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resolved@ejstubbs I've ordered new cassette, chainring and chain - and the tools required to get at the Bosch chainring
Chain wear on e bikes with derailleur gears is always going to be high. If it's hub then should be less so.
Basically you can run 400w+ of human and e-power combined through transmission. Those with illegal e-bikes will shred components.
What model is it - not an Urban Arrow?
I don't believe it...
The additional parts I was waiting on arrived this morning. I've just made a start on disassembling the right-hand side of the crank/chainring assembly. I removed the crank securing bolt - check. I carefully wound the threaded coupler of nice new, used only once before, Park Tools CCP-44 crank puller into the threaded hole in the crank, taking care to make sure it wasn't cross-threaded - check. I started turning the spindle driver handle on the crank puller. It was, as expected, hard work to begin with but gradually got easier until - it PULLED OUT OF THE CRANK. Closer examination suggests that the threaded coupler of the CCP-44 seems to have stripped the thread out of the crank.
When I reassembled it after the last debacle I was very careful to tighten to the crank bolt to 60Nm as indicated. So I don't believe that the crank was over-tight on the splines. I'd also put a thin coating of grease on the mating faces to avoid the risk of them binding, as I'd seen recommended in http://www.naden.de/blog/bbvideo-bbpress-video-plugin -->
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I can only conclude either that this particular crank is actually made out of cheese, or I had somehow forcibly crossed the threads on a previous occasion - but I really don't think I did that - the crank came off without a problem the last time. I can't work out what else I might have done wrong, though.
So now I have to buy a new crank. But, more challenging, I have to find a way to get the stripped crank off. Anyone got any ideas?
How deeply did the crank extrator thread into the crank? Usually they go in about 1/4". Also, 60Nm seems a bit on the high side to me, but if that's what's specified then maybe the crank really is made of cheese.
[Edit: just spotted that it's ISIS and not square taper. 60Nm is about right. I think my FSA cranks are torqued a bit more than that.]
A 3-jaw puller might help remove the crank if you can finangle some sort of bearing plate to go behind the crank. The alternative is to ride the bike until the crank falls off; an alternative alternative is to put the blowtorch on the crank for a bit to heat it faster than the spindle. Sometimes just the expansion will break the bond at the interface, and sometimes it's the expansion you need to help drift the two apart.
@LaidBike: What model is it - not an Urban Arrow?
No, it's a Voodoo eMTB with a Bosch Performance CX motor.
@arellcat: Thanks for the suggestions. See below for "progress" of a sort:
A passing remark on another YouTube video has led me to discover the cause of all my woes. "Sometimes," said the YouTuber, "there's a washer under the head of the crank bolt." Washer? No-one said anything to me before about a <rule 2>ing washer.!
It turns out that this washer can sometimes get lodged at the bottom of the thread for the crank puller coupler. The catch is that the "pusher" at the end of the spindle on the crank extractor is fractionally too large to go through the washer. So, you wind back the spindle and screw the coupler in to the crank. It looks like it's in a good distance because the washer is only ~1mm thick. You then start screwing the spindle down. But what actually happens is that the spindle pusher ends up pushing against the washer at the bottom of the coupler thread, rather than against the crank axle, so instead of pushing the crank off the axle you end up pushing the extractor coupler out of the crank, hence stripping the thread.
I suppose if I'd been thinking about it a little bit more as I was doing it I would have clocked that the spindle wasn't far enough in to have engaged the end of the axle before I started to feel resistance. But it just never occurred to me that there might be an obstruction in there to beware of.
Further inspection has revealed that the crank bolt as supplied had the washer held in place by an o-ring that sits on the bolt thread. If the washer is at all tight at the bottom of the coupler thread then the o-ring just slips off the bolt and the washer gets left behind. Grr...
So that's another lesson learned that isn't in the book (at least, not the one I read): check that there's nothing that could prevent the extractor spindle from pushing on the end of the crank axle - and especially check that there isn't a washer stuck in there (literally stuck: I had to ping it out with a screwdriver). It's actually obvious if there's a washer in there if you know to look because it covers the ends of the slots in the splined face of the crank: you see a smooth surface rather a castellated ring.
But that does leave me pondering why only sometimes do manufacturers use a washer on the crank bolt? Apparently infrequently enough for it not to be mentioned as a matter of course in most instructional texts and videos. I did think that it might be because the crank bolts on my bike seems to need to be done up rather tight, so a washer would help prevent binding. But Arellcat thinks 60Nm is about right so it seems unlikely to be that (and anyway, isn't that what copper grease is for?) Without the washer the bolts sit slightly recessed in the cranks, but they torque up just fine so if it's just cosmetic then...well, what with one thing and another I think a second Grr... might not be unreasonable in the circumstances.
