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prkaye

Well Known Member
My carb heat cable has to have a curve it at the end because the arm travels through an arc as the door opens and closes. See pic. The bowden cable end from vans is secured by a castle nut and cotter pin. It now occurs to me that maybe I should have installed this so that the nut is not torqued down, and the cable end can rotate freely as the door opens and closes, allowing the cable to remain pointed straight.
What have others done?
 
An alternative

Phil
I heard stories of the cable breaking after a short time when using that method.

I wrapped the cable around a -4 bolt into a nut plate on the carb heat arm.
 
After all kinds of pains, here is what I ended up with.

img_5005.jpg
 
But is that bowden cable end designed to rotate freely as I decribed? Allowing it to do so is the only way i can see to get smooth travel of the arm without putting a flexing strain on the cable.
 
The bolt needs to rotate.

It does have to rotate freely. I stack mine up this way.

1) Bolt
2) Single washer for wear
3) Put through the lever
4) Washer for wear -this portion 1-4 rotates freely

5) Cable - there shoud be space between the above stack.
6)Washer - Tight against the cable. THis locks the cable in.
7)Nut - tightens up and locks 5-7.

I drill my own bolts so that I get the exact setup I want without slop.
 
In my picture, the -3 bolt is fixed solid with a nut on each side of the arm. The cable wire is wrapped around the bolt on which it rotates freely. Way better than the B-nut as far as I'm concerned.
 
prkaye said:
My carb heat cable has to have a curve it at the end because the arm travels through an arc as the door opens and closes. See pic. The bowden cable end from vans is secured by a castle nut and cotter pin. It now occurs to me that maybe I should have installed this so that the nut is not torqued down, and the cable end can rotate freely as the door opens and closes, allowing the cable to remain pointed straight.
What have others done?
Click to expand...

Phil, the elegant solution is probably the B-nut. See photo. The wire is held in place with a grub screw and the entire shaft is free to rotate....no bending or stress on the wire. Available from Aircraft Spruce. If you require extra security for your application you can thread the wire through the shaft hole and then hook the wire back on itself.

 
yes that B nut looks exactly like what i got from Vans. My initial question was whether I should torque down the castle nut, or leave it loose (cotter-pined) so its free to rotate. I have it that way now and it's working great.
 
Last edited by a moderator:
I think I have been misunderstood.

The bolt in all cases is free to rotate. Think about it some more. The lock on the cable is because the nut holds the cable in the hole drilled in the shoulder of the bolt. The bolt is free to rotate in the control arm. This allows you to adjust the cable at that the bolt. I know you can adjust your wrap with the clamp but this is just another way.

Do what ever you wish, but be careful not to wrap the cable in too tight a radius. It may break. The cable is not all that flexible and might be too brittle to take it. Careful Please! Try a test on the extra cable you cut off. I hate surprises! :eek:
 
prkaye said:
My initial question was whether I should torque down the castle nut, or leave it loose (cotter-pined) so its free to rotate. I have it that way now and it's working great.
Click to expand...
Phil,

I'm a little confused. Where would you use a castle nut on a bug nut like you have? The shaft should be smooth, not threaded, with a hold for a cotter pin. A washer (actually a spring washer and flat washer combo) and cotter pin will do the trick and allow the bug nut to rotate freely.

Do you have a picture of the other side of the installation?
 
Where would you use a castle nut on a bug nut like you have? The shaft should be smooth, not threaded, with a hold for a cotter pin.
Click to expand...

I used the hardware vans supplied with the HW WIRE NUT KIT. The hardware supplied is:

VA-181-1 wire nut (the first 1/8" of the shaft is smooth, the rest is threaded to accept the castle-nut).
AN960-10L (x3)
MS24665-132 cotter pin
AN320-3 Nut, castle shear.

Has nobody else used this kit? All I was asking is if I should torque down that castle nut. If I do, it clamps the wire nut to the arm so it cannot rotate. Based on your replies here, I have inferred that no, I should not torque down this castle-nut. So I now I have the castle nut just delicately finger-snugged with the cotter pin through it (the wire nut comes drilled for the cotter pin). This allows the wire nut (smooth portion of its shaft) to rotate freely in the control arm, and now my control cable is sitting straight and the action is smooth. The stack looks like this:
1) Wire nut (with control cable passing through a hole in the wire-nut and secured with an allen-key style screw in teh wire nut).
2) 2 AN960 washers
3) the control arm
4) 1 AN960 washer
5) castle nut and cotter pin.
 
Yes Vans thing looks identical except a portion of the shaft is threaded, so in addition to the cotter pin you can put a castle-nut (AND cotter pin). I'm surprised nobody here has used this.
 
prkaye said:
Yes Vans thing looks identical except a portion of the shaft is threaded, so in addition to the cotter pin you can put a castle-nut (AND cotter pin). I'm surprised nobody here has used this.
Click to expand...

I have used them in various places, such as the heater door and parking brake valve:

20090419_brake_valve2.jpg


It seems implicit that the nut should not be tightened all the way down.

mcb
 
It seems implicit that the nut should not be tightened all the way down.
Click to expand...

Yes, I know I can be a moron somtimes :rolleyes:
In hindsight, of course it is pretty obvious, but I didn't really notice that until I observed the control cable having to bend around as it did in my previous installation. It's working perfectly now.
 
ahhhh

I finally see why everybody was misunderstanding my question. It seems Vans has changed the parts in their HW-WIRE-KIT. I think the older wire kits contained a VA-181 Wire Nut, as this is what is shown on the plans for the FAB. The Wire kit I got contains VA-181-1 Wire Nut instead. The difference between the VA-181 and the VA-181-1 is in the smooth shaft. In the VA-181 the whole shaft is smooth and is held with a cotter pin. In the VA-181-1, the first 1/8" of the shaft is smooth and the rest is threaded to accept the AN320-3 Castle Nut, which is also contained in the kit (as well as the cotter pin which holds the castle nut onto the VA-181-1) .

I guess not everyone at Vans is aware of this change. Joe kept sending me the same diagrams, and didn't seem to understand that I was saying my wire nut was different than what was shown in the diagrams.

Anyway, problem-solved. I now know not to put that AN-320-3 too tightly on the back of the VA-181-1.
 
Captain Avgas said:
Phil, this is what a B-nut looks like.

http://www.aircraftspruce.com/catalog/appages/cablendbnut.php

It's a common termination for Bowden cables. You can see that the main shaft is restrained only by a cotter pin and is thus free to rotate.

Perhaps the device Vans has provided will do the same if you do not tighten the castle nut and rely only on the cotter pin to keep the mechanism together.
Click to expand...

Does anyone know which of these four has correct dimensions for Van's carb heat cable end?

Mine was set up with a simple drilled bolt, the Bowden cable passing through that hole, and with a nut tightened down to cinch in the cable (between washers). This didn't let it rotate, and sure enough the cable busted.

Thanks in advance!
 
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