puppypilgrim

Which is why I converted both my bikes to singlespeeds

Will be doing a 200 km ride from Vancouver (Canada) to Seattle (USA) in June as part of the Ride to Conquer Cancer. I plan to use my SS at 71-72 gear inches for the ride.

SesameCrunch

That is courageous. I hope there's not much climbing!

invisiblehand

That didn't cross my mind. They are very small cogs and would spin a lot.

jur

All this talk about aero bars... that is contrary to my roll-down tests. Sitting bolt upright as much as my arms and fingertips on bars would allow vs sitting slightly bent arms on bars an inch or more below that saddle made squat all difference. Only the most impractical aero tuck made any significant difference.

invisiblehand

It so happens that I have the Bicycle Quarterly article regarding aerodynamics in front of me. Measured in Newtons @ 22 mph ...

aero tuck ... 16.28
drops ... 24.24
hoods ... 26.06
hoods/stem raised 2 cm ... 27.39

They measured frontal area and drag coefficient to determine that frontal area was the big factor.

chucky

It's my understanding that clothing (flapping vs sleek and aerodynamic) can make a big difference and perhaps muddle the aero advantage. Also, it's my understanding that a narrow grip (ie aerobars) has much greater aero advantages than a low grip due to the way the arms taper to the narrower shoulders. So perhaps your extreme upright position was narrower due to unbent elbows?

BTW I just ordered some bullhorns and am going to attach long L shaped bar ends to approximate a triangle/arrow/house shape like this:


we'll see if it helps.

jur

Drag is proportional to speed squared... the difference between 14R's 18mph and the above 22mph would then be:

aero tuck: 10.9N
drops: 16.2N
hoods: 17.4
up 2cm: 18.4

My tests would have been roughly the same as tuck, drops and up 2cm. Alex Whetmore, who did those tests you quoted, agreed with everything I found in my tests.

I suppose it's like trying to reduce bike weight: There isn't one big thing that is going to make a massive difference by itself - you basically have to do everything, and a lot of small things amount to something useful. So going to a more aero position would make you a small amount faster, but don't expect a miracle. In fact if you are not comfortable, you'll end up going slower over an hour.

I still think a clean lubed chain, high quality jockey wheel, a Velocity Aeroheat wheelset and narrow tyres are the first steps. Sawing off an inch off each end of the flat bars will be good, and fitting some small light bar-ends will give you what aero bars would - a lower position, elbows closer to the body.

invisiblehand

Yep. No argument there.

I guess we have to consider what "massive" means. My first reaction is that 5% less wind resistance would be a lot over a long ride. Given this is 14R, we can be fairly confident that he is riding on stelvios or similar!

invisiblehand

Curious ... Where would one get a high quality jockey wheel?

14R 

If you are in the USA, HERE



Edit: For US$150.00, you can get the Ti one, but it is currently out of stock.

KCNC Titanium wheel

Speedo

You are one powerful dude if those differences don't amount to much for you!!!! Using those numbers at 18 MPH the marginal power requirement for drops over tuck is 42.6 watts, hoods over tuck is 52.3 watts, and up 2cm over tuck is 59.5 watts. Any of those is a significant chunk of my power output. A set of $50 aero bars and you can hold that tuck position pretty comfortably.

Back in 2001 or 2002 Bicycling Magazine did a "bang for the buck" assessment of the most cost effective way to buy performance on a bicycle. Aero bars won hands down. The drag force goes with the square of speed, but power required goes with the cube of the speed.

Speedo

jur

Perhaps we don't mean the same thing for "aero" bars? Proper triathlon aero bars have the arm rests on them and there would be a large improvement. But I cannot see ANY advantage in bullhorns as were pictured earlier on in this thread over any other style if those bars are all mounted the same height and do not have the aero arm rests. Do you mean those bullhorns to have the aero attachments for the arms?

jur

So, power in hoods is 17.4*18*1.6/3.6=139.2W
power in drops is 16.2*18*1.6/3.6=129.6W, a 10W reduction.

Did I mess up my calcs? They don't match yours.

Anyway 10W is indeed a significant value. Tyre drag is of the order of 50W, and tyre improvement can be 5-10W also.

[edit] Ah I see what you calculated. We are on the same page.

chucky

I think we both know that the armrests themselves are for comfort and don't contribute anything to the aero advantage. So if the aero grip is in the same position then doesn't it make more sense to support it with a short extension from the end of the horns than a long extension from the stem area? All else equal the short extension will be lighter and stronger.

Of course the pictured bars don't quite achieve the aero grip, but there are other bar ends to choose such at this one which is 7.5" long and L shaped:

And, yes, I plan to use thick plumbing insulation at the flat/stem area to make it more comfortable (with the horns I'll never grip the flat/stem area anyway).

