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  1. #1

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    Results stock and with free mod's

    As with any conclusive test, the results only stir up more questions. . .

    All of the following were done with water and air temps in the upper 80's to lower 90's. I weigh 190 lb and the ski is a '04 RXP with 52 hours.

    - As purchased, oil 1.5" over top bend, 1 bar gas, worn out wear ring: 64.5 mph

    - Drained the oil down to normal level (just under top bend), still 1 bar gas and a worn out wear ring: 64.7 mph

    - New wear ring, but running with 6 bars of gas: 65.5 mph

    - No mechanical changes, but sat at the rear of the seat and crouched down: 66.3 mph

    - Free mod's! Trimmed the reverse bucket and removed the impeller nose cone. I filled the rideplate holes, but upon inspection after the run, the filler fell out of 2 holes and was damaged in 3 more. 1 bar of gas and sat at the rear of the seat, crouching. 67.7 mph

    Every time I ride it, it's a little faster, which is progress. I'm not sure how much of the improvement is due to riding position and weight differences of the gas. I'm also not sure how much good the filler in the rideplate was, being that it was damaged.

    My goal is to break 70 mph and I'm trying to do it with utmost reliability. I understand that Stage 1 (prop, grate, wedge, and air intake) will get me over 70. I wonder how close I could come if I just install the grate, prop, and fill the rideplate holes. . . since this avoids any rectifier cooling or water ingestion issues associated with the air intake.

    Thanks,
    Mike


  2. #2
    GTXX's Avatar
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    just wondering about an engineers opinion on something, how long will a splined shaft run inside a splined part at 8000+ rpm with varying loads using water as the lubricant before noticable damage occurs? that free mod may eventually cost you $250+ for a driveshaft and whatever a prop cost. bah humbug...

  3. #3
    Moderator The Bandit's Avatar
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    Grate and prop should get you there in my opinion

  4. #4
    Site Admin Green Hulk's Avatar
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    Mike, i highly recommend you go with the 14/19R, Riva grate and air intake. You won't have any problems with water ingestion with that air intake in your riding conditions and the Riva air intake comes with a rectifier bracket that relocated the rectifier near the battery. I have never heard of a rectifier burning out from not enough air flow when mounted in this location.

    If you run the 14/19 without the air intake you will have to take some pitch out of it to get max RPM's

    Do those three things and you will be over 70 and be extremely reliable.

  5. #5

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    GTXX, That does cause me some concern, as the rubber nose cone was actually doing a pretty good job of holding the lube in and keeping the water out.

    To partially answer your question. . . it depends on how badly mis-aligned the impeller is to the shaft. If the alignment is perfect, then there won't be any relative movement, and, thus, no wear regardless of lubricant. However, the pump impeller is inevitably at a slight angle as compared to the driveshaft, then during each revolution, the spline will slide ever so slightly and cause wear. The worse the misalignment, the worse the wear.

    You might also consider a dirt bike front sprocket. The sprocket splines onto the transmission output shaft and has no grease or protection. The spline lasts quite a long time in very harsh conditions. Dirt, sand, mud, as well as constant loading and unloading make things pretty aggressive, but it still holds up.

    Knowing the materials combination would help also. Obviously, the weaker material will wear much faster than the stronger one. If the shaft is 4340 (high strength steel) and the prop is 316 stainless, then the shaft will go untouched, but the prop will wear out. However, we know that the shaft doesn't rust, so it may be 17-4PH material (very expensive corrosion resistant high strength steel), in which case it has similar wear properties to 4340. Now, if it is 304 stainless and the prop is 316, then they will wear at the same rate. . . that is if the splines in the prop and on the shaft are both manufactured using the same method. Rolled splines will be much harder than cut splines because of the hardening affect of plastic deformation. Again, if the shaft has cut splines, but the prop has rolled, then the prop will last much longer.

    As Calvin, of "Calvin and Hobbes" fame, once said, "the more you know, the harder it is to take decisive action. When you are informed, you see complexities and shades of gray. You realize nothing is as clear as it first appears. Ultimately, knowledge is paralyzing." It's downright scary how true that statement is.

  6. #6
    RxPrider's Avatar
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    wow.....................u lost me

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