It's killing me but..........

[RapDaddyo]

I'm waitin' until you get your Lake Meade overpass completed so I can add it to my epic overpass riding resume.

I burned a lot of family matches getting out to the CA Death Ride last year, but sadly wasn't fit to ride.

We're working on it.

 

[Alex Simmons]

Whoa!! How cool is that? Alex, is that a custom flywheel? You must know a good machinist.

Yes but it wasn't me that built it.

It was a fellow I coached last year who came up with it. He actually has 2 or 3 flywheels left over, not used (and not with cut outs like this one). The balance is pretty good, there isn't much in the way of vibration.

The flywheel is a bit OTT but hell it's great for doing intervals. My indoor power = outdoor power on this baby.

By the way, it has a name - Thunderbird 7.

 

[RapDaddyo]

Yes but it wasn't me that built it.

It was a fellow I coached last year who came up with it. He actually has 2 or 3 flywheels left over, not used (and not with cut outs like this one). The balance is pretty good, there isn't much in the way of vibration.

The flywheel is a bit OTT but hell it's great for doing intervals. My indoor power = outdoor power on this baby.

By the way, it has a name - Thunderbird 7.

Cool! I also like the infinitely adjustable seat and bars setup and the adjustable crank arm length. Actually, that would make a great dynamic fitting bike. I continue to be amazed at the fact that most fitting systems today are based on static body frame measurements. I believe in dynamic fittings at FTP power coupled with CG analysis as a predictor of bike handling characteristics. Static body frame measurements can get you in the ballpark, but I would never set up my bike without a dynamic fitting process. However, I have yet to find a discussion of this approach. Cheers.

 

[gman0482]

That makes alot of sense RDO. If I understand correctly, you're saying that the form you have on the bike normally is different than the form you maintain at FTP or higher efforts, and that should be calculated into the fitting process ?

 

[RapDaddyo]

That makes alot of sense RDO. If I understand correctly, you're saying that the form you have on the bike normally is different than the form you maintain at FTP or higher efforts, and that should be calculated into the fitting process ?

Exactly. Specifically, the critical relationship of a bike fit is where your hips are relative to the crank. Most static fitting systems today are built on the LeMond fitting model, which positions the front of the kneecap precisely vertical to the center of the pedal hub. For LeMond, this was his optimal position for generating maximum power on the downstroke. But, this position is NOT the optimal position for all cyclists. I believe this relationship can not be "defined" for a given cyclist, but can only be "discovered" by a cyclist when pedaling at his normal sustainable power, when normal forces are required on the downstroke (the key part of the pedal stroke). It's sort of like a visit to the optometrist when he goes through a trial and error process of determining the correct adjustment to each eye. He changes the strength of a lens and asks, "Better or worse?" I think a cyclist has to go through a similar process to nail down the optimal position of the seat relative to the crank. After each change in seat position and with the cyclist producing the same target power, the question is, "Better or worse?" Once you have the seat position, the rest of the fit falls into place pretty easily because the torso length will largely define the position of the bars. I have even tinkered with a fitting seat concept where the seat is equal width from front to back rather than flaring at the back as a normal seat does. There would be a few different seats, varying in width to accommodate different sitz bones. Then, in the dynamic fitting, the cyclist can easily slide forward or back to search for his optimal position. The hard part is then to figure out where the cyclist's sitz bones were in his optimal position. I haven't figure that part out yet, but a good proxy is to position the crank horizontal and drop a plumb line from the front of the cyclist's kneecap.

 

[tonyzackery]

, but I would never set up my bike without a dynamic fitting process. However, I have yet to find a discussion of this approach. Cheers.

Check these guys out; if you haven't already. Would love to try it out to see how far off/close I am.

RETUL

 

[RapDaddyo]

Check these guys out; if you haven't already. Would love to try it out to see how far off/close I am.
RETUL

Thanks for the link. No, I wasn't aware of these guys. Their approach is very interesting. I especially like their first statement about their philosophy: "Bike Fits Must be Dynamic." About the only thing missing is an infinitely adjustable fitting bike jig like Alex's custom trainer. Now, if we could just use their data collection and software analysis to predict drag we would also have a system for diagnosing a rider's aero position on a TT bike -- a "virtual" wind tunnel. I may have to look up the guy in Las Vegas and try this out.

