#81
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Bearing damage?
Tom Keats wrote:
In article , Tom Sherman writes: Tom Keats wrote: In article , A Muzi writes: The manufacturers of steel pinned cranks seem to feel a heavy cast steel press with 42:1 leverage driven forcefully ( an able man puts out about 80 pounds with both arms just below shoulder height) is a better approach. That is a humongous amount of pressure. Here are two clever designs, a VAR #7 crank press and a set of S+S couplers: http://www.yellowjersey.org/photosfromthepast/VAR07.JPG When these cranks were still common, even new premium quality Sugino cranks on Sugino spindles would fail in a day or two of riding when the assembler neglected to remove, lubricate and press the pins properly. For forcing barrel-chested or wrongly-sized cotter pins into straight-tapered holes, I'm not surprised. But cotter pins are not barrel-chested. I actually have a few in my stock -- I've slid dial calipers down them, and there's no widening in their middles. Straight taper pins; straight taper holes. As it should be, as long as there's a perfect fit with no slop. Although one might get a small amount of pin/spindle contact by drawing up the nut, the forces at that contact will work it free and deform the pin's surface in short order if the pin moves at all. We don't (didn't?) want a "small" amount of pin/spindle[/crank] contact. We want (wanted?) ~full~, tight contact all along the length of the pin. That calls for proper fitting, not cheap-assed swage-fitting where the pin is fat in one localized spot, and loose (or loosening) everywhere else. And the only reason to "lubricate" cotter pins (w/ appropriate grease) is to be able to easily pop them out in order to service the BB. They don't fail from inadequate greasing. Might bend the threaded section when driving them out, but that goes with the territory. And there's an acquirable "touch" for avoiding that. Well, it's mostly luck. If I had a bike with cotter cranks that needed servicing, I would take it to the shop with proper tools, such as Mr. Muzi's. A cotter pin that does NOT require significant force to insert will NOT form a press fit, Okay. You want an oversized something forced into a weakened hole, thereby further weakening it. What an American approach. American, as in western hemisphere? That includes Vancouver, does it not? which is what this interface requires to function as intended. The interface requires proper fitting of crank, spindle and cotter pin. And yet you want everything to depend on some fat guy/thing. How typical. Well, if that's what you want, knock yerself out. Shove barrel-chested pins into your cranks, spread your metal apart, and see what happens. The above is not an accurate discription, as it implies shoving in a grossly oversized cotter by brute force, which is NOT the practice recomended by either Jobst or Andrew. -- Tom Sherman - 42.435731,-83.985007 LOCAL CACTUS EATS CYCLIST - datakoll |
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#82
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Bearing damage?
On Sun, 28 Dec 2008 00:11:24 -0800, Tom Keats wrote:
In article , Tom Sherman writes: Tom Keats wrote: In article , A Muzi writes: The manufacturers of steel pinned cranks seem to feel a heavy cast steel press with 42:1 leverage driven forcefully ( an able man puts out about 80 pounds with both arms just below shoulder height) is a better approach. That is a humongous amount of pressure. Here are two clever designs, a VAR #7 crank press and a set of S+S couplers: http://www.yellowjersey.org/photosfromthepast/VAR07.JPG When these cranks were still common, even new premium quality Sugino cranks on Sugino spindles would fail in a day or two of riding when the assembler neglected to remove, lubricate and press the pins properly. For forcing barrel-chested or wrongly-sized cotter pins into straight-tapered holes, I'm not surprised. But cotter pins are not barrel-chested. I actually have a few in my stock -- I've slid dial calipers down them, and there's no widening in their middles. Straight taper pins; straight taper holes. As it should be, as long as there's a perfect fit with no slop. Although one might get a small amount of pin/spindle contact by drawing up the nut, the forces at that contact will work it free and deform the pin's surface in short order if the pin moves at all. We don't (didn't?) want a "small" amount of pin/spindle[/crank] contact. We want (wanted?) ~full~, tight contact all along the length of the pin. That calls for proper fitting, not cheap-assed swage-fitting where the pin is fat in one localized spot, and loose (or loosening) everywhere else. And the only reason to "lubricate" cotter pins (w/ appropriate grease) is to be able to easily pop them out in order to service the BB. They don't fail from inadequate greasing. Might bend the threaded section when driving them out, but that goes with the territory. And there's an acquirable "touch" for avoiding that. Well, it's mostly luck. If I had a bike with cotter cranks that needed servicing, I would take it to the shop with proper tools, such as Mr. Muzi's. A cotter pin that does NOT require significant force to insert will NOT form a press fit, Okay. You want an oversized something forced into a weakened hole, thereby further weakening it. What an American approach. which is what this interface requires to function as intended. The interface requires proper fitting of crank, spindle and cotter pin. And yet you want everything to depend on some fat guy/thing. How typical. what? don't you guys breed "get a bigger hammer" engineers over there? Well, if that's what you want, knock yerself out. Shove barrel-chested pins into your cranks, spread your metal apart, and see what happens. cheers, Tom |
#84
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Bearing damage?
