osymetric
  • Anonymous

    A 10% increase in power for only a 1% increase in speed? That seems like very little gain for such an increase in measured power.

    Also, he claims a 0.9km/h increase in speed, implying 90km/h riding speed?? Something’s fishy in Jean’s maths…

    • I’ve double checked the recorded conversation I had with Jean-Louis and that’s what he said. I’ll email him to confirm.

      • Nick

        It sounds fairly realistic to me.

        On a flat road, 600W gives you 47.43 km/h. A 10% gain in power gives you 49.06 km/h (which is ~1.5 km/h, or roughly 3% more. Calculations done via http://bikecalculator.com/).

        I suspect Jean may have actual test data that shows a 10% power increase, a 1% speed increase and a 0.9km/h speed increase, all from different test.

      • Nick

        It sounds fairly realistic to me.

        On a flat road, 600W gives you 47.43 km/h. A 10% gain in power gives you 49.06 km/h (which is ~1.5 km/h, or roughly 3% more. Calculations done via http://bikecalculator.com/).

        I suspect Jean may have actual test data that shows a 10% power increase, a 1% speed increase and a 0.9km/h speed increase, all from different test.

      • Anonymous

        OK, I stand corrected. Ran some numbers through analyticcycling.com;
        rider + bike = 90kg, eff. frontal area 0.6, 0% slope, 90rpm cadence…
        36km/h = 219.2W
        241.1W = 37.3km/h, so extra 10% gets you 1.3km/h. At pro rather than fat hack speeds the gain is probably a lot lower due to wind resistance.

      • Coach

        There is a known issue (actually, known by few, but verified) to do with the sampling rate of SRMs over the course of the pedal stroke and the way torque is averaged that mean that non-circular rings lead to high readings. This would go some way to explaining the discrepancy in power versus speed.

        • Is this why some sports scientists say that the shape of the chainrings messes with the SRM readings into make the measurements appear higher than they really are. Would a powertap make a difference in measuring?

          • Peter Karlsson

            There is one power meter immune to different ring shapes; the polar chain based power meter. See google wattage group,my precious something. SRMs do inflate.

        • jules

          this doesn’t make sense to me. the torque will also vary over a given crank revolution with conventional round chainrings. the SRM system just samples stress values (measured with strain gauges) at different points across the crank arc and averages them to derive torque. the Osymetric rings will change the shape of the stress/torque curve, but my understanding of the SRM system is that it would easily account for that.

          http://www.srm.de/index.php/gb/technology/function

    • Robert Merkel

      The online calculator at Analytic Cycling suggests that you improve your power by 10% you get about a 3.5% improvement in speed on the flat, all other things being equal. So, for instance, going from 300 to 330 watts should get you from about 43.2 to about 44.7 km/h.

    • Note that the 10% more watts is at VO2max based on a study involving 19 cyclists. At lower intensity the advantage is less. I produce 4-5% more watts at LT with Osymetric compared to round rings. However, it is individual. Some might have smaller or bigger advantage. Hope this clarify your question. Best regards Bo Kamstrup, distributor of Osymetric in Scandinavia

    • It is at VO2max intensity that power is increased 10% using Osymetric according to the study. At lower intensities the advantage is less.

  • learn how to pedal and you dont need this extra stuff!

    • mouse

      Brilliant contribution.

    • Cynic

      But it wouldn’t lead to any debate that’s nearly as interesting as this one :)

    • Cynic

      But it wouldn’t lead to any debate that’s nearly as interesting as this one :)

    • Kris

      Yeah the tour can be won on a kmart bike.

  • Nico

    Following success of Sky using these chainrings I also recently purchased a set but yet to install which sounds like a challenge in itself. Hopefully worth the cost and effort but also concerned if 10% increase in power yields 1% in speed?

  • Nico

    Following success of Sky using these chainrings I also recently purchased a set but yet to install which sounds like a challenge in itself. Hopefully worth the cost and effort but also concerned if 10% increase in power yields 1% in speed?

  • jimbo

    It would be interesting to hook this up to an SRM and see the difference in the power curve (or torque curve) over one pedal revolution as compared with a circular chainring.

