Here is a stock motor that has nasty fouling on the comm plate.

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Britton Hudson
6 years ago
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When selecting a motor I look for one that has a flat comm plate. Doesn't do any good to have the face of the metal plates not making contact with the motor brushes.

2 When selecting a motor I look for one that has a flat comm plate. Doesn't do any good to have the face of the metal plates not making contact with the motor brushes. Even small waves can cause the motor brushes to bounce in their holders - no electricity transfer means no power. I chuck the motor up in my dremel (the chuck is available at Walmart for ~ $11 and it holds the motor perfectly centered by holding the shaft. Here is a stock motor that has nasty fouling on the comm plate. I then use a flexible very fine grit polishing wheel (I bought a gunsmithing polishing wheel kit with a wide variety of grits) that I hold in my hand and touch it against the shaft & comm face while it is spinning and also to remove the old crusty layering that has built up on the copper face of the comm plate. Clean as a whistle afterwards.

While you are rotating it you can see if it is flat or has rolling hills.

3 After the polishing is complete I can rotate the Dremel shaft by hand very slowly and I hold the motor at this angle so that I can look across the face of the comm plate and look for how flat it is. While you are rotating it you can see if it is flat or has rolling hills. Believe me you can't imagine how wobbly the comm plate can be. There are remedies to fix a comm plate that isn't flat but it doesn't always work.

4 Since it's all about reducing friction in the drivetrain then this is a simple method. Take a dremel wire wheel and attack the teeth of the gears. Remove the top plate from the chassis first then take the center (idler) gear off the top plate and hold the wheel 90 degrees to the idler gear and remove some of those super tiny burrs on the teeth with the wheel. Make sure to wear eye protection as those wire brush pieces will fly off. They will embed in everything, soles of feet etc... If you can't or don't want to remove the other gears from the top plate then you can attack them with the wire wheel while they are still attached to the top plate. Make sure to put a little bit of oil on the shafts since they can spin up and you want that shaft lubed before doing so. The idea is to grind the teeth not get the gears spinning at 50 million rpm. Keep the gear rpms to a minimum if possible and work on the teeth. You will notice a difference in smoothness. This is the easy method. There is a messier method called lapping in the gears with paste or polishing compound. Works better though to lap them in but the wire wheel method works pretty darn good too.

So you think you've got a fast car? Could be lots of vibration that makes it sound fast when it really isn't. I used to use the old "ear dyno" but it lies to you big time.

5 So you think you've got a fast car? Could be lots of vibration that makes it sound fast when it really isn't. I used to use the old "ear dyno" but it lies to you big time. So the simplest solution is to make an inexpensive dyno. Radio Shack or ebay sells this voltmeter. I got a motor from a tape deck and glued it onto the voltmeter. Then I soldered the leads to the motor, put a hub and tire on the motor shaft...voila! Instant, portable dyno. Just make a power supply and solder alligator clips onto the wire ends. Then attach the clips to the pickup shoes of the chassis and then lower the rear wheel until it contacts and spins the dyno wheel. It will read a number on the volts - the higher that number then the faster the motor is spinning. You can use this dyno to help you find the fastest combo for your car. Swap between top plates, try different motor brushes in each cup, gently press up against the motor brushes on the underside and if the motor wants more spring pressure then it will respond with more rpms... Be VERY careful when adjusting the motor brush springs upward - you can ruin them easily by putting too much bend in them. You must remove the top plate and motor brushes to be able to properly adjust the pressure of the motor brush springs. Remember to match your power supply to what the power supply will be for the track that you are going to be running on since some motors run very well at 18 volts but terrible at 13.8 volts. One simple solution for an adjustable power source is an old train transformer that has the handle on it to allow you to increase/decrease the amount of power. Use your newly acquired voltmeter to set the DC power output of the train track transformer.

Air Gap Adjustment What is air-gapping? It's cutting/grinding down the outside dimension of the metal lams to make them all the same distance from the motor shaft.

