Shaft material opinions?

Discussion in 'Props' started by Sindel, Aug 14, 2009.

  1. Yellowjacket
    Joined: May 2009
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    Yellowjacket Senior Member

    Here we go again...

    Frosty,

    No I didn't say that increasing the shaft size at the place where it is bending wouldn't improve the bending problem. In fact I said it would help in that regard. I just wasn't sure that it was worth it, or that it couldn't be addressed with the material change.

    And yes he might be able to turn his existing coupling out to a larger SAE size, but if he does he risks increasing the stress in the shaft because, for a given shaft misalignment, the stress will be higher because the shaft is stiffer. Sit down and do a bending stress calculation for a canteliver beam and you will see that for a given deflection the stress will be higher for the stiffer beam. So increasing the shaft diameter will make the bending stress (which was the cause of the failure of the shaft in the coupling the last time) for a given deflection higher. It will also put bigger offset loads on his engine which is not a good thing either. I said he might be able to mod his coupling to fit the SAE format, but not sure if there is enough length to have a sufficiently long taper and the nut within the present envelope for it to work properly. Since I don't have the dimensions of his coupling, don't know the material and haven't looked at it, it is probably less hassle and risk to just go out and buy one. Since he is making a new shaft, a new SAE coupling for his current size shaft is, in my opinion clearly the best way to address the failure at the coupling that he saw without risking a failure due to a change in stiffness that results in higher shaft bending stress.

    Sindel seems to want to keep his boat as original as possible. Not sure that he would want to modify his existing cutlass if it wasn't going to make a big difference. And I really doubt that he would want to put a new replacement on that wasn't a duplicate of the original.

    As I said, there probably aren't any real simple solutions here since stiffening one part will just transfer the loads somewhere else and push the failure upstream to the next weakest link. Unless he can keep from hitting big chunks of wood at speed, he is likely going to have some damage, the only question is where that is going to occur, and how much collatteral damage is going to happen along with it.

    If you are an engineer (as your profile says) do some back of the envelope calculations before you give somebody some advice, or at least give the basic engineering principles some thought before you chime in...
     
  2. Frosty

    Frosty Previous Member

    Might be able to turn out to SAE. Probably are'nt any simple solutions?--Probably. Are you not sure? Off set loads on his engine ??? what rubbish.

    Probably, maybe, might???

    No I don't work things out on the back of an envelope which a lot of people do and still dont know.

    I can only offer experience of doing "exactly" the same thing on the rivers in summer of England. Albatross , Delta, Moon fleet, all shaft drive, and ive owned all of them, thats all the ski boats we had in Uk 40 years ago.

    Bent shafts week by week, vibrations, and shear,----ski one day fix the next.

    I also imported the first Master craft into Dubai 28 years ago for the first Gulf water ski championships

    How many shaft drive boats have you had? It does'nt matter --I don't care.

    But you go ahead you tell him what would probably fix it. Its all yours
     
  3. Sindel
    Joined: Jun 2009
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    Sindel Junior Member

    Ad Hoc
    See opinions are more fun...
    I go boating (having fun and enjoying myself the whole time) for the weekend and have all sorts of opinions to generate thoughts for me.
    Shaft's are 1" and 32.75" long...
    And, I know a lot of the boat could be better designed, but I am happy with its performance with all it's antiquated components.

    CDK
    I'm not looking for something that I cannot break...
    Actually would like to be harder to bend than the ss, but not as hard as to break like the aqua-whatever. The design of where I live on the river would be the most I could do...

    TeddyDiver
    The bottom 3 shafts are rock hits in that picture.
    - Bottom picture was my first trip up the Auglaize River... (choose never to go back that way again...)
    - 5 years later...
    Wife wants this house on the Auglaize about 600 yards past where we hit before? We chose to trailer the boat for the first month until a neighbor showed us the way through. I also ride back a forth in an aluminum jon boat with a modified outboard (extra aluminum plate beam clamped to skeg) and try to find the rocks... The 2 (worst) bent shafts are from this area of the river...
    The top shaft just got tired? (my antiquated stuff contributed this?)
    The next 2 are from hitting logs, of which the worst there also tweaked the strut... I bought a new/used/different strut (before I knew they could be straightened)
    The engine is supposed to be 105HP (so say the manual?)

    apex1
    As always, your advice is well appreciated. Thanks
    Does bronce bend or is it more likely to break?
    How do the various stainless steels on the market compare for strength?

