What's your take on carbon fiber shaft for a solid shaft?

[MassiveOverkill]

If you glue a piece of carbon rod (solid or hollow) to a short piece of steel or brass tube to act as solid bearing indside of a stuffing tube with a short piece of flex cable for alignment, and the other end of the carbon rod is glued inside the prop shaft stub (diameter of stub fits in stuffing tube),making sure non of the carbon rod abrades against anything, do you think the carbon rod will hold up to the stress and water\lubricant?

[NativePaul]

If you lose the short flex shaft and rely on good alignment for alignment, ditch the brass tube bearing for a ball bearing (most carbon you can buy doesn't like heat) it will work OK and withstand water and lubricant as long as it has no solvent in the lube, stress is another matter though, how much power are you wanting to put through it? Size for size it is much weaker than piano wire, much lighter too, but what percentage of the total build is the wire weight, IMO you would have to be looking at an exceptionally light boat with very limited power for it to be worth it.

[MassiveOverkill]

Paul, it's easier to refer you to my other threads:

http://forums.offshoreelectrics.com/showthread.php?34816-Joysway-transmitter-protocol

http://forums.offshoreelectrics.com/showthread.php?35110-Seaking-120A-ESC-what-should-my-timing-be

I need to lighten my reciprocating mass or go with a new motor\motor mount. The only thing the carbon rod would be turning other than itself, is the mass of the prop assembly.

I have everything I need to make the new driveshaft prototype.

[MassiveOverkill]

Hmmmm....

http://www.southriverrcboats.com/shop/article_ET-H31/ETTI-2mm-CF-Drive-Shaft-1_8-prop-shaft.html?sessid=E9FM6f4Wru1VQmgRu3BqVhGB8fYzjObS 80ziwYL9tSAjzyPl4Je8OCOqsEbdZeZY&shop_param=cid%3D27%26aid%3DET-H31%26

[martin]

If you want less reciprotating mass & less friction go with wire drives, i have the Etti ones in some boats. But also custom make them for other boats down to .062". You can get collet couplings in .062" .078" & 2mm. If you need somethig custom re stub size & wire diam Jeff Wohlt on this forum makes nice shafts & couplings with set screws if you dont want collet couplings,

[NativePaul]

The ETTI unit you linked to is a standard piano wire shaft, only the "stuffing tube" or whatever you call it when it doesn't actually penetrate the hull, is a carbon tube as opposed to the usual brass or alloy.

.078" and 2mm collets are interchangable, they are easily close enough that you can use whichever collet is more easily available, better quality or cheaper. There is only 0.6 thou" or 0.02mm in it, with the imperial being larger than the metric.

I doubt you have any reciprocating mass in an electric drive system, as you have seen taking your motors apart they have no crank shafts or pistons going in and out, I think what you meant is rotational mass which is the mass if all the rotating parts in your drive system. I do not believe that it is the cause of the excessive temperatures you are seeing, it only has any effect if you are accelerating or decelerating it, if you are running at full throttle in flat water it will make no difference at all and even in the worts case of constantly accelerating and decelerating in rough water where the prop is loading and unloading, the low moment arm of the shaft compared to the motor's rotating can means it is a negligible effect. what can have big effects are vibrations from out of balance components, rotational drag of the shaft/stub separate from the drag caused by vibrations, the size of the prop, and the timing of your motor.

Epoxy putty is often used for balancing motors, outrunners are easy, as long as you put the putty on the inside of the rotating bell the centrifugal force from spinning will try to stick it on further rather than fling it off, not only the balance of couplers is important but if there is any eccentricity it will whip the shaft around and cause large amounts of drag.

No flexible shafts like to run straight, a flex shaft will whip if run straight and will actually have less drag if a small curve is present, a wire drive will be better but will require at least 1 central bearing to prevent it whipping. if you have increased the diameter of the flex shaft this will increase drag not only from the greater frictional losses within the shaft, (more strands rubbing against each other) but from the higher speed of the surface, and if you went from a teflon liner to no teflon and a greased shaft to use the same stuffing tube, the grease will have increased the drag too.

