simply put a 7/8 shaft will pull 4-5 mph on a SS than a 1"Quote:
Originally Posted by Propless
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simply put a 7/8 shaft will pull 4-5 mph on a SS than a 1"Quote:
Originally Posted by Propless
WOW that's a big difference ! Sometimes its hard to remember just how much every little thing can add up to.Quote:
Originally Posted by white tortilla
ill check into that lolQuote:
Originally Posted by Propless
so does a 16' boatQuote:
Originally Posted by white tortilla
Maybe, but keeping it set and hammered becomes more of a challenge.Quote:
Originally Posted by ogshotgun
I've seen pictures of a 16' Biesemeyer flat mold. I'd like to play with one of those using a hopped up sbc.Quote:
Originally Posted by ogshotgun
Something to consider when dealing with centerless ground stock is you can't determine the roundness with a set of mics. The process of centerless grinding can produce a shaft out of round way beyond the size tolerance and it will mic good. Every subsequent machining process will be affected by that . If the shaft mics in size and wont fit your coupler this would be an indication. You either have to deal with people and material you really trust or invest in tools to verify it yourself.
Separately from the above , centerless grinding is a primarily a high production process , setup and the guides for doing a step grinding from 1" to 7/8 would be a relatively pricey thing and finding a shop to do one-off stuff on a c-less would be difficult.
The 2 shafts I have seen that have reduced diameter, both ends were still 1", and only the area was reduced, with a very generous fillet. So what goes on inbetween is of little concern provided it is reasonably centered between the 2 original areas. I also wouldn't want to bet they were ground, that was an assumption I my part. They could possibly have been reduced on a lath and "polished" Not sure the accuracy of reduction is all the critical. Even if it had to be done by flipping the shaft in the lath due to length, I don't see what it would matter.Quote:
Originally Posted by sangerdan
The diameter accuracy of the prop shafts is evidently a lot less critical than I would have thought just a few years ago. Because all the shafts I have ever seen were nothing more than mill roll. I have a 17-4 shaft that actually has a very slight depression groove the length of the shaft almost like you would see in welded tubing, and was in service as a multi championship ski boat in the 60s. The groove is kind of handy because you see any twist that might occur in the shaft just by looking at it. Its still pretty much dead straight.
The poster mentions having to enlarge his coupler to 1" so I guess I assumed only the prop end was at 1" ,hence what I said about the expense. Not looking to endure the wrath of anyone but I doubt any prop shaft is just mill finish without being either turned or preferably ground. Part of the finish machining process is to get rid of the surface imperfections and such from the mill.
Or if you have crush grinding on the c-less you reduce the diameter in increments and let it outfeed. Turning on its own diameter will lessen the chance of leaving the prop end too far out of whack. C-less will leave far fewer surface imperfections due to the actual cutting process and leave fewer areas for stress risers. I would imagine it was turned to reduce diameter, I guess I was looking at the way I would have done it for myself. If you're hanging a $2k prop on the end of a shaft this long do want everything leaning your way of is everything good enough. I'm not trying to stir the pot but most guys on these forums are not dealing with 250 horse 45 mph boats , spend 10k on polishing and powdercoat and have your prop shaft touched up on the neighbors 10" SouthBend lathe. Looking only to maybe spread a little knowledge and get some thinking going.
While it is always good to eliminate uneven loading, the prop will still create uneven thrust. Disturbances in the water flow from the strut, from compression against the hull, and especially the prop leaving and reentering the water all generate uneven loads.Quote:
Originally Posted by WESTERNAERO
As for leaving the shaft 1" at the ends, that would require a 1" strut and shaft log. It would seem that more gain would be achieved by reducing the contact area in these areas. I had a discussion about this recently when we were either turning down a 440 crank or boring the journals in the 400 block.
I like the idea of a nc'ed prop BUT in an ideal world it is the best solution. As someone who actually had a machine shop and was killed by the "digitizing" thing, the work will go overseas once that is done. Anyone with a co-ordinate machine can digitize; punch the button and you can have the code spit out the other end and onto your nc. No matter what you think you know about your product when some overseas company puts up an nc prop on Ebay your business is going in the shitter. Shops in the Phillipines were selling a piece on our shores for less than I could buy aluminum by the pound, before I touched it. If the Grose's are prop people and can do what Kindsvater or the other know and can do something is saved. If not hello foreign props. "Be careful what you wish for" means more today than ever.
Obviously the closer to perfect you can make anything the better off you'll be. But as you know, perfection isn't cheap. And since you're dealing with variables to begin with, does it really matter that much? Boats turn (normally lol) so that affects the loading on the prop. I'm sure the water conditions will also affect it.Quote:
Originally Posted by WESTERNAERO
The mass of such a small (relatively) prop spinning at fairly reasonable rpm most of the time, isn't all that great. If the prop was 10' in diameter and weighed 10,000lbs different story.
Not saying its ok to be sloppy, just saying perfection probably isn't necessary for 99% of the boats out there.
I agree John Hart with dirty sanchez does pretty good in his ..Quote:
Originally Posted by gn7
I need to clarify my previous post. I am a geographic undesirable in most of these talks : I don't know any of these people because I'm 2000 miles away. What usually gets lost is the craftsmanship and knowledge of the details when a product is nc'd. If I bought a prop that didn't quite work and needed it tweeked will it still fit the fixturing on the machine or will the shop that machined it have the ability to transform my arm waving and gesturing and non-tech words into what I need. I'll bet the old prop masters could, and that would be a shame to lose for the repeatability of an nc prop. When its a week between races and you want to try XorY don't call Manila or Bejing or increasingly HoChiMihn City or Jakarta.
You could very well be dead on. I just know that I have never seen a shaft that had anything approaching the surface finish or the diameter accuracy of a crankshaft or even a rocker shaft from something like a FE or BB Mopar. Not saying it looked like hot rolled bar, just not something that looked "tight tolerance"Quote:
Originally Posted by WESTERNAERO
Knowingly, no. But how often will that boat see 10,500? Just saying perfection probably isn't necessary. But damn close would be much better :DQuote:
Originally Posted by WESTERNAERO
Centerless ground finish on the size and material of a rocker shaft is easy. Grinding or machining high nickel, chrome and some other alloys is a bitch to do period. Getting a finish that doesn't look like a plowed field is either a lot of work or a lot of very specific experience. Rocker shafts are heat treated and not "gummy" like these shaft materials.
It would be interesting to see what those shafts do in a hard turn :DQuote:
Originally Posted by WESTERNAERO