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crank arm and sprocket help
Hello all, I need help with a problem I have encountered. I'm putting back together a delivery bike, the sprocket is loose on the crank arm, the little stub that sticks out seems to be too big???. It looks to be for a thicker sprocket, which leads me to believe maybe it's not correct for this bike. THE serial number says it's a 1949, the sprocket has a dish too it. It looks nothing like My other bikes of the same era.
Here are a couple of photos
That hole is too big and there for has play making it loose.
I would be prepared to dissemble the bottom bracket remove the crank and tighten up the sprocket retaining nut of the crank arm side.
gt
Hello my Friend,not sure why you have a dished sprocket for this resto,it must be off another multi gear shifter style CCM.Is the sprocket thickness the issue?The only dished sprockets I have are nos Firebird 5 speed units which are very similiar in diameter as your 49 but not thickness.Looks like you might need a replacement.You have the technology.Good to see you at the T.O show which was a great success,saw lots of folks new and old,even my new friend Toast yes thats his name let me ride around on his nice and rusty Sunshine framed creation c/w fixed drive ,disc front brake carbon forks and all kinds of other little add ons of other trashed parts,it actually rode quite well with some caution.Now finish that Delivery Bike as it could become center fold material for the upcoming Vintage CCM calender if you play your cards right.Let me know Thx Jamie
The correct drivetrain for a delivery bicycleof that era is 3/16" wide. While this is an old standard that was largely phased out very early in the century but CCM continued to use it into the 1950s on their delivery and track racing models. The extra width allows them to carry higher loads and wear slower than a 1/8" system. 3/16" is still used on moderm BMX bicycles, so obtaining replacement chains is not an issue. I haven't specifcally looked at a delivery bicycle chainring for dish, but the track racing chainrings are dished.
The nub on ther back of the crankarm prevenets rotational play of the chainring while the retention nut prevents lateral play. I can't tell via the photo if the nub is engaging the chainring or not. You say the nub is too big, so I assume it's not engaging. The simple solution is to drill the nub mating hole one size larger.
I'm trying to attach another photo which really gives a good indication of what the problem is. Iam having technical difficulties. It's the circular hole on the sprocket that the nub on the crank arm goes into, which locks it from having play. The hole is too big which is causing it to not seal up tight even when I tighten it down. I don't think there is a solution other than replacing with a different sprocket which has a smaller hole, or finding another crank set and trying. frustrated!!
IHey Simon when you have a few vintage ccm bicycles this is common problem as the drive brake pin on the crank arm tends to wear over many years. I have fixed many, all you have to do is have the pin built up and machined to snug fit the sprocket. As we speak I actually have to fix the one on my '56 CCM built Zenith. If the welding shop machine shop use a tig welder you won't heat the metal enough to ruin the chrome on the crank. Like I said I have fixed a few.
Or you could wrap an appropriate thickness of shim stock around the nub/pin to build it up to the required diameter.
T-mar I find that when you shim it that it works its way off the drive pin as I have tryed that in the past. Just saying from my experience
While I only have one bicycle with a one piece crankset and have not had to resort to this fix on it, I have had no complaints regarding the few shim repairs I've done for customers. However, it does not work for a severely worn pin and you need to use the correct shim stock. I've seen many people try to use scrap metal, such as pop cans, for shim stock. Aluminum is far too soft and displaces easily in most applications. I prefer feeler gauge stock, which is typically stainless steel or high carbon steel. You have the added advantage of being able to buy it in a wide range and thickness and therefore obtain a very good fit. You can buy 12 inch feeler gauges at most industrial supply houses. It's been a while since I bought one, but I believe it was only about $2.00. If you're having issues with the shim working its way out, you could try one of the various metal adhesives to hold it in place.