Drive Dog Clearence

[stractor]

Please humor me as this has probably been hashed over before. Conventional wisdom says to use a space between the drive dog and the stinger of the diameter of the drive cable and let the cable push on the motor shaft with a thrust bearing to move the boat. This would seem to work fine if the cable was a good fit in the stuffing tube, but it it is not. It is a very sloppy fit. It seems to me that pushing on a thrust bearing between the dog and the stinger would work better. My reasoning is that when pushing on the end of the cable along with the twisting motion, by the prop it causes the cable to buckle because of the sloppy fit of the cable. This causes wear and in some situations tends to melt the Teflon casing. This is the first time I have used a cable drive my other boats are shaft drives, so I am new to it.
Thanks
Bob

[Basstronics]

Your right its been hashed over.

Basically it wont work.

Let me ask you this, how much will the flex cable shrink under load? Thats correct- there is no way to know. Since theres no way of knowing you cant set a thrust bearing up with proper space. The flex cable wont shrink as much at lower speeds also... So if you set this up and you have to much room then there is no benefit.

Now lets talk flipside of this. Lets say you set it up and the flex cable shrinks more than you thought. This will create excessive drag/load on the thrust bearing. This is equally no good.

On a ending note the radial ball bearings used in motors are not meant to carry thrust loads. They will take some but not a lot. Thats why people tend to use a thrust bearing between the motor and the coupler. Funny part with this is all those thrust bearings are meant for lower RPMs then most of us run.

[martin]

Yep dont waste your time thinking a thrust bearing between the dog & strut is a good idea when using a flex, however its a different story if using a wire drive where theirs no wind up ( shrinkage of the shaft ).

[LarrysDrifter]

Pervert....

[stractor]

It was a thought. I am using a ball thrust bearing between the motor and the coupler. I was wondering about what everyone describes as shrinkage. The cable the way it is made should not shrink or wind itself tighter due to torque. I agree there is "shrinkage" > My thought was that the shrinkage is due to wind up in the cable caused by loose clearances in the stuffing tube and the force of the prop trying to coil the cable into a spring like configuration, and the loose clearances letting it happen to some degree. We have a Tripple expansion Marine engine at the railroad museum I belong to and it has it's matching thrust bearing assembly. The thrust bearing is huge, consisting of a bunch of disks on a shaft pushing against oiled wear surfaces in the thrust bearing casting.

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