Nexus 7 on vertical dropout Help!
 

I just convert my bike wit an SG-7C18, but I have a big problem IMO. The chain is too tensioned and I need a clue what to do...

Actualy my bike have vertical dropout like in the photo http://sheldonbrown.com/images/dropf-vert.gif

Now, I believe there are 3 variants: to add a pair of links and a chain tensioner, to add 4mm spacers between dropouts and axle (that's enough to relax the chain a bit), and the bad idea :twitchy: to enlarging holes with a drill ... not so fun and too much risky. ??? Need other clues or any other opinions. thanks

the bike is this: http://www.krone-radschlag.de/images..._milano_gt.jpg

I really don't understand the underlined bit. Adding - or rather restacking spacers would shift the wheel sideways and change the chainline. And you set the chain line to run straight as a separate task from chain tension. No good can come from tweaking the chain line to change the chain tension.
One option is to use a half-link, and to file the dropout a little bit wider forwards at the top. With a half-link, you don't need much to get the requred adjustability.
But what crank do you have? On the pic it might well be more than one ring on it.
And you don't need to buy a chain tensioner - you already have one. Put your derailer back on, use a short length of wire to lock it to the right position and you're done. If you have a double or a triple crank, then you'd still be able to use all rings up front.

well... the truth is that I kept old crank with 3 gears and the chain is between the firs gear and the nexus spoke. BTW i didn't know about the half link but I'm afraid that even with it will be too large. http://bikeforums.net/attachment.php...hmentid=352635 here I explain the idea with the spacer. thanks

the correct fix is some sort of chain tensioner
and an old derailleur will work perfectly for this

anything else you do is just a kludge

the other problem i see
is that you seem to have the wrong anti rotation washers
there are anti rotation washers made specifically for vertical dropouts
and then the cable will not have the tight bend in it as it leaves the hub

3rd post link: Add a half link to the chain, 1/8" and 3/32" width is available it offers a smaller chain length adjustment..

and , if too long.. say a whole link, or 2, then you can always add a chain tensioner ,
it screws in where the derailleur was ..

I have a Rohloff Hub and it's chain tensioner , it works very nicely.. twin pulley with a stiff return spring.

single pulley ones are also made .. more rigidly takes up excess slack ..

and you can look for a different chainring, 1 tooth one way or the other , makes a difference.

Likewise 1 tooth on the hub cog.

a well aligned single speed chain-line does not have to be super tight..

another thought

if you put the claw of the anti rotation washer above the axle instead of below it
it will act as a spacer like you are looknig for
although any type of spacer there will limit the space against which the nut is tightened

If that is the coaster brake version of the Nexus 7 (Shimano specs say it is), then you won't be able to use it with a spring-loaded tensioner or rear derailleur. If it fits now but is too tight, add a half link.

i have a shimano alfine chain tensioner
it is the same type and works great

good call

Thanks again for the answers to all of you
I'll gonna try with half link, and if is still too large I'll DIY a fixed (no spring) tensioner like in this image http://i179.photobucket.com/albums/w...e/IMG_3088.jpg. I believe that the tensioner with spring will affect the coaster brake... not so sure, just a simple believe. If not afect the brake, I'll use the "old" derailleur tensioner. For the antirotation washer, I have to buy one dedicated for my vertical dropout.

So, I just tought ok that I need a fixed tensioner... before see your message :)

If its a coaster brake , chain tensioners will flex under back pedal breaking . er Braking.

any chain tensioner will negatively affect the function of the brake
or snap in half the first few times you use it
you need a rigid straight run of chain on top and bottom

+ NB: a retrofit BB eccentric is available now. for some BB types.

didn't know about it... thanks allot for help

It will work like you said but i have to filing a bit. Anyway good idea.

It will work like you said but i have to filing a bit. Anyway good idea.

I'm still not sure that I get it. Chain tension should be set either by chain length or moving the rear wheel(or possibly the crank) length wise, not moving the wheel sideways.
And which chain ring are you using, the biggest or the smallest?
Either is unlikely to offer a good chain line for an IGH conversion. The most common approach is to flip the big ring over to the inside of the carrier for a better chain line.

judging from the picture
and the angle of the top and bottom of the chain
i would guess he is using the small ring

the op however
did not ask about proper chainline
or about useful gear ratios
so i said nothing
but i suspect he will acheive neither

Wilfred, I find the problem... and can be a big problem. I rotate the hub with about 90 angle and now it just ok and the chain tension is also well. I.m afraid the hub axle is a bit crooked. Also when move the pedals, on a point the chain is relaxed an on the opposite point 180 degree is tensioned. ??? What do you think? BTW, i bought an SH hub, and i still have another 3. I like gears systems, epicyclic trains and somethimes i use to change the disks on my Trooper 4L30E AT :) and I find them (hubs) cheap. The one I use is almost new and I payd for it less than 50$. In Romania people are afraid of complicated systems and I benefit because of this. I've seen same bike with nexus from factory made... so I guess that this type of bike is provided to have a hub without any adjustments.

I just post a new repply to Wilfred and you... the problem seems to be much tricky.

I use the smallest chain ring and the chain line seems to be alright. Where I live is a hilly area, I don't need speed, but rather force. I'm a beginner in bikes, not with too much training... after about 17 years of break. I got first 1st place on bike skill on my school many years ago :p. Until next spring, because now is snowy in my area, i plan to convert it on front electric hub... just for climbing help (about 1km/0,6mile daily) using a small battery.

a Spring loaded 2 pulley chain tensioner would let you run 2 chainrings and a front derailleur.

and a path not taken was the SRAM DualDrive, a 3 speed IGH with a cassette driver on the right end.

that offers a granny gear without needing the triple crankset.

i installed a nexus 7, with coaster brake, on a custom framed bike with vertical rear dropouts.

here's what i did:

i decided on a rear sprocket and chainring combo whose ratio i could live with. i bought a half-link. when installed, the chain was too tight to fit all the way into the rear dropout, so i filed it (the dropout) a little. voila!

BTW, IIRC, my Nexus7 coaster brake hub did not have any special washer on the back, probably because it had a whopping brake arm attached to the offside chainstay, IDK. it was a good setup, a little too heavy in the rear, but IMO that's a matter of personal preference...