Square taper, grease or not!!!!
- Thread starter dicoverybmw
- Start date
Good pointJohn":is6olkr5 said:
I for one apologise for losing it a bit there
Lets just agree to disagree.If you all wish to not grease your tapers then that is fine.
But.....
http://www.youtube.com/watch?v=AQNHHhwbBHM
RadNomad
Senior Retro Guru
Charlieboy28":1thlnmdg said:RadNomad":1thlnmdg said:
YES IT IS
Clearance fit
It is a fit that always enables a clearance between the hole and shaft in the coupling. The lower limit size of the hole is greater or at least equal to the upper limit size of the shaft. WRONG
Transition fit
It is a fit where (depending on the actual sizes of the hole and shaft) both clearance and interference may occur in the coupling. Tolerance zones of the hole and shaft partly or completely interfere. WRONG
Interference fit
It is a fit always ensuring some interference between the hole and shaft in the coupling. The upper limit size of the hole is smaller or at least equal to the lower limit size of the shaft. RIGHT
AND IF YOU WERE RIGHT YOU WOULDNT NEED CRANK PULLERS , oops soz caps, or grease for that matter
You are correct in your definition of the three classes of "fit", but in engineering terms that reference relates to holes and (parallel) shafts. It will be apparent that on a tapered shaft, any one or all three of these classes could be argued depending on where one chooses to take the measurement. A tapered shaft provides a method of transmitting torque by the friction provided by the close tolerances of the male and female cones, if the axial thrust is sufficient (such as in a Morse taper drill shank) the friction generated by the taper alone is sufficient to transmit the required torque. Where the application of sufficient axial thrust can not be guaranteed a drawbar (or bolt) will be required to provide constant axial loading and in high torque applications, keys, tangs, or splines may be necessary to prevent slip occurring. The big advantage of using the taper is that it is easily dismantled and assembled repeatedly, such as in the cycle crank application, where the taper is used to "take up" the necessary clearance between crank and spindle and held in engagement by the bolt, while the square of the taper provides positioning location and works with the taper in applying the high and varying working torque likely to be generated. The conventional "Interference Fit" is not employed where repeated and easy dismantling is a requirement (the application of heat or hydraulic force may be required) and any textbook of workshop engineering will corroborate this statement because where this is a requirement one of the other two classes of fit will be specified. While your explanation of the high and low limits of the Hole and shaft is correct this would normally be supported by an example of the practical application of each and it is this that rules out the concept of a taper being an "Interference Fit". A cycle crank assembly is without any doubt whatsoever a clearance class fit.
retrobate":2hmgnb2q said:
Radomad, please call skf & explain the error of their ways? You're normally the voice of reason & sense, so I'd like to know your explanation for their error?
I really can't grasp why the grease camp think it's all over when the majority of manufacturers are on the dry list.
For me I'll say that I've moved from NO to AS & a very specific variety at that, not copper & not lubricating grease.
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Taper Shaft or Bushing
A common method of introducing an interference is to manufacture a tapered shaft and tapered bore. At installation, axial force is applied (by tightening a nut against a thread on the taper shaft's end) to advance the hub along the tapered shaft
Furthermore, you'll need a method for removing the part later.
sounds like a a square taper crank to me and it is an interference fit as it achieves the interference fit by the crank arm being driven up the tapered shaft and there is some degree of deformation of the aluminium: xmas-big-grin: :xmas-big-grin: :xmas-big-grin:
and i'm not an engineer im just always right
and i dont care what the non grease gestapo have to say
A common method of introducing an interference is to manufacture a tapered shaft and tapered bore. At installation, axial force is applied (by tightening a nut against a thread on the taper shaft's end) to advance the hub along the tapered shaft
Furthermore, you'll need a method for removing the part later.
sounds like a a square taper crank to me and it is an interference fit as it achieves the interference fit by the crank arm being driven up the tapered shaft and there is some degree of deformation of the aluminium: xmas-big-grin: :xmas-big-grin: :xmas-big-grin:
and i'm not an engineer im just always right
and i dont care what the non grease gestapo have to say
velomaniac
MacRetro Rider
Did a basic bike maintenance course years ago and the mechanic tutor said do not repeat do not grease a tapered bottom bracket axle. You could overtighten a greased component causing damage and making removal much harder.
Plus Mikee's a pretty good engineering bod and i respect his knowledge.
Plus Mikee's a pretty good engineering bod and i respect his knowledge.
gtRTSdh":10dacfty said:
There's a few more additions to the list:
No Grease
FSA http://www.fullspeedahead.com/storage/i ... 319_v3.pdf
Grease
Phil Wood http://www.philwood.com/support/faqs.php
Rene Herse http://janheine.wordpress.com/category/ ... se-cranks/
Some comments / opinions:
- Shimano altered there position what seems to be from the mid-90s / late-90s. Perhaps to be simply opposite to Campagnolo or after doing their own uncommunicated R&D as to why. Who knows?
- It seems some manufactures offer there own magic, perhaps because they make a complete chainset with their own set of tolerances to achieve an optimal fit and only want consumers to buy the whole lot.
- Race Face gave a very complete reasoning, putting other manufactures to shame really.
- I "heard" that Middleburn were meant to be used with Royce BITD, which would perhaps explain they are in the same camp.
- I suspect there is a certain amount of manufactures simply copying the position of another manufacturer, leaving us the consumer with a 16 page thread to get to the bottom of it :roll:
What winds me up the most with the "No Grease" camp is the generic spiel of "it can damage and deform the crank if pushed on too far" like this bod http://www.youtube.com/watch?v=4XhcLErjHn0
When are we going to see some measurements of the apocalyptic "too far" point expressed in mm or a % of taper length for a specific - or typical - crank and BB combination? It's a known engineering fact that some "deformation" of the crank is required for it to sit properly so clearly there is a "sweet spot" range not properly communicated by pretty much all manufactures.
When I hear this "too far and could damage" argument it echos someone saying "ooooh....you could strip that bolt thread if you tighten the nut too much". Yes, sure you are right if I was a hamfisted pleb / brute with no feel for materials. I could strip a thread with or without lube too. It's just an utter nonsense stand point.
Carry on...
velomaniac":6bphs7ms said:
This mechanic tutor you had velo must be the exception to the rule because the tutor that deals with the bike station staff and mechanics INSISTS on the torque wrench being used.He is fully accredited in velotech and cytech.
I fully agree that if you grease it it will make it easier the force on further and further till the slot is damaged beyond repair.
That however is not the point here
I an arguing here that the correct use of torque means that you stop turning the bloody spanner when the correct torque is reached and not forcing it on beyond that point.Correct torque and threadlock will prevent the bolt from undoing.
This goes for any bolt
Take the bolts on these lock on grips, having only to rely on the tightness of the bolt to stop it undoing and all of a sudden the grip flies off and you take the tumble ?
What was wrong? the bolt wasnt tight enough or the understanding that without threadlock the bolt will inevitably undo through the shock of off road cycling. This same understanding must also apply to crank bolts. If you dont threadlock the bolt in it can and will work loose and the part that is being held on will loosen off also.
Im hardly going to keep forcing these small bolts tighter and tighter in some vain hope that they wont work loose :?
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