my chain on my tall bike is rediculously loose like i have to hop off and put it back on about 4 time in a 1/2 kilometer ride i have a derailer or 2 how can i rig it up to tension it or whats another way to do it

try a ghost/phantom cog:

http://www.dirtragmag.com/forums/attachment.php?attachmentid=17566&stc=1&d=1189540866

or

take a link out/use a half link

or

when tensioning your chain, pull the drive side all the way back in the dropouts, tighten the HELL out of THE DRIVE SIDE. straighten the wheel, then tighten the other side.

or

use a stripped rear derailler and a longer chain. the springy mechanism should heep it taut. (i like this way cause i can hop off and switch gears manually if im feeling lazy, or doing a big hill)

or

all of the above

do you have any close up pics of a derailler being used to tighten it, my rear wheel has a couple gears so this would probably be best for me

just put the rear derailer on as usual. cut the cable and all that crap off. put the chain on AS USUAL, with the derailer. the springy thing in the derailer makes the chain tight, no?

the end.

you could also leave the cable on/get a longer cable, and have a geared tallbike. whee.