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Cottered Crank Spindle has Rounded Flat?
When I got my frame back from the painter's, I put the components, including the bottom bracket and crank back on. Same b.b., cotter pins and crank. Now, every time my pedal stroke reachers the 12 o clock position on the n.d.s., the crank arm slips forward about 7mm. I have experience with cotters, and use a nice Bikesmith press, but I have not found the cure for this.
I've tried filing the pin more, putting it in farther, trying new cotters, https://cimg4.ibsrv.net/gimg/bikefor...1734011eb1.jpg etc. Interestingly, when the pin is just resting in the hole, against the flat, the crank arm has no play. It's only after I use the press that I get this play. I am trying, now, to determine if it is the spindle that is the problem, so am including some photos, in case one of you can tell me if the leading edge of the n.d.s of the spindle is rounded enough to cause this sort of play. It does appear slightly mis-shapen. https://cimg5.ibsrv.net/gimg/bikefor...74a03ddf32.jpg |
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do not see anything amiss in images normally symptoms such as you describe are due to poor fitment or poor matching appreciate you know what you are doing are wedgebolts new or used? if new, what sort of marks can you see on the flats when you disassemble? how much head is showing following fitment? beast appears British so would assume 9.5mm cotter --- my guess - if cotters correct and well matched seating them with greater pressure will likely eliminate the symptom ----- |
Perhaps try both cotters inserted from the other side of the crank arm?
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Make sure that the cotter pins are not all the way through the crank arm. Usually, they should go all the way through without sticking out. I always check this carefully and add ensurence with a washer that has a slightly larger hole diameter that the outside diameter of the pin.
When I press the cotter into place, I snug both crank arms slightly and then look to ensure that they are parallel to one another. If satisfied, I start the super snug up process... Snug up the cotter with the press a lot then give it three taps or hits with a steel hammer, forcing the pin further into its fit. Now, snug up the press a wee bit (it will most likely turn easily at first) and tap again. Snug the press, tighten the press and tap again. I continue to do this until I get no more turn when I go to re-snug the press. When hitting the press head, do not be shy. Give it a decent three smacks with a steel hammer. You would be wise to support the crank assemble to prevent the impact from damaging bottom bracket bearings, and/or races. This is my home made press. The head on the screw has mushroomed even more that it appears in this picture... https://cimg0.ibsrv.net/gimg/bikefor...7ee6393045.jpg It is a slow process but does work well when done correctly. Now, make sure the round of the cotter is not sticking past the crank arm fit. If no, install the cotter pin nut and washer. If yes, install a washer with a hole larger than the cotter round, once again ensuring the the round does not stick out. Finally go for a ride but stick close to home. After the ride, remove the cotter nut and use the press again to ensure that the cotter has not slipped or worked its way into a better fit. I know this sounds silly but this final check is important. If the press does turn, go through the snug and tap procedure again. Now you know my secret about installing cottered cranks... https://cimg5.ibsrv.net/gimg/bikefor...0b109ca348.jpg |
BITD, especially during the height of the Bike Boom Fad, many makers, especially the French (Gitane in particular) were using cotters that were Wayyyy to soft. They easily distorted and worked loose. It was difficult to find hardened after market cotters. We used to get some from Zeus that were strong and through hardened but expensive. We reserved them for better quality bikes that had cottered cranks.
I was a forceful masher back in the early 70's and had to replace the cotters on my 1972 Gitane Gran Sport almost monthly because the crank arms worked loose. Those soft cotters were one of the impetuses for the adoption of cheap cast aluminum (melt forged euphemism) cotterless cranks that became De rigueur on decent lower priced bikes by 1975... There was nothing wrong with quality cottered cranks with good cotters. But hey, looks were everything and that's what sold bikes! randyjawa those forged steel Stronglight cranks with alloy chainrings pictured above were handsome! :thumb: verktyg :50: |
Originally Posted by verktyg
(Post 22190191)
BITD, especially during the height of the Bike Boom Fad, many makers, especially the French (Gitane in particular) were using cotters that were Wayyyy to soft. They easily distorted and worked loose. It was difficult to find hardened after market cotters. We used to get some from Zeus that were strong and through hardened but expensive. We reserved them for better quality bikes that had cottered cranks.
