Vertically Inane and Laterally Fatuous
You might’ve noticed that we don’t do a lot of bike reviews on this site. There’s a couple of reasons for this.
One, bike makers are hardly clamoring for our ‘expertise’. Two, and more importantly, road bike reviews SUCK. They’re all incredibly subjective, and despite having been mercilessly mocked by bikesnob, continue to revolve around the dual linchpins ‘vertically compliant’ and ‘laterally stiff’. We’ve only done one bike review (scroll down) on this site (well, two), and it was a direct comparison between three bikes where we declared a loser (in so many words, words like ‘carbon quicksand’). Since most reviewers depend on industry advertising, you’re not going to see a lot of bikes declared a ‘loser’. Therefore, almost all reviews will tell you that the bike in question accelerates like a scalded cat, climbs like a spider monkey, smoothes bumps like a Cadillac, and is stiffer than Viagra in a sprint. You should also add it to your quiver immediately.
Keeping this in mind, VelocityNation would like to announce the birth of DrunkWerx, our super secret testing facility with a super stupid name where we will attempt to put hard numbers to that elusive quality called ‘feel’. We’ve created tests for vertical compliance and lateral stiffness, and we’ll try to amass a database of bikes for comparison. This week we’ll establish a baseline using my old Viner carbon bike, and next week we’ll review the Litespeed Archon.
Vertical Compliance
I taped a 4mm wire to the front and middle drums on my rollers to simulate a bump in the road. Reflectors are attached to critical points on the bike: both axles, the top of the headtube, the seat collar, and the top of the seatpost.
The bike is first photographed statically to establish the size of the reflectors, then shot in motion as I rode the rollers. A one second exposure captures several cycles over the bumps.
The size of the blur is then measured in Photoshop, and the dimension of the reflector is subtracted to yield actual travel. The travel distance is then compared to the reflector size to correct for size differences due to perspective. The ten cleanest shots (where I stayed the straightest on the rollers) are chosen and the numbers averaged. Then the travel at the headtube is divided by the travel at the front axle, and the seat collar by the rear axle. That percentage is subtracted from 100 to give the % of vibration dispersed by the front and back end of the bike.
The Viner eliminated 29% of the vibration in front and 38% in back.
Lateral Stiffness
Our lateral test is far less accurate than the vertical test, but much more fun. A laser pointer is attached to a small video camera, which is in turn attached to the top tube near the head tube. The laser pointer is aimed at a target on the seat collar. The target has calibration marks to show how much the laser dot moves from side to side. I then do some sprints and try my damnedest to flex the frame. Here’s a short video. The picture is sideways because the helmet cam has to be mounted on its side. The red dot is a lot easier to make out in the original uncompressed video.
The Viner flexed 4-6 millimeters for the most part, with a max of 7.3mm. For the record, I’m 165 pounds and the max sprint recorded on this day was 1045 watts.
Seriously. Neat idea though! Keep up the DrunkWerx1
This is awesome.
nice, this is fine work here, people. it’s been a while since you donned the lab coat and went mad scientist on us, andy! for another measurement, you could use a method similar to the lateral flex test, but attach the pointer along the seat tube, close to the BB, and maybe use the trainer in a big gear — when i ride the trainer, i’m always a little shocked when i look down and see the bottom bracket swaying back and forth. it’s especially pronounced if you push a huge gear. on the trainer you could regulate the torque/watts/cadence more easily, too.
They use mirrors a lot for this kind of analysis. For instance the guy’s suggestion for shooting the laser up the seat tube, you could fix a mirror on the bottom of the top tube to bounce the laser onto a sheet of large sheet of graph paper in front of you and off to the side… might be tricky with spinning legs & knees. Then record how the laser moves around the graph paper to measure the effects once you are pedaling.
http://www.iop.org/EJ/abstract/0022-3735/14/11/012
Yamaguchi who wrote that article was probably the same guy who made steel frames in the 80s (the article’s from 1981).
dont push 450 on the trainer for extended periods of time, your BB wont flex as much…;)
Having seen the endless flame wars on the cycling newsgroups over anything related to the tech aspects of cycling I have to commend you for your bravery in looking at this area. I’m not in the least a techy with no engineering background whatsoever but from my unlearned view you don’t seem to take into consideration the size of the rider or the size specs of the bike. I think your test might be worthwhile for an individual to judge how well a particular bike is matched to his or her body type. But a lighter or heavier rider on a different sized frame, etc. would likely generate different results. Also, the vibration you’ve induced seems to be too regular rather than random. Again, engineering is not my area but harmonics would seem to be more significant in your test than in the real world. Softride was mentioned in a comment in another article and that made me think of another possible misrepresentation. The Softride seat apparently bounces a lot, having no shock absorber to dull the “ringing” of the seat. That might appear to be a problem in a test like yours but in terms of the jarring of the “taints” it’s probably better – less stressful. That is, you seem to be measuring the travel of a vibration ‘stroke’ (can’t think of a better way to describe it), but not the ‘hurt’ factor. I guess it’s the “G” force transmitted that isn’t considered.
