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  1. #251
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    Eating my hat

  2. #252
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    Nice demonstration Graham. Thank you for that.
    Looking at the video it is easy to see now that the chain tension is creating a force vector at the bottom bracket with a direction along the chain which travels above the rear axle, and therefore creating a moment about the rear axle. I was previously picturing the chain tension to be centered on the rear axle and therefore creating no rotation about it.

    I still have some issues with the term "torque reaction". I have to think about it some more. To me, Newtons 3rd law in this case means that the chain pulls on the hub and the hub pulls on the chain. In this case, those forces create torques, but in a general sense a torque doesn't always create an equal and opposite torque. I will ponder this and post later.
    But that's a god video. Thanks for doing it.

  3. #253
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    Hi Steve,

    I use the term 'torque reaction' in that the normal output torque of the drive chain is reversed. And I see no reason, given the low friction nature of the drive chain, why the new 'alternative' output force would not equal the normal output for a given input force. Therefore it appears to comply with the 'equal and opposite' conditions of Newton's third law.

    Whether this fits within the received wisdom of what constitutes a classic torque reaction in physics is indeed an interesting question. It is conceivable that this is in fact a type of reverse motion mechanism that mimics the characteristics of an actual torque reaction. And I appreciate any insight that you and others may be able to bring to this question.
    Last edited by GrahamWallace; 06-05-2015 at 10:44 AM. Reason: typo

  4. #254
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    No good

    Quote Originally Posted by smilinsteve View Post
    Post a YouTube video and show that you can fix a rear wheel to the ground, push on the crank and make the front end lift. It will never happen. It's impossible. Instead of 3 years of confusion, you could have done a 15 minute experiment to help you find the truth in this.

    The only points of attachment between the drive train and frame are at the bottom bracket and the rear dropout. Both these are attached by bearings so no torque can be transferred to the frame. Zero.


    Nature happens. Physics is just humans trying to explain it to themselves. So all the issues with humans and their communication apply. As demonstrated FTW lololol =D Repetition isn't fun but it works, one more time now...

    https://www.youtube.com/watch?v=JZVC0BCHIFg

  5. #255
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    Quote Originally Posted by GrahamWallace View Post
    ...Whether this fits within the received wisdom of what constitutes a classic torque reaction in physics is indeed an interesting question. It is conceivable that this is in fact a type of reverse motion mechanism that mimics the characteristics of an actual torque reaction. And I appreciate any insight that you and others may be able to bring to this question.
    Apart from action and reaction forces being equal and opposite, Newton's third law usually has these forces acting in the same place. i.e. a foot pushing on a paving stone means that the paving stone must also be pushing back against the foot. Or in terms of torque reactions, both action and reaction forces act at the same center of rotation.

    But with this bicycle drive chain mechanism, the input force at the pedal is some distance from the reaction centered on the rear axle. And so this mechanism appears to differ from from the usual torque reaction models.

    However, if you consider the pedal, crank, the chain and frame as just a means to deliver the force to the rear cog and the reaction force back again , then this example does fit in with other models of torque reaction. i.e. action force vector forward along the chain, reaction vector lower down along the chain-stay and a moment of rotation created due to the distance between axle and the chain contact point at the top of the cog. And all forces acting on the same center of rotation, the rear axle.

    Also with the chain parallel with the chain-stay the the forces acting along each will be equal and opposite. However, most action and reaction forces measured elsewhere in the mechanism/bicycle may not be equal, due to variations in mechanical advantage or velocity ratio.
    Last edited by GrahamWallace; 06-05-2015 at 10:42 AM. Reason: typo

  6. #256
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    Cleland: The original big wheeled off-road bicycle?