I was a forceful masher back in the early 70's and had to replace the cotters on my 1972 Gitane Gran Sport almost monthly because the crank arms worked loose. Those soft cotters were one of the impetuses for the adoption of cheap cast aluminum (melt forged euphemism) cotterless cranks that became De rigueur on decent lower priced bikes by 1975... There was nothing wrong with quality cottered cranks with good cotters. But hey, looks were everything and that's what sold bikes! randyjawa those forged steel Stronglight cranks with alloy chainrings pictured above were handsome! :thumb: verktyg :50: https://cimg2.ibsrv.net/gimg/bikefor...140b3c74e2.jpg Bought this take off (basically NOS) Legnano set complete with bottom bracket off of Ebay for a hundred bucks plus shipping. Swapped the Leggy rings and spider for Simplex and alloy rings... https://cimg9.ibsrv.net/gimg/bikefor...657e1e1c6d.jpg https://cimg6.ibsrv.net/gimg/bikefor...7575d4243f.jpg Nothing too special about the set on my Torpado and, because I forgot the snug and tap thing, they came loose on my test ride. Limped the bike home, fixed the problem and been cotter spinning ever since. I really like my entry level Torpado! Perhaps my favorite bike in my little stable these days... https://cimg8.ibsrv.net/gimg/bikefor...caaa2236d6.jpg |
More Cottered Cranks
randyjawa my 1965 Swiss made Tigra has DURAX SPECIAL COURSE forged steel cranks with Simplex chainrings and a Campy cottered BB.
https://cimg8.ibsrv.net/gimg/bikefor...c6c9bd80a2.jpg https://cimg0.ibsrv.net/gimg/bikefor...e46b2c4d57.jpg A few years back a LBS had this 1959 Paramount on consignment. It had these beautiful Stronglight cranks. Would have popped for it but the bike was too big for me. https://cimg8.ibsrv.net/gimg/bikefor...8978ac2360.jpg A 1961 Paramount at the same shop... https://cimg9.ibsrv.net/gimg/bikefor...1efe68d50e.jpg verktyg :50: |
Hi Juvela.
The pins are new, but I tried to install them a couple of times, cranking them down as tightly as I normally do. I'm sending a photo of the flats on the pins, and we can see, here, that there is a transverse slot that has been cut (by the spindle flat edge?) When I press these new pins down, I see about 8mm of the top showing. Yes, British, so 9.5mm. https://cimg1.ibsrv.net/gimg/bikefor...59f9885324.jpg |
Thank you, Randy.
I am going to go through this process as soon as I hear back from Juvela and get his estimation of the markings on my cotter pins. It looks like I might have some filing to do, first. |
Verkytyg,
I had been using the same cotter pin set for about 5 years, and was fine until I dis-assembled the bike for painting and then re-assembled. |
VAR 371 Cotter Vise
VAR 371 Cotter Vise for holding cotter pins while filing them to fit. Used them BITD when cotters didn't fit in the cranks properly. Also, the holes in cheap cranks sometimes got distorted.
https://cimg1.ibsrv.net/gimg/bikefor...f3b307a706.jpg verktyg :50: |
Verkyg,
It is interesting that you mentioned "distorted mount holes" and "cheap cranks". I do not know if this is related to my cotter-pin woes, but the arm on this side in question is having a really tough time sliding onto the spindle. I can "get it on", but I have to twist and shout. A spare, identical arm, goes on with no effort. This is the crank I am using, a Raleigh-branded Nicklin: https://cimg9.ibsrv.net/gimg/bikefor...22ead3dc58.jpg |
Originally Posted by verktyg
(Post 22190191)
randyjawa those forged steel Stronglight cranks with alloy chainrings pictured above were handsome! :thumb:
verktyg :50: https://cimg3.ibsrv.net/gimg/bikefor...b93c8ea91e.jpg Agrati cranks with integral forged crank-and-spider. Aluminum Simplex rings, 58(!)-45.(I subsequently downsized to 49-45, which is more my style.) |
I found the issue today. It was actually the drive-side pin that was loose.., not the n.d.s. as suspected. I had looked at the end of the spindle to see if it was turning with the installed n.d.s. crank arm, and thought it was not, but, upon closer inspection, it was. Thank you for your helpful tips. They could help me in the future, if and when I encounter other cottered-crank situations. I would still like to know people's opinion on the lateral grooves on the new cotter pins. I'm sure there are threads on filing pin faces, so I'll look for one or two of those.
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