cable for parking brake?

alpinelakespilot2000 · #1 12-03-2006, 01:50 PM

In the FWF kit Van's includes two CT-A-740 black push-pull cables http://www.vansaircraft.com/cgi-bin/...product=bowden, which I assume are for the carb heat and cabin heat. I'm going down on Tuesday to pick up my finish and fwf kits: should I pick up a third one for my parking brake or does the brake require a different type/length of cable?
Thanks.

mark manda · #2 12-03-2006, 03:53 PM

that's what I did-- you will need to cut it to fit.

carefully, with a cut off wheel on the dremel. IMHO

edit-- I watched a friend cut one with a med. sized file the other day.

Andy Hill · #3 12-03-2006, 07:53 PM

I would think a Park Brake handle using a CT 740 cable somewhat "unusual"? These cables have some friction in them, but not enough to hold a "spring", nor "lock" in place.

The "other" catalogues will detail "T Handle" cables you can buy that twist and lock - and we've then used a spring to release (and hold off) the Park Brake valve until the T Handle us pulled and twisted. Somewhat more conventional I would think? And maybe safer...?

N941WR · #4 12-03-2006, 08:17 PM

Check out this picture the parking brake is just to the left of the airspeed. To set the brakes you apply pressure and then pull and twist the tee handle.

If you go to this page and scroll down to the 10/24/06 entry, you will see how the other end is connected to the parking brake.

There are many ways to install your parking brake and if you do a search, you will find a good thread covering this topic.

Captain Avgas · #5 12-04-2006, 04:12 AM

Quote:

Originally Posted by Andy Hill

The "other" catalogues will detail "T Handle" cables you can buy that twist and lock - and we've then used a spring to release (and hold off) the Park Brake valve until the T Handle us pulled and twisted. Somewhat more conventional I would think? And maybe safer...?

Do you have a part number and specific supplier for the T-handle product that you used. It sounds like the correct thing to me but I'm struggling to find it in the ACS catalogue.

Andy Hill · #6 12-04-2006, 07:58 AM

Wick's: http://www.wicksaircraft.com/catalog...513/index.html US$46

We used LAS in the UK:http://www.lasaero.com/las/55?id=35 ?14

HTH?

Davepar · #7 12-04-2006, 10:33 AM

I don't have the part number in front me that I used, but this page looks right:
http://www.aircraftspruce.com/catalo...ledashctrl.php

Bob Brown · #8 12-04-2006, 11:27 AM

My experience with the Matco valve is that the lever arm moves freely and easily throughout its range. Brake on is one position, brake off is the other. There's no spring force you're pulling against to close or open the valve, so a simple friction detent cable, such as you might use for the heater or alternate air setup will work fine. I bought the locking T type cable from ACS, but decided not to install it as it seemed like overkill for such a simple application and it's kinda big and ugly IMHO. I elected to install the basic detent stop cable and it works perfectly.

alpinelakespilot2000 · #9 12-04-2006, 11:31 AM

FWIW, just talked to Scott at Van's while I was ordering my FWF kit. The standard recommendation is (that if you need a cable at all, depending on where it's located, of course) just one of the regular carb heat/cabin heat cables will do. The detent is more than sufficient for the type of parking brake they sell.

Captain Avgas · #10 12-04-2006, 08:19 PM

This is an interesting thread and reveals the true value of the internet for plane builders.

I would imagine that the worst scenario for the park brake is that it swung into the valve closed position in flight unknown to the pilot. There is virtually zero resistance on the Matco arm from the valve open to valve closed position. It's not highly likely that the brake could end up in the valve closed position...but it is possible that it could be knocked. And the ramifications could be catastrophic. It is my understanding that with the Matco sytem it is possible to pressurize the brake system AFTER the valve has been locked in the closed position. In other words if you land with the brake in the valve closed position and apply one brake pedal as you land that brake will stay pressurized in the locked postion after you remove brake pedal pressure. It doesn't take much imagination to see where that would be going.

So I fancy the idea of installing a spring such that if the cable fails the valve arm is always pulled to the valve open (brake off) position. That is then failsafe...but I think having a spring would necessitate having the lockable T-handle rather than the detente knob type. Otherwise if the detente slips while the plane is parked (and I find that detente type knobs DO tend to slip with age) then the spring will pull the brake to the off position.

Anyone have any further thoughts on this. My gut feeling is that the threat of the valve coming on in flight is much more dangerous than the valve coming off while parked.