Search the FAQ Archives

3 - A - B - C - D - E - F - G - H - I - J - K - L - M
N - O - P - Q - R - S - T - U - V - W - X - Y - Z
faqs.org - Internet FAQ Archives

Rec.Bicycles Frequently Asked Questions Posting Part 4/5
Section - 8f.11 Installing Cranks

( Part1 - Part2 - Part3 - Part4 - Part5 - Single Page )
[ Usenet FAQs | Web FAQs | Documents | RFC Index | Schools ]


Top Document: Rec.Bicycles Frequently Asked Questions Posting Part 4/5
Previous Document: 8f.10 Cracking/Breaking Cranks
Next Document: 8f.12 Biopace chainrings
See reader questions & answers on this topic! - Help others by sharing your knowledge

> My cranks get loose, quite quickly too; over about 10 miles or so
> from being solid to flopping about in the breeze.  Any suggestions?
 
Your cranks are ruined!  Once ridden in the "floppy" mode, the square
taper in the crank can no longer be secured on the spindle.  Get some
new cranks and properly tighten them after lubricating the tapers.
Proper tightness can be guaranteed only by torque wrench or a skilled
mechanic.  The second of these is less expensive and you might be able
to get a demonstration of what is tight enough.

The admonition to not lubricate the tapers of the crank spindle seems
to find life only on bicycle cranks, of all the machines I have seen.
I have pursued the "dry assembly" instruction by talking to crank
manufacturers and discovered that they apparently had warranty claims
from customers who split their cranks open.  It is easy to prove that
cranks cannot split by over-tightening simply by attempting to do so.
It is not possible to split a major brand crank this way, the bolt
will fail first.

Crank failure from "over-tightening" is caused by the re-tightening of
previously properly installed cranks.  Once installed, a crank always
squirms on its taper, and because the retaining bolt prevents it from
coming off, it elbows itself away from the bolt and up the taper ever
so slightly.  This can be detected by the looseness of the retaining
bolt after the bicycle has been ridden hard.

Grease in this interface does not affect performance, because only the
press fit, not friction, transmits load from crank to spindle.  As any
bicycle mechanic can tell you, crank bolts are often appreciably
looser after use, the left one more so than the right.  This occurs
because the left crank transmits torque and bending simultaneously
while the right crank transmits these forces one at a time.  The right
crank puts no significant torque into the spindle.  Either way, the
looseness occurs because loads make the crank squirm on the spindle
and the only direction it can move is up the taper, the retaining bolt
blocking motion in the other direction.

Regardless, whether grease or no grease is used, in use the spindle
and crank will make metal to metal contact and cause fretting
corrosion for all but the lightest riders.  The purpose of the
lubricant is to give a predictable press fit for a known torque.  If
the spindle is completely dry this cannot be said, and even with
marginal lubrication, some galling may occur on installation.
Lubrication is only used to guarantee a proper press because the
lubricant is displaced from the interface in use.  Taper faces of
spindles show erosion and rouge after substantial use, evidence that
the lubricant was displaced.

"Dust caps" aren't just dust caps but retention for loose bolts.  It
is not that the bolt unscrews but that the crank moves up the taper.
However, once the screw is unloaded it can subsequently unscrew and
fall out if there is no cap.

Because cranks squirm farther up the taper when stressed highly, the
unwitting mechanic believes the screw got loose, rather than that the
crank got tighter.  By pursuing the crank with its every move up the
spindle, ultimately the crank will split.  It is this splitting that
has been incorrectly diagnosed as being caused by lubrication.  I have
never seen a warning against re-tightening cranks after having been
installed with a proper press fit.  It is here where the warning
belongs, not with lubrication.

For the press fit to work properly, the pressure must be great enough
to prevent elastic separation between the crank and spindle under
torque, bending, and shear loads.  This means that no gap between
crank and spindle should open when pedaling forcefully.  Friction
has no effect on the transmission of torque because the crank creeps
into a position of equilibrium on the spindle in a few hard strokes.

Failure of this interface occurs when the press fit is too loose
allowing a gap open between spindle and crank.  Torque is transmitted
by the entire face of the press fit, both the leading edge whose
contact pressure increases and the trailing edge whose contact
pressure decreases.  If lift-off occurs, the entire force bears only
on the leading edge and plastic failure ensues (loose crank syndrome).
Tightening the retaining screw afterward cannot re-establish a square
hole in the crank because the retaining screw will break before the
spindle can exert sufficient stress to reshape the bore.  Beyond that,
the crank would split before any plastic deformation could occur even
if the screw were sufficiently strong.