    Quote Originally Posted by GrahamWallace View Post
    I use the term 'torque reaction' in that the normal output torque of the drive chain is reversed.
    I think your use of the term torque reaction is what threw me. I thought you were implying that the rear wheel was somehow imparting torque on the bicycle frame.
    The front end of the bicycle lifting is due to the magnitude and direction of the chain tension relative to the rear axle/pivot point.
    Once the chain tension multiplied by its distance from the axle exceeds the weight of the bike & rider multiplied by the center of mass's distance from the axle, the bike will lift.
    Quote Originally Posted by pvd
    Time to stop believing the hype and start doing some science.
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  7. #257
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    Quote Originally Posted by deepfraught View Post
    douchebaggery definitely helps.
    Quote Originally Posted by pvd
    Time to stop believing the hype and start doing some science.
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  8. #258
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    Quote Originally Posted by meltingfeather View Post
    I think your use of the term torque reaction is what threw me. I thought you were implying that the rear wheel was somehow imparting torque on the bicycle frame...
    The fact that the bicycle frame rotates clearly indicates that a torque is being applied to it. I would explain it in terms of the constrained torque in the rear wheel taking the path of least resistance, back along the chain.

    When I first noticed this back in the 1990s I called it the 'drawbridge' effect, due to the similarity with the chain mechanism used to open castle' drawbridges. In this analogy the wheel and rear cog represents the castle wall, the drawbridge chain the bicycle chain, and the drawbridge the bicycle frame.

    I guess if you bolted the open drawbridge to the ground and applied enough force through the chains, the resultant torque would cause the castle to raise up instead of the drawbridge. But don't ask me to post the video.
    Last edited by GrahamWallace; 06-20-2015 at 12:57 PM. Reason: claricication

  9. #259
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    Cleland: The original big wheeled off-road bicycle?

    Quote Originally Posted by GrahamWallace View Post
    The fact that the bicycle frame rotates clearly indicates that a torque is being applied to it. I would explain it in terms of the constrained torque in the rear wheel taking the path of least resistance, back along the chain.

    When I first noticed this back in the 1990s I called it the 'drawbridge' effect, due to the similarity with the chain mechanism used to open castle' drawbridges. In this analogy the wheel and rear cog represents the castle wall, the drawbridge chain the bicycle chain, and the drawbridge the bicycle frame.

    I guess if you bolted the open drawbridge to the ground and applied enough force through the chains, the resultant torque would cause the castle to raise up instead of the drawbridge. But don't ask me to post the video.
    I think I understand the confusion now.
    There is a difference between applied torque and applied force, and both can cause rotation. The fact that an object rotates does not mean necessarily that torque was applied, as it was not in the case of your bicycle. Chains or cables can not apply torque, only linear tension.
    If I lift a wheelbarrow with vertical linear force at the handles (not torque), the fact that the wheelbarrow rotates about it's axle does not mean that somehow the force I applied was changed into torque and the pushback of the wheelbarrow's weight against my hands magically becomes a torque reaction.
    Quote Originally Posted by pvd
    Time to stop believing the hype and start doing some science.
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  10. #260
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    Quote Originally Posted by meltingfeather View Post
    Chains or cables can not apply torque, only linear tension...
    True. However linear tension applied above or below the wheel axle (or axis of rotation) of an object will be converted into a torque. In the drawbridge analogy any linear force applied to the bridge that is not aligned with the bridge's axis of rotation (hinge) will be converted into a torque.

    Likewise any linear force, applied to a cyclists head in an accident, that does not pass through the head's Center of Mass/rotation will be converted to a torque. This rotation is the reason why cyclists in accidents can suffer brain damage even when their helmets show little sign of damage.

    Quote Originally Posted by meltingfeather View Post
    ...If I lift a wheelbarrow with vertical linear force at the handles (not torque), the fact that the wheelbarrow rotates about it's axle does not mean that somehow the force I applied was changed into torque and the pushback of the wheelbarrow's weight against my hands magically becomes a torque reaction...
    What you suggest could be true if the wheelbarrow's wheel was free to roll back and forth and you ignored any effect resulting from the barrow's inertia. But if the wheel cannot rotate, then the handles will follow a circular path around the wheel and the initial linear force acting on the handles would be converted into a torque.
    Last edited by GrahamWallace; 06-20-2015 at 03:35 PM. Reason: claricication

  11. #261
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    Cleland: The original big wheeled off-road bicycle?

