Supprise on way to work! wheres my pedal!, Now Rebuilt

[Ricky_nz]

Just after crossing a road as I crossed the bridge at the edge of the road back onto the bike path I heard a clunk and had to adjust my balance in a hurry!

View attachment 1


This is on my early 300W V2 elation kit.
These cranks always seemed to flex a bit so I guess some form of metal fatigue.
I had a previous one replaced due to it starting to bend in the area where this crank broke..
Not sure what I'll do now as I don't think we have a dealer in NZ any more.
I am tempted to go to a longer bottom bracket and use the parts from sick bikes as their cranks although of similar construction are straight rather than having a bend in the middle of them. I really need to finish my HXT powered bike but that takes time.
For a kit only used on the road / bike paths to get to / from work approx 5Km / week day total it suggests a weak part / poor design they should not bend in the first place.

Until I fix it its back to a GM hub :-( don't get enough exercise on that in my short commute and that bike has poor brakes although that swap from lead to lipo helped it..

I've just about had it with this expensive kit!
things that went wrong since I brought the kit:
LIFP04 dead just out of warantee 2 cells dead (now ruinning on 7S lipo!)
crank arm bent
freewheel failure
Crank arm break
:x :-(
on the plus side the motor mount bracket is still solidly on the bike and the motor / electronics are still good.

I did learn from this kit that I definitely prefer the non-hub solution.

.

 

[Miles]

Glad you're ok, Ricky - crank failure can be dangerous....

I would forget these cheapos and get some decent trials cranks.

 

[sk8norcal]

hey Miles,
why do trials bike use freewheel cranks?

are all these cheaper freewheel cranks meant for motorized kits?

 

[spinningmagnets]

why do trials bike use freewheel cranks?

If you remove the freewheel from the rear wheel, the cog in back can be much smaller. Once you have a smaller cog in back, you can keep the same gear ratio with a smaller chainring, which gives the bike better ground clearance when crawling over logs and boulders.

Edit: A while back I found these BMX rear hubs with the freewheel alongside the cog, to allow a tiny 9T cog with the freewheel still in back.

 

[Miles]

It also takes weight off of the back wheel.

I'm not sure what the cheapo cranks are made for. I don't think they'd last long in trials riding, though

The ones in your pic look much stronger than Ricky's ones.

 

[Ricky_nz]

Glad you're ok, Ricky - crank failure can be dangerous....

I would forget these cheapos and get some decent trials cranks.

Thanks Miles, I start looking for some good trials cranks.
Anyone got any recommendation for a new strong trials crank assuming I change the bottom bracket etc to clear the motor?
I will have to use some front sprockets other than the elation ones though as they need a nasty bend in the cranks, I already have the good sick bike parts freewheel so just need a couple of sprockets..
I seem to remember some mention on this forum of echo. I will do a search later when I get time.
Most really wide bottom brackets I've seen are square so I guess that limits the choice of cranks a bit.

Yep kind of glad it happened when it did at probably <20Kph and just off the road and while I wasn't putting too much power into the pedals.
The bikes inertia kept it stable and I was pretty much in the seat at the time so luckly held it together before coming to a stop then returning for the pedal.
I can think of situations where it could be far more dangerous though so definitely want to avoid it happening again.

 

[Miles]

I'm using the Echo forged cranks.

Plenty of choice here: http://www.tartybikes.co.uk/search.php?category_id=514 It might be a bit expensive to buy there from Australia, though...

NB Tarty bikes give the offset dimension for many of the cranks, which is useful...

 

[sk8norcal]

Ricky, got a pic of the original crank?
why does it need a bend...?

this wouldn't work?
http://www.sickbikeparts.com/catalog/product_info.php?cPath=21&products_id=35&osCsid=lvfvkrsof720slu09umva0t5p4

 

[Miles]

I already have the good sick bike parts freewheel so just need a couple of sprockets..

See here, with regard to use of that: http://www.endless-sphere.com/forums/viewtopic.php?f=28&t=21248

 

[Ricky_nz]

Ricky, got a pic of the original crank?
why does it need a bend...?

this wouldn't work?
http://www.sickbikeparts.com/catalog/product_info.php?cPath=21&products_id=35&osCsid=lvfvkrsof720slu09umva0t5p4

I do have a set of those ones arround somewhere I was going to use for a project (got themn when I got the freewheel).
They are similar to the one that broke just without the bend s may be stronger but I kind of like the idea of somthing stronger if I can get it.

