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How much is too much!

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  • How much is too much!

    Here is a question I need an answer for. I'm not sure this end of the spectrum has been discussed about pancake armatures? So I know if you are searching for a good torque AFX arm you want to try finding a mean green. Something that ohm's out at 5.5 -6.0 ohms. Well how far up that ohm scale is useless or bad? 7.0-7.5?

    Same question with the T-jet Aurora arms or the modern AW product. I always thought the 14 -16 range was useful. The other night I was going through some old stuff for my builds. I found an armature that ohm'ed at 22-23. Is this bad,coming apart and useless? Seemed really strange and is what made me think of asking here. Most bad arms I have tested show an open field and no ohm rating. Thanks in advance for knowledge and comments!

  • #2
    Mean Green arms vary greatly in performance, some of them are no better than a good 16 ohm T-Jet arm, others are are so powerful that you could scarcely drive them in an A/FX chassis. With pancake arms in general I do take ohm readings, but that is mostly to avoid wasting my time with an arm that has a major defect. I look for arms with a good balance and for commutators that are centered, flat and level. After that the ultimate test is to put it in a car and run it.


    • #3
      (Edit. Looks like we posted at the same time.)

      All about careful selection and what magnets you match them with. What's the goal?

      As for Mean Greens, they are all over the map in performance. You can measure the poles until your wank falls off, but the true test of a Meanie is putting it in a chassis and running it. The low resistance was designed for higher RPMs, not torque. They aren't known for big torque, but some are amazing runners; some, not so much.

      The red tipped AFX Magna-Traction (red or gold wire) armatures were 12-15 ohms generally and were done so for additional torque. If you need torque, look into one of those or a JL/AW armature.
      Careful. There was an earlier red with gold wire Thunderjet armature. The wire tends to have a chunky look to it.

      Some of my best runners (a few even mounted in AFX chassis) are early T Jet arms in the 20+ ohm range, which also seem to respond well to stronger JL/AW or Dash magnets.
      Is that what it was? They can be wonderful.
      I think the gray tip gold/wire ones are pretty consistently good.
      That was the only problem with the early 20-24 ohm armatures, weak magnet technology.
      Last edited by JimDouglasJr; 05-15-2018, 01:17 PM.


      • #4
        I discussed a few (3) Magna-Tractions I have with Thunderjet armatures.
        All three are amazingly zippy. Three for three, so maybe not a fluke.


        • #5
          Thanks guy's,you 2 are the people I would figure for answers on. I guess I screwed up by mentioning "mean Green". I was only referring to them as a point of reference not what I actually had readings on. My 22+ ohm arm is a X-mas tree,I know,oh dear! That's why I was wondering? I mean dead is dead,but what about high out of range ohms?

          My other instance is a 4 gear red tip-red wire showing 16.5. I figure these arms are in the Dud range! So no use using them for anything. Wish I could find someone to rewind arms. Yes,I know I could do them myself as suggested before. However when it comes to this I would rather pay to play!


          • #6
            Bi-color and tri-color early armatures read in the 21-24 ohm range. Not unusual. See my topic I linked to two posts above, second page.
            I just added one I have with a tri-color early armature in an AFX MT. Thing is a bandit.

            Red on red is the Red Devil armature. 15-17 ohms is in their range. They are usually perky and often run better in reverse as they may have been designed/timed that way for the 4 geared Specialty chassis.

            My suggestion is find an empty gear plate and put them in a chassis without mounting the pinion and spin them up. Listen to see if they're quiet (well balanced) and wind up fast (high pitch).
            You're depending on numbers too much. Both of the examples you listed are well within their original tolerances at those numbers and may be wonderful.

            To summarize what I wrote in previous posts and the linked topic, Thunderjet armatures seem to perform spectacularly with modern magnets.
            I'll look through the rest of my collection for feedback on Red Devils, bur they're generally excellent. I'll see if I'm running any with newer magnets.
            Last edited by JimDouglasJr; 05-15-2018, 03:29 PM.


            • #7
              Thanks a lot,Kyle. I understand what you were saying. I was worried about the ohm values because I did not understand them and wanted to give reference. Will try my 4gear Red devil and see what happens. Only trying to make something out of nothing I have. No serious business out of all this. Will also try the X-mas tree in a T-jet as well,guess I could have done this all along but wanted a reference before I wasted my time!


              • #8
                It's actually a Red Devil. It was factory installed in both the Specialty and the Magna-Traction, so no need to differentiate.
                Time for a nomenclature lesson. The long chassis manufactured by Aurora with four gears is called the Specialty Chassis.
                Auto World's version is slightly different and is in fact named the 4-Gear.
                Anyway, I pulled all of the Reds I could find from my available runners collection. I have some "keepers" in cubes put away that may have one, but this is a good sampling. After the photo was taken, I did find another white Buddy Baker (11) Charger with one.

                The orange Matador (5), white Corvette and Camaro (7 and 6), both white Chargers (11), the black Ford woodie, BRE Datsun (35), and the red wingless Porsche Can Am car are among the fastest Magna-Tractions I have. Keep in mind, I have like 150-160 of them active, so that's a pretty good showing. So, about 10% have the Red Devil, and a good portion of those, about half, are in the top 10% of the entire 150-160.
                All are zingers most amateur home racers would be keeping in their race box.

                I outfitted 4 of them with Johnny Lightning X-Traction magnets. Three improved speed significantly. One was about the same but handled better. I didn't tinker with any of them much.