    • The SRM calculates rotational velocity once per rev, this velocity multiplied by torque gives the power reading. The assumption is made that the rotational velocity is constant throughout the revolution as it does not have the ability to measure instantaneous rotational velocity. Non circular chainrings obviously change this velocity relationship and hence the power reading. An SRM reading torque coupled with a instantaneous velocity sensor on the bottom bracket is required to measure the power accurately. The torque value alone is not really useful information as it is power that propels the bike.

      • What are your thoughts on this Raoul? Do you have any experience with testing athletes on osymetric? Or anything anecdotal?

        • We have done quite a bit measuring instantaneous power with some equipment that we applied for a patent. The torque curve is sinusoidal as to be expected, however the velocity is also non constant and there are large differences depending on the cyclist pedalling technique. If you want accurate data you cannot make assumptions on a major variable!

          Typical powermeters record average power typically at 1 Hz. To get a better understanding of the pedaling cycle 100Hz or more data acquisition is required. It depends on how much data you want to process, only recently has the hardware existed at a small enough size to have onboard.
          I have also looked into shaped chainrings and other methods to reduce the “deadspot” with mixed results. That’s all I can say at this time :)
          Power is the product of torque x angular velocity, however as stated above the torque value alone without the velocity data is not that useful. The highest torque values are produced when stationary, the power is zero because the velocity is zero. Power needs to above zero to propel the bike.

      • jules

        disagree. what you describe is problems measuring instantaneous power – but you can use the average speed (cadence) to measure average power, say over a single crank revolution. that’s all you would ever need.

      • jimbo

        sure, but power is the product of torque and angular velocity, so torque is highly relevant. Assuming the angular velocity varies insignificantly over one pedal stroke (regardless of chainring type) then any differences in power over the pedal stroke are related to the variation in torque generated. It is this that is of interest.

      • Henry

        A simple solution to this (which no one mentions) is to simply do the testing with a PowerTap, that uses torque*wheel speed which would be unaffected by chainring shape

      • Ashraf

        Torque is a product of force (from leg) and perpendicular distance (crank arm) which none of these variables are affected by chainring shape (gear teeth). However chainring angular velocity will vary relative to no. of gear teeth (radius) which in this case changes with non circular chainrings, hence velocity becomes the comparative variable between chainrings.

  • jules

    i have no specific knowledge of these and can’t judge their effectiveness. but i have dealt a bit with claims by suppliers of motor vehicle fuel saving devices. what i learned from that is that humans are very poor at subjectively assessing marginal changes or improvements in areas of performance subject to multiple confounding factors – otherwise known as the placebo effect. the funny thing about the placebo effect is that people often swear that they can genuinely detect an improvement – and they may be right – it’s just that the improvement is sometimes derived from the expectation of an improvement (in this case, which may psychologically assist the rider in producing more power).

    i’m not suggesting that is necessarily the case with the Osymetric chainrings – i don’t know, but the only way to tell with certainty is scientific testing – which i imagine is difficult with a product that works with complex human biomechanical systems.

    • steel

      Surely the difference here is that unlike the “perpetual motion” machines spruiked by the snake oil salesmen in the automotive aftermarket, this idea at least seems to work from a theoretical mechanical view. Increasing your moment arm at the point of greatest leverage while reducing it a top dead centre seems technically sound to me.

      Anyway, don’t necessarily disagree with anything you’ve said, more just the degree of skepticism with which you approach this.

      • jules

        i wasn’t commenting on the concept, just the method of measuring its effectiveness.

        i am skeptical of the concept though – the moment decreases at top/bottom dead centre. at the same time, the chain length is being increased – as chains are not flexible in that direction, this means that cadence will slow to accommodate it. varying cadence from the optimum will reduce power (for that phase of the pedal stroke). the combination of reduced moment arm and having to slow your pedalling while the chain ‘feeds’ through will combine to reduce power at top/bottom dead centre, at which power is already compromised biomechanically (you’re pushing forwards).

        this all has to be compensated by increased power on the downstroke (which it would be, for precisely the opposite reasons as it’s decreased at op/bottom dead centre). maybe it is – it didn’t seem to slow Sky down.

  • Chadwick

    Ive used the Rotor Qrings and i honestly felt no difference in power/speed but it all felt natural. Though the Rotors are on the training bike and have circular on my race bike yep i go against the system.
    Though i definitely know the feeling of setting up the FD and shifting at the ring point to not derail same issues with the Rotors.

