Flex cable sizing

[MadProps]

yes what i am saying is if you buy a shaft from the states its most likely an Imperial Measurement size but if this shaft came from china or another country that uses Metric Measurements , its more than likely that the shafts are either metric or imperial which are different in sizes , you need 2 x vernier calipers to measure [ metric and imperial.] i had alot of issues some time ago with my gas powered hydros where i was using a u.s. made [ cc racing ] drive collet but the flex shaft came from chine and the problem was constant slippage until i did the measure and purchased an imperial flex shaft to match the imperial collet.

I am well aware of what your saying and again I can read my calipers its no challenge, they read in both imperial and metric

[rol243]

MadProps, what size cable do you have ? are they Imperial measurements or Metric measurements. both different my friend.

[Fluid]

The difference has nothing to do with how you measure them. It is instead how the maker builds them. If they are built to metric standards they may measure slightly less than Imperial standard sizes. Also, tolerances enter the picture. Chine stuff often is not held to the same tolerances which could also account for undersize cables.


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[CraigP]

They need a bunch of clearance anyway, is it an issue for anybody? If so, what are you running into? Just interested....

[Ken Haines]

Wonder if that guy needs a partner Doug........hmmmm

I was less worried about the stuffing tube and more worried about the collet. I had one that I could never get to hold. Even with solder on the end. We spun one out of an MPB collet on Ty's Q sport. Didn't lose anything that time. Checked the dia and figure, well there's the problem. Got another pair and found both to be a tic under. I don't know. Maybe we didn't crank it down enough.

Hey Terry,
Have you ever tried the Lehner Collet's ?
They work very well and have a minimal amount of run-out.
Especialy if you can find the older versions that also had a brass insert.
I can tighten them about as hard as I want with two 13mm wrenches.
I have pretty much gotten away from all the Octura couplers, even on the P-Ltd's.

[Ken Haines]

Another shaft related issue.
I have been struggling with my T-Rigger.
After spitting out too many .187 shafts over the past 2 years,
I finally took the advice from Dougie Twaits, Howard Tucker and others
to switch to .250 shafts. This was plenty of work and I took a methodical approach.
Oddly I now have what seems to be tube friction and heating while bench checking.
It seems to be on the outside portion of the tubing on the final sweep before the strut.
I did run the boat at the Michigan Cup without incident, hoping the water actual cooled that section.
My question is does anyone know of undersized 1/4" (.250) cables that I can buy ?
Also after using the standard 5/16" brass tubing I wondered if anyone had ever tried 11/32" tubing.
After close inspection it seems to me that the clearance between the standard .250 cables and the
5/16" brass tubing is tighter than when I look at my .187 setups. Conversly when I look on the bench
at possibly using the 11/32" tubing it seems too loose. Hoping somone may have an in between option
to improve this minimal clearance. Please understand that I use the .250 shafts and tubing in my
T-Mono's and other T-Rigger without a problem, but do see the clearances there a little tight too.
I may be making too much of this.....also know that I used a drill blank in the collet to center the shaft during the build,
used minimal sweeps, and did try 2 different cables (same Brand Speed Master), 2 different Lehner couplers,
and 2 different motors. I also took some advice from Tyler Girrard and lighly sanded and re-prepped both
cables with his careful advice. I use a mixture of grease and oil to also reduce the friction.
To give you an idea of what I believe I am fighting here.....it almost sounds like a shaft that has no grease or lube
at all when I bench test it at conservative RPM's. The motor swap helped a little but could not totally correct it.
I suppose maybe more run-time on this boat might help, but I know that it is not normal to have to break-in a shaft or tube.
Help !!
LOL,
Ken

[T.S.Davis]

I haven't used an Octura coupler in so long I can't remember when I last did. The coupler that TFL makes isn't bad. Think Steven sells those too. The MBP couplers are stellar in my opinion.

I've had a couple shafts now that spun in the couplers. One was with an Aeromarine coupler with the brass insert, one with the TFL coupler, and even with the MPB. On the TFL in particular, the cinch nut or what ever you call it bottomed out before the shaft was tight enough. Apparently. That's how it appeared but I really don't know that for sure. Once you spin them your hosed. You can't know for sure what happened.

Maybe the combination of the tolerance on the actual cable and the tolerance on the couplers combines to make it difficult to get tight enough. Or........I'm an idiot and simply didn't tighten them up enough.

