Good high speed shaft material?

Terry Keeley wrote: ...

As noted before, that's an overall picture of your boat. None of the other pictures on the page look like a gearbox. Do you have a picture of the gearbox? And a picture of the connection between the 1/4" and 3/16" shafts?

-jiw

=================== Have you considered an alternative material such as carbon fiber reinforced tubing, possibly with adhesive bonded metal ends? Unka George (George McDuffee)

...and at the end of the fight is a tombstone white with the name of the late deceased, and the epitaph drear: ?A Fool lies here, who tried to hustle the East.?

Rudyard Kipling The Naulahka, ch. 5, heading (1892).

If I understand correctly the end that breaks has threads that are part of a collet that secures the flexible shaft. If that is right, how about making a collet that clamps on both the shaft and the flexible shaft?

Dan

Depending on where the bearings are and how heavy the prop is, I think you are close to (or more likely over) the critical speed of the 10" shaft, which may be causing it to flex, which may be what is breaking the end off your gearbox shaft.

-- Regards, Carl Ijames carl.ijames at verizon.net

Isn't a tube within a tube the best way to handle this? No whippng. Octura used to make lots of different drive systems for hydros. The guys around here (San diego) always seem to need to run the thing up to nearly full throttle and toss the whole boat into the water. That has to put incredible stress on the shaft at the weakest point. Maybe you could add some rubber isolator or clutch to soften the shock

TK,

My reference for 1144 steel (cold finished) states the following: Yp minimum: 100,000 psi TS: 125,000 psi Machineability: 83% of B1112

For 4140, heat treated and stress relieved: Yp: 120,000 psi TS: 140,000 psi Machineability of annealed 4140: 55% or B1112

Agreed that 4240 HT & SR has a slightly higher yield point, but in steels with a tensile strength of over 100 ksi this does not affect the resistance to fatigue failure (endurance limit) by much.

Consequently I stand with my statement above that if a shaft of 1144 steel failed then, other things being equal, a shaft of 4140 HT & SR will likely fail also.

The suggestion to attach the flexible shaft onto the gear box with a double-ended collet sounds eminently suitable to me and that is what I would do.

Wolfgang

Terry Keeley wrote:

Someone else can weigh in on the material choices here but I was thinking that if you had shaft ends that were made with rolled threads and no stress risers, then for the bulk of the shaft length, have a hollow shaft either pressed or welded on. If you have the hollow section with tapered profiles near the ends, you can eliminate the vibration issue should the length and speed be the source of the problem.

If I understand correctly the end that breaks has threads that ar par

flexibl

Exactly, thanks, see my post below..

Terry Keeley wrote

th

pla

As noted before, that's an overall picture of your boat None of the other pictures on the page look like a gearbox Do you have a picture of the gearbox? And a picture of th connection between the 1/4" and 3/16" shafts?

-jiw[/quote:b450b0904b

Sorry James, guess the ordering on the page has to be right for th

links to work. Think I've fixed it now, here's the gearbox again an the only pix that sorta shows the other end in the boat

If these don't work it's pix a5 & a3 respectively

The collet end that attaches the flex shaft to the gearbox is kind

heavy. Normally they thread the collet to the crankshaft of th motor on a non-gear application so I tryed to make that work as i and had to thread a jamb nut on first, then the collet, making it al just a little too much for the 1/4" shaft with threads.

As mentioned I think I'l make a collet that is attached with se

screws eliminating the threads and halving the weight hanging off th shaft

According to Terry Keeley

th

tha

With setscrews, you will have a bit more difficulty balancin the shaft -- but I'll bet that the keyway introduced enough of a imbalance at the speeds which you mentioned

If you *must* have a keyway -- can you cut *two* of them at 18

degrees -- and use two keys as well -- to maintain the balance

And another thing which *might* improve your reliability with th

threaded end of the shaft. Look into having the threads rolled instea of cut. This makes for a more rounded root of the thread, and th rolling process makes for greater strength beyond that of the stres riser problem

Good Luck

DoN

-- Email: | Voice (all times): (703

938-456 (too) near Washington D.C. --- Black Holes are where God is dividing by zer

---[/quote:e479075049

Thanks Don, I'm going to eliminate the threads completely. Didn'

think to balance the shaft but I'll try moving the location of th set screws around to get it as close as possible

I think we are not exactly in sync. I am thinking of a double ended collet, which grips the shaft on one end and the flexible shaft on the other end. No set screws used.

