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Poor Running Speed Shifters

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  • Poor Running Speed Shifters

    I have many Speed Shifter chassis using them on a regular track setup - no special controllers.

    I find they run okay in one direction but very rough, noisy and poorly in the other direction. I'm not sure which crown gear is being used in the good running direction but I would have hoped they would perform about the same in both directions.

    Is this just a design flaw in the Speed Shifter?


  • #2
    I have never seen one of these cars in person, they came out a couple of years before Aurora went out of business.

    It looks like you have to run the motor in one direction to engage the large crown gear and in the other direction to engage the small crown gear. The small crown gear would give you more top speed providing that the mesh was good. I could not make out from the picture how the gears were supposed to switch. You might want to run a car on the bench with the body off to see what goes on. If the pinion gear moved towards the rear the small crown gear would be engaged, but so would the large crown gear unless the teeth were shaped so that they wanted slip in one direction. If that is the way it works the large crown would eventually be damaged and the entire rear axle assembly would need to be replaced. Slot Car Central has the rear axle assemblies and also the Speed Shifter controllers. Type Speed Shifter in the Search the Store box to find the part.
    You should also take a close look at the pinion gear to be sure that it has not been damaged.
    Last edited by RichD; 03-26-2020, 07:57 AM.


    • #3
      I think the controllers just changed polarity when the gears were shifted.


      • #4
        Originally posted by ElCamino View Post
        I think the controllers just changed polarity when the gears were shifted.

        17 years I've been on this forum, and always I seem to be learning something new.

        If I have this right then, those shifter cars were actually designed as dragsters, and when the driver decided to shift, it was not only from one cog to the other, but with a (more or less) simultaneous reversal of polarity to the motor?

        The sheer stress on everything in the power train - including all the gears - would be enormous, as everything suddenly got spun the other way, in order to go even faster in the higher gear. .


        • #5
          Or, was the intention that the driver be able to shift up or down on a regular circuit, in order to keep the motor within its optimum rev range for the different areas of the track?

          That would be a challenge, for the driver, but then they didn't have any brakes back then, did they?


          • #6
            I think I know how those Speed Shifter chassis change gears.

            Long ago Aurora experimented with a slotless racing set -- I bought one. The cars were designed to coast when not in contact with the power rails. Aurora managed that by designing in an extremely clever overrunning clutch inside the crown gear. It involved a small steel pin that went through a hole in the rear axle and was free to slide in the radial direction. The crown gear covered both ends of that pin. There was a cam surface molded into the crown gear. In one direction that pin came up against a stop, so the crown gear pushed on the end of the pin and drove the rear axle.

            In the other direction there was a cam slope that would push the pin radially so it would clear the stop, and the rear axle could spin free of the crown gear. When overrunning that pin was constantly sliding around the cam and moving radially, but that contributed little drag, and the car would coast very well.

            I believe the Speed Shifter chassis incorporates two of those overrunning clutch setups, which drive or overrun in opposite directions. Both crown gears would be engaged with the pinion gear continuously, but only one would drive at any one time, and which one drove would depend on which way the armature was spinning.

            I was very impressed by the simplicity and cleverness of that overrunning clutch design. It is a small miracle of miniaturization. I have never seen anything like it before or since. Whoever came up with it deserves recognition. It is a shame that such a brilliant and appropriate design never found a good home in slotcar design.

            Ed Bianchi


            • #7
              If that were the case both crown gears would look like they were engaged all of the time. The picture only shows the larger crown gear engaged and I don't see any sign of clutches built into the gears. I did find more pictures in Bob Beer's book that show gears that could include clutches.

              Looking at the first first picture that I posted nothing made sense, in order for the small crown gear to engage the pinion would have to move back, but there was no obvious way to make that happen. I really can't imagine those dinky clutches holding up for long, even if you did not shift very often. I do believed that the cars were dragsters.


              • #8
                Actually one of the things that impressed me about those overrunning clutches was how robust they were despite how tiny they were. I do believe they would have held up.

                My slotless cars are long gone, dang it. Someone needs to dissect a Speed Shifter and settle this.

                Ed Bianchi


                • #9
                  The way the Speed Shifter works is rather ingenious. The backside of the crown gears are unique in that they will engage a "clutch" and lock when the arm is turning in one direction while spinning freely when the arm is turning in the opposite direction. Because the two crown gears sit on opposite sides of the pinion gear, one crown gear sees the pinion as spinning "up" while the other sees it as spinning "down". This is why only one of the two "locks" onto the rear axle at any one depends on which way the armature is turning.

                  One thing to check on a Speed Shifter is the pinion gear. The Speed Shifter uses a longer pinion gear than a G-Plus or Super MagnaTraction because it needs to mesh with the teeth on the smaller of the two crown gears. In looking at Rich's picture, it seeems those chassis have the standard length pinion gear which will not reach the teeth on the smaller gear.

                  When the larger gear is engaged, the chassis runs about the same as other Super Mags. My issue seems to be when the smaller gear is engaged. There appear to be two issues.

