Can't afford SRM or PT right now, other power measurement tools?

cbjesseeNH

Polar Power Sensor Kit worked swell on one bike and on a 1UpUSA trainer, which vibrates very little, but didn't work well at all on another frame with different chainstay geometry. Hence - off to eBay and Powertap on the way.

Where you can mount the Polar unit very parallel to, and just barely contacting, the chain when in small chainring/cog combination, it seems to work fine.

jws

This sounds like a good decision. Instead of spending the bucks for a trainer with power, just get a decent trainer now and get a PT when you can afford it. Then you have a trainer with power simply by using the PT on the trainer and you also have the PT for outdoor training and racing.

One added benefit is that you don't have to worry about accounting for differences between two different power meters.

RapDaddyo

I can almost hear the screams, "Oh, no!" already, but as I said in a different thread, I believe one can use a non-power equipped trainer to define interval levels and do interval training in all three of the levels that really matter (L4-L6 per AC's schema) -- who the hell needs a power meter to train at L1-L3. I have a Tacx Swing trainer (~$180) and I intend to test my theory tomorrow. I'll let you know the results. This will also give plenty of time to the nay-sayers to get all wound up to heap mountains of negatives on my suggestion.

RapDaddyo

Well, I've finished my testing and have drawn my conclusions. So that nobody gets too upset with what I am going to say, let me qualify my remarks as follows: "This is what I would do if I didn't have a power meter but wanted the benefits of training indoors with power." First, I think that while there are many benefits to training and racing with a PM, two of them are very powerful for training rides: (1) define training levels or zones for desired physiological adaptations; and (2) track progress over time in max sustainable power at different durations. Second, my comments apply only to my trainer, a Tacx Swing. This $190 trainer has a click-stop variable resistance setting and I did my testing in the 4th setting (3 clicks up from the least resistance setting). I used this setting because it allows me to ride at all of my usual interval powers (200w-400w) at my desired cadences (90-110) with gear changes only. IOW, I do like Ron, the guy in the rotisserie cooker TV commercial says, "Set it and forget it." The resistance lever is connected via a cable and can be attached to the handlebar, but I don't bother with it -- I just leave it on the floor.

With all the above caveats, here is what I discovered. First, there was a direct, but non-linear relationship between power and speed. Second, my training power numbers throughout the power/duration curve is well approximated by the formula, IP = .90xMP, where IP = Interval Power and MP = Max Power at a given duration. The durations I use are 30sec-3min = L6, 3min-8min = L5 and 10min-30min = L4. There's no mystery here -- this is basically my translation of Andy Coggan's schema to the full power/duration curve. I'm not invoking Andy's name as being responsible in any way for my approach. I'm just explaining how I got here. Converting this to my bike on the Tacx Swing trainer without a PM, the only change I would make is to use a .92 multiplier. Specifically, IS = .92xMS, where IS = Interval Speed and MS = Max Speed.

So, how would I use this information if all I had was a speedometer on my bike? I would do a few test rides to find my max avg speed (MS) at a few key durations spanning the L4-L6 range, say 30sec, 3min, 5min, 10min, 20min & 30min. I would then ride my desired interval set at .92xMS. Surely, there's something wrong with this approach, but I don't know what it is. Now, there's one obvious question. Why didn't I address L1-L3? Because I don't think I need a power meter or even a speedometer to ride at these levels. I think RPE or a HRM works just fine. This is less true (at least for me) in the important training zones, L4-L6. As I said above, I'm not giving anyone training advice. I'm just sharing with you what I would do and why. IOW, I'm advancing a thesis or theory that seems to work for me at my training power levels.

Rideastrong

RD - thanks for your info. After talkign with the wife i am going to just buy another good trainer for this winter (last one lasted 6 years, and only was warrentied once for a broken weld) and next year i will pick up the PT and build up a new wheel. In the mean time i found a local that has a computrainer that i will visit with and try out and check in with to see how my training pogresses over the next 6 months. Next year i will rebuild my training around the ideas and principles of power training vs just hr training. This fall i am going to see if the OTC in Colorado Springs has the Power Training Seminar that i can attend and learn a little more. But atleast waiting another year will allow me to do some research and figure out how to redo my training.

RapDaddyo

Good plan. Actually, I hope somebody chimes in with comments (good or bad) on my quick and dirty protocol for training with power on a trainer with only a speedo. As to the PM Clinic, I know there is one in Clermont, FL December 3-4, but I don't know about CO Springs. Given that CO Springs is USA Cycling's home base, it is only logical that they will have a power clinic there, but maybe not until '06. BTW, I think you may need to have your Expert or Elite Coaching License to attend.

Eldrack

I can't afford a power meter either so i go with a nice approximate approach using a Tacx swing trainer. Each resistance level on the trainer (magnet) is related to a certain force (nice little graph in the instruction book to work this out). Multiply the force of the magnet by the speed (convert to meters per second) on your cycle computer and you have power output. I got the trainer for 115 UK pounds.


How accurate this is I don't know and you have to know a tiny bit about physics to work out what power your producing but its worked for me so far.

RapDaddyo

That's interesting to know about the power conversion chart in the instruction book. Frankly, I have never looked at the book. I'll have to see if I can find it. I'd like to compare the computed power numbers with my actual power numbers at different speeds. But, let me clarify something about my training protocol above. My protocol doesn't require that one computes power or converts speed to watts. All you do is determine your maximum sustainable speed at a given duration (e.g., 20 mins) and use that as the basis for an interval session at that duration (specifically .92xMS). This also gives one a way to track progress because one's maximum sustainable speed at that duration will increase with fitness. The power equivalent is a "nice to know" but not essential to effective training.

F1_Fan

CycleOps produces a nice graph for the Fluid2 trainer showing the relationship between power/cadence/gear. I haven't checked it against my PT SL yet but the graph numbers match what I "feel" on a local test hill I ride (average power calculated at kreuzotter.de).

It's unlikely to be perfect but I think it's a good estimate for someone without a power meter.

Rideastrong

that is ok. I just ordered my club coach materials from Sam down in C-springs. If i need to get my expert to attend i will make plans to attend those clinics prior. I have alot to learn and am eager to do so. So this should be no problem.

RapDaddyo

If you move quickly, you can do the Expert Clinic in CO Springs in October and then attend the Power Clinic in FL in December. I'll be at both.

biker-linz

I happened to be passing and thought this might help you out:

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

Apologies if it's been posted already.

L.

__________________
MSc (Applied Sport and Exercise Science)
RST Associate Coach
ABCC Level 3 Coach
Doctoral Student (Physiology), University of Oxford, UK.
www.cyclecoach.com
www.science4sport.com

RapDaddyo

I had not seen that link. Thanks, Lindsay. I wonder if there is consistency from unit to unit within the same model line?

cbjesseeNH

Picked up a Powertap Pro hub built into a DT Swiss RR 1.1 32 2-cross DB-spokes wheel and a similar front wheel built with a Simano Ultegra hub, shipped 2nd Day Air from AirBomb.com for $965.66. Used coupon code TPM77 for 10% off. The full CPU, harness, software kit arrived with the wheels 5 business days after I placed the order.

I had doubts about Airbomb based on others' comments, but they tracked fine online and delivered as ordered.

CPU SN 504XX, does that seem to be recent production?

Do hubs have a SN anywhere?

Now to put on tires and install!