Another possibility would be to silver solder instead of attaching with set screws. I may be wrong, but set screws seem like one more thing to go astray.

Dan

According to Terry Keeley :

[ ... ]

Is there any *logical* way to navigate this site? I find a3 (with some difficulty), and the forward and back links skip rather unpredictably to other letters. The only thing which *might* work is to step through them all -- which is very time consuming.

Does it need JavaScript enabled? Does it require something in Windows' IE browser which I won't find on any of my systems? (I not only *don't* run IE, but I also *can't* run it on Sun Workstations. Wrong CPU. :-)

Certainly the "album=70" "pos=4" don't seem to tie to "a5" in any logical way.

Enjoy, DoN.

According to Terry Keeley

Is there any *logical* way to navigate this site? I find a (with some difficulty), and the forward and back links skip rathe unpredictably to other letters. The only thing which *might* work i t step through them all -- which is very time consuming

Does it need JavaScript enabled? Does it require something i

Windows' IE browser which I won't find on any of my systems? (I no only *don't* run IE, but I also *can't* run it on Sun Workstations Wrong CPU. :-

Certainly the "album=70" "pos=4" don't seem t

tie to "a5" i any logical way

Enjoy

DoN

-- Email: | Voice (all times): (703

938-456 (too) near Washington D.C. --- Black Holes are where God is dividing by zer

---[/quote:78500dc401

Sorry about that Don, must be some reason why it's not working fo

some, damn 'puters

Here's a link to my main page, if you go to the album titles "m

stuff" it's pix a5 & a3

Thanks for looking

If that doesn't work, here's the main page, you can find my albu under my name

Terry Keeley wrote

I think we are not exactly in sync. I am thinking of a double ende collet, which grips the shaft on one end and the flexible shaft o th other end. No set screws used

Another possibility would be to silver solder instead of attachin

wit set screws. I may be wrong, but set screws seem like one more thin t go astray

Dan[/quote:5569d352c4

It is a double ended unit, one end has a collet to attach the fle

cable to the gearbox (it needs to come out a lot for grease etc.) an the other end has to be attached after the shaft is slipped throug the bearings in the unit..

If you want to gild the lily, make your new shaft from VascoMax C-300 or C-350 (Teledyne Vasco). These materials have high yield, tensile, toughness, ductility and impact strengths, as well as high fatigue and compressive strengths. Could be your breaking problems will come to an end.

It will require heat treatment, but VascoMax requires temperature no higher than about 925 degrees F for several hours to achieve maximum strength.. Distortion is limited or eliminated, and shrinkage is predictable.

Harold

3 HP at 20K RPM is only a bit less than 10 lbf-in of torque. With 1/4" of "grab" length on a 1/4" dia shaft, shear at the interface is less than 400 lbf/in^2. Neither of these should be any problem at all for a steel shaft. It therefore seems to me that your failure is due to vibration fatigue with the shaft "whipping" when rotating at speed, 20K flexures per minute. I would think that balancing, suppression of resonances and intermediate support would be the way to fix that.

Yep - Java - suggest you download Mozilla for a zun - and it uses SUN Java.

International Waters Community - My Stuff/k2 - TF2 soon to be TF1!

Martin

Martin H. Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net NRA LOH & Endowment Member NRA Second Amendment Task Force Charter Founder IHMSA and NRA Metallic Silhouette maker & member

Terry Keeley wrote:

According to Martin H. Eastburn :

Not according to the quoted html below. It uses JavaScript, which is *not* Sun' JAVA, but something designed to have a similar sounding name, but to include no Sun-owned code.

And with both Java and JavaScript turned on (in Opera, by browser of choice), the following URL:

Brings up image "b4" -- between the two indicated.

And clicking on the back arrow takes me to image "f4", not "b3".

And clicking on the forward arrow takes me to image "b2", not "b5".

So with (Sun's) Java and JavaScript both enabled, I get no better response.

Going to the Mozilla which *came* with the Sun OS in question (Solaris 10), I get exactly the same results.

Nothing seems to allow me to navigate it in a logical manner, such as going from "b4" to "b5", or back to "b3".

Enjoy, DoN.