NEIL'S WHEELS TECH TIPS

INTRODUCTION
ABOUT THE AUTHOR
TOOLS OF THE TRADE
T-JET BASICS
HOW TO MOUNT SKINNY T-JET SILICONES
AFX NON-MAGNATRACTION BASICS
AFX MAGNATRACTION BASICS
ALL ABOUT T-JET AND AFX ARMATURES
HOW TO “HAND-SELECT” A T-JET OR AFX ARMATURE
HOW TO INSTALL A T-JET OR AFX ARMATURE
GA-GA ABOUT T-JET GEAR RATIOS?
T-JET AND AFX MAGNET PERSONALITIES
HOW TO MAKE T-JET POLYMER MAGNETS
THE T-JET AND AFX GEARS THAT BIND
WHEN ALL ELSE FAILS ON T-JET AND AFX CARS
DRIVE TO WIN
CHASSIS DIAGRAMS

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INTRODUCTION

The purpose of this web page is twofold: to help new racers unravel some of the mysteries surrounding maintaining and racing Aurora Thunderjet and AFX cars, and to provide information for the experienced racer. If you've ever tinkered with and raced T-Jet and AFX cars, you'll understand that they are simple and complex; beautiful and ugly; rewarding and frustrating. Hopefully, the information contained herein will lead to a greater appreciation of these remarkable vintage slot cars, still goin’ strong after all these years!


ABOUT THE AUTHOR

I've raced slot cars (all scales) since I was ten years old, and have many fond memories of racing with my father, both in commercial raceways and at home. To me, the best thing about HO scale was that you could have a track at home! Some of my most vivid memories are of tinkering and racing for hours and hours on end in my own room. After racing for many years both in clubs and commercial raceways, I opened Neil’s Wheels Model Car Speedway--a full-time, full-service, HO scale-only raceway--in Plano, Texas in September, 1997. Neil’s Wheels has a large and active T-Jet racing program, with many extremely experienced, creative, and talented T-Jet mechanics and racers. It’s from this background--my own personal experience racing T-Jets, and from competing with and observing these other fine racers--that the information on this page is derived--Neil Planick.


TOOLS OF THE TRADE

Every worthwhile human endeavor requires the proper tools. So do yourself a favor and get the right tools and supplies for the job at hand. Here's a list to get you started:

-Set of jewelers screwdrivers.
-High quality pair of sharp tweezers, non-magnetic if possible.
-Set of small hobby pliers.
-Rechargeable Dremel tool with wire brush, grinding stone, collet set, mandrel for shoe cleaning
disk, and drill bit set.
-Pickup shoe cleaning disk for Dremel tool.
-Good quality digital ohm-meter.
-Tech-Block or gauge (to check the width of your cars).
-Tire diameter gauge (to check the size of your tires).
-Wheel and gear press and puller.
-Needlepoint oiler.
-Super Glue gel.
-Loctite Black Max adhesive.
-Rags and pipecleaners.
-Roll of wide masking tape.
-And finally...a good Plano tackle box to put all your cars and tools in.


T-JET BASICS

The Thunderjet was a revolutionary design in its day. The fact that these “toys” are still enjoyed and operational today is testament to their outstanding design and construction quality.

