I keep losing prop shafts!

[lmorsink1]

What are your guys tried and true ways for attaching the prop shaft (aft end where the prop and drive dog slide into) to the flex cable? I?m using an OSE 0.150 cable and octura 2.5? prop shafts and have just lost my 4th one.

I?ve used superglue, loctite 638, jb steel weld and soldering without much success from either.

I?ve considered the idea of too much friction in the strut causing heat and allowing the adhesive to soften and loosen but I?ve never heard of that being an issue before. I was also sure to apply liberal grease to it on the most recent run with no success.

I haven?t been running the boat hard either. I?ll roll easy into the throttle and the boat will accelerate up to about 50kph and then the motor spins up to max rpm and the boat looses thrust.

Any help or recommendations would be appreciated. It?s just that at this point I feel like I?m missing a major step and just don?t know what it could be.

[T.S.Davis]

I buy my cable and stub shafts assembled. Essentially they are braised. Someone with better equipment than I is doing that crap job. I hate doing it.

If I were trying to glue them I would use loctite 603. 603 is oil tolerant. It's nearly impossible to get all the oil out of the flex cable or the strut from manufacturing. Another trick is making sure the loctite actually gets down in there. Maybe use a needle to pop any air bubble keeping it from getting down t=into the stub shaft. Then when you put the parts together use a twisting motion so the loctite spreads around the shaft and is on all sides if you follow what I'm saying.

I've had the loctite work and I've had the loctite fail so I would still advise just buying them assembled.

[dasboata]

I buy my cable and stub shafts assembled. Essentially they are braised. Someone with better equipment than I is doing that crap job. I hate doing it.

If I were trying to glue them I would use loctite 603. 603 is oil tolerant. It's nearly impossible to get all the oil out of the flex cable or the strut from manufacturing. Another trick is making sure the loctite actually gets down in there. Maybe use a needle to pop any air bubble keeping it from getting down t=into the stub shaft. Then when you put the parts together use a twisting motion so the loctite spreads around the shaft and is on all sides if you follow what I'm saying.

I've had the loctite work and I've had the loctite fail so I would still advise just buying them assembled.

What Terry said

[lmorsink1]

Thanks for the input. I?ll try a pre-assembled one next. I have been taking precautions with getting the bubbles out and inserting while twisting, also soaking the parts in acetone to remove oils but I guess I?m just having bad luck.

[dasboata]

Thanks for the input. I?ll try a pre-assembled one next. I have been taking precautions with getting the bubbles out and inserting while twisting, also soaking the parts in acetone to remove oils but I guess I?m just having bad luck.

you need to use water proof grease when installing the shaft in the stuffing tube

[NativePaul]

I use 603 for wire drives as it is thin and needs a real tight fit to have good strength, 648 is like a thicker version of 603 that is capable of filling the bigger gaps between the strands in a flex shaft, or an oil tollerant version of 638.

"oil tolerant" doesn't mean you will have good good strength if you use it on an oily surface like the as cut end of a flex, just that it is more tolerant of small amounts of contamination, soak the end of the flex and stub shaft in acetone for a few minutes and massage both with a fine brush, than agitate in a fresh clean bath of acetone, to clean and rinse before gluing to get best results.

Loctite has a shelf life and reduces strength over time even in the shop before you buy it and open it, it will have a best before date printed on the bottom, I have had failures when I have pushed that date, and especially if you aren't keeping it in a cool dark dry place, but in a toolbox that gets left in the hot sun at races from time to time, buy small bottles and replace yearly.

When I made flexies for a shop we silver soldered them (hard brazing rods not soft solder), but that was more to do with the jig time being 30 seconds instead of 2 hours, and I don't think it is ideal where hight strength is needed due to the high heat (650-700c 1200-1300f) needed affecting the temper of the flex.

[lmorsink1]

I use 603 for wire drives as it is thin and needs a real tight fit to have good strength, 648 is like a thicker version of 603 that is capable of filling the bigger gaps between the strands in a flex shaft, or an oil tollerant version of 638.

"oil tolerant" doesn't mean you will have good good strength if you use it on an oily surface like the as cut end of a flex, just that it is more tolerant of small amounts of contamination, soak the end of the flex and stub shaft in acetone for a few minutes and massage both with a fine brush, than agitate in a fresh clean bath of acetone, to clean and rinse before gluing to get best results.

Loctite has a shelf life and reduces strength over time even in the shop before you buy it and open it, it will have a best before date printed on the bottom, I have had failures when I have pushed that date, and especially if you aren't keeping it in a cool dark dry place, but in a toolbox that gets left in the hot sun at races from time to time, buy small bottles and replace yearly.

When I made flexies for a shop we silver soldered them (hard brazing rods not soft solder), but that was more to do with the jig time being 30 seconds instead of 2 hours, and I don't think it is ideal where hight strength is needed due to the high heat (650-700c 1200-1300f) needed affecting the temper of the flex.

I feel fairly confident in my prep work. Acetone bath, cleaning with a brush, acetone again, roughed up the flex shaft with course sandpaper and the inside of the prop shaft with a needle file and acetone again to get any shavings/dust out. I can?t say for certain what the expiry date is on the loctite but I haven?t had it for long. It?s stored in a desk drawer in my house as well.

I?ve already ordered a pre-assembled one but I might pick up either 608 or 648 and try it as well.

[lmorsink1]

you need to use water proof grease when installing the shaft in the stuffing tube

I?ve been using dynamite rc marine grease. I think it?s the correct stuff?

[Silver954]

You gotta grind off the coating off the flex cable until it's shiny. Then use the loctite retaining compound. You are gluing to a coating otherwise.

[lmorsink1]

You gotta grind off the coating off the flex cable until it's shiny. Then use the loctite retaining compound. You are gluing to a coating otherwise.

I?ve just been scuffing it with sandpaper but I see what you mean and I?ll try grinding it further before I try again. Thanks.

[T.S.Davis]

I've used break cleaner to get the oil off too. Nasty stuff but it works.