    Quote Originally Posted by GrahamWallace View Post
    True. However linear tension applied above or below the wheel axle (or axis of rotation) of an object will be converted into a torque. In the drawbridge analogy any linear force applied to the bridge that is not aligned with the bridge's axis of rotation (hinge) will be converted into a torque.

    Likewise any linear force, applied to a cyclists head in an accident, that does not pass through the head's Center of Mass/rotation will be converted to a torque. This rotation is the reason why cyclists in accidents can suffer brain damage even when their helmets show little sign of damage.



    What you suggest could be true if the wheelbarrow's wheel was free to roll back and forth and you ignored any effect resulting from the barrow's inertia. But if the wheel cannot rotate, then the handles will follow a circular path around the wheel and the initial linear force acting on the handles would be converted into a torque.
    The fact that a force causes rotation does not convert the force into torque.
    All forces can impart moments, but applied forces and applied torques and their respective reactions are fundamentally different things.
    This may be semantic... I think I get where the confusion was caused and it may be a communication issue rather than a fundamental lack of understanding, however by standard definitions used in physics/statics your claim above is incorrect.
    Quote Originally Posted by pvd
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  12. #262
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    Quote Originally Posted by meltingfeather View Post
    The fact that a force causes rotation does not convert the force into torque.
    All forces can impart moments, but applied forces and applied torques and their respective reactions are fundamentally different things.
    This may be semantic... I think I get where the confusion was caused and it may be a communication issue rather than a fundamental lack of understanding, however by standard definitions used in physics/statics your claim above is incorrect.
    A standard definition of a torque is "a force that makes an object turn around an axis". Usually measured in Newton meters. There are three components: the magnitude of the acting force, its direction and its its radius from the axis of rotation.

    Given this and that we are talking about forces acting on rigid bodies. Like bicycle frames, wheels etc, where the axis of rotation is fixed relative to the force. Can you explain exactly why my analysis is fundamentally incorrect?

    Or at least point me towards the area of physics where forces applied to stationary rigid bodies with that have a mass and a fixed axis of rotation, causes rotations of the rigid bodies where no torque is generated?

  13. #263
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    Quote Originally Posted by GrahamWallace View Post
    A standard definition of a torque is "a force that makes an object turn around an axis". Usually measured in Newton meters. There are three components: the magnitude of the acting force, its direction and its its radius from the axis of rotation.
    A torque always causes rotation because it is a "twisting force."
    A torque is either clockwise or counter clockwise and has a magnitude described in Nm. You are confusing this with a simple force and the moment it imparts when summing moments about some axis as in a statics problem.
    Quote Originally Posted by GrahamWallace View Post
    Given this and that we are talking about forces acting on rigid bodies. Like bicycle frames, wheels etc, where the axis of rotation is fixed relative to the force. Can you explain exactly why my analysis is fundamentally incorrect?
    The fundamentally incorrect part is that a linear force somehow magically becomes a torque because it causes rotation in the body it is acting on. This is very basic stuff and what you are saying is simply incorrect.
    Quote Originally Posted by GrahamWallace View Post
    Or at least point me towards the area of physics where forces applied to stationary rigid bodies with that have a mass and a fixed axis of rotation, causes rotations of the rigid bodies where no torque is generated?
    My wheelbarrow analogy and your bicycle video are perfect examples of this. In both cases the body is lifted by a linear force acting on it, not a torque. The fact that the bodies are supported at a pinned connection that determines that the resulting motion is rotation does not mean that my hands start twisting (applying torque to) the wheelbarrow handles or that the bicycle chain somehow starts twisting the chainring. A chain can NEVER apply a torque. All forces impart moments... all you have to do is pick an axis to sum moments about that he force vector does not intersect and voila, a moment associated with the force can be described. That does not mean that the force becomes a torque somehow.
    Not lapping this again.
    Could be semantics like I said, but the words you are stringing together are not consistent with the very basic definitions used to describe forces and force balances.
    Good luck.
    Quote Originally Posted by pvd
    Time to stop believing the hype and start doing some science.
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  14. #264
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    Quote Originally Posted by meltingfeather View Post
    The fundamentally incorrect part is that a linear force somehow magically becomes a torque because it causes rotation in the body it is acting on. This is very basic stuff and what you are saying is simply incorrect.
    Can you produce a force vector diagram of an instance where a linear force makes a an object turn around an axis, with no rotational force and so is not a torque?

