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Austin's SCX 61820 Dome Judd

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  • Austin's SCX 61820 Dome Judd

    First a look from the out side



    Did you see the new style case that the SCX 61820 Dome Judd Lammers #15 comes in. What a nice display, unlike the Scalextric and Ninco cases the bottom will not fill out letting your car fill to the floor. There is a nice easy to push in button on each end to release the cover. I just removed it and I am looking down on the car. I am too overly in love with the Black and white adds all over the car but thatís the way it was raced. All the print on this car is very clear and readable. The sun is shining in the window and making the car sparkle.



    Now to take it off the stand, do I really want to? Letís take a dime and turn the fastener. Ok something just went flying, letís stop and check it out. It was only a small peace of plastic on the bottom of the case. The car is off and looks like it can be placed back on easy.


    The car weights in at 78.1 grams. Front tires feel hard and are grooved. I will have to check and see if this car was raced with slightly grooved tires? The front axle spins very freely and no signs of any tire rub. The rear tires are slightly grooved and are soft to the feel. My finger don't want to slide across the grooved. Turning the tires by hand the gears feel a little rough. The floating rear motor and axle setup is very free. This should be great for non-magnet racing. The are no signs that the rear tires will rub at any time.



    The self centering guide is easy to turn plus has I slight down force that will help hope it in the slot and hold pressure on the contacts The head light lenses look be to very will in will. Donít you hate it when you loose on of these! I pulled on the mirrors and they seen to be very solid. Now lets check the leakiest part of a LMP car, the rear WING. At first look the wing seams to be angled so that it would lift the rear of the car. I will need the check race photos and check this out. The wing is held tightly in place as I can not pull it out. Will it break, well it is still the break point on this car, like all LMP cars.


    The drivers helmet is red, white , and blue. A black fire suit with a green colored harness, gloves are blue. There is no dash, but a nicely placed windshield and a black and sliver wheel.


    Update on the grooved tires, it seams that this car never ran grooved tires. This OK because it looks like that Sloi-it S1s all fit right on.

    Update on the rear wing, It is the same shape as many of the photos I came across.

    Inside this car is a brand new motor. Yes more power and more speed.

    SCX RX-41, 81, F1 13,500 RPM/14.8v
    SCX RX-6 16,500 RPM/14.8v
    SCX Pro Turbo, Plus, 4x4 18,000 RPM/14.8v

    The new RX6-2c Motor RPM's ????




  • #2
    It is a great looking car and almost all the faults can be fixed without too much work. The new motor is a big improvement over the old lump.
    Are we not happy that we entered this car in the RAA
    Wait till you see how next years model goes!
    Dan

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    • #3
      SCX Judd, a love/hate relationship!

      The new RX6-2c Motor RPM's ????
      19,700 at 14.8 volts, according to Slot Racing Yearbook.

      Funny you should post this right now Austin, as I just had the motor in my car melt down after no more than 50 or 60 laps. Up until then, it had been very punchy, and I had started tuning it up to run better on wood. Gearing had been changed from stock 9:27 to Slot.it 10:28, with the axles, wheels and tires replaced for truer, and quieter, ones, and I thought I was getting a handle on making this super looking car seriously quick on my track.

      Maybe I was just unlucky with that motor, as I notice that there aren't any drop-in replacements on the market; which will be fine if the next SCX one has the same power without the same problems!
      Last edited by Wet Coast Racer; 05-08-2006, 08:30 PM. Reason: Not telling

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      • #4
        West Coast, what bushes did you uses with the Slot.it axle? My SCX Merc also has the cradle and I want to replace the drive train but can not because of the bushes.

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        • #5
          Mampara , I don't understand your question. Are you talking about the rear axle bushings? If so they don't need to be replaced to use Slotit axles. My RAA SCX Dome (slow as it is this year) has Slotit axles, gears and hubs. It's sister has the stock hubs glued onto a Slotit axle with Slotit gears. Does your Merc have the motor pod with the magnet or is the magnet mounted in the frame. If the magnet is in the pod like the new Ferrari 550, you are in luck. Alot of motors will fit with just a little cutting and either a home built or store bought adapter from Slotit. I have four Audi R-8's set up with Carrera E-100 motors and I kill Scaly Lolas with them. If your car has the new motor with the real long pinion shaft then you could try the Ninco NC-7 Raider motor. I have two but I haven't put them in yet.
          Wet, I tip my hat to you. You smoked a SCX motor! I have tried but just couldn't get the job done. Have you tried running a new one in water for about 2 hrs. or so at 9v. The motor brushes need to be worn down by about a third and then the thing wakes up and runs so much better than right out of the box.
          Dan
          Ace Hobby Racing

          Comment


          • #6
            Question for yellowdog

            Hello yellowdog, Your suggestion for running in SCX motors got my attention as I have quite a few SCX cars. Mechanically I am a neophyte. How do you run in a motor under water? Is it really necessary to run it in underwater?
            Thanks, Spider V.