    Frosty
    Yes, an old antique pinch is all that was used in the day (I use 2)
    Failed me once in 11 1/2 years (I can live with that...)
    And yes again, a tapered coupling connection would be better, but there isn't much space and the redesign never gets much thought until there's an incident... (I haven't run across any standard specs to go from)
    Driving? Not poor navigation or bad location?

    whoosh
    What's 2205 like?
    Will it bend? How much before it breaks?
    I want something that will bend, just not too easily...

    mark775
    Good for you...
    I'd have to agree on that tapered coupling... I installed one on my father-in law's CC Barrelback, but he has an extra foot behind the engine to play with. The coupling we got from the prop shop takes 3" to remove (I've only got 2.375"?)
    Pinch screw are those pointed set screws with the safety wire hole in them...
    I always thought these set screws and the brass key I use would be the first to fail, but I've only ever had one complete failure...
    And the reason for the bad "milled" in keyway's - my lack of tools... (I made the shafts myself...)
    Would it be okay if the prop has a keyway, the shaft does not, and no key used at all? should a bastered key be made to fill the void?

    Yellowjacket
    Thanks for your thoughts, very helpful...
    The tapered end break was caused by a high speed rock! Nothing will probably stop this except maybe to drill a hole in the rock and use some dynamite?
    The other shaft break was fatigue from my antiquated setup?
    Might it be better to bend than break? This is my thinking...
    As for shaft material verse price... Is the aqua-whatever worth the extra $125 over the stainless when there's a possibility of loosing a prop... This is what I'm trying to determine for myself... (and to find out if others are using different solutions)

    Frosty
    Can't ever seem to get enough in... ever!
    The vibrations must be bad... In a wooden boat? Have you ever ridden in one?
    The wood flexes quite a bit... fore to aft measurements change around an inch from winter storage to summer use...
    Rides in my buddies mastercraft are much rougher and feel totally different...
    You can change the size of the cutlass... Really?

    Yellowjacket
    Don't worry about Frosty... Every post I read where he comes up, it's the same old... (you should, I have done, etc)
    Do you know where I can find some specs on shaft tapers for couplings?
    When I first got the boat, someone had repowered it with a 350 v8 and was using a different strut with 1 1/2" cutlass... (broke, cracked, destroyed lots of the frame...)

    Frosty
    Your experience must have been very sheltered. Or your ego just can't see past the tip of your own nose?
    I have got to enjoy my boat everyday except 3 this year... (since it's been in the water May 30)
    Twice due to rain and once to take my damaged props to the repair shop. (they're always happy to see me and my $$$)
    So easy to fix... Can pull the boat; change the prop, shaft, and coupling in a couple of hours; and be back in the water to enjoy a nice ride with my wife and dogs before going to work...

    Thanks everybody, you've given my lot to think about...
    Type of metal for coupling?
    SAE coupling specs?
    What shaft material should I use?

    All is good in life, when your boating... :D
     
  4. baeckmo
    Joined: Jun 2009
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    baeckmo Hydrodynamics

    Exactly, and this is why I proposed a highly flexible coupling in the other thread. The fact that this is a wooden boat, which does a lot of flexing, makes this even more important. And I hope that you do the final shaft line-up with the boat in the water??!

    As for tapering the coupling end of shaft; forget it! Use one of the excellent clamping couplings instead (Even if you don't go the rubber coupling route)! For the shaft speed here, use the type with conical compression rings, not the slotted variety. Some of the materials available for shafts have been sensitive to "slot corrosion"; so give the coupling/shaft end a spray with thin corrosion protector ("Tectyl" or similar), giving a waxlike surface when dry.
     