-Clean dirty oil off of the chassis soon after racing; don't oil again until just before practicing.
-Gently clean the motor brush springs inside the armature compartment with a folded-over pipe cleaner or small wire brush on a Dremel.
-Clean the pickup shoe hooks where they hook into chassis with a wire brush on a Dremel.
-Clean the motor brushes with a wire brush on a Dremel or on an index card or piece of paper.
-Polish the commutator and armature shaft gently with a wire brush on a Dremel.
-Polish the brass idler gear to a bright shine with a fingernail buffer.
-Polish the drive pinion gear and cluster-gear shaft with wire brush on a Dremel.
-Check the drive pinion/crown gear mesh: remove the magnets and idler gear and spin the rear tires with the gear plate mounted in the chassis. The tires should spin freely and not bind. If there is binding, make sure everything is oiled and assembled correctly; check the crown gear for flawed or broken teeth; check the cluster-gear shaft for free movement; make sure a tire or wheel is not rubbing on the chassis. As a last resort, try another gear plate and/or crown gear.
-Adjust the motor brush springs so the car rolls fairly freely when the power is cut. If the rear tires lock up, or car stops abruptly, then the brushes may be too tight. If the car runs too slowly (or not at all) and rolls very far, then the brushes may be too loose. Adjust the springs with the motor removed; if too tight, press down gently on the top of the brush while it’s sitting in the barrel; if too loose, gently push the spring up into the barrel from the bottom. When done, both brushes should be at the same height when sitting in their barrels.
-Adjust pickup shoe springs so the car powers smoothly through turns and does not jump (wheelie) out of the slot when starting. If the car “wheelies”, remove the springs and squash them down slightly with a tweezers. If the car now dies or has a lot less power than before, the springs may now be too weak; remove and stretch slightly to get the proper tension.
-Tweak the pickup shoes so the contact patch sits flat and full on the rails. Run the car for a few laps and observe the wear-stripe; it should run evenly through the entire contact area, not just a spot at the front or rear. Bend slightly to compensate, run, then check and adjust again.
-Spread out the front and rear tires as far as the rules and/or tech block will allow. Use spacers on the front end. Use Super-Glue to secure press-on hubs, but make sure they do not wobble before the glue sets.
-Check that there are no bent axles; remove axle and roll it on a flat surface and observe closely to see if it is bent. If so, replace immediately.
-If the rules allow, use low-slung bodies with the least amount of front and rear overhang.
-Leave the body mounting screws slightly loose--this allows the body to “float” and helps improve the handling.

HOW TO MOUNT SKINNY T-JET SILICONES

If you have ever raced with those skinny silicone tires on the small, stock T-Jet hubs, you know that they tend to fall off, sometimes over and over again in the same heat. Here's an almost foolproof procedure to cure this problem:

Step 1) Soak the plastic hubs in Mr. Clean Ultra liquid overnight to strip off all of the chrome. This is the secret, you must remove the chrome plating! But don't sand it off; this may remove too much plastic and then the tires will go on lopsided or loose.
Step 2) Wash the Mr. Clean off, dry the hub, and lightly press the hub onto a scrap axle. This is so you can hold it while you glue the tire on.
Step 3) Put a thin coating of silicone adhesive all around the hub where the tire will touch. Slip the tire on, and turn it around a little on the hub to distribute the adhesive. Make sure the tire is on straight, and then let it dry undisturbed overnight.
Step 4) Take the car you want to install the hub/tire combo on and put a dot of Super Glue on the tip of the axle. Place the hub/tire combo on the axle tip. Rotate the axle and straighten the hub/tire before the Super Glue sets up.


AFX NON-MAGNATRACTION BASICS

While the Thunderjet was good, the AFX Non-Magnatraction was better. Faster arms, stronger magnets, better tires and wheels, and a lower center of gravity let them dominate the competition in their heyday.

-Clean dirty oil off of the chassis soon after racing; don't oil again until just before practicing.
-Gently clean the motor brush springs inside the armature compartment with a folded-over pipe cleaner or small wire brush on a Dremel.
-Clean the pickup shoe hooks where they hook into chassis with a wire brush on a Dremel.
-Clean the motor brushes with a wire brush on a Dremel or on an index card or piece of paper. Don't forget to clean the groove in the brushes.
-Polish the commutator and armature shaft gently with a wire brush on a Dremel.
-Polish the brass idler gear to a bright shine with a fingernail buffer.
-Check the drive pinion/crown gear mesh: remove the magnets and idler gear and spin the rear tires with the gear plate mounted in the chassis. The tires should spin freely and not bind. If there is binding, make sure everything is oiled and assembled correctly; check the crown gear for flawed or broken teeth; check the cluster-gear assembly for free movement; make sure a tire or wheel is not rubbing on the chassis. As a last resort, try another gear plate and/or crown gear.
-If the crown gear and drive pinion actually slip past one another (a fairly common occurrence on AFX cars) place a very thin spacer behind the crown gear, or try another gear plate and/or crown gear.
-Adjust the motor brush springs so the car rolls fairly freely when the power is cut. If the rear tires lock up, or car stops abruptly, then the brushes may be too tight. If the car runs too slowly (or not at all) and rolls very far, then the brushes may be too loose. Adjust the springs with the motor removed; if too tight, press down gently on the top of the brush while it’s sitting in the barrel; if too loose, gently push the spring up into the barrel from the bottom. When done, both brushes should be at the same height when sitting in their barrels.
-Adjust pickup shoe springs so the car powers smoothly through turns and does not jump (wheelie) out of the slot when starting. If the car “wheelies”, remove the springs and squash them down slightly with a tweezers. If the car now dies or has a lot less power than before, the springs may now be too weak; remove and stretch slightly to get the proper tension.
-Tweak the pickup shoes so the contact patch sits flat and full on the rails. Run the car for a few laps and observe the wear-stripe; it should run evenly through the entire contact area, not just a spot at the front or rear. Bend slightly to compensate, run, then check and adjust again.
-Check that there are no bent axles. To check, remove axle and roll it on a flat surface and observe closely to see if it is bent. If so, replace immediately.
-For best handling, spread out the front and rear wheels/tires as far as the rules and/or tech block will allow. Use spacers on the front end. Use Super-Glue to secure press-on hubs, but make sure they do not wobble before the glue sets.
-If the rules allow, use a steel guide pin as the stock plastic pins bend and break easily.