The bottom line is that this crank is basically toast, in that once it's off it's off for good. So my plan now is to source replacement cranks before attempting other approaches for removing the crank, and in the meantime run the old chain and cassette with the old chainring that I currently can't get off.
@Arellcat: Thanks again for the suggestions. I'm not sure there's enough real estate on the back side of the crank for a gear puller to get secure purchase (there's no spider or anything like that). Similarly, the blowtorch idea could be hampered by there being no ready access to the backside of the crank to get a drift in close enough to the centreline of the axle. Plus, I'd have concerns about hitting something firmly attached to a Bosch motor with a hammer. I don't actually have a blowtorch anyway, although I wondered if my heat gun might be sufficient. OTOH there's a risk that excessive heat might do nasty things to the motor...
Riding it until it falls off could be an option. Once the new crank arms turn up (now ordered, in silver rather than black 'coz cheaper - and shouldn't show so much evidence of crank/rock interface incidents!) I could just carry the new one with me and pop it on if the old one pings off mid-ride.
The other option I'm considering is careful but destructive surgery on the old crank. I've seen suggestions that a Dremel cutting disc can be used to slice a quadrant out of the splined ring. I'm not sure whether there's quite the clearance available to do that much cutting, but I'm thinking that multiple cuts followed up by a bit of levering with a big screwdriver could prise it open enough to come off. (Possibly with judicious application of the heat gun as well.)
I'd forgotten that my FSA cranks have thin washers under the heads of the crank bolts, but they usually come off with the bolts. But they are also thin enough that the force of an extractor would bend them. Shims rather than washers, perhaps.
A Dremel might do the trick, cutting away a portion of the splined region, but you want to avoid cutting into the splines of the spindle. What a faff!
Since thread is knackered, maybe a blind bearing puller to get the crank off?
@arellcat: I'd forgotten that my FSA cranks have thin washers under the heads of the crank bolts
I bought a pair of FSA self extracting crank bolts over the weekend. They have a shim between the bolt head and the screw-in "lid" that the bolt pushes against when you unscrew it, thus extracting the crank at the same time as undoing it. Magic.
They also have a washer under the bolt head, but it's a proper captive washer* that can't be left behind in the crank, rather than relying on a tiny o-ring to stop it slipping off the bolt (or not, as it turned out in my case).
If only the OEM cranks had been supplied with such useful fixings...
* I think these are also "magic" in the sense of: how are they made? They remind me of those love spoons with caged wooden balls that have to be painstakingly whittled out of solid wood by love-lorn Welsh swains.
New crank arms have arrived - and very shiny they are too. All I have to do now is get the old r/h one off.
Sadly, riding the bike with the r/h crank arm bolt removed doesn't seem to have done the trick (so far). I may try the heat gun/differential expansion approach next, though I'm not too optimistic.
I think a 4" gear puller would actually do the job. Although the backside of the crank arm doesn't at it stands provide a very good surface for the puller to grip on to, I'm 99% sure I can file/grind it down to a flatter surface. (The crank arm is toast anyway so I don't care about inflicting damage to it, though I don't want to damage the axle.) I think this is actually a much more promising idea than trying to cut open the crank arm's fluted ring with a dremel, given that a lot of the metal is surrounded by the chainring lock ring.
Just wondered if anyone had a 4" gear puller I might be able to borrow, before I go and splurge good money on a new one of my own? Suitable recompense e.g. beer could be arranged...
Today's update: I acquired a 4" gear puller yesterday. After much trial and error, struggle and strife - both with the motor in the frame, and with it removed - I eventually achieved...a broken gear puller. One of the 'hooks' that was engaged on the crank arm snapped off.
It's as if somehow this crank arm has become practically welded on to the axle. I have literally no idea why it is being such a <rule 2> to shift. I'm pretty sure that I know how I managed to strip the extractor thread (the errant washer as identified previously). That's nothing to do with this problem. Why the thing isn't shifting now I have no idea.
I think I've reached the end of my abilities with this and I'm going to have to seek professional help. I have a horrible feeling that it's going to end up having to be a new motor - which will be very costly - just because there's no way to get the crank arm off in order to fit a new chainring (the old chainring having also fallen victim to yesterday's struggle and strife).
Very unhappy
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:(
:(
If the crank is toast (or even if it isn't but may as well be if the chainring is), you might try cutting as much of it off as you can, Dremelling a slot and using a nut splitter. I'm not sure what else to suggest now!
I do have an extremely large* bench vice, if that is of any help.
* but also extremely heavy and extremely bolted down
Yikes I had missed this thread.
There's a couple of things to be tried;
1) Blowtorch as hot as you dare (I will drop mine off at yours) and then pour on ice water. Repeat. Thermal shock may break the weld.
