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Krazed Builds 2.2S Pneuma

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  • Krazed Builds 2.2S Pneuma

    So the cats out of the bag on our latest Capra axle based 2.2S build. After seeing how well the Alcista handled with Capra axles we decided it was time to sit down and really design a comp version of our next Shafty chassis kit to come.

    We took everything from our notes on our 2018 Nationals Portal rig and did some deeper digging into geometry and our math. Again I will say Axial nailed it with these axles. I loved the portal rig I built prior to this and learned so much from it and from talks with some great OG comp guys. The few things I battled with that rig I started educating myself more on. Understanding geometry and the real engineering side of our little trucks and the evolution of crawling .

    My main goal was to design a new chassis able to win with our conventional older axles while benefiting from the newest type being portals. First I must say the myth of portals raising your COG I believe to be just that, a myth. Let me explain my thinking.

    Lets take our past shafties and sit the truck on our bench. Now Im gonna use measurements loosely but lets say we have a belly that sits 3'' off the ground. Our axle centers are 2.5'' off our bench with tires on. Now most people would say well you raised everything up because you raised the axles so your COG rose.

    Wrong ..... Now lets say you lowered your belly a half inch on the same truck. Did you raise or lower your COG? Most would agree you lowered it because you brought the chassis/trans closer to the axle center right? Now lets say you kept your belly at 3'' and raised only your axle center (not the wheel center) a half inch. So yes you brought axle weight up but now look at all that room you have 'below' the axle center to add weight.

    Before you only had 'loosely' a half inch of room to add weight below the axle center. Now you have a wheel center thats a half inch lower then your axle center. Virtually doubling the distance now with portals that you can get weight below the 'axle' center. I will say I define 'axle center' as your axle/ring n pinion gear and Not the stub axle your wheel rides on. When you add in the portal gears you have more weight to begin with below the axle.

    So in my theory Im able to stack upwards of 157g per side with loaded dice wheels, upwards of a crazy 255g per side with rock magnet hangers. All that weight is farther from the axle center then able to be before. This lowers my COG since I didnt move the chassis up, I only moved the axle housing and corrected some geometry restrictions we had before.

    Crazy? Ya im no 'engineer' that can mathematically explain it but just let that ponder.

    Now with that theory and my experience from the last rig I knew I had my notes right. Measuring everything out and running ideas for my goal in this chassis I came up with this which became 3 prototypes.

    Believing in 3D printing and have been doing it for a couple years now all our skids come printed in PETG.

    For my own personal I went to try some real carbon fiber PETG material for printing. Strong and a bit lighter.

    For my own rig I went with my own transmission and 23% internal overdrive for the front axle. I will say I wont be producing these though, theres just too much work and theres plenty of reliable options already out.

    Ive been testing with my own truck for quite a bit lately and must say it feels good driving a shafty again. Especially this one that is just above anything Ive driven over the years. But after some talks with another team driver and some talks with a some OG drivers I made a couple geometry changes and so far loving the effects of them. And here I am now with our newest prototype for some more testing.

    I also went to the front axle with a strong servo and electronics plate that cleared the upper links and not printed.

    So there it is ..... We are calling our 3rd generation shafty chassis 'Pneuma' meaning the vital spirit, soul, or creative force of a person. Now we arent looking to replace the Alcista or believe any less in it because of the Pneuma. The Alcista really is a way to wake up a Capra for drivers looking to try the competition side of crawling. We believe in the hobby and ways to attract new blood with out breaking the bank. The Pneuma is our dedication to the drivers looking for that upper edge over the older, past thinking of shafty rigs. More testing and practice this friday and hopefully some good video for it.

    Thanks for looking .......

  • #2
    Heres some basic setup info Im running with right now.

    Servo: Hitec 7950
    ESC: Holmes BR Mini
    Motor: Holmes Puller 500
    Battery: 3S 500mah
    Tires: Rover white rear - Rover Pink front all shaved and softened up
    Foams: Crawler Innovations 5.25 Med rears/Soft fronts

    Shock Oil:
    Front: 37.5
    Rear: 42.5

    Front: Element Greens
    Rear: Element White

    Truck RTR Weight: 4.13lbs

    Hot Bodies Front OD AR44 gear
    Trans OD: 23%

    Front knuckle weight: 74grams per side (rock magnet hanger + 1 tungsten slug)

    Body: Jconcepts Illusion Mini E-revo body (have bubble roof to help with roll overs)


    • #3
      Ohh almost forgot some weight pictures for comparison. Although I dont use the scales much for crawlers its always neat to see how close to balanced they are.

      This is my Daughters Alcista conversion
      60% front bias and 50/50 corner to corner

      My Pneuma
      65% front bias and 50/50 corner to corner

      My 5th Dimension Dominator Pro (which looks like it needs a diet lol )
      65% front bias and 50/50 corner to corner

      Just food for thought when rigs hit the scales


      • #4
        Took little video of some practice time the other day.


        • #5
          Playing with some gearing ideas. So portals gave reduction ... our normal trans always had reduction .... and now I'm digging for wheel speed.

          What if .... I try some speed in the trans? So I came up with something able to get me from 11:1 up to 8.33:1 and threw some carbon on the machine.

          So far I'm happy with what I'm seeing in the trans. Much better wheel.speed, no stalling on a 16t pinion and even better, no motor heat. Plus i still ha e room to drop pinion teeth if needed.

          Couple shots of what i came up with.

          PSA: love the new forums, so clean and easy even to upload and view from Mobil phone.

          Sent from my SM-A600P using Tapatalk


          • #6
            Looking good man, hope I see it on the rocks next weekend.


            • #7
              Originally posted by BCBrian View Post
              Looking good man, hope I see it on the rocks next weekend.
              Thanks - Im hoping, trucks are running incredible lately.


              • #8
                awesome build

                what gears do you use inside the transmission?