AFX MAGNATRACTION BASICS

Some say the first “magnet car” contributed to the decline of the HO slot car hobby, others praised its ground-breaking technology. Follow these tips while building or restoring your own Magnatraction car and decide for yourself!

-Clean dirty oil off the chassis soon after racing; don't oil again until just before practicing.
-Gently clean the motor-brush coil-spring tabs inside armature compartment with a folded over pipe cleaner or small wire brush on a Dremel.
-Magnatraction motor brush coil springs loose their tension due to the heat and pressure they're subjected to, or if they are old. If they are bad, your motor power will just go away. Change them if they are old, or if you detect a loss in performance.
-Clean the motor brushes with a wire brush on a Dremel or on an index card or piece of paper. Don't forget to clean around the nub on the bottom.
-Clean the pickup shoe hooks where they hook into chassis with a wire brush on a Dremel.
-Polish the commutator and armature shaft gently with a wire brush on a Dremel.
-Polish the brass idler gear to a bright shine with a fingernail buffer.
-Check the drive pinion/crown gear mesh: remove the magnets and idler gear and spin the rear tires with the gear plate mounted in the chassis. The tires should spin freely and not bind. If there is binding, make sure everything is oiled and assembled correctly; check the crown gear for flawed or broken teeth; check the cluster-gear assembly for free movement; make sure a tire or wheel is not rubbing on the chassis. As a last resort, try another gear plate and/or crown gear.
-If the crown gear and drive pinion actually slip past one another (a fairly common occurrence on AFX cars) place a very thin spacer behind the crown gear, or try another gear plate and/or crown gear.
-Adjust motor brushes so car rolls fairly freely when power is cut; if the rear tires lock up, or the car stops abruptly, then the brushes may be too tight. If car runs too slowly (or not at all), then brushes may be too loose. Adjust brushes with motor removed; if too tight, remove spring and brush and press down gently on top of chassis spring/brush tab; if too loose, gently push spring/brush tab up from bottom of chassis. When done, brushes should be at the same height when sitting in their barrels.
-Wheelies caused by excessive pickup shoe tension are not that much of a problem with Magnatraction cars because the magnets hold the car down; however, you can capitalize on this by increasing the spring tension which can increase your power. Just don't increase the tension so much that the springs overpower the magnets and cause de-slots.
-Tweak the pickup shoes so the contact patch sits flat and full on the rails. Run the car for a few laps and observe the wear-stripe; it should run evenly through the entire contact area, not just a spot at the front or rear. Bend slightly to compensate, run, then check and adjust again.
-Check that there are no bent axles. To check, remove axle and roll it on a flat surface and observe closely to see if it is bent. If so, replace immediately.
-For best handling, spread out the front and rear wheels/tires as far as the rules and/or tech block will allow. Use spacers on the front end. Use Super-Glue to secure press-on hubs, but make sure they do not wobble before the glue sets.
-If the rules allow, use a steel guide pin as the stock plastic pins bend and break easily.

