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View Full Version : One more clue to my steering problem...



Lenny
05-18-2005, 10:42 AM
Does this help in finding out what might be wrong? As some of you know. steering this thing is impossible in one direction. It reverses the problem when I reverse the rotation of the prop so it is not a cable thing. As well, the cable is free and moves effortlessly on land and idling in the water.

Anyways, yesterday, when I was flying the hull in following seas I noticed a rather "disgusting trait" It will leave the water fine, fly straight etc, but on re-entry it hooks, (in this case port) violently and requires a quick flip of the wheel to set it up straight again. It is like the drive moves to some other position while the hull is un-wetted and loads up to some other angle once submerged again.

Could this be a sloppy gimbal issue?

...also, when flushing it yesterday, i noticed for the FIRST time, a "squeak"... :( It doesn't sound good. I am going to take the belt off and run it when I get the courage up and see if the rotating assembly "squeak" is the (hopefully) Alternator, crank pump etc, or.....the motor. It sounds like I am running it with no oil. It has all of those things. "Bling" to the tune of 425 Ft Lbs might be closer than I think.

MOP
05-18-2005, 12:24 PM
The steering thing is a tough one, I think there is a possibility that a fin style tab may help that at least can add some force to counter act the prop. Being equal in both directions is a puzzler, it may be in the Helmut if that is loose the drive will get floppy. You have said you do not find much looseness. Have you considered adapting late style power steering to it, It is not as hard as it sounds. Noises need to be heard or discribed very well, maybe even a sound clip.

Phil

mattyboy
05-18-2005, 12:58 PM
Lenny,


all of the problems you posted were eliminated on my boat with

1. a LH ultra prop

2. installing a rubber o ring around the helmut bolt eliminating slight play in the drive to helmut connection

post some pics of the drive and the prop

ITTLFLI
05-18-2005, 02:48 PM
Lenny,

It sounds like the prop is "walking" and taking advantage of the play in the gimbal before the boat(hull)re-enters the water. I have felt this before on a sloppy bravo set up. I don't recall if there was any slop in that gimbal or not, but I would assume so due to its age.

Formula Jr
05-18-2005, 09:16 PM
Lenny, as we spoke on the phone, to test for cable binding, you need someone to put a force on the drive, pushing it left or right, as much as they can with their leggs and back to a wall, while you turn the steering wheel. You can't test this at idle or just on the trailer by yourself. You will then note that it will be harder to over come the force of the person pushing on the drive, than it should be in one direction. The forces will not feel linear. As we know, the counter steering torque fin can only compensate completely equal in a small window.
You have an upper bushing from the Steering fork to the upper drive unit and a lower Needle Bearing from the Steering Fork to the drive unit. These are the only two places that pivot the drive, side to side.

Your last observation, that unloading the drive on a jump, lets it spring to the left or right, fits my theory of cable binding.

So here is a full explanation of the theory:
The Key to all of this is that your steering problem is completely reversable depending on the rotation of the prop. And Mattty found the last part of the puzzle here explaining that there may be creeping play in the Cable to Steering arm coupling.

We'll start from the back forward. I have to use a merc in my example, cause thats what I have. But the theory is exactly the same.

A. Your drive trim tab isn't sufficient to counter the torque force of the drive. Tabs are not linear in this opposing force and they only find a true balance of forces in a window of RPM at speed. I set mine to balance at 9/10th throttle as this is most comfortable, At WOT I expect the steering wheel to pull a little to the side. And at 7/10ths I expect it to pull slightly to the other side. The small tab offered by merc isn't large enough, to ever counter the torque force above 7/10ths so I have to use the larger older tab to find balance at 9/10ths...... I have to modify the large tab slightly to work correctly.

B. There are only two pivot points to any drive for side to side motion. Volvos have a lower needle bearing and an upper bushing which pivots the upper unit in the Steering Fork by way of the Hemet being connected to the steering arm. The steering fork only has up and down movement. If there was looseness, side to side in the Steering fork, what you would experience, is a hard jerk to the left or right at the moment the drive finds balance of the forces of the prop and the the tab. You have not expeienced this. Even if these pivot points were completely fryed, If the torque tab was doing its job, the binding would still be even no matter which rotation you spun the prop if you re-adjusted the tab accordingly.

C. The Cable to steering arm coupling could be loose or "creep" under tension. This is an important part of the puzzel as we will see later. If it "creeps" you would not experience this "flip" of forces between the drive and the Tab. If it have a lot of looseness you will feel this flip of forces and steering can be very squirrly. But a creep can set up the next event.

D. Your steering cable is a large metal rope in an inflexable sheath. The sheath has to be connected to hard points at both ends. And the metal rope cable slides and is guided by this sheath, keeping the metal rope from "blowing out" in a bend. But the Metal rope is trying to do that if you are thrusting the metal rope in this sheath against the force of the drive. This rope is not smooth and needs lubrication to move in this sheath. Thick marine grease also acts as a long bushing for the inner cable.
There are two bends in the sheath, guiding the inner cable. These are friction points. When you are pushing the inner cable Through the sheath, the friction is in the port side bends of the sheath and rope, When you are pulling the cable the friction points are on the inner starboard side of the Sheath and rope cable. As far as you know this Entire Steering cable has never been replaced or regreased. And you also don't know what the inner surface, friction surface, of the outer bends of the Sheath look like or if the inner rope cable has worn through one of the upper stands of wire and may have then frayed. Lets assume the sliding surfaces in these bends are no longer smooth and no longer have a lubricate. At idle or on the trailer, you are not pushing hard enough on the inner cable for it to dig in, ie, want to blow out, and press into the port sides of these bends.


Now lets think about what happens when you "load"-push that worn cable in the sheath. Even with alittle torque force from the drive - wanting to rotate, this is normally being countered by light pressure on the Steering wheel, you have now shoved that cable into two friction points at the bends and the harder you counter, the more the inner cable wants to bite into the sheath. If the inner cable to Steering arm, creeps; even alittle, You may not feel this binding being "set" as you increase speed. Its unnoticeable. But if you unload the drive, The inner cable will, with out steering effort, "Spring straight" and pop the drive left or right, So you now land with the drive slightly cocked setting you into a slight port or starboard roll on landing.

It will take some diagrams of the forces involved depending on how your system is configured, but find the set of forces that are pushing the inner cable in the sheath to counter the force of the drive. And check for binding.

Formula Jr
05-18-2005, 10:28 PM
So to start:
Is your pinion steering gear on top of the rack or under it?
And what direction are you spinning the prop right now?