    Quote Originally Posted by meltingfeather View Post
    ...or that the bicycle chain somehow starts twisting the chainring. A chain can NEVER apply a torque.
    But is not the chain twisting the chainring fundamental to the workings of bicycle gearing? Big chainring more torque, small chainring less torque, for a given linear force in the chain?
    Last edited by GrahamWallace; 06-21-2015 at 03:51 AM. Reason: claricication

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    Cleland: The original big wheeled off-road bicycle?

    Quote Originally Posted by GrahamWallace View Post
    Can you produce a force vector diagram of an instance where a linear force makes a an object turn around an axis, with no rotational force and so is not a torque?
    The simplest is analogous to the wheelbarrow: a beam with a pinned connection at one end and a vertical linear force at the other. The force is not a torque. It does not twist. It is linear. It causes rotation.

    Quote Originally Posted by GrahamWallace View Post
    But is not the chain twisting the chainring fundamental to the workings of bicycle gearing? Big chainring more torque, small chainring less torque, for a given linear force in the chain?
    No it is not.
    The chain does not twist the chainring. It pulls on the chainring with linear force. The chain does not apply a torque to the chainring.
    You are confusing terms and concepts.
    Torque (a twisting force) is applied to the bottom bracket spindle by the crank arm. The bottom bracket spindle pushing back is a torque reaction.
    Rider's feet pushing on the pedals is not torque and the pedals pushing back against the rider's feet is not torque reaction.
    Quote Originally Posted by pvd
    Time to stop believing the hype and start doing some science.
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  16. #266
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    Quote Originally Posted by GrahamWallace View Post
    Can you produce a force vector diagram of an instance where a linear force makes a an object turn around an axis, with no rotational force and so is not a torque?
    Quote Originally Posted by meltingfeather View Post
    The simplest is analogous to the wheelbarrow: a beam with a pinned connection at one end and a vertical linear force at the other. The force is not a torque. It does not twist. It is linear. It causes rotation.
    See attached.
    Attached Thumbnails Attached Thumbnails Cleland: The original big wheeled off-road bicycle?-imageuploadedbytapatalk1434992668.423567.jpg  

    Quote Originally Posted by pvd
    Time to stop believing the hype and start doing some science.
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  17. #267
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    Folks reading this thread might appreciate my frankenbike. It was originally a bmx cruiser with 24" wheels. After awhile I went 24/26, then dual 26, and finally 26/27.5.

    Putting a 26" rear wheel and a 27.5" front wheel on the bike has of course made the bike handle completely differently. For one, with larger front wheel and a longer fork the geometry is more relaxed. Although the bottom bracket is higher than it was with 24" wheels, the feel still works for me. Because of the short wheelbase and the laid-back rider position, the bike is pretty fun on technical descents. That same setup gets a little more sketchy as the speed picks up but it is still stable enough to descend with conviction. It handles predictably but it's much different than my other more traditional mountain bikes. The 5 inch riser bmx cruiser bars put me in a position where it's easy to lift the front end up. They are just short of 28 inches wide so I have plenty of leverage.

    The rear brakes arms were machined out of an old crank arm, and the other parts were cobbled together from other sets of rim brakes. Given the extra length of the caliper arms, they are extremely powerful.


    On climbs it requires a bit more body english to make it over obstacles but the bike does have gobs of rear wheel traction. The drivetrain is a bit unusual but so is everything else on this bike. It is a 3x8 that goes
    18/26/38x12-15-18-23-28-34-38-42. I spend most of my time in the 26t middle ring. It's nice to have some super low bailout gears because the bike is not exactly light.
    Attached Thumbnails Attached Thumbnails Cleland: The original big wheeled off-road bicycle?-0606051856.jpg  

    Cleland: The original big wheeled off-road bicycle?-0606051856a.jpg  


  18. #268
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    BTW. If you are wondering about the seatpost, it goes halfway into the frame. It is quite long.