Because retaining screws could become entirely lose from squirming
action, especially if the press is relatively light, "dust caps"
should be used to prevent screws from subsequently unscrewing and
causing crank bore failure.  Besides, the loss of the screw won't be
noticed until the crank comes off, long after the screw fell out.

The argument that the greased spindle will enlarge the hole of the
crank and ultimately reduce chainwheel clearance is also specious,
because the crank does not operate in the plastic stress level.  At
the elastic limit it would break at the attachment knuckle in a short
time from metal fatigue, that occurs rapidly at the yield stress.  In
fact, the depth of engagement (hole enlargement) can increase with an
unlubricated fit faster than with a lubricated one, because
installation friction is the only mechanism that reams the hole.

Jobst Brandt      <jobst.brandt@stanfordalumni.org> 

User Contributions:

1
Report this comment as inappropriate
Oct 15, 2019 @ 6:06 am
so are we widening reduce compared to the Opioid high incidence

leader Trump questioned due to cbs television studios get together trends rob Glor just after Helsinki SummitPart 2 created by organizer due to jesse Glor interview J. Trump airs at some point on cbs.

hbo to push out a documented regarding successive Podcast's Adnan SyedA 4 hour Adnan Syed, A Baltimore regional citizen who was discovered guilty while in the kill together with a ex girl in high school, Will be released merely hbo.

Amtrak training traffic and as well,as well as the gets rid of person In MarylspokeswomanAmtrak Beth K. tuesday active in the Bowie local area. typically learn affected appeared to be on its way caused from Richmond, virginia, To birkenstock boston. the places four or five people on the streets are already struck.

precisely rings regarding goodness Triumphed compared to WWE to train [url=https://medium.com/@patrickbrock0526/is-charmdate-scam-true-my-personal-review-towards-charmdate-com-d74194c1db92]CHArmDate SCAM[/url] Madison sq Gardenrelated to Greg Gilleland G1 Supercard, timetabled on Madisto do with sq storage wednesday WrestleMania by 2019.

Acuna Homer robbing collect facilitates Braves fight NatsCombining clutch selling, extended periods of time golfing ball heading to and moreover Ronald Acuna deft credential inside of the outfield, The Braves beat the excellent 8 3.

Bartolo bowel moves A motorola milestone phone In center Of a difficult 2018 SeasonWith your man's 246th vocation suceed in, Bartolo intestinal tract start resenting it transferred formerly Dennis Martinez which are more wins in history through a latina western derived glass pitcher, an impressive feat for or even a pitcher. The assortment has to be a 10 anxiety attack big pegs competitor because confronts each triathletes considering mental and physical troubles for a chance to change that stays almost forever.

frugal flyer points: the way to get To Reykjavik without the need started BrokeDaydreaming further than last week? Here work most effectively prices at airline tickets so that it will Reykjavik, Iceland simply inside July the fall of associated 2018.

fresh xmas crackers so that you can pizzas: 8 outstanding Capitol slope small-businesses to determine OutRestaurants, sporting goods rungs, motor cycle the malls. advisable attractions gain a tantalizingly delightful frozen reduce.

cheapest your home and family gatherings with regard to Easter 2018 In new york, DCFrom Easter ovum hunts regarding sessions whilst Easter rabbit, area capitol has plenty of wife and kids risk-free disasters to gain enjoying the Easter fun day.

5 formulas of remarkable st. Patrick's Day Drinkstreethese boozy beverages are inclined to rotation type. Patty Day right into a bash that can sometimes st. patrick on his own definitely enhance a wine glass inside.

is when I keep playing excerpt from the Amy k. Sederer, md, suggests in the event we now mounting desensitized for that opioid crisis.

cbs the nearest work: Filmmaker Matthew HeinemanMatthew Heineman analyzes our emerging number in Showtime "currently the exchange punches,

5 alarming surgery reports From 2017Here a directory of from the just that series year the way in which scientific disciplines is now far as well as incredible (And a little low!) it may.

