outboardman10
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- Oct 5, 2003
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- 84
are brass stuffing tubes better than nylon tubes?
in an o.s. motor.
does it rob horsepower?
in an o.s. motor.
does it rob horsepower?
brass stuffing tubes
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izitbrokeyet?
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I’ll go ahead and reply to this one, even knowing it may start some debate on the issue. I’m guilty of putting metal shafts in some of my lowers. The truth is that the Kenetic Coefficient of friction (Uk) of Teflon-Steel is .05 and the best achievable Uk of steel-brass is .06(with lubrication). There’s actually not much difference between the two. With this info alone one might say that Teflon is the only way to go, but the truth is that it doesn’t take some other factors into account.
I have not seen any objective data, but I’d swear that I get a few more RPM out of the same powherhead & prop, pipe carb etc. with the metal sleeve V/S the Teflon sleeve.
WHY IS THIS?? ???
I saw an article at one point that made me feel better about why this may be. The article basically said that the fastest shaft in a tube is in a sleeve where the shaft has 2 points of contact and that there should be a slight “S” bend to promote those “two points” of contact rather than a continuous contact over some arbitrary distance of sleeve.
As we all know, the rigidity of a metal sleeve will promote these 2 points of contact rather than the continuous support that a flexible Teflon tube will provide.
In Summary: I believe there is some benefit to running a metal shaft (especially brass) because it has a relatively low Uk and promotes pointed contact between the shaft and sleeve.
Did anyone ever realize that Ben Stein’s initials were B.S. ?? ;D
I have not seen any objective data, but I’d swear that I get a few more RPM out of the same powherhead & prop, pipe carb etc. with the metal sleeve V/S the Teflon sleeve.
WHY IS THIS?? ???
I saw an article at one point that made me feel better about why this may be. The article basically said that the fastest shaft in a tube is in a sleeve where the shaft has 2 points of contact and that there should be a slight “S” bend to promote those “two points” of contact rather than a continuous contact over some arbitrary distance of sleeve.
As we all know, the rigidity of a metal sleeve will promote these 2 points of contact rather than the continuous support that a flexible Teflon tube will provide.
In Summary: I believe there is some benefit to running a metal shaft (especially brass) because it has a relatively low Uk and promotes pointed contact between the shaft and sleeve.
Did anyone ever realize that Ben Stein’s initials were B.S. ?? ;D
Foolwitools
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- Apr 15, 2003
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- 768
Hey, Izit....... What do you recomend to lube metal tubes? I bought a stainless tude for a 7.5 and the poop sheet says 50/50 STP and 50wt motor oil. Whatchatink?
Hi Guy's
My $0.02
Teflon without lubricant has lower friction than brass lubricted - no disputing the facts.
Dilemma - lubing teflon tubes with oil or grease probably increases drag on the flex as they both have higher stiction than teflon. The bearings in the prop driver are cooled and lubed by water - eg that's what the holes are for. Do we wear them out faster by clogging up with grease/oil? ???
I think this is really a preference issue - with the OS which has a much better tube flex and angle set-up than the K&B I'd guess it isn't worth changing.
Can someone do back to back testing measuring speed and RPM and tell us. That should settle this debate? once and for all.
GT
My $0.02
Teflon without lubricant has lower friction than brass lubricted - no disputing the facts.
Dilemma - lubing teflon tubes with oil or grease probably increases drag on the flex as they both have higher stiction than teflon. The bearings in the prop driver are cooled and lubed by water - eg that's what the holes are for. Do we wear them out faster by clogging up with grease/oil? ???
I think this is really a preference issue - with the OS which has a much better tube flex and angle set-up than the K&B I'd guess it isn't worth changing.
Can someone do back to back testing measuring speed and RPM and tell us. That should settle this debate? once and for all.
GT
izitbrokeyet?
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- Apr 5, 2003
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Sir,
I don’t think what you use to lube matters as much as how frequently you lube your shafts. I'd recommend Lubriplate for metal sleeves, but any light lube for a Teflon sleeve should work fine.
I don’t think what you use to lube matters as much as how frequently you lube your shafts. I'd recommend Lubriplate for metal sleeves, but any light lube for a Teflon sleeve should work fine.
hi all i have been running a beass tube in my 7.5 and 11 cc out board lower unit for 4 years now with no power loss or speed loss the only thing is i do not break no more shafts anymore i lube befor every run with stp with no oil mix this works for me jimmy