  19. #269
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    looks like the stem is flipped 180. High center of gravity and DH = OTB
    The wheel is a extension of the foot

  20. #270
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    Never have gone OTB with this one.

    It might be OTB for someone not familiar with the bike or someone with poor handling skills. The rear weight bias helps alot. I have gotten used to it. Been riding bmx and mtn since the mid 1980's. I have decent descending skills regardless of which bike so the short wheelbase is not as much of a hindrance as it could be. It's certainly not as stable or fast as my 27.5ers and my 29ers but it's very manageable and pretty fun.

    Actually the stem is put on the same direction as any other stem on my bikes or anyone else's.

  21. #271
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    Hi Meltingfeather, Thanks for uploading the force vector diagram of the wheelbarrow and sorry for the slowness of my reply, but it has been a very busy week for me.

    Before I give a detailed reply there is one thing that still puzzles me regarding your comments below...

    Quote Originally Posted by GrahamWallace
    But is not the chain twisting the chainring fundamental to the workings of bicycle gearing? Big chainring more torque, small chainring less torque, for a given linear force in the chain?
    Quote Originally Posted by meltingfeather View Post
    No it is not.
    The chain does not twist the chainring. It pulls on the chainring with linear force. The chain does not apply a torque to the chainring.
    You are confusing terms and concepts.
    ...
    Whilst I agree that the force the chain applies to the chainring is not a torque. Some of my bicycle science books and numerous internet sources, including Sheldon Brown, refer to the chain tension being converted to a torque at the rear sprocket. I take it that you would agree with them?

    Excerpt from the Sheldon Brown website:
    "Now, let's assume a 50-tooth chainwheel. This has a radius of about 4 inches, or 0.33 feet. We can now calculate the chain tension:

    50.4 pound-feet/0.33 feet = 153 pounds.

    We'll assume a 20-tooth sprocket, with a radius of 1.6 inches -- 0.13 foot at the rear wheel. The 153-pound chain tension produces a 20.2 pound-foot torque at this sprocket:"
    Understanding torque as it applies to bicycles
    Last edited by GrahamWallace; 06-26-2015 at 11:37 PM. Reason: claricication

  22. #272
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    Cool vids and pics. Reminds me of early ATBs (pre-MTB) made by adapting BMX stuff and road bike ders to old Schwinn frames and beach cruiser tires. Our goal in the late 70's was never speed or distance (Midwest didn't lend itself to true mountain adventures), but difficult trials-like trails. The best bikes we road where either the 26/24 cannondales or the Gary Fisher raised chainstay montaire's or similar bikes.
    The most expensive bike in the world is still cheaper than the cheapest open heart surgery.

  23. #273
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    Hi Forster,

    The Clelands were the equivalent in Britain of the early US Schwinn Excelsior, Breezer and Ritchey bikes etc, but with more of an off-road touring ethos. I guess the modern day equivalent of a Cleland would be Fat Bike.

    Whilst the US pioneers used 26" Uniroyal Knobbies, Cleland designer' Geoff Apps used larger diameter 700c and 650b Nokia' Hakkapeliitta snow tires from Finland instead. But unlike the US mountain bikes, the Cleland designs never became popular. Though Apps' sending the Finnish tires to the American proved to be influential, both at the time and over the following decades, due to their use by US bike builder Bruce Gordon.

    As well as building the first 700c wheeled mountain bike in 1981 Apps can also be credited as being the first person to manufacture 650b mountain bikes from 1982 to 1984.

    His first 1981 700c wheeled prototype has now been restored. Here are some photos...

    dCleland: The original big wheeled off-road bicycle?-restored-700c-1981-range-rider.jpgCleland: The original big wheeled off-road bicycle?-1981-700c-cleland-range-rider-frame.jpgCleland: The original big wheeled off-road bicycle?-1981-cleland-range-rider-during-restoration.jpg
    Incidentally, the earliest pictures of this bike that I can find are in the first ever book on mountain bikes written by Rob Van der Plas and first published in 1984.
    Last edited by GrahamWallace; 06-27-2015 at 02:01 AM.

