Serrated Brake Cylinder Rods

[MoonlightVFR]

Question

What was the designer's purpose in supplying serrated brake cylinder RODS?

Function of the serrations?

[Bruce Fenstermacher]

The parking brake lever engaged the serrations. This system is superior to the later system from the standpoint that it can not be accidentally engaged like the later system can. While I removed the later system from my first 170, the earlier system is still intact and will remain so long as I have the serrated rods in my current 170.

[hilltop170]

Don't the serrated rods have a bad history of breaking?

[Bruce Fenstermacher]

Don't the serrated rods have a bad history of breaking?

Don't the non-serrated rods have a bad history of accidentally engaging the parking brake and ground looping the airplane?

Yes Richard, apparently, at least one broke. I wonder when it, (they) broke if there was any other damage. Guess if it happens at the wrong time it might not be pretty.

Ours have stood the test of time. We feel no need to change them now.

[n3833v]

I still have the serrated rods but I safety wired the catch levers so they cannot engage the rods. I never had any trouble but I didn't want any lockup at the wrong time.

John

[Waterboy]

Is there a rebuild kit available for the serrated rod cylinders?

Mine leak.
I fill them and they leak static, sitting in the hanger not being used. After making a mess on the hanger floor they find a happy place and stop leaking. I am not sure how they leak if all the holes are in the top?

I acquired a nice set of Cleveland 10-35 cylinders at a good price. But I am having trouble finding approval for installation. Here is a link to the other thread

http://www.cessna170.org/forums/viewtop ... =24&t=6394

I am still waiting for a call back from the tech rep at Cleveland, I talked to some one who was covering for him and he did not know of an approval for installation on the 170.

If any one has Cleveland 10-35 installed in there aircraft I could use some help with the how you went about the approval process. There are several threads on the 170 site that mention the 10-35s at the appropriate replacement.

thanks,
Ken

[Bruce Fenstermacher]

Ken, what you are describing is not possible unless it is leaking at the line fitting at the bottom and then I wouldn't know why it would stop till it's dry.

Are you sure your not over servicing them?

Filled to the brim they can leak out the vent hole in the plug. Any that comes out can look like a lot but maybe they aren't continually leaking. If they find a level, don't leak further, and work, that is likely your service limit.

[Waterboy]

Bruce, It is possible that I am over servicing them. They may leak when first serviced and then it takes awhile to run to the drain holes in the belly. There is fluid on the serrations of the rod, indicating a leak from there.

I have been filling to about a 1/4 of an inch below the bottom of the filler hole. When they stop leaking the fluid level is down a good inch. I have had the right brake get soft when the fluid is at that lower level. A pump or two returns the brake to normal. At that level (down an inch) I am thinking air is getting under the lock-o-seal? Not sure, but thinking that is what will happen when the level gets too low.

What level of fill do yours run at?

[Bruce Fenstermacher]

I would service it about 1/4 below the filler opening. My partner would service them until it runs out the top then wipe the excess off. We are not overly concerned with some oil in the belly. I do not recall substantial oil on the serrated rod.