ALL ABOUT T-JET AND AFX ARMATURES

Aurora pancake armatures were manufactured with many different combinations of wire color, tip (lamination) color, and ohm ratings. While these factors alone do not determine the performance of a particular arm in a particular car, they can be used to help separate the good from the bad, select the proper arm for your specific needs, or at the least get you headed in the right direction.

-”Quadra-Lam” arm (copper wire/black tips): A super-fast arm with four armature plates or “laminations” (hence the name “Quadra-Lam”) that came only in the AFX Super II car. Has special advanced and silver-plated commutator. They usually ohm in the 4.0-4.5 ohm range. Very rare and expensive (if you can even find one!)
-”Mean Green” arm (copper wire/green tip or green wire/green tip): An excellent high speed racing arm. They rev high, but seem to have lower torque than other arms. They work best in light-weight cars (no handling pans or lead sleds). They respond very well to strong Super II or polymer magnets. They usually ohm in the 6.0 to 6.5 ohm range.
-”Tuff Ones” arm (green wire/red tip or copper wire/red tip ): Probably one of the best all-around, multi-purpose arms. Consistently has both good torque and top speed. They tend to run hot and suffer heat-fade with the stock red/white Tuff Ones magnets, so use stronger magnets if the rules allow. Ohm in the 6.0 to 7.0 ohm range. (There are also copper wire/red tip Magnatraction arms that ohm in the 13.0 to 15.0 ohm range--don’t confuse the two!)
-”Wild Ones” arm (green wire/gray tip): Never seemed to have very much luck with these arms. Might be worth a try, though, if you want to experiment, since they ohm fairly low, usually between 6.0 and 7.0 ohms.
-”Drag” arm (copper wire/blue tip or green wire/blue tip): Delivers what its name suggests: lots of torque. They don't have tremendous top speed, but this can be helped by using Tuff Ones gearing, larger tires, and strong magnets (even polymers are OK). This arm can handle weighted cars or cars with handling pans. They usually ohm in the 7.0 to 7.5 ohm range.
-”Magnatraction” arm (copper wire/red tip): There arms came in some Magnatraction cars with both standard and Specialty chassis. They ohm in the 13.0 to 15.0 ohm range, and generally run just OK.
-”Stock” arms: Red wire/gray tip and copper wire/gray tip are the most common.   Usually you have to check and run a bunch of these to find a good one, but when you do, they can run very well. They usually ohm in the 16.5 to 18.5 ohm range.
-”Christmas Tree” arm (copper & red & green wire/gray tips): These were among the first T-Jet armatures made. Many racers dismiss them because they ohm so high (usually 18.0 ohms or higher). However, if you can find one with fairly equal ohms, they can be very smooth and reasonably fast. They work better with  weaker magnets (avoid polymers). They ohm in the 18.0 to 21.0 ohm range. There is also a green & red wire/gray tip variation that usually ohms lower.

 
HOW TO “HAND-SELECT” A T-JET OR AFX ARMATURE

Regardless of which type of armature you choose to run in a particular car, there are general characteristics you should look for in terms of construction quality and electrical properties.

Step 1) With the commutator facing you, spin the arm in the gearplate and visually inspect the commutator as it spins; some are horribly out of round which will throw the whole arm out of physical balance; avoid installing one of these in a racing car. Also make sure the commutator is not worn, scraped, or gouged.
Step 2) Examine the wire wraps on the stacks. There should be no loose wires or wires hanging out. Also look at the solder joints; they should be neat with no gobs of solder all over.
Step 3) Check the ohms of all three stacks of the arm; they should have no more than about 0.3 of an ohm difference from one to the other (a little difference is usually present due to manufacturing variances.) Remember: the most equal ohms from stack-to-stack is the ideal, not necessarily the lowest. Write the ohms down for each arm you check somewhere on the gearplate.
Step 4) First, install (see below) and test-drive the arms that have both the lowest and most-equal ohms. If you're not happy with these, then try the higher, but most equal-ohm arms. If neither batch works out, then go ahead and try the rejects; sometimes these work out.

HOW TO INSTALL A T-JET OR AFX ARMATURE

Every racer worth his salt should know how to change armatures from gearplate-to-gearplate. It’s really not that hard, and once you try it a few times it’ll be a piece of cake!

