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1/32nd Direct Drive

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  • 1/32nd Direct Drive

    I have recently attended a couple of IHRS (Interstate Home Slot Racers) events, held in Maryland and Pennsylvania. The IHRS races 1/32nd scale cars, which is a bit different for me. I have been primarily an HO racer, when I raced at all.

    I did race 1/32nd scale sprint cars for a couple of years back in the '90's. That ended when the racing center burned down.

    IHRS has an 'unlimited' class, which I plan to participate in. Nothing like ditching the rules and building whatever you want to race.

    For me, that includes two direct-drive chassis. The first will be a single-motor lash-up of brass and piano wire. The rear wheels will mount directly on the 2mm diameter motor shafts of a R&H 'Jack Rabbit' motor. Said motor is not high-rev, but is high-torque. Just the thing for direct-drive.

    The second chassis will take that 'unlimited' description to an extreme. It will feature TWO motors set up for direct-drive, one front, one rear, all mounting aggressive rubber. Because, why not?

    Now I am well aware that twin-motor chassis have been tried before, both in 1/32nd and 1/24th scale, with lack-luster results. And I think you have to go back to the 1960's to find any slotcars with direct drive. I'm pretty sure Eldon made some back then. So why am I scavenging failed concepts from the past?

    People who know me have the answer for that. I have a history of making nutty concepts work. I have produced direct-drive cars in HO scale with notable success. I see the potential to make it work in 1/32nd scale too. Modern slot motors with rare-earth magnets could very well have the torque required.

    So I have gathered up the parts I need to build those two chassis. I have tracks I can test them on. All I need now is some serious fabrication time. We'll see just how nutty my ideas are.

    Stay tuned!
    Ed Bianchi
    Last edited by HO RacePro; 11-09-2018, 10:22 PM.

  • #2
    There is at least one direct drive 1/32 on the market these days. JK have had a direct drive chassis and a motor called the Hawk DD to suit. Direct drive does need reasonably long motor shaft at both ends. The Hawk DD does have unusually long shafts out both ends of the motor. Direct drive also needs the right size wheels to fit the motor shaft, fortunately 2mm is a very common shaft size in 1/32 and 1/24 slot motors and 2mm axles is one of the standard sizes for which wheels are available.


    • #3
      Thanks for the tip, Al!

      Here is a link to the JK page for direct-drive products: *********************

      The chassis is designated the 'C10', with the center sub-frame available as the 'C10C'. A full-up running chassis is available as the '017', equipped with the M20 motor.

      There are several pages of Ready-To-Run cars with detailed vacuum-formed bodies -- sadly, with no pictures as yet.

      Anybody have experience with these products?

      Ed Bianchi
      Last edited by Wet Coast Racer; 11-16-2018, 05:08 PM. Reason: Rule 13, it's very clear. Anybody can look up JK using Google.


      • #4
        There is some write-up(s) on the JK direct drive cars, I "think" somewhere in this board, maybe others.
        Just start digging..!

        As I recall reading, while they were a little sluggish (as can be expected) at low speeds, overall, they were fast enough and fun to drive, "for...what they are".

        I was going to give one a try, never did.



        • #5
          The JK C10 is based on the much more widely used C1 and uses the same body pan pressing as the C1. Pretty much the entire range of JK's 1/32 sports car type bodies will fit, as will a vast range of 1/32 sports car bodies from other manufacturers. The JK web site has several pages of photos of 1/32 bodies starting at


          • #6
            The direct drive chassis for reference.


            Last edited by Wet Coast Racer; 11-16-2018, 05:06 PM. Reason: Rule 13


            • #7
              What's your plan here, Ed? A track car, or a dragster?

              If you haven't noticed it before, there's a lovely bit of tractor pulling multi-motor madness to be found here.


              • #8
                A track car and/or oval racer. For now.

                The whole Land Speed Record business dates back at least two decades. I was fantasizing about building an LSR track, as described above. Well, more than fantasizing, since I built a prototype big enough to be a 1/4 scale mile drag strip. The fantasy was that I'd find a location big enough to set it up and host a national competition.

                Here's the interesting thing -- money wasn't the issue. I'd worked out what the track would cost, and I could handle it. The issue was where to set it up and where to store the track before and after the event.

                I thought seriously about selling off the track in drag-strip-size lengths, post-event. Then building a whole new track if the event were to be held again.

