[Question] Gearbox?
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Gearbox?

  1. #1
    Senior Member Jetdream'n's Avatar
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    Default Gearbox?

    Saw this on b1racing.net. Not that my pile needs this or that I could ever afford it but it looks interesting. How does it work? What are the performance gains and or loses. Why do we not see more of these in jet applications? Any more info and pics? Just curious...
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    That is an Owens 2speed. Basically the same as his v-drive version.

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    I think the jet boat guys mostly underdrive the pump to get more engine rpm., so they may not use it as as 2 speed.

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    Senior Member Red Rocket's Avatar
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    It's only low gear. The case is half the size of a two speed and only holds a single planetary gearset. It allows higher engine rpm than jet drive is turning.

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    Senior Member Jetdream'n's Avatar
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    Higher rpm's but lower pump speed?

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    Senior Member Boat 405's Avatar
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    Quote Originally Posted by Jetdream'n View Post
    Higher rpm's but lower pump speed?
    Yes exactly. So the engine can spin where it makes peak power and the pump spin any impeller you choose. A 1200hp 500" deal isn't going to make peak power at say 6800 rpm (not sure of exact rpm vs hp) where an A impeller will absorb 1200 hp. So Put a gear box in between the engine and impeller and Spin the motor at 8800rpm and run the pump at 6800 rpm. Several pro gas guys are doing this. Red rocket, Pattymelt, myself, and others. Probably not ideal for a river boat type deal. These boxes have 1 quart oil capacity and get pretty hot in just one run. They do not have any type of water cooling except direct air transfer.
    Boat 405.

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    Senior Member River Dad's Avatar
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    Is there any significant power loss through the box? I know there were guys talking about this a few years ago and as I recall, most of the racers agreed that the weight and power loss would eat up most of the gains and it would probably not be much of a benefit... Looks like you guys are definitely proving that theory wrong!!!

    RD

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    Senior Member bwurst1's Avatar
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    Quote Originally Posted by widowmaker View Post
    Yes exactly. So the engine can spin where it makes peak power and the pump spin any impeller you choose. A 1200hp 500" deal isn't going to make peak power at say 6800 rpm (not sure of exact rpm vs hp) where an A impeller will absorb 1200 hp. So Put a gear box in between the engine and impeller and Spin the motor at 8800rpm and run the pump at 6800 rpm. Several pro gas guys are doing this. Red rocket, Pattymelt, myself, and others. Probably not ideal for a river boat type deal. These boxes have 1 quart oil capacity and get pretty hot in just one run. They do not have any type of water cooling except direct air transfer.
    Kjell help me understand this. If the engine RPM is 8800 and the pump is at 6800 what is the benefit of spinning the motor that high if its not resulting in shaft RPM? If peak HP is at say 8800 whats the point if its not being transferred to the pump? Seems to me that any engine rpm over 6800 would be a waste. Not knocking it just trying to understand it.
    Thanks,

  11. #9
    Oklahoma Hot Boat Assn BeerBudget212's Avatar
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    That looks like grey matter, if so isnt he spinning that motor to something like 10k?
    Last edited by BeerBudget212; 01-30-2015 at 11:34 AM.

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    Senior Member bp298's Avatar
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    Quote Originally Posted by River Dad View Post
    Is there any significant power loss through the box? I know there were guys talking about this a few years ago and as I recall, most of the racers agreed that the weight and power loss would eat up most of the gains and it would probably not be much of a benefit... Looks like you guys are definitely proving that theory wrong!!!

    RD
    yes, there is some hp loss to the gear. it all depends on the power curve. it comes down to how much hp the engine makes at peak, and how much hp the engine makes with a c or d impeller. prostock engines are very peaky. could be a 200hp difference over the last 1000rpm, hard to say. if the difference is more than you would give up with the box, and you're trying to run pgj or cj, then you run a box. when we were running one 15 years ago, got with a couple other MEs. based on this design, we calculated that the box was taking about 70hp where we were running it. compared to the hp values at the rpm we'd run with a d impeller, the box would get more hp into the pump. your talking tenths of difference in et. but that's really the only application where these things are useful.

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    Senior Member Jetdream'n's Avatar
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    So in this application, it's working the opposite as in a v-drive?
    Last edited by Jetdream'n; 01-30-2015 at 05:08 PM.

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    Senior Member PE 340's Avatar
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    You can run water to a Casale Jet Drive gear box.They have been run in the Parker Enduro Races in the past.This was a overdrive application like a V drive.
    Last edited by PE 340; 02-04-2015 at 12:28 PM.

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    Resident Ford Nut Sleeper CP's Avatar
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    this thread could really use a chart or a graph ............................






    S CP

    "Dark Sarcasm"
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    fast is the other half.
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    Senior Member Boat 405's Avatar
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    Quote Originally Posted by Sleeper CP View Post
    this thread could really use a chart or a graph ............................






    S CP
    I'd love to see a graph of impeller size. Vs hp absorbed and at what RPM. Then add the available gear ratios.

    Right now I think you can get a 19, 21,25,30 and 34 percent gears. Example being. At the 25 gear. The motor spins 1.25 revolutions per 1 revolution of the pump.
    Boat 405.

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