Question

[MikeMischnick]

Hi everyone, I have a question. All of us who race model boats use flex shafts as part of our drivetrain. We have all obviously had to trim the shafts to get the proper length of shaft for our boat. Here is my question how far from the tip of the drive shaft should you apply silver solder? Should I use Silver solder or 60/40 solder? I have just recently been told but you should never ever Silver solder end of your flex shaft because you will mess up the shaft. I am confused. What do y'all think?

Mike

 

[Hydro Junkie]

Hi everyone, I have a question. All of us who race model boats use flex shafts as part of our drivetrain. We have all obviously had to trim the shafts to get the proper length of shaft for our boat. Here is my question:

1)  how far from the tip of the drive shaft should you apply silver solder?  Depends on which end of the cable and what kind of set up you're using.  On the prop end of the shaft, if you're using a ferrule, you would need the solder to extend past the end of the ferrule

2)  Should I use Silver solder or 60/40 solder? Always use silver solder or weld on the stub shaft

I have just recently been told but you should never ever Silver solder end of your flex shaft because you will mess up the shaft. I am confused. What do y'all think?  That statement can be confusing.  If you're talking about at the engine end, where it is clamped in a collet, then no, you don't want to solder the shaft.  At the prop end, you need to either silver solder to a ferrule or weld the flex shaft to a stub shaft if you want to get it to work with the strut and prop.

Mike

I hope you don't mind but I divided your post up and answered accordingly.  Others may have different ideas on how to answer this as well

 

[Marty Davis]

I ALWAYS use "StayBrite" solder on all my shafts after cutting to length.  I usually solder the first 3/4" of the shaft after using the acid to clean.  Don't try to solder a shaft that has been run and has grease in it.  After I add the solder, while it is still hot enough to flow, I wipe the shaft with a rag or paper towel to remove most of the solder.  It will look bright and shiny after wiping.  Quench immediately.  Clean the acid off with Brake Clean or similar and add the grease or WD40 type to keep from rusting.

 

[Terry Keeley]

I let just a bit of 45% solver brazing solder wick into the end to hold the inner and outer cables together. Working for 30 years!

 

[Grimracer]

Mike.. YOU WANT TO SOLDER THAT!.

You want to connect the inner lays with the outer.. thats the reason for adding solder. Silver solder is fine.

Grim

 

[dr gary turner]

No soder

The lans need to be able to move against each other especially if the FLEX SHAFT is making a bend coming out of the bottom of the boat

If running the flex shaft straight soder it and make it a straight shaft

 

[Jim Allen]

The heat sink shown allows 1/8" of the cable's end to be silver soldered without annealing the cable. I move the same heat sink & then solder for approximately a 1.250" length, the entire end of the cable, making it a solid, without annealing it. A very clean cable, inside & outside with the correct fluxes makes this easily possible. The precision hardened collet can be clamped on .750" of the solid area without any damage to the cable or the collet. I have used cables prepared this way without any problems. In fact I run them so long the round wire becomes flat on the outside. This is when the cable runs the best without heat generated friction.

Jim Allen 

 

[johnsteltzer]

You should never solider the motor end of the FLEX SHAFT the flex SHAft has to move internally and externally that is why it is made the way it is by solider it you are looking the SHAft to gether it's now not going to flex properly when the prop loads the SHAft it like a shock absorber when you solider the SHAft end it's like a solid shaft that's probably why the outboard shafts don't last long because they stamp both ends square and the SHAft can't flex like was intended to think about it 

 

[Jim Allen]

You should never solider the motor end of the FLEX SHAFT the flex SHAft has to move internally and externally that is why it is made the way it is by solider it you are looking the SHAft to gether it's now not going to flex properly when the prop loads the SHAft it like a shock absorber when you solider the SHAft end it's like a solid shaft that's probably why the outboard shafts don't last long because they stamp both ends square and the SHAft can't flex like was intended to think about it 

I disagree. The shaft in the outboard PTO is floating with both ends squared. Remove the teflon tube, replace it with a hard brass tube & a grease fitting. Run & forget about it!

JA

 

[Grimracer]

A cable failure in this case would be a disaster.

Both my EC-145 and my Bell 212 have cable drive tails on them.. if one of those fails I loose the machine.. 

SO.. the key as we know is at least ONE end needs to be allowed to move (Slide in and out of the drive)..  nothing new here.. Soldering the ends came from having the outer lay rotate over the inner causing the tail of the heli to cycle back and fourth. The flex in the cable is best kept between the ends. So if the cable has a slight bend or a S bend the lay movement happens within the entire length of the cable.

The nice thing is the cable has a VERY consistent feel to it in rotation.

4 years now on the EC-145 and no issues.. the cable spins quite a bit lower then our boats (about 8K) but only comes in and out of the machine a few times a year for inspection and maintenance. The load on the cable however is quite high!

From what I have learned.. I will forever solder my cables!

Choose your weapon!

Grim

 

[Grimracer]

You should never solider the motor end of the FLEX SHAFT the flex SHAft has to move internally and externally that is why it is made the way it is by solider it you are looking the SHAft to gether it's now not going to flex properly when the prop loads the SHAft it like a shock absorber when you solider the SHAft end it's like a solid shaft that's probably why the outboard shafts don't last long because they stamp both ends square and the SHAft can't flex like was intended to think about it 

My understanding they fail because they have been work hardened..  I have seen cables break in the middle but every time thats happen its been on a VERY high RPM system. Also.. most of the OB cables I have broke or seen broke have to do more with boat setup then the cable end preparation.

Results my vary....

Grim