[Rick6a]

Are jam nuts required on the quadrant side of control cable threads? As I fit the quadrant (what a pain), all three levers can only be advanced approximately 75% of full travel because it seems the jam nuts serve as a sort of stop as they butt up against the control cable housing.

 

[Ironflight]

Rick,

I know that I have the jam nuts on, as I've been in there to replace cables in the not-to-distant past. The trick I found is that you have to have the cable housing ends as far forward as possible, or you don't get enough travel on the cable. Of course, everyone's setup is just a touch different - and they are very sensitive to minor tweaks at either end of the range. Getting full travel is one of the more frustrating tasks in setting up the -8's engine controls.

Paul

 

[Rick6a]

Thanks Paul,

I can only imagine how difficult it is to remove and replace a quadrant cable from a flying RV.

Out of sheer frustration, I removed the quadrant assembly with its three cables from the a/c, disassembled same, reassembled and reinstalled. I really don't know what I did different. Now the travel seems acceptable with the jam nuts pretty much left in the same location! One of those little unexplained bugaboos I guess. I'm sure glad I decided to do the quadrant installation before I remove the fuselage from the rotator. Even with reasonably good access, it still is a royal pain.

I'll worry about final tweaking later.

 

[Danny King]

The real problem with the travel of the RV-8 engine cables are the cable themselves. The total length of the travel of the cable is too short, therefore changing the geometry of the attachment points at the levers is futile. There is plenty of travel length there.

Like Paul said, if you maximize the lever travel, then you might just have enough travel to get full throw at the engine end. I heard that Van was going to supply new cables with more throw. I don't know the status of that.

Until then, it is necessary to drill attach points on the throttle, and mixture levers on either the carburetor, or throttle body, closer to the pivot point in order to get full throw. It is frustrating, but possible to do.

 

[N941WR]

Gang,

I don't know if this will help or not but it might.

This is from my web site:

...the clevis ends I bought from Vans did not have a deep enough throat to allow the throttle and mixture levels to travel their full distance. A quick call to Aircraft Spruce had the correct cables here in two days. If you are using a three lever quadrant, the Aircraft Spruce clevises may be too wide and you will have to modify the Vans clevises. YMMV.

One addition note, I'm using one of Dayton's throttle quadrants in my -9.

 

[dan]

Are jam nuts required on the quadrant side of control cable threads? As I fit the quadrant (what a pain), all three levers can only be advanced approximately 75% of full travel because it seems the jam nuts serve as a sort of stop as they butt up against the control cable housing.

Sounds like you got it worked out, but keep this in mind. I would not leave those jam nuts off. Some cables can rotate freely inside the sheath. I liken it to not using jam nuts on aileron pushrods. I mean...if you rig it right, there should always be enough threads engaged to prevent either end from coming loose, even if the rod manages to rotate many times...but do you want to take that risk?

 

[N908RV]

I can only imagine how difficult it is to remove and replace a quadrant cable from a flying RV.

Rick, first, been following your posts here and there and enjoying your pics of the new matched hole fuselage. Nice workmanship Rick.

Agreed, pulling these cables out of a working RV-8 are a real challenge, especially if you, like me have a rear seat throttle as well. It took all my patience and lots of strong language to get that in there without scratching anything after final painting the interior.

Those cables barely have enough throw on the throttle and mixture and not enough on the prop. You'll have to go for the high end on the prop and take whatever you can get on the low RPM range.

But, I agree with Dan, definitely want that jam nut in there - it is the only thing keeping it from rotating and loosening. Yes, in theory you have one on the other end too, but.... It's too risky and you can get to it much easier now. You'll feel much better down on the deck at 170 knots knowing that your quadrant cables are perfect.

 

[Ironflight]

Those cables barely have enough throw on the throttle and mixture and not enough on the prop. You'll have to go for the high end on the prop and take whatever you can get on the low RPM range.

Hmmm....that's interesting Rob - for me, the prop had plenty of throw, the Throttle had just SLIGHTLY more than I needed, and the mixture, well....I wish I had just a little more when it comes time to do an "idle cut-off" at high altitude airports.....

There are enough different engines out there...that's probably the difference.

Paul

 

[Rick6a]

Jam it!

Thanks guys. My better sense told me to leave the jam nuts installed. It is encouraging to hear others have experienced similiar frustrations setting up the quadrant. Thanks to your valuable input, I have to conclude that if you work at it long enough, all can be made to work....eventually.

 

[tonyjohnson]

sequence

I am approaching that part of the build but not there just yet. I want to plan it so that I don't end up with a problem that I could have avoided with a littel forethought.

It seems a little like a chicken and egg situation. If you install the cables before you install the engine, it is easier to get to the cable areas it would seem, however you are betting on the cables being of the appropriate length and fit. If not, you would have to remove them, perhaps replace them, and start again.

If you install the cables after the engine is in place, it might be more difficult. I do not know that of course, having no yet done it.

I am using a Superior IO-360 vertical draft engine with a precision fuel injection system. I have heard that presents a problem in itself, since there is some issue with the throttle cable fit unless you have one specifically designed for an RV (I don't). Vans was working on that issue a couple of years ago. I am also using Dayton Murdocks quadrant and a fixed pitch prop.

Do any of you have any observations or advise to offer as to when to install the cables and how to know if I have the correct length cables? I would like to figure that out before I start installing them.

Thanks in advance