  5. Sindel
    Joined: Jun 2009
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    Sindel Junior Member

    baeckmo
    Exactly why I started the discussion...
    Worried about breaking a shaft or something worst...
    Cost-wise I'm thinking about going back to my homemade ss shafts...
    But maybe there's something else to use, hence the questions...
    As for the clamping couplings, how do they come apart?
    Who makes them?
    Tectyl? Never heard of this... (I'll have to google it...)
    What kind of flexible couplings are available?
     
  6. apex1

    apex1 Guest

    Go "Vetus.com", you´ll find most of the stuff you need, proper descriptions and fair pricing.
    And do´nt be bothered when others tell you, you could have done better. These are the folks having usually less hours on their mains, than we on our wiper motor.
    Stay with your bronce props, they bend, dent before they break and can be hammered back as often as you like to hit the rocks. The duplex steel shafts are pretty strong, but not too strong (to kill the gear instead), as I mentioned one page back, do´nt make the gear the weakest point. The Bullflex coupling is a nice thing but not cheap. When you cannot manage to align your system perfectly you might need it unfortunately. And make the final alignment on the floating vessel! As Baeckmo said, you have a flexible boat (all boats are), so a "dry" alignment is just a first, broad one. And listen to Baeckmo´s advice, he knows what he´s talking! (yes some others too, but I cannot comment on their expertise)
    Tectyl 506 EH is what you are looking for.

    Regards
    Richard
     
  7. CDK
    Joined: Aug 2007
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    CDK retired engineer

    1 person likes this.
  8. Yellowjacket
    Joined: May 2009
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    Yellowjacket Senior Member

    Baeckmo is right in that it is probably easier to use a more modern coupling but I am thinking that Sindel wants to keep the design close enough to what is original that he can show the boat and not install a different shaft every time he goes to a show. If that is his desire then he can make a mild steel coupling with the outside dimensions and flange that is the same as his current coupling and cut the inside to an SAE # 1 coupling, and drill and tap the outside with four faux set screws and he will have a centered modern coupling that looks like his original. A bit of work, but if he has access to a lathe and a mill it isn't going to take more than a day to make it.

    Here is a link to Gerr's Propeller handbook table that has the dimensions of SAE prop shaft couplings (look at tables 1 and 4) which go down to a 3/4" shaft diameters and will work fine for what he wants to do. If the link doesn't work just google "SAE shaft couplings" and this popped up as one of the first hits.

    http://books.google.com/books?id=8w...xxfsO&sa=X&oi=book_result&ct=result&resnum=1#

    I am also in agreement with Baeckmo in that boats are flexible and that some type of coupling with a high degree of misalignment (radial and angular, but in particular radial) are good practice. You are going to have to take it out for showing, but it will likely save you a lot of headaches in the long run to have it in there on a daily basis.
     
  9. mark775

    mark775 Guest

    "As for tapering the coupling end of shaft; forget it! ...use the type with conical compression rings" - Could you please post a pic? A tapered coupling is the easiest way to perfect alignment, every time, that I know. Enlighten me - you are very confident!
    Not using a key? Drag boats with thousands of horsepower don't use keys. The Morse taper of your drill press handles much more torque than your propshaft. It's not a Morse taper but something else - 1/16" per inch, maybe? I don't know. Make sure to lap the prop to the shaft. The worst that can happen is that your prop spin if nuts not torqued enough, right? It might even save you a tranny if you mine rocks again.
    These "pinch bolts" have no place anywhere near this application, IMO.
    Alignment in or out of the water - I have my own way of doing things here and what these guys are saying is customary and accepted. I feel, align out of the water and check in the water and note the difference but do align to the Nth degree.
     
