# Bicycle Mechanics - Crank Design (for your approval) :)

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Fairmont
05-24-11, 01:46 PM
I have an idea for a crank design. I doubt it's new or original, and might not even be possible or even more efficient, but it's in my mind and I thought I'd burden your time with it.

When cranks go in a circle, I can't help but think that there is only a short amount of distance around the circle in which much force is being applied. The rest is lateral movement, right? For example: When one pedal is down and the other is up, then the top pedal must be pushed forward while the lower pedal pushed backward. It seems like wasted time and energy to do that.

So, what if pedals only went straight down and straight up, so that the full weight and pressure from the rider is put on one of the pedals at all times?

I sketched a rough diagram (not accounting for gearing) that shows the general idea. And the entire shaft could be rotated somewhat for standing, sitting, etc. (angle).

Keep in mind that in this diagram, I only drew one pedal. This is the right side of the bike. The other pedal is on the other side at the opposing point in the chain (so that the pedals are always half-way around the "circle" from each other).

Anyway, enjoy:

http://teacherweb.com/GA/CrabappleLaneElementary/MichaelFairbanks/Crank-Design.JPG

On another note: Why hasn't anyone designed a bike in which it is driven by rowing, as in a boat (only you obviously face forward instead of backward, as is common in a rowboat).

I wonder if that would be a good way to build upper body strength while providing transportation.

Monster Pete
05-24-11, 02:01 PM
There's been early examples bikes driven by levers that move in an arc, something similar to your idea, but for some reason the more common crank prevailed. Unlike a piston and crank, you can apply power forwards and backwards on the pedal to some extent as well as just up and down. This means that a conventional crank doesn't have too much of a dead spot in its rotation.

Rowbikes also exist, basically using a long chain connected to a handle at one end and sprung at the other, wrapped around a freewheel. They offer an immense upper body workout, and are probably more interesting than a stationary machine for training if there's no convenient river nearby. Handcycles are another good option, even if you have use of your legs. Theoretically you could build a bike powered by both arms and legs- probably with legs powering the rear wheel like a conventional recumbent bike and hand cranks driving and steering the front wheel- giving a whole body workout while getting you somewhere.

MilitantPotato
05-24-11, 02:02 PM
There's a video of some 1970's-ish design that does just that. Though they'd certainly show it in the best light possible, it did look pretty effective.

I think they used strings of some sort, and independent pedals.

Lenaxia
05-24-11, 02:03 PM
The rowing bikes already exist

http://rowingbike.free.fr/ramebike-2.jpg
http://rowingbike.free.fr/

As a rower myself, I can say that rowing has too much going on for me to be comfortable riding it anywhere other than on a MUP. It may be simplified since you're not on water (not having to worry about boat set or steering) but you probably wouldn't be able to react quickly i.e. if someone right hooks you.

Fairmont
05-24-11, 02:06 PM
I thought that maybe, with the design I drew above, all one would need is his or her weight to move the bike. If your weight is on the right foot, the pedal descends, and the bike moves. Then you essentially stand up on your left foot (as your left leg was previously bent.

Booger1
05-24-11, 03:10 PM
How you planning on hooking a pedal to a chain and keep it tight(pedal and chain) and make it go over a gear?
I think a treadle drive is close as you can get with an up/down movement.

fuzz2050
05-24-11, 04:47 PM
Look up an Alenax bike. There really isn't anything new under the sun, at least when it comes to bicycles.

BCRider
05-24-11, 05:18 PM
In looking up the Alenax reference I found these two on You Tube for lever driven bikes.

http://www.youtube.com/watch?v=gDH_OcepG4s&NR=1
http://www.youtube.com/watch?v=V3g58pxlb8c&NR=1

The first looks like the arc of the arms is working quite well with the leg motion. However getting on and off this beast seems rather difficult due to how the arms are working.

The pedal positions in the second link seem more "normal" and would be nicer for casual riding.

The use of arms that travel in an arc would appear to be easier to build up. Although the drive system in the Hanna-Dean setup is far too complex. But as a proof of concept for arms instead of rotating cranks it's interesting.

In the end I suspect a switch to reciprocating arms for pedalling would be more appropriate if the rear hub axle were hollow and served as the pivot point for the arms which then drove directly into an internally geared hub. But of course that may not produce the optimum arc of travel for the arms. It may well be that the best option is something along the lines of the Hanna-Dean setup but with the chains off the upper rear portion running directly to the rear hub instead of through the "normal" placement.

As for a rowing bicycle that's just a bad idea. To get the most power out of our bodies the legs and arms would all need to operate together. To do this AND steer a two wheel vehicle that basically has a prone feet first rider trying to "scull" their way down the road or path while somehow steering and balancing is just way too much for the average rider. The trike shown by Lenaxia at least takes away the balancing requirement and the need to be able to put a foot down at stops. But as mentioned it does little to encourage awareness of the rower/rider's surroundings. Besides, we're already using most of the more powerful muscles in the body in terms of the legs and lower abdomen.

rwhite2
05-24-11, 07:08 PM
As for a rowing bicycle that's just a bad idea. To get the most power out of our bodies the legs and arms would all need to operate together. To do this AND steer a two wheel vehicle that basically has a prone feet first rider trying to "scull" their way down the road or path while somehow steering and balancing is just way too much for the average rider. The trike shown by Lenaxia at least takes away the balancing requirement and the need to be able to put a foot down at stops. But as mentioned it does little to encourage awareness of the rower/rider's surroundings. Besides, we're already using most of the more powerful muscles in the body in terms of the legs and lower abdomen.

Here's one that uses both the arms and legs. It's also pretty easy to steer after a little practice. Still more suited to exercise than transportation, though.
http://www.rowbike.com/

fuzz2050
05-24-11, 07:23 PM
Here's one that uses both the arms and legs. It's also pretty easy to steer after a little practice. Still more suited to exercise than transportation, though.
http://www.rowbike.com/

They also make an awful lot of noise.

Mr Gnome
05-24-11, 07:40 PM
So, what if pedals only went straight down and straight up, so that the full weight and pressure from the rider is put on one of the pedals at all times?

Do mean like an elliptical exercise bike? It's been there and it's done that and they are for sale. Well, they don't go 100% straight down and straight up.

Bob

davidad
05-24-11, 11:22 PM
Been done. OUr thing is almost 200 years old. The main changes lately are because of material improvements. Everything that can be done has been done and is occasionaly resurected.

Jeff Wills
05-25-11, 12:57 AM
As for a rowing bicycle that's just a bad idea. To get the most power out of our bodies the legs and arms would all need to operate together. To do this AND steer a two wheel vehicle that basically has a prone feet first rider trying to "scull" their way down the road or path while somehow steering and balancing is just way too much for the average rider.

I guess these guys ain't average:

http://www.youtube.com/watch?v=zvPucDbmUPo

Jeff Wills
05-25-11, 01:06 AM
So, what if pedals only went straight down and straight up, so that the full weight and pressure from the rider is put on one of the pedals at all times?

I've seen such an arrangement, with pedals attached to a chain that traveled over two sprockets. It used a couple additional lever arms to keep the pedal from twisting the chain. It was at a Taiwan trade show a year or 2 back.

It's one of many designs that shows up every once in a while with some imagined benefit. Even when the benefit is real, implementing the design compromises so many other things in the drivetrain that any gains are lost to mechanical inefficiency. That's life.