Square taper, grease or not!!!!

[retrobate]

Do what the manufacture recommends!

eg. Campagnolo recommend a dry taper interface and a dry bolt thread. Raceface recommend lubrication.

I can see the point of both arguments.

Grease (anti sieze compound, a specific loctite type compound or JC4) to reduce the chance of corrosion between different metals (very good point and one that I go by on non tapered interfaces).

But my interpretation of engineering practices is that (as a generalisation) a square taper (with no manufacture information) is nothing like a splined or keyed shaft and should not be greased as this could lead to the crank moving too far up the taper thus increasing the stress on the corners of the female square taper leading to possible cracking in the future.

Even if you installed the campy cranks on a dry taper but greased the bolt and then used a calibrated torque wrench at the correct setting you will still have over torqued the bolt (because of the grease reducing the friction) and put more stress on the taper than the designers intended. Again do what the manufacture recommends!

Conversely if you installed the raceface cranks dry with a with a torque wrench the crank will not be seated on the taper far enough with the risk of play developing.

To all the other aircraft engineers. Would you grease a componant when installing it if the AMM said it should be installed dry? And I have to admit that I dont recall any square tapers on any of the aircraft that I have worked on so I have no specialist knowledge regarding square tapers on aircraft.

Personally I dont grease

 

[kingoffootball]

I think what's clear is that it's not whether you grease the taper or not that's important, but that you are convinced that your way is right to the point of being willing to argue your point

 

[gdb2b]

Wow. There is a bit of passionate "religion" in this thread. Who'd of thought? Especially for BB taper cranks of all things. At the risk of unintentionally fanning the flames of the discussion, several additional comments if I may?

Do what works for you/you are comfortable with, particularly heeding the manufacturer's instructions. There is no one right way (except in the case of long term assembly without the benefit of AS).

Despite the commentary/religion expressed herein, it isn't that big a deal either way, especially if you service your kit frequently enough such that corrosion isn't a factor.

The only time that it what you do is a factor is if the cranks are going to be on for a long time (multiple years).

Does AS cause/allow the crank to be more deeply seated? Possibly. However I have never measured same. AS coumpound and grease ARE different and have very different properties. Grease absolutelly will allow the taper to seat more deeply at the same torque. Is that a big deal? I don't know (but probably not, especially at the torque settings for this gear).

AS is a viscous, space filling, friction compound. The concept is counterintuitive, as cyanoacrylic ester (LocTite) actually adds several microns to the crank taper's dimension causing it to reach it binding contact point sooner in the taper bore.

AS coumpound is highly recommend/damn near required for successful automotive use/applications (rod bolts for instance). You do not EVER assemble the bottom end of an engine block without exacting use of AS. The torque requirements are considerably more stringent/exacting than those of square taper BBs. Over-torque a rod bolt and the result is instant bearing failure (and several thousand spent in engine repairs).

AS coumpond, used properly, has two engineered functions. First, to fill in minute spaces between the mated surfaces, harden, and thereby inhibit movement and the subsequent loosening of the mated parts. Second, inhibit corrosion.

Grease has a completely different purpose. It is explicitly engineered to provide lubrication to allow movement under load. It is subsequently chemically treated with corrosion inhibiters. Is movement really what is desired for these parts?

Alternative solution? Use Teflon tape. Addresses the AS corrosion issue without the possibility of overinsertion, and eliminates squeakly cranks.

Queue next preacher/sermon...

 

[shogun]

All this torque talk then, lets see some manufacturer torque specs for common 90s cranksets then?

 

[RadNomad]

....why others in here has to back up their arguments by stating long experience in the airline industry....??....well it only seems to be one agenda behind such rhetorics; and that is to discourage others, less educated, from providing a rational explanation based on their own practical experience. :?

Wow.. some very ungracious comments on here! I don't believe anybody is trying to "discourage others" nor is this an "argument", it's just a light hearted discussion among people with common interest. Why be so vitriolic? Those who cited their considerable and/or relevent competence in whatever industry are doing so because explaining the source of their knowledge is actually a universally accepted way of demonstrating the quality of the input (Wikipedia articles are a good example of information backed by sources). Those people are trying to be helpful in solving - or at least contributing - to the discussion. There is nothing wrong with so-called "less educated" (as the above quote puts it) opinions based on practical experience, nothing wrong at all, in fact practical experience positively augments the base knowledge.
It is unwise, foolish even, to attempt belittling those who are well versed on a topic by calling their input "rhetoric". Pretty much all of these posts are well intended and many have technical merit, but there are also quite a lot of misinformations being written (for example someone stated these square tapers are an interference fit whereas in fact they are a clearance fit. Someone else described gavlanic reaction as physics whereas it's actually chemistry).
Everyone is entitled to an opinion and there is nothing wrong with "backing up" one's statement.
Bigotry on the other hand is (in my opinion FWIW) counterproductive.

