[Closed] Tensioning chain with EBB - Help!

You need to rotate it forward (increase chain stay length) to eliminate slack. Most EBBs will have sufficient adjustment, but they do vary in size and so capacity will vary.
What frame is it on?

EBB is positioned as far back as possible in order to get correct chain length - and thus move down nearer 3 o'clock to get tension - but chain comes up too short or too long - EBB doesn't seem to give enough back and forth adjustment ..

You could try using a half link but most Ebb's have enough adjustment to get tension good enough ime.

what frame/EBB is it?
what chainring/sprocket combination are you using?

I've never come across one that can't get tension, it might not get it exactly where you want the BB to be but they should all have enough range to take up slack.

Frame is Stooge - I'd not taken into account gear ratios - I'm running 34/20 and hoped on running the EBB @ 5 o'clock - I'd hoped to be able set chain length @ 3 o'clock and then rotate ebb to a lower bb height and set tension .. I've never used a half link and hadn't reckoned on needing a 'magic gear' to run the EBB @ 5/6 o'clock - tips appreciated !

It must be user error.

Never had an issue with tensioning my EBB Inbred, even with changing cogs.

Now i have a chaintugged slot dropout, I'm amazed how little adjustment it needs to take up slack; we're talking thread pitch sized adjustments or even fractions of. If you can't get a tight chain with an EBB and the comparatively large adjustment capability, you [i]must[/i] be doing something wrong.

Can you do pics?

If you derail the chain, what is hub axle to BB axle when axle is at 9 and 3 o'clock positions?

Thinking it through; if you put the EBB so the BB axle is at 9 o'clock (I'm always assuming you're looking at it from the drive side, ie, 9oc is as far towards the rear as it'll go)

Fix the chain using the minimum # links to get it around both chainring and cog and still connected.

And then rotate the EBB so the axle moves anticlockwise (9->8->7->6, etc.); the chain slack must get taken up because the distance between wheel axle and BB axle is increasing. Making allowances that the top and bottom chain run isn't exactly parallel, but for these purposes it's close enough..... to take up the slack of one pair of links (inner and outer = 1") then a 1/2" change in axle-axle length takes up a pair of links of slack - 1/2" each from top and bottom.

If an EBB doesn't have > 1/2" of adjustment I'll eat my hat. And if you need more adjustment than that, then you didn't use the minimum # of links in step 1.

However:

Just re-reading one of your earlier posts.

I've never used a half link and hadn't reckoned on needing a 'magic gear' to run the EBB @ 5/6 o'clock - tips appreciated !

You don't get to choose where the BB axle will be. You decide whether to rotate it down for a lower BB height, or up for more clearance, but how far to rotate will be decided by a combo of chainstay length, the ratio you're running and how stretched the chain is.

When I'm trying to work out the correct length of chain - which I've been doing simply by wrapping it around front/rear cogs and mating the links accordingly chain is either too loose or respectively too tight .. I guess it's not as simple as perhaps I've naively assumed to set bb position with EBB running SS - yeah I'm probably doing something wrong but a quick Google on such matters will show similar posts on the issue .

Start with the EBB at the back, set the chain loose, rotate the EBB forward (either up or down) to take up the slack.

Do as i said. Connect it with the EBB axle as far back as it'll go (9 o'c) using the shortest possible chain to connect it.

Rotate the EBB forward. If there isn't the capacity to take up one pair of links then the EBB has been spectacularly badly designed.

I always used to try and get the bb between 12 and 3 o'clock. I figured chain tension would tend to help stop the EBB rotating in the Shell that way.

The only EBBs I've heard of that occasionally need a half link are the bodge jobs that give you some adjustment on a normal (used to be normal, kids these days etc) English thread BB. Sometimes enough to tension a SS chain on its own, sometimes not.

Anything with an EBB like your stooge will have enough on its own. Start at 9 o'clock slickest. If you only get to 10 or 8 before the chain's tight, then those are your choices for now.

OP, cna you clarify:

are you saying you can't take up enough slack with the EBB to get the chain tight?

OR

that you cant get the chain tight with where you want the BB axle to end up?

Where I want the axle to end up - I want the BB low and as far back as possible - which is about 7 o'clock (viewing from drive side)

To get it to 7pm just follow the above indstructions:
BB at 9pm (or 9am, that's fine as well)
Put chain on and join it.
Rotate BB down until chain is tight.
Cross fingers that this means it's at 7pm.
If it's not, ride it until the chain wears the re-rotate.

The only choice you have with EBB position is up or down.
When you're running it singlespeed it's main function is to tighten the chain.

As above fit the chain with the EBB in the most rearward position.
Then rotate it either upwards or downwards depending on the ROUGH LOCATION you want the BB in.

The only choice you have with EBB position is up or down.

There's even a logic to that decision. The pedals pushes the BB down, and the chain pulls it back, so the best place for it is either 1-2 o'clock or 7-8 o'clock.

The mistake you are making is trying to set it at a predetermined position (5 o'clock). That is defeating the object of the EBB as the position is dictated by where it needs to be not where you want it to be.

Yes you could use half links and gearing changes to get it in an exact position (as you would with a "magic" gear) but you don't need to do any of that because you have an EBB. A cm difference really doesn't matter and one ride and you won't notice where the BB is...

? This.