6 Air Gap Adjustment What is air-gapping? It's cutting/grinding down the outside dimension of the metal lams to make them all the same distance from the motor shaft. Sort or making the outside of the circle center around the motor shaft. Why do it? It allows the motor to be centered in the chassis and you can also shim the magnets closer to the motor for more power/torque. Sometimes a motor that isn't air-gapped will strike a motor magnet if the magnet is shimmed too close to the motor. You also get an equal attraction force from the metal lams towards the magnets. That smooths out the motor - sort of like when you rode your Huffy bike as a kid and each time you'd push downward on a pedal the bike would surge forward then slow down until you pushed downward on the other pedal. The motor behaves like this if the lams are differing distances from the motor shaft. I use a fine stone and hold it against the edge of the motor while it is spinning at a high rpm. Make sure you do this step before you balance your motor as you are removing metal.

7 The outside edge of the lam will look like so when finished. I try to hit 60-70% of the exposed edges - not all of it but nearly all of it. I don't want to remove too much metal. In this pic I pretty much hit 100% of this end - that means that one of the remaining two ends doesn't have much metal removed.

8 Balancing The Armature How to balance a motor? I like razor blades, long ones too. I bought some at Home Depot and then got a couple bolts, washers & nuts and sandwiched the razor blades in between the washers. Works well enough for me. I do the initial balancing on this device then move the motor over to a jeweler's balancing tool. It's got very fine/sharp edges to rest the motor shaft on to do very detailed balancing. Once the motor stops turning I use a Dremel diamond wheel to cut a slot into the metal lam and remove metal. Remember it is the side that ends up on the bottom that you want to grind away at. Remember it's a diamond wheel - it will buzz clean through the metal lam in a hurry so go slow and don't take off too much. You'll also cut into the wires and ruin your motor if you get careless. (BTDT).

9 Here are some slots that I cut into the lams to remove weight.

10 Another method of balancing is to add lead weight. You can cut slivers of lead off fishing weights to add to the motor. Remember, if you use this technique that you will have to add the lead weight to the TOP of the motor when it stops on the razor blades. You can see a square of lead on the right side of the motor that I added on the top of the comm plate and to the inside of the end of the lam. I use super glue to attach it to the comm plate. About Plates Not all top plates are created equal... Look at these two pics and you can see the difference in the idler gear posts. One is rounded at the top and a tiny bit more narrow, the other has sides that go straight up and is a bit wider. If you've used the wire wheel trick to grind at the teeth of the top plate gears but your car still sounds loud & raspy then you might have some sloppy gear lash. Hold the motor pinion and keep it from moving then use your other free hand to move the rear gear on the top plate back and forth and watch what happens to your middle (idler) gear. If you've got the round top center post I bet you've got some sloppy movement of the center gear when you go back and forth with the outside gears.

11 If you've got the top plate that has the straight sides going upward then you are in luck since you've got one that doesn't have lash problems.

12 Solution??? A fellow named Rick Terry at RT-HO.com has built a tool that will expand your anemic round top post outward and therefore eliminate the slop in your drivetrain. Notice that his tool drives a metal point into the plastic idler post and therefore expands it. Make sure your idler gear is ON the post when you are smashing the post otherwise you could mash it too much and bind your idler gear.

Brush Adjustments So how do you adjust the motor brush springs for more upward pressure. Here's a stock chassis with no adjustments. Notice one side is lower than the other.

13 Brush Adjustments So how do you adjust the motor brush springs for more upward pressure. Here's a stock chassis with no adjustments. Notice one side is lower than the other. They don't necessarily have to be even - I just adjust upward the one that responds to higher rpms when I push against it while the car is running on a power supply. Remember this next race has a track that is set at 13.8 volts. Test your car at that voltage if possible. Notice the tiny screwdriver pushing upward from the bottom of the chassis. Be careful to not push too much at first - start small and see what happens.

14 Here it is after adjustment. Here are some that have been adjusted for LOTS of pressure. Of course you can adjust them too much and totally dork them up ruining the chassis.

15 Ruined motor brush spring: Something that can rob horsepower is the motor brushes spinning in the brush cups. The JL brush on the left already has a notch in the bottom of it. What do you do with a stock

replacement brush? The Wizzard brush on the right has a notch carved into it with an Xacto blade. Be careful when doing so as you can slice through the motor brush with too much downward pressure.

