Flex hex coupling

[jaso]

Hi all. Just have a question that some may have some thoughts on.

On my .21 riger I was looking at the size of the flex hex coupling and just wondering if there would be any performance gains by removing some of what seems like excess material from it by machining. The part I'm refering to is the end cap part which screws on to close the jaws.

One of the former members of my club made this for me years ago and my dad made a copy of it for my newest boat and looking at the .21 size one it seems over kill. I'm running 3/16 th cable which has served the boat well with no problems.

My question is - Will it rev harder with a trim or just rev quicker? If it's too big I quess it is the same as having a larger flywheel than needed. But will this allow any more revs or just be quicker to get there( Max RPM)

Any Ideas? :huh:

 

[Don Ferrette]

Jason, I've always used stock Aeromarine collets, unmodified. As for flywheels, keep in mind a flywheel stores energy in it's rotating mass. Too light & the boat won't launch worth a ****. Been there, done that. Too heavy & they won't rev real high. Anyone remember those heavy brass flywheels K&B used to have??

 

[_laxmasta2039]

i beat up the collet on my .21 mono trying to tighten it with wrenches, that was a KB .67 collet. may wanna leave the extra material so the collet has a longer life.

Joe

 

[Scott Schneider]

Do yourself a favor and go Square drive using .150 cables. They are lighter in weight everywhere! and drive collets can be ground to a bullet shape thats super light. And they have very little run out if any at all. On a .21 size hull the trick set up for sure. Scott

 

[Eric Perez]

Okay, so where do you get this trick .150 square cable at?

Is it square only on the engine collet side? How about the strut end, soldered or square?

 

[jaso]

I've never used square end cable and collets before.

What do people think of these and are there any performance gains?

I've heard people talking of the thrust being put on the strut rather than the engine

but does this make much difference. Does any one have any first hand example of a difference after changing to a square drive set up?

 

[Don Ferrette]

What do people think of these .....

In a word ......Yuck! But that's only my opinion.

 

[jaso]

So Don, Your running a flex hex type setups? Have you had bad experiences with square drives?

 

[Joe_Knesek]

So Don, Your running a flex hex type setups? Have you had bad experiences with square drives?

I've ran square drives in the past and personally think they are a pain in the butt. With a clamping collet, you have 3 points of failure. The collet, shaft and drive dog. With the square drive you have all the above plus the ferral, thrust washer and the other end of the shaft.

You also have to balance the ferral and it increases the rotating mass.

 

[Don Ferrette]

So Don, Your running a flex hex type setups? Have you had bad experiences with square drives?

Like I have said in previous posts I'm a firm believer in the KIS principle- Keep It Simple! A properly set up conventional collet will give worry free operation & really doesn't get any simpler set up wise. Too much b.s. to go thru with sq. drive. Now that's just my opinion, there are those who will swear by sq. drive but I tried it once & it's not for me.

 

[Scott Schneider]

Damm guys those are some serious I dont likes!! Been using Sq drives only for over 10 years and love it !! .150, .187 and .250 types with no troubles at all !!

The .150 are SQ on engine side only and cable goes inside of a 3/16" stub and is soldered in. a small piece of rubber hose keeps it in the collet at engine.

The .187's you can do 3 ways. #1 is a welded stub/cable with Sq on engine like .150's

#2 is a soldered flex ferel at prop shaft and sq at engine.

#3 is a double Sq cable that runs in a Sq frex ferel on prop shaft and a Sq collet on engine.

The .250 like #1 and #2 above.

Best thing is, NO THRUST is put on engine or bearings. All the push is on strut and that make tuning for ride attitude very precise.

If one is truely better?? whos knows for sure. many fast times and records have been set with either type. I have set 3 nationals myself with Sq drive set ups.

Have a compression collet come loose and cable not only slips it ruins cable !!

have sloppy engine bearings in engine and the forward thrust stuffs the crank into the intake rotor !! and will at times take out rod too !!

Had all this happen before switching to Sq drive. For me I will NEVER go back to compression collets and thrust on engine.

Scott

 

[Don Ferrette]

It's kinda like the PC vs. Apple/MacIntosh thing................

 

[jaso]

They are all fair comments and opinions. I think I'll stick with what I know for now as I haven't had any real troubles.

Don,took my .90 rigger out today and it's starting to get humming, I quess I'll start working with some props now. It's getting interesting to drive now with some speed. Thanks for your input with some of the problems I was having it was very helpful.

 

[Don Ferrette]

Anytime Jason, glad to help!