 

[Alex Simmons]

Cool! I also like the infinitely adjustable seat and bars setup and the adjustable crank arm length. Actually, that would make a great dynamic fitting bike. I continue to be amazed at the fact that most fitting systems today are based on static body frame measurements. I believe in dynamic fittings at FTP power coupled with CG analysis as a predictor of bike handling characteristics. Static body frame measurements can get you in the ballpark, but I would never set up my bike without a dynamic fitting process. However, I have yet to find a discussion of this approach. Cheers.

This is my bike fit specialist:
cyclefit services

Dynamic fitting is pretty important and Steve has a really cool adjustable bike for the purpose if not doing it on your existing bike.

 

[Alex Simmons]

Now, if we could just use their data collection and software analysis to predict drag we would also have a system for diagnosing a rider's aero position on a TT bike -- a "virtual" wind tunnel. I may have to look up the guy in Las Vegas and try this out.

Tunnel or field testing really is the only way.

Sometimes positions that "look" more aero, aren't. Or more to the point, aren't as fast.

 

[Sillyoldtwit]

Great to see you back in the fold RD, however, nothing has changed. I still don't understand more than half of what you're talking about. It's all Chinese to me. On second thoughts, maybe "Chinese" is the wrong word as I can read over 1000 Chinese characters (as used by the Japanese Frenchy ) Doesn't sound much, but more than 90% of the characters have 2 or more readings. In fact the character for life has more than 200 different readings. Mind you, ask any Japanese and they can only give you between 5 and 8 readings for said character.

Still, never did like maths or physics much.

I digress.

Now on to today's session on the CT. It lasted just 40 seconds!!

I have a special tyre for trainers on the back wheel which you can pump up to 120PPS. I pumped it up this morning in a darkish room, dark because it was raining heavily outside. Guess what, I pumped it up to 140PPS. After 40 seconds on the trainer there was an almighty bang which left my ears ringing for 3 hours or so. END OF SESSION!!

 

[Felt_Rider]

In similarity of RDO, I did 2 hours on the trainer last Saturday and may end up doing the same tomorrow based on weather conditions.

Unlike the similarity of RDO my effort was much lower.
I suppose my effort would be classified as junk miles. My IF was not too bad after the first 60 minutes, but the last 60 minute pulled the IF down to 0.66.

Keep working to get better right?

 

[lanierb]

Thanks for the link. No, I wasn't aware of these guys. Their approach is very interesting. I especially like their first statement about their philosophy: "Bike Fits Must be Dynamic." About the only thing missing is an infinitely adjustable fitting bike jig like Alex's custom trainer.

Actually I got Retul'd once and the way they did it was they had you on an infinitely adjustable fitting bike with a power meter/load device (not unlike a computrainer) attached. Not sure if the fitting bike was made by Retul or not though. The fitting bike was really cool though, as many (but not all) of the adjustments could be done via remote control, while you were actually riding! Every part of the bike could be changed, top tube length, seat tube length, etc. Then there's a camera watching you from the side and the Retul computer system superimposes a stick figure on your body (on the computer screen) and spits out a running calculation of the angles your body is making while pedaling. Very worth while.

 

[RapDaddyo]

In similarity of RDO, I did 2 hours on the trainer last Saturday and may end up doing the same tomorrow based on weather conditions.
Unlike the similarity of RDO my effort was much lower.
I suppose my effort would be classified as junk miles. My IF was not too bad after the first 60 minutes, but the last 60 minute pulled the IF down to 0.66.
Keep working to get better right?

I'd be kidding if I didn't say these rides are brutal. The 2nd hr is so hard at first I thought I'd never finish. But, yes, I agree you should do them initially at a lower effort. Try 75%FTP initially. I also find I need to get off the saddle about every 15mins to change my position. And, as I discuss in my bike room specs, I find that using a metronome helps me get through it. I try to keep my cadence exactly in synch with the metronome. I think the role the metronome plays is that it gives me something to focus on continuously. Maintaining focus in these rides is very challenging. I think if you do this ride once a week you'll be close to 91%FTP after a month.

 

[RapDaddyo]

I pumped it up to 140PPS. After 40 seconds on the trainer there was an almighty bang which left my ears ringing for 3 hours or so. END OF SESSION!!

Tyson, in all likelihood the tire didn't blow due to the pressure. That's what happens when they go, it's a big bang. Sometimes you can get a heads-up if you notice a slight thump every tire rotation as it passes the roller. That's a bubble forming at the spot where the tire is going to blow. Just change out the tire right away when you get a bubble to avoid ruining a good ride. I buy my training tires about a half dozen at a time from an online source so I always have a few spares ready. In fact, I rarely have a blowout on the road because I change out my tires as soon as they show significant wear.

