from one work out to the next, but somehow progress was made. Despite the heat and the drift, which isn't something I notice during use, I find the computrainer to be an extremely useful tool for intervals, particularly in ergometer mode. I can incrementally add wattage from week to week, like adding plates during weight training, which is helpful in measuring progress. Even with some degree of drift, I know that my work done this week is greater than that done the week before.
 
park said:
Despite the heat and the drift, which isn't something I notice during use, I find the computrainer to be an extremely useful tool for intervals, particularly in ergometer mode.
Isn't the Computrainer kind of pricey (e.g., >$1K)? If a trainer costs as much as a PM, it sort of defeats my purpose.
 
park said:
Despite the heat and the drift, which isn't something I notice during use, I find the computrainer to be an extremely useful tool for intervals, particularly in ergometer mode.
I'm surprised that's not something you notice. I noticed that my speed was higher on later intervals even before I got a power meter. Unfortunately, I was unable to delude myself that I was just riding stronger, so trainer drift was the only explanation. :)
 
frenchyge said:
RDO, have you looked at the 1UP trainer? It uses a mechanical friction brake without any fluid. http://www.1upusa.com/bike_trainer.html
Does anybody with a PT or SRM PM have experience with the 1UP trainer? Does speed (at a constant power) drift during the course of an interval (e.g., 20mins)? Is it consistent from ride to ride? How sensitive is the power/speed relationship to tire/tire pressure?
 
RapDaddyo said:
Has anybody tested this with a PT or SRM? How accurate is their power estimate? Does this estimate assume the unit is warmed up?

Again, has anybody tested this unit against a PT or SRM?

Precisely why I am interested. Not for myself because I have a PT SL. But, for others who don't have a PM and can't afford one yet.

I don't have a PT or SRM, so I can't provide any hard data for that. Maybe someone else who has access to a Kurt Kinetic and a real power meter can run some detailed tests.

I just thought the Kurt Kinetic trainer especially with the extra power readout would fit the niche you were trying to fill for someone who couldn't afford a power meter. Especially if they were alread looking to get a trainer to ride indoors - incremental cost is not much (~350 for Kurt Kinetic w/ power readout vs. 200-300 for cheaper fluid trainers with no power readout option.)

I think consistency (precision) is more important that absolute accuracy as you have alluded to. Absolute accuracy is only important if you want to compare your numbers to others. As long as whatever power measurement device is consistent from workout to workout -you should be able to do a FT test and design a structured program of appropriate intervals.

It is important to note that the power curve (which is used by the power computer) is strictly a function of rotational speed of the trainer's flywheel.

The manufacturer hooked up an electric motor and ran a series of tests recording the actual power required to spin the trainer at various constant speeds and then fit a curve through the data points to get the formula.

This should be pretty accurate for constant power intervals i.e. 2x20 @ 200W, since you usually try to hold pretty steady cadence.

You should try to eliminate as many variables as possible - use the same bike with the same tires inflated to the same pressure, tightening the trainers wheel against the bike's tire with the same number of turns, etc.

The Kinetic's power computer only knows how much power it takes to spin it at a certain rpm. It is not a direct measurment using strain guages as used by high end power meters.

The Kinetic power meter would report the same power output from two bikes as long as the speed maintained was identical - high end road bike with 700x23 tires inflated to 130psi vs. Pee Wee Herman bike with 2" knobby mountain bike tires inflated to 40psi. The road bike would actually take less power to turn the same speed.

Of course as long as you always rode your Pee Wee Herman bike, you could still design a structured program with it... :D

I think the only unknown variable is how much the resistance changes a function of fluid temperature. Supposedly whatever fluid they use does not change viscosity much over the normal operating tempurature of the unit.

I think most people would do a 5-10 min warmup anyway which should raise the temp and reduce this effect somewhat.

I still think this would be more accurate than RPE or heartrate and maybe a good solution for some people.
 
RapDaddyo said:
Has anybody tested this with a PT or SRM? How accurate is their power estimate? Does this estimate assume the unit is warmed up?
RD,

Yes, some independent PT data is available:

http://www.geocities.com/almost_fast/trainerpower/tr_kintic_road.gif

Similar data for other trainers is available on the parent page:

http://www.geocities.com/almost_fast/trainerpower

Incidentally, I have a Kurt Kinetic Road Machine trainer and ignore my Polar power sensor for indoor sessions (due to the known and much-discussed Polar issues with trainers) and derive power data from the rear wheel speed by using the known best-fit power curve of the trainer.

The next road bike I buy/build will have PT, but for now this works pretty well for me.

Berend
 
Red2000SS said:
I don't have a PT or SRM, so I can't provide any hard data for that. Maybe someone else who has access to a Kurt Kinetic and a real power meter can run some detailed tests.
frenchyge has a PT SL and a KK Fluid trainer and has sent me some data.

Red2000SS said:
I still think this would be more accurate than RPE or heartrate and maybe a good solution for some people.
Great post. Thanks for taking the time. And, I agree with your conclusion.
 
squidwranglr said:
RD,

Yes, some independent PT data is available:
Actually, this study is what gave me the idea in the first place. What this study did not do (at least explicitly) was to tell me if the power/speed relationship is consistent over the course of a 20min interval or consistent from one day to the next.

squidwranglr said:
Incidentally, I have a Kurt Kinetic Road Machine trainer and ignore my Polar power sensor for indoor sessions (due to the known and much-discussed Polar issues with trainers) and derive power data from the rear wheel speed by using the known best-fit power curve of the trainer. The next road bike I buy/build will have PT, but for now this works pretty well for me.
Thanks, Berend. I agree the KK looks to be a good solution for my purpose. I'd still like to get some input on the 1UP, but their published power data are remarkably similar to the KK Fluid. The thing I think people (who haven't ridden a trainer for high-intensity efforts) don't realize is the incredible mental toughness it requires to do these efforts. It makes road sessions fun by comparison.
 
RapDaddyo said:
frenchyge has a PT SL and a KK Fluid trainer and has sent me some data.
Actually, I have the PT Pro. The yellow hub intimidates the competition... :cool: