Ski Brakes

[bda]

Grizzly Claw Ski brakes

- On Carbon Concepts skis

Jeremy did a good job with this design, the lever makes it something that will keep working and not require constant maint.

I installed the Grizzly claw brakes last year because I have to taxi around other planes (with straight skis) for fuel, at an airport that plows the ice and snow smooth as glass. Not to mention the wind blowing me all over the place.

But

They did not work at all because the master cylinders that I have on my plane would only push 1/3 of the fluid needed to fully extend the "claw".

So I had to install Grove Master cylinder# 679-3 with a 7/8" bore to push the volume required to make these brakes work.

The Grizzly Claw brakes require a master cyl volume of at least .62 cubic inches to actuate all the way.

AK Airframes won't tell you that. And they don't care if the brakes don't work on your plane after you buy them. Very poor customer service.

The brakes work well now, with the new master cyl, if I taxi super slow, and the wind is not blowing. (My skis are oversized and super slick bottoms). I can turn with the brakes, and stop when needed. The one drawback is that the larger master cyl is pushing a lot of fluid, and the orifice sizes in the brake system are small, so the brake actuation is not instant, "kinda like stepping on a plum".

The only time they have not worked for me is when the ice/snow got packed in under the "claw" lever so it couldn't go down. I have to clean it out every time I get out., especially when it is warm/wet.

The harder the ice the better they work.

[cubdriver2]

Could you have pressurized the system to take up the slack?

Glenn

[bda]

Could you have pressurized the system to take up the slack?

Glenn

Not sure what you are asking??

What slack? The brakes are spring return...

[BC12D-4-85]

What happens if the pilot quickly pumps the brakes twice? Two shots of brake fluid should be expelled. That assumes a reservoir is connected to refill the master.

Back when we had to do that to extend worn brake linings or drums on vehicles.

Gary

[cubdriver2]

Not sure what you are asking??

What slack? The brakes are spring return...

Pressurize the master and lines so that the brakes are partly activated.
Example, if the spikes travel 2" pressurize it till they are always out 1" .
Then when you apply them they only need a small amount of fluid to fully extend.
Same thing we do with expander tube brakes to make them work good enough to lock a wheel

Slack = any unusable brake travel

Glenn

[bda]

I see what you mean.With these when you set them up you use spacers to put the claw tips just touching the ice. There is no free travel.

[aktango58]

I see what you mean.With these when you set them up you use spacers to put the claw tips just touching the ice. There is no free travel.

However, that does not mean that all the lines between the master cylinder and the actuator are totally full of fluid.

Pump the claw down, refill the master while holding the brake lever towards the tail, allows another teaspoon of fluid.

[skywagon8a]

[QUOTE=aktango58;843570]
However, that does not mean that all the lines between the master cylinder and the actuator are totally full of fluid.

Pump the claw down, set the parking brake, refill the master while holding the brake lever towards the tail, allows another teaspoon of fluid. release the parking brake.

[stewartb]

When struggling with my brakes Mr. Grove schooled me on brake masters. Stopping power requires pressure, not volume. The way some masters achieve pressure is by reducing the cylinder diameter and therefore the fluid volume. The need for volume is a different problem. It sounds like bda solved it.

Ski brakes are great tools on ice. Thanks for the user report!

[aktango58]

[QUOTE=skywagon8a;843571]

However, that does not mean that all the lines between the master cylinder and the actuator are totally full of fluid.

Pump the claw down, set the parking brake, refill the master while holding the brake lever towards the tail, allows another teaspoon of fluid. release the parking brake.

Thank you! Forgot that step... been a while

[stewartb]

Won’t work with vented masters.