Going from a 30mm prop to a 32mm prop will make a large increase in amp draw, this will heat things up massively compared to any difference in rotational mass ever would.

Outrunners like a lot of timing, despite being told this in the second thread you liked to you said you are running low timing to keep the heat under control, but by running at low timing you are running less efficiently than you could and thus increasing temperatures needlessly.

[martin]

Hi Paul re the .078" & 2mm i listed was more to do with whatever couplings are available as the Octura is spec as .078" & the Etti is spec at 2mm so as to buy the right coupling for this size wire. Regards Martin.

[MassiveOverkill]

Yep, I meant rotational mass. The reason why I feel that it's a big deal in my situation is because of the size of the motor, which is small compared to other brushless motors. I've also seen huge differences in my micro helis where 2 grams difference in weight between the the heli's stock steel shaft, and the carbon fiber replacement.

The weight of my new Octura flex is about double the weight of stock even though my new setup spins very freely. I went back to the 30mm prop but the overheating persisted.

I did make some progress though. I've elminated alot of vibration and possibly some friction.

If you look at this picture, the magnets are out of magnetic alignment with the coils:

http://img.photobucket.com/albums/v632/MassiveOverkill/SuperMonoX/f6ca025b.jpg

Here is how the alignment should look:

http://img.photobucket.com/albums/v632/MassiveOverkill/SuperMonoX/73fb09a3.jpg

The reason why is Joysway installed a brass bushing:

http://img.photobucket.com/albums/v632/MassiveOverkill/SuperMonoX/74b8470c.jpg

http://img.photobucket.com/albums/v632/MassiveOverkill/SuperMonoX/3eeece2c.jpg

With this bushing in place, the motor is loaded aginst the rear bearing because the magnetic force is pulling it against that brass bushing so I machined the inside of the can an equal width of the bushing. Here's a side-by-side of machined housing vs stock CF2812:

http://img.photobucket.com/albums/v632/MassiveOverkill/SuperMonoX/af7e5bb2.jpg

My alignment is now back and the housing now floats when inserted into the core. Running the motor freely is very smooth now. Running the motor in the boat has little vibration (just a very minor buzz at a certain point in the RPM range). I'm anxious to take her out tommorrow and see if she'll overheat. The other thing is that with the magnets now being aligned with the core, I should get more power out of her in addition to eliminating the bearing loading since the motor is now free-floating.

Another good point you all make is the way I drive her.............because the new setup, I was only going part throttle and doing short bursts of speed vs doing WOT runs like in my video. This probably created the most heat, but it's hard to get away from that natural instinct you have inherited from going easy on internal combustion engines and not just running them WOT. The other reason why I did it was because I wanted to keep the boat close to shore in case things went bad and I had to rescue her.

Back to timing. This isn't your 14 pole outrunner, it's an 8 pole. I should follow ESC timng appropriately for an 8 pole? No matter what timing I run her at she screams and moves fast.........speed isn't an issue. If running her at 0 degrees advance isn't going to hurt either the ESC or motor, I'm fine with running it.

I'm not going to run grease. I tried that initially until I turned the prop by hand and felt all the drag. I've been using a lighter viscosity lube made for control cables, and it's been staying put since the stub fits snug in the stuffing tube.

Thanks for the tips.

[m4a1usr]

Holy mackeral did this thread take a turn for the? The OP states will a CF shaft substitute for a metal one? The answer without even gleening the specifics is a resounding "NO". Not today. Not tomorrow. Unless you know of some specific material with greater rigidity then metals which are denser remember this, the question is already answered. Sorry if I sound dismissive but the original question should have been researched before posting. The applications of composites material strength is due to flexability. Not rigidity. Motor shafts should resisit force as much as possible due to design restrictions. In essence, they should not flex any amount if possible. We know thats not possible. So use a high carbon steel, which almost every motor manufacturer does.