On Sun, 28 Dec 2008 01:33:32 -0600, Tom Sherman wrote:
"jim beam" wrote: On Sat, 27 Dec 2008 22:21:16 -0600, Tom Sherman wrote: "jim beam" wrote: On Sat, 27 Dec 2008 22:02:08 -0600, Tom Sherman wrote: "jim beam" wrote: On Sat, 27 Dec 2008 21:55:04 -0600, Tom Sherman wrote: "jim beam" wrote: On Sun, 28 Dec 2008 03:29:26 +0000, jobst.brandt wrote: [...] The way you say that, I become ever more certain that you have no experience with high quality racing bicycle cotters, the mainstream when I began bicycling over longer distances. cotters were fundamentally misconceived. your defense of them is bizarre given your favorite hobby-horse of pedal thread fretting, yet apparently you're oblivious to the same effects in this application. [...] Where did Jobst defend cotter cranks as being a good design? I missed that. Please provide a citation. serious social perception issue there tom! discuss that with your medical professional. So "jim beam" apparently can not provide a citation. more perception problems! or your newsreader doesn't allow you to follow a thread. So "jim beam" apparently can not provide a citation. Enough said. mea culpa - i can't be bothered to do your rudimentary google searching for you. Obviously, when Jobst took up serious cycling (late 1940's or early 1950's?), there were no quality alternatives to cottered cranks. From Jobst's postings, it appears he abandoned cottered cranks shortly after quality square taper cranks became available. as did we all. stupid design. So "jim beam" criticizes Jobst for using the best commercially available design at the time? Sheesh! no, i'm criticizing defense of cotter pin use - jobst's position that they're ok if "driven home hard enough". they're /never/ ok. No "jim", Jobst was writing in the context of what was best if cotters were being used. Of course, your personal hatred of Jobst blinds you to reason when reading his posts. don't read closely enough - do you. Translation - I do not read with an anti-Jobst agenda. YAWN it's not anti-jobst, it's anti made-up bull**** - that's where you're making your huge mistake. i'll dish it out to /anyone/ that pollutes the knowledge pool with misinformation and underinformed guesswork. just like we saw with nate, it's the lies and bullying that keep people with real information away. and that's just plain WRONG. |
#85
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Bearing damage?
On Sun, 28 Dec 2008 02:45:46 -0600, Tom Sherman wrote:
Tom Keats wrote: In article , Tom Sherman writes: Press fits are designed to have things crammed together with high force and deformation of the parts involved. Would you ride a square taper crank that you could push onto the spindle by hand? That's a way different matter from swaging, and you know it! Press fitting a cotter is not swaging in primary intent either. you don't have experience of cotter pins then - they come out deformed. |
#86
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Bearing damage?
Tom Keats wrote:
The way /you/ say it, you can't even get cotter pins in without a fancy hydraulic press and a bunch of fussy alignment. That's true, but as I mentioned, the press fit is preload on the spindle, just as one needs preload on a square taper aluminum crank. This is not because the cotter doesn't fit, but because it needs high preload to no fret in use. No, it needs to /fit/. No fit, no value, no proper function. That's all. As I mentioned, the cotters I used were a close fit into the pedal cotter bore that intersects the spindle bore. Cotters could be pushed through the hole and out the other side on a crank held in hand although it took a bit of manual force due to chrome plating roughness on the cotter, (they not being cosmetically polished as cranks). Oi, bloody hell! Please, not the Q-factor thing again! How does how convexly tapered pegs in squarely tapered holes fit, do with crank spacing anyways? Cotters are cylindrical and have a sloping face toward the spindle. You are imagining this assembly incorrectly. Things should properly fit with each other, and not be barbarically thrust or forced into each other in hopes of achieving something that isn't cheap, ugly or wrong. What do you mean by "barbarically thrust or forced into each other in hopes of achieving something that isn't cheap, ugly or wrong"? As I said, this makes me sure that you never installed such cranks or you wouldn't say such off-the-wall things about the process. Cotters must be pressed into place with great force by a press or impact. It was done successfully for more than a half century for all the finest professional racing bicycles, and of course all general purpose bicycles with three piece cranks. As I've stated in a previous up-thread post, I've enjoyed the benefits of Japanese bicycle engineering. I don't get it. What does tis have to do with cottered cranks? Much of it is pretty good. You'll need to be more specific to make clear what engineering features you think are Japanese. It certainly wasn't the square taper BB or derailleurs. Nothing is safe from me. That's a suspicious phrase. What are you getting at? Jobst Brandt |
#87
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Bearing damage?
Tom Keats wrote:
If I had a bike with cotter cranks that needed servicing, I would take it to the shop with proper tools, such as Mr. Muzi's. A cotter pin that does NOT require significant force to insert will NOT form a press fit, OK. You want an oversized something forced into a weakened hole, thereby further weakening it. What an American approach. which is what this interface requires to function as intended. The interface requires proper fitting of crank, spindle and cotter pin. And yet you want everything to depend on some fat guy/thing. How typical. Well, if that's what you want, knock yerself out. Shove barrel-chested pins into your cranks, spread your metal apart, and see what happens. That settles it for me. You have no idea what cottered cranks are and how thy work. Not only that, but you show a lack of understanding of force transmitting mechanical interfaces, yet you choose to others who do, how it should be done in the vaguest of terms. Jobst Brandt |
#88
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Bearing damage?