Other alternatives I'm considering entail:
-Hammering long wood dowels into the ends of these bars to close the triangle:

-Reverse porter-style bars instead of flop and chop bullhorns. With the extra horn extension I'll only need to worry about extending the grip towards the center:

SesameCrunch

The arm rests on true aero bars also serve to bring elbows closer into the body, thus making the profile smaller.

Speedo

Yes, and no. What I find key in aerobars is that they help you remain comfortable while holding an aerodynamic position. So the comfort provided by the armrests is critical in the overall function of the aerobars. Using regular drop bars I have to move up and down between the drops and hoods to stay comfortable. Using aerobars I can stay in the aero position for an hour at a time.

(edit)This is what I mean by aerobars. I would agree with SesameCrunch that the quality of the aero position you get with them is important. It is probably the closest to the "tuck" position in the drag results.(/edit)

Speedo

fietsbob

Rather than Chuckie's in #56 kludge ,, the figure 8 bend of trekking bars ,
a Euro favorite,
does that without, uncomfortably, having that clamp for the bar ends
in a good hand grip site.
Kalloy is offering one in the US for a budget $25 .. 22.2/7/8" where all the controls go.. 1" center clamp.

top of the page .. https://sheldonbrown.com/harris/handlebars/index.html

feijai

Seriously, we're talking about aerobars on a bike with as low a trail as a Brompton? I don't think I could possibly ride a bike like that without crashing almost immediately. Low trail steering instability plus aerobar steering instability seems like a recipe for disaster.

14R 

It can be done.



But the selection for the handlebar already took place. Time Trial it is.

Bacciagalupe

That's nice, but that kind of "feedback" doesn't happen on a bicycle. A bicycle is not an amplifier, it doesn't add an old signal to a new one. In fact, your use of "feedback" is, as far as I can tell, rather non-standard.

So, let's review a few facts.

• Power meters sample at a higher rate than cyclometers.
• Power meters are highly accurate.
• Power meters are used by professional racers, who need that high degree of accuracy. This includes sprinters, who can win or lose a race by fractions of a second.
• These kinds of measuring capabilities are one of the major raisons d'etre of power meters.

As to "sample rates," people colloquially use that term to mean the amount of time the display unit will average out. If the sample period is too short, the display can look too jumpy and won't provide useful information.

I.e. by using a 3s sample time, you aren't using a yardstick to measure a flea (as you suggest). In fact, if your sample time is too short, then it'd be like using a magnifying glass to look at a house.

I really see no reason whatsoever for your skepticism towards power meters. They are hands down the most accurate, objective, efficient tool to evaluate a cyclists' efforts. And with a properly designed test, there should be no doubt that they'll produce a good idea of the effect of adding 10 pounds to a bike.


Uh huh.... Such dummies that they include rider position, tire type, temperature, height above sea level and elevation grade in the formulas?

Lots of people who own power meters are aware of the calculators. If they were off by an order of magnitude, someone would improve the formulas.


No, I'm not. I'm looking at the OP's expected uses, and making recommendations on that basis.

14R is commuting and complaining about speed. He's in Florida, so it's almost certainly flat as a board. In this context reducing weight is not going to improve either his speed or travel time or ride feel significantly. (If it did, putting a single water bottle on a bike would drastically change the ride feel.) The only real benefit is carrying.

A 17 pound bike might feel faster, but a big chunk of that will be geometry rather than actual weight. I might add that this is one reason why small-wheeled bikes feel "more fun" than a 700c bike of identical weight -- smaller wheel = faster turning circle = more responsive = "feels faster." That doesn't mean it is faster -- or that the weight he could shed from a Brommie will make an actual or perceptual difference.


You don't need to see the "exaggerated" data. You don't want to see the "exaggerated" data. If the measurements are too jumpy, you won't be capable of holding a reasonably consistent wattage.

For example, if you're doing a 10 mile climb on an average 3% grade, and the 17 pound bike is consistently 10 minutes faster than the 27 pound bike, on multiple tests, and with as consistent as possible a wattage reading, then what's the problem? 10 minutes is well outside any reasonable margin of error. Nor do you need a 20 millisecond sampling interval to truly squeeze every last bit of accuracy out of your measurements.

Oh, and yes, you can absolutely tell the difference between a "lazy" rider and a pro, even when you average out over several hours. For example, here's Bradley Wiggins' profile from the Giro D'Italia, Stage 3, 2009:

https://connect.garmin.com/activity/5284649

The guy averaged 255 watts over 3 hours. Good luck finding a "lazy cyclist," let alone any amateur, who can accomplish that.

fietsbob

My Brompton handles better with weight in the front bag mounted on the frame clip, than without it.

At 200# I have low performance expectations.. its Transportation..

chucky

I haven't noticed any positioning advantage from the rests on the aero bars I've seen: the forearms go in exactly the same place they would if resting on the stem area of the bar itself. As a comfortable place to rest the forearms any good padding should perform well enough. Maybe not as comfortable after an hour, but neither are small diameter wheels...so the compromise seems perfectly appropriate for a folder.