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            • #7
              I find running them under water for 2-3 minutes on a 9v works fine. The brushes wear very quickly under water. This does help the SCX motors a lot.

              Comment


              • #8
                No Spider, you don't have to run them under water but your cheap comutator will love you for it. I use a clean glass jar filled with enough water to cover the motor. Hang the motor in the water and put some voltage to it. When you'r done blow all the water out, oil the bushings and run it till it's dry.
                Dan
                Ace Hobby Racing

                Comment


                • #9
                  Hey Wet, I was just rereading your post about smoking a SCX motor. 10/28 Slotit gears? When I tried a 26t Slotit on my Dome it left marks on the body where it was rubbing. I had to grind a lot of plastic off the body in the gear grove and round off the edges of the gear. Slotit gears are bigger than the same size stock ones.
                  Dan

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                  • #10
                    I posted this elsewhere, maybe it belongs here:

                    These are no-load tachometer RPM readings from two motors I have here:
                    SCX RX-41 13,102/12v
                    SCX RX-62C 20,110/12v 24,230/14.8v [14.8v/12v=1.20]

                    More test results of some motors sent to me by a guy who requested info on the difference between his Turbo Plus and RX62C:

                    "The RX62C turned 20,218 at 12v.
                    The Pro Turbo Plus turned 20,340 at 12v.
                    These motors are essentially the same, as far as no-load RPM goes.
                    But the RX62C has a longer armature stack, which is often associated with higher torque.
                    Armature winding resistance for the Turbo is 1.9 ohms, and is 2.2 ohms for the RX62C. All other factors being equal, the lower resistance motor (Turbo) will draw more amps, run hotter, and will put out more power. However, the difference in power is probably minor. I cannot imagine why they produced two different motors of such similar performance, unless they just happened that way due to different production runs."

                    On the run-in business, you can run it under water for a few minutes, or you can run it in the open air for an hour or more to get the same effect. The water increases the wear, which is what you want. The water does not conduct electricity, very much, so the thing doesn't short out. You can also pull brushes out of an old SCX motor and use them in a new one, or vice versa. You can try increasing or decreasing the spring prsssure on the brushes by bending the springs or using double springs (if they fit). This is a standard tuning procedure for electric motors, as we did it in the old days. If you decrease the pressure, they start at a lower voltage but lose top end. If you increase it, they start at a higher voltage and gain top end, and gain brakes as well. In model railroading, we decrease brush pressure; in slot cars, we increase it. Sometimes the motors come from the factory with just the right amount of pressure, but not usually. You can also try grinding angles on the brushes to advance the timing, a common trick with the 16D series. You can can swap in 16D armatures, which may be an interesting way to get too much power.

                    Comment


                    • #11
                      Sometimes you think you're subscribed to a thread and then suddenly realize it weren't so. The more I look at my inert SCX Dome Judd chassis, the more cleverness I see in some of the design; I can see why some - the rtr entry in particular - are doing so well on some of the RAA tracks.

                      What bushes did you uses with the Slot.it axle?
                      Mampara, Dan is correct in observing that the stock spherical SCX bushes accept probably any 3/32" type axle; I think the limited amount of pinion protrusion into the Slot.it hub may prove a greater concern, given my recent experiences in the RAA which Dan corrected for me.

                      I was just rereading your post about smoking a SCX motor. 10/28 Slotit gears? When I tried a 26t Slotit on my Dome it left marks on the body where it was rubbing. I had to grind a lot of plastic off the body in the gear grove and round off the edges of the gear.
                      Dan, the motor smoking turned out to be my own fault. I used a couple of handy button magnets to clamp onto either side of the motor as an experiment in weight placement and apparently destroyed it in the process; not that it went any faster or slower than before, much to my regret now - I'm working on purchasing an identical replacement motor from the Canadian distributor, who don't seem to have run into this problem before.