  • I would be sceptical about claims of increased power with Osymetric rings, or other non-standard rings. Aside from the basic observation that if that were the case I’m certain the entire peleton would be using them, there’s the simple mathematical proof that you can’t measure crank based power on a chainring that’s not round – so unless you’re running a powertap then the figures will be wonky.

  • I rode these chainrings for a week or two on a bike I was thinking of buying. It definitely felt faster, but I found the shifting was a deadset pain. Was riding with Di2 and consistently struggled to shift the gears neatly from big ring to small and back.

  • wilso

    I cant see this working for sprinters as they are only in their position for ~300m of a 70-200km race.
    what about for track sprinters though. could the angle of the dead spot be modified?

    • It wouldn’t work on the track unless you had a chain tensioner.

      • vandebergen

        I run a Rotor Q-Ring on my singlespeed/fixed gear MTB with zero issues.

  • Sold! Great article. A chain catcher may also be a good suggestion.

    • A chain catcher comes with the chainrings, but it’s not pretty. A K-Edge catcher looks better in my opinion.

      Bobby said that still uses the chainrings to this day. He used them for both road and TT back in the day.

      • Peter Karlsson

        Set the k-edge chain catcher up so it just rubs when on large back, small front, wrap the edge in electrical tape to make the slight touch of chain less of a drag (audible). This way you’ll get clean downshifts to small front, and no dropped chain (in that direction).

      • Hazy78

        Do you know if there are plans to improve shifting Wade, anything like those used on Q-rings or absoluteblack?
        I’ve wanted to try O-symmetric for a while forever the ones I’ve looked into don’t suit my cranks so is a big step to change everything.
        Great article by the way.

  • Paolo

    Lets hope Contador doesn’t use them in next years Tour…but maybe he won’t need to as they didn’t really help Froome in the Vuelta. What i don’t understand, how you can push out more watts when your legs are still the same?

    • steel

      Mechanical efficiency

  • cynic

    off topic….. but 490W was more or less what Lance/Ullrich put out to win the tour, and at wiggos weight that 450W is more or less the same P/W ratio as them anyway. who said cycling was getting cleaner, cant wait to see that average speed drop back down to 36/7km/h for the entire race……. Viva le Blaireau!!

    • Nick

      It’s good to be cynical, but in this case I think it is misplaced.

      “The difference between the current era and previous eras is startling. In the last four years, none of the Tour’s decisive HC climbs have been done at greater than 6 W/kg. Even theContador-Schleck showdown on the Tormalet, with the Tour title at stake, was ridden at 5.9 W/kg. ”

      http://www.sportsscientists.com/2012/07/tour-in-mountains-analysis-discussion.html

    • jules

      while i’m commenting on everything, i suspect the lower average speeds of previous era Tours was a lot to do with the absence of teams willing to drive the pace all day to force a sprint finish.

    • Euan

      Armstrong and Ullrich were pushing these numbers at FTP up Ventoux etc. Wiggins wasn’t pushing more than 6.1W/kg at FTP which is substantially less than Armstrongs 6.7+ numbers.

  • I’m also curious about what effect these rings would have on the wear and tear of chains – anecdotally I heard that because the chain grabs and stretches, it reduces the life of a chain. Perhaps not a big problem for a pro on a team where they get all their gear for free.

    Wade, have you ridden them long enough to notice abnormal wear and tear?

    • I’ve only ridden on them for a week and can’t see any wear on the chain. Chains are only $40 these days and if they’re kept clean they last quite a while.

  • toby@ride

    For those interested in a comparison between Rotor rings and O-Symetric, here is a little review we did back in 2010 with Shimano Dura-Ace Di2 as the groupset.

    http://www.zinio.com/pages/RIDECyclingReview/No.49/416212681/pg-166

    • Thanks Toby. I completely missed that article.

  • Hi Wade, thanks for this post. These odd looking chainrings were a standout feature, visually at least, of this year’s tour, so the follow up article is of immediate interest. I have had some experience with “asymetrical” chainrings. Soon after experiencing flex in my sram red chainring (early version), I have been running an old Biopace chainring found in the shed (aka dead bike archive). Until I read your post, I was unaware that Biopace and Osymetric are oriented in the opposite direction. S’pose its time for a new new chainring. But first, I might experiment by reorienting the Biopace around 1/5th and see if it makes any difference. See you on 1:20. http://app.strava.com/athletes/111528

  • slapper

    me smells an advertorial..

