Brake issue

[Kai]

Sorry,

I’m not that far down your path yet.

Although I’ve had the Aeroconversion hydraulic brake setup in my Sonex for the last three years, I can’t make them work as I would like. They won’t hold the plane during runup, and braking action during rollout is hardly any better than the old mechanical ones.

As far as I can understand the issue is getting the air out of the system. I religiously follow the procedure recommended by Sonex. But after a short while I again have to ‘pump’ the handle in order to have any braking action at all- and lo and behold: the air bubbles are back.

I can’t find any leaks. The discs are nice and dry. No spill anywhere. Hardly any loss of fluid in the master reservoir. All fittings dry as a desert. The bores in the calipers are prestine. Piston o-rings replaced 2-3 times every season. Anywhere else I should look?

What the blazes do you guys do to make these things work?

Thanks
Kai

[WaiexN143NM]

Hi all,
It may be how you are bleeding them? are you a one man or two person operation?
i’ve posted before on check valve brake bleeders. you can find these at your local auto parts store. run a tube into a clean cup. crack open the bleeder valve, get some fresh brake fluid handy, sit in plane and pump the handle. add more fluid as needed. tighten valve replace master cap. should be good to go.

WaiexN143NM
Michael.

[Area 51%]

The reservoir capacity of the master cylinder my be your issue. The wheel pistons will use-up the small amount of reservoir fluid in short order as the brake linings wear. These master cylinders are not vented, and when the system would like to draw fluid from the master cylinder to take up space, a vacuum forms making it possible for air to get sucked in past the wheel piston seal.

I added an external reservoir from a motorcycle brake system and have never had any air get introduced into the system.

I can send you a picture of my setup if you PM me your email.

[Kai]

Hi,

Great- a photo of your setup would be very welcome.

PM with email address sent.

Thanks
Kai

[builderflyer]

The reservoir capacity of the master cylinder my be your issue..

The capacity of the master cylinder is very limited but a simple way to get additional capacity is to screw a 3" tall, 1/2" o.d., standpipe into the threaded hole that the filler plug occupies. I found such a brass tube that came threaded at both ends along with a brass cap at the local hardware store. This tube adds enough capacity such that the brake fluid level can drop a little without the possibility of getting air in the attached brake lines.

Art,,,,,,,,,,,,,,,,,,,Sonex taildragger #95,,,,,,,,,,,,,,,..Jabiru 3300 #261

[racaldwell]

A cheap way to add the reservoir is with tubing. This way you can see the level and know when to add fluid. I did this with my One Design and used a syringe to add fluid by inserting a small tube connected to the syringe. I used teflon tubing 5/16" OD x 1/4" ID. On my Xenos, I have a large access panel on the glasreshield to access these for refilling. Surprisingly, the volume in the tubing is greater than the volume of the Grove brake reservoirs he sells.

Rick Caldwell
Xenos 0057