TITLE: Ideas for a DIY bike chain tensioner
DATE: 2018-08-31
AUTHOR: John L. Godlee
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This is a set of notes I made on images I gathered from around the
internet, mostly on mountain bike forums, about making a DIY chain
tensioner for a single speed bike. One day I'll make my own.
This first chain tensioner seems very simple. A piece of flat metal
with a hole punched through at one end for a jockey wheel and a
channel taken out of the other end to sit under the wheel
tightening screw. The issue is that there is no spring in this
method, so any tension put on the chain could stretch the chain,
then the tensioner position would have to be reset manually
otherwise the chain could fall off the jockey wheel.
This tensioner I feel is at the other extreme. It would require so
much effort to make I might as well just buy a chain tensioner. It
has a spring and I presume one of the pieces of metal attaches to
the bottom hanger of the frame like a normal derailleur.
Adapted derailleurs
Usring an old rear derailleur seems like a great idea, as all the
parts are available and they should fit onto the bike with few
problems, especially if the derailleur is from the bike being
converted. On both the examples below the rear derailleur has been
tightened as far as it will go by snipping a small length of wire
from the original gear lever and using it to lock the derailleur as
far forward as needed. The first example only uses one of the
jockey wheels, while the second uses both. Using both jockey wheels
creates more chain wrap around the main cog, which reduces the
chance of it slipping under a lot of torque. The only problem I can
see with this method is that rear derailleurs can be quite heavy. I
wonder whether certain bits can be removed?
This frankenstein is pretty interesting. It's made out of a spring
loaded brake arm from a mountain bike, with a jockey wheel screwed
onto the end. I reckon this would be a really good option IF you
already had the parts, otherwise gathering them all together would
be a pain.
Frame attached chain tensioners.
These chain tensioners don't attach to the rear mech hanger of the
bike, instead they attach to the chain stay on the frame.
Additionally, they tend to push the chain up rather than down,
which increases the amount of chain wrap.
This one is made from a front derailleur with a jockey wheel
screwed through the end. This one is easy to attach to the chain
stay as front derailleurs often have adjustable p-clips to attach
them to the seat tube on. Again there is no spring mechanism in
this one so although it looks very simple, I would rather use
something else.
This one is still a bit of a mystery to me. I think it's a
skateboard wheel, but it looks like the attachment is brazed onto
the frame.
This one looks very easy to make, but I can imagine that it would
increase the friction on the chain quite a lot as there isn't a
jockey wheel. I guess with this design one could easily be added
however.
This one seems like a really great idea. All the parts should be
sources and it has a pretty robust looking spring mechanism.
Although this one is on a weird tandem setup, it could easily be
attached upside down to a chain stay on a normal bike. It needs:
- 2 extension springs
- 1 p-clip
- 2 strips sheet metal
- 1 jockey wheel
- 3 bolts (1 to fit the jockey wheel, 2 arbitrary size)