Tom Keats wrote:
In article , (Tom Keats) writes: In article , A Muzi writes: The manufacturers of steel pinned cranks seem to feel a heavy cast steel press with 42:1 leverage driven forcefully ( an able man puts out about 80 pounds with both arms just below shoulder height) is a better approach. That is a humongous amount of pressure. Here are two clever designs, a VAR #7 crank press and a set of S+S couplers: http://www.yellowjersey.org/photosfromthepast/VAR07.JPG When these cranks were still common, even new premium quality Sugino cranks on Sugino spindles would fail in a day or two of riding when the assembler neglected to remove, lubricate and press the pins properly. For forcing barrel-chested or wrongly-sized cotter pins into straight-tapered holes, I'm not surprised. But cotter pins are not barrel-chested. I actually have a few in my stock -- I've slid dial calipers down them, and there's no widening in their middles. Straight taper pins; straight taper holes. As it should be, as long as there's a perfect fit with no slop. Although one might get a small amount of pin/spindle contact by drawing up the nut, the forces at that contact will work it free and deform the pin's surface in short order if the pin moves at all. We don't (didn't?) want a "small" amount of pin/spindle[/crank] contact. We want (wanted?) ~full~, tight contact all along the length of the pin. That calls for proper fitting, not cheap-assed swage-fitting where the pin is fat in one localized spot, and loose (or loosening) everywhere else. And the only reason to "lubricate" cotter pins (w/ appropriate grease) is to be able to easily pop them out in order to service the BB. They don't fail from inadequate greasing. Might bend the threaded section when driving them out, but that goes with the territory. And there's an acquirable "touch" for avoiding that. Well, it's mostly luck. It just occurred to me: most of my bikes have been Japanese imports, or Japanese/Canadian collaberations (especially Apollo and Sekine.) I'm a Vancouverian canadian, and we've had our own localized bicycle trade. So maybe our bicycle design experiences differ from that. If cotter pins were to be barrel-chested, it seems to me they should be made of a softer & more pliable metal than hard steel, that would spread like butter under pressure, the better to fill in the gaps, while still retaining enough interface. But to anyone else reading this: don't let your LBS flog-off unto you the wrong cotter pins. It's not like that on our planet. Wedge pins ("cotter pins" in bicycle jargon) are steel cylinders with an angled cut which rides against the spindle flat. Peugeot's proprietary pin has an offset thread to allow a larger flat. I've never seen a non-cylindrical pin. Not-tight wedge pins readily move under pedal torque and develop a 'notch' at the spindle edge. Dry pins cannot be forced as tight, with the appropriate press, as lubricated pins. -- Andrew Muzi www.yellowjersey.org/ Open every day since 1 April, 1971 ** Posted from http://www.teranews.com ** |
#89
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Bearing damage?
Tom Keats wrote:
If I had a bike with cotter cranks that needed servicing, I would take it to the shop with proper tools, such as Mr. Muzi's. A cotter pin that does NOT require significant force to insert will NOT form a press fit, OK. You want an oversized something forced into a weakened hole, thereby further weakening it. What an American approach. which is what this interface requires to function as intended. The interface requires proper fitting of crank, spindle and cotter pin. And yet you want everything to depend on some fat guy/thing. How typical. Well, if that's what you want, knock yerself out. Shove barrel-chested pins into your cranks, spread your metal apart, and see what happens. That settles it for me. You have no idea what cottered cranks are and how thy work. Not only that, but you show a lack of understanding of force transmitting mechanical interfaces, yet you choose to tell others who do, how it should be done in the vaguest of terms. Jobst Brandt |
#90
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Bearing damage?
On Sun, 28 Dec 2008 18:51:47 +0000, jobst.brandt wrote:
Tom Keats wrote: If I had a bike with cotter cranks that needed servicing, I would take it to the shop with proper tools, such as Mr. Muzi's. A cotter pin that does NOT require significant force to insert will NOT form a press fit, OK. You want an oversized something forced into a weakened hole, thereby further weakening it. What an American approach. which is what this interface requires to function as intended. The interface requires proper fitting of crank, spindle and cotter pin. And yet you want everything to depend on some fat guy/thing. How typical. Well, if that's what you want, knock yerself out. Shove barrel-chested pins into your cranks, spread your metal apart, and see what happens. That settles it for me. You have no idea what cottered cranks are and how thy work. that's clearly not true. Not only that, but you show a lack of understanding of force transmitting mechanical interfaces, yet you choose to others who do, how it should be done in the vaguest of terms. so, great and mighty jobst brandt the expert engineer, how do you reconcile pedal spindle thread fretting with cotter pin [supposed] non- fretting??? by your logic, all you'd need to do is over-tighten the pedal into the crank arm so it wedges hard enough. because that's what you're asking us to take on faith for cotter pins - which were notorious for getting chewed. |
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