2) Dremel a slot and split it with a hammer and cold chisel. (Assuming a nut splitter can't be fitted over the crank as I imagine...?)
You'll be there forever with a dremel. What part of Edinburgh are you in? I have a small angle grinder........
@Blueth
I think there's an angle grinder on the premises. Having done genchi genbutsu on this issue I believe it will be difficult to bring such a tool to bear on the crank without damaging the motor housing. Think dentistry rather than demolition.
I have a mains Dremel with a range of saws and also a diamond cutting disc. It is proffered.
Having looked at the video I don't think you'll need to risk going near the motor housing. The sprocket would protect it anyway. By the time you are part way through the crank it will probably have loosened its grip on the shaft. If not, the application of a chisel to open up the groove cut should release it.
Thanks folks for your continued advice and support. I realised as I was checking this thread on the way home from the Botanics on the bus that I do actually have a mains powered Dremel 'clone' (it's a Parkside tool which I think means I bought it from Lidl). Dug it out just now and it's 160W which I think sounds reasonably meaty. I also have some 2" diamond cut-off discs bought many years ago for another project which never happened. (Also gloves and eye protection!)
Question: would one cut be enough or might it be better to cut a narrow vee slot (a bit like felling a tree) before applying the cold chisel?
Job for tomorrow, anyway: too chilled after strolling around the Botanics to work up the necessary determination to take on another bout of hardcore bicycle surgery today...
One slot for maximum leverage. Cold chisel and bang.
Cannot wait to hear news of your success.
Sorry, another question: am I aiming to split the top of the crank open like a nut splitter would i.e. with the split parallel to the axis of rotation? If so then I need to have the pedal end of the crank against a solid object, yes? May be a little tricky with a few pounds of Bosch motor hanging off the axle...will see.
3lb hammer OK or too much?
Yes, the top end of the crank diametrically opposite the leg, ie where the crank is thinnest and most vulnerable.
I'd go for lots of blows with a light hammer, driving the chisel in towards the motor, perpendicular to the crank, with the opposite side of the splined shaft resting on a bit of wood.
Might actually be best using an old screwdriver to get the crack opened up initially...take your time.
Exciting!
@IWRTS: Have PMed you.
mains powered Dremel 'clone' (it's a Parkside tool which I think means I bought it from Lidl)
Some of them are surprisingly good. I bought a faux-Dremel from Makro years ago for £14. I can't even remember the brand It's a Fairline, and it is a shameful copy of the original black Dremel of 25 years ago, but in a rather strange terracotta red plastic. I've used it a lot!
Well, I eventually chickened out of inflicting any further injury to the crank, partly due to the risk of collateral damage to the axle and/or the motor itself. I dropped it in to Harts Cyclery this am and they succeeded, by dint of more butchery than I had the nerve to attempt, in removing the crank with no harm done to the axle or motor. Hurrah, and multiple kudos points to them. I had it back within the hour in exchange for a very reasonable fee (less than I paid for the gear puller which I ended up snapping*, in fact) and spent a happy afternoon rebuilding the bike and listening to the rain come down. The motor is now back on the bike, with the new chainring, and is definitely working in walk mode. The new cassette is on the back wheel and the new chain is transferring drive from the motor to the wheel. I didn't have time to put the new cranks on before dinner called but that should be a straightforward job for tomorrow. I have a tube of Park Tools' silver anti-seize which I may use sparingly on the mating faces of the axle and crank. Good idea? EDIT: Just checked Park Tools' web site, they say use anti-seize on the splines.
Lots of lessons to chalk up from this experience but at least I and my 'leccy steed will be back on the trails at last.
* Harts actually tried their own gear puller on it while I was in the shop, and backed off when it became clear that pulling wasn't going to shift it.
@ejstubbs
Good outcome. I hesitated to suggest further butchery. Everyone has their limits on this kind of stuff. Bear in mind that you had done most of the work for them.
Square taper bottom brackets are famously left bare as they are effectively an interference fit, but splined ones are not so anti-seize should be fine (I applied some to mine).
As a former electrochemist with an interest in pitting corrosion I would love to know how the crank and shaft got so intimate.
“
The bottom bracket spindle—it is a spindle and not an axle since it “spins” on the bearings
“
https://www.firstcomponents.com/square-taper-bottom-bracket
I have always called them axles and will continue to do so.
It's attached to a motor so it is also a drive shaft?
“so it is also a drive shaft?“
Mmm, but motor not there to (primarily) drive cranks.
So, who know!
I never thought about axles not spinning before but it's quite right, isn't it?
Would pushing the crank itself not count as a power source and therefore validate the use of driveshaft?
@acsimpson
Aye lad. That's reet smart. Drive shaft it shall be.
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