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  1. #226
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    I think it would be a good time for me to try and summarize my current understanding of the factors that limit the incline that a mountain bike can climb. I hope that this will help to clarify any confusion caused by the earlier debate.

    This account is only possible because of the many earlier contributions to this discussion. Not just the contributions that have withstood detailed scrutiny, but all of the ideas that made us think hard and led us towards a greater understanding.


    KEY FACTORS INVOLVED: These factors can combine to cause front wheel liftoff. Alternately pushing too abruptly on the pedals, can cause the rear wheel to lose traction and so spin out.

    Load Transfer due to increased incline
    As the hill gets steeper load is transferred from the front to rear wheel. If the weight transfers behind rear wheel ground contact point, then even a stationary bike will flip over backwards.

    Load Transfer due to the rider moving their body-weight Moving the riders body-weight forward can compensate for Load Transfer due to increased incline. Move it too far forward and the rear wheel may loose traction and so spin out.

    The Load Transfer caused by rear wheel Torque Reaction forces( This can happen both when the bike is accelerating or climbing at a constant speed)
    According to Newton's Third Law of Motion every force has an equal and opposite reaction. This means that as a rear bicycle wheel rotates clockwise, the same torque force tries to rotate the bicycle and rider in an anti-clockwise direction. Normally the weight of the rider, pulled downwards by gravity will prevent this from happening. But if the low gear torque is powerful enough the front wheel can lift off the ground. especially when combined with the force of the Load Transfer due to acceleration of the high Center of Gravity.

    Load Transfer due to acceleration
    If a cyclist tries to accelerate in order to get to the top of a hill an additional load is transferred from the front to rear wheel that can cause the front wheel to lift off the ground. This effect is made worse because acceleration will also increase the torque being transmitted to the rear wheel and therefore the upwards front wheel reaction to it.
    Weight transfer - Wikipedia, the free encyclopedia

    The acceleration during a pedal stroke and the deceleration in-between strokes.
    If the slope is steep enough the acceleration during the pedal stroke, combined with the rear wheel torque reaction, can lift the front wheel off the ground. Motorbikes or electric bicycles with there smooth, non-pulsed, power sources do not suffer from this effect and so given enough torque will be able to climb steeper slopes than pedal cycles.

    Steep segway climb - YouTube

    A Segway is able to climb very steep slopes because is is not affected by:

    Load Transfer due to increased incline

    Load Transfer due to acceleration
    (This is because acceleration is proceeded by the rider leaning forward)

    The acceleration during a pedal stroke and the deceleration in-between strokes.

    A Segway is effected by torque reaction but this is countered by the forward lean of the rider. If the rider stops leaning forward the Segway will stop. If the rider leans to fall forward the Segway will accelerate in order to compensate.
    Last edited by GrahamWallace; 10-15-2012 at 02:55 PM. Reason: clarification

  2. #227
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    Quote Originally Posted by GrahamWallace View Post
    If we can get past the question of does torque reaction exist? And is it relevant issue? It may get even more Interesting
    Quote Originally Posted by james-o View Post
    q1 - I think yes, it's part of the forces you feel lifting the front as you pop a wheelie. Weight shift + torque reaction in balance - at that moment the lead foot pushes down, eight moves back and the acceleration / torque and rearward weight shift pop the front up. On a climb, your weight on the front wheel / COG overcomes the pop and you move forwards.
    I agree with that analysis

    Quote Originally Posted by james-o View Post
    Q2 - I think no, it's a smaller component in a larger force system if you climb in 'normal' balance.
    I also agree that torque reaction is a lesser issue than the acceleration and resultant weight shift caused by each pedal stroke.

    Quote Originally Posted by james-o View Post
    With COG at infinite height above but same position between the wheelbase, the bike wheelies again, I see the points made there. But If the COG is 'tied' to the bike, ie muscles acting in arms and legs, maybe not - muscle input mean the forces here are too complex for diagrams.
    Sometimes insight can be gained by considering the extreme limits of a problem, even if these are unachievable in reality. In this case the inertia and infinite leverage of an infinitely high CoG, attached via a rigid second class lever would prevent the bike from moving at all. And this ultimate example of an inverted pendulum would take an infinite amount of time to unbalance. let alone to fall down.

    Quote Originally Posted by james-o View Post
    At climbing gradient limits, torque resulting in wheelspin, or positioning on the bike compromising power output and/or balance is the issue. Or the wet/rocky/ etc terrain.
    It's all too variable and complex to model imo, but I appreciate the force diagram points as it's food for thought (and some confusion, followed by 'maybe I'll just go for a ride'!)
    True, but some times the theoretical modeling of a problem can lead to insights that can then be applied to real situations.