    • Do you honestly think I’d risk the trust and credibility I’ve earned on a $200 set of chain rings which I’ll never have a hope in getting and advertising dollar from?
      I’ve always disclosed any potential conflict of interests. There is none here.

      • Peter Karlsson

        CTips, nice article. I share your enthusiasm, and changed to osym on four of my bikes. Actually, 3.5 bikes; one has a round 44 ring and an osym 54; when shifting between them during a ride it’s all too clear I’ll never use round rings again. Osym feels continuous, round, smooth and strong, round rings feel jerky, unkind and square. Well, you know by now. Shifting sucks, but stand and climb on these rings and all is forgotten.

    • AaronG

      me too………..I better get the Gruen boys to analyse this type of marketing strategy. Interesting in the regular use of the capitalised brand name “Osymetric”. We get so used to talking about brand names like “Glad Wrap” instead of “plastic wrap” and, in this case, “Osymetric” (capital O for the brand) instead of “non-circular chain rings”. The accidental rendezvous with Jean-Louis was quaint.
      Anyway, gotta pull on the Nikes and go for a run……………I’ll Google this topic and then I’ll Facebook you later

    • mattb

      have you ever read this blog before? me smells someone who just likes a product

    • jules

      good point. i think all product reviews should be done without mentioning the product name.

  • Camsand

    Re the installation, what was the issues. Seems simple on the video, so I’m assuming it was around the fd setup? If so, the heights, or end point adjustments? Or both? Is it a trim issue, in which case group sets ith trim adjustment may be easier to set?
    Thanks for the article

  • Thanks for the article. Is Osymetric a sponsor for SKY ?

    • No, they aren’t. Shimano is SKY’s sponsor and you’ll notice that all decals and branding for osymetric is rubbed out.

      • Brilliant.

        A friend of mine is ordering one already.

  • Thanks for the article. Is Osymetric a sponsor for SKY ?

  • Peter Siestrzewitowski

    First of all, thanks for the great read! I am an avid fan and user of the Rotor rings. For me personally its all about the feeling and the end of aching knees with the Rotor rings, not power output. I had a pro fit done and the Rotor rings were the piece to the puzzle the took away the knee pain. I also did consider the OSymetric rings but the spotty shifting held me back. I really hope that the next generation will fix this. Combined with the YAW Red FD I get perfect shifts both ways every time and have yet to drop the chain. These rings, both Rotor and OSymetric seem to be most beneficial during climbing, making spinning up the hills much more efficient. Just my .2c

  • MaLóL

    are these reings available for compact cranks? I guess that makes little sense for racing, as pro riders use no compact, but I´m thinking about trying them and would like to know. Rotor are available in compact diameter though…

    • Yes, they do come in compact, but because of the shaping, the smallest inner ring you can get is a 38. Some people blamed this for Wiggo and Froome’s sluggishness on the super steep pitches in last year’s Vuelta. Obviously did not bother Froome enough for him to change though, as he still used them this year, although with some big cogs (a 32, I think) out back. I use a 38×52 combo. I am effectively pushing a 36 over the top, and then a 40 in the power stroke.

  • C Grade Cyclist

    Thanks for the great review CT – I’ve always wondered about those funny looking chain rings!!
    Re: your comments about them being ‘just a thin bit of alloy’ – I know early SRAM chainrings copped a hammering because of how much they flexed, and they had to be ‘beefed up’ (and became the ‘sprinters chainrings’). Do you think these Osymmetrics will suffer in the same way?
    Sounds a lot to me like they would benefit by being taken over by a larger company that could integrate some ramp/pins to improve shifting and maybe stiffen them up a bit… What do you think?

    • Yeah, the first thing I noticed when I took the rings out of the package is that I could flex them by hand. Not a huge amount, but enough to notice. It’s not something I notice when riding though

  • Aaron DC

    “According to Jean-Louis, he did some testing with Bradley Wiggins during
    this year. With circular chainrings he tested 450watts at a 20mins
    average. With Osymetric chainrings Wiggins generated 490watts average
    (20mins ave).”

    What I find most interesting is that since the 12th of July, these rings have improved Bradley Wiggins’ power an additional 10W !!

    On July 12th, this very same Jean-Louis told 20minutes.fr that “Quand un gars produit 450W, ce qui est déjà énorme, avec ça il va produire 480W.” ie “When someone normally produces 450W – which is already enormous – with this they produce 480W.”