[T.S.Davis]

Ken, my Whip with the 1/4" shaft sounds like a swarm of bumble bees with no load on it. Sometimes I wonder if I should have used teflon. I've run it for years like this and not lost a stuffing tube or a shaft. You might have to just run it and let the boat tell you if it's not right.

[longballlumber]

Couple of thoughts on Collets:

2 piece collets (i.e. Octura, MPB, and Lehner (I think)) – Can be and should be CRANKED DOWN. The threads are large enough that you shouldn’t be stripping anything. Repeating a step I learned on OSE is to use a little anti-seize on the threads. This helps a bunch!

I have run into a situation where an Octura Collet would bottom out (hard stop) before properly engaging the flex shaft. It was enough to make me think it was OK, but it ended up spinning the shaft. Thank goodness I didn’t lose the prop. In hindsight I could tell it was bottoming out. I now have a better “feel” for an Octura Collet that is fully engaged on the flex cable. I believe this was a manufacturing issue with this individual collet.

3 piece collets (Aeromarine style) – you need to be a little more careful. The problem with these, if cranked too hard, they will deform the brass insert and they start “sticking” when you try and loosen and the cable won’t release. I am not sure if it was Aeromarine or not, but you used to be able to get a stainless steel insert (in .187 size) that would solve this problem.

On flexible drive cables:
I couldn’t find any documentation to back up my theory, but I would suspect the cables identified as a nominal “3/16 cable” is actually undersized when manufactured on purpose. I would also bet the detail manufacturing drawing has the nominal diameter with a minus-minus tolerance for manufacturing. Because it’s a flexible rotating mass it’s intended to be supported by a housing in some way shape or form. Secondly because it’s a round object it’s intended to be “inserted” into other components based on its application. It’s much easier and cheaper to purchase “off the shelf” tooling and mating components if the cable is actually measured less than 3/16” (i.e. drill, reams, and tubes). In normal circumstances, I think you will find the same situation with machined dowls, pins, etc…

I did find this website… They list a 4.7mm diameter flex cable. I bet this is there 3/16” cable. They also had an interesting statement on their website about the housing size; “As a rule of thumb, the inner casing diameter should be 1/3 larger than the shaft diameter” This statement tells me the larger the cable diameter, the more clearance you need for the ID of the housing.

https://gemo.de/en/flexible-shafts/industry/flexible-shafts/

Here is another supplier - http://www.suhner-transmission-exper...le-shafts.html

Later,
Ball

[MadProps]

MadProps, what size cable do you have ? are they Imperial measurements or Metric measurements. both different my friend.

I cant continue this conversation....sorry

[CraigP]

What's the thoughts on the Etti coupler? I'm running it now, no issues at this point. I got it because the overall length was shorter... I needed some space to get an STS from Aeromarine in there...

[T.S.Davis]

Repeating a step I learned on OSE is to use a little anti-seize on the threads. This helps a bunch!

Couldn't agree more. It only takes a tiny bit to make a difference too. Don't fall for grease on the threads either. Not the same thing. Grease will move as soon as it gets warm. Anti-sieze will stay put.

I did break an MBP collet but I think it was before I was using anti-sieze.

[ray schrauwen]

Hey Terry,
Have you ever tried the Lehner Collet's ?
They work very well and have a minimal amount of run-out.
Especialy if you can find the older versions that also had a brass insert.
I can tighten them about as hard as I want with two 13mm wrenches.
I have pretty much gotten away from all the Octura couplers, even on the P-Ltd's.

Everyone overlooks H&M collets. I love them and they are similar or same as Lehner afaik??

[Ken Haines]

Everyone overlooks H&M collets. I love them and they are similar or same as Lehner afaik??

Hi Ray,
Hmmm maybe those couple original couplers which I thought were Lehner with the brass insert were H&M.
They look identical except for that insert. How do I find and even better view those H&M couplers ?
What web-site ?
Thx :)

[ray schrauwen]

Hi Ray,
Hmmm maybe those couple original couplers which I thought were Lehner with the brass insert were H&M.
They look identical except for that insert. How do I find and even better view those H&M couplers ?
What web-site ?
Thx :)

Rocket City Racing in your home state. Check out his site.

https://www.rocketcityracing.net/product-category/flex-collets/electric/

Or Hydro & Marine Germany.