  10. Sindel
    Joined: Jun 2009
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    Sindel Junior Member

    apex1
    Wow, what they make for boats these days... Thanks for the site.
    I'd like to stay with the Bronze prop, but what if I loose it? (I'd like a spare...)
    Rocks have been located (for this year), I just can't believe how much the ice flow in the spring can move some of those monster boulders.
    But hammering the prop back to shape? I would hope the prop repair shop would do it differently...
    Might just have to give that duplex ss a try when I redesign my coupling... Really am amazed by that bullflex, its design is inspiring... Perhaps I could design a coupling with build-in flexibility? (space is limited...)
    Alignment is done before the boat goes into the water, then again while it's in the water - daily for the next 3 days... And yes it moves, seems to be about the same each year... I usually have to lower the front of the engine on day 2, but in the fall when the weather gets cooler, it usually need to go back up a little...
    Is that Tectyl 506 EH available in small quantities, perhaps under a different name? Are any of those aerosols they make any good for my needs?

    CDK
    I've been meaning to redesign that coupling for years; just didn't have a clue as where to start. Most of the "old" boat people I talk to think it's ridiculous to want to change anything for the better on these wooden boats (ie They all run points? Lots of 6 volters? Most only see the water for shows?) Why have a boat, I always ask myself?
    I don't have room for a universal or anything, but that coupling of yours is so simple, it really take away my fear to design and build something better for my boat... Thanks for the photo...

    Yellowjacket
    Did you get wet today? It hammered down rain this afternoon here, stopped for a bit after dinner (for me to take a boat ride :D ), now it's raining cats and dogs again...
    Your right on with my desire to keep things looking original. Would mild steel be strong enough? My taper could only be about 1 1/2" or so... (I'll have to check out the link/specs you gave me...)
    I do have access to "big enough" leftover stubs of mild steel, various high carbon steels, even tungsten/steel alloy. (I make my current coupling from tungsten - probably overkill is't it?)
    And the flexible coupling... Ever see anything that's not so ugly?
    I only take the boat (for showing) to 2 or 3 shows a year, so taking out something like my drivesaver isn't really that much of a hassle. Something with pins, a bunch of retaining rings, and 3 specialty tools tools might become a bit much, but something one piece would be easy enough... However, I'm not sure that my drivesaver does a good enough job, any thought or suggestions on this?

    mark775
    I'm not sure about this conical compression rings type coupling either...
    I definitely see and more importantly understand (in my mind) how the taper would work to center the shaft and believe this to be the way to go... Thanks.
    Not using a key? I'm still not convinced... I would feel the need to pull the boat out of the water often to recheck the nut for tightness (especially without a cotterpin and me hitting logs...)
    With a drill press, you're always exerting more force to the taper making it tighter, and the drag boats don't stay in the water for months without checking things, do they?
    If I were to go without a key, I think I would feel safer with a cotterpin, but then torquing becomes an issue...
    Arg... Not sure here... Affects would be minimal... (loose a little cotterpin drag, but oh, I got a big fat rudder) I'm not sure I see any benefits with this other than not needing to cut my own brass keys or buying a cotterpins?
    The idea of the prop spinning on a hit is okay, but if the prop somehow got loose when I'm out in the middle of Lake Erie and there a storm rolling in... :confused: Then what?
     
  11. mark775

    mark775 Guest

    I grew up with the drag boats on Spanaway Lake and Thunder Boats on Lake Washington - Never could resist sneaking peeks at what's underneith/inside when I could.
    The advantage to no key is probably moot here if the prop is installed properly. Big horsepower will find weaknesses like keyways and you don't have big horsepower. I'll tell you what, I've never done this on a boat where it is critical to keep going but I will. I will put a new prop on my passenger boat and there will be no keyway ( I intended to do this anyway as I am marginal with something like 1,100 ft.lbs of torque through a 2" shaft and want to dispense with the keyway). I'll let you know in one year if it worked! The important thing is to lap the prop to the shaft well and torque and jam nut. Lapping is critical with or without a key and nobody does it anymore!
    I certainly don't intend to offend here by questioning your abilities but just to make sure: Install prop on shaft without key. Torque nut on lubricated threads and prop face. Make a Sharpie line at the highest point of the prop. Remove prop. Place key. Repeat install and if the prop did not go as far up the shaft as it did the first time, you are riding on the key with no chance of fit.
    The cotter pin might keep a prop from falling off, I 'spose but if the prop is that loose...I just always have seen them to be ugly, hurt, catch fishing line and unnecessary. Try jam nutting in Rectorseal or 5200 as a lubricant.
     
