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Power curves from rollers and trainer

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Power curves from rollers and trainer

Old 02-07-08, 07:20 PM
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Power curves from rollers and trainer

Thought some people might be interested in this. Last week my friend and I made some power curves on my rollers and trainer (Blackburn Trackstand Ultra), and the results are shown in the attached zipped Excel files. My friend has a powertap on his bike, so he rode the trainer and rollers, then we switched the pedals to mine so I could ride the rollers and see if there was a difference from our weights (I'm ~188, he's ~165). The whole point of all this was so I could make some power curves and calorie charts to use as extra info in my training sessions. We got pretty good results, with good curve fits on all the sessions.

We were a little surprised at how steep the power curve was on the trainer. It is fairly new, with only about 75 miles on it so far. Also, the rollers gave a predictable result, as the only resistance it has is the rolling resistance of the tires (proportional to weight and speed). We're going to do some more tests on these, as well as his Cycleops fluid trainer because he thinks that one is nowhere near as steep as my Blackburn. After seeing the curves I realize why it seems to take so much more effort to raise my average speed by only a couple tenths of a MPH on the trainer, as opposed to the rollers, which I seem to be setting new PR's on all the time.
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Roller_summary.zip (54.6 KB, 105 views)
File Type: zip
Trainer_summary.zip (55.1 KB, 82 views)
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Old 02-07-08, 08:11 PM
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Do you, perchance, have all six bearings in your trainer? These numbers are way higher than I get on my trakstand ultra. If the resistance seems grabby and not constant, take the resistance unit apart and oil the sliding flywheel plate at the axle and put some oil on the bearing tracks. Also, since the friction is proportational to centripetal force, and centripetal force is proportional to V^2, you should be fitting your curve with a cubic (Power = Force*Velocity ~= V^3). According to the literature, it should be about 350W at 25 mph with this setting.

I would like to do some training with power, but I don't have a powertap. Knowing the speed vs. power curve would help me immensely. I am glad you posted this, however, I don't think the one you published is correct. I know I'm strong (), but not strong enough to cruise at 25mph at over 1000W, and that was the speed I was holding for half an hour last night.
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Old 02-08-08, 07:42 AM
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Good point, I never checked how many bearings were in it, I just unloaded it and started using it. I'll check it out but I'm assuming its got the standard three because it came with three extra in a separate bag.

The results do kind of make sense though. My typical efforts for a half hour have been around 23 mph average on the rollers and 13 mph on the trainer. That equates to roughly 200W on the rollers and 170W on the trainer, both roughly equivalent. I also do notice a little harder workout on the rollers just by virtue of the much higher volume of sweat pouring off.

Thanks for the tips though, I'll be disassembling it this weekend to check it out.
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Old 02-08-08, 08:05 AM
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You are reading much higher than what the factory specifies.

Last edited by jcbenten; 02-08-08 at 08:12 AM.
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Old 02-08-08, 12:11 PM
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I should point out that what I said yesterday was bogus. My friction plate had some glaze on it - I remove it after it started grabbing randomly, which made it better, but now I am NOT going at 25 mph for half an hour.

I fixed it, and then I lowered the resistance by putting the three balls into the lower slots. Not really necessary - with the balls in the outside slots I was getting resistances that were on par with my former fluid trainer, but I wanted to center the chain more on my cogset and allow a spinning warmup, which wasn't really possible with my former trainer either.

Regardless, you are reading much, much higher than I am; even with the cleaned pad and all I am nowhere near 1000W at 25mph. Probably closer to 400W on the higher resistance setup, though I don't have a PT to test this. This trainer; I like the design, it looks good in theory and when it works, it works well... but it is a bit finicky. I've only had it for less than a week though, so maybe things will settle out after a bit. Mechanical mechanisms tend to do this. It's got a pretty good 5 year warrenty, so that's good. Not lifetime, but if I am still having problems with this after 5 years, well, time to get something different.
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Old 02-08-08, 12:35 PM
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I have a blackburn... this seems right to me.
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Old 02-08-08, 07:32 PM
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Well, my friend came over again tonight for another training session. Before that I disassembled it to check it out and everything appears to be fine. Its got just the three balls in it and they're in the inner holes. He rode the rollers tonight but when we were done we put his bike on the trainer to check the power again. Sure enough, we got the same results as the first time. He even tried to get up to 25 mph, but couldn't do it not even in a dead sprint. He maxed out at 22 mph and 900+ watts. It not like he's a weak rider either, he's a CAT-4 racer and well into his preseason training.