    I will be using the understanding gained from this discussion to further improve the climbing ability of Cleland bikes.

    The maximum slope that a current mountain bike can climb is just above 20 degrees, but a Segway can climb a 40 degree slope. Why can't a bicycle not do the same? This question has been answered here in theoretical terms but can the problem be resolved in reality. I believe that it can!
    Last edited by GrahamWallace; 10-07-2012 at 02:00 PM. Reason: Typos

  3. #228
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    It turns out that with the use of certain search terms like: motorbike "Load Transfer" and "motorbike squat" that there is a fair amount of information on the internet relating rear wheel torque reaction. Though almost always in relation to the effects on motorbike suspension.

    I also found this Wikipedia Talk page relating to bicycles where the learned Wikipedians also get confused.
    Talk:Bicycle suspension - Wikipedia, the free encyclopedia

    This is not the first time,that the notion that torque reaction forces are distinct from load transfer forces, has been considered in the design of a Cleland style bike. I designed this energy efficient rear suspension system in 1992.
    Cleland: The original big wheeled off-road bicycle?-suspension1992.jpg
    The rear swing arm is pointed up towards the CoG in order to neutralize the load transfer forces, whilst the torque reaction is used to counter rear wheel squat . The system was intended to have pre-loaded springs (no-sag), to eliminated vertical bobbing of the CoG.

    The gearing is in-between the twin seat tubes and the chain to the rear wheel runs inside the rear sub-frame tubing.
    Last edited by GrahamWallace; 10-07-2012 at 02:58 PM. Reason: clarification

  4. #229
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    Though I never built this high pivot point suspension system. But I did describe the concept in detail to a British engineer called David Wrath-Sharman whose company, Highpath Engineering, manufactured Cleland style bikes. In 2004 he made this bike called the TopTrail, that he, and car suspension designer Adrian Griffiths had enginnered.

    Name:  2004 TopTrail.jpg
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    This is a classic piece of Cleland lineage' blue skies thinking. A first class example of "first principle engineering" in which Citroen style interconnected hydro-pneumatic suspension, is adapted for use on bicycles.

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    On very rough ground, a Cleland the rider will stands bolt upright "on the pegs", whilst the front and rear wheels rock seesaw like beneath his feet. On this bike, despite the pitching of the wheels and frame the handlebars and saddle remain amazingly still. This allows the rider can remain seated and pedaling un-interupted whilst the suspension does all the work.

    High_Performance_Bike_with_Interconnected_Suspensi on.mpg - YouTube

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    Last edited by GrahamWallace; 10-09-2012 at 04:07 PM. Reason: Typos

  5. #230
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    Quote Originally Posted by GrahamWallace View Post
    Though I never built this high pivot point suspension system. But I did describe the concept in detail to a British engineer called David Wrath-Sharman whose company, Highpath Engineering, manufactured Cleland style bikes. In 2004 he made this bike called the TopTrail, that he, and car suspension designer Adrian Griffiths had enginnered.

    Name:  2004 TopTrail.jpg
Views: 1748
Size:  50.6 KB

    This is a classic piece of Cleland lineage' blue skies thinking. A first class example of "first principle engineering" in which Citroen style interconnected hydro-pneumatic suspension, is adapted for use on bicycles.

    Name:  5143a046b0b895845e5e5d9071faa2d2_full.jpg
Views: 1325
Size:  38.7 KB

    On very rough ground, a Cleland the rider will stands bolt upright "on the pegs", whilst the front and rear wheels rock seesaw like beneath his feet. On this bike, despite the pitching of the wheels and frame the handlebars and saddle remain amazingly still. This allows the rider can remain seated and pedaling un-interupted whilst the suspension does all the work.

    High_Performance_Bike_with_Interconnected_Suspensi on.mpg - YouTube

    Name:  2975f4dde1007255ad0bb1f966e85fbc_full.jpg
Views: 766
Size:  24.1 KB
    Very intriguing design.
    I'm interested in how the "high anti-squat" is achieved. Since the chain and therefore chain tension (the mechanism for every other anti-squat design I'm aware of) are routed very close to the pivot point, the effect of chain tension is neutralized. In fact, with the pivot point below the chain tension vector, it appears on the surface that the design would be pro-squat. What prevents chain tension from pulling upward on the axle? The "high anti-squat angle" is cited, but without the chain tension effect I'm at a loss for how it is realized.
    Enlightenment...?
    On a related note, the explanation will probably illuminate how severe pedal feedback associated with high anti-squat is avoided on rough terrain during "uninterrupted pedaling," but I'm not seeing it at the moment.
    Last edited by meltingfeather; 10-09-2012 at 08:41 PM.
    Quote Originally Posted by pvd
    Time to stop believing the hype and start doing some science.
    29er Tire Weight Database