  12. Yellowjacket
    Joined: May 2009
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    Yellowjacket Senior Member

    Sindel,

    No, it blew over us, we have't seen rain in two weeks. Every time it looks like it wants to rain, it just passes us by....

    Mild steel will work fine here, there isn't much stress in it and the original coupling was probably mild steel. You can get the same "patina" pretty quickly in mild steel...

    The SAE couplings have a keyway in them. I would look at the amount of taper length that you have available, and if it is more than the SAE spec then maybe you won't need the key. If it is less you should put it in for sure. Mark 775 is right in that there isn't a lot of torque here, but if it slips it is going to make a mess of things. I'd probably just put a key in it and walk away. Also make sure you find a low height locking nut for the end of the shaft. Our dyno came with an SAE coupling and it had a slotted end low height lock nut that fit really nicely in the recess of the coupling. McMaster-Carr has them, they are called Flexloc style expanding lock nuts. They are better than Nyloc nuts and come in stainless steel.
     
  13. mark775

    mark775 Guest

    Thanks a lot, Yellowjacket - I just killed hours on the McMaster sight!
     
  14. Frosty

    Frosty Previous Member

    This is an interesting thread. A guy who is well capable of fixing his problems asks questions that he knows the answer to.

    He gets people dancing to his tune as he gets everyone to talk about his beloved boat. When some one gives him a good answer he comes up with, Oh My brother in law has the propeller, or I don't want to move a way from original (crap 50 year old engineering), or I don't have the money,--he just wants to talk about his boat some more.

    His boat is original he says then posts pictures of a fibre glassed bottom!!!!

    Whats next --? lets discuss the flag pole position.

    Im going to thank you Sindel for helping me to see the light. I wonder how many other threads absorb time by members trying their best to hep and get kicked in the teeth.

    Ive learned a lot from you.
     

  15. Sindel
    Joined: Jun 2009
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    Sindel Junior Member

    mark775
    It's not that I don't think "no key" won't work...
    I like the thought of the redundant features (key and cotterpin) since I'm lazy and forgetful...
    And, I don't see the need (105 hp)
    As for spinning on the shaft, probably not a good thing...
    But I'd still be interested in how it works out for you.
    Wish I had someone to explain that key interference thing to me years ago. I had the hardest time fitting the key when I purchased my first aqualloy shaft. It had rounded edges in the keyway all the ones I made had a square "milled" bottom... I did exactly what you suggested after having already tried to tighten the thing 2 or 3 times unsuccessfully.

    Yellowjacket
    Still no rain?
    We got hit again today... Got over 5" these past few days and the river shot up 4 feet.
    Thanks for the confirmation; I'll have to keep my eyes open for a chunk of mild steel for a new coupling... The original that I got with my engine was actually cast, but almost every other I've seen has been steel. I'm sure using it will add the patina quick enough.
    The SAE couplings look easy enough to make and I should have room. I guess the biggest thing will be room to get to the nut? Nuts at McMaster, great! Thanks...

    mark775
    Thanks for looking out and sorry about your time. Searching that McMaster site can be maddening...

    Frosty
    Yes, capable, but needing the direction of others... (I thought this was a "discussion" forum)
    There isn't much room to dance and you'll have to bring a radio if you want tunes...
    Sorry you don't approve that I married into a family with 7 chris crafts and 3 lynmans.
    Money's not the issue, it's paying more for something when less will do better. (at least in my situation)
    Trying to maintain the boats original appearance doesn't always mean like the factory did it. The factory only put 2 or 3 coats of varnish on the boat, never considered bookmatched planks, etc.
    The west system bottom was a bad idea (I feel now), but my father-in-law said it would be my best solution since this was my very first boat ever. There are 2 other boats in the family with west bottoms... The latest boats we've restored have been given 5200 bottoms.
    Is there something wrong with the position of my flag? I've seen several other Rivieras with their flags mounted in the same place?
    What would indubitably help here would be if you could enlighten us about their proper placement...
     
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