Step 1) “Hand-Select” an armature as described above.
Step 2) Obtain a brand new armature pinion gear. DO NOT re-use a used gear, as they almost always spin loose on the armature shaft sooner or later. Think about it: all of the motor's power is transmitted through this gear so you don't want to scrimp on parts here.
Step 3) Look closely at the hole in the pinion: one side will be flat, and the other side will be slightly chamfered; the chamfered side must go onto the arm shaft.
Step 4) Place the armature in the gearplate and lightly hand-press the new pinion onto the arm shaft, chamfered side onto the shaft.
Step 5) Loosely clamp both ends of the armature shaft with the new pinion in a small hobby vise or wide slip-joint pliers. Carefully align the gear on the shaft so it is perfectly straight and square, and then tighten the vise or squeeze the pliers to press the gear on. Be careful not to press the gear too far on; the arm shaft should be flush with the top of the pinion.
Step 6) Install the gearplate in a chassis, put in an idler gear, and make sure the new pinion is on straight and the arm and all other gears spin freely.
Step 7) Remove the gearplate and do the “Twist Check.” Hold the pinion between two fingers of one hand and the arm between two fingers of the other hand. Slowly begin to twist the arm against the pinion, gradually increasing the force. If you can break it loose fairly easily by hand, then chances are it wouldn't have survived under racing conditions (better to find this out now, rather than in the middle of the race!) If it holds until the pinion teeth begin to dig a little into your fingers, than it's probably OK.
NOTE: Don't use too much force when doing the “Twist Check”--this can cause the gear to break loose unnecessarily! Use just enough force to ensure that a good joint has been made--this is something you will just have to  get a “feeling” for.

GA-GA ABOUT T-JET GEAR RATIOS?  

Gear ratio and rear tire diameter have a tremendous influence on your car's acceleration and top speed. It is very important to have at least a general understanding of how these factors operate and interact. Think about it: you're trying build a real (albeit H.O. scale) racing car with just a "one-speed transmission" so to speak! It's critical that you choose the right gear ratio and tire diameter.

-To begin with, there were three different gear ratios made by Aurora (actually four if you count the Super 2, but to keep it simple, we won’t get into that right now):

1) “Stock” gearing: 9-tooth drive pinion and a 15-tooth crown gear.
2) “Hop-Up” gearing: 12-tooth drive pinion and 15-tooth crown gear.
3) “Tuff Ones/AFX” gearing: 14-tooth drive pinion and a 15-tooth crown gear.

-Rule of Thumb #1) With a given tire diameter, Stock gears will give you the most acceleration (but least top speed), and Tuff Ones gears will give you the most top speed (but the least acceleration). Hop-up gears will fall somewhere between these two.
-Rule of Thumb #2) With a given gear ratio to get more top speed (but less acceleration) use a larger diameter tire; to get more acceleration (but less top speed), use a smaller diameter tire.
-Another Way To Picture It: Think about shifting a bicycle or car. Stock gearing is like “first” gear (most power/least speed); Hop-Up gearing is like “second” gear (less power/more speed), and Tuff Ones is like “third” gear (least power/most speed).

T-JET AND AFX MAGNET PERSONALITIES

Magnets have a tremendous influence on your car's acceleration, top speed and, in addition, handling. Too strong a magnet may cause the car to stop abruptly; too weak and it may roll too far. So be prepared to experiment with your magnets. Here's a run-down on the common T-Jet and AFX magnets by color:  

-The blue/yellow Super II “fully oriented” magnets (or “Turbo” magnets), and the white/orange Xelerator magnets are the strongest magnets ever made by Aurora. They will have a little “dimple” or indentation stamped into them. These are excellent magnets that make almost any car run better.
-Next strongest are the blue/red AFX Non-Magnatraction magnets. These also work well with just about any armature.
-Next strongest are the red/white Tuff Ones magnets, which are a good upgrade over Stock.
-The weakest magnets are Stock magnets in colors black/black (with white stripe), white/green, and orange/green.
-The red/white Magnatraction magnets basically came in only one strength.

