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dropping a chain with a single ring(16 posts)

dropping a chain with a single ringpatricksc
Nov 24, 2003 4:57 PM
I am running a 42t single ring with an N-gear Jump stop and a 48t outter ring (instead of a chainguard- I *THINK* is should serve the same purpose).

So this past weekend, I dropped my chain twice. Through the barriers, I'd get sloppy and as I would lift my bike, I'd manage to kick the pedals and make them spin backwards.

So my question: is a single ring setup going to keep a chain on the ring? Or should I just *really* concentrate on not kicking the pedals?

Thanks!
re: dropping a chain with a single ringfeathers mcgraw
Nov 24, 2003 5:15 PM
I run a similar setup, but with a chain guard instead of an outer ring, and I haven't had any problems. You could go with a double chainring setup. Sounds to me you should check your chainline. Just spinning your cranks backwards shouldn't cause the chain to derail if the setup is good.
re: dropping a chain with a single ringdamon
Nov 24, 2003 5:32 PM
What kind of drivetrain setup do you have?

A couple things that could help:
1) non-ramped chainring more positively engages chain. Try a BMX chainring (they are wonderfully cheap, too!)
2) short cage rear derailleur holds chain much more tightly (older derailleurs you could pull apart and increase the cage spring tension... havn't tried it on the newer generation, though)
3) like mentioned before, chainline

Those would be some of the first places to start. As a temporary fix, you could mount a front derailleur low and tight over the chainring (remove the outer ring) so there is no place for the chain to leave the top of the chainring, so even if you drop the bottom part of the chain, all you have to do is pedal for it to re-wrap itself... That is what i ended up doing on my 1x7 commuter (urban 'cross :-), but i have a long cage rear der. and a ramped chainring on that bike, too...)

-Damon
re: dropping a chain with a single ringfeathers mcgraw
Nov 24, 2003 5:56 PM
Those are real good points. I have a Spot ring, which isn't cheap, but beautiful and sturdy, as well has having taller teeth. That may be why I haven't had any problems. I'm not sure the front derailer would help, since the jump stop is basically doing the same thing.
re: dropping a chain with a single ringflyweight
Nov 25, 2003 8:41 AM
In addition to what the others have mentioned also consider shortening the chain. It should be just long enough to work on your largest cog and no more.
a little teaser.....anaerobic Max
Nov 25, 2003 1:05 PM
here's what i did. (this is the first shot of my new CX rig - i will post pics as soon as i got my new wheelset ;-)) )

originally i started with using a shimano XT front der. (down swing), but as i'm a real weightweenie i refused to keep a 130 g FD on my single chainring bike.

so i bought a DMR chainring guard - 39 € - nice thing, made from some sorta steel plates. should hold up just fine when used on XC or CX bike (check out the reviews on mtbr.com). though i was astonished by the relatively high weight - in fact 120 g for such a little part.

I started thinking how i could reduce weight. i started replacing the steel plates with alloy plates. the outer one has already had the holes drilled in and is only 1 mm thin. really featherlight!

the inner plate needed to be made from thicker alloy, since it has to give some stability: 2,5 mm thin, and i drilled 3 mm holes in areas where there is less stress on the plate.

the upper clamp is original, but i removed the lower one and replaced it with a very thin alloy plate that i attached to the thread in the frame (the one where you mount those pulleys to run a road FD if the cables run down the seattube)

check out the pic. post if you have further questions....

BTW: weight is now 60 g :-) 50% off the original chainguide.
here's another one.....anaerobic Max
Nov 25, 2003 1:07 PM
taken from between the seatstays
.....and another oneanaerobic Max
Nov 25, 2003 1:11 PM
taken from the left side. in the lower part you can see the screw that i screwed into the thread to attach the alloy plate to the frame (instead of the second clamp)
Looks like a cheese graterjhr
Nov 25, 2003 2:34 PM
looks like you could pop a block of parmisian on your chainring and go to town.

jhr
but a very light one ;-)anaerobic Max
Nov 25, 2003 11:02 PM
i'm also planning "chop-wheels" (to chop carrots, bananas, meat,..) with special BLADED spokes *haha* you could put the meat on your saddle and go for a ride to make it softer....
I really like the design. function over form.buffalosorrow
Nov 26, 2003 7:44 AM
I work in a metal shop and could start cranking those out for you, have you priced out for ti bolts? and drop a few more grams...what about carbon plates?

What do you think of a symectrical elliptical face plate, visually may look pleasing.

I am running 44/32 and have never shifted into the smaller ring, sort of keeping it that way for sake of knowing that chain drop could become an issue and the cost of single set up.

If you you can offer a solution at a reasonable price compared to that of a single set up, weight savings and functions equally to a double guard set up... you have a winner of a product.

Some comparisons:

Shimano dura ace Front der: 79g

Record Front der: 90g

*Chainring guard kit (2 rings+ long bolts):
$120, 80g plus bolts (guards 40g each)

*spooky carbon guards: $80 each, 19g each

*note, in many applications you need to switch to a longer bottom bracket for proper ring to chainstay clearance. Another expense.
good ideaanaerobic Max
Nov 26, 2003 10:49 AM
i've considered using carbon as a front plate since a friend of mine designes and constructs small carbon RC planes. but believe me, the carbon plate would be heavier (although this would be beyond measurable tolerances). maybe with a very thin carbon plate it might work. but i also like the drilled "cheese grater" look of my al front plate. the back plate is bent, so you need some sorta metal.

surely, the elliptic form would look great, maybe i'll try with a different plate. but the drilled plate wouldnt look that good if cut to an elliptic form.

mind that the rear derailleurs need an additional clamp. weight is then somewhere around 120 g, and it wouldnt work as good as a serious chain guard.

i've also tried to install self-made chainring guards. i made them from thin woodden plates (very light and cool looking), but the inner plate would rub on my seatstays unless i mount the middle chainring on the outer position, which would affect my chainline.

i will ask my friend if he could give me a small carbon plate, and then we'll try the elliptic plate, ok?
how 'bout full body CNC?buffalosorrow
Nov 26, 2003 11:05 AM
wouldn't match....anaerobic Max
Nov 26, 2003 12:58 PM
I think it wouldn't match the estethic appeal of my slim and fragile looking CX bike. those heavy cnc parts are rather made for DH rigs, dont they?

waht'S more, full body cnc sounds a little bit heavy.... any thoughts to produce a light one? i also lack a cnc-machine....

note that the most heavy part is the upper clamp, since it is the only thing made from steel, besides the srews (dont have Alloy screws)
wouldn't match....Love2du
Dec 3, 2003 9:04 AM
Just use an XT front der. I use this with my single ring setup and it works great. Not one chain drop yet.
no, i just like my DIY guide :-) (nm)anaerobic Max
Dec 3, 2003 10:13 AM