John

[MassiveOverkill]

Holy mackeral did this thread take a turn for the? The OP states will a CF shaft substitute for a metal one? The answer without even gleening the specifics is a resounding "NO". Not today. Not tomorrow. Unless you know of some specific material with greater rigidity then metals which are denser remember this, the question is already answered. Sorry if I sound dismissive but the original question should have been researched before posting. The applications of composites material strength is due to flexability. Not rigidity. Motor shafts should resisit force as much as possible due to design restrictions. In essence, they should not flex any amount if possible. We know thats not possible. So use a high carbon steel, which almost every motor manufacturer does.

John

Please step off your high-horse. There are many applications for it: https://www.google.com/search?q=carbon+fiber+driveshaft&rls=com.microsoft:en-us&ie=UTF-8&oe=UTF-8&startIndex=&startPage=1&rlz=

Googling for RC boat or boat didn't bring up much. As I've already stated, my micro heli works just fine with a carbon fiber shaft. It's used in blades as well.

The applications of composites are due to rigidity and lightness, why do you think people are reinforcing their hulls and making them with it?

http://en.wikipedia.org/wiki/Carbon_(fiber)

"The properties of carbon fibers, such as high stiffness, high tensile strength, low weight, high chemical resistance, high temperature tolerance and low thermal expansion, make them very popular in aerospace, civil engineering, military, and motorsports, along with other competition sports"

[Cooper]

Googling for RC boat or boat didn't bring up much. As I've already stated, my micro heli works just fine with a carbon fiber shaft. It's used in blades as well.

There is a reason for this, if you ask for our opinion then you should get ff your high horse and listen! If you want to try and manufacture a cf driveshaft, then do it and let us know how it works. I have spun .78 wire drives to where you could see the metal spiral, yes stopped just in time before they broke. A lot of stress on that, had to step up to 93 wire. Only went with wire for less restance. And have and always will put grease on/in the driveline. Also helps keep water out. With wire you should regrease after every run/day. Water and high carbon steel don't mix. As for the cf, you will have to make a straight shot to the prop, cand put the lateral stress on a cylindrical cf tube. And a tube is stronger than a solid under different loads, tube will support more weight (hanging on it) but less rotational force. A solid shaft is opposite and will have more rotational strength if a slight bend is applied. Cf will not. Big difference in applications is size and weight. For what you are "wanting to do,know" cf is not the answer. In order for your cf shaft to not shatter under the forces boat drivelines apply the size would just not be practical. It can be done but why? And the resistance you are talking about?, too many other factors apply that you haven't addressed to be considered relevant . New bushings, old out of spec? Bearings? Oil lube or grease? Temperature of lubricant? Teflon liner, how much resistance from bend? Is it attached to motor? Ect... Any way it sounds like your mountain is more of a mole hill,,, and please remember many of the people here are pretty knowledgeable of boats. It's good to think outside the box, that's how a lot of improvements are made. But not this time. So your high horse is pretty much being a smart ass kid on the merry go round pestering mommy for more tickets! If you don't like the answers to your question then you are going to have a hard time and expensive time setting up your boats. Oh and don't argue with the guy you bought your motor/speed controller from saying it was defective because it burnt up. ( I think you will need some time in this sport to figure out why I said that)

[MassiveOverkill]

Googling for RC boat or boat didn't bring up much. As I've already stated, my micro heli works just fine with a carbon fiber shaft. It's used in blades as well.