HOW TO MAKE T-JET POLYMER MAGNETS

Did you know that you can make your own polymer magnets for T-Jets and AFX cars? They can make your car ballistic down the straight and out of the hole, with fantastic brakes, and cooler running, to boot. Follow the procedure below:

Step 1) Obtain a pair of Magnatraction Polymer magnets. These are thicker than regular T-Jet magnets and will have to be cut down as described below.
Step 2) Put the magnets in a scrap T-Jet chassis, and carefully grind off the protruding magnet material until it is flush with the top of the chassis. Use a Dremel with a large, wide grinding wheel, and go as slow and easy as possible, do not overheat!
Step 3) Carefully (they are fragile!) remove the magnets from the chassis and clean every particle of magnet dust off of them. Strips of duct tape work great!
Step 4) Paint the top of each magnet where it was ground down. This is not for aesthetics; it helps prevent cracking, chipping, and oil absorption. After the paint dries, install and let 'er rip!

THE T-JET AND AFX GEARS THAT BIND

Friction is the arch-enemy of T-Jet and AFX cars since the motors are relatively weak; every effort should be made to eliminate friction in all areas of these cars.

-One of the worst places for geartrain binding in T-Jets is in the hole where the cluster gear shaft fits into the chassis above the rear axle. You can keep trying different gearplates until you manage to find one that doesn't bind AND has a good arm, or you can ream the hole out a little bit (if your rules allow!). You'll be amazed how much freer the entire geartrain can get! The best way is with a drill bit with the axle removed.
-On both T-Jet and AFX cars, polish all gear teeth with a soft wire brush on a Dremel (go easy on the plastic and nylon gears, though). This removes all of the dirt and sticky oil from the teeth and really improves smoothness and reduces friction in the geartrain.

WHEN ALL ELSE FAILS ON T-JET AND AFX CARS  

Sometimes, no matter what you do, you can't get a car to run well. Before chucking the car in the junk box (or worse), try some or all of these tips:

-Change the entire armature/gearplate assembly. Why? Tight or slipping gears; binding, physical or electrical imbalance; open windings; worn commutator. Or just a dud arm.
-Change the chassis. Why? Weak commutator brush springs, especially in T-Jet copper chassis. Brush springs can suffer metal fatigue and may not be able to exert sufficient force on the brushes, no matter how much you bend them.
-Change the idler gear. Why? Binding here can ruin an otherwise well set-up car. Remove the gearplate and spin the arm with the idler gear installed-it should all spin freely.
-Install a brand-new set of motor brushes. Why? Sometimes the brushes have small cracks in them that you can't see, or they get saturated with dirt, oil, or dirty oil.
-Change the magnets, either to another similar pair, or to a pair that are substantially stronger or weaker. Why? Sometimes one magnet is stronger than its mate which unbalances the arm, and some armatures just simply run better with magnets of a particular strength, be it weak or strong.
-Turn one or both magnets over. Why? Sometimes you can get more power because of variations in the shape of the magnetic field thrown out by the magnets.
-Check the crown gear on the axle to make sure it is not slipping on the axle or slipping past the drive pinion. Replace the crown gear or axle or gearplate as necessary. Why? The teeth and/or hole in plastic gears do wear out over time, or the axle may be too small in diameter or the splines are worn out (so any gear you put on there will slip), or, believe it or not, brass drive pinions on T-Jets do wear down over time.
-Make sure the rear tires are not slipping around the hubs. Install a fresh pair of tires every now and then even if they look OK, and clean the hubs off before doing so. Why? Slip-on tires stretch and the hubs get oil and dirt on them.
-Make sure the guide pin is not worn too thin or short, or is bent. Why? A too-thin guide pin can cause deslots in the turns; a too-short pin can cause wheelie deslots upon starting, and a bent pin can bind in the slot, slowing you down all over.
-Make sure no tires, wheels, or gears are binding on the body or chassis. Check the car in both the straights and turns and make sure the body isn't hitting something.
-Make sure the axles are centered in the chassis. Why? The knurled part of the axle is larger in diameter than the flat spot and can bind badly in the chassis axle hole.
-If the rules allow, try the domed, slotted AFX silver brushes. Why? The slots prevent brush rotation and provide a solid electrical contact with the brush springs, the silver conducts electricity better, and the domed/angled top generates less friction with the commutator (however, these brushes may cause more commutator wear than flat brushes.)

Now that you’ve got your car all set up and humming along, what can you do on the track to improve your chances of winning? Read on: