F = ma

So... what you really need is a psychologist for your mechanic?

This engineer can't be bothered. He's about to make ladies uncomfortable at a party.

You might be able to have the best of both worlds. Can you position the FD so the chain rubs and the crankarm hits it?

Sounds like a smart mechanic :innocent:.

Jim, good to see you finally putting that advanced degree to work.

That's brilliant!

Energy loss due to friction, rubbing and grinding on a bike is not a tolerable question......regarding the fairer sex? There are special forums for that :rolleyes:

But seriously, no one believes you'd ride more than a few hundred feet with a rub or a click, just impossible.

It might depend on how hard you ride. If you ride hard, the chain rubbing against the derailleur could cause a greater loss of energy than the banging of the crank against the derailleur. The friction from the chain rubbing is likely to increase as your effort increases. On the other hand, the crank bangs the derailleur when you're applying more power to the opposite crank, so the crank banging the derailleur is probably not banging it hard. And that force decreases as your pedaling effort increases.

So if you're tooling around, let the chain rub. If you're mashing hard, let the crank bang.

Can he say that?

Let's see...

71 plus six

times 99

divided by 2 or 3

Added on to 360.



32.

You know, you're right. I hate extraneous noises. But for some reason, I didn't notice this one on a previous ride--or maybe I forgot, that's a problem when you have too many bikes. And my question is really about what I should do at the moment once discovering the problem. I wasn't going to go to the nearest house and ask if they have any Pre-CPSC Campagnolo front derailleurs. I was going to keep riding, having to make such a difficult choice.

Um, yeah, twss.

I think we have a winner.

.
...has anyone yet considered the weight savings gained in comparing the two different mechanical interference mechanisms as a function of time ?

Good point! The wearing away of material due to rub/contact needs to be factored in!

For that matter, isn't the terrain around Boston rather flat? Could probably go with a single ring up front and remove the FD entirely. :p

+1 this. I see this problem often with vintage Stronglight and TA cranks.

Okay, I'm convinced this FD is a POC. Anyone want to trade me a lip-less Campy NR or SR for this post-CPSC SR model? (and, yes, I'm serious--straight trade.)

Surely you are joking, Mr. Feynman?

Great book, sorry I loaned it out.

Anyone knows a Record front derailleur has less friction than a Super Record as there are no holes to catch the chain pins on from classic 3/32" derailleur chains.
Why do you think Campagnolo went from 4 cage holes to 3? Surely not for aesthetics.

The constant rub will reduce material, achieving a lower mass, at the same time, the rider exerting additional force to overcome said fricture will convert mass to energy at a higher rate........maybe it's good they rub?

It could also be that the derailleur is not rotated right. The outer plate of the derailleur needs to be parallel with the outer surface of the big ring.Sight the derailleur cage against the chainring, and see if the derailleur is not parallel. If it isn't, make it right and you'll maximize the clearance between the chainring and the crank arm.

That's kinda what I was thinking. What I would do, if I were paid commensurately that is, is conduct a controlled experiment with both configurations, with careful weighing of the affected parts before and after. The parts with the greatest loss of mass will be on the configuration with the most net drag.

Ah, that's why you engineers want to study everything over time--you're paid by the hour!

There's nothing wrong with your SR front derailleur; it's just not designed to work with pre-CPSC cranks. As I have a number of vintage cranks that need the pre-CSPC version, I'm reluctant part with any usable front derailleurs. Other front derailleurs that will work include Zeus Criterium, 1st edition Dura-Ace, SunTour Compe, SL, or 1st edition Cyclone, and Simplex Super LJ, among others.

I think the answer is to drink more and listen less.
That's what I do when encountering physics.

This is clearly the result of the Greek banking crisis. Since you can only take 60 euro's at a time from the atm, you will have to wait a couple of days to gather the funds to buy a new FD.

Thanks for the advice, John. I currently have five different bikes in the fleet with Stronglight or TA cranks; four of them have FDs from among the group you mentioned. For this fifth one, I thought I might sneak in something with more bling, but I've been denied. But I do have more options in the bin, none Campy pre-CPSC.

Good thinking, sir!

That's why I'm trying to barter. Eff those banks!!

I think I have something for you, Neal, but it will be some days before I can check, and I will have forgotten by then, so: good luck with that! :thumb: