Pros and Cons of jackshaft power.

Discussion in 'Metal Boat Building' started by Capt Sport, Apr 8, 2007.

  1. TerryKing
    Joined: Feb 2007
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    TerryKing On The Water SOON

    I'd like to see that. My current boat (in USA) has a Casale V Drive with a (Shaft I always called "The Drive Shaft") made from a Chevy drive shaft, with universal joints at each end.. It's about 40 inches long, I think. But how did you "change direction"?? No gears.. Hmmm. Chain/Belt??
     
  2. Capt Sport
    Joined: Dec 2005
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    Capt Sport Junior Member

    Ok, to clear up the mystery of where I got the term jackshaft, which to my knowledge has been around in the boating industry for well ever. You can follow the links below.

    http://www.albemarleboats.com/trailerable/242CCspecifications.html

    http://www.volvo.com/vce/Templates/...lications/Search/search.htm&NRCACHEHINT=Guest

    http://marine.cummins.com/public_cu...anchorId=3&contentId=526&marketId=13&menuId=1

    So, you can see some pretty big players in the marine industry use the term as well.

    Thanks for your replys!

    Cya,

    jr
     
  3. Capt Sport
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    Capt Sport Junior Member

    Driveshaft vs Jackshaft

    Rusty,

    Driveshafts are what are in your truck, 4x4's have 2. Jackshafts are what there called when in a boat. Essentially they do the same thing in different platforms.

    Cya,

    jr
     
  4. alan white
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    alan white Senior Member

    It's based on a link at the juncture that has four bearings at ninety degrees to each other, like a u-joint. The inspiration came from a very old patent for an L-shaped link to turn a shaft around a corner without gears. I've got the drawings for the V-drive somewhere. I'll upload them when I learn how to use my new camera.
    The concept of using bearings for gear reduction has always fascinated me. Most are called trochoidal drives. I designed a 5 speed sailboat winch a few years ago, got Harken interested enough to consider it, but no cigar.
    That had a bottom (reciprocating) handle for four ratios and a top crank for fast 1:1.
    It incorporated a rotating cam that shifted by twisting the handle. It had three moving parts. The efficiency I figured would be about 98-99%, contrast to regular winches at 85-90%. I've got hundreds of drawings of that one.
    Trochoidal drives are probably used on submarines to reduce the turbines speed. They have zero pitchline velocity error, something that causes cut gear teeth to make noise (a micro-chatter that comes from an ever so slight speeding up and slowing down of the driven element due to imperfect polishing or wear. True of all gear drives, but averaged in helical cut gears, trading smoothness for frictional loss).
    Subs gotta be real quiet. One drive I came up with showed up already patented in a search. In 1985 someone had sold it to the US Navy. It was identical to mine.
    I do it for fun now. Too much bother trying to patent something people expect to come from an engineer. Very hard to get an audience as a non-professional.

    Alan
     
  5. Frosty

    Frosty Previous Member

    I always refer to it as a drive shaft too.( A shaft that drives)

    A jack shaft is probably some American terminology that we have now and its just another word in the English language we just have to go along with.

    Same --wrist pin --gudgeon pin
    lifter --cam follower
    Transmission ---tranny
    gear shift----gear lever
    Bonnet ---hood
    boot ---trunk -----and it goes on
     
  6. rayk
    Joined: Nov 2006
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    Location: Queenstown, NewZealand.

    rayk Senior Member

    I think you are right jack frost.

    Jack shafts normally have cogs/gears/pulleys on them, except on American boats.
    [​IMG]
    [​IMG]
    Snow mobiles, karts, diesel locomotives, motor bikes and mechanical engineers all illustrate a jack shaft as being geared and in parallel to its input and output.

    Below, the jack shaft is part of the reduction gear, not a flange bolted shaft.
    The illustration below is from NASA, so being wrong aint bad company.
    [​IMG]
     
  7. Frosty

    Frosty Previous Member

    Input shaft -output shaft -1st motion shaft, layshaft , centre shaft, gear cluster shaft, transfer shaft, PTO shaft, propeller shaft

    Normaly a shaft is described in the word preceding it--ie reverse gear idler shaft,---pretty descrptive? jack shaft? --not very clear.

    Shaft fitted by Jack??? jack **** shaft-- does nothing?
     
  8. Capt Sport
    Joined: Dec 2005
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    Capt Sport Junior Member

    Wow, who’d of thought a simple question would cause so much controversy. What’s funny is that “jack shaft” is an accepted term in use by Cummins, Volvo and Mercury marine just to name a few. Which are undoubtedly major players in the marine industry worldwide. Yet so many people here on the boat design board seem to have never heard it.

    Oh, since you seem so adamant about the fact that you’ve never heard the term, so it must be more made up American B.S. Just maybe you Mr. Frost, define the term “jack ****” as in your knowledge or lack there of. As apposed to being open to learning something one doesn’t know.

    Cya,

    jr
     
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  9. Willallison
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    Willallison Senior Member

    now now gents, lets not let this get personal;)

    It's not a case of being a US term - it's used throughout the marine industry as a description of the set-up as shown earlier by Bob S. It's a perfectly straight forward setup and is very common.
     
  10. alan white
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    alan white Senior Member

    It's a troublesome term.

    A.
     
  11. alan white
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    alan white Senior Member

    And that British term for the thing that spins between the tranny and the differential on rear wheel drive cars...?
     
  12. Frosty

    Frosty Previous Member

    Dear oh dear,- only 7 posts and into insulting outbursts. Im sorry that you dont like my interpretation of a jack shaft---you asked the question.


    You may remember your first attempt at posting a thread met with similar confusion.

    I was suggesting that shafts generally have a name preceding---Oh well you can read.

    Myself and other members were now discusing why perhaps a jack shaft is so called. Not that it did not exist. This has obviously angered you because you are not getting what you expect from members who try to diplomatically help you,-- and I hasten to add for free.

    As this is not enough ,--part B of you question is equally as confusing how does this affect manouvarability???????????????

    The same way as moving the engine would!!!

    You seem to have poor understanding of engineering terminology. Your question are confusing. If you dont know what it is, just say the thing that drives the!!! we will understand,-- rather than googling it and asking incorrectly.

    Trying to talk engineer to an engineer will aways catch you out.
     
  13. Capt Sport
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    Capt Sport Junior Member

    Thanks to all that replyed, I sincerely appreciate the information.

    Cya,

    jr
     
  14. dsharp
    Joined: Jan 2006
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    dsharp Junior Member

    jack - shaft

    I knew exactly what you were talking about. I have a 23' Seacraft that was originally set up with a volvo i/o and a 4 cyl diesel mounted midship. I took it out and converted to straight inboard. I never liked working on i/o's after they have been in saltwater. On boats the size that you are talking about I don't know that the handling would be much different because fuel tank placement usually is going to be aft or mid depending on engine placement and the weights are similar.
     

  15. BillyDoc
    Joined: May 2005
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    BillyDoc Senior Member

    Alan, you really have me curious about this, especially the "L" drive and your "V" drive . . . did you get your camera working? I would love it if you posted some details on these various concepts.

    Thanks!

    BillyDoc
     
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