DAVID ARONSON'S RV TECHNIQUE PAGE

BLEEDING BRAKES ON THE RV SERIES EXPERIMENTAL AIRCRAFT

In response to a lot of traffic on the Matronic's list, a short tech session on bleeding the brakes follows. 
This is not the only way to achieve airless hydraulic systems but I chose to do it this way due to:

1.    Ease of technique.
2.    One person can easily finish the job.
3.    Clean, fewer spills.
4.    Little equipment necessary.
5.    Fills from top up, forcing air to the top.  Complex systems are as easy to bleed as simple systems.

I have bleed many systems using several techniques.  Pushing the pedal, pumping the system and releasing the bubbles at the bleeder screw is the most popular.  This system will work but requires two people, adding fluid in a cramped area and potentially can be very messy.  Here is the technique step by step.  I tried to accomplish this with a small squirt type oiler but the pressure required to push the fluid up to the reservoir made it very difficult.

                FIG. 1                                                            FIG. 2                                                        FIG. 3

               
    Click pictures for larger view

FIG. 1        Remove the pump tubing and replace with the clear tubing listed below.  Insert into container of hydraulic fluid with
                    the handle of the pump all the way down.  Pull-up on handle and fill the pump with fluid. 

FIG. 2        Open the bleeder valve on the brake caliper just enough to allow the uptake of fluid.  About 3/4 turn is enough.
                   Remove the brake reservoir cap and place a rag under the reservoir.

FIG. 3        Attach the tubing to the bleeder valve on the caliper and begin pushing down on the pump handle.  Quite a bit of pressure
                   will be necessary.  Keep an eye on the reservoir and listen for a spilling sound from the reservoir warning of quick fill.
                    When the reservoir is filled, disconnect the tubing from the caliper and tighten the bleeder fitting. 

Repeat this simple technique for the other wheel cylinder.  This system works with separate reservoirs or a single system.

Materials;

1.    Bicycle pump
2.    3 ft. 3/16" ID clear tubing
3.    2 radiator type clamps for tubing
4.    Aircraft grade hydraulic fluid.

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