Lightweight Frame Tubing and "Planing"

bicipunk · #1 10-01-2017, 07:09 PM

Hey all, this came up in another thread and I didn't want to go too off topic so I'm starting a new one. I'm looking into a new custom, low trail, 650b randonneur and from reading the reviews of bikes in Bicycle Quarterly, I've become interested in lightweight tubing and what the BQ folks call planing. I weigh between 160 and 170 depending on the season and am more of a spinner. My question is if folks seem to think that lightweight tube specs such as .7-.4-.7 tubes and Kasei fork blades would be too light of a spec for a rider like me on that type of a bike? The bike will typically carry a 10-15 lb loads with the occasional 30-40 more pounds on the fork on lowriders for the weekend camping trip, light touring, etc. Any insights y'all can offer would be greatly appreciated! Framebuilder's insights would be particularly appreciated

eddief · #2 10-01-2017, 07:20 PM

is tough to design into a bike...in my opinion. You happen into it or luck into it cuz it is a magical phenomenon. I think a builder can set you in the right direction for sure and plump low pressure tires are a giant step in the right direction, but no builder will tell you he can design planing into the build. As much about tires as metal tubes, especially with weight hanging from the bike.

I swear my el cheapo modern Fuji Touring was a planer.

https://www.performancebike.com/weba...QaAmiHEALw_wcB

Custom-butted Elios 2 chromoly frame with rack and fender mounts
Elios 2 Chromoly fork features low-rider rack mounts

ultraman6970 · #3 10-01-2017, 07:59 PM

Paper thin tubes and rando is not like a combination I would recommend for anybody. Specially if you want the frame to last you for a very long time.

adampaiva · #4 10-01-2017, 11:34 PM

I'm about 15 lbs heavier than you and put my bikes through a lot. I have a Lyon L'Avecaise with the BQ formula tubing (and 650b) and it does plane, or I think so anyway. I rode it for 40 miles today about half on mountain bike trails and half on gravel and dirt carriage roads. I hit a surprise rock and went over the handlebars. I went down a rocky rooty descent at 30 mph. I bunny hop off the occasional rock and curb. So far, the bike has held up to all the abuse with nothing to show of it. (Touch wood)

I'm curious if there's any hesitation from builders on the Toei fork blades (I have them) and using low rider panniers.

buddybikes · #5 10-02-2017, 05:47 AM

We obtained a abosolutely great Bilenky tandem made from super thin aerolite tubing in the 1990's. bike has long since put away due to back issues - examined it, there is a rust hole in the rear seattube. thin stuff - between denting an rusting do you really want that kind of concerns?

Peter P. · #6 10-02-2017, 06:10 AM

Some explain planing to me, please!

eddief · #7 10-02-2017, 06:15 AM

https://janheine.wordpress.com/2014/...at-is-planing/

https://janheine.wordpress.com/2014/...cs-of-planing/

cnighbor1 · #8 10-02-2017, 11:22 AM

Quote:

Originally Posted by adampaiva

I'm about 15 lbs heavier than you and put my bikes through a lot. I have a Lyon L'Avecaise with the BQ formula tubing (and 650b) and it does plane, or I think so anyway. I rode it for 40 miles today about half on mountain bike trails and half on gravel and dirt carriage roads. I hit a surprise rock and went over the handlebars. I went down a rocky rooty descent at 30 mph. I bunny hop off the occasional rock and curb. So far, the bike has held up to all the abuse with nothing to show of it. (Touch wood)

I'm curious if there's any hesitation from builders on the Toei fork blades (I have them) and using low rider panniers.

'' I hit a surprise rock and went over the handlebars. I went down a rocky rooty descent at 30 mph.'' a ? Both you and the bicycle or just you has you went over handlebars

adampaiva · #9 10-02-2017, 11:51 AM

heh. No, separate incidents. The over the handlebars thing basically happened in slow-motion.

timto · #10 10-02-2017, 12:14 PM

As mentioned above too - the BQ spec type bike is thin walls AND small (std) diameter tubes with stiff chain stays (typically round or ror). I've goofed around with many permutations of tube diameter and wall thickness but have yet to build with kaisei blades...

My personal observations for the BQ type frames are as such (at 160 lbs)

With front bag and weight = more prone to shimmy
Skinny tubes make the bike feel like a handful when really reefing on the bars / sprint type efforts with bigger gears
Tempo riding while staying on top of the gear does feel nicer on a nice flexy bike vs a super stiff one and accelerating with leg speed vs higher gear and torque feels like flying on a super flexy bike. A nice feel.