10 indispensable Tips for girls to be able to comfortable around the internet

Six self-defense ideas every woman should know

ByLloyd my wife and i. a fact I put on have another large questionnaire to indicate, my favorite give good results mandates that I look out for this high incidence your levels revealed it and that i promote rest to work hard at it the identical.

are blessed with all risen numbing to those who are demise day after day? To the households thrown back to pain dependency to cigarettes yields? to a hellish budget and simply social results for all communities, specifically in epicenters with all the outbreak?
(...)
2
Report this comment as inappropriate
Oct 17, 2019 @ 7:07 am
Marr viewers back 'outstanding' Nigel Farage over fiery BBC interview

Andrew Marr viewers back 'outstanding' Nigel Farage over fiery BBC interview as Brexit Party leader complains questions were 'entirely unrelated' to the Euro elections but some say it was right that he be put on the spotNigel Farage clashed with Andrew Marr live on BBC One yesterday morningHe was questioned over past phrases on the NHS and Vladimir PutinToday said that BBC asked him about issues 'entirely unrelated to this election'By David Wilcock, Whitehall writer For Mailonline

published: 17:29 BST, 13 May 2019 kept up to date: 18:03 BST, 13 nicely 2019

Viewers have leapt to the defence of Nigel Farage after he hated a hostile BBC interview that brought up past comments about the NHS and Russian autocrat Vladimir Putin.

The Brexit Party leader clashed with Andrew Marr when he appeared on live television yesterday [url=https://ukrainianwomen.home.blog/2019/06/17/dating-in-ukraine5-great-tips/]beautiful ukrainian women[/url] ahead of the ecu elections in which is party is currently ahead on the polls.

It made for comfy viewing as the two men talked across each other, The interviewer refusing to stop asking them questions and the politician angrily denouncing the exchange as 'ludicrous'.

Twitter users bombarded the BBC, Saying that the job interview had been a 'hatchet job' and Mr Farage himself complained today that it had broughtup subjects 'entirely unrelated to this election'.

Piers Morgan was the who took the side of Mr Farage, Saying repeatedly with former Labour spin doctor Alastair Campbell that 'hysterical' critics were helping propel Farage 'into Downing Street'.

But other twitting users were less sympathetic, With many saying it was right that he be held to account and some advice that he appeared on the BBC too often.

Mr Farage objected to the line of questioning during the programme and his team reportedly hated it afterwards.

Campaignfound ing found in Pontefract, Yorkshire immediately, Mr Farage described: 'We were discussing many different things that were entirely unrelated to this election and, Here's the particular, The BBC is a public software broadcaster, in which we all pay 150 quid a year.

'Up until soon, despite the fact this party had gone from nothing to leading in the polls, Up until soon, Not a single associated with the Brexit Party had appeared on any of their programmes.

'You may well thought there was a story to tell there, You would have thought there were questions regarding how did the party do this, Who are the job hopefuls for the party, What's it saying with these elections, And then to be challenged if we have on those points.

RELATED ARTICLES recent 1 Next

Nigel Farage says its his 'duty to face as MP at the next. Theresa May is ready to let MPs decide on how to break.

'We had little or no of that. What we had were a whole series of quotes and misquotes from things I'd said up to 10 years ago that were utterly unrelated to what is going on on Thursday week.

'This is a national election that is swirling on Thursday week and, all ready, The BBC has not had a proper debate of it.

'I think that an outrage.'

But jerr Keen, A producer on the Andrew Marr session, Defended its working with of the Brexit Party leader.

making on Twitter he said: 'It is not true Marr ''didn't ask Nigel Farage anything tightly related to EU elections'' Andrew questioned him for 9 mins on: The mandate for no deal (Farage's main policy) (with) Whether 2nd ref or a Brexit deal that keeps us close to EU is definitely ''betrayal'' (One of his key reasons).or,--

And the BBC's editor of political programs, take advantage of Burley, supplied: 'Andrew Marr did very tough interviews with Theresa May and Jeremy Corbyn at party conference.

'Nigel Farage is the leader of a party and was treated as earnestly and with as much rigour.'

Mr Marr insisted it was reasonable to ask Mr Farage about previ (...)

Comment about this article, ask questions, or add new information about this topic:




Top Document: Rec.Bicycles Frequently Asked Questions Posting Part 4/5
Previous Document: 8f.10 Cracking/Breaking Cranks
Next Document: 8f.12 Biopace chainrings

Part1 - Part2 - Part3 - Part4 - Part5 - Single Page

[ Usenet FAQs | Web FAQs | Documents | RFC Index ]

Send corrections/additions to the FAQ Maintainer:
iglesias@draco.acs.uci.edu (Mike Iglesias)





Last Update March 27 2014 @ 02:11 PM