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  1. #1
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    CVT - Continuously Variable Transmission

    I have been thinking about a multiple speed drive/tranny and think this would be the simplest set up if I could find or make on.

    Has anyone messed aroung with or know of any RC that use a CVT - Continuously Variable Transmission via mini v belt drive?
    This give anyone any ideas.

    Tony - StampedeProject
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    Bashing on a budget is and excersie in temerity. Ultra-Pede & Ultra-Rusty. Now the Tri-Pede.

  2. #2
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    well now that is very interesting.....

    justin

  3. #3
    RC Champion jtcfanof3's Avatar
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    Well on the old Tamiya Blackfoots they had an optional belt drive,but man thats been soooo many years ago I forget all the details about it,but kool animation!

    http://cgi.ebay.com/Tamiya-Frog-Blac...QQcmdZViewItem
    "Freedom is never more than one generation away from extinction. We didn't pass it to our children in the bloodstream. It must be fought for, protected, and handed on for them to do the same."
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  4. #4
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    I think I migh tbe able to make one..

    I am thinking 4 mini- slipper plates some springs, a belt and some chewing gum...

    Something to think about though.
    Tony - StampedeProject
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    Bashing on a budget is and excersie in temerity. Ultra-Pede & Ultra-Rusty. Now the Tri-Pede.

  5. #5
    RC Champion jtcfanof3's Avatar
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    Re: I think I migh tbe able to make one..

    Originally posted by stampedeproject
    a belt and some chewing gum...

    "Freedom is never more than one generation away from extinction. We didn't pass it to our children in the bloodstream. It must be fought for, protected, and handed on for them to do the same."
    Ronald Reagan

  6. #6
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    For an electric car, that would be preety heavy, and you wouldn't get as much out of a 2 speed as you would in a nitro. Keep thinking though




    Ethan
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  7. #7
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    he is thinking Macgyver style

    justin
    Last edited by joostin240; 03-02-2006 at 07:58 AM.

  8. #8
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    Originally posted by skylark
    For an electric car, that would be pretty heavy, and you wouldn't get as much out of a 2 speed as you would in a nitro. Keep thinking though

    Ethan
    I think you are missing the concept a bit.

    CVT are a little different. A CVT is continuously variable meaning infinite gearing at any point between the lowest gear and highest gear so that it is always optimally geared. The diagram shows the highest and lowest positions and skips everything in -between. In theory for instance, you wouldn't need to change gearing for rock climbing or high speed, the cvt would automatically gear as appropriate.

    So the idea is that at start the CVT in in the lowest position gearing, as speed increases and the need for torque decreases the belt move automatically to toward the higher gear, if you slow down is moves back down to the lower position. High speed through tall grass where it needs some torque as an example would automatically moves to let's say some mid point gearing, high speed on the street it would move to the highest gearing. In theory this could allow the Stampede or Rustler for that matter to obtain some seriously high speeds but still maintain insane torque for wheelies with a relatively modest motors all while delivering very linear power. Your could really clean up on the track.

    The advantage of a CVT is that it always operates in the highest torque curve of the motor which is where the motor is usually the most efficient.

    Additionally, it shouldn't be any heavier than a regular multi-speed tranny in fact in practical use they are usually considerably lighter. Faster acceleration, better fuel/power efficiency. These are some of the reasons it is now being used in lots of stuff like scooters to cars.
    It's also simpler and cheap.

    How to actually set one up on the Stampede has been keeping me up at night though.
    Last edited by stampedeproject; 03-02-2006 at 12:32 PM.
    Tony - StampedeProject
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    Bashing on a budget is and excersie in temerity. Ultra-Pede & Ultra-Rusty. Now the Tri-Pede.

  9. #9
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    Now, don't get me wrong: I think the idea is great and I'm sure you'd have a blast building it...but the little experiance I've had with CVT's points to the fact that real world performance doesn't match the theory.

    I'll explain: About a year ago, I helped test drive a small prototype, two seater buggy for a company my friend works for. The buggy had a 150 CC 2-cycle engine and a CVT trany.

    I was not impressed with the tranny at all. Even with one person in it, it had a pathetic amount of torque on take off, and top speed was still fairly slow. The buggy would have been much better off with a 6-speed manual (in fact, if they had just shoved a Yamaha Blaster engine and tranny in there, it would have been much better). It might have been a limitation due to the using too small of a CVT, but what the engineers had planned out, and what really happened were very differant.

    Also, I don't think a CVT would be a good idea for a nitro powered RC. If you give full throttle to a CVT powred vehicle, the engine revs up to max, then the CVT starts changing gearing. The buggy I drove had a rev limiter on it, so it was never a problem. With a nitro RC, I think you'd have a hard time not over-reving the engine.

    Like I said, I'm not trying discourage you building this, and I'd love to see it done.

    Fred

  10. #10
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    Honda used the CVT for a while in their Civics. I sold a few, but don't recall how they held up.

    Very interesting concept, the CVT.

    How about a rotary engine/CVT RC car??
    All those who believe psychokinesis raise my hand

  11. #11
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    I believe that Kyosho used a CVT for a short while back in the 90's on a nitro rig. I think it was available in a Pathfinder or something along that line. It was complicated and unable to handle large amounts of power. Supposedly anything other than the stock motor would cause it to burn up.

    I think that for RC purposes a CVT will only work great "in theory". The fact is that with a decent motor and one, ideally two, gears you can have all the torque and speed that any drivetrain can handle. A CVT would need constant readjusting every time you changed motors/gearing/tire sizes to perform to it's potential.

    Theres nothing really wrong with a CVT, as virtually every snowmachine and tons of ATV's are running around with them without any problems or performance drawbacks. They are also becoming more popular in fullsize autos, but, with only a few exceptions, they are limited to low torque and/or lighter vehicles.
    It sure seems like sense is no longer common.

  12. #12
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    Like you said, it would weigh about as much as a 2-speed. Obviously a 2-speed gives better excelleration. If the weight of the 2 speed wasn't too much to get good performance out of a 2-speed tranny, you would see them in electric cars. Plus, electric cars don't really need help on the bottom end, because electric motors have much torque down there. They need help on the top end.
    We don't see multi-speed trannys in electric cars because:
    1.Weight outweighs the benefits.
    2.electric cars don't need help accelerating. They need help hitting high speeds with weak top-ends.

    Hey, don't get me wrong, I am not trying to shoot ya down, but only to help show the problems.


    Ethan
    Detail is everything!

  13. #13
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    All really good points

    This is why it threw it out there. Though some people might has some insight and opinions on this.

    Although I know it will add extra weight, has anyone (recently) fitted the Stampede or the Rustler with a multi-speed tranny.

    Perhaps some stock setup from someone that can be "fitted" to the Stampede.

    I am fishing here but, I would imagine that this is why everyone eventually goes to a brushless setup. From my understanding brushless setups kind of negates the rational for a second speed due to the extreme RPM capable. Any comments on this?
    Tony - StampedeProject
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    Bashing on a budget is and excersie in temerity. Ultra-Pede & Ultra-Rusty. Now the Tri-Pede.

  14. #14
    RC Champion jtcfanof3's Avatar
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    Re: All really good points

    Originally posted by stampedeproject

    I am fishing here but, I would imagine that this is why everyone eventually goes to a brushless setup. From my understanding brushless setups kind of negates the rational for a second speed due to the extreme RPM capable. Any comments on this?
    You caught a whopper on the line,your dead on!
    Awhile back everyone was all hyped up about that NOVA 2 speed from HiIQ off ebay,but it was poorly enginered and customer service was no exsistant.But then came along BL systems which basically made a 2 speed pointless on this type of R/C.
    "Freedom is never more than one generation away from extinction. We didn't pass it to our children in the bloodstream. It must be fought for, protected, and handed on for them to do the same."
    Ronald Reagan

  15. #15
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    I dont know if a CVT will ever work in a pede, but looking at that picture makes me want to go snowmobiling . Now if we only had snow.

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