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Dynam prop adapters

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  • Dynam prop adapters

    Just curious. My Dynam Waco came with an 8mm diameter prop shaft adapter, while I've noticed looking online, that 6mm is more typical for wooden props. Looking at the replacement adapters on MRC's page, they don't tend to list shaft diameter. Is there one of the 4 bolt adapters that will work with the Waco motor that has a 6mm shaft, and will work fine on the Waco?

  • #2
    Prop makers default to drilling for the smallest shaft they expect you to want to put the prop on, then you are expected to drill them out or use a "reamer"


    You can also use a tapered reamer.

    with any reamer, start at one side and make the prop go about halfway onto the shaft, then ream out from the other side until the prop just slips on the shaft.


    Note: Dynam has started putting "keying" ridges on spinner backplates to go into slots in the props. This is good and bad. To use an aftermarket prop you need to cut these ridges off. .They work VERY well to help you hold the prop shaft still when tightening the prop nut (using the OEM prop for the model)

    I like the looks of the XOAR scale wood props on many models.
    FF gliders and rubber power since 1966, CL 1970-1990, RC since 1975.

    current planes from 1/2 oz to 22 lbs


    • #3
      I drilled the wooden prop from a 6mm hole to an 8mm, but just wondered if I could change the prop adapter and not have to worry about it. That said, it's simple enough to enlarge the hole.

      I did start wondering today what the difference is between gas and electric props. When I was browsing the selection of Xoar props online, I noticed they separate the electric props, and the Master Airscrew I picked up today is labeled for electric. I had the mindset that the propshaft spun the prop, and it really didn't matter to the prop whether the motor spinning the shaft was gas or electric. The prop just spins and produces thrust. Apparently, since these things are made by people with a heck of a lot more experience than I have, it must be a bit more complicated than that.


      • #4
        Gas props have to be stronger to withstand the cyclic acceleration/deceleration of the gas/glow engine.

        The prop partially acts as a flywheel to carry the engine through the exhaust, intake, compression portions of the cycle. During these (especially compression) the engine is acting to slow the propeller, Only during the combustion phase of the cycle is the engine accelerating the prop.
        This would snap the blades right off of most electric props. (usually in the combustion phase)

        Electric power is far smoother with no hard deceleration (compression stroke) and especially with brushless, many small acceleration periods per rotation.
        FF gliders and rubber power since 1966, CL 1970-1990, RC since 1975.

        current planes from 1/2 oz to 22 lbs


        • #5
          So, if I surmise correctly, about the only problem with using a "gas prop" on an electric, is that the prop may be a bit heavier than needed.

          One of the guys out at the field this morning made some comment about not realizing anyone was making wooden props for electrics, which almost made it sound like he didn't think a gas prop would work.

          The nylon prop that came with the Dynam Waco weighs 26 grams. The Top Flite wooden prop of the same diameter and pitch weighs 16 grams.


          • #6
            Mostly correct.

            The electric props are thinner, lighter and more efficient. The airfoils used give better thrust for less load on the motor.
            FF gliders and rubber power since 1966, CL 1970-1990, RC since 1975.

            current planes from 1/2 oz to 22 lbs