Customizing rear sprockets for a Cyclone - advice?

[bluehead]

Hi,

I'm now the proud owner of a new Trek Navigator bike with my old Cyclone 500W motor on it. I'm wondering how to deal with a problem in the gearing.
There's an 8-speed megarange cassette on the back wheel, but the angle of the chain is way off in the bottom 4 gears. This gives a practical gear range of just 11-16. I'm wondering if it would be possible to rearrange the order of the sprockets from

11, 12, 14, 16, 18, 21, 26, 32

to

11, 14, 18, 26, 32, 21, 12

in order to get a usable range of 11-26 for regular use, with the 32T available for when I want a low gear and don't mind an awkward chain angle. The 21T and 12T would not be used.

Has anyone ever tried this? Should I expect it to be possible to rearrange the sprockets like this and for the gears to work, or would the derailleur be unable to shift? Or is this way off topic for an electric bike forum?

Daniel

 

[flyinmonkie]

Not off topic.

Most of the megarange set ups I've seen are a freewheel and not a cassette. The difference being when you remove a freewheel, all the sprockets and spacers will stay together in one unit. A cassette when removed all the sprockets and spacers will come off individually. You can tell by looking at the face of the front sprocket. If there is a large hole almost the size of the inside of the sprockets and it is threaded on the inside, it is a freewheel. If there is a disc with little teeth pointing in, then it is a cassette.

If it is a cassette, you can put the sprockets in any order you want on the hub. You will need a special tool from the bike shop called a cassette removal tool. The big thing is to keep the spacing the same between the sprockets so the derailleur doesn't miss a sprocket when shifting. You can also limit to derailleur from using the either or both ends of sprocket set up.

You can remove sprockets from a freewheel, but it is harder and requires 2 chain whips.

FM

 

[bluehead]

Thanks for your help, it sounds like this is worth trying. No bike store in town has the tools needed, so I've ordered them and should get them next week.

 

[boostjuice]

The teeth profile of Shimano Hyperglide/SRAM equivelant sprockets are designed to only engage the 'next-one-up' tooth count sprocket. I dont think it will shift cleanly any more...
If you look closely at the cluster, you will see a spiral shape in the rotationaly offset ramp guides. If you miss out a sprocket then the formation will be altered and it will shift like an old 5/6spd where the cluster will require a full revolution before the kinked chain follows through and you get complete chain wrap. Bad for shifting under load....

 

[Miles]

Marchisio sprockets and spacers are available individually, for those that want to build their own custom cassettes.

 

[flyinmonkie]

Wow, almost every bike shop I have been in has had a cassette tool and a chain whip for sale. At least they can order them.

boostjuice is right about the shifting, but if you are just taking the 2 smallest sprockets and putting them on the back side of the cassette it will still shift fine as long as you don't get to those 2 from the largest sprocket. You can either set the stop on the derailleur to not use those 2 sprockets, or get the bike shop to do it. They may look at you funny, but just tell them what you want done. You could also take those 2 sprockets off all together and use single speed spacers in place of them.

FM

 

[bluehead]

The teeth profile of Shimano Hyperglide/SRAM equivelant sprockets are designed to only engage the 'next-one-up' tooth count sprocket. I dont think it will shift cleanly any more...

This is one of the things I wasn't sure about. Since with the Cyclone it is necessary to stop the motor and shift with pedals anyway (or so I am told, and that's what I always do), shifting is already disruptive and this might not make much of a difference. The gear replacement operation will be reversible, so it's worth a try. I saw there was a lot of information about Hyperglide shifting at http://www.sheldonbrown.com/k7.html.

Wow, almost every bike shop I have been in has had a cassette tool and a chain whip for sale. At least they can order them.

You'd have thought so. Two shops said they didn't have a lockring tool but could order it and the third said they "don't sell that, it's a tool." There's an internet store with self pickup near my office that does claim to have it in stock, so I ordered from there and can pick it up next week.

In the meantime, I got to ride the new bike. Sure is fast compared with the old one; it gets up past 40kph without even trying even though it has the same 500W motor. When I get the new LiFePO4 battery that's on order I'll really be able to test its limits.

Daniel

 

[boostjuice]

Yes that SheldonBrown webpage explains it well. Particularly this part;

" To provide the Hyperglide functionality, each sprocket must be designed with regard to the adjacent sprockets. For instance, there are 3 different 15 tooth sprockets for 7-speed systems: one version works between a 13 and a 17; another works between a 14 and a 17; another works between a 14 and a 16.

Hyperglide cassettes are commonly sold as a unit, and are designated by a letter which refers to a particular set. There are dozens of different cassette combinations available. Most 7- and 8-speed cassettes are designated by a one- or two-letter code"

So you cant just remove odd/even sprockets in the cassette cluster and have it shift like beforehand. The ramps wont line up.

