Plastic Chain Guides
- From: Giles
Puckett
Subject: Re: [hpv] Making your own chain tubes to replace/supplement
idlers
Chain tubes are good. IMHO they complement, not replace,
rollers.
Recipe: obtain/borrow a hot air gun. Buy from H/W a
length of plastic black garden watering system tubing, I
think it's PVC, 12mm (1/2") diameter.
Also buy a 10mm (3/8") round wooden dowel of
sufficient length.
The tubing will come in a roll and will not lay straight.
Cut off the right length and push it onto the dowel,
heating it up as you go. Let it cool completely while the
dowel is still inside. This will straighten it. Once
cool, remove the dowel and heat up the ends of the tube.
While hot, flare them with a ball peen hammer or other
suitable round object, so the ends have a little bell-mouth
shape.
When mounting, use three zip ties thus: one tight round
the plastic tube, one tight round the frame, and the
third linking them in a sort of linked-rings arrangement.
Adjust this one till the spacing is right and the tube
floats on the chain. Sometimes this middle zip tie breaks
if it's flexed back and forth a lot (happened to me due
to use of Biopace chainring) so it might be a good idea
to use two in this position.
Total time 30 minutes, cose $10 (and you can make a lot
more of them out of the great big roll of tubing you had
to buy)
- From: Richard
Drdul
Subject: [hpv] Re: Making your own chain tubes
I used 1/2" irrigation tubing, available in big
rolls (typically 50 feet) at hardware stores. There are
two thicknesses of tubing -- I used the thinner stuff (the
thicker stuff is called riser tubing). Push a dowel
through the tube to hold it straight, then blast it with
a heat gun or a blow dryer until it stays straight
without the tube inside. I used a wooden lemon juicer to
slightly flare each end of the tube (while applying heat).
I attached the chain tube to the bike with two stainless
steel hose clamps (oh, the shame of it!) and a 5"
piece of nylon webbing (same stuff as used for straps on
helmets). Remove the topside idler and attach the nylon
webbing at the hole where the idler was mounted. The
nylon webbing is attached to the frame at the midpoint of
the webbing (with a metal grommet to prevent the hole in
the webbing from distorting), and is attached to the
chain tube at each end of the webbing with a hose clamp.
That holds the chain tube in place even when
backpedalling, and allows some slack for the chain tube
to move sideways and up-and-down as the chainline changes
with different gear combos. The only thing you need to
check is that the hose clamp is circular -- if it's
somewhat oval, the chain tube will be somewhat oval at
that point, and the chain will stick (especially when
backpedalling) -- just squeeze the hose clamp into shape
with pliers.
The resulting installation looks very slick -- as if it
were stock equipment. My V-Rex is now quieter, less gunk
gets on the chain, the chain doesn't slap the frame
anymore when I shift, and the best part is that it's
probably just as efficient (if not more so) than the
idler. Keeping my clothes clean wasn't a huge problem for
me, as I use White Lightning, but it's still a nice
benefit.
Date: Mon,
7 Aug 2000
From: Sverker
Fridqvist SWEDEN
Subject: [trikes] Re: Chain tubes, friction, loss of
energy
List-Id: Recumbent Human-Powered Trikes <trikes.ihpva.org>
Teflon tubes: Good idea!
I checked the internet for suppliers; here's a few:
http://www.caprub.com/tefhose.htm
http://www.teleflexhose.com/
http://www.integraco.com/chemfluor.htm
Obviously, it is possible to find teflon hoses. My search
(+teflon +hose) rendered 8416 hits...
- From: Robert Stein
Subject: Re: [trikes] Chain tubes, friction, loss of
energy
Date: Sun, 6 Aug 2000
List-Id: Recumbent Human-Powered Trikes <trikes.ihpva.org>
I tried out on my prototype almost all allowed chain tube
and tubeless options. The long and short, on the drive
and return side. Also experimented with very soft and
hard tubes. (must say that I had tubes lying around and
whole lot of time on my hands)
I came up with similar conclusions:
If the tube is installed properly, so, if there's a large
enough inside diameter, and it doesn't force the chain to
bend/break, than the feeling of drag is basicaly
insignificant. Still, there is a small amount of drag
which one feels when needs to achieve high speeds solely
by pedaling. (no running downhill) The final version of
the trike has a relatively short piece of tubing on the
return side, just to protect the powder coating on the
crossmember tube where the chain passes by. Also, I
believe that if roller/pulley wheel(s) are used, it is
very important that they must be set up with much care.
After much experimenting (nothing scientific), I found
that the best solution is a combination with one hard
rubber roller wheel on double sealed bearings which
reduces the friction and the noise on the drive side, and
because of the setup of the chain management, couldn't
avoid the second one, which is on the same axle, side by
side with the first one, but the second one is in
conjuction with the previously mentioned short piece of
tube, keeping the chain in desired line of movement, and
represents almost no drag. The option without the second
roller wheel increased the drag / friction through the
tube because the chain virtually brakes up toward ground
or lies on the crossmember tube. This way, the supporting
point is on the roller wheel, not on the tube. These
conclusions, of course, came on a specific trike frame,
with a simple chain management. If I could do so (which
seems impossible because of low boom and 26" rear
wheel) I would like to manage the chain with absolutely
no pulleys, idler or roller wheels and without tubes just
like the short upright bikes are solved, but as they say,
every coin has two sides. Trikes and other recumbent HPVs
have so many good sides that I personally can live with
this "problem" that chain management represents.
If there's a solution to avoid the short piece of tubing
without further compromising, or introducing a second
pair of roller wheels, I'm sure that someone will come up
with that in the near future. Many of us are working on
that while riding and maintaining the machines, so if
there's a solution, we'll do it!
Robert Stein Road Shark designer
PS there's a picture of the presented solution at http://www.wrhpv.com
(go to road shark page and click on the small picture to
enlarge)
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Friday, 07 September 2001