Left Brake Not Working

 When I went flying on Thanksgiving the left brake wasn't working.  I only use them for taxiing and running up the motor, for pre-flight checks, so I went flying anyway.  They are heel operated and I'm getting better at using them.  I just think if you need them on landing you really need to get back in the air.  I'm sure the day will come when I have to use them after landing.

They are CUB brakes and in the CUB the cylinders are mounted, as shown, on the floor board between the rudder pedals, one pointing left and one to the right.  They are very easy to service in the CUB, you just lean in the door opening.

The way they work is, the Brake, Line, and Reservoir are filled with fluid, held in by the Diaphragm and Filler Plug.  When you push the pedal the plunger pushes on the diaphragm forcing fluid to expand the tube in the brakes.  This pushes the Brake Pads against the Brake Drum, very simple.  If the Filler plug comes loose the fluid just squirts out and that brake is dead.  That was why my brake was dead.  The gasket had gotten very hard and the plug came loose, so I made a new gasket, problem solved.

In the Fly Baby the cylinders are under the floor board.  There is a hole in the floorboard to access the filler pug but you need to lay on the floor under the fuel tank to get to it and add fluid, a real pain.

Instead I have a removable access panel under the cylinders.  With a 5/8" crows foot wrench and a little work you can loosen or tighten the filler plug from under the plane.  It takes  bit of dexterity to screw it in or out with your finger tips, but not much more trouble than while laying on the floor.

I have a gooseneck oil can for filling the reservoir.  It's much easier to fill it from below, then above, by using a piece of safety wire to hold the nozzle pointing down.  You just hook it in the opening and slowly squirt until it starts to overflow.  It's easy to see that it's full with a light and an inspection mirror.

I think I finally have all the air out of the brakes.  They feel better than they have since I put it back together.  

Now I just need a less windy day to go back to flying.

Brake Dragging Slightly

 

The left wheel is back off because there was a light drag in one spot.  It was there when I put on the new bladder.  I decided to taxi it a bit and then see if it was still there, of course it was.  It hung up the wheel enough I was worried it would do something squirrely when the wheel started turning on landing.  The right thing to do was to pull it back apart and fix it.

It happened in one spot as the wheel turned so I assume the 70+ year old brake drum is slightly out-of-round as well as something out-of-round with the mechanism.  

First I blued the metal frame thinking it was rubbing, based on the sound.  That wasn't it.

I used the blue marker to blue the entire inside of the drum.  Spinning the wheel rubbed plenty of blue onto 2 of the pads.  I measured those 2 pads and found they were 0.300" thick, basically new.  I sorted through the pads I have and found 2 which were worn  about 0.010" thinner.  That solved the stopping on the pads, but now I could for sure hear metal on metal wear.

I removed the pads and blued the metal frame that holds the pads in position, wheel back on and spin.

With the pads removed there were areas where the blue was rubbed off the frame.  After 4 hours filing a little, cleaning up metal filings, re-bluing, installing the wheel, spinning, removing the wheel and repeat, I stopped the metal rubbing.

The wheel spins great and the brakes are ready for a test flight.

I need the wind to switch back to a southerly wind and we're ready to fly.  Yay!

Left Brake Fixed

 

You can see the wet brake fluid on the brake puck, not good.  The bladder clearly ruptured.  It appears they haven't made any bladders since WWII.  Thanks to the war effort there was a lot of surplus.  As a result no one makes new bladders.  Grove does make some nice disk brakes to replace these for $920, a little out of my budget.

Fortunately a friend, Bernie Estes, had a couple CUBs in the past.  I rebuilt the wings for one of them.  He had put Groves on the other one 10 years ago, and still had the old brakes in his hangar.  Don't you just love people who keep useful things.

I used the best parts from mine and one of his to put together a good brake.  Maybe some day I'll switch to Groves.

I had trouble getting all the air out when I made the new brake lines so I got a syringe from the farm co-op.  It worked fine but the bladder itself wouldn't take any fluid.

Once I had the brake hooked up I used the syringe to fill the line from the bladder to the bleed valve.  Then I pumped fluid from the valve to the brake cylinder under the cockpit floor.  That worked, no air in the lines.

The wheel's back on and the brakes work great while taxiing the plane.

Now I need to solve the magneto problem.  I've removed the mag.  If I can't fix it with the parts I have I'll order all new from Fresno before I head to the AAA fly-in in Blakesburg.

Spark Plugs, Rain, Tie Down for Starting Motor, Throttle Cable and Brake Problems

 

I couldn't find a reason for the miss with the RH Magneto so I replaced the spark plugs with new Champion REM40E plugs.  I also replaced the plug leads with new wires from Fresno Air Parts.  I had one wire which, in the past, had rubbed through the insulation against the cowl bump so I wanted to change them anyway.  Th new ones have elbows to help protect against chafing.

As I got ready to run the motor the rain started so I quickly covered the cockpit.

You can see the wheels are chocked with ropes that allow pulling both chocks as one.

The tail is tied to a piece of rebar which goes into a tube in the ground and through an eye bolt in the hangar door.  The guy before me install them for his plane.

I made a 1/2" rope, about 5 feet long, with eyes spliced at each end.  I used 3/8" eyes because they fit the rope better.  The wrap at the end of the tucks is heat shrink tubing.  The forward end hooks to the cockpit operated tow hook.  Start the motor, pull the chocks, climb in, buckle up, and release the hook and you're ready to taxi.

Fortunately I did some more taxiing and found my foot was catching the throttle cable and reducing power, not good.  I've added some more cable ties so it's tight to the fuel line and my foot can't snag it.

When I came back the next day I found brake fluid leaked on the floor from the Left Brake.  The old bladder had sprung a leak.  I need to find a good cheap bladder or replace the brakes, big $$.

O yeah! I still have the magneto miss.