                      As to gearing, I initially tried a 30t but that was raucous. The 28t was certainly making some interesting sounds at times when the car was running - and believe me, it was tuning nicely to the track - and I was already contemplating how to reduce the external diameter of this crown to reduce the friction a bit, cause I don't want to go down to a 26t if I can avoid it.

                      This car needs work, without a doubt, cause I don't like the guide either, but you know I think I can make it go quick and will try to update soon.
                      Last edited by Wet Coast Racer; 03-14-2006, 09:34 PM.

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                      • #12
                        I have found that the stock gearing is ok up to about 40' of track. After that you need to reduce crown gear teeth. I should have fixed my Dome while it was at Ace for the RAA. I thought I was OK because I was using the stock motor, but after they left I looked at my other stock motored Dome and saw that I may have the too short pinion shaft illness.
                        The problem with the SCX guides is that they will lift the front end of the car when you put the power down. If you are coming out of a cornor it will help you deslot. And when it is extended like that, it is real easy to snap it off. To fix the problem I push the guide all the way up against the frame and drill a small hole thru the shank as close to the frame as I can. I slip a short piece of wire thru the hole and bend it. Now the guide cannot move up and down. Now I adjust the front ride hight. I use Evergreen plastic strips. .080X.250" I think. Cut two pieces about 1/2" long and drill a .093 hole thru both pieces at the same time. Open up the front axle slot so the front end lays down on the guide braid. Pull one wheel off the axle ( thank you SCX for not knurling your axle ends) and slip the new uprights on and cut them down so they fit against the old axle carrier. When you have the lengths right scrape the paint off the frame and glue with Testors model glue. After this simple mod you can drive that car through the cornors a lot faster with out desloting.
                        Dan
                        Ace Hobby Racing

                        Comment


                        • #13
                          My RAA SCX Dome (slow as it is this year) has Slotit axles, gears and hubs.
                          Wasn't slow at my track; first of the LMPs that could do almost sixty consecutive laps all under nine seconds, wicked brakes too.

                          There have been a couple threads going about SCX Judds and Slot.it gearing, as well as the bushing question. By chance, my Slot.it 956 wore out its gear hub, as I had shortened the pinion shaft too much. This chassis, like the SCX Judd, uses spherical bushings. I suspect that this additional flex may also contribute to the problem.



                          Dan fixed this for me at the RAA Niagara race by replacing the worn out crown gear and adding fine inner spacers to the axle at each end to properly locate the drivetrain, particularly the gear mesh. This has resulted in it running quite a bit stiffer, but it's faster now by a couple tenths than when first tested on the home track, and the (now) relatively fixed positioning of those bushings doesn't seem to matter.

                          So it was ironic when his SCX Dome Judd developed basically the same problem; though it has the stock RX62C motor with a Slot.it 26t crown, which on the end of the long pinion shaft is very similar in setup, right down to the spherical bushings in what is actually a very flexible chassis, with a superb motor pod IMHO. Sorry these photos aren't so good.



                          So he sent me a set of spacers pretty much the same as he had used on my car, I put 'em in and swapped the gears and voila! As they say in the old country.

                          He even provided some genuine Yellowdog Grease!



                          So to my mind, this type of "fix" on a car that's using spherical bushings, which incidentally happens to be chewing up crowns and pinions, may be the smartest thing you can do, perhaps even before the problem starts?

                          Last edited by Wet Coast Racer; 05-08-2006, 09:05 PM.

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                          • #14
                            If the motor/axle bracket flexes at the rear, axle spacers won't provide much stiffening effect. The brackets would need additional bracing.

                            But do note the jumper wires bypassing the sliding contacts betwen the phosphor-bronze motor leads; are these factory stock, or added by a guy who understands electrical power loss at poor connections?

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                            • #15
                              If the motor/axle bracket flexes at the rear, axle spacers won't provide much stiffening effect. The brackets would need additional bracing.
                              You might think - but it's something you can feel in your hands, I noticed it with both chassis after this had been done, particularly my Slot.it.

                              But do note the jumper wires bypassing the sliding contacts betwen the phosphor-bronze motor leads; are these factory stock, or added by a guy who understands electrical power loss at poor connections?
                              Well observed, Robert. That's something that Dan added. To the eye, the SCX guide flag and the pressure strap contacts used between this, the motor, and the lights appears to be a source of quite tenuous contact. Yet in practice, it seems to work quite well, the lights on Austin's and the Manufacturer car still shining brightly and even power supply being provided to the motor. Old Yellowdog wasn't taking any chances, though!

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