16 replacement brush? The Wizzard brush on the right has a notch carved into it with an Xacto blade. Be careful when doing so as you can slice through the motor brush with too much downward pressure. Another method is to make a tool from a pair of needle nose pliers that has a U shaped end. You can then grab the motor brush spring and squeeze it to make the end of the brush spring a U shape. The points on the ends dig into the motor brush and keep it from rotating. This can be a dangerous exercise as I've ruined more brushes than helped. If the rules stated "motor brushes cannot be altered in any manner" then this is a good method from keeping the motor brush from spinning in the brush cup while the motor is running. (Bunny hairs on the chassis are no charge).

round. Both of these are stock crown gears - I'd prefer the one on the left.

18 Trued Parts How round or out of round are your parts? Things spinning perfectly around an axle work better than items that are out of round. Both of these are stock crown gears - I'd prefer the one on the left. Is the hole in your idler gear centered? I marked the idler gear then made measurements with a micrometer.

19 Here are pics of the 4 different sides being measured.

Efficient Electrical System Since an automobile engine is basically an air pump and how fast or efficiently you move the air through it determines how fast you go then it stands to reason that a

21 Efficient Electrical System Since an automobile engine is basically an air pump and how fast or efficiently you move the air through it determines how fast you go then it stands to reason that a t-jet is an electric pump. You need to make sure that the electrical connections are optimum and that the electricity flows unrestricted through to the motor. How many electrical connections are on a t-jet chassis? 1. Pickup shoe to track rail 2. Pickup shoe to hanger plate 3. Hanger plate to bottom hanger plate (notice the rivet that holds them together?) 4. Hanger plate brush spring to motor brush 5. motor brush to motor comm plate Your job is to make sure there is little or no arcing across those connections. How to do it? I dunno - I've been trying to figure out all those connections ever since I've been racing these things. Notice the pickup shoe on the right is properly adjusted since the whole shoe is contacting the track rail. Now notice the left rail needs some adjusting as the rear portion isn't in contact with the track rail. Speed is being lost because of this improper adjustment. I made a tool from a tiny screwdriver and using a steady hand and the Dremel diamond wheel I cut a slot into it.

You can also set the car on a piece of test track (small piece you cut of of some old

22 Notice where you grab the pickup shoe to adjust the angle - twist the shoe to bend it ever so slightly then run it again and see what the results are. This takes time so be patient. You can also set the car on a piece of test track (small piece you cut of of some old track) and look from the sides to see if the pickup shoe pad is resting flat on the track rail.

I hold it very steady and slowly take little bits of the wheel down by grinding it against the metal

23 Truing The Wheels What about your hubs - if you are using stock hubs I can probably guarantee that they will be out of round. Here is an AFX hub on an axle inserted into the Dremel. I hold it very steady and slowly take little bits of the wheel down by grinding it against the metal file. I stopped to show that the hub was in fact out of round as you can see the paint missing on one half as I'm truing up the hub.

Other Tips Ok last of the tips - I've got to save a couple of them for myself. I'm probably taking this a little far but if reduction of friction is the overall goal then what about these tips.

friction on the gear. What about the comm plates - I take an Xacto blade and draw it across the leading edge of the comm plate that first comes in contact with the motor brush.

24 Other Tips Ok last of the tips - I've got to save a couple of them for myself. I'm probably taking this a little far but if reduction of friction is the overall goal then what about these tips. I bevel the bottom edge of the top clip so that if the idler gear bounces up while the motor is running then the teeth don't run into a sharp edge but rather a beveled edge that doesn't cause as much friction on the gear. What about the comm plates - I take an Xacto blade and draw it across the leading edge of the comm plate that first comes in contact with the motor brush. If the brush has a nice ramp to ride up onto and not a sharp edge then it will most likely make a smooth transition to the next copper plate. Otherwise I'd imagine that it would bounce the brush when it hits the leading edge if it isn't beveled resulting in less time that the electrical connection is being made.

Make sure to clean the crud out from between the comm plates - after all the dust that comes off the motor brushes conducts so if enough of that dust got in between the comm plates theory would seem

Notice there is a gap between between the 9 tooth gear and the bottom side of the top plate.