From my own personal experience and aching back I remember the switch over from my prior gas pipe tubed 27 x 1 1/4 to large tubing aluminum with carbon fork bike. My first 50 mile ride (my standard, rarely exceeded) left my back in severe pain and my wrists feeling broken. It got to the point where I realized that I was continually on guard for any slight bump or rut in the road, gritting my teeth in anticipation of the pain when one could not be avoided. Eventually I went from 25c tires to 35c to reproduce the gentler feel of the old bike. And that was with the shock absorber seat post the newer bike had. I had transferred the sprung Brooks saddle. I think the less techy foam bar pads of the old bike did a much better job of easing vibration transmission to the wrists than the gel wrap that’s on my newer bike. Personally I think gel in any bike use should be spelled b-u-l-l-s-h-i-t. It doesn’t work in the bar wrap and it certainly doesn’t work in taint pads where it seems to counter any benefit of the Brooks saddle. Oh, my bike has those see through things in the fork that are gel like and supposedly dampen vibration. “Jerk” pads or something.
Anyway, that’s my seat of the pants perspective on vertical compliance, sans reflectors.
Slam, good points. I didn’t mention it to avoid muddying the waters, but there was a touch more movement at the top of the seatpost than at the seat collar. This is with a 27.2mm carbon seatpost. With a 31.8 carbon post on the Litespeed, there was about the same movement at the seat collar and the top of the seatpost. This seems to indicate that the skinnier post is flexing more, which might be more comfortable.
As for rider size/weight, I’ll be doing all the testing, so that’s one variable that won’t change. But a harsh frame for me might be fine for a bigger guy. All I can do is try to provide comparisons between frames. And I’ll try to test only 56-57 size frames.
Nice work Andy. The homestyle science and testing is great. When are you introducing your own power meter?
Pretty sweet tests – the diy science approach is great. You may consider looking at the impact of not being exactly straight on the rollers. That U shaped pixel trail looks too uniform and may be influenced by your sideways motion. Sideways motion will cause some up/down movement because the effective distance between the drums changes. You’d be interested in the vibrations above and below the U shape predicted by the yaw impact.
The blurs took on all sorts of different shapes, so I wouldn’t put too much stock in the U shape. I think that you can’t lean a bike very much on the rollers and remain upright. The reflector at the axle is about 34mm from the bottom, and the reflector at the seat collar is about 77mm. If the bike leaned 1 degree, then the lower measurement would be off by .005mm, and the upper measurement .012mm. If the bike leaned 2 degrees, then those numbers would be .02mm and .047mm. For 2 degrees, that’s roughly a .5% error at the bottom and a 2% error at the top. So I don’t think the sideways motion affects the results by that much.
I’m an idiot!! That’s 340mm and 770mm, so multiply everything by 10. If you assume the lower limits of the travel are caused by a 2 degree lean, then the actual damping number for the rear of the Viner would be 48% instead of 38%. This obviously makes the numbers pretty unreliable. I can only hope that I’ll ride in a similar way on all the other bikes and the same error occurs throughout, so at least the numbers will be useful as a comparison.
I just read that Drunk Werx will be speaking and presenting their findings at Interbike in Las Vegas. Good luck and be on the lookout for Greg Lemond crashing the event.
I just measured some angles in the shots, and the variation I can see doesn’t exceed 1 degree. If there’s a .7 degree variation, the rear damping number would be 40% instead of 38%.
the creaky noises and your thighs got me a litle randy. did i miss something?
Glad to be of service. Might get some glasses to complete the sexy librarian effect.
I would like to make a few recommendations, which you have already thought of, for the vertical compliance test. Make sure you use the same wheels and tires for all tests. Make sure you pump the the tires the to the same pressure for each test. Using the same tires is probably the most important part since compared to everything else they flex much more. You should also try to use the same seatpost and seat since they too flex a bit. Lastly, you might also try to use the same bars and stem.
I really like that you put a lot of thought into your experiments and try to do measurements as accurately and reproducible as you possibly can using home made jigs. Cool stuff.
ride yer bike!
and you are quantifaction of the flatulation because you might reproduce your pontication that no 2 bikes ever feel the same? First you must age your components separately in vacuum douchebags, then after 3-5 years, whether you are Belgian or Basque, you can then assemble parts into “identical” machines…
But I lost my train of thought?
oh yeah, RIDE YER BIKE, HARD!
😉
(there, I feel better, and will be at the top of Perkins performing Cyclo-CORE)