Announcement

Collapse
No announcement yet.

Plastic Armature Gear

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • #16
    GCS -- Good question.

    And it is not like the pinion gears on inline motors are made of high-temperature engineering plastics.

    I do think that the inline motors are more efficient and don't get as hot as the traditional T-Jet motor. Do I have proof for that? No.

    Yet if a plastic armature pinion gear would work, then I'd think it would be in common use. If a plastic gear would be two cents cheaper than a brass gear -- and it worked -- then by gum folks would grab those two cents and run.

    My takeaway is it has been tried, probably by everybody who has made a T-Jet repop, and it failed. Due to heat? Yeah, seems likely.

    Ed Bianchi

    Comment


    • #17
      Typically Inline cars get hotter than T-Jets. Inline cars typically run plastic gears until you get to the really fast cars with a lot of downforce. You can safely run to 150 degrees F. Some people routinely run up to and over 200 F with no problems as well. Box stock inline cars typically run cooler that those set up for racing, but still warmer than your typical T-Jet.

      Comment


      • #18
        I guess there are two steps which can be taken to get some answers, neither of which I have the capability of doing at the moment. One would be to take the temperature of the pancake armature gear and the inline pinion gear after getting up to speed. The other would be to 3D print an armature gear, although I understand a 3D printed gear may not have good enough resolution to actually work without binding.

        Comment


        • #19
          Joe, if you're just running cars for FUN, there are still Aurora 14T armature pinion gears out there for sale at a decent price.
          And, as mentioned earlier the CNC modern gears are there for the task, too. I like to use the original brass gears that run just like back in the day...
          Good luck, my friend. Ernie

          Comment


          • #20
            Originally posted by Grandcheapskate View Post
            The other would be to 3D print an armature gear
            I'm guessing 3d printing would have issues with either the available material or the precision required.

            I would bet that is you asked RT-HO or maybe FLR to machine you a plastic gear they would be able to do it. They are both already set up to machine them, and RT-HO uses plastic stock for the crown gears. They should be able to substitute one material for the other. No idea what it might cost.

            Comment


            • #21
              It's sure nice to have you back, posing thought provoking ideas Joe

              Even though the components are arranged directly over the burner, so to speak, I dont think the primary issue is heat. The heat required to slush a plastic gear in a vertical arrangement would also produce mutually inclusive failures of the wind/insulation, and the gear plate; whether or not one uses a metal or plastic gear. Even with the fact that heat rises, and we do see a toasted pancake from time to time, such is really not the trend as a whole.

              I think the issue is friction, not thermal. Specifically, a lack of it in the press fit, when using a plastic gear on a metal shaft. It's all about dissimilar materials. Plastic cant withstand the required negative tolerance to get a reliable press fit, when using a gear of narrow cross section. Show of hands. Has the "inline" portion of the H0 community seen enough cracked pinions to stipulate to the syndrome?

              I went up to the slot cave. After a cursory glance at various armature to pinion arrangements using my eye-chrometer, I knocked the dust off the digital calipers, then trudged back down stairs to get a fresh battery. I only took one sampling of the chosen subjects, because the initial visual disparities are sufficiently graphic to indicate a trend.

              A T-jet arm shaft is 1.60 mm, the arm gear bore is 1.50 mm.

              A Tyco 440 arm shaft is 1.5 mm, the pinion gear bore is 4.50 mm.

              A Tomy Mega G arm shaft is 1.0 mm, the pinion bore is a whopping 7.00 mm.*

              From the above, using "handgrenade maff", we see that on the T-jet; a reliable metal to metal press fit affords the use of a gear cross section that is relatively similar to the shaft diameter ... lets not quibble over a 10th of a millipeter.

              Enter the Tyco 440. The dissimilar pinion gear material requires more than double the cross section. hmmmm ?

              As seen, on the MG+, should the diameter of the arm shaft be reduced, the bore depth must be increased further, in order to compensate for the loss of surface area.

              The metal to metal relationship is square. By spreading the load through a larger cross section, the negative tolerance that splits plastic gear can be sufficiently reduced to accommodate the load. This puts the relationship out of square, which in a vertical arrangement translates as increased height.

              Certainly steel and brass are dissimilar, but both being metal they are "genetically" similar. Plastic and metal are TOO dissimilar. So what we have is, similarly dissimilar, and radically dissimilar. Beyond both being made of matter, metal and plastic dont share enough properties to work in a short reach press fit, without the need for design compensations. Plastic simply doesnt have the density to survive either the initial, or stored energies, of a press fit; without first reducing the "intolerance" that creates a reliable fitment. That compensation rears it's head as extending the bore.