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    Funny Bruce Gordon's name entered the conversation, I just installed a set of his Rock n' Roads on my Fargo and was thinking about how "retro" those tires seemed, very much like skinny versions of the IRC Trials tires from the period. I wouldn't mind seeing a similar pattern in wider sizes (like 2.2s) with slightly wider knob spacing (to clear mud). I always wondered if the internal brake hubs would stand up to our riding back in the day. I was lighter (170#s), but 4' drops were killing the best hubs I could afford at the time so I never tried them.
    The most expensive bike in the world is still cheaper than the cheapest open heart surgery.

  25. #275
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    Quote Originally Posted by Forster View Post
    Funny Bruce Gordon's name entered the conversation, I just installed a set of his Rock n' Roads on my Fargo and was thinking about how "retro" those tires seemed, very much like skinny versions of the IRC Trials tires from the period. I wouldn't mind seeing a similar pattern in wider sizes (like 2.2s) with slightly wider knob spacing (to clear mud).
    In 1980, Geoff Apps heard about the Ritchey mountain bikes and contacted Gary Fisher and Charlie Kelly. As a result of the correspondence they asked Apps to send over a sample 650b Nolia' Hakkapeliitta tire and Ritchey built a frame to fit. They were so impressed that they asked Apps to send over as many 650b and 700c tires as he could obtain. It appears that a few years later the 700x47c version came to the attention of Bruce Gordon who then built bikes to fit these large diameter tires.

    Around 1984, Fisher lost interest and stopped importing the Hakkas from Apps. And when the 700x47c versions ran out, Gordon had copies made that he called the the "Rock 'n' Road". The Ibis' Hakkalugi model was also named after these Finish tires.

    Here are some pictures of Nokia' Hakkapeliitta tires:
    Name:  hakkatire.jpg
Views: 1057
Size:  64.7 KBName:  1977e.jpg
Views: 100
Size:  33.1 KB

    And below are some Bruce Gordon' Rock 'n' Road versions:
    Cleland: The original big wheeled off-road bicycle?-1988-bruce-gordon-rock-n-road-tire.jpgCleland: The original big wheeled off-road bicycle?-rock-n-road-prod-detail.jpg


    You can still buy 54mm x 650b Hakkapeliitta tyres as they are still popular in Finland and they also make a 35mm wide 700c version.


    Quote Originally Posted by Forster View Post
    I always wondered if the internal brake hubs would stand up to our riding back in the day. I was lighter (170#s), but 4' drops were killing the best hubs I could afford at the time so I never tried them.
    The hubs used by Apps were designed for use on French mopeds. They are simple, very robust with the bearings being insulated from the braking surfaces that are extremely well cooled. They also have a floating input cam that improves braking power by compensating for the uneven brake shoe wear problem that is commonplace with brake hubs.

    In the past 30 years I have never seen one of these hubs fail though I have seen some bent axles.

  26. #276
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    Great to see the 700c bike finished Graham. Did you ever post it on that other forum? I didn't see it if you did.

  27. #277
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    Quote Originally Posted by firedfromthecircus View Post
    Great to see the 700c bike finished Graham. Did you ever post it on that other forum? I didn't see it if you did.
    No, this is the only forum at present where I have posted pictures of the restored bike.
    I have some pictures of the restoration and so I will create a thread covering this and the bikes history when time allows.

  28. #278
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    Quote Originally Posted by GrahamWallace View Post
    No, this is the only forum at present where I have posted pictures of the restored bike.
    I have some pictures of the restoration and so I will create a thread covering this and the bikes history when time allows.
    I shall look forward to it.

  29. #279
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    If anyone's interested, here's a link to where you can see photos of the latest Cleland:
    https://crosscountrycycle.wordpress....17/by-the-way/

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