I might buy the argument that the cupped rests make it easier to steer, but I never claimed there wouldn't be any compromise, just that anything which allows one to achieve the same position with the same contact points should provide the same aerodynamic advantage.

Now THAT really would be a kludge. Not only would trekking bars be an extremely unaerodynamic ~4" wider for both the side grip (the "horns") and the aero grip positions, but the controls would also be in the worst possible spot for aggressive riding. Moreover it would require an extremely long stem since the butterfly bars need to be mounted with the open section backwards (or else the side/horn section flares out resulting in uncomfortable and unaerodynamic arm splaying).

In comparison what I've proposed should match actual aerobar positioning in every possible way with only a moderate compromise in comfort (but at much lower cost and weight).

You obviously have no idea what I'm talking about. Go get a good book on control systems and once you've applied what you've learned to the cycling formulas, then we can resume this conversation.

Why control? Because control is how one unlocks potential; it is the difference between what a Ferrari can do in 60 seconds vs a gallon of pure gasoline.

Speedo

Huh? On the one hand you're a hard dude who dismisses the comfort in the armrests, and on the other you can't ride your small wheel bike for more than an hour because it's uncomfortable.

Speedo

Bacciagalupe

Funny though, I know what I'm talking about.

Since you clarified that you're talking about control systems, I expect what you mean is:

- The power meter reports wattage output to the cyclist.
- The cyclist adjusts their efforts to maintain a consistent wattage.
- The new effort level gets reported back to the cyclist.
- Thus, the information fed back to the control mechanism (the cyclist).

Your argument seems to be that any averaging interval on a power meter will obscure vital data, which will result in improper feedback sent to the cyclist.

This is incorrect.

I suspect one reason why you believe this is because you do not understand how pedal strokes actually work.

Cyclists don't apply 100% consistent power at every instant of a pedal rotation. In fact, a cyclist is more like a two-stroke engine. You apply an increasing amount of power on each downstroke and none on the upstroke, so it's more like a pulse than a steady stream of power. You don't actually apply power on the upstroke, even if you're clipped in; all you do is relieve the downstroke from the extra effort of lifting your other leg.

As such, if you were looking at instantaneous data, it won't be a consistent number; you'll constantly see huge spikes, and as such you won't be able to properly evaluate your efforts.

Consider the second graph below ("Vector Power Left / Right"), from Metrigear. Their power meters are in the pedal itself, rather than in the BB or rear hub. The power output of the left leg is in red, and the power output of the right leg is in green.



If you were looking at instantaneous data, your output would go from near-zero to 800 twice a second. Seeing that much data would be utterly useless in terms of evaluating your efforts, and would NOT work "better" than, say, a 2- or 3-second average.

Because a cyclist is more like a two-stroke engine than a water wheel, a sample interval that is too fast will be counter-productive for providing feedback to the cyclist, because the rider won't be able to make sense of it. You need a longer averaging interval to make the data intelligible.


So, what about longer time periods?

Keep in mind the test I'm proposing: We want to find the effects of changing one variable (weight) on the total time it will take to do, say, a 10-mile climb on a 3% grade. The purpose of the power meter is to keep the power output as consistent as possible, to eliminate a critical variable as best as possible.

The shorter the length of the test period, the less likely you are to have a measurable difference. A 10% difference on a 30 second run is 3 seconds. That's going to be extremely difficult to measure without a highly sophisticated testing system.

In comparison, a 10% difference over a 60 minute run will be 6 minutes. You could easily pick up a difference like that with a wristwatch. If you really wanted to go nuts, you could compare the charts to pick up any discrepancies due to fluctuations in the rider's power output and possibly correct for them.

Thus, in this case a longer measurement provides better real-world data.


Finally: You don't seem to understand that providing feedback to the rider is a critical function of a power meter. For example, pros routinely use them to avoid going anaerobic -- and they're using 2s or 3s sample times. If it wasn't providing reasonably accurate data to the rider, it would be worse than useless.


So, in sum:
• Power meters are designed to provide accurate feedback control data to the rider.
• You need to average power data over 2-3 seconds to get intelligible results.
• You don't lose any critical accuracy with a 2-3s average sampling rate.
• For our purposes, a longer test/sample time will produce better results.

As a result, if you want a real-world evaluation of the effects of weight on rider performance, and you don't have access to a multi-million dollar training facility, your best option is to do repeated runs on a specified route using a power meter to get the power output as consistent as possible, and have the run be long enough to make the effects easier to measure.

So, NOW do you see why I proposed using a power meter?

puppypilgrim

Bacci,

That's a FANTASTIC explanation! Thanks. I learned a lot from your post.