Simple CPP

Discussion in 'Props' started by born1957, Jul 12, 2015.

  1. born1957
    Joined: Jul 2015
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    born1957 New Member

    Hi all,

    I wish to present an idea of simple CPP. It is a solid shaft controllable pitch propeller. The structure and application will be simpler than the conventional hollow shaft CPP.

    Start with a hollow shaft CPP with a control rod. If we remove the hollow shaft and connect a rotatable collar to the hub, relative postion between the collar and the control rod will determine the pitch. Finally, apply a spline coupling between the control rod and the hub, we then can use the control rod as the drive shaft.

    By this configuration, pitch control can be done by moving the collar or moving the shaft while the other is fixed.

    Simple demo is shown in the picture.

    The control rod (1) inserted into the hub (2) with control grip (3) holds and controls the pitch of the blades (4). The rotatable collar (5) connected to the neck of the hub via a bearing set (6). The hub will be rotated by the drive torque applied to the control rod which also acts as a drive shaft via the pin (7) on the control rod and the slot (8) on the neck of the hub which acts as a spline coupling.

    Pitch control is done by holding the shaft(1) and move the collar (5) along the shaft, or holding the collar (5) and moving the shaft(1) through the hub (2) using extensible shaft.

    This solid shaft CPP has many advantages, for example:
    - no limit in size, applicable to all boats and vessels.
    - non hydraulic hub, under water serviceable.
    - cascadable to make twin prop contra drive with sync pitch using double layer counter shaft and connecting the collar of second hub to the tip of the first hub.

    Demo video can be viewed at
    https://www.youtube.com/watch?v=dWh7ZLGRoq8

    Published patent:
    https://patentscope.wipo.int/search/en/detail.jsf?docId=WO2015050508

    Regards,
    Jack
     

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  2. Jamie Kennedy
    Joined: Jun 2015
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    Jamie Kennedy Senior Member

    Very good Jack. I like it's scalability down to small DC electric motor driven shafts for smaller sailboats, that might only need 500w or so, and infinite variable power down to very little for solar assisted sailing in light air. Also provides opportunities for recharging batteries.
     
  3. TeddyDiver
    Joined: Dec 2007
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    TeddyDiver Gollywobbler

    That's about the same configuration as the old SABB CPP's. Dozens of them still running around here.

    Ps. Sorry to pour rain on your patent apply but the original patent most propably is expired so it's free for anyone interested..
     
  4. born1957
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    born1957 New Member

    The different of this Solid Shaft CPP from today CPP is, this CPP doesnot use hollow shaft but all other CPP include SABB still use hollow shaft.
     
  5. baeckmo
    Joined: Jun 2009
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    baeckmo Hydrodynamics

    Nope, they don't. Teddy D has referred to the Sabb arrangement, which has a solid shaft and the propeller hub is fixed with its own bearings, including thrust bearing. Pitch is adjusted by moving the shaft lonitudinally. Your patent sketch is in reality a copy of the existing Sabb arrangement....nothing new there!
     
  6. JSL
    Joined: Nov 2012
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    Location: Delta BC

    JSL Senior Member

    I have seen something like this before but forget the brand.
    I was called in to solve a suspected speed anomoly on a 40' sailboat. They had put a CV joint on the shaft with its own thrust bracket. The bracket was a bit flexible so as the thrust increased with rpm the shaft moved for'd a bit, therby reducing the pitch... and therefor the boat speed.... all the while absorbing horsepower. Top speed was about 4 knots. Once the thrust plate was 'stiffened up' the speed jumped to about 7 knots.
     
  7. pdwiley
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    pdwiley Senior Member

    Completely wrong.

    As I have a Sabb 16HP engine with CPP on my bench, I can speak with considerably more authority on this than you can.

    PDW
     
  8. TeddyDiver
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    TeddyDiver Gollywobbler

    The confusion of the OP is understandable. Sabb made the last solid saft CPP decades ago..
    Like most things mechanical there's not much new to invent which hasn't been invented during the last few centuries of industrialization. Just some things become rare and some are forgotten.
     
  9. pdwiley
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    pdwiley Senior Member

    Yeah - I spent literally years looking for one close to me. Finally found a 16HP model with ~1300 hours on it even though it's 30+ years old.

    I need a new thrust/cutless bearing for it as the previous owner wouldn't remove that from his boat. I can make one if I have to, though. I took some measurements off of the original one when I collected the engine.

    The Sabb design is really simple and elegant. I wish they still made them. As it is I settled for second best - a Bukh 36HP engine driving a 22" Autostream propellor.

    PDW
     
  10. baeckmo
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    baeckmo Hydrodynamics

    pdw, there are still most of the spares available here. Send me a mail with what you need and I'll see what is possible to scratch to the surface.
     

  11. pdwiley
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    pdwiley Senior Member

    Thanks, I'll do that when I get back home in 5 weeks or so.

    If I'd found a 30 HP unit I think I'd have been pulling the g/box off of the Bukh and installing the Sabb g/box and propellor. The 16 HP unit is just too small for my boat (or I think it is anyway). I may make up some bigger blades one day though but I can't take it too far. It'll be a very nice engine to fit to a small motor launch at some point.

    PDW
     
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