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Thread: CVT-PRSU what do you think?

  1. #21

    Join Date
    Oct 2011
    Posts
    17

    Where to go next

    What is needed is either test data or a good mathematical analysis. Anything else is opinion. Since I lean toward hardware, I will try to develop some data.

    Vince Homer

  2. #22

    Join Date
    Oct 2011
    Posts
    3

    CVT-PRSU what do you think?

    Quote Originally Posted by Vince View Post
    Removing the variable feature kinda defeats the purpose
    Did you read my msg, above? There are multiple possible valid 'purposes', each one has its adherents.

    the flyweights actually weigh only a few onces.
    Ounces make pounds. And I listed a few more parts than that. You don't know how much weight we could lose, I don't know either.

    I'm sure that a cog belt PSRU would be more efficient than using a locked CVT.
    Yes, and I am sure that is true also. The whole point here is lost if you keep picking at small things. The point is that there is more than one reason to use a CVT PSRU. Some reasons may not be important to you but they might be to the next guy.

  3. #23

    Join Date
    Sep 2014
    Posts
    1
    I like the idea of using a CVT for a PSRU for the falling reasons. The hp curve for an engine is convex, where as the hp required for a propeller is concave. This means that they can only match at one speed. When you back off the engine to let’s say 80% rpm the engine is still capable of slightly over 80% hp. But the prop only can use 50% power. This leaves the engine very lightly loaded. 4 stroke engines don’t like this and 2 stroke engines positively hate it.
    The CVT will keep the engine properly loaded at all times.
    So in by using a CVT for your PSRU you would need a propeller tack and back the propeller to 80% rpm which would bring the engine down to near 50% rpm.

    Attached Images Attached Images  
    Last edited by d-omber; 10-25-2014 at 02:47 PM.

  4. #24

    Join Date
    Oct 2011
    Posts
    17

    CVT Test

    I have a rolling test stand that does exactly what d-omber suggests. It has 16 HP engine driving a go cart CVT which drives the prop. The engine runs at 3600 rpm no matter what prop or prop pitch is hung on it. For example; I have a 54 inch prop that turns at 3200 rpm in fine pitch and 1600 when in coarse pitch. Essentially what the VCT does is to lay the engine torque curve onto the curve of propeller torque over the operating rpm range of the engine.

    I have a PP presentation on this, but can't seem to figure out how to attach it to a post. Is it possible to make files (Power Point, Word, Excel) available on this forum? If anyone is interested I can send the file through email: vhhomer@hotmail.com

    Vince Homer

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