    But meh, what’s 10W between friends right?

    If you’re interested in reading more from Jean-Louis’ interview with 20minutes.fr, the article is here: http://www.20minutes.fr/sport/cyclisme/970437-tour-france-retrouve-inventeur-arme-secrete-sky

    “I have not independently verified this, but it’s a point
    that Jean-Louis is eager to talk about.”

    Eager? Why am I not surprised! Free power!! Every cyclist’s dream. Also available via EPO and blood transfusions.

    If we take his claim at face value, and say the chain rings provide the difference, making the rider more efficient, as opposed to the other explanation that round rings are absorbing 10% of a rider’s power, we get the following:

    450W for 20 minutes consumes ~2348kj @ 23% efficiency
    490W for 20 minutes, only consuming ~2348kj requires an improvement to 25% efficiency

    I ain’t buying what he’s selling.

    • Aaron, thank you for your excellent comment and analysis that adds to the conversation, but I’ve edited out your unsubstantiated doping allegations. This won’t be tolerated in this forum.

      • Aaron DC

        Apologies for giving the wrong impression. In no way was it mean as a doping allegation. I AM questioning the veracity of the claim Jean-Toulis makes, that it increases power 10%.

        Do you know when Brad started using them? I get the impression it was when he joined Sky.

        Here’s an interview discussing pre-2009 Tour de France testing Brad was doing when at Garmin:

        “The
        tests he’d done suggested he could. “In a ten-mile time trial I
        averaged 482 watts for 18 minutes, and if I did a 30-minute test on a
        climb I’d be averaging 475 watts.”

        http://www.cyclingweekly.co.uk/news/latest/436524/bradley-wiggins-the-transformation.html

        • No worries Aaron. I just need to make that line very clear.

          From what I understand Bobby Julich put Wiggo onto these chainrings in 2009 before he got 4th in the Tour with Garmin.

  • Notso Swift

    Hmmm comments are gone?
    Still bugs Wade? I had thought the take 2 of the new system was going OK

  • Notso Swift

    Hmmm comments are gone?
    Still bugs Wade? I had thought the take 2 of the new system was going OK

  • Rasmussen

    For bold claims, there is a significant lack of evidence presented by O-Symmetric. That is especially notable considering how long the product has been around for. Surely there has been time to provide some reproducible evidence by now?
    If Jean Louis had data relating to his chainrings providing a 10% boost in power, why does he not publish his methods and results in a reputable… or even non-reputable journal?
    Until then, his claims are as reliable as those made by Patrick Holford.

    CT, I doubt your comments section has enough space for me to write at length about scientific method and bias (intentional or not). But I would love to send you a book to read by Dr Ben Goldacre that addresses bold marketing claims, bias, perception, placebo effect and how the scientific method combats these problems. Although Goldacre refers mainly to complementary and alternative medicine, his tome is equally as relevant to claims regarding these chainrings.

    Furthermore, while I have not conducted a literature review of scientific studies on non-round chainrings, the literature I have read would best be described as mixed. While power increases have been reported, they have mostly be reported around the 3% mark. Notably though, studies dont show any change in physiological function and oxygen metabolism is usually the limiting factor in cycling, not one’s ability to push a big gear through its dead spot.

  • I have Osymetric rings on my racing bike, and Rotor Q rings on the bike I train on and my MTB. I put the Osymetrics on because the Rotors would not fit on a compact Quarq powermeter without some serious hacking. The big knock on the Osymetrics is the poor shifting. Being able to slam it into the big ring at a critical moment is important. I hope that Osymetric improves their design with some ramps and pins, and perhaps a stiffer ring.

    Another minor complaint is that the smallest available size is a 38, instead of the 36 I prefer to ride. And, they are noisy….dropping 4 chain rollers onto the chainring all at once as it hits the flat part of the ring makes a noise that sounds like your drivetrain needs some work…..and it happens twice a pedal stroke.

    They do feel great when you are on the limit and would normally be pedaling squares, and they also feel great out of the saddle, when it is hard get power down over the dead spot. Quarq calibrated them for me, and they said they were able to get reliable power readings.

    Overall, though, I prefer the Rotors. They feel smoother, because you don’t have to accelerate your foot over the top in such an exaggerated manner, and they shift great (I use the stiffer aero big ring). As to which one is technically faster? No idea, but they both feel better than round rings under big power.

