42

If the aluminum is sufficiently stiff it makes zero difference -- the crank could be any shape (a disk, an S shape, etc), but the relationship between the two contact points would still remain the same, and that's all that counts. The only effect the crank could have is adding a bit of spring to the crank, which might be good or bad for effective cranking. ...


25

The comments on the Kickstarter project have a few good explanations of both why the design is effectively identical to a straight crank, and why the plan to make carbon-fiber versions is dangerous. Now leverage: if you tried to push down on the pedal (as shown in the video) when it was exactly top dead center and stopped, it doesn't matter if it is a ...


23

I haven't seen one of those before, but it looks as though it could stop the chain dropping between the bottom bracket shell (the bike frame) and the crankset if you ever drop the chain off the inside of the small ring. When that happens it can be tricky to get it back out, and if the chain is oily you end up with that oil everywhere (mostly on your hands ...


22

I don't think you can make a 3x1 setup work. In order to have the chain change gears, there needs to be a mechanism to take up the slack in the chain. In a normal dual-derailer setup, the rear derailer does that. You might be able to make it work with a chain tensioner, but I'm not sure if you can find one with enough range to do the job as well as a rear ...


21

This is just a rehashing of a very old and horrible idea. See PMP Cranks et al. Edited for additional information: RE: PMP cranks A moment's thought shows a straight crank and an L crank always have the same relation between pedals, chain, and bottom bracket. Thus, there is no advantage to L cranks. And an L crank always has more material than a ...


21

Once loose, the pedal spindle will describe a cone as the crank rotates. This concentrates force at certain points in the crank threads, leading to damage. Top image shows the pedal spindle in the threaded hole in the crank. The threads are fully engaged and tightened, and forces are distributed. Note there is space between the male and female threads (...


16

Saddle height for new bike setup purposes should always be set relative to the pedal, not the BB center or any other reference point. So yes, crank length makes a difference. Using the ground or BB center as a reference point is convenient for re-establishing a given height after the post has been moved, but not for setting up one bike to have the same leg ...


16

I started getting seriously into bike work circa 2002 and was lucky enough to come across Jobst Brandt's view of the topic around that time. Since then, most of which time I've spent working as a mechanic, I've observed that the Brandtian observations of the mechanical dynamics at hand are wholly correct, but I don't agree with him on what to do about it. He ...


15

Unfortunately this doesn't help. The example pictures demonstrate misunderstanding elementary classical mechanics and more specifically, statics. Moment, a.k.a. torque, is defined as M = F * d where F = the force applied d = the perpendicular distance from the axis to the line of action of the force. The shape of the crank has not effect on either. F is ...


15

The system you propose is just a third way to change gear, in a mechanically very complicated way. Any benefit that could be obtained by lengthening the cranks can already be obtained by moving to an easier gear and a bike with two or even three front chain rings and anywhere between five and eleven rear sprockets has plenty enough gear ratios available to ...


15

The bottom bracket spindle is for cottered crank. The bottom bracket looks like threaded one, so it is likely that it can be replaced with square taper or external cup bottom bracket. To tell which thread the bottom bracket has, we'd need to know the exact dimensions.


15

The bottom bracket is not damaged, the left hand crank arm is. You have a 'two piece' crank where the right side crank is permanently attached to a steel axle, and the left hand crank clamps onto the axle with two pinch bolts. The axle has small splines cut into it where the crank clamps on and the crank has corresponding splines cut into it. for the crank ...


14

This is actually a matter of the force multiplication that each chainring provides, and the size/mass of each chainring. Force difference Let's propose, only for a moment that you had a chainring as big that the radius of it is almost the same as the crank length. If the rider stood to pedal while using that chainring (and using simple platform pedals). ...


14

There are multiple components that can contribute to a clicking or grinding sound in your drive train in addition to the bottom bracket, including the chain, the pedals, the derailleur and the rear hub. That said, the symptoms you describe seem to indicate a problem with the pedal bearings or the bottom bracket. Here are my steps for troubleshooting the ...


12

The Giant Reign is a long travel 'enduro' bike that is designed to be ridden down steep technical trails, not pedalled down road/fire trail. It's most likely that changing to a 39-53 will not work as the inner chainring will catch the chain stays, and even if it did work, it would compromise the bike in technical terrain, increasing the chances of '...


