Help Please Flex shaft replacement.

[boatmanpete]

I lost the right hand flex shaft and prop on a very early outing (my own fault of course). Some time later and at huge freight expense a replacement arrived but it is 105 mm too long. I am a Newbie. Do I send it back or can it be cut and fitted. If it can be cut are there any tricks'n'tips

The boat is the Venom King of Shaves. I really loved the way it moved and I want to see it do that again.

[JIM MARCUM]

Use a dremel & a 1" 1/32 thick cut-off wheel. Don't get it too hot, quench as you go. JIM

[m4a1usr]

I lost the right hand flex shaft and prop on a very early outing (my own fault of course). Some time later and at huge freight expense a replacement arrived but it is 105 mm too long. I am a Newbie. Do I send it back or can it be cut and fitted. If it can be cut are there any tricks'n'tips

The boat is the Venom King of Shaves. I really loved the way it moved and I want to see it do that again.

Easy fix. Do you have any skills in shortening something like this? All you need is a cutting tool and some type of grinder. If you dont have a dremel tool with a cutoff wheel you can use something as crude as a pair of dykes. But your going to need to cut it long if using dykes so you can grind it down to the required length. Actually its a pretty simple in scope. What you need to end up with is the length long enough to slowly cut down in OAL with the grinder while not overheating the flex shaft and ensuring the outer sheath does not unravel as you reduce the OAL. Does that make sense? BTW. Welcome to OSE!

John

[SirBudman32]

A Dremel and a cut off wheel, no biggie. Cut a little at a time and cool between so not to weaken it.

[boatmanpete]

Jim that is a fabulous fast reply and I get your drift but as you might expect of a newbie I have a follow up question. The shaft seems to have some sort of stiffener at the core of the inboard end. When I make the cut 105 mm towards the prop end it seems as if I will have gone beyond that stiffener. Should I try to insert a new one or will I be able to retrieve the old one from the cut off piece?

Most appreciative of your input.

[boatmanpete]

John and Sir Budman, I am amazed at the way the responses are flowing in. I think I am just about on top of this already but if you think of anything which a mug might need to know please dont stop.

Best wishes to you all.

[m4a1usr]

Jim that is a fabulous fast reply and I get your drift but as you might expect of a newbie I have a follow up question. The shaft seems to have some sort of stiffener at the core of the inboard end. When I make the cut 105 mm towards the prop end it seems as if I will have gone beyond that stiffener. Should I try to insert a new one or will I be able to retrieve the old one from the cut off piece?

Most appreciative of your input.

Uh oh? A more basic question should be asked. Did you order the correct side flex? Twins typically run a left and a right hand lay flex. Dont butcher one up if its not meant for that side.

John

[dana]

If heating the cable weakens it, then how do you solder cables?

[m4a1usr]

If heating the cable weakens it, then how do you solder cables?

Cutting one usually involves some pretty concentrated amount of heat. Very localized. One would have to keep cutting for a relative long amount of time to effect a flex in some amount of strength but its sort of assumed with relative newbies that they may not know that right away. Most of us hate to see a new guy do something that they may not be well enough informed about. I guess you could call that second guessing on our part but its just a warning. Nothing more.


John

[JIM MARCUM]

Pete, the stiff section at the end of a flex drive is usually "stiffened" the last 1/2-3/4" with silver solder or epoxy to keep the strands from seperating when squezed by the collet and/or twisting between the collet & stuffing tube. On flex drives = to or larger than 3/16" I don't "stiffen" the end & I've not had a seperation problem, yet.

People who make flex drives with attached prop shaft usually use silver solder, occasionally brazing. Not sure how they do it with out de-tempering the flex shaft. But imagine they heat up the prop shaft only with a torch, let capillary attraction "suck" the solder into the shaft, while keeping the flex shaft cool by wraping it with wet cloth or water imersion.

There have been OSE threads on how do-it-yourself guys use everything from epoxy to blue locktite to attach the prop shaft to the flex shaft. I prefer a good quality epoxy for connecting prop shafts, and to stiffen the collet end of small flex drives.

Some people like using silver solder for both ends. But they must be a Hell of a lot better at soldering than me (I use a micro-torch even when soldering wiring larger than 12 gage) to not overheat the flex drive.

That's my opinion anyway. JIM

[martin]

Some of the best flexes around are brazed, if you want a .187" flex & 3/16" stub or 1/4" flex & 1/4" stub they must be brazed as the outer wind on both these type is removed & just the inner core of the flex goes into the stub hole. You put chopped up pieces of braze rod & flux into the hole then the flex goes in & the flame is concentrated on the stud & not direct on the flex, youll be suprised how hot the flex can go without affecting its temper. Re Loctite on joining you must use a retainer Loctite either 603, 638 or 648 which are all green at least they are in the UK.

[JIM MARCUM]

PS: The only times I've made 1/4" drive lines, I had a machinist friend make the SS prop shaft wiht a a .254" hole for the .250" flex shaft, turned down to .1875" at the prop end. With big boats, 5692 motors, and 70mm props I just don't trust the cut-down flex shafts. All that remains is a .1875 flex shaft where it really counts, not a full length .250". JIM

[martin]

Not so, yes you have the smaller inner core going down into the stub hole but you also have the outer wind brazed to the inner core + the braze extends along the outer wind of the flex at the butt of the stub & flex for around 1/4" - 5/16". These flexes hold up fine to gas motors turning 70mm 3 bladed props. Just about every 1/4" flex & stub is made this way.

[martin]

I should add that most of the fastest ic hydros that use .187" flex & 3/16" stub are also made this way.

[boatmanpete]

I am most grateful. I will do the deed on Saturday and let everyone know how it goes. Thanks so much.