sreten

Hi,

I resent yet another personal comment.

But will repeat again the precession of bearings has nothing
to do with the phenomenon, the bearings do not turn the BB
cup, they transfer the rotating torque, and the precession
occurs between the BB cup and the thread it is in.

(Just consider a loosely threaded BB cup, it's obvious,
if it isn't you don't understand bicycle precession).

Once the cranks start actually moving regarding the BB
I can now see a ratcheting mechanism for continually
undoing the nut or bolt which I wasn't considering.

Probably my fault for not explaining enough, but I was
considering a damaged crank, tightened back onto the
crank so it cannot move, but not set onto the crank
properly, so torque can transfer to the bolt / nut.

What initially undoes the very tightened bolt/nut.

I still think pulses of sideways forces through the edges of
the bolt / nut cause it to initially undo due to precession.

My prognosis was if you file the damage out of the
crank, so it can seat properly, that will fix it, as it
prevents torque transfer to the bolt/nut.

Worked for me.

rgds, sreten.

cny-bikeman

Still waiting....

sreten

Hi,

Go out and look yourself. If you think precession cannot and
does not occur between two threaded parts there is no point
discussing the matter. It's been understood for over a century.

rgds, sreten.

cny-bikeman

1. So far you are the only source making that claim - all I'm asking for is one credible source that supports your position.
2. That would be a non-sequitur, as the only reason for discussion in this thread is the existance of that very disagreement.
3. Again, as you appaently are aware of the time of initial discovery or initial positing of precession of threaded parts perhaps you can guide us to the source of that information.

Until then I'm posting to this one no longer.

sreten

Hi,

Toys and pram, you won't go out and find out for yourself.

Pretty much IMO, because you know I'm not stupid,
and you have a very good idea of what you will find.

rgds, sreten.

I have explained things elsewhere in this thread and
so far no-one has found analytically any fault with
with what I'm saying, just pointless contradiction.

Airburst

I don't know how you do things, but generally in a debate it's traditional to provide your own sources when asked, rather than asking people to go out and find them for themselves. Citation needed, and all that.

If it helps, assume we're all far less intelligent than you and that we therefore can't find the sources of information you're using, so you have to show us them.

sreten

Hi,

Simply put no it is not. If your going to argue the toss about
every simple detail in a engineering "debate" you really don't
know your onions and the "debate" is essentially meaningless.

All typically known facts are a given for all engineering, and
there is no requirement to back up what you are saying, the
onus is on anyone arguing to prove you are wrong if you are
going out in a limb, when your not, there is no debate.

(Just saying I don't think that is right because I don't
agree, is not debate, its ignorance the way I see it.)

If you don't get what I'm saying, ask a question.
I'm pretty good at explaining stuff, but cannot do
with no that is wrong its like this wikipedia blurb,
(which only shows no understanding, not some).

I'm quite happy to argue about the details of pedal
and bearing precession with no sources whatsoever,
because I'm an engineer and want to understand it.

If you have problem with the fundamentals, its your job,
not mine, to know what you are allegedly talking about.

rgds, sreten.


I can design a rather good hifi power amplifier - IMO.
If you think I need to be able to explain it to all and
sundry and they will instantly understand why it is
good, you really don't understand good engineering.

Airburst

Now who's going for the personal attacks? Don't bother, being a female engineering student I get enough crap from people assuming I don't know what I'm doing, usually based on even less evidence than you have. It just bounces off now, so unless you have a particularly interesting piece of evidence as to why I don't understand engineering leave the insults out, they're not doing anyone any good.

OK then, how exactly is it that precession loosens left-hand crank bolts, and how do you account for right-hand cranks occasionally coming loose, as I've seen them do?

sreten

Hi,

Your pushing the boat out there implying its personal, note the If,
and post signature, implying a general related point to ponder for all.

Right hand cranks come loose, but generally if you retighten them
you generally have far less problems than trying to retighten the left.

My thinking regarding precession and toasted cranks has already
been outlined in this thread and there in no point repeating it.

Though the short version is with damaged cranks retightened
onto the crank the left is more problematic due to precession.

rgds, sreten.

cny-bikeman

Well I had to look up "toys and pram" to understand you were saying I'm a spoiled child looking for attention - this from the person claiming personal attacks toward him. Couching it in a cute Brit expression does not make it any less insulting, nor any less contrary to the tenor of this forum.

Your assumption about my reason for asking for empirical support are baseless and presumptuous. I'm not going to go looking for support for YOUR position because it's not up to me to prove it. Your position flies in the face of every other poster's knowledge as well as references they have cited, so yes it is up to you to prove your position in something other than words.

Everyone has found fault with your analysis as far as I can see - you have merely decided that any disagreement, no matter how well explained (by people who obviously understand engineering), is "pointless contradiction." You have in fact been dead wrong or at least ill-informed on other posts where you have given advice, so your record hardly argues for taking your position at face value. Finally, anyone who so inconsiderate or so careless as to drop contraction apostrophes and use your for you're is hardly careful enough to trust to proper analysis.

sreten

Hi,

It doesn't mean quite that applied to Adults,
as I understand it, but I'm not going to explain.
(It is an observation of apparent behaviour.)

The rest of your post is not worthy of a reply.
It is inaccurate and meaningless self-deception.
You can wallow in it thinking it makes out you are
right, but it really just illustrates your personality.

rgds, sreten.

If you want to try to fix/save a "toasted" crank, I'm your
man. I've fixed cranks that are "toast" according to most.

(I set off on the left, being a lefty, and lefties who
do the same generally have a lot more problems with
cranks than most, in that respect I'm no exception.)

For my road bike with softer alloy cranks and a steel
BB you need to stand on the pedal and the ratchet
and bounce up and down to get it tight enough to
not come undone on the left, not so the the right.

cny-bikeman

In reverse order:

I'll be sure to post a crank over the pond to you next time I find a toasted one. Seriously I don't waste my time fixing a toasted crank when I can install a new one. I can afford the crank better than the time, and if I were still working in a shop I could not warranty the repair. Nobody said you should not choose to fix your own, though standing on a ratchet is a great way to bottom out or fracture the crank arm.

Most people, right or left-handed, mount from the left side and as has been noted that is a well=known probable cause of the left loosening more often.

You fail to point out what is inaccurate or meaningless, and you are hardly qualified to judge someone else's self-deception.

Comments about my personality and insults such as self-deception and wallowing, as well as the toys and pram comment are not appropriate in a technical discussion, or for that matter anywhere in this forum. As such it's an excellent way to end this thread and hopefully truncate some of the more inflammatory portions. If you had not escalated to a personal, insulting level I would have hewed to my original stance of not posting until you provided support for your theory.

Goodbye.