  6. #231
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    Quote Originally Posted by meltingfeather View Post
    Very intriguing design.
    I'm interested in how the "high anti-squat" is achieved. Since the chain and therefore chain tension (the mechanism for every other anti-squat design I'm aware of) are routed very close to the pivot point, the effect of chain tension is neutralized. In fact, with the pivot point below the chain tension vector, it appears on the surface that the design would be pro-squat. What prevents chain tension from pulling upward on the axle? The "high anti-squat angle" is cited, but without the chain tension effect I'm at a loss for how it is realized.
    Enlightenment...?
    On a related note, the explanation will probably illuminate how severe pedal feedback associated with high anti-squat is avoided on rough terrain during "uninterrupted pedaling," but I'm not seeing it at the moment.
    The reason that I posted images of these high pivot point bikes is that the main anti-squat mechanism is the rear wheel torque reaction.

    By placing the pivot in a "sweet spot" under the CoG the torque reaction vector at the pivot can be contained. Placing the rear swing arm pivot and the center of the top chain cog was a mistake I made on my 1992 design. Consider a situation where the rider pedals hard whilst the rear brake is applied. The top jockey-wheel over which the chain is routed is prevented from rotating by the chain and the rear swing arm then acts as a first class lever with the load at the rear axle, the fulcrum at the swing-arm pivot and the input at the point where the chain rests on the jockey-wheel. This would cause the rear to squat and would also do so in other situations that create high levels of rear wheel drag like hill climbing and high acceleration. The arrangement on the TopTrail simply stops a lever being created by placing the input and fulcrum at the same place.

    The TopTrail is amazing in that it works at all. A high center of gravity bicycle with interconnected suspension where the front wheel rising causes the back to fall, should in fact, ride like a rocking-horse. The successful use of anti-dive and anti-squat systems to stabilize everything is quite remarkable.

    Many people say that this design is too complicated to build and must be heavy. But the use of carbon fiber reinforced molded sections would both reduce weight and the complexity of the space-frame.

    I did go on to build full suspension Clelands using Renault Sport's NRS system. But these behave exactly like rigid bikes until they hit a bump. The TopTrail however is much smother as it isolates the rider from not only bumps, but the pitching of the bike.

    The Toptrail Interconnected Suspension Bicycle Project

    Cleland NRS:
    [Cleland NRS 2010 | Flickr - Photo Sharing!
    Last edited by GrahamWallace; 10-10-2012 at 09:38 AM. Reason: clarification

  7. #232
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    Quote Originally Posted by GrahamWallace View Post
    The reason that I posted images of these high pivot point bikes is that the main anti-squat mechanism is the rear wheel torque reaction.
    To me the use of "torque reaction" is confusing and I don't yet understand how it is accurate, if it is.
    A drive force at the rear axle would cause the suspension to rise by virtue of the pivot placement. I don't see the role of "torque reaction." Even if there was no torque applied and someone were to push at the axle from behind by way of some type of yoke, the anti-squat would still occur.

    Quote Originally Posted by GrahamWallace View Post
    The TopTrail is amazing in that it works at all. A high center of gravity bicycle with interconnected suspension where the front wheel rising causes the back to fall, should in fact, ride like a rocking-horse. The successful use of anti-dive and anti-squat systems to stabilize everything is quite remarkable.
    It's certainly interesting, and takes some pretty involved mental modelling to understand. I'd love to ride one.
    Quote Originally Posted by pvd
    Time to stop believing the hype and start doing some science.
    29er Tire Weight Database

  8. #233
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    Quote Originally Posted by meltingfeather View Post
    To me the use of "torque reaction" is confusing and I don't yet understand how it is accurate, if it is.
    The torque reaction is proportional to the torque applied at the rear wheel whilst chain tension is dependent on the combination of cogs being used.

    Quote Originally Posted by meltingfeather View Post
    A drive force at the rear axle would cause the suspension to rise by virtue of the pivot placement. I don't see the role of "torque reaction." Even if there was no torque applied and someone were to push at the axle from behind by way of some type of yoke, the anti-squat would still occur.
    The clever bit is that the "Torque Reaction" force is being balanced against the "Load Transfer force with the weight/inertia of the rider pinning everything down. The "Torque Reaction" is trying to lift the CoG whilst the "load Transfer" forces are trying to move the CoG downwards. For this to happen the position of the rear swing-arm pivot is crucial and this was what I meant by "sweet-spot". In reality you are still left with a vertical component that when combined with the upward force of the springs will cause the CoG to lift vertically. This can be countered by damping or pre-loading the springs.

  9. #234
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    You should try climbing a steep hill on a modern mountain bike. Fat knobby tires, tubeless. Dual suspension, with at least 5 inches( 125 mm) of travel. Low gearing, important as to keep even steady pedaling. Most importantly, the rider. I've seen riders climb more than 20 degrees. He was on a single speed pugsly. Mind over matter. All this theory stuff is interesting but somewhat not the most important. I go on many group mt bike rides. Why on a steep section do only 3 out of 10 make it up ? Skill, technique and strength are some of the factors you are overlooking.

  10. #235
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    Quote Originally Posted by leeboh View Post
    You should try climbing a steep hill on a modern mountain bike. Fat knobby tires, tubeless. Dual suspension, with at least 5 inches( 125 mm) of travel. Low gearing, important as to keep even steady pedaling. Most importantly, the rider. I've seen riders climb more than 20 degrees. He was on a single speed pugsly. Mind over matter. All this theory stuff is interesting but somewhat not the most important. I go on many group mt bike rides. Why on a steep section do only 3 out of 10 make it up ? Skill, technique and strength are some of the factors you are overlooking.
    You are right about the rider skill aspect and the fact that I enjoy hill climbing is probably a factor in being good at it. The problem that the physics are complicated enough without factoring in the subtleties of riders skill. I do ride up very steep hills on my relatively modern Giant NRS Carbon full suspension bike which is pretty good despite a tendency to steer where it wants to and not necessarily where I want it to go. But it is still not as capable and assured as my un-sprung 1983 Cleland.

    The use of elliptical gearing improves the climbing limits of modern bikes as it allows for a slower cadence and reduces suspension bobbing. It also improves rear rear wheel traction and reduces the probability of front wheel lift.

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  11. #236
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    Impressive. Looks like a modern Dursley-Pedersen!

    The 3 bike comparo on a rough track on the Toptrail site was interesting. While it's not what I'd call a rough track, it was enough to show a considerable difference. To my mind the relative silence of the Toptrail suspension would almost be worth it on its own. What I saw there overcomes most of the reasons for my dislike of suspension.
    As little bike as possible, as silent as possible.
    Latitude: 5736' Highlands, Scotland

  12. #237
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    Quote Originally Posted by Velobike View Post
    Impressive. Looks like a modern Dursley-Pedersen!
    But in the Victorian era groundbreaking bicycle designs got manufactured. Today the British cycle industry is content to churn out the same old designs whilst proclaiming minor improvements as major developments.

    The TopTrail is unique in being a collaboration between top automotive suspension designer Adrian Griffiths, and the ingenious British mountain bike pioneer/engineer, David Wrath-Sharman. David who was pictured at the very beginning of this thread riding a Cleland certainly knows how to ride off-road. So despite the lack of challenging riding shown on the TopTrail website, this bike is bound to be a highly capable machine.

    I wonder how many "industry" bicycle designers would understand this design?
    And I severely doubt that any could be this inventive and creative.

    Will the TopTrail or an updated version ever be manufactured?

    I very much doubt it.

  13. #238
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    Quote Originally Posted by meltingfeather View Post
    To me the use of "torque reaction" is confusing and I don't yet understand how it is accurate, if it is.
    Amen brutha.

  14. #239
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    Quote Originally Posted by GrahamWallace View Post
    I think it would be a good time for me to try and summarize my current understanding of the factors that limit the incline that a mountain bike can climb. I hope that this will help to clarify any confusion caused by the earlier debate.
    Most of your summary is ok. I'm not going to go through it. It seems however that you have not progressed at all in your thinking about torque reactions, so I will quit trying, but to respond to this:


    Front wheel lifting caused by rear wheel torque ( This can happen both when the bike is accelerating or climbing at a constant speed)
    According to Newton's Third Law of Motion every force has an equal and opposite reaction. This means that as a rear bicycle wheel rotates clockwise, the same force tries to rotate the bicycle and ride anti-clockwise.
    NO.

    You posted somewhere earlier that you could push on a rear wheel and make the front end of a bike lift off the ground. Well, post the youtube video showing this. I'm not going to argue, just make it happen.
    When you understand that this is impossible, you wil have a better understanding of the foces on the bicycle, and you will have to revise your "torque reaction" theory.

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