Rather than the hassle of modifying your rear cassette, i would look at changing the offset of the rear cluster driving chainwheel on your freewheel cranks. This assumes your using either a 2 piece freewheel crank system (Typically bundled with the larger 1000watt motors), or one of the 3 piece chainwheel setups that Cyclone added to their product lineup only this year (As an option with the planetary gearbox style motors). With these, the motor driving a different chainwheel to the one that drives the rear cluster means you can modify the relative offset/spacing between the two. You might need longer M5 bolts and spacer standoffs or even a $#!Tload of washers stacked up, but as long as you have frame clearance, there is no reason to not be able to get your chainline straight with the centre sprocket in your rear cassette, and gain use of all the gears in the cluster.

If you have the single chainwheel freewheel cranks then i would suggest purchasing a solid filled BMX 44T chainwheel and boring out the centre and drilling 5 x M5 holes to couple it next to your existing chainring in an offset spacing. Without access to a lathe, you could use a holesaw and a file to bore the centre out. The good news is you have the current chainwheel as a template to mark these holes out so it wont be reliant on your measuring accuracy. For more on this process see here>> http://www.endless-sphere.com/forums/viewtopic.php?f=6&t=1757&start=45 This would be cheaper than purchasing a whole new 2/3 piece freewheel crank system from Cyclone of which the majority of the cost would be the ridiculous postage rate.

pictures say a thousand words;

A chainwheel like this 44T BMX one has a solid fill to allow you to match the cyclone freewheel crank flange profile. As it is designed for 1/8" BMX chain, you would have to use this one for the motor coupled chainring and your existing narrower chainwheel for your narrower multispeed chain that drives the rear cluster.

PS: If you currently have a single chainwheel drive and need to convert to a dual chain system, you would also have to change the motor rotation direction from CCW >CW

 

[bluehead]

If you have the single chainwheel freewheel cranks then i would suggest purchasing a solid filled BMX 44T chainwheel and boring out the centre and drilling 5 x M5 holes to couple it next to your existing chainring in an offset spacing. Without access to a lathe, you could use a holesaw and a file to bore the centre out.

Clever!

 

[kfong]

I have the 650watt version, single front sprocket setup and can do all gears in back. You just need to get the motor positioned better. My build is posted.

 

[pakobike]

Hi,
I too found the same problem when mounting my Cyclone, but playing with spacers to get the chain to work with 9 speed 11 - 34, I added a modified derailleur chain to prevent the output from the inside.



Best regards

 

[dumbass]

I didn't have this problem but my setup may solve your problem. I run a 360w with a Nuvinci hub. No shifting sprockets so no more problem. Of course with the Nuvinci hub my bike gained 4 pounds. But I was running twin 18ah SLA packs at 56 pounds. So I traded up to a single 20ah lipo4 pack at just 13 pounds. End result was a 39 pound weight lose and twice the range. Oh yeah, still no chain shifting and a much better gear range to select from. And you wouldn't believe how smooth and quiet it is when shifting.

 

[bluehead]

I didn't have this problem but my setup may solve your problem. I run a 360w with a Nuvinci hub. No shifting sprockets so no more problem. Of course with the Nuvinci hub my bike gained 4 pounds. But I was running twin 18ah SLA packs at 56 pounds. So I traded up to a single 20ah lipo4 pack at just 13 pounds. End result was a 39 pound weight lose and twice the range. Oh yeah, still no chain shifting and a much better gear range to select from. And you wouldn't believe how smooth and quiet it is when shifting.

I thought of this but I wasn't sure about the extra weight or the durability of one of these hubs.

In the meantime I've been riding for a couple of weeks on the new bike, although not so much as I usually do. The main thing I've noticed is that when I'm in low gear I'm not using the motor much - either I'm using a low gear because I'm around pedestrians and riding slowly, or I'm just getting started before I immediately change up. There are no steep hills in my area. So I don't need to put the chain under a lot of stress in low gear. It seems to be managing fairly well. I have had the chain come off a couple of times when descending kerbs in low gear, and a hub gear would probably fix that. I have a similar setup to pakobike which keeps the chain on in normal use, at the cost of some added friction.

The bike store FINALLY has the lockring tool I ordered, but I am not sure I am going to use it. I appreciate the way these gears shift so easily and I'd miss that if I went back to what it was like shifting on my old bike.

 

[flyinmonkie]

Bluehead,

You could remove a couple of the lower gears, or big rings to move the rest over and put spacers to take up the space. You would keep your nice smooth shifting, but you would loose the lowest gears. They may be too low for the motor to use anyway.

FM

 

[bluehead]

I finally did this and it works great. I removed the 16T and moved the 12T over to the left of the cassette to use as a spacer. Then I adjusted the L screw on the derailleur to stop the the chain from shifting onto the 12T. I had to play with the indexing adjuster a little to get the shifting, but it worked well on this morning's ride.