throttle cable

[sonex885]

Have had to replace throttle cable on Sonex N885CW while still in Phase 1 testing. Discovered that the woven throttle cable would not always feed smoothly back into the cable housing when moving the throttle quadrant back but would sometimes simply loop down between the throttle quadrant and the cable housing. Discovered this in dramatic fashion when my building buddy Tom Einhorn started up the engine with the throttle quadrant cracked open about 1/2" from the full back idle position only to have the engine fire up a very high rpms and start moving rapidly. Fortunately the apron in front of the hangar fronts onto the grass runway and Tom aimed the aircraft down the runway while he pulled out the mixture control to idle-cutoff to kill the engine. Still managed to move about a hundred feet or so before getting the engine stopped.

Ordered a new throttle cable assembly from Sonex. The good news is that they have upgraded the throttle cable to a more robust cable than the woven one being sold about a year ago when I bought my original one. The new cable is a larger diameter and appears to be unlikely to fray and kink the way the old one would. The cable housing is also a larger diameter to accommodate the more robust new cable so I needed to slightly increase the size of the hole in the firewall through which the cable assembly passes. I had requested a new set of installation instructions as I had misplaced my old ones and it appears that Sonex has also upgraded the throttle quadrants to include a hole on the inside face of the quadrant and a slotted wire retainer swivel bolt so that one can use a screw driver to hold the wire retainer swivel bolt while tightening the nut onto the cable held between the two washers on the other side of the quadrant body. Wasn't aware of these changes when ordering the new cable assembly so didn't know to order the new slotted wire retainer bolt from Sonex also. I did get from Kerry the dimensions and placement for the hole in the throttle body so I could drill the hole, but without the slotted bolt the hole does no good. The old wire swivel bolt that came with my throttle quadrant has a hole that is not quite large enough for the new larger throttle cable to pass through, so I simply drilled the hole out larger to 3/32" yesterday and installed the new throttle cable and went flying.

I have a lot more confidence in this new more robust throttle cable than in the old flimsy woven one which was not stiff enough.

Be aware however that if you want to upgrade to the newer throttle cable, and I highly recommend that you do so based on our experience with the old woven one, and if you do not have the newer style throttle quadrant with the hole in it to permit use of a screw driver to hold the wire swivel bolt in place, you may have a wire swivel bolt that will need to either be drilled out to accommodate the new larger diameter cable or you may want to purchase from Sonex at the same time a newer style wire swivel bolt with the slotted head (and get from Kerry the instructions for drilling the hole in the throttle quadrant.

Bruce Watkins
Sonex N885CW (31.3 hours in Phase 1 and counting)

[sonex1284]

Bruce, I also had a problem with my cable. I just happened to look down while doing a run up before take-off, I found my cable frayed at the throttle quadrant. There was only 1 strand remaining. I chose to replace it with a piece of solid (either left over from my trim or mixture) rather than using the braided. IMHO, it works much better and I now feel safer. I know of other pilots who've had problems with the supplied cable on one end or the other. - Mike #1284

[sonex885]

Mike, yes the braided one was too flimsy and prone to fraying and kinking. I am happy to report that the new one now being sold by Sonex appears to be the best of both worlds. In addition to being larger diameter, it seems to be both comprised of a number of twisted strands that are fused together into a more or less solid wire, so you have the strength of numbers (of strands) and the stiffness of them all being twisted and joined into a more or less solid wire. Not woven so not going to unweave and fray. I think it will be most satisfactory.

I do suggest that anyone with the old woven throttle cable either replace it or keep a very close eye on it by checking it every pre-flight for fraying, kinking, or looping.

Bruce W.

[kmacht]

When did sonex switch to a braided cable. The one that came with my throttle quadrant from sonex a number of years ago was completely solid. To hook it to the carb I had to bend one end of it into an L and hook that into the slide.

Keith

[phenry]

I am having the same problem. I talked to Kerry a while back and he explained how to mod the quadrant (which I have done) and said a new cable was going to be available sometime. Just looked on the web store and could not find it, does anybody have a part number?

[fastj22]

I tossed my stock Aerocarb cable early in my flight testing and replaced it with a solid wire bowden cable, just like my mixture control.

[Fastcapy]

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[tonyr]

I am having the same problem. I talked to Kerry a while back and he explained how to mod the quadrant (which I have done) and said a new cable was going to be available sometime. Just looked on the web store and could not find it, does anybody have a part number?

Peter,

I had some email conversations with Kerry when issues with the thinner flex cable came up, the new cable assembly is:

Part number ACV-Q01-45. The cost is about $15.00 and includes the cable and a new housing

Not in the webstore yet from my recent searches. Should able to email sales@sonexaircraft.com to order..

Cheers
Tony

[sonex885]

When did sonex switch to a braided cable. The one that came with my throttle quadrant from sonex a number of years ago was completely solid. To hook it to the carb I had to bend one end of it into an L and hook that into the slide.

Keith

Not sure when they switched, but when I purchased my throttle quadrant and cable from Sonex about a year ago the Bowden style cable had the woven or braided cable. When the cable arrived it seemed to me to be somewhat thin and flimsy, but it also seemed to move in and out of the cable housing OK so I installed it per the instructions with the throttle quadrant. The problem appears to result from the changing geometry as the lower arm of the throttle quadrant moves fore and aft and pushes and pulls the cable into and out of the cable housing. Although the bolt securing the aft end of the cable is referred to as a "swivel", once the nut is tightened down to hold the cable securely between the two washers I think that for all practical purposes the bolt does not actually swivel, so the cable tended to loop or kink. The new cable I just purchased from Sonex has, as I mentioned, a much more robust and larger diameter cable, appearing to be perhaps several strands of wire twisted (not woven) and essentially fused as one solid wire, so I don't think it will be prone to looping, kinking, or fraying like the old one. I do like the idea of a twisted set of wires instead of a single wire.

Bruce W.

[RodgerC]

Peter,
I had the same kinking issue with my cable...I spoke to Conwire in Milperra (NSW) and they made me up a 1.9mm st/steel push-pull cable...You'll also need to change the outer sheath to a push-pull type that has the "windings" oriented axially rather than in the conventional helical arrangement of a Bowden pull cable.
Rodger