hydraulic brake actuation

On Jan 7, 3:19*pm, DRN wrote:
You say you have "long run of stretchy cable".
If you didn't replace it, you're using up lots of travel stretching
the cable.

May be a minor point but the lost motion in light weight bowden cable
systems is typically not caused by stretching of the inner, rather by
compression of the coiled outer sheath.

On a cable with any bends the compression shows up as a change in the
shape of the cable run. Cable length change caused by compression of
the outer is the reason that special non compressible cable outers
were developed for 9 and 10 speed indexed bicycle gear systems.

The compression of the outer sheath can be reduced by minimizing
bends, optimizing bend radius, and/or by going to a heavier gage. All
cable fittings should butt square when relaxed or under max load.
Optimizing the cable run can work wonders even if the materials are
not changed.

Andy
(Years of experience with British motorcycles and now relearning it
all building and modifying mountain bikes)

DRN wrote:
On Jan 7, 4:56 pm, Greg Arnold wrote:
DRN wrote:
On Jan 7, 3:38 pm, Greg Arnold wrote:
wrote:
I built such a system for my former AS-W12 using a Cleveland system.
Worked fine but make sure the entire system is as stiff as you can
possibly make it. Use heavy motorcycle bowden cable and make the run
as short as possible. Also make sure the master cylinder mount is
rigid.
The ratios from brake handle throw (e.g., what is the max throw you
can get with your hand on the stick) to the throw on the master
cylinder actuator is an interesting geometric cut-an-fit. Making your
own handle will help a lot.
I much prefer spoiler-actuated brakes due to the additional force you
can apply with your entire arm/shoulder, the fact that both drag
devices are appropriately on one handle and the difficulty in mixing
fine-scale pitch/roll inputs on the stick with the gross-scale motor
skills of pulling like hell on the wheel brake.
I installed a Tost disc system (modified Cleveland) in my Discus A.
Just uses bicycle cable, and the run is from the handle on the stick all
the way back to the master cylinder alongside the wheel well. The
problem was that the lever on the stick (designed for a drum brake) hit
the stick before there was much braking action. This was due both to
the shape of the lever and the long run of stretchy cable.
After spending considerable time surfing bicycle shops on the internet,
and ordering several different bicycle brake handles, I found one that
is a perfect replacement for the SH handle. It is shorter and curved
away from the stick, and allows you to apply any pressure you want
without the handle hitting the stick.
Thus, you can make such a system work with bicycle components.
Um, why didn't you just replace the Bowden cable with something
more appropriate ??
See ya, Dave
I don't know what would be "more appropriate" than an arrangement that
works perfectly.

Apologies if I mis-understood your email.
You say you have "long run of stretchy cable".
If you didn't replace it, you're using up lots of travel stretching
the cable.
If you fixed the cable problem, you wouldn't have needed to change the
handle ?

Either "fix" would work, but changing the handle seemed easier and as
effective.


And you would have better leverage ?

Sounds "adequate" but hardly "perfect", especially as soon
as any additional deficiency develops...

Sorry if I mis-understand !
Best Regards, Dave "YO electric"

On Jan 7, 5:44*pm, Andy wrote:
May be a minor point but the lost motion in light weight bowden cable
systems is typically not caused by stretching of the inner, rather by
compression of the coiled outer sheath.

Absolutely right, sorry I wrote imprecisely...
The sheath (housing) is after all a wound spring !
Best Regards, Dave

Brad,
I found a picture of the break handle I made
http://www.soaridaho.com/Schreder/HP-18/C-FETQ.html
5th picture down.
Udo

Here is some photos of the stick/cable system I built for my HP16.
While It won't stand the glider on the nose it is adequate.

http://www.soaridaho.com/Schreder/Co..._Stick_Mod.htm

Brian
HP16T

Thanks for all the ideas, suggestions and links guys!

Looks like I'll be using a wheel and brake combo listed as a C-90. It
uses an Azusa 5" wheel with a hydraulic disc brake. For my
"lightweight" version of the HP-24 it should work quite well, and the
brake disc is set on the "inside" of the wheel rim so there will be a
slimmer overall package.

The trick I guess will be fitting a stick mounted handle and cable
setup to give me good actuation of the master cylinder. I really do
want the brake handle on the stick, so I'll just make it work, and may
as suggested end up making my own handle.

Cheers,
Brad