By the way always remember.... It takes a crank to start a revolution!

 

[Tazio]

eg. Campagnolo recommend a dry taper interface and a dry bolt thread. Raceface recommend lubrication.

That sentence sums it up for me.

Nobody really has a "correct" answer.

 

[We_are_Stevo]

....why others in here has to back up their arguments by stating long experience in the airline industry....??....well it only seems to be one agenda behind such rhetorics; and that is to discourage others, less educated, from providing a rational explanation based on their own practical experience. :?

Wow.. some very ungracious comments on here! I don't believe anybody is trying to "discourage others" nor is this an "argument", it's just a light hearted discussion among people with common interest. Why be so vitriolic? Those who cited their considerable and/or relevent competence in whatever industry are doing so because explaining the source of their knowledge is actually a universally accepted way of demonstrating the quality of the input (Wikipedia articles are a good example of information backed by sources). Those people are trying to be helpful in solving - or at least contributing - to the discussion. There is nothing wrong with so-called "less educated" (as the above quote puts it) opinions based on practical experience, nothing wrong at all, in fact practical experience positively augments the base knowledge.
It is unwise, foolish even, to attempt belittling those who are well versed on a topic by calling their input "rhetoric". Pretty much all of these posts are well intended and many have technical merit, but there are also quite a lot of misinformations being written (for example someone stated these square tapers are an interference fit whereas in fact they are a clearance fit. Someone else described gavlanic reaction as physics whereas it's actually chemistry).
Everyone is entitled to an opinion and there is nothing wrong with "backing up" one's statement.
Bigotry on the other hand is (in my opinion FWIW) counterproductive.

By the way always remember.... It takes a crank to start a revolution!

Cool reply...

Another quote worth remembering; 'There are none so deaf as those that don't want to hear'

 

[mkaavin]

....why others in here has to back up their arguments by stating long experience in the airline industry....??....well it only seems to be one agenda behind such rhetorics; and that is to discourage others, less educated, from providing a rational explanation based on their own practical experience. :?

Wow.. some very ungracious comments on here! I don't believe anybody is trying to "discourage others" nor is this an "argument", it's just a light hearted discussion among people with common interest. Why be so vitriolic? Those who cited their considerable and/or relevent competence in whatever industry are doing so because explaining the source of their knowledge is actually a universally accepted way of demonstrating the quality of the input (Wikipedia articles are a good example of information backed by sources). Those people are trying to be helpful in solving - or at least contributing - to the discussion. There is nothing wrong with so-called "less educated" (as the above quote puts it) opinions based on practical experience, nothing wrong at all, in fact practical experience positively augments the base knowledge.
It is unwise, foolish even, to attempt belittling those who are well versed on a topic by calling their input "rhetoric". Pretty much all of these posts are well intended and many have technical merit, but there are also quite a lot of misinformations being written (for example someone stated these square tapers are an interference fit whereas in fact they are a clearance fit. Someone else described gavlanic reaction as physics whereas it's actually chemistry).
Everyone is entitled to an opinion and there is nothing wrong with "backing up" one's statement.
Bigotry on the other hand is (in my opinion FWIW) counterproductive.

By the way always remember.... It takes a crank to start a revolution!

Do you really believe that my comment was ungracious? .....and I'm even guilty of bigotry as well?

As usual, discussions like this one turns into a polemic discussion where, as I carefully pointed out, rhetorics becomes more important than the actual subject of the discussion. It becomes a matter of "winning" rather than finding the correct answer. It may of course be that this was not your intention at all, but you were not the only one mentioning such experience.

But still looking at your post, my point is simply that spending most of a post pointing to long experience in another technical field isn't very relevant to such a simple discussion. Some technical experience might of course be relevant across fields of experience but I do believe that the wear a bicycle crank will be exposed to from human force, is in no way directly transferable to any condition technical parts in an airplane will be exposed to.

Especially viewed from my own (probably limited and uneducated ) experience were the absence of any grease never has posed a problem.

 

[RadNomad]

Yes, and yes. And who is the one trying to "win"?

 

[unkleGsif]

Jeez.......

Grease up like a Roman, or stay dry like a Nun... its up to the individual

THE END