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SCX Rally cars

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  • SCX Rally cars

    I now have 5 new SCX Rally cars. Can the motors be replaced by other brand motors or do I have to buy SCX Rally motors to replace the motors that came in them? Does the long motor shaft that goes to the front wheels go inside the motor can? 2 of the cars are fast, 2 are slow, and one falls in the middle regarding speed. So far, I am not impressed with the consistentcy of the motors to say the least. If I can change motors, that will hopefully give me a chance at some consistentcy for running them IROC.

    Also, one out of five has a very loud gear mesh sound. Should I just replace the gears with another brand gears, or can I do something to fix it, like running the gears in with a rubbing compound with very tiny grit in the compound?

    This is my first experience with SCX car products. 2 of the cars came in the Acropolis starter set. 2 of the cars came in Initiation starter set.
    Should I try buying more recent editions of the Rally cars? If so, what year editions? Help please.

  • #2
    Hi Jack, the SCX motors are a little sensitive to break in and usually run better after they are "run in" a little. My favorite method is to remove the motor and connect it to a 9v battery or 6-9v power source will holding under water for about 2 minutes. This seats the brushes against the commutator. Afterward, blow them dry and lube the bushings with a small amount of oil. They should run better.

    As for the noise, check to see is the bushings are loose in the chassis, usually the SCX cars need the motors and axle bushings glued in place. This should quiet thing down. I like to use superglue or GOOP. If you use superglue, only use a little in case you have to get it apart again.


    • #3
      SCX motors

      There are several things to consider when talking about SCX motors. First the SCX 4x4 motors come in several designs. The main types are RX8 (old 4x4 without copper feet connectors), RX-81 with copper feet and RX-91 with copper feet and hotter armature( and may have a slightly shorter shaft). Now within these designators there are several updates that didn't change the motor P/N. Some of these are: long/ short stack armatures with different # of wire turns, poor/better comms both with and without solder rings, weaker/stronger magnets, modified brush holder hardware and minor case changes. As you can see it is possible to have 2 RX81s, for example, with very different performance because of the "minor" changes. If your cars are fairly recent then in all likelihood they have many of the latest updates. The latest and greatest motors should, with proper breakin, run around 21-22,000rpms at 12vdc and have much more torque than most of the FC-130s in other car types. This added torque allows you to run gear ratios that are lower numerically than you would typically run on Scalex Rally and similar with no great loss in acceleration/braking. The result being that the SCX performance is now as good as or better than the same setup (inline) in Scalex cars.
      Some things to check on your motors to get the most out of a particular type are:

      1. proper breakin- low dc voltage runin for 3 hours minimum to seat bearings and brushes. There should be little/no sparking around the comm if the brushes are seated properly and the brush spring tension is correct.

      2. brush spring tension- This is a little hit and miss but if the motor speeds up when you apply slight pressure to the brush at the spring end then you probably need more tension. Also if there is allot of sparking after breakin and motor sounds erratic with a steady voltage application then the tension may be too light allowing the brush to float or skip over segment gaps. Sometimes you may also need to sand the comm with 1200-1800 grit sandpaper to smooth out slight comm imperfections.

      3. brush holder hood alignment- this is often overlooked but can make great differences in performance because it can effect the motor timing.

      4. armature end to end slop and stack placement with respect to the magnets. The armature stack should float in the center of the magnetic field then the armature spacers should be set to maintain that position.

      5. bearing slop- Because of mfgring tolerances sometimes there is excessive slop in a motor bearing. Other than trying to match the cans to the armatures the only other thing you can do is to replace the bearing.

      6. oxidation on the contact feet and brush springs- Usually occurs on the spring feet and robs the motor of voltage. sand the copper feet tips and chassis lands to get the best connection. I usually add a drop of solder to the connections once I get the motor setup in the chassis so that the connection is solid. Brush springs should be clean and free of oxidation where they contact the brush and at the spring post interface.

      7. loose / out of alignment endbell- Sometimes the can crimps are not tight and allow movement of the endbell. Make sure they are tight and there is not endbell movement. Also there is some slop in this connection so make sure the endbell is properly aligned/seated with the can before tightening the can crimps

      There are several other items but they would take some explanation and I'm feeling lazy today.

      Last edited by JimmyinGreece; 08-17-2006, 02:34 AM.


      • #4
        Hi Pete and Jimmy,

        Well, I appreciate the comments. I think I got caught by cars with different upgrades. I probably should have researched and then bought the latest and greatest. Instead I bought 2 sets, with cars which were probably put together at different times. Live and learn.
        I will check out the loose bushing. Dunno how committed I am timewise to spending time tweaking the cars at this point.

        Jimmy, I was not aware that any 1/32 car motor parts : brushes, coms, brush springs were accessible. I'm guilty of not even looking before I posted this.
        I raced HO cars for a long time. The motor parts are not inside a metal "can", therefore the motor brushes, com, brush springs and motor magnets are at your fingertips (easily accessible) for tweaking/tuning.

        Thanks guys. Time, time, time. It is not easy to come by right now.


        • #5
          Batmanjack, this may be sort of unrelated to your questions but here goes. I bought a new generation Skoda and was pretty dissapointed. The car was slow and wouldn't make it accross my lane change area. I took the rubber band off to the front wheels and removed the interior. Now it's pretty well the fastest car I've got. I run my track on 18 volts. The closest car in out right speed that I have is my 1/24th Tamiya Mini Cooper S conversion running a Falcon IV. It is pretty close between the two but the Skoda is a way easier to drive.