              Im further reminded that Aurora used the same press fit arrangement for power transmission at the pinion cluster. Conversely, AW kept the metal to metal press fit on the armature, but they chose to use the plastic to metal fitment for the pinion cluster. So how did they get away with using plastic gears with a narrow cross section at a power transmission? Notably and to my overall point, they "gnarled" the pinion shaft, increasing the necessary friction to produce a reliable press fit. Consider that the crown gears on both examples must use the axle splines for purchase on a plastic/metal fitment..

              Plastic gears are easy enough to make. At this point, Im at a loss to see a path without modifying the armature either by extending the shaft length, or knurling the shaft.

              Bill
              Last edited by model murdering; 10-31-2020, 03:57 PM.

              Comment


              • #22
                Originally posted by model murdering View Post
                It's sure nice to have you back, posing thought provoking ideas Joe

                I'm further reminded that Aurora used the same press fit arrangement for power transmission at the pinion cluster. Conversely, AW kept the metal to metal press fit on the armature, but they chose to use the plastic to metal fitment for the pinion cluster. So how did they get away with using plastic gears with a narrow cross section at a power transmission? Notably and to my overall point, they "gnarled" the pinion shaft, increasing the necessary friction to produce a reliable press fit. Consider that the crown gears on both examples must use the axle splines for purchase on a plastic/metal fitment..

                Plastic gears are easy enough to make. At this point, Im at a loss to see a path without modifying the armature either by extending the shaft length, or knurling the shaft.

                Bill
                Hi Bill,

                It's good to have a little time to come here and try to catch up on what's being discussed. It's amazing how much time out of my day is taken up. What little time I have for the hobby has been taken up with getting some parts designed and produced, trying to keep this hobby alive and affordable. Hence the inquiry about plastic gears.

                Well explained professor. Bottom line is your thesis proposes it is the length of the "grab" on the metal shaft that determines whether or not a plastic gear can work on a smooth metal shaft. The exposed shaft on a pancake armature is just not long enough to provide the needed grab.

                I do wish to point out one caveat in your statement about crown gears. There are guys out there, and perhaps many guys, running rear axles with no splines. These are either produced professionally in a machine shop or just home made axles cut from drill rod. It is important to note there is quite a bit of "grab" on a crown gear and probably very little heat as compared to an armature shaft. But it is worth noting that not all rear axles have splines.

                Joe
                Last edited by Grandcheapskate; 11-01-2020, 09:19 PM.

                Comment


                • #23
                  Joe,

                  My pappy was a dual engineering threat, and a humorist. He always called it "gription" with a wry smile. Used in a sentence: "Ya need more gription because it's too slickery."

                  Oh sure, smooth axle for a modern racing application. I started to type on the smooth axle and pulled it back, as my post was getting windier than usual. If memory serves, Loctite or CA is used, and some go so far as to glass bead a land on the axle, for the crown gear. I see it as the exception rather than the production norm.

                  The T-jet uses a whole heap of shoulder to extend the cross section of the plastic crown gear, regardless of the axle application. We see that the factory flipped the shoulder inboard from it's outboard position for the Tuff One and AFX 14 tooth pinions; and AW copied it for their JLTO and Extraction clones. To my eye, well prior to modern inlines, engineers were already compensating for a plastic to metal gear fitment by extending the bore in some fashion, to ensure reliability.

                  Related side note: Over years of restoration work, I've noted many a used short shoulder 12 tooth hop pinions that wont hold fast. Significant only by comparison, because of a notable higher failure rate, verses their limited numbers. Enough to make you go hmmmm, and always check carefully.

                  Same here Joe. Mom passed last fall. Life conspires to inflict chaos in my tiny, but well organized OCD world

                  B.




                  Comment


                  • #24
                    Originally posted by model murdering View Post
                    Joe,

                    The T-jet uses a whole heap of shoulder to extend the cross section of the plastic crown gear, regardless of the axle application. We see that the factory flipped the shoulder inboard from it's outboard position for the Tuff One and AFX 14 tooth pinions; and AW copied it for their JLTO and Extraction clones. To my eye, well prior to modern inlines, engineers were already compensating for a plastic to metal gear fitment by extending the bore in some fashion, to ensure reliability.

                    Related side note: Over years of restoration work, I've noted many a used short shoulder 12 tooth hop pinions that wont hold fast. Significant only by comparison, because of a notable higher failure rate, verses their limited numbers. Enough to make you go hmmmm, and always check carefully.

