Prop Shaft

[sangerdan]

I have an honest question that I'd like some input on. Has anyone ever done the prop end in splines like a drag axle and splined the prop. I don't know that that interference fit of a matched taper could be duplicated for lack of runout. Pro stock drag axles are 300m material which is in the same family of materials as a prop shaft. Gundrill a maybe slightly larger diameter than current shafts for strength and??? Broaching splines can be pretty accurate. Just a question keep the stones thrown on the small side!

[sangerdan]

Yeah I get it. But when you're talking about a 3-d surface like these props have, I feel the best way to make them is with CNC machines. Both sides come out equal. Now is it as critical with a 3, 4 or 5 blade? Hell no, they'll have an easier time balance themselves out. And as far as being able to tweek or rework a prop on a CNC, absolutely! And if the programmer is really good it can be done in a fraction of the time than doing it by hand. You can twist and tweek surface profiles anywhere you want on a CAD.

But theer has to be material to work with to change the profile on a cnc but I thought some props ears were worked, call it bending if that is correct. I guess my point was, I hope that knowledge isn't lost or does the guy making the cnc prop retain the knowledge to make the tweek . If I have prop"A" and say I need more lift for example who does he call to find out what program to run to get that.

[gn7]

Yeah I get it. But when you're talking about a 3-d surface like these props have, I feel the best way to make them is with CNC machines. Both sides come out equal. Now is it as critical with a 3, 4 or 5 blade? Hell no, they'll have an easier time balance themselves out. And as far as being able to tweek or rework a prop on a CNC, absolutely! And if the programmer is really good it can be done in a fraction of the time than doing it by hand. You can twist and tweek surface profiles anywhere you want on a CAD.

Exactly. No hand shaped prop has two identical ears. let alone identical to another prop. Even as good as CNC is, it is still no guarantee. Tom Black of Precision learned long ago that just the smallest difference in batch material, and HEAT TREAT!! made a huge difference.
We have reworked 2 Hill 17-4 SS props to 99% of our original Hill prop that finally developed crack after have been in service as both a GN and K prop and a few championships under 3 different boats starting in 1988. We had the "twin" to it for awhile that had its own history. Remarkably, both props gave up the ghost on the same weekend at Parker. The other rip the ear off at 100 plus, our revealed a crack after Sat races.

In all the testing and mods of a dozen props, we have finally come to the conclusion that for us to get the same speed and handling from a steel prop is going to require some more testing and or some changes to the boat itself. We just could never get to where we wanted to be with a steel prop. Close, but close only works for back up props, or use in the endure, or as a river/lake prop, which is exactly what they are used for right.

Its the one thing that makes me hesitant to pay to have the prop digitally mapped, and made. I don't see the SS shape working correctly in a 4330 prop

[sangerdan]

GN brought up a good additional point about materials. If someone has a basket full of forgings of a certain material "A" what good does mapping a prop do when I have a prop from another material "B". Even Bobs17-4 prop could have been heat treated about 6 different ways. I'll bet there has been more recent engineering on sails than on the drive line of our boats. How does one guys shaft bushing go away in months and another goes years. can't all be owner error. The tolerance build-up on some setups might be beyond belief.

[gn7]

Pretty sure most the circle boats are seeing those RPM's at the prop most of the time. Not engine RPM, prop shaft RPM. Don't most of them run 50 over or somewhere close to it. Where's Bob?

It would be interesting to see what those shafts do in a hard turn

I asked that same question and I think these guys are concerned with the larger shaft diameter creating more drag in the water.

But theer has to be material to work with to change the profile on a cnc but I thought some props ears were worked, call it bending if that is correct. I guess my point was, I hope that knowledge isn't lost or does the guy making the cnc prop retain the knowledge to make the tweek . If I have prop"A" and say I need more lift for example who does he call to find out what program to run to get that.

Well I guess if someone don't start doing it soon then all V-drive boaters will be without props soon. Why does every other motor sport advance and change for the better and the v-drive industry sit stagnate? Because most of these guys want to keep doing things the same old way.

Circle boats are hard on the props and shafts because they are constantly cycled between max torque and max HP. If you want to break something on the dyno, you do just that. There is a video on You Tube of Mercury testing the 1350 4 cam and that's exactly what they do in the video.
What a shaft does in a turn is a very interesting thought, and assure you, its not pretty. But then anytime the boat exposes the shaft and lands has a similar effect, just upward.
Flats are much worse the GNs because the GNs tend to track the turns more than the flats. Those suckers do some slipping.

Asking how often the shaft sees max RPM is like asking how often it wins. If it isn't hitting max Rs every lap, it isn't winning.
Only the Ks are running gears in the 50s. Pros and some SS in the high 20s low 30s, GNs pretty much the same.

As for knowledgeable tuners......its a dying art form. Harold Kinsvater is tops, but is pretty much in semi retirement. None better than Gibbs in Havasu, but it VERY picky who he will do a v drive prop for. The guy that took over PB props up north I understand does some nice work, as well a guy I Texas, and Florida. My secret weapon guy is truly remarkable. He was doing the props for Ben Morrone's GN 305, and he made "tuned" them up a gaggle of props. He is willing to try anything just to see the results. He just likes working with a known combo he feels is repeatable, and a driver he feels can give him good imput. Bill and him just flat click.
His name is Brent and he goes by Props Works West on PB, and his claim to fame believe it not, is props for RC boats to the rich and famous, like Anton Brown, but he is looking to make a name in circle boat props. He has 4 championships under his belt to date, and he might be doing some work I am not privey to.
How you make a prop provide more or less lift is pretty much a known "shape" of the ear, or more accurately, the fore aft angle (rake)and location of the ear on the hub. Just as moving the whole shaft forward effects the nose lift, so does just moving the blade forward on the hub relatively speaking. Leaning the blade back as opposed to more straight up will raise the nose too.
Where things get really trickey is in the interface area between the blade and hub, and that's where our props get pretty strange. When SFV2RVR was suggesting that the prop under his Schiada would work reasonably well under my GN, he some what right. It would get it up and down the river, and blast across Havasu just fine. It could never be raced under my boat with any success. Been thru waaaay too many props to know that's never going to happen.
Had props that were 2-3 MPH faster, and handled like a kicked football. Ones that handled "reasonably" well, and 5-6 mph slower. And more props than you can imagine, including brand new props from Both Menkins, and Radience, that did nothing right.

[SnoC653]

I think too much relevance is being placed on uneven trust from the prop ears. Hydro's run the same basic shafts (materials and dimensions) and one ear is providing all of the thrust while the other is out of the water providing zero thrust. What are they doing better than the flats?

[Propless]

I think too much relevance is being placed on uneven trust from the prop ears. Hydro's run the same basic shafts (materials and dimensions) and one ear is providing all of the thrust while the other is out of the water providing zero thrust. What are they doing better than the flats?

I have theory on that. The hydro prop will still have a consistent load even though its not even. It would be a forward from the bottom force. Probably trying to bend the shaft up in the middle. But an uneven load from a prop that has different bite from each blade would have a different force on the shaft depending where the good biting blade was. Good blade on the bottom forces the shaft up, good blade at the left shaft forced right, good blade at the top shaft forced down, ect. I could imagine the shaft looking like a jump rope when it was under a load.
Just an opinion.

[gn7]

I have theory on that. The hydro prop will still have a consistent load even though its not even. It would be a forward from the bottom force. Probably trying to bend the shaft up in the middle. But an uneven load from a prop that has different bite from each blade would have a different force on the shaft depending where the good biting blade was. Good blade on the bottom forces the shaft up, good blade at the left shaft forced right, good blade at the top shaft forced down, ect. I could imagine the shaft looking like a jump rope when it was under a load.
Just an opinion.

Not even close. The prop is running off/on the whole time.
When the ONE blade is headed down, it is doing the vast majority of the work to the point it passes straight up and down. Then its doing progressively less, while the other is beginning to do progressively more. But when they are dead horiz, neither is doing shit. No prop is loaded and unloaded like a hydro prop, and its only worse the more power you put to it.
With the twin props, they are arranged 90* out of sync, and the forward thrust is relatively even, although still off and on per side during the run. The fact they are counter rotating helps immensely with the stability of the boat, and counters the "side walking"

You can see the on/off in the rooster tails. This is actually a mild case.

[gn7]

Our #1 prop for 5 years had one ear 1/8 larger/longer from the hub than the other. Perfectly balanced, but the ears were different "lengths" and it never shook, or hurt a bushing in any boat it was run on in 25 years. If it doesn't shake, or hurt things, I don't sweat it.

HOWEVER, it still points out what I said OVER AND OVER, don't try to bullshit me with intellectual property for something you CANNOT reproduce.
If the dipshit can't get 2 ears right on the same fucking prop, how can the dumbass claim anybody copied shit.

Don't get me started again whos IP the tuning of a prop belongs to.

[Propless]

Not even close. The prop is running off/on the whole time.
When the ONE blade is headed down, it is doing the vast majority of the work to the point it passes straight up and down. Then its doing progressively less, while the other is beginning to do progressively more. But when they are dead horiz, neither is doing shit. No prop is loaded and unloaded like a hydro prop, and its only worse the more power you put to it.
With the twin props, they are arranged 90* out of sync, and the forward thrust is relatively even, although still off and on per side during the run. The fact they are counter rotating helps immensely with the stability of the boat, and counters the "side walking"

You can see the on/off in the rooster tails. This is actually a mild case.

Ok but that doesn't make me wrong. The hydro prop is still doing the majority of its work in a bottom forward way, whether its consistent or pulsed. So it should force/flex the shaft in one direction, right ?

And a flatbottom or V hull prop (fully submerged) that had better bite/greater thrust on one blade would be creating a greater force at whatever position the strongest biting blade was positioned. Trying to whip the shaft around like a jump rope.

And you know I only ask because I love to learn. But just because your prop and one blade/ear 1/8" longer, doesn't mean it had an unbalanced amount of thrust from each blade. I would guess that the number of variables that determine the actual thrust from a blade/ear are greater than I could even imagine. So I'm sure that even though yours had one ear longer, it still could have had equal thrust from each ear, right ?