          • #6
            Is that non magnet, Goggles?


            • #7
              SCx motors

              SCX motors are fairly easy to tune and replace parts.

              Brushes and springs are available from Teamslot if you can find them where you're at but it isn't all that difficult to take 16d brushes and use 1200grit sandpaper to size them to fit exactly. Some types of 16D springs can be made to work if you need new springs.

              As for armatures, many of the 16d arms will fit with a little work though the shafts tend to be a little short. This can be over come by setting the gear mesh with spacers or by using a long pinion and shaft extension.
              I generally don't put anything much hotter than an S16D armature because of the heat and the fact that anything much faster will exceed the capabilities of the brush gear and bearings.

              For magnets, the stock magnets are pretty good but if you want more , Teanslot makes a special set of Neos that fit the RX can.

              If you need bearings or want to rewind an armature with a better comm you can find comms and ball bearings at some of the RC sites that have parts for FA/C-130 motors.



              • #8
                Goggles - Is the new generation Skoda you referred to made by SCX? The reason I ask is because you mentioned removing the band to the front tires.
                The 5 SCX Rally cars that I own, have a front drive shaft and are gear driven.
                I got the SCX Rally cars because I heard good things about the gear driven versus band driven front ends. I'm glad to hear after removing the band and interior it came to life. Something along that line may work for mine.

                Pete - I have never opened a 1/32 or 1/24 can motor up. Aren't special tools required?
                Last edited by batmanjack; 08-28-2006, 08:50 AM.


                • #9
                  Huh? I never suggested opening the motor, only running it in under water.


                  • #10

                    No special tools needed to open one up. Just pry open the side tabs with a jewelers screwdriver or similar but be careful that the tool doesn't bend the brush hoods when you're prying. Look at my old tuning article at :
                    There is a section near the end on motor disassembly (SCX is 13UO type)



                    • #11

                      Pete - Gotcha. I should have made my last response to Jimmy in Greece instead of to you. Sorry bout that! I only get online at lunch. I was hurring too much! I will run the motors in water and glueing the bushings first. What method should I use to get the water out? A blow dryer or high pressure air?
                      I could buy an aerosol can for cleaning computer keyboards if necessary.

                      Jimmy - Gotcha. I will print and read your article. Thankyou. When someone shares knowledge, although I was reluctant to get into the motor, in the long run, it will be nice to know how. So far all the 1/32 motors I have seen have "all" the parts inside the can. The only thing you see is a motor shaft coming out of them. I will be taking the body off one SCX Rally car this weekend and re reading "all" that you have written in this thread !!!!

                      Motors are relatively pretty cheap when compared to the price of the entire car. What part number SCX motor should I order if I eventually want to replace any of my current SCX Rally motors in a "lazy" mans way of trying to "build" 4 similar running IROC cars without buying more cars. Do any other brand motors work in the SCX Rally cars?

                      I will try your tuning tips before I buy any replacement motor or other parts.


                      • #12
                        I just run them while blowing though them.


                        • #13
                          Gotcha Pete.

                          Pete and Jimmy - I looked at my motor and chassis tonight. I think SCX has the right idea putting the com and electrical com brushes and com brush springs outside the motor can. Am I correct in assuming: To remove motor, I first remove the rear axle assembly ( and axle bearings ) from the chassis, then snap the pinion bearing out of the chassis, then slip the motor backwards away from the front driveshaft?

                          What if I remove the front axle assembly and rear axle assembly and then run the motor "in the chassis under water" to seat the com brushes? Then remove the chassis and motor from the water and run the chassis and motor out of the water while blowing air thru the motor from my mouth. (And blow off the com and com brush assembly with a blow dryer on low heat) Then put the car in the sunshine to let the sun dry out the area between the flat brass electricals that run along the top of the chassis and the plastic chasis? It looks to me that it could be difficult to get the com back in between the brushes. Do the brushes fall out when the motor can is removed?

                          Is the front driveshaft and com brushes and com spring assembly all one assembly that comes out with the motor? It looks like it is one assembly and could all be placed under water together.

                          I have 2 RX-41 motors and 3 RX-81 motors in my 5 SCX Rally cars.
                          Last edited by batmanjack; 09-01-2006, 08:42 PM.


                          • #14
                            The motor should just snap out, straight up, with out doing anything else. The end bell, with brushes, is part of the motor and can only be removed by bending the tabs on the can, as Jimmy describes. I also like to add a couple drops of super glue to keep the motor from moving in the mounts when re-installing it.


                            • #15
                              Pete and Batman, my track is routed mdf with copper tape, no magnets. I guess I goofed up on the "latest" edition bit. It must be one version older. Still a lot of fun though. So far I have bought Scalextric, Ninco and Carerra cars for my track. So far I like the Scalextric the best. they run pretty well right out of the box. The only thing I do to them is shim the gap between the spur gear and the chassis if there is too much side to side play in the axle. Going around left hand turns on my track, they make a real racket if this gap is too great.

                              As mentioned earlier, I am running 18 volts and these cars really respond well to the increase.

                              I run two cars per slot and have been having a hard time getting lap timing to work. With the help of some of the guys on Jimmy Attard's AC2 Car mailing list I finally have the lap timing working. A really fast car can cut a 9.8 second lap around my 72' track. Average lap times are around 10.5 seconds. Now that I have the timing I can see what results my tinkering makes.




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