Thanks for all the comments so far. Some assumptions/approximations for the dynamic model:

As soon as I heard PowerPoint, I was waiting for 'aged 5' to appear 😂. Crackin' vid 👍🏻

Worst thing about this video was that it ended! Really informative and thoughtful analysis of something I’m currently trying to get my head around. Thanks 👍

I have difficulty accepting crank length is not effecting torque, this video and others state that you manage that with gearing and cadence. I see two machines working, just like an engine and a gearbox. The engines is making power and gearbox is putting it to the ground, ignoring crank length i fel is like ignoring bore stroke in an engine saying it's all in the transmission 🤔 The transmission is a ratio device who needs power externally

Don't forget the beer belly effect! For a lot of riders I see, reducing the hip angle means that the knees don't hit the gut LOL.

Warren Buffet is a total Fred.

Been riding for 30+ years. Always had 170s, am 5' 7", and noticed that I always had trouble accelerating from a dead stop, or ever, as compared to my taller compadres. Switched to 165s about 10 years ago and, man, what difference! Changed everything. And now I know why. Thanks so much for this.

“Can’t be arsed to convert imperial to metric” ....

Great video ! With the reduction of crank length, should your model not also increase the seat height since the maximum extension of the leg is correspondingly shortened when the shorter crank is a the bottom of the rotation? That would open up the hips even more.

colors are missing from your legends for your graphs

You start out with hip angle-but you seem not to be emphasizing KNEE angle-and opening that up is a big deal if you have knee pain or a knee injury. I went shorter and it was

Being a shorter rider (173cm) I changed from 170 cranks to 165 a few years ago, it changed my life on the bike.

2 key problems I have with this analysis are failure to adjust seat height with crank length and the acceleration analysis assuming consistent velocity.

"Let's put some numbers to it" thank you! The lack of data and sound reasoning behind most discussions/debates in cycling has driven me nuts!

Fascinating study you’ve done here. I’m very interested in following your progress. My academic background was in Human Factors Engineering and Ergonomics many years ago before I started cycling. I have been searching for an analysis just like yours. I like that you also mentioned leg mass as well. I am about 185 cm tall with large feet (size 47), and big legs. I also have fairly long tibias. I do not use a power meter but I do get the feeling that I cycle better with shorter cranks. The joint angle I am concerned with is the knee. There is a very powerful fulcrum there as well and I want to continue to preserve my 65 year old knees. I haven’t measure power but is seems to me I am able to generate more power at the pedal with the more open knee angle a shorter crank provides. Knee angle and hip angle are related but I haven’t paid attention to hip angle. I look forward to seeing your next video on the subject. Thanks!

Oh man this brings back dynamics and kinematics studies from uni... Love it.

Wonderful video. I have been considering shorter cranks because of intuition only, now I am starting to understand due to your excellent work

Beautifully done; loved the analysis!

I moved fom 172.5 to 165mm to alleviate anterior knee pain. I also have te seat forward & raised. So much more comfy in the drops or TT position. Great vid!

Good analysis. I ride long cranks (old school 185 and 180mm). Recently I have a bike with shorter (175mm) cranks. The feeling is very different. My second ride with the bike resulted in "exploded" legs after 75km. You really need to adjust to it timing wise. My cadence did not change (94rpm average). In several studies they changed crank length and tested in a short period of time. That would never give a good result.