There is a reason for this, if you ask for our opinion then you should get ff your high horse and listen! If you want to try and manufacture a cf driveshaft, then do it and let us know how it works. I have spun .78 wire drives to where you could see the metal spiral, yes stopped just in time before they broke. A lot of stress on that, had to step up to 93 wire. Only went with wire for less restance. And have and always will put grease on/in the driveline. Also helps keep water out. With wire you should regrease after every run/day. Water and high carbon steel don't mix. As for the cf, you will have to make a straight shot to the prop, cand put the lateral stress on a cylindrical cf tube. And a tube is stronger than a solid under different loads, tube will support more weight (hanging on it) but less rotational force. A solid shaft is opposite and will have more rotational strength if a slight bend is applied. Cf will not. Big difference in applications is size and weight. For what you are "wanting to do,know" cf is not the answer. In order for your cf shaft to not shatter under the forces boat drivelines apply the size would just not be practical. It can be done but why? And the resistance you are talking about?, too many other factors apply that you haven't addressed to be considered relevant . New bushings, old out of spec? Bearings? Oil lube or grease? Temperature of lubricant? Teflon liner, how much resistance from bend? Is it attached to motor? Ect... Any way it sounds like your mountain is more of a mole hill,,, and please remember many of the people here are pretty knowledgeable of boats. It's good to think outside the box, that's how a lot of improvements are made. But not this time. So your high horse is pretty much being a smart ass kid on the merry go round pestering mommy for more tickets! If you don't like the answers to your question then you are going to have a hard time and expensive time setting up your boats. Oh and don't argue with the guy you bought your motor/speed controller from saying it was defective because it burnt up. ( I think you will need some time in this sport to figure out why I said that)

I'm not the one on the high horse. Being on a high horse is sayng "you're beneath us for us to even entertain your question so you shouldn't even ask", which is what was done, and is what you're doing right now, putting me down simply for asking and/or not knowing. All I asked were the reason why or why it could not be done, not that I had my mind set on doing it regardless of what was recommended. You make alot of ASSumptions.

http://www.rcgroups.com/forums/showthread.php?t=1663518&page=4

"It's why I'm not complaining about a defective ESC."

And your reference to Make-a-Wake's misfortune. Do you really want to bring that up and start the mud slinging again? Let it be.

You didn't even bother to read the thread did you? There are no curves in my stuffing tube, it's a straight shaft. It only needs flex from the end of the stuffing tube to the motor.

The reason for the links in my last thread was not to imply "Look everyone else is doing it, so I'm going to do it no matter what", it was meant to show that there's all of this information showing the application of carbon fiber in these situations and that there were no red flags stating "OMG don't do this in RC boating or you'll blow your S$%t up!!", meaning my question was a valid inquiry.

Thanks for the explanation, I could have done without the prickness part. Sorry to tread on your elite group with my mundane questions. You're both models for the hobby that beginners can look up to (I hope those of you non-pricks know this comment doesn't apply to you and I appreciate all the tips and pointers). :thumbup1:

[Rumdog]

lol
again..

[Cooper]

Read what I said, do it see what happens, as to your question wasn't it asking about a driveshaft of cf? The stuffing tube could be made of glass! Yes your are right it is straight. No one questioning you on that. Yes your right a straight shot, no one questioning you on that.


If you glue a piece of carbon rod (solid or hollow) to a short piece of steel or brass tube to act as solid bearing indside of a stuffing tube with a short piece of flex cable for alignment, and the other end of the carbon rod is glued inside the prop shaft stub (diameter of stub fits in stuffing tube),making sure non of the carbon rod abrades against anything, do you think the carbon rod will hold up to the stress and water\lubricant?
That is your original question-right? And you got an answer from m1a4-right? Yes on both. And your response was- get off your high horse, go figure. And the answer I told you in my opinion which you wanted from the start of the thread, was simply no cf isn't a wise choice. Steel is better and been proven. If you want to try it then try it and let the rest of us know how it works. Hey if it works then I'll use it.

But you twisted those answers so you get what you put in, jack! Don't be a ass. No one here appreciates it, and there is a lot of very wise people here so humble yourself and learn something. Chances are someone has already had the misfortune or fortune of doing something you are thinking of and willing to share there experience. Makes the learning curve for you easier and less expensive.

But you seem like a smart guy so you must know all that. And I guess I hit the nail on the head with the last comment. And no I didn't read the thread just a simple statement.

[MassiveOverkill]

And no I didn't read the thread just a simple statement.

That's all I need to hear. Let's drop it as this no longer productive.

[Cooper]

Something to be said there about hitting the nail on the head.