                  One is whether the pinion is fully engaging with the smaller crown gear - this could be either because the wrong length pinion is used or the correct pinion is used but does not fully reach the smaller gear due to being pressed too far onto the armature shaft.

                  The second issue is wear to the back of the crown gear. It seems some of the smaller crown gears on my chassis may slip on their "clutch" leading to noise and a jerking motion as the crown is constantly losing it's grip on the axle.

                  I was given advice to know which crown gear engages in each direction. Hold the rear wheels off the track and run the chassis. The crown gear which is moving in the same direction as the wheels is the crown gear which is engaged. It looks to me as if the chassis runs quiet when using the larger crown gear and noisy when using the small gear, possibly due to one of the reasons listed above.

                  Last edited by Grandcheapskate; 03-27-2020, 08:13 AM.


                  • #10

                    So, are the crown gear clutches designed the way I described, with a sliding pin and cam surfaces on the crown gears? I'd really like to know.

                    Ed Bianchi


                    • #11
                      Originally posted by HO RacePro View Post

                      So, are the crown gear clutches designed the way I described, with a sliding pin and cam surfaces on the crown gears? I'd really like to know.

                      Ed Bianchi
                      No, it's not designed like a Tyco TCR where there is an incredibly small pin through the axle which engages the back of the crown gear.

                      There appear to be four pieces on the rear axle of a Speed Shifter; two crown gears and two "clutches". Both crown gears are loose on the axle and can spin freely. The clutches (for lack of a better term) sit behind each crown gear and are press fit onto the axle. The backside of each crown gear is hollow except for a small nub on the inside of the outside wall.

                      This is key: The clutches are designed like the latch on a door - rounded on front and squared off on the back.

                      For example, on a regular door latch the rounded side is on the front and the squared off section is on the back. This is so when you close a door, the rounded part of the latch can smoothly ride on the latch plate and be pressed into the door until the entire latch reaches the latch plate hole at which time the latch releases and goes into the hole in the latch plate. This is why you can open a closed door with a credit card - the credit card will ride along the rounded side of the latch pushing the latch into the door.

                      So on a Speed Shifter, in order for a clutch to engage the back of the crown gear, the square side must rotate until it hits the little nub on the crown gear. Once that happens, as the pinion turns the crown gear, the crown gear turns the clutch and the clutch turns the axle.

                      The crown and clutches are set up in such a way that only one clutch engages depending on the way the armature is turning. The clutch which does not engage is rotating in a direction where the rounded side hits the little nub on the back of the crown gear and the nub simply rides along the clutch without causing the clutch to rotate - much like the rounded side of a door latch rides the latch plate.

                      Does that make sense?

                      Last edited by Grandcheapskate; 03-27-2020, 12:59 PM.


                      • #12
                        After writing up the last couple posts I decided to take my own advice and look at the pinion gear. While the pinion gear on this chassis is the correct longer pinion, it was pushed a little too far onto the armature shaft and therefore did not completely mesh with the smaller crown gear. Pulling the pinion out a little further so it almost touches the rear axle solved my issue. The chassis now runs equally well in either direction using either crown gear.



                        • #13

                          So I understand how the clutches work, except for one thing. Something has to move radially in order for the latch to override the nub. There has to be a spring or something that slides in order for the clutch to disengage. If it is not a pin, like I described, it has to be some other device that can be cammed out of the way. Whassat?

                          Ed Bianchi


                          • #14
                            I had a whole explanation written but timed out and it got wiped out. Dang that ****es me off.. I'll try again later.

                            Just real quick...the clutches are shaped just like the latch on a doorknob. Rounded on one side and flat on the other. The rounded side will simply ride over the nub on the back of the crown gear while the flat side will hit the nub and turn the crown gear.

                            Actually it's the crown gear which turns and hits the clutch (which turn the axle).

                            Need more?
                            Last edited by Grandcheapskate; 03-27-2020, 04:02 PM.


                            • #15
                              It looks like you were not the only one that had the pinion gear pushed on too far, the one in the first picture that I posted was too far on as well and the picture did not show the clutches like the second picture did.
                              I really consider the shifter idea to be a gimmick. 1:1 cars need a transmission in part because the motor has minimum torque at low speeds. A DC motor has its maximum torque available at low speeds. If you were running your cars on a track with sweeping turns and very long straights you might want to shift into a higher gear, but most of the time it probably would be better to just change gear ratios.
                              If you had a dragstrip it would be an interesting experiment to first run the car in one gear, than in the other gear and finally shifting part way through the run.
                              Since these cars have snap-in rear axles you could also try using a conventional axle assembly. It is hard to imagine that you would get better times if you had to reverse the direction that the motor was running part way down the drag strip. I would also expect that the slipping clutch would waste at least a little power.
                              In the world of 1:1 electric cars the new Porsche Taycan Turbo S has a two speed automatic transmission on its rear wheels. When the car is cruising it is driven by just the front wheels, punch it and the rear wheels and motor kick in. It was the view of the testers that the added cost and complication of that system gave no added benefit on the street. Perhaps Porsche engineers should have looked at a Speed Shifter.