Re: [Amel Yacht Owners] Steering Failure on 1992 SM72 "Aloha"


Stephen Davis
 

Hey Bill,

I did leave the autopilot completely out of the loop when testing, so that is not the issue. I found it hard to believe the incredibly robust looking steering cables could fail, but we feel like we have eliminated all other possibilities. I’m even wondering if a problem with a cable didn’t lead to premature failure of the rack. I emailed Maude Thursday to see if the cables are available, but have not heard back yet. I’m hoping Olivier may chime in on this one, as I suspect he has more insight into this system than anyone else. Liz and I could probably add a chapter to your book on SM steering rack and pinion replacement after taking it apart twice. The second time was far easier, but it was certainly frustrating to still have steering problems. 

Aloha,

Steve and Liz

On Jul 14, 2018, at 19:44, Bill Rouse brouse@... [amelyachtowners] <amelyachtowners@...> wrote:

 

Steve,

Congratulations to you, Liz, and to Amel. Wow!

I know this may sound nuts, but... I assume that you are going to have to replace the cables, but I wasn't clear if you totally eliminated the autopilot drive motor & clutch. I admit that I cannot believe the fault is anywhere but the offending cable.

Best,

CW Bill Rouse
Admiral, Texas Navy
Commander Emeritus
Amel School www.amelschool.com
720 Winnie St
Galveston Island, TX 77550
+1(832) 380-4970


On Sun, Jul 15, 2018, 04:20 flyboyscd@... [amelyachtowners] <amelyachtowners@...> wrote:
 


Seeking knowledgeable input on troubleshooting a steering issue on 1992-vintage SM.

 

Approximately 4000 nm into the 5200 nm passage from Panama to Hawaii, we experienced failure of the wheel steering system. Initial symptoms included intermittent clunking noises coming from the rack and pinion area, intermittent freezing of the steering wheel part of the way through the steering arc when turning in one direction only, but normal steering in the other direction.

 

Although we hand steered as much as possible after the initial symptoms appeared, the symptoms continued to worsen until we had complete failure of the wheel-steering system. SMs of this vintage have only a single, chain-driven rotary-drive autopilot, so we could not use the linear-drive autopilot that newer SMs are blessed with as a back-up steering system. Instead, we rigged the back-up tiller and spent the next 1200 nm out in the weather on the aft coach roof hand steering with the very responsive and robust Amel tiller system.

 

The yacht steered well with the tiller, and we were able to steer through the entire arc of the quadrant, from stop to stop, without resistance. Therefore we suspected the steering issue was unrelated to the rudder or steering quadrant. (The procedure for rigging the tiller requires that you disconnect the steering cables/rods from the quadrant.)

 

Upon landfall in Hawaii, we determined that several of the teeth had been broken out of both of the racks. Maude shipped us a new pair of racks as well as a new steering wheel shaft (the forward section of which incorporates the pinion) so we could replace our entire 26-year-old rack and pinion system.

 

We replaced both racks and the pinion using copious amounts of grease. We made sure to align the pinion in the very center of each rack with no tension on the steering rods / cables during the installation.

 

However, during a test sail, we were disappointed to find that we still have a mild, quiet thunking, primarily perceived through hands on the wheel rather than ears, while steering left using the wheel. Additionally, we are not able to steer through the full arc.

 

When turning starboard using the wheel, we can easily steer to the rudder stop. However, when steering to the port using the wheel, the quadrant arm stops about an inch prior to the rudder stop. While at the wheel, this symptom manifests as only getting 1.2 full turns of the steering wheel when steering to port,while the wheel turns 1.7 turns when turning to the starboard.

 

We feel confident these symptoms are not due to running out of teeth in either of the racks because we disassembled the brand new rack and pinion system, closely examined it, re-assembled it, and reinstalled the whole darned thing a second time to make sure we had not misaligned it. Upon examination, we were able to see that the new pinion had never rolled even close to the end teeth of either of the new racks.

 

We feel confident this symptom is not due to a problem with the rudder itself because, with the steering cables / rods disconnected from the quadrant, we are able to turn the quadrant with our bare hands through the full designed swing of the rudder from rudder stop to rudder stop in a smooth motion.

 

Another clue: We turn the wheel as far port as possible until it stops itself prematurely with the quadrant arm about an inch from the rudder stop. Next,we disconnect the steering cables / rods from the quadrant. Then, we apply significant muscle to the wheel and watch what happens to the exposed ends of the steering cables. The forward-most cable wants to continue to obey the wheel’s command and lengthen its protrusion from the cable sheath. It cannot protrude further, but you can see it trying to do so as you apply pressure to the wheel. However, the aft steering rod /cable,which should be obeying the wheel's command by shortening its protrusion, (moving more of the steering rod back into the sheath), instead refuses to move any more of the protruding rod back into the sheath. While we perform this test,if we place a hand on each of the sheaths while exerting pressure on the wheel at the far left turn position, we can feel a clunking inside of the aft steering cable sheath. We do not feel a similar clunking within the forward cable sheath.

 

Further examination of the visible portion of the steering cables didn't show any signs of wear or tear of the sheathing. The cable run from the racks through the cockpit lazarette, and takes the same smooth gentle pathway it always has. It disappears into a conduit which is glassed into the hull-side interior wall of the life raft locker and continues through a similar glassed-in conduit along the aft bathroom hull-side until finally emerging in the aft stateroom and heading beneath the bed. Beneath the bed, the cables go through a shallow, gentle curve to the spillwell devices that shepherd them through the structural stringer beneath the bed, allowing them to connect at the correct angle to the quadrant arms.

 

Further examination of the function of the misbehaving steering rod / cable while detached from the quadrant but still attached to the rack and pinion shows that,when turning the wheel to starboard,the rod appropriately lengthens, emerging from within the sheath without apparent friction. When turning the wheel left, the fully-protruding rod sucks itself back into the sheath without apparent friction until it suddenly stops a few cm short of where it should stop.

 

If the rod was broken somewhere within the sheath, totally transected, it seems that it might be able to follow the wheel’s command to protrude, but it wouldn’t then be able to follow the wheel’s command to suck itself back into the sheath. If there was some sort of kink or obstruction within the sheath, it seems we would have symptoms of friction with movement of the rod within the sheath in both directions, not just while moving the quadrant-end of the rod back into the sheath.

 

If anyone has experience with similar symptoms,or has knowledge of what is causing this very specific set of symptoms, your input would be greatly appreciated. Olivier, I hope you are reading this I suspect you have more knowledge of this system than all of us combined.

 

Thanks in advance for your input.

 

Steve and Liz Davis World Record Holders for Tiller steering an SM:)

Aloha SM72

Ko Olina, Hawaii


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