Flex shaft coming loose

[Praxis]

I need some help guys. I have a 5mm motor shaft and a 4mm flex cable. The adapter I have is new. I screw it down tight with two wrenches. Boat runs fine for a while and then loses power and I hear the motor running, but I'm getting no thrust. I pull the boat back in, and the flex shaft is turning inside the adapter..... and the adapter is still tight. What do I do?

[mtbenjamin77]

do you use a two piece collet or a three piece collet? If a two piece replace the collet. if a three piece replace the brass insert with the correct size and good as new.
Two piece collet.......
http://www.offshoreelectrics.com/pro...ct-ocfhe5mm15S
Three Piece Collet.......
http://www.offshoreelectrics.com/pro...d=aero-coupler

[Rumdog]

Sounds like he's using a coupler, and not a flex hex collet. Get a collet. Works much better than a couple set screws.

[Praxis]

Two piece. Exactly like this, but 5-to-4. http://www.hobbyking.com/hobbyking/s...exi_Shaft.html

Do you think I would be better off replacing it with a 3-piece?

[mtbenjamin77]

Be sure that the flex shaft isn't so worn from spinning in the collet that It cannot clamp down. If so you may have to replace the flex. I've seen that happen on a friends spartan. Be sure to verify you have the correct sizes. a standard sized shaft will not work with any metric collets. your best best is just replace both the flex and the collet and be sure to get the right size of both

[Praxis]

Here is where I am confused... this was the maiden run on all of these parts. When I got these parts, I was careful to make sure that I ordered a 4mm flex and a 4mm adapter.

If I'm replacing flex and collet, what do you folks recommend (keeping in mind I have a bit more 4mm hardware than I want to replace, so I'd like to keep the same size)?

[mtbenjamin77]

maiden run where did you get the boat and what model is it? if you're in the USA you want to use the 3/16 shaft metric is more prevalent overseas. I use this collet.....
http://www.offshoreelectrics.com/pro...d=aero-coupler

it doesn't come loose....... ever, never, forgetdaboutit!

[Praxis]

Boat is a build. It's a 28" deep v. I'll probably use 3/16 hardware next build, but I just want to fix this one without replacing all of my running hardware. Do they make a 4mm collet for that adaptor you linked?

[mtbenjamin77]

I don't think so. It's made by aeromarinerc, an american company so no metric. your mainly gonna find metrics from overseas suppliers/manuf.

[Praxis]

Dang. Any thoughts on wrapping the shaft or loctiting it or something along those lines?

[tlandauer]

First of all, is there any damage to your flex cable? if its strands are becoming unwound, you need to replace it. When the motor is spinning, there was ALOT of heat build up, happened to me once and there was smoke because the grease I used was being cooked. The steel wires might have weakened.
Don't know this particular collet, it looks like a 2-piece unit. So no brass insert to worry, let's assume this collet is machined properly, i.e. when you tighten it and it clamps down to a thearitical 4mm, and your cable is at its claimed diameter, you can try using this product:http://www.permatex.com/products/Aut...ubricant_a.htm , only get the 1 oz tube. They sell it at PepBoys Auto store.
I learned this trick from OSE member "FLUID".
This stuff really lubricates and allows any moving parts to move further without binding and potential damage. You need only a small amount on the threads. I use this all the time after that experience.
Goodluck!

[Praxis]

No really obvious damage to flex cable. I'm planning to replace it in case the cable was damaged/weakened though. I'll order some and see if it will clamp down further. I'm not sure if the cable or collet are sized to spec or not and I don't have a way to really test them.

What do you guys think about running a wrap of Teflon tape around the end of the flex to try to get some extra grip?

[iamandrew]

Hi there Praxis
I had very similar problems with that kind of collet
I ended up getting a fine hacksaw blade, and made the gaps bigger that go around the flex shaft.
this allowed me to clamp down on it more when i tightened it .

my other advise is to upgrade the drive setup to a 3/16 because in my experience its a lot better than 4mm

[Praxis]

my other advise is to upgrade the drive setup to a 3/16 because in my experience its a lot better than 4mm

Believe me, next one will be 3/16. 4mm has been a real pain. Thanks for the advice, I'll give it a try.