This whole thing has got my brain turning now. It seems like mine is really high resistance, Carus47's is about the same as mine (at least I think that's what he meant), but Brian's must be a lot lower resistance (unless he's superhuman). I may try to contact someone at Blackburn to see what they say.
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Old 02-08-08, 08:42 PM
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This is a comparison of the BB with all ball configurations, KK Road Machine, and BB Fluid. All curves use equations or data from manufacturer websites or customer service. I think something is not quite right with your BB. How many turns during clampdown do you use? When your done, does it spin down over several seconds or stopping pretty quick? How tight are you on the quick release? A few years ago I used to really clamp down on the QR and I was actually bending the hub. When I eased up, the resistance went down.
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Old 02-09-08, 10:06 PM
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Yes, mine has about the same resistance as cm02WZS6's. As far as jcbenten's graph, it seems really low. And as for the spin down time, it takes about 20-30 secs (i just checked). Also, I searched the forums for blackburn and found that a lot of people comment about the high resistance of the Blackburn.

https://www.bikeforums.net/showthread...ltra+blackburn
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Old 02-10-08, 05:37 PM
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jcbenten, thanks for the info. I couldn't find anything like that on the website, so I'm assuming you got that from customer service? The attached picture shows how my resistance curve compares to the ones you provided--its definately much higher and the difference is certainly not just due to manufacturing variability. To answer your questions, I don't think I tighten down too much on the hub. I go just past the point where it would stop moving on the circular sockets on the ends of the screws. Mine also takes about 20-30 seconds to spin down.

I think I'll try to contact their customer service and see what they think. From Carus47's link, it appears as though we're not the only ones who have these trainers with such high resistance.
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Old 02-11-08, 01:40 PM
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Originally Posted by cm02WS6
jcbenten, thanks for the info. I couldn't find anything like that on the website, so I'm assuming you got that from customer service?
Yes, I received the numbers from customer service. Comparing between the KK and BB Ultra, and I own both, the KK is definitely more difficult which matches my curve. However, I do not have a power meter to compare against.
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Old 02-11-08, 02:16 PM
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I am nowhere near superhuman . Probably closer to sub human...

Anyway, I've been hearing that there's been some issues with the friction plate. I sanded mine down and now the resistance basically follows the published curves (from Blackburn). The last time I did this, it was good for a little while (about 20 min of pedaling time, though it was only a very light sanding), then the resistance went down to basically nothing again. I've sanded it more aggressively this time, and hopefully the resistance doesn't fade again. My next session is tonight, and it seems to have held its resistance for 20-30 minutes already, so there is hope. I am kinda hoping that this is merely a breakin problem - perhaps there was a film of something on the brake material left over from the manufacturing process that is getting worn and burnt off.

How long have you all been using the trainer? I've had mine for a week now. I'm almost to the point where I give it another week and then return it and get a KK or something. I'm reluctant though because the whole reason I got this one was because of the frame. I have a BB fluid and the only thing wrong with it was it was unsteady holding my bike. The fluid unit was actually quite good. The BB ultra holds my bike steady like a rock and perfectly vertical.
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Old 02-11-08, 03:45 PM
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Since we're geeking out, plot your power vs. cadence. Your sweet spot is right about 97 rpm on cadence. Much over or under that and you fall off. I'd say about 85 rpm is near the bottom of your power range. I've felt the same thing about myself. I don't have any power gear, but I'd say from about 93 to 105 is my best pedaling range and anything outside of that is hurting me. It's pretty amazing how little of a window I feel good in.
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Old 02-11-08, 03:49 PM
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Power curves? I thought that was what Oprah called her love handles.
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Old 02-11-08, 09:13 PM
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Originally Posted by Brian Ratliff
I am nowhere near superhuman . Probably closer to sub human...

How long have you all been using the trainer? I've had mine for a week now. I'm almost to the point where I give it another week and then return it and get a KK or something. I'm reluctant though because the whole reason I got this one was because of the frame. I have a BB fluid and the only thing wrong with it was it was unsteady holding my bike. The fluid unit was actually quite good. The BB ultra holds my bike steady like a rock and perfectly vertical.

I have about 10 hours on the BB then my wife took it. The only real issue I had was some slippage in the first 5 or 6 hours. Just slipped occasionally and seemed to happen when it had been run enough to warm up. Once I got passed the first few hours/rides (I ride ~45 minutes a session), the slippage seemed to have diminished.

The KK is pretty solid feeling.
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Old 02-12-08, 12:47 PM
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After a week of futzing with it, I'm returning my blackburn trakstand ultra trainer. See the thread I started for my review of it: Blackburn Trakstand Ultra trainer sucks - a review.
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