    • Brill Chris….I came back to ask just that question…. I will stick with the Rotor Q’s I have – which incidentally appear to have cured my knee pain within a week (surviving both Haute Route Alps and Pyrenees) whereas before on rounds I had pain after 20 minutes of every ride. No science basis for this, but that was the change which yielded knee pain free 1500km of riding through the two mountain ranges…Maybe subconscious change making me pedal sweeter, maybe real. But I will take it.

      • Good to hear that your knee pain issues were solved. That is one of the claims made by both Rotor and Osymetric, as there is less torque required over the top and across the bottom of the pedal stroke, which eases the strain on your patellar tendons and hamstring tendons.

      • Good to hear that your knee pain issues were solved. That is one of the claims made by both Rotor and Osymetric, as there is less torque required over the top and across the bottom of the pedal stroke, which eases the strain on your patellar tendons and hamstring tendons.

  • Phips

    I ran Q-rings for almost a year before giving Osymetrics a go a couple of months back. I did some crude physiological tests of my own of Qs versus rounds earlier this year (http://trackstanding.com/rotor-q-rings-versus-round-rings.html) and found they worked much better for me – heart rate 5-10 beats per minute less for a given wattage. So I’m sticking with them. I’ve been meaning to get around to testing Os in the same way (although my heart rate and power readings are much the same as Qs) – but purely subjectively I prefer the feel. Sure, shifting is a pain (and I’m running Os with Campag EPS) but not if you time it right. The words above from a pro are exactly what I’ve found – I tend to shift down once my foot has come through 6 o’clock and is heading for 8/9, and shift up between 5/6 o’clock – backing off the pressure everso slightly (which you would on mechanical too, anyway) Works faultlessly every time then.

  • The rear derailleur has to constantly extend and retract through the pedal stroke with this setup. Wonder how significant the losses are?

  • Tim

    For the vast – vast – majority of riders out there, spending money on training/losing weight would offer, I think, a better ROI and more definitive result than stuff like this.

    Sure, if you’re a pro, 1% makes a difference, but at A-B-C grade level, dropping weight, or even some kgs off your bike, and doing some good training, and cross training, would provide a more quantifiable improvement than these.

    I’m not saying they don’t work – far from it – I’m just saying, for most people, have some perspective.

    We all love spending bucketloads of $ on tech and mech trying to win local races and shave seconds off Strava KOMs, but really, big gains are possible with training/eating right, sleeping right, stretching, self treatment of your body and more.

  • I was speaking to Christie O’Hara at Eurobike who performed an independent study “Effects of Chainring Type (Circular vs. Rotor Q-Ring) on 1km Time Trial Performance Over Six Weeks in Competitive Cyclists and Triathletes” published in the International Journal of Sports Science and Engineering (who has since joined ROTOR’s competition & scientific staff).

    Very impressive paper, and seems quite conclusive about the benefits of Q-Rings. (Note they are a different shape than the Osymetric chainring, and according the Rotor the effects of the Osymetric shape are not proven in studies.)

    “Evidence from this study indicated that for these well-trained cyclists and triathletes, performance improved after just one week employing the Rotor Q-Rings. The maximal oxygen consumption results from the Pre-test and week 5 Post-test further demonstrated that positive performance effects were only evident with the Rotor Q-Rings.”

    More here http://www.rotorbikeusa.com/science.html

  • Alan

    Item 1:
    The placebo effect works even on people who know they are way too smart and experienced to be fooled by the placebo effect.
    Item 2:
    At the lowest effective diameter, either the cranks + feet + legs have to increase their instantaneous angular velocity or there is no torque applied. This continual (twice per crank revolution) acceleration and deceleration soaks up power. The gain in biomechanical efficiency is low and is counteracted by the power required by the oscillations in angular velocity.
    Item 3:
    I have tried oval chainwheels fitted with the long axis parallel to the cranks and at right angles to the cranks. Not much difference. See item 2.
    Item 4:
    See Brenden Smyth’s astute post in this thread on how to use round chainwheels effectively.
    Item 5:
    A cyclist can apply some torque at top and bottom dead centre. See item 4. A piston connected to a crank arm applies *zero* torque at top and bottom dead centre. Oval gears have been made and used in machinery for more than 100 years. When did you last see oval cogs in a gear box or on a steam train?

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