Brass liner resistance

[Outboard]

I replaced the standard Teflon liner with a 3/16 brass tube and slowly bent it to shape.
The flex shaft is greased and installed but i do find some resistance, the shaft is snug in the brass tubing. will it "break in" and loosen up you think?
FLEX.JPG

[TheShaddix]

more than likely the reason for this snugness is from the kinks created at the bends. How did you bend it into shape? Did you heat it up first? Did you use those spring inserts to prevent kinks? This is a very extreme angle for a flex cable, so some resistance will be there no matter what, but it would not be an issue under load. It will break in a bit for sure, but it also causes a lot of heat and extra resistance for your motor. Add some oil in there too every time you run your boat.

[Outboard]

I used a pipe bending tool that properly seat the pipe. so it doesn't give a chance to bend. I am certain no kinks have been made when bent. I am using grim racer grease, maybe i should mix in some thinner viscosity oil?

[785boats]

Perhaps you might try the next size up with the brass tube 7/32".
What size is the shaft?

[Outboard]

I did give that a thought but the tube wont fit into the outboard casing. 7/32 tube will be too big externally.
Diameter of flex shaft: 4mm (0.16")

[TheShaddix]

There will be some kinks if you didn't heat up the tube beforehand, even with a pipe bending tool, and especially with that extreme of a bend. Since you didn't answer my question whether or not you heated it first, I am assuming you did not, and that's the reason. But if you did, then it could also be caused by not uniformly bending it with your tool, meaning you hold it in one spot too long when bending instead of sliding it constantly along the length. If you post an upclose pic of the tube, maybe we can see the problem. The main issue with a pipe bending tool is that it can deform the tube diameter without you even realizing it since you cannot see the inside of it anymore due to the bend. So it presses on your flex and causes resistance. I don't use any tools due to this reason alone. I simply bend the tube using a flexible object like a steel ruler, so there is no too much pressure at any given point and it's spread uniformly.

[martin]

Im afraid 3/16" o/d tube is simply to small to run a 4mm (.158" ) flex in, even a .150 flex should use 7/32" o/d tube.

[Fluid]

With care and a little practice hobby-grade tubing can be bent easily without any time-wasting "annealing" or "filling with sand". I used to bend 1/8" brass and aluminum tubing by hand into cooling coils to fit snugly around an 05 motor - no kinks. Today I bend my 1/4" stuffing tubes by hand - no kinks. The secret is to start with a piece of brass somewhat longer than needed so that your hands have something to hold beyond the area which needs to be bent. That and going slowly, working from one end of the bend to the other. Extreme bends may take two passes to complete.

Or you can go ahead with annealing (which softens brass tubing, accelerating wear) and filling with sand, or buying tubing benders.



.

[martin]

3/16" o/d tube is .160" bore before any bending or distortion or closing down of the bore, 4mm flex is .158". 2 thou clearance is where your problem lies.

[Outboard]

Sorry about that, I DID NOT HEAT the tube. as it bent very easy and the tool used hugs the sides of tube.

[Outboard]

Im afraid 3/16" o/d tube is simply to small to run a 4mm (.158" ) flex in, even a .150 flex should use 7/32" o/d tube.

I will give the 7/32" o/d tube a go but I am sure it wont fit into the outboard casting

[Outboard]

3/16" o/d tube is .160" bore before any bending or distortion or closing down of the bore, 4mm flex is .158". 2 thou clearance is where your problem lies.

Thanks, Down under in AUS we use metric measurements so sometimes ordering online is hard till you actually have the item in your hand.

[785boats]

It looks like there's enough space in the groove of the leg to fit the 7/32 tube. That's why I suggested it.. As long as it is a nice even bend.
As Fluid said, nice even pressure with a piece of tube longer than you need. And make a few passes along it. It's easy to bend tube with just your thumbs & fingers.
I sometimes put the liner & the flex in the tube, or just the next size up flex if you have any. It acts as a sort of a bending spring if it is a snug fit.

[Outboard]

Ok sounds like a plan guys ill have a look tonight, i'm not using a Teflon liner it will just be cable and brass tube.

[dasboata]

3/16 ID for a 3/16 shaft will be too tight look into a KB lead Teflon liner or as suggested go up in size !!!