                The connection between direct-drive slotcars and the Land Speed Record is that I am convinced a direct-drive car would have the best chance of winning said event.

                Ed Bianchi


                • #9
                  Wow - a serious land speed record attempt.

                  For sure the rear wheels are going to need to spin quickly to achieve a land speed record.

                  The fastest straight line speed slot cars achieve in regular racing seems to be about 135mph for dragsters. Guess a meaningful LSR is going to need to be faster than that.

                  Quick back of an envelope calculation shows a one inch diameter tyre doing 47,000 rpm works out at roughly 140mph. With direct drive you'd need a motor that free runs way above 47k.

                  Of course slot motors are available off the shelf that can rev way past double that, one of those with 2 point something to 1 gear ratio would be an alternative to direct drive.


                  • #10
                    Custom pinions and or spur/crown gears to get to those really high ratios (overdrive even !?).
                    Then a high torque motor to get there.

                    Sounds like an interesting proposition. Would push cars be legal..? Mostly kidding.

                    As noted, finding rear tires to withstand the RPM would be the hard part of this whole thing.

                    Last edited by Mike-; 11-12-2018, 10:40 AM.


                    • #11
                      To get the maximum speed out of the motor you may want to go to a series-wound DC motor.

                      A series-wound DC motor has no permanent magnets. They are replaced by electromagnets -- coils of wire on steel spools. The magnets are wired up in series with the armature.

                      The neat and a bit scary thing about a series-wound DC motor is, if it does not have a load, there is no limit to how fast it can turn. No limit, that is, until it spins itself to destruction!

                      Permanent magnet motors all have a built-in top speed, determined by the reverse-EMF they generate. But with a series-wound DC motor the question is whether the car will reach the end of the LSR track before the armature explodes!

                      Now obviously the motor will have SOME load on it. The forces of acceleration and drag will provide the load. So there is a good chance the motor will never be in danger of scattering during the run. But guy, don't lift the rear wheels and run it!

                      I warned you!

                      Ed Bianchi


                      • #12
                        For a serious slot racing land speed record attempt, it seems rather unlikely that the sorts of slot car motors that have rpm ratings would be suitable. Faster permanent magnet slot car seem like a good option as they are already available and regularly run up to the sorts of revs you'd need. You could try series-wound DC motor if you like experimenting, I've seen examples of these in slot type cars from over 70 years ago but as far as I know permanent magnet motors are universal in modern slot cars

                        There's a vast choice of slot car motors that'll rev so high they'll self destruct if you are unwise enough to free run them on full voltage. That's the main reason the manufacturers never give rpm ratings for the higher reving slot car motors.

                        Properly balanced armatures are a prerequisite of really high revs and at land speed record speeds balancing the wheels is going to be important. Both are pretty standard for top end slot cars.


                        • #13
                          Aside from balancing, the wheels and tires need to be able to withstand the RPM's.

                          A wheel mounted directly onto a motor shaft will easily spin off a slip-on tire if run without a load. Bonded sponge-silicone tires will 'grow' due to the rotational forces. High enough RPM's might destroy such a tire.

                          If I remember right one real-life LSR car used metal wheels without tires. I think it was a jet car, so there was no need for tire grip to drive the car forward.

                          For a scale LSR event, without magnetic downforce, there may need to be a trade-off between adequate traction and tires capable of handling the G's.

                          Ed Bianchi


                          • #14
                            For sure you need tyres up to running at LSR speed, a good place to look is the fastest slot cars currently around - they already get close to the sorts of speeds we'd be talking about for an LSR car - for example Slot dragsters hit around 135mph and wing cars average over 80mph laps. Tyres that are glued, trued and balanced work at those sort of speeds.
                            The tyres used on slot dragsters certainly produce good traction!


                            • #15
                              I remember driving one of your scratch built, brass chassis, HO scale direct drive cars. You called it the "Rattler", if memory serves, with a Ford GT MK IV Lexan body - one of my all time favorites! We were running on one of the hand routed, braided, banked ovals that you used to bring to our Super Bowl Slot Car Show here on Long Island. I think you were keeping tabs on lap times and awarding something, maybe even one of the cars, as a prize to the driver with low E.T. for the day.
                              If his 1/32 car is as good as the HO model... watch out to the competition!
                              Good luck, Ed. -- Ernie :>)