Other observations for this genre of bike
650b @ 38mm felt like they didn't maintain their momentum as well as 700 c wheels at 38mm
Low trail handles just as nice without weight as with weight (easy to get used to)
Fenders and horizontal drop outs are too finicky (go vertical)
Lots of accessories makes for a heavy to pick up bike
If it's a dream bike consider the bag/decaleur/rack up front/lighting details up front

If I were making a bike for a power rider, someone who liked leaning on the pedals in huge gears and pulling on their bars, or who was really tall (big frame) or heavy I wouldn't use std tubing diameters and thin walls. If I were build a city beater that would get locked up to poles and stuff I wouldn't use super thin walls either.

Also I also don't believe the other claims such as more power, or less leg pain but I do know I like the feel of a flexy (within reason) frame. Feels really great. I don't race. I enjoy a more flexy bike over a stiff bike any day. So much so I've stopped looking at racy race bikes all together.
FWIW
Tim

cachagua · #11 10-02-2017, 12:25 PM

Mr. Heine says,

Quote:

Finite element analysis models have shown that almost all energy that you input into the frame as flex gets returned into the drivetrain, powering the bike. This stored energy is released when the pedal stroke approaches the dead spots.

Let's think. Your leg pushes against the bike (speaking in the abstract) and the resistance to acceleration pushes against it in the other direction, and the frame deflects from the force. Like a spring, yes. Think of your frame as a giant bobby pin, pinched between your foot and your back tire's contact patch.

Then as your leg presses a little less -- as you approach the dead spot in your stroke -- and as the force it's applying drops below the force the frame has stored, the frame unsprings and "gives back" that energy. Good so far.

And where does that energy go? Toward which side of the squeeze, as we pictured it, on the bobby pin of your frame? Does it go toward the resistance at the rear wheel, or does it go the other way?

Goes toward the side where the opposing force is lower, presumably. And the side where the force is lower is not the resistance at the rear wheel -- that has remained constant through the whole process. The side where the force is lower is your leg, which is coming around to where it can't push as hard.

Therefore I don't think you actually "get back" the energy that goes into frame flex in forward motion -- you get it back, essentially, in slowing down your legs. The energy stored in the spring of your frame can't accelerate you because there's somewhere easier for it to go. I don't deny Jan's experimental results, and I think a little twang in a bike frame can feel nice and be useful, but I don't think it's for that reason. The second half of that quote above looks right, but the first half I think has a hole in it somewhere.

Or am I not seeing this accurately at all?

Mark McM · #12 10-02-2017, 12:31 PM

Theory and hypothesis aside about how a rider might generate more power with a flexible frame ...

If a flexible frame that "planed" could allow a rider to generate 15% more power (as claimed in the second article), than why wouldn't professional racing teams use such frames? A 15% difference in power would vault a middle-of-the-pack racer into being an untouchable winner. Heck, that's probably a bigger advantage than blood doping can provide. That kind of improvement could not be ignored, even if you wanted to for business/financial reasons. I call BS.

disspence · #13 10-02-2017, 01:08 PM

Quote:

Originally Posted by Mark McM

Theory and hypothesis aside about how a rider might generate more power with a flexible frame ...

If a flexible frame that "planed" could allow a rider to generate 15% more power (as claimed in the second article), than why wouldn't professional racing teams use such frames? A 15% difference in power would vault a middle-of-the-pack racer into being an untouchable winner. Heck, that's probably a bigger advantage than blood doping can provide. That kind of improvement could not be ignored, even if you wanted to for business/financial reasons. I call BS.

I agree. 15% more power is quite the claim. If it is true that all riders could generate 15% more power with the frame flex described, then this would be adopted by the pro peloton.

GregL · #14 10-02-2017, 01:18 PM

Quote:

Originally Posted by disspence

I agree. 15% more power is quite the claim. If it is true that all riders could generate 15% more power with the frame flex described, then this would be adopted by the pro peloton.

Another engineer jumping on this band wagon. The "planing" articles are glorified opinion pieces, NOT well-researched scientific studies.

Greg

El Chaba · #15 10-02-2017, 01:46 PM

15% increase in power output?..what a load....However, I have to testify that a bike built with light gauge tubing in standard diameter can feel fantastic. I have a Peugeot (Pro 10) built in very early 1982 that is made with Reynolds 531 with 0.5 mm tubing save for the top tube which is *believed* to be 0.3 (you can squeeze it). The bike has the greatest ride characteristics, and I can fully understand why somebody would coin a term such as "planning" to describe it. Of course, there are no free lunches and you wouldn't want to have the bike fall over into the corner of a brick wall....It's also not the best bike that I have ever ridden for stomping up a short steep hill in the big ring, but you can still do it especially if you make enough grunting and heavy breathing sounds to drown out the sound of a little front derailleur rubbing...I think that light gauge tubing might a fair portion of the "magic" that is often attributed to many of the bikes built by constructeurs such as Rene Herse and Alex Singer. They really tended to go light except for the full campeur models or the ones built for tall or heavy riders.