                The lone dud is in the white Matador (2). It's from a "loose keepers" case. JL Magnets did nothing for it.
                That chassis is in that case as I like to have my keeper bodies with a correct running chassis underneath so that they're whole cars.
                Speaking of, the Red Devil may get overlooked as it was an early Magna-Traction armature. Those chassis sometimes suffered from mismatched magnets, with the front often being weaker. With well matched magnets, their potential is realized.

                Anyway, if the Reddie spins up nice, mate it to some good magnets, even originals if in a Magna-Traction, and you should be happy with it. Almost guaranteed killer with JL/AW X-Traction magnets.
                Can't guarantee how it'll run in a Thunderjet or pre-Magna-Traction car if using original magnets. Should be good with later JL/AW or Dash magnets in those chassis'.
                Last edited by JimDouglasJr; 05-15-2018, 05:15 PM.


                • #9
                  Looking for that smooth snarl

                  What did us cave dwelling "analoggers" do?

                  JDJ: "My suggestion is find an empty gear plate and put them in a chassis without mounting the pinion and spin them up. Listen to see if they're quiet (well balanced) and wind up fast (high pitch).
                  You're depending on numbers too much. Both of the examples you listed are well within their original tolerances at those numbers and may be wonderful."

                  Thats my method and philosophy as well Kyle. I couldnt operate without a slave chassis for the bench. In just a few seconds I can quickly determine what one needs to know about the test subject. As a dinosaur, I see the advent of, and subsequent dependence on digital meters to be a bit of an exclusionary rabbit-hole.

                  Somewhere (I believe it was "H0 World"), I saw a thought provoking compilation of the top three Fray finisher's; where in the resistance values pole to pole where not always equal. Naturally I made a mental note at the time, simply because it supported my contention that optimum and actual are two very different things.


                  • #10
                    Kyle,sorry to mess up your nomenclature world. I am getting lazy in my old age and 4G is just so much easier to type. I used to differentiate when I first started here but not any more. Guess I don't care to be a slot car purist nerd like some of the Professors here.
                    Actually I kind of refuse to call it,Specialty chassis as there isn't anything special about them to me! After all the time and money I have spent on them things,I actually loathe them now. Honestly yes,I said that.

                    Geez Bill,you really shot me down with the Vohm meter thing.(sob)wimper) For 20yrs I worked on cars everyday for a living. Never,ever had anything more than a needle meter scale. Now I am into slot cars and go out and buy a cheap H.F. Vohm meter for them. Only to find out you guys say I don't need one? Who'd have figured.....

                    BTW Bill,what is a "anallogger"?


                    • #11
                      Analogger = old-timer.

                      Your meter did it's job. What it didn't do was tell you how well balanced the armature is, or how true the commutator. That's WAY more important than an exact match of the poles.

                      In other words, sometimes the ear is more important than the gadget.
                      Last edited by JimDouglasJr; 05-16-2018, 06:08 PM.


                      • #12
                        Well you will be happy to know I did make myself a cheap balancer over winter. Basically 2 utility knife blades in parallel. Before that I came up with an answer for a com facing tool. Basically a fine sanding disc for Dremel tools. And NO I do not use it on my Dremel for facing!
                        All I need to do with these disc's is enlarge the center mandrel hole,which I easily did with a paper punch. So there you go,voila....


                        • #13

                          I had some time today and wandered through my pre-Magna-Traction AFX cars.
                          I'm surprised I forgot about the Escort (46). It used to have standard magnets and was a bandit with them. It's since been upgraded to Super II magnets, and also carries an AJ's rear offset guide pin, AJs Stabilizer (brass), AJs low silicone rears, and a set of Aurora's longer power steering shoes.
                          Anyway, it was a build from parts about 9 years ago. It was a bandit with the Red Devil and all stock parts, hence earning the hop-up upgrades.

                          The Javelin (yes, the scarce "black 5" version) either came with the Red Devil, or I dropped it in in place of something lackluster. Stock AFX magnets and again, a punchy bandit.

                          The Porsche 510 (Auto World) has a grey tip/green wire Thunderjet Armature. I got it this way, as well as with the tall hot rod rear wheels. Someone built it. Standard AFX magnets; punchy fun bandito.

                          Anyway, more evidence maybe Aurora shouldn't have gone so low on the resistance. The Tuff Ones and early AFX failed with them - no torque/hot running. The Mean Greens were an improvement, but also often lack torque. They'll spin up fast without a load, but each one is a gamble with the stock 15 tooth crown gear. Some are amazing.

                          Other than an obvious dud in my survey, higher Ohm Thunderjet and Red Devils perform consistently well with decent stock or better magnets.
                          Last edited by JimDouglasJr; 05-17-2018, 05:53 PM.


                          • #14
                            This is getting interesting,Kyle. I will be sure to post more here or your other thread. Xmas tree's are the flavor of the day here. Will let you know how that turned out in my next post and a fake one I may have? I am getting more cars running,but some are still running bad considering the mongrel load of parts put into them! Got to find the right adjustment of parts to suit,but I am trying to get my brush tension set better.


                            • #15
                              Matched magnets. So important.
                              Brush tension:
                              After spinning up the car with power so it's loosened up, spin the rear wheels with your finger. They should spin very easily, but stop almost immediately. That's the sweet spot.
                              To slightly loosen the brushes - with the car on a track section, remove the gearplate and push the brushes downward until the leaf springs resist some. Too much and you bend them.
                              Also, the "V" brushes are junk. J. U. N. K. Junk.
                              You'll get better running, faster cars with flat brushes. Invest.
                              I'm running about 50 or so pre-Magna-Traction AFX cars. Hands down the best thing you can do for them is change the brushes.
                              Last edited by JimDouglasJr; 05-17-2018, 07:24 PM.