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Suggestions on balancer clearance problems

  1. #15
    www.highflowdynamics.com LakesOnly's Avatar
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    Quote Originally Posted by Caribbean17 View Post
    Hi,
    I Have a chevy engine (Race) that was built to run direct drive from the snout of the crank (Hydroplane). My setup will have the gearbox running off the flywheel end with engine opposite way round.

    Here is the problem, It has a cam driven dry sump pump that doe's not allow enough room for a damper of any sort, Is this going to be a big problem?

    I've included a pic to show how little room there is, about 4inch. It will be run in a Circuit race Boat up to 7000rpm. Thanks for any help
    I interpret your post to mean that you will be running a "crankshaft snout-PTO engine" flipped around and instead operated as a "crankshaft flange-PTO engine." If that's the case, then:

    • It's preferred to have some rotational inertia at both ends for the crankshaft so as to balance out any crank twist but this is not always mandatory. The absolute need (or not) for a dampener depends somewhat on application, how powerful the engine is, how stiff the crankshaft is, the rpm at which the engine will be operating, whether the engine rpm is constantly varied or if it is sustained, etc.
    • Very generally speaking, all crankshafts in running engines have a natural harmonic vibration frequency, and most harmonic dampeners have a vibrational frequency range for which they are tuned to absorb. Usually, non-harmonic dampener engines may experience catastrophic failure when a high-powered engine is operated at a sustained rpm which is inside the range of the crankshaft's vibrational fequency. Running up and through that frequency is not near as detrimental as holding the rpm inside of that frequency range.
    • Over in this camp, the alcohol and nitromethane engines do not use vibrational dampeners. Some of these engines run for just 1320 feet and others run up to 3 miles.
    • If you will not use a dampener on the snout, then I recommend that you make the flywheel side of your engine's rotational mass as light as possible (so as to more closely "equalize" the rotational mass at each end of the crankshaft), meaning use a flexplate and not a flywheel.

    If you simply want to use a dampener on the snout and plan to extend your cam-driven oil pump, then I strongly suggest you fabricate an oil pump support bracket for the end of the pump.

    LO
    Last edited by LakesOnly; 09-26-2012 at 07:00 AM.
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  3. #16
    Senior Member jimclauss's Avatar
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    Quote Originally Posted by LakesOnly View Post
    I interpret your post to mean that you will be running a "crankshaft snout-PTO engine" flipped around and instead operated as a "crankshaft flange-PTO engine." If that's the case, then:

    • It's preferred to have some rotational inertia at both ends for the crankshaft so as to balance out any crank twist but this is not always mandatory. The absolute need (or not) for a dampener depends somewhat on application, how powerful the engine is, how stiff the crankshaft is, the rpm at which the engine will be operating, whether the engine rpm is constantly varied or if it is sustained, etc.
    • Very generally speaking, all crankshafts in running engines have a natural harmonic vibration frequency, and most harmonic dampeners have a vibrational frequency range for which they are tuned to absorb. Usually, non-harmonic dampener engines may experience catastrophic failure when a high-powered engine is operated at a sustained rpm which is inside the range of the crankshaft's vibrational fequency. Running up and through that frequency is not near as detrimental as holding the rpm inside of that frequency range.
    • Over in this camp, the alcohol and nitromethane engines do not use vibrational dampeners. Some of these engines run for just 1320 feet and others run up to 3 miles.
    • If you will not use a dampener on the snout, then I recommend that you make the flywheel side of your engine's rotational mass as light as possible (so as to more closely "equalize" the rotational mass at each end of the crankshaft), meaning use a flexplate and not a flywheel.

    If you simply want to use a dampener on the snout and plan to extend your cam-driven oil pump, then I strongly suggest you fabricate an oil pump support bracket for the end of the pump.

    LO
    Now that is some good info..

  4. #17
    Senior Member SHAWN DAVIS's Avatar
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    I traded a freind a complete Peterson belt drive pump, lines and brackets even a large tank for some stuff, has everything but the crank drive mandrel. I'm sure he would sell if interested let me know i'll get a price
    you can call me if interested 337-802-0904

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  6. #18
    Ain't Right Racin piston in the wind's Avatar
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    Fuel Injection Ent.,LLC would this help

  7. #19
    gn7
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    Quote Originally Posted by piston in the wind View Post
    Fuel Injection Ent.,LLC would this help
    Even if the thing would bolt up, or could be made to bolt up, and you could bolt the pump to it. I don't think it would add any clearance for the damper. The base on that is as thick as the base of the oil pump.
    I think the only thing that will work is an extension like a water pump or fuel injection pump except with the bolt pattern this thing has.



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  8. #20
    Senior Member jimclauss's Avatar
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    Quote Originally Posted by gn7 View Post
    Even if the thing would bolt up, or could be made to bolt up, and you could bolt the pump to it. I don't think it would add any clearance for the damper. The base on that is as thick as the base of the oil pump.
    I think the only thing that will work is an extension like a water pump or fuel injection pump except with the bolt pattern this thing has.
    An extension will work no problem. been there done that.

  9. #21
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    Quote Originally Posted by LakesOnly View Post
    I interpret your post to mean that you will be running a "crankshaft snout-PTO engine" flipped around and instead operated as a "crankshaft flange-PTO engine." If that's the case, then:

    • It's preferred to have some rotational inertia at both ends for the crankshaft so as to balance out any crank twist but this is not always mandatory. The absolute need (or not) for a dampener depends somewhat on application, how powerful the engine is, how stiff the crankshaft is, the rpm at which the engine will be operating, whether the engine rpm is constantly varied or if it is sustained, etc.
    • Very generally speaking, all crankshafts in running engines have a natural harmonic vibration frequency, and most harmonic dampeners have a vibrational frequency range for which they are tuned to absorb. Usually, non-harmonic dampener engines may experience catastrophic failure when a high-powered engine is operated at a sustained rpm which is inside the range of the crankshaft's vibrational fequency. Running up and through that frequency is not near as detrimental as holding the rpm inside of that frequency range.
    • Over in this camp, the alcohol and nitromethane engines do not use vibrational dampeners. Some of these engines run for just 1320 feet and others run up to 3 miles.
    • If you will not use a dampener on the snout, then I recommend that you make the flywheel side of your engine's rotational mass as light as possible (so as to more closely "equalize" the rotational mass at each end of the crankshaft), meaning use a flexplate and not a flywheel.

    If you simply want to use a dampener on the snout and plan to extend your cam-driven oil pump, then I strongly suggest you fabricate an oil pump support bracket for the end of the pump.

    LO
    Thanks, I understand the workings of a damper and feel that the near constant 7000+ Rpms for a good few minutes each run in is too much risk to possibly be within the "wrong range for vibration", sprints, drags etc are more 5-10sec WOT and off again so there is a lot less chance of this occurring.
    Next question is in regards to a blower belt type drive possibly just to an alternator? I'm sure lots of blower motors just run hubs as the belt acts as a damper? It is just a flex plate and small coupling on the other end of crank. Thanks guys

  10. #22
    Senior Member jimclauss's Avatar
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    Quote Originally Posted by Caribbean17 View Post
    Thanks, I understand the workings of a damper and feel that the near constant 7000+ Rpms for a good few minutes each run in is too much risk to possibly be within the "wrong range for vibration", sprints, drags etc are more 5-10sec WOT and off again so there is a lot less chance of this occurring.
    Next question is in regards to a blower belt type drive possibly just to an alternator? I'm sure lots of blower motors just run hubs as the belt acts as a damper? It is just a flex plate and small coupling on the other end of crank. Thanks guys
    I never run a flew plate. Alu flywheel. My choice

  11. #23
    gn7
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    Quote Originally Posted by Caribbean17 View Post
    Thanks, I understand the workings of a damper and feel that the near constant 7000+ Rpms for a good few minutes each run in is too much risk to possibly be within the "wrong range for vibration", sprints, drags etc are more 5-10sec WOT and off again so there is a lot less chance of this occurring.
    Next question is in regards to a blower belt type drive possibly just to an alternator? I'm sure lots of blower motors just run hubs as the belt acts as a damper? It is just a flex plate and small coupling on the other end of crank. Thanks guys
    As much as Lakes post is dead on, I don't feel it tells the whole story. He addresses the natural Freq of the crank and the harmonics but not the torsional twist and rebound that actually cause the vibration. I only mention this because the idea of a blower belt helping is total BS. The blower has its own contribution to flexing the crank. The power draw of the blower is anything but smooth. I creates its own pulses and transmits them to the crank thru the snout. The reason blower guys feel it is beneficial is that IN A CAR, it helps tie the nose of the crank down as is the back of the crank thats propelling the car. Power out the front and back. There MAY be some merit to that. But keep in mind, its alot of power driving the blower. Not some 1" belt driving a pump or alternator.
    If that belt could help the crank, NASCAR guys wouldn't bother with dampers. You could even say a belt cam drive is enough. Its not!
    Look at a Cup car. Oil pump, alternator, water pump, and power steering pump, and still running an ATI damper. Lot of power driving alot of stuff, and still a damper. One little alternater belt will do nothing.

    As for a blower helping in a boat like a K? Its even worse. ALL the power out the snout, and ZERO out the flywheel. With no power load, and no damper, the flywheel is left to deal with virtually all the harmonics that normally exits the ends of a crank. ALUMINUM does a better job of dealing with these harmonics than a steel flex plate. Flex plates are OK for jets and flywheel driven v-drives. Your driving off the flywheel so a GOOD flex plate will work, although I still perfer a aluminum flyhweel. You don't have the water asorber of a jet. Istead you have a two blade prop, and in a hydro, half the prop is out of the water half the time. TALK ABOUT PULSES!! Long ways from a nice smooth jet impeller.
    One reason why jets can run cast 460 Ford cranks for years with no issues. Aside from the RPM, the crank is treated like its hooked to a auto trans converter and damper on the snout.

    Imagine this is happenig to your crankshaft 27,000 times a minute at 7000 RPM, and what you're doing to try and arrest it. You can't do much to keep the intial flex from happening on the power stroke other than running the stiffest, strongest crank you can buy. But the rebound, bending the paper clip backwards each time you can address.




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    Last edited by gn7; 09-28-2012 at 11:57 PM.

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