The dreaded dragging brakes.

[John Courte]

My DAR called out the fact that there were no cotter pins on the brake pedal or brake master cylinder hardware, and I remember actively blowing off that task "until later" some time around 4 years ago because the yoga poses necessary to get under the panel and work with the brakes in-situ are both unfamiliar and painful.

So of course, in correcting the deficiency for airworthiness, I torqued the hardware and installed cotter pins. My brakes now drag, both sides, the right a little worse than the left. I'm just glad I found this out on a taxi test/joyride yesterday. This led me to the wealth of information on VAF regarding this issue, which seems to be fairly common, at least common enough to merit several threads.

Of course, the result is the need for more yoga. I'm going to try just backing off the castle nuts a bit and see if that works before I have to buy a couple of twelve-dollar AN3-58's or disconnect everything to install return springs.

So my advice to all the new builders out there: Sort this out before you put your ship on the landing gear and close the forward deck skin, especially if it's a taildragger.

 

[crabandy]

I bought some 3/16 rod, cut to length and threaded the ends instead of buying the long bolts.

 

[RV10inOz]

Not sure if this helps but regardless the pistons may not want to come all the way back, and still drag, so we installed a coil spring over the rod to apply enough return that the pedals and master always return back. Works a treat!

 

[flyboy1963]

What kind of rod?

I bought some 3/16 rod, cut to length and threaded the ends instead of buying the long bolts.

Craig, curious what kind of rod is of similar strength, before I go out and buy some brass or whatever.
....also wonder if just drill & cotter pin each end was considered, rather than the trouble of threading?..... easier to do on the field for me!

 

[crabandy]

This thread had some good ideas, http://www.vansairforce.com/community/showthread.php?t=11598&highlight=Brake+return+springs
I used the parts list for McMaster Carr for the collars, springs and bushings. Along with the solid hinge point (bolt/tubing/rod/etc) the brake pedals work perfectly.

 

[Captain_John]

I used appropriately sized AN bolts instead of threaded rod. It was about $10 per bolt. The rod would likely be just as good in all regards, plus it is cheaper!

CJ

 

[Tony Spicer]

So of course, in correcting the deficiency for airworthiness, I torqued the hardware and installed cotter pins.

Don't torque it! The fastener needs to be free to rotate.

Tony

 

[TS Flightlines]

No piston travel--

Hint---make sure that the master cylinder rods are at the full 'aft ' position, and not depressing the pistons slightly. If so, it will create some residual pressure and apply pressure to the caliper pistons. It 'could' even be enough to lock them down. Had it happen in a race car at Charlotte in the mid 90's----bad scene. I've always remembered it.
Tom

 

[Mike S]

http://www.vansairforce.com/community/showthread.php?t=40235

Lots of good info in this old thread, photos and part numbers too.

 

[jdeas]

Have you added return springs?

I can't find the thread but the parts are listed below for adding return springs to the cylinders. Worked great on my 7.
Perhaps someone else here can locate the original thread.

From McMaster Carr www.mcmaster.com/<http://www.mcmaster.com/>
(1) Pkg 6389K625 Nylon Bearing Flanged, for 3/8" Shaft Dia, 1/2" Od, 3/8" Length, Packs of 5 $1.97 Pkg
(1) Pkg 9657K115 Steel Compression Spring Zinc-Plated Spring-Tempered, 3" L, 1/2" Od, .047" Dia, Packs of 12 $5.29 Pkg
(4) Ea. 9946K13 Aluminum Set Screw Shaft Collar 3/8" Bore, 3/4" Outside Diameter, 3/8" Width $1.82 EA.