RFQ 2 ea. main bevel gear and matching pinion bevel gear - Page 2
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  1. #21
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    Folks please don't waste any more time on this. I have discovered lots of errors in the Main Gear file and it looks like I'll have to generate it again from scratch. I apologize for the inconvenience.
    SD

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    Perhaps get the manufactorer involved in the design

    Peter

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    Thank you Peter. I'll try to keep things stateside for now.
    SD

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    Quote Originally Posted by saucerdesigner View Post
    Folks please don't waste any more time on this. I have discovered lots of errors in the Main Gear file ....
    Doesn't really matter for a quote. It's always going to be expensive because bevel machines take time to set up.

    1) A couple hours to figure all your settings
    2) Four hours to set up for roughing
    3) Build a holding mandrel
    4) Rough first part, check it, if wrong adjust
    5) Rough the teeth
    6) Change over to finishing, two hours
    7) Finish teeth on first part, then check, preferably in a rolling tester
    8) Adjust to get the contact where you want it
    9) Finish teeth on the remaining parts

    Have to do this for both pinion and gear. As you can see, there's some time involved. For this number of parts, profiling in a mill probably makes better sense.

    Also, by milling you could just as easily do spiral or skew bevel. Plastic teeth really want to have a contact ratio over two and they also like a full radius in the root.

  5. #25
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    11" dia Delrin gear running at 6K RPM? 30K pinion? lube is going to be? That's quite an RC model. Pretty straight forward for a straight bevel gear pair, but the pitch line velocity will be over 18000 ft/min! Did I miss something?

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    EG, any thoughts on the wear aspect of Al against Delrin in an application like this? Especially at the design speed...

    I'd wonder if a larger, courser pitch propeller meant for lower speeds might not work better, allowing more robust, lower RPM gearing.

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    I forget where but i was reading about a 6:1 helical gear for a helocopter. 1 inch wide 6inch diameter on the plastic driven gear. Something like 6 or 10 horsepower load.

    The aluminum pinion and the plastic gear were both profile adjusted to account for the difference in stiffness.

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    Quote Originally Posted by Milland View Post
    EG, any thoughts on the wear aspect of Al against Delrin in an application like this?
    Nah, at the designed 18,000 ft/min pitch line velocity the delrin will melt down in about 15.7 seconds. That should be just enough to get this thing far enough off the ground to do some real damage when gravity takes over

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  11. #29
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    So we're basically at put a dang motor out there with the prop and forget about gearing...

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    Quote Originally Posted by Dan from Oakland View Post
    11" dia Delrin gear running at 6K RPM? 30K pinion? lube is going to be? That's quite an RC model. Pretty straight forward for a straight bevel gear pair, but the pitch line velocity will be over 18000 ft/min! Did I miss something?
    I don't think the Hughes 269c 2 place chopper has that big of a ring gear....
    Hughes TH-55 Osage - Wikipedia

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    Matched pair.....
    DP-14 Multi Mission UAS - DPI UAV Systems

    Might be direct coupling the Turbine engine output shaft to the pinion.

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    Quote Originally Posted by digger doug View Post
    Matched pair.....
    DP-14 Multi Mission UAS - DPI UAV Systems

    Might be direct coupling the Turbine engine output shaft to the pinion.
    A quick look at the video still makes me think direct coupling is unlikely. The orientation of exhaust and casing looks to be at right angles to the props, and besides, no small turbine is going to run slow enough for direct drive unless you define that as having reduction gears integrated into the turbine casing.

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    Quote Originally Posted by Milland View Post
    A quick look at the video still makes me think direct coupling is unlikely. The orientation of exhaust and casing looks to be at right angles to the props, and besides, no small turbine is going to run slow enough for direct drive unless you define that as having reduction gears integrated into the turbine casing.
    NO, not THAT one, I am thinking the OP is trying to doo direct reduction in one shot.

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    I have corrected the main bevel gear screw-up and now the inside diameter is as it should be. The old files have been removed.
    I really appreciate the comments, especially regarding concerns about Delrin in contact with aluminum rubbing, a material suggestion, a call-out for tooth surface roughness, a question about lube and the concern about pitch-circle velocities.
    The motors to be used in this twin-motor device are those powering a single-motor 450 size RC heli turning at the same RPM but what I had not considered is that the gears in those are much smaller, hence much lower pitch-circle velocities. I'm learning. At any rate the files are now up on the repository in a different folder. This time I'll be sharing the files without the option for editing them enabled. It's very likely that I inadvertently nudged the objects myself in the creation of them. Soon I'll again invite you all to submit a quote and I'll share a link.
    Regards,
    SD

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    Quote Originally Posted by saucerdesigner View Post
    I really appreciate the comments, especially regarding concerns about Delrin in contact with aluminum rubbing, a material suggestion, a call-out for tooth surface roughness, a question about lube and the concern about pitch-circle velocities.
    Delrin on aluminum is no big thing, but what is kind of a big thing is the way plastic gears behave. That's a whole 'nother specialty, because the material is so flexible and doesn't act like steel.

    I'd be concerned about these even if they were carburized 8620 prperly lubricated (very light synthetic oil sprayed at the outgoing side of the mesh ...) straight bevels just aren't that good for this kind of thing. Then transferring the design straight across to a material that has specific and different requirements ....

    What's the transmitted load, by the way ? You need to know that to figure the contact stress on the teeth. That's kind of an important number.

    Maybe just get the cheapest price you can because when the teeth melt and the thing falls out of the sky, at least you won't have spent as much.


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