 

[RapDaddyo]

Actually I got Retul'd once and the way they did it was they had you on an infinitely adjustable fitting bike with a power meter/load device (not unlike a computrainer) attached. Not sure if the fitting bike was made by Retul or not though. The fitting bike was really cool though, as many (but not all) of the adjustments could be done via remote control, while you were actually riding! Every part of the bike could be changed, top tube length, seat tube length, etc. Then there's a camera watching you from the side and the Retul computer system superimposes a stick figure on your body (on the computer screen) and spits out a running calculation of the angles your body is making while pedaling. Very worth while.

Wow! That makes this approach even more interesting. One of the problems of going through the "discovery" process I describe in an earlier post is the time consumed by making changes in the seat position. Being able to do this quickly or even by remote control with servos is even better. I bet one of these guys was into RC models.

 

[RapDaddyo]

Tunnel or field testing really is the only way.
Sometimes positions that "look" more aero, aren't. Or more to the point, aren't as fast.

That's a shame. Wind tunnels are rare and sessions are expensive. frenchyge and I have thought about designing a mobile wind tunnel, but we haven't made much progress. BTW, frenchyge is an engineer and airflow expert. I still think it's possible and can be done not too expensively. Just haven't had time to drive the project along.

 

[lanierb]

That's a shame. Wind tunnels are rare and sessions are expensive. frenchyge and I have thought about designing a mobile wind tunnel, but we haven't made much progress. BTW, frenchyge is an engineer and airflow expert. I still think it's possible and can be done not too expensively. Just haven't had time to drive the project along.

Have you guys considered the so-called "Chung method"? I haven't tried it but it seems like a good way to start. The idea is you do laps of a looped course with a power meter holding the same bike position over the loops. Then, you infer the elevation changes of the course from the power data conditional on presumed values for the CRR and CdA and graph them. Only the correct CRR and CdA will give you the same/correct elevation changes from one loop to the next. This allows you to measure CdA (and CRR). You can then change your position and retest. For more details, see here: http://anonymous.coward.free.fr/wattage/cda/indirect-cda.pdf

Edit: BTW we have seriously hijacked Tyson's thread

 

[Alex Simmons]

That's a shame. Wind tunnels are rare and sessions are expensive. frenchyge and I have thought about designing a mobile wind tunnel, but we haven't made much progress. BTW, frenchyge is an engineer and airflow expert. I still think it's possible and can be done not too expensively. Just haven't had time to drive the project along.

You are not alone in that thought.
wattagetraining.com • View topic - How hard would it be to build a LS wind tunnel?

 

[Alex Simmons]

Have you guys considered the so-called "Chung method"? I haven't tried it but it seems like a good way to start. The idea is you do laps of a looped course with a power meter holding the same bike position over the loops. Then, you infer the elevation changes of the course from the power data conditional on presumed values for the CRR and CdA and graph them. Only the correct CRR and CdA will give you the same/correct elevation changes from one loop to the next. This allows you to measure CdA (and CRR). You can then change your position and retest. For more details, see here: http://anonymous.coward.free.fr/wattage/cda/indirect-cda.pdf

Edit: BTW we have seriously hijacked Tyson's thread

Here's an example of using power meter data to create a Virtual Elevation profile:
Alex's Cycle Blog: Funky things with a Power Meter #77

I've been using the method, quite successfully, to test for variances in aerodynamics on my track bike at an indoor velodrome. I have been able to assess, for instance, the aero difference between different front wheels in order to decide which was the better choice for my pursuits. Last time I did this I assessed the difference between a front disk, a Zipp 808 and an old Campag Shamal.

I also used it to assess helmet choices for a rider I coach (who went on to set a new masters world hour record earlier this year - 48.317km). It readily told us which was the best choice for him. And I could do this from data collected from normal training efforts.

It is remarkably sensitive. But prying apart CdA and Crr is much more difficult and one needs to introduce other variability in the data in order to do that (such as speed variability).

Of course one should also look at using the regression method (which is also linked in the above post) as that enables one to more readily separate the CdA-Crr pair. This has some specific advantages.

Sheets to make it easy to process the data are available via the wattage forum (I posted them there).

However, when doing field testing, there is a pithy power proverb:
"Wind is thine enemy"

By that I mean the results are very sensitive to even minor variations in wind conditions.

 

[RapDaddyo]

You are not alone in that thought.
wattagetraining.com • View topic - How hard would it be to build a LS wind tunnel?

In this thread, Andy C put his finger on the main problem, dealing with the back end airflow. That's why I recruited an airflow expert from the jump (frenchyge).