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#63 ·
Those have opposition or think lever theory about curved cranks, if their viewpoint is correct, why people so surprise curved crank’s efficiency after riding.

As I know the efficiency comes from the gravity of cranks forward , in other words, toe-out effect. The calculation formula is not using lever theory but using trigonometric function to calculate its effective force area

According to maker’ data, they did integral calculation by every 10 degree then total work got 33% efficiency that is compared with traditional straight crank.
On upper dead point , straight crank is vertical to axle ,so most of pedaling force are　lost on this angle. However sickle crank not only center gravity forward but also effectively pass through upper dead point and reduce loss, so output increases by 33% compared with straight crank..


My personal opinion

There are two kinds of scientist since long time ago- practice and laboratory scientists.
Science calculation is to explain nature phenomenon not simply to examine its possibility. The sickle crank’s efficiency is fact and proved. It is said that SGS was surprised, too when they got result.


The follows comes from official website

1. calculation formula( by every 10 degree)
According to this data you can see torque output is bigger than straight crank before 160 degree and get more efficiency from 0 ~130 degree. Reduced force loss in the max pedaling force losing zone , so curved crank can get more torque output.
Straight crank is better than curved from 160~180 degree , however, it is in the low pedaling force losing zone ,besides on 180 degree position , the other crank already on the 0 degree(upper dead point) to start new circulation.

If using clipless pedal to pull from low dead point , the efficiency will be as same as 0~130 degree. One leg pedal and the other leg pull by clipless pedal , it will get multiple effect

2.SGS Test report ( official website)

3. USA Cyclist used computer trainer to test, AVE HR reduced 11 bpm，maximal oxygen consumption reduced 9%；MAX HR reduced 5 bpm，maximal oxygen consumption reduced 4%


I installed one set. When pedal harder , I could feel the explosive power form rear wheel .If I constant speed ride , the pedal seems be driven by certain force and automatically pass through upped dead point.
Some one had pedaled 53t gear and his rpm increased 20%. My experience is using front 56t and rear 11t , feel as same as 50 t gear. The speed is very fast and easy to reach 40km/h, well, because it is 56t. Some friends got good physical condition they could easy to reach 50~55km/h


One of my riding course is 20km and 9.75km is a slope. The slope is average 3.5% and last 2km is 7.5% slope. It took 90 minutes to run this course, but used this sickle crank , it only takes 70 minutes. 20% faster.

From these riding experience , I know it really get efficiency

Sharing this information for you guy . If you want know more riding experience , you may check out official website.
 

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#65 · (Edited)
celine0711 said:
Those have opposition or think lever theory about curved cranks, if their viewpoint is correct, why people so surprise curved crank's efficiency after riding.
.
Click to expand...
The idea has been around for a very long time. There is one example shown above from 1983. If these actually do work as advertized, why has not a single competitive professional rider adopted these?

I am trying to figure out if you are even serious:confused:

You do realize that the table of torque calculations is complete nonsense, right? They don't actually tell you what they are plugging into the formulas. Thing is, they SHOULD be plugging in the exact same numbers for the curved and the straight cranks at each crank position, so the mathematical results should be the same. The fact that they are getting different values means they are plugging in different values. I can't believe I am even having to explain this to you.
 
#67 ·
celine0711 said:
1. calculation formula( by every 10 degree)
According to this data you can see torque output is bigger than straight crank before 160 degree and get more efficiency from 0 ~130 degree. Reduced force loss in the max pedaling force losing zone , so curved crank can get more torque output.
Straight crank is better than curved from 160~180 degree , however, it is in the low pedaling force losing zone ,besides on 180 degree position , the other crank already on the 0 degree(upper dead point) to start new circulation.

If using clipless pedal to pull from low dead point , the efficiency will be as same as 0~130 degree. One leg pedal and the other leg pull by clipless pedal , it will get multiple effect
Click to expand...
I took a look at the chart and did a quick calculation. I can't read Kanji but if I'm interpreting the chart correctly, the highest force shown is developed at 180° which is 1 N*mm. Run through the math of a force applied as if it were at the outer most point of the crank on a 170mm average crank length and assuming the force applied is not a distributed load across the crank arm (which is it, but let's assume best-case scenario). If you did that, (and if I did it correctly) then you would come out with 1 N*mm applying a 0.6g force.

For reference, a sheet of standard printer paper weighs about 18g.
 
#69 ·
They should make these out of depleted uranium. The efficiency would be off the charts and they would make your ankles glow!
 
#74 ·
Wow I didn't know George Bush had sterted building bike parts.

Question is ??? Is this closer to the truth than anything else he has said ???????

Sounds like 1 of his claims. Well if it wasn't for the fact it was only 30% out.:D
 
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