11

Here's what I'd recommend As others have suggested, you should avoid a stock bicycle. They're designed with the top of the bell curve in mind, and you're simply half-again as much man as the normal one. For more information on any of these topics, consult a bike shop! Crankset: Since you asked specifically about them, I'll start here. The stiffest, ...


11

There are bicycles with a crankshaft that runs through the rear axle. The "Tur Meccanica Bi Bici" is such a bicycle: I can't tell from your picture if it's the same bike or not, but it certainly could be.


11

Many two wheel drive mountain bikes exist. Here's one article advertising a new one: There’s been no shortage of attempts to build a workable two wheel drive bicycle over the years, but this latest effort from Double of Japan looks like one of the most compelling yet. https://www.bikeradar.com/news/this-is-a-two-wheel-drive-bike-done-right-sort-of/ They do ...


10

Could be any number of things. The first thing to check (because ignoring it can rapidly cause expensive damage) is that the crank arms are tight. Even if they don't seem loose it doesn't hurt to put a wrench on the fixing bolts and torque them a bit. (If one moves more than a small amount, get a torque wrench and do them up right.) Likewise with the ...


10

By "non-drive" I assume you mean the left side. This is more apt to come loose than the right because of "precession" -- most crank bolts are right-hand thread on both sides, but the motion of the crank arm relative to the shaft tends to loosen the bolt on the left side, whereas it tends to tighten the bolt on the right side. But if this is occurring it's ...


10

The clicking, only under load and always at the same point of the stroke, can be due to: A bad pedal. I've had this a couple of times. The crank arm slipping on the crank. Generally if you've been riding it this way for more than 100 miles or so the crank arm (and possibly the crank) will have been permanently damaged, but tightening the fixing bolt may ...


10

Believe it or not in the range of lengths you are looking at there is very little scientific support for there being any real discernible differences in performance (both in absolute power and metabolic efficiency). For the lengths you are considering I would suggest this is largely a personal preference choice. Crank length and maximal power If we are ...


10

The main distinction is whether the puller is for square taper (and Powerspline) versus Octalink/ISIS. Among square taper crank pullers, there are some older ones made with nutted spindles in mind that don't play nice with the now more common bolt-style ones because their tips are too narrow and can jam into the bolt hole and damage the threads. A couple ...


10

The research on subject (source: Wilson & Papadopoulos: Bicycling Science, MIT Press 2004) shows that crank length has very little effect on pedaling efficiency or or maximum power output. There is a small increase in maximum power output with shorter cranks and and in efficiency with longer cranks, and racers who optimize to the last percent do use ...


10

There is little research on the impact of crank length on power output in cycling. There are some lab studies, and they seem to show that even for crank lengths significantly shorter or longer than the norm, the metabolic cost to maintain a specified speed or power output in the lab doesn't change. Importantly, some of these studies included lengths ranging ...


10

You are undertightening the crank bolts on initial installation. 44Nm or 33 ft-lb work well as generic values for square taper cranks. A basic large beam-type torque wrench works well for crank bolts. If you aren't able to get one, it's safe for basic square taper cranks to reef like mad with something like a 12" ratchet or breaker bar. You'll be ...


9

I disagree with the selected answer as most of the provided links are simply opinion without any analytical backing. In terms of choosing a crank length on the basis of performance, there is very little scientific support for there being any real discernible differences widely used crank lengths (160-180 mm). For an overview of some of the scientific ...


9

Well, you're a big guy, so a lightweight racing bike is probably not for you. You might want to look at touring bikes, and, in particular, some of the Surly models. For the crank problem you probably should have a splined vs square crank, and you need to regularly check the torque on the crank bolts.


9

If you keep the rest of the bike the same a shorter crank gives more ground clearance at the bottom of the stroke, and that's going to be the main thing most people notice. You're unlikely to notice a change in power output unless you're shorter than, say, 1.7m, which would put you firmly on the down-slope of the power curve (ie, the part where longer = less ...


9

Yes, you need to replace the crank arm, if tightening the bolt does not make it 100% solid again. No doubt the crank arm had been loose for days, and had you tightened it earlier you might have "saved" it. And there's some danger that you have damaged the crank axle as well, meaning the bottom bracket cartridge will need changing out as well. I have ...


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