                    Same here Joe. Mom passed last fall. Life conspires to inflict chaos in my tiny, but well organized OCD world

                    B.
                    Bill,
                    Sorry to hear about your mom. My dad passed over 6 years ago and I can still feel it. Mom is just plain old tough. Last year after she was admitted to the hospital and unresponsive, the doctor thought she could not possibly survive because her vitals were not something anyone could live with. Within 48 hours all her numbers were back to normal. Doctor said she just decided this was not her time. I told the doctor my mother cannot make a decision about dinner and you want her to decide between life and death?

                    On your post, you mention the 12 tooth hop-up pinion. I think you meant to say when using the 12 tooth pinion and the crown which came with them, the crown had a short shoulder and not the pinion itself. Correct?

                    Joe

                    Comment


                    • #25
                      Regarding plastic gears, I just noticed that Dash has added delrin idler gears with both a large and small hole for T-jet and AFX.

                      Comment


                      • #26
                        Joe: "On your post, you mention the 12 tooth hop-up pinion. I think you meant to say when using the 12 tooth pinion and the crown which came with them, the crown had a short shoulder and not the pinion itself. Correct?"

                        Correctamundo!

                        Thankfully you have always been able to translate my demented gibberish. Two thoughts in my head, using two hands, on only one keyboard. That darn proof reader of mine is totally worthless! I'd fire him in a minute, but sadly he has tenure.

                        Bill

                        Last edited by model murdering; 11-03-2020, 02:37 PM.

                        Comment


                        • #27
                          Originally posted by Axle View Post
                          Regarding plastic gears, I just noticed that Dash has added delrin idler gears with both a large and small hole for T-jet and AFX.
                          Will the plastic idler gear be an advantage with either brass gear set or AW/JL plastic gear sets????

                          Comment


                          • #28
                            Just a question on idler gears...is there any advantage/disadvantage to either the small or large hole idler gear in general? One advantage I see in using a small hole idler is it becomes identical to the driven gear resulting in one less part which needs to be manufactured. In fact, if you use a small hole idler and a 14 tooth pinion, the four gears of the T-Jet become only two different gears.

                            Joe

                            Comment


                            • #29
                              Originally posted by Dyno Dom View Post

                              Will the plastic idler gear be an advantage with either brass gear set or AW/JL plastic gear sets????
                              I have no idea. But I know that Aurora moved to plastic gears (except the motor pinion) soon after releasing the AFX.

                              Delrin is very low friction (or can be depending on the flavor), and I would guess a delrin gear would be quieter.

                              But I have no idea if it's faster. As far as I'm aware, a plastic idler would not be legal in any of the well known T-jet racing classes.

                              Comment


                              • #30
                                By using plastic top gears in a pancake car you would reduce the overall weight of the car as well as the rotating weight of the drivetrain. The center of gravity of the car would also be a little lower. I wonder if anyone has done a careful study of what effect those would make. If changing from brass gears to plastic ones was not legal one might not consider it worthwhile to do such a study. JL/AW cars have plastic gears and my club races those in SS trim. I have found that my best JL/AW cars are as fast as my best Aurora cars even though they do not have balanced armatures and use slip-on tires as opposed to the silicone on sponge tires that the Aurora cars have. Confusing the issue somewhat is fact that the JL/AW armatures are about 14 ohms while the Aurora armatures are 16 ohms. In order to properly study the effect of brass VS plastic gears I would have to build a special car. Even so the act of swapping parts might inadvertently change something and muddy up the results. The easiest thing to do would be to build a JL/AW car with silicone on sponge tires and determine the best lap time, then change to brass idler driven and drive pinion gears. The cluster gear shaft would need to be changed as well since the JL/AW shaft is splined. Hopefully the mesh would be good using brass gears. I know that a few people like to change to brass driven and drive pinion gears with JL/AW cars because those can have mesh problems with the stock gears.

                                Comment

                                sex vidio
                                antalya escort
                                lara escort escort istanbul escort sirinevler escort antalya
                                beylikduzu eskort bayan taksim eskort lara eskort bayan bakirkoy bayan eskort
                                gaziantep escort gaziantep escort
                                izmir escort kayseri escort gaziantep rus escort
                                replica watches
                                kadikoy escort kartal escort
                                eurocasino
                                brazzers
                                Blonde and brunette dirty 3some in semi obscure Профессор трахнул студенту толстым хером pelicula embarazada por accidente
                                Working...
                                X