Ventus 2cx brake

On Nov 26, 8:32*am, Andy wrote:

Why would anyone ruin a great hydraulic disc brake by actuating the
master cylinder with a bicycle cable?

When I was building a brake system for the center stick controls of my
HP-18, I decided I wanted the stick to have as little inertia, and as
little mass aft of the ptich pivot, as practical. Hence my decision to
use a mountain bike brake lever on the stick driving a fixed master
cylinder through a low-friction sheathed cable. That's why this
sailplane developer developed such a system.

My caution was driven by an earlier accident involving a late
acquaintenance whose sailplane unzipped in turbulence and distributed
parts pretty widely. That ship's control stick had been modified in a
way that some thought contributed to undamped PIO.

Thanks, Bob K.

On Nov 26, 1:05*pm, Bob Kuykendall wrote:
On Nov 26, 8:32*am, Andy wrote:

Why would anyone ruin a great hydraulic disc brake by actuating the
master cylinder with a bicycle cable?

When I was building a brake system for the center stick controls of my
HP-18, I decided I wanted the stick to have as little inertia, and as
little mass aft of the ptich pivot, as practical. Hence my decision to
use a mountain bike brake lever on the stick driving a fixed master
cylinder through a low-friction sheathed cable. That's why this
sailplane developer developed such a system.

My caution was driven by an earlier accident involving a late
acquaintenance whose sailplane unzipped in turbulence and distributed
parts pretty widely. That ship's control stick had been modified in a
way that some thought contributed to undamped PIO.

Thanks, Bob K.

Even better is to use a direct linkage from the spoiler
and keep this buggery off the stick completely !
See ya, Dave "YO electric"

PS: I know, doesn't work on the HP-18, no spoilers;
my whale has it on the stick...

On Nov 26, 11:05*am, Bob Kuykendall wrote:
When I was building a brake system for the center stick controls of my
HP-18, I decided I wanted the stick to have as little inertia, and as
little mass aft of the ptich pivot, as practical. Hence my decision to
use a mountain bike brake lever on the stick driving a fixed master
cylinder through a low-friction sheathed cable. That's why this
sailplane developer developed such a system.

Did you consider using a mountain bike hydraulic brake lever? Perhaps
they were not available then. Is the mass of the lever even
significant compared to the mass of the pilot's hand and arm that are
also usually, and certainly during a PIO, attached to the stick?

Andy

On Nov 26, 3:00*pm, Andy wrote:

Did you consider using a mountain bike hydraulic brake lever? *Perhaps
they were not available then.

Yes, I tested a promising one at the time. As little displacement as
my Cleveland caliper requires under typical conditions, it still took
a couple pumps of the lever before it pressured up.

Is the mass of the lever even significant compared to the mass of the
pilot's hand and arm that are also usually, and certainly during a
PIO, *attached to the stick?

Not known. I do know that the available hydraulic master cylinders
with attached reservoir are around a pound or so. I also know that the
human hand and arm has a lot of inherent damping, and also that only
about half the mass of the forearm counts as sprung weight. In this
case at least I decided to develop conservatively and move on.

Thanks, Bob K.