Heres a few pics. one of the left side showing the bend around the motor and then two if the right side that broke.





Thanks Miles for the link to the message on the SBP freewheel usage. I'll have a look to see if I can get the chain aligned right since I don't want to put too much effort on this bike. I imagine that being 300W I shouldn't have the same issues as the hight power systems though.

 

[Ricky_nz]

HI All,

Parts are in

Just got new echo cranks and bits to rebuild the bike after the broken crank.
I'm re-gearing it for slightly higher speed as I can't pedal fast enough to help the motor at top speed. Because the land is flat where I live I won't miss the other 2 sprockets on the elation spider. I never shifted it out of top anyway.
I've got Friday off work to work on my own projects since the weekend is always too short.

Here is a few photos comparing the sick bike parts cheap cranks and the echo cranks. Both are thicker at their thinnest point than the elation ones that failed. ( Looks like they use something different now).
The Echo cranks feel more solid to hold and look better machined.
I will be using the echo cranks on the rebuild. The sick bike parts ones I brought a while ago will be left on the shelf for something else, still usable but I prefer solid and reliable for my commuter bike.
I think I should be able to keep the forces on the bearing in the freewheel under control by lineing things up well but only time will tell.
I have been running a sick bike parts freewheel with the elation sprockets for a while now and with that the loads are definitely well away from the freewheel bearing most the time I guess its surviving because of the low power of the system, 300W..

 

[Ricky_nz]

Hi All,
I've just got back from a short ride round the block after swapping out the parts and aligning the chain.

I now have one sprocket either side of the SBP freewheel (small spacer for the outside one to allow the 2 chains to clear comfortably) with echo cranks. currently 2 * 44Tooth.
I may go for a smaller sprocket for the side driven by the motor as it is now slightly lower geared than it was with the stock elation spider (42? haven't counted)
One bonus is I think the 44 makes the pedal assist easier by lowering the crank revs slightly so maybe its is good to keep it this way.

I had wanted to put a 48 Tooth to drive the main bike chain but unfortunately without messing up the chain line with an very wide bottom bracket I couldn't make it clear the frame and being an aluminium frame I don't think its wise to try and crush it slightly to make clearance wouldn't need much (few mm but I think too risky).

It feels much better pedalling with the echo cranks, rock solid rather than flexie stock cranks that ultimately failed.
The slightly narrower space between the pedals is also more comfortable still a little wider than a stock bike though.

Unless you have steep hills to contend with I would recommend this change if you own an older v2 elation and like to pedal.

Has anyone got any recommendation on sprocket setup for good performance from the elation 300W or maybe 200W kits? Until today I had always used the spider in the way it was configured stock but have heard others had swapped sprockets around.

One other thing I will be keeping an eye on is where the motor mounts onto the frame. I had to move this forward to get the now motor chain to the right tension and this is the first time I had removed it since I put it on the bike. There is a few marks in the frame and dings where the mount originally sat. I had only tightened it enough to hold in conjunction with the torque stay. It slipped once so it got an extra turn on the nuts and it had been that way since. I guess placing something between the motor mount and the frame might help but on my frame the chain clamp things were too short.
There is a couple of lengthways in the frame tube and a few diggs and at the corners of the formed frame where the chain in the clamps tried to dig in.

I have mounted it back the same way after moving it but won't be using this frame for anything too strenuous but will keep a close eye on it but its been this way for a couple of years.

Now I need to do something about the stupid slow stepped start throttle! learnt a few tricks to make it go to full quicker but not ideal and I think this throttle is just plain hazardous in traffic.

 

[Ricky_nz]

Just got round to getting my turnigy keychain camera working so here is a video of a short test ride.
The bike doesn't really sound that bad though, probably that the camera is taped directly onto the stem..
The video was quite choppy on the original microsd card. This is off a different 4G card I had lying around that seems to work better..
[youtube]Zuy9LZKp964[/youtube]