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ss + vert dropout ?

LordOpie

MOTHER HEN
Oct 17, 2002
21,033
1
Denver
How hard is it to find the right cog+ring combo to create a chain length that'll work?

I keep reading on another forum people say that such-and-such a bike will need a tensioner, but I don't think so.

So, what's the math needed to find the right chain length for a cog-ring-chainStayLength?

(Let's assume a 0.5-1.0" vertical flex in chain movement)
 

jimmydean

The Official Meat of Ridemonkey
Sep 10, 2001
29,553
2,236
Portland, OR
I have a singulator on mine and I like it. Do you just not want to run one? I have a gear hub (spacers used) because I might switch to gears some day.
 

LordOpie

MOTHER HEN
Oct 17, 2002
21,033
1
Denver
Do you just not want to run one?
yeah, pretty much.

Someday soon, I'm going to build up an internal geared hub bike for all-weather commuting and because of such bad weather, I don't want a derail or singulator* -- as simple and maintainenance free as possible.

I remember reading somewhere about the math, but cannot remember anything about it whatsoever, erg.

I don't yet have a frame for the bike yet, tho I do like the Surly LHT, so I want to know if vert drops is a problem before I go that direction :)

Thanks for your positive feedback on the singulator.


* EDIT: the internal geared hub will have a coaster brake, so I'm pretty sure that'd rip a singulator off?
 

H8R

Cranky Pants
Nov 10, 2004
13,971
20
My broken collar bone was proof enough that there is no "just right" length.

Chain slip is a bitch.
 

LordOpie

MOTHER HEN
Oct 17, 2002
21,033
1
Denver
My broken collar bone was proof enough that there is no "just right" length.

Chain slip is a bitch.
I'm sure you're right, which is why I'm asking, but my ss roadie has 1" vertical movement (slack?) and hasn't been an issue. I tried tightening the drivetrain up, but read that you don't want it too tight and 1" slack is better than fully snug, so I left it as such.

Maybe pavement riding is more forgiving?
 

H8R

Cranky Pants
Nov 10, 2004
13,971
20
I'm sure you're right, which is why I'm asking, but my ss roadie has 1" vertical movement (slack?) and hasn't been an issue. I tried tightening the drivetrain up, but read that you don't want it too tight and 1" slack is better than fully snug, so I left it as such.

Maybe pavement riding is more forgiving?
I had a beater SS built up. Found the "perfect" chain/gear/cog combo. Worked great for months.

I was riding home from the first day at a new job at Medina Cycle Works (now Wrench Science). Got around the corner, stood up to sprint off a stop light, whammo. Chain slipped, I hit the street. Shattered collar bone, bruised ribs, etc.

I had to walk back and call in sick after one day. :(
 

LordOpie

MOTHER HEN
Oct 17, 2002
21,033
1
Denver
Just a thought, but maybe run a Halflink chain. Little heavier, but you can better finetune the chain length.
That's what I'm saying?!

You can have a small amount of chain movement, but not enough for the chain to easily jump off. You manually derail the chain off the ring to get the rear wheel off, yeah? And then you don't need a singulator, right?
 

DirtyMike

Turbo Fluffer
Aug 8, 2005
14,276
858
My own world inside my head
If I were building something like this, I would be using a half link chain. But yeah the idea would be to get as clsoe of a gear combo as possible, and use teh half link chain to get the chain as close to tight as possible without the need for a tensioner.


Man from the sound of it, your gonna have something built up pretty soon!!!
 

johnnyru

Monkey
Feb 20, 2004
125
0
Slingerlands, NY
I would say get a frame with an eccentric bottom bracket (EBB). Unless you want a road frame, not sure any road frame come with EBB's. What's wrong with horizontal dropouts?
 

BikeMike

Monkey
Feb 24, 2006
784
0
You can run a single half link in a normal chain. Chains composed entirely of half links are more or less BMX fashion statements.

A somewhat impractical, though kind of cool (and kooky) alternative would be to try out a ghost gear setup. Insert the perfect size cog between your chain (if you can get it so the chainstay doesn't get in the way) and it rotates in place and keeps your chain tensioned (in theory).

Also: if you get close enough to tension w/ right gear combo and/or a half link, and you don't have little weenie dropouts, you can file a wee bit off the back, potentially giving yourself a couple mm's to play with.
 

brungeman

I give a shirt
Jan 17, 2006
5,173
0
da Burgh
Absolutely nothing, except that my body geometry isn't typical and the only production frame that I've found that works for me is vert. It's $400, other wise I could go custom for $1100.
eccentric rear hub? (hub/wheel build < getting a custom frame) or use a single half link to fine tune it.
 

Wumpus

makes avatars better
Dec 25, 2003
8,164
154
Six Shooter Junction
Have fun:

Since bike sponsor Giant no longer offers a singlespeed due to low sales in the niche category, Decker took a unique approach to acquiring his one-geared racer; he modified his 2005 team-issued hardtail. Decker says his conversion of the geared bike, which featured essentially the same frame as his 2006 XT-C, is simple; but takes time and patience.

For the first step, Decker said, "I cut the (derailleur) hangers off. My magic system for getting the right chain tension involves starting with a handful of [used] chains with different stretches and a bunch of chainrings. To get that perfect tension without any of those little do-hickeys and with these [non-horizontal] dropouts, you just have to take the hour or two hours to find the perfect combination. I've done it a bunch of times."
 

