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Last Call- Gear Up! Edition

Robert Emslie April 29, 2014 Last Call 28 Comments


After watching this morning’s fun little instructional video on Synchromesh you probably have gears on the brain. You are after all a gearhead, right? Here’s a handy-dandy little cheat sheet of various gear types and since we’re done for the day, consider this homework.

Last Call indicates the end of Hooniverse’s broadcast day. It’s meant to be an open forum for anyone and anything. Thread jacking is not only accepted, it’s encouraged. 

Image source: Go Away Garage


  • Scandinavian Flick ★
    • 3Mercedes124s

      You sir, have found a way to keep my attention for hours and hours. Fascinating.

      • Scandinavian Flick ★

        Mesmerizing, isn't it? It makes me wish I had the kind of mind that could come up with this crazy stuff.

  • Where's Top Gear?

  • Kris_01

    You want gears, check out the Simpson planetary gear set operation. It'll fry your brain.

  • <img src="http://mattysf.com/wp-content/uploads/2013/04/CA-Mille-Ferrari.jpg&quot; width=600>

    Well it's California Mille time again! They should be rolling through San Francisco and into Sausalito on Thursday.
    <a href="http://www.californiamille.com/index.html” target=”_blank”>http://www.californiamille.com/index.html

    • vwminispeedster

      And once again I forgot the date it was happening. And its only 5 blocks from my office. Try again next year.

      • Today! I think in about 8 hours from this reply.

  • Marc

    What's the difference between a spiral bevel and hypoid gear? The location of the pinion gear?

    • Yup. The hypoid arrangement has the axis of the pinion shaft offset from (not intersecting) the axis of the ring gear.

      I didn't know that until I saw this post, though. I had to go look it up; I dropped out of Mechanical Engineering before they got to that.

      • HTWHLS

        thanks, I was going to ask the same thing.

      • Gears are way to practical to learn in Mechanical Engineering school. That's one of those things you just have to sort of figure out once you get a job or buy a Machinerys Handbook.

        • That's exactly what I did! How did you know?
          I got a job, earned some money, rolled around in the Starrett catalog like a pig in shit, bought a used Kennedy toolbox to keep the Machinery's Handbook in and showed up at the next job looking like I really knew my shit.

          The student loans were nothing compared to the investment in really nifty measuring devices. Much more satisfying to pass a precision level on to the next generation than a loan debt.

    • nanoop

      Calculating is more demanding for the hypoid, as rack and pinion are gliding a tiny bit on each other. The touching area is larger (less pressure on the teeth/surfaces) and hence survive higher torque for a given material pairing, they run quieter, and the location of the pinion may allow for more compact designs.
      In former times, this gliding demanded for special oils, and you can still buy "transaxle oil" today, but a close look at fwd cars will reveal that they can have hypoids, too, but don't demand a special lubricant – whereas the 944 gearbox, actually a transaxle, is from an Audi fwd, but runs with regular gear oil, too.
      [Disclaimer: oil, both for engines and gearboxes, is discussed religiously across all kinds of forums mostly by people with hours invested in research = 0 and number of samples = 1. I'm not going to discuss somebody's beliefs.]

      • HTWHLS

        Word! I did that once…never again!

  • There are also offset bevel gears with strait teeth. They were used in the 19th Century until the more efficient Hypoid shape was developed. One example of their use was on geared steam locomotives, where they allowed a drive shaft to connect multiple axles while crossing at an offset.
    Here is a picture of a model of such locomotive built by a friend of mine. The whole project started when he located those gears in some surplus store…
    <img src="http://www.wegmuller.org/trains/friends/IMGP0353.JPG"&gt;
    <img src="http://www.wegmuller.org/trains/friends/IMGP0355.JPG"&gt;
    <img src="http://www.wegmuller.org/trains/friends/IMGP0350.JPG"&gt;

    • RegalRegalia

      Thanks, this is really cool. What a fun project that had to have been.

  • Honda's VF500F Interceptor had a very compact and wonderfully functional planetary gearshift mechanism. I've always thought it was very cool.

    <img src="http://i.ebayimg.com/00/s/MTIwMFgxNjAw/$%28KGrHqVHJEIE88cr4tFRBPcb7nbqog~~60_21.JPG"&gt;

    • RegalRegalia

      Thanks for sharing a planetary application.

  • RegalRegalia

    One of the best last call posts I can remember, thanks Robert and everyone who's commented.

  • Marto

    Ok bear with me here, I am in no way a mechanic…

    What if you used a planetary gearset between your input and output shafts.
    The input shaft would be inside and would mesh with the little planetary gear.
    The little planetary gear would be free to rotate on its axis and in orbit around the input shaft within the larger gear.
    The outside planetary gear would be the output and connected direct to the wheels.

    Now, if you applied various degrees of braking (clutch?) to the little planetary gear – would that create a constantly variable transmission?

    That is, would the combined orbit and rotation of the small planetary gear – governed by the braking applied to same – translate to various degrees of torque and speed? Or would it all be driveline loss?

    I am sure this has already been invented a zillion times, I just don't know what the set-up is called.


    • Marto

      To clear up:

      If the output shaft would not budge, the little planetary gear would just rotate on its axis while also orbiting the input shaft. And if there was braking involved in that instance, it would just burn the brakes.

      If the output shaft was spinning freely (i.e. no load) the little planetary gear would not rotate on its axis at all, but it would orbit between the input and output, giving a 1:1 gear ratio.

      • skitter

        Conceptually, you are on the right track. However, slipping a friction clutch constantly will quickly wear it out/burn it up. If you use another braking mechanism such as a fluid clutch (think torque converter), you're still turning a lot of energy into waste heat just to get the speed right. If you use an electric motor/generator to control the drag/power to a planetary set, you have a Prius drivetrain, which can be made to work pretty brilliantly.

        • Marto

          Cool! And now I sort of understand hybrids drivetrains? Thanks for taking the time to read and explain Skitter? 🙂

          • Marto

            My iPad put in all those question marks. 🙁

            • Rover1

              Marto, are you still in NZ?

              • Marto

                Yes, until July.

                As for my upcoming roadrrip, I have been talking to a scooter dealer in Cairns, Australia.

                He recommends I buy the SYM Jet 4R for about $2300. Don't really want a brand new one though. Anyway, then I'll need windscreen, helmet, gloves and luggage boxes. Then swag and satnav.

                And the dealer recommends to run it in for 300km. So, I'm thinking I'll mosey even farther north, up to the end of the road: Cooktown. Then I'll turn around and mosey all the way back to the Gold Coast: 1200 miles down the highway. But I'm not taking highways…

                • Marto

                  Also, I just realised I might need to clarify for American readers: in Australia a "swag" is word meaning a waterproof tent/bedroll. Very commonly used for lightweight campers and cattle musterers, etc.

                  Like this: http://cache.gawkerassets.com/assets/images/4/201