Aeromarine collet style coupler. brass insert keeps breaking

[wicked1]

I am running genesis with 3/16 upgrade flex shaft and 42mm cnc 3 blade prop.The brass insert keeps breaking inside the collet style coupler , any clues to why this is

[tlandauer]

Welcome!
While I prefer not to say anything w/o first hand experience as much as possible, I have been around long enough to remember people having trouble one way or another with this type, the majority issues were stuck brass inserts and having trouble to loosen it to take the cable out. It seems the idea is good but the real world experience differs a bit. Are you inserting it the right way? the cone should face rearward, contrary to what one thinks.collets_01_zwxh.jpg
The advice that I remember from reading is to use an Octura style collet ( TFL Stainless Steel OK too) if one is having trouble.

[nata2run]

MBP collets never had any issues. Worth the extra $$

[kevinpratt823]

I had trouble breaking them originally because I kept bending the tabs out, as the Shaft wouldn't come out easily once the brass molded to the flex. I started loosening it a bit, and spinning/unthreading the flex in and out once it was loose and haven't broken one since. Sometimes you have to take the collet nut all the way off and carefully wiggle the insert with a pair of needle nose pliers to free it up.

[tlandauer]

MBP collets never had any issues. Worth the extra $$

Agreed! If the measurement fits and also VERY IMPORTANT, this collet prefers a motor shaft that HAS NO FLAT SPOT.
If you have a flat side, it has to be less than 15% of the shaft diameter, otherwise it will not have enough grab of the shaft .
http://www.offshoreelectrics.com/pro...?prod=mbp-1000

[kevinpratt823]

The MBP collet are great. IME, they do also form to the shaft, which requires the same spinning/threading in/out.

[wicked1]

I do have the cone facing the rear of the boat, they break when I run 5s Lipo in the middle of the pond. Thank god I keep my fishing pole with me to get boat back... lol

[kevinpratt823]

Wow, never had them break while running. How much of a gap do you have at the drive dog? Or maybe you're tightening too much, or not enough......? Odd.

[wicked1]

the gap was 2mm at the drive dog . just added 2nd spacer to make it 4mm hoping that may fix the problem. runs fine on 4s ,when i go to 5s it breaks

[kevinpratt823]

the gap was 2mm at the drive dog . just added 2nd spacer to make it 4mm hoping that may fix the problem. runs fine on 4s ,when i go to 5s it breaks

What do you mean you're adding spacers. Can you show us a pic of your rear end at the drive dog?
If you have a one piece flex, as in it is all one assembly and it doesn't come apart from the shaft, then you need to run a gap about equal to the thickness of the flex, from the drive dog to the strut to allow for the flex to shrink under load,(because the flex is wound like a spring). In your case, you need to allow the flex enough room to shorten(under load) about 3/16", or 4.75mm.

[wicked1]

heres the pic,the spacer is a o rubber ring to keep drive dog from rubbing on the strut. the stock set up had a teflon spacer20150521_205503.jpg20150419_141333.jpg. i will remove them asap and see if thats the problem

[ray schrauwen]

I can see some issues. Instead of using rubber o-rings, try nothing and leave a 3/16" gap between the drive dog and the strut.

This will help your driveline but, may do nothing to stop the brass from breaking.

I use anti-seize on the inner threads of the nut for the coupler.

Frankly I prefer a H&M collet but, that's just me. The MBP's are great but, too big for any of my applications.

[wicked1]

Thanks for the tips
thats what i'll try when i take it out on sunday. i'll post on how it works out.

[wicked1]

Just put the boat back together without spacer and ran it for 30 seconds on the bench with the 3/16 space between drive dog and strut. wow it moved in 1/2 the distance forward.
thanks again for your help, and hopefully this will be the end of it.

[tlandauer]

This is strange, I always thought the shrinkage occurs while the cable is wound up by the torque of the motor, when you stop the boat, the gap should remain the same as you have left it before the run.