25 Make sure to clean the crud out from between the comm plates - after all the dust that comes off the motor brushes conducts so if enough of that dust got in between the comm plates theory would seem that it could short between the copper comm plates. You might notice the fact that there is some mounting slop on the rear shaft when it comes where the gear is located. Notice there is a gap between between the 9 tooth gear and the bottom side of the top plate. I'd drive one of the two gears (top gear or the 9 tooth gear) towards the other one to remove some of that excessive gap. Be careful and don't drive it too far and bind up the gear against the top plate. Lastly - remove the motor magnets and motor brushes. Re-assemble the t-jet without those two components and then spin the rear tires to see how smooth your drivetrain is. It should spin freely - try this in both directions. If not then you've got some work to still do.

Where to get the tools to work on t-jets? ( I remember back in the day that a screwdriver, needle nose pliers and a tiny hammer were all that we had.) I use a lot of stuff from Rick Terry. http://www.

Here is a way to get a closer look at how your pick up shoes ride. Tweak them to run as flat as possible. Jet demonstrates a great tool he made above in his post. Old piece of Aurora track.

26 Where to get the tools to work on t-jets? ( I remember back in the day that a screwdriver, needle nose pliers and a tiny hammer were all that we had.) I use a lot of stuff from Rick Terry. There are many other tool makers as well - the race sponsors carry lots of their stuff too. Other Tips from PSYCHOSLOT members As Jet talks about above. Here is a way to get a closer look at how your pick up shoes ride. Tweak them to run as flat as possible. Jet demonstrates a great tool he made above in his post. Old piece of Aurora track. Let's chop this mother up! Take a Dremel with a cut off tool and cut along the rail. Use a round grinding stone on your dremel to smooth things up after your rough cut with the cut off wheel. Here is what my test track looks like after completing.

27 A view from below. You can see the front of the shoe is up a little From the side -SKR

Attaching Weight How are racers attaching extra weight to the chassis for the Super Stock race?

Any chance we could modify the Super Stock rules to allow the weight to be attached to the

-waltgpierce I've found this to work better at least here on our track.

D.) by 1/16" width O-Rings. I found theses at Lowes for 59 cents.

28 Attaching Weight How are racers attaching extra weight to the chassis for the Super Stock race? Super Glue does not seem to be doing the trick. Any chance we could modify the Super Stock rules to allow the weight to be attached to the underside of the body as long as it is not visible? -waltgpierce I've found this to work better at least here on our track. This will drop the frond end.018 putting more pressure on the pick up shoes. 5.32" I.D. (9/32" O.D.) by 1/16" width O-Rings. I found theses at Lowes for 59 cents. More Tips RRR stock front tires..384" To help mount the orings I rolled the orings from the ball tip side up onto the pen body. After the orings are both in place I butted the pen body up to the wheels tight and rolled each one over to the front wheels.

-SKR Sam I use O Rings on front wheels all the time, here's a tip, go to Lowes or Home Depot and in the plumbing dept look for #5, O Rings on a plastic case I think I paid a buck something for 10

29 Picture from the bottom side of the chassis. Side view, new orings mounted are.366" and they touch and roll on the track. I've also had better e/t's by taking the front tires you just took off and placed them on the rear. -SKR Sam I use O Rings on front wheels all the time, here's a tip, go to Lowes or Home Depot and in the plumbing dept look for #5, O Rings on a plastic case I think I paid a buck something for 10 pcs, cheaper than getting the individual ones at the Hardware store. They also fit the AFX size front ends to. -kdogs Here are the things that we've done to our cars along with Jet's tune up tips if anyone is interested. Kim and I are running silver motor brushes that can be found through Jags here on this page Don't forget to add brush tension as Jet describes in the tuning guide. BSRT pick up shoes #504 which can be found through Lucky Bob's here I found these pick up shoes to work best on our cars. And we added lead weight to the front of the cars. I'll take pictures of the weight when I get the cars back.

30 If your running RRR wheels and tires. Try the same size orings I mentioned above on the front. Also as mentioned we took the front RRR tires off the front and put them on the rear. The cars seemed to run better this way and will get your car up to speed quicker, which should help on the 1/8th mile.

The Magazine For Slot Car Enthusiasts

The Magazine For Slot Car Enthusiasts Building the Tomy Super G+ By Milt Surratt Tomy Super G+ slot cars have been around in the current form for about 12 years. Out of the package, the Tomy HO slot car