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Throttle friction lock

schaplerrh

Well Known Member
Sponsor
The throttle in my RV 7 will creep back to about 15" MP unless I have the friction lock turned tight. I've check the cable run for the cause but no joy; cable looks to be in good condition and nothing touching or binding.

I'm wondering if the [little split plastic thing] inside the friction lock body has worn to the point that it provides no friction unless and until I turn the lock tight. To my knowledge the throttle cable was purchased from VAN's as part of a build kit. The engine is an IO-360 with a MT CS prop.

1) Has anyone else experienced this problem?
2) If the problem is that the [little split plastic thing inside the lock body] needs to be replaced - I know the part must have a proper name but I don't know what it is - will I need to replace the entire throttle cable?
3) If I don't need to buy a new cable, where can I buy just the part?

Thank you in advance for all help.

Robert
RV7
 
Shamelessly bumping this to the top in hopes that one of you can answer at my questions.

Thank you in advance.

Robert
RV7
 
Since no one has jumped in, they probably haven't had the problem. Got a photo of the plastic ring, preferably in context with the shaft/nut/etc? If it's a split cone (or even made like a ferrule used in a compression fitting), you might be able to remove a bit more material from the sides of the slit, and possibly add a washer behind it so the friction lock actuator can push it tighter into its 'mate'.

Bare in mind that this is a shot in the dark. I've never had to repair one; I just sleep in hotels that are similar to but cheaper than Holiday Inns occasionally (and live in the South, where we have been known to 'improvise' a lot).

Charlie
 
Thanks Charlie. I'll snap and post a photo. I too frequent cheap hotels and often make do with whatever's available. That's the only way I can afford my toys.

Robert
 
Throttle

ACS Products in Lake Havasu City AZ is a subsidiary of Aircraft Spruce and probably the largest supplier of push pull controls. I don't know if they sell parts. I have a spare ACS throttle, I will try to remember to unscrew the lock and look at it.
 
Plastic thingy!

Had this slippage problem a while back and if I remember correctly I removed the plastic block from the cable and then reversed it on the cable (front to back) with good results.
 
After landing on Thursday the friction lock knob on my throttle cable became extremely hard to turn. Any ideas how to fix?
 
Spare plastic collet(?)

Had the same problem.
Called Spruce, described the part, ordered two.
Replaced and friction lock works again.
Sorry don't have the part number.
 
Had the same problem.
Called Spruce, described the part, ordered two.
Replaced and friction lock works again.
Sorry don't have the part number.
How did you remove the friction lock without removing or replacing the whole throttle cable?
 
How did you remove the friction lock without removing or replacing the whole throttle cable?

I recently removed mine to clean it up and got improved performance. Just pull the knob all the way out and remove the 1" dia knurled nut (counter clockwise) and you will see the plastic part wedged into a taper in the main body.

Larry
 
I recently removed mine to clean it up and got improved performance. Just pull the knob all the way out and remove the 1" dia knurled nut (counter clockwise) and you will see the plastic part wedged into a taper in the main body.

Larry
Thank you. Went to the hangar and fixed my friction lock by cleaning the threads. Smooth.
 
I've had success fixing a throttle friction that was weak even when the friction knob was screwed in hard, by wrapping the nylon bit that squeezes on the throttle cable with several wraps of PTFE Thread Tape.

You don't even need to remove the knob, just pull it out. Unscrew the friction knob fully. The nylon double-cone will slide out on the cable. Plenty of room to work.

YMMV
 
Discussion?

Dumb question? Should I expect my throttle cable to stay in place on TO without engaging the friction lock?

I thought that is what the lock was for, and yes mine backs out if the lock is not engaged. I just thought it was nice and broken in with low friction internally, i.e. a good thing.
 
Is your throttle a push-pull knob on the panel, or a throttle quadrant?

In either case, if the throttle friction is OFF, you should expect the throttle to move easily, and perhaps move aft during takeoff. (Don't you always keep your hand on the throttle during takeoff? :eek:)

If the friction is ON, the throttle should not move during takeoff.

I tend to change my throttle friction during flight: For takeoff, the friction is ON. Then off a bit until my cruise setting is set (if not full throttle), then back on for cruise. Then off again for descent and especially for landing.

My comment above about the "plumber's tape" is if your throttle friction is full ON, and the throttle is still easy to move, it means that it's likely worn out. The tape trick can fix it without buying new cables or parts.

As always, YMMV!
 
Is your throttle a push-pull knob on the panel, or a throttle quadrant?

In either case, if the throttle friction is OFF, you should expect the throttle to move easily, and perhaps move aft during takeoff. (Don't you always keep your hand on the throttle during takeoff? :eek:)


As always, YMMV!

Thanks, Pete. My (push-pull) throttle will back out as the normal friction is low, but the friction works quite well even if the application curve is steep. HOT during, but after TO (5-800') the hand is busy and fails me, albeit rarely, in keeping the friction set. I'll have to check the compression sleeve and get another JIC. Maybe that will adjust the turn/drag curve.
 
Thanks, Pete. My (push-pull) throttle will back out as the normal friction is low, but the friction works quite well even if the application curve is steep. HOT during, but after TO (5-800') the hand is busy and fails me, albeit rarely, in keeping the friction set. I'll have to check the compression sleeve and get another JIC. Maybe that will adjust the turn/drag curve.
Someone earlier in this thread said they were able to buy the part from ACS after describing what was needed. The part being the small plastic sleeve that fits over the throttle push rod.
My fix was so simple. Just unscrewed the knurled friction knob until it was free and cleaned all threads. Works now like new.
 
ACS throttle cable friction-stop part #

I just dealt with the throttle cable slip issue in my RV-7. I use the ACS throttle cable provided in the Vans FW forward kit. The symptoms were the throttle creeping back unless an unreasonable amount of force was applied to the friction lock. The fix was to replace the throttle friction-stop. This is the small, white nylon/plastic piece within the throttle cable referred to elsewhere in this thread.

The ACS friction-stop part number is A-971-A for those in future need. Its a five minute fix. The piece is split down the middle, to replace simply loosen the friction lock, pull the throttle out for access to the friction-stop and replace. The only tool required is a small flat screw driver with which to pop off the offending piece.
 
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