Westy

the teste
Nov 22, 2002
36,566
3,363
Sleazattle
I tried this with my hardtail and could never get it to work. You need a bike with a near perfect chainstay length or a large selection of cogs and chainrings to get it just right.
 

BurlyShirley

Rex Grossman Will Rise Again
Jul 4, 2002
19,183
1
TN
You know Loopie, you could fool around for the rest of your days with all these half assed bandaid fixes to an inherently flawed design, or you could just get a decent frame with some horizontal dropouts and do it right. I mean if you're after simplicity after all, just go the least complicated way; the right way.

Surly 1x1's, Karate Monkey, Pacer frames come cheap.
 

Westy

the teste
Nov 22, 2002
36,566
3,363
Sleazattle
What Burly said.

You really don't want to mess around with the possibility of losing a chain especially when you have the hair brained idea of using a coaster brake.
 

OGRipper

Turbo Monkey
Feb 3, 2004
9,737
166
NORCAL is the hizzle
I gotta agree with BS and Westy. There are ways to make it work, and you might get lucky, but factor in chain stretch and it's a moving target. A bit of stretch might explain what happened to H8R.

And maybe it's me but if you can derail your chain on an SS by hand, your chain is too loose.
 

LordOpie

MOTHER HEN
Oct 17, 2002
21,033
1
Denver
Magic gear ratio calculator here: http://eehouse.org/fixin/fixmeup.php
You rock! That's a great calculator.
Surly 1x1's, Karate Monkey, Pacer frames come cheap.
I really appreciate your help, but again, those bikes will not work for me unless I use a stem riser which I do not want.

I have a neck injury from a climbing accident that pushed my C1 vertebrae forward, so if I'm in a tight/low/aero position, I'll get a migraine as my spine compresses in an odd way.

And maybe it's me but if you can derail your chain on an SS by hand, your chain is too loose.
I've done a fair amount of reading about SS since getting mine and you don't want the chain too tight. You should be able to move the chain 0.5" up-and-down total distance.

That amount of proper slack does allow for manually derailing the front ring. It's only an issue if the chain line is off much.

Have a rear wheel built up around a White Industries ENO rear hub and you'd be golden.
Thanks bro! But DirtyMike posted a link to a coaster brake hub that's internally geared (7spd?).
 

LordOpie

MOTHER HEN
Oct 17, 2002
21,033
1
Denver
what type of purpose will this bike serve?
Utility, commuting, bad weather rides.

Which is why I'm looking at internally geared rear hub with coaster brake :)
Also, DirtyMike linked a front hub that has an internal brake.
 

BurlyShirley

Rex Grossman Will Rise Again
Jul 4, 2002
19,183
1
TN
Opie, I know you know this, so Im not sure why Im posting it. But such a unique situation might call of a unique solution. You've had custom before...
 

LordOpie

MOTHER HEN
Oct 17, 2002
21,033
1
Denver
Opie, I know you know this, so Im not sure why Im posting it. But such a unique situation might call of a unique solution. You've had custom before...
So you're saying that I should buy a custom frame for $1200 when I could get another LHT for $400?

timH -- who is that masked poster? :) -- posted a chain length calculator and it looks like there are several cog-ring combos that would provide an exact chain length necessary.

If there is a good reason to not do this, I'd appreciate the feedback. Otherwise, I'd rather save $800!
 

LordOpie

MOTHER HEN
Oct 17, 2002
21,033
1
Denver
Ha!

Someone tried a ghost ring to add tension to a stretching chain...



No, I will not be trying that, just thought it interesting and funny enough to share :)
 

H8R

Cranky Pants
Nov 10, 2004
13,971
20
If there is a good reason to not do this*, I'd appreciate the feedback. Otherwise, I'd rather save $800!
*See above posts about the shattered collar bone.


I'm not saying that will happen to you though. But there is a risk.


Make sure the chainline is DEAD on, that there is enough but not too much tension, etc. Make sure you use a dedicated SS chain and not a shift friendly 9spd chain.

Problem is, you always get chain stretch. As you ride after time the chain tension will drop. Without a tensioner or horiz drops, the chance of throwing a chain grows.

Eccentric hub would be the key here imho.
 

LordOpie

MOTHER HEN
Oct 17, 2002
21,033
1
Denver
Make sure the chainline is DEAD on...
Thanks!

I should clarify that when it comes to things that critical, like chainline, I'll have my LBS build it up.

And yes, I'll be running a SS/BMX chain.

And yes, ideally, I'll find a bike with horizontal drop outs. I just need one that has a 55cm TT and a noticeably long HT. :)
 

w00dy

In heaven there is no beer
Jun 18, 2004
3,412
28
that's why we drink it here
Ha!

Someone tried a ghost ring to add tension to a stretching chain...



No, I will not be trying that, just thought it interesting and funny enough to share :)
Don't knock the phantom chainring. It's simple, efficient, reliable, and easy to set up. Not to mention it gets lots of looks on the trail.
 

buildyourown

Turbo Monkey
Feb 9, 2004
4,837
0
South Seattle
I think it's pretty easy to find a combo that will be the perfect chain length if you have a half link (they are really cheap)
However, I was unable to find one that was the perfect length and was the proper gear ratio.

The trick I used was to use a "floating chainring" midpoint along the chainstay. Mine is just my short commuter so I don't need anything super burly.

edit: somebody beat me to the "phantom chainring"