ssTuningGuide

8/9/2019 ssTuningGuide

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When selecting a motor I look for one that has a flat comm plate. Doesn't do any good tohave the face of the metal plates not making contact with the motor brushes. Even smallwaves can cause the motor brushes to bounce in their holders - no electricity transfermeans no power.I chuck the motor up in my dremel (the chuck is available at Walmart for ~ $11 and it holdsthe 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 wheelkit 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 upon the copper face of the comm plate. Clean as a whistle afterwards.



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 forhow flat it is. While you are rotating it you can see if it is flat or has rolling hills. Believe meyou can't imagine how wobbly the comm plate can be. There are remedies to fix a commplate that isn't flat but it doesn't always work.



Since it's all about reducing friction in the drivetrain then this is a simple method. Take adremel wire wheel and attack the teeth of the gears. Remove the top plate from the chassisfirst then take the center (idler) gear off the top plate and hold the wheel 90 degrees to theidler gear and remove some of those super tiny burrs on the teeth with the wheel. Makesure to wear eye protection as those wire brush pieces will fly off. They will embed ineverything, soles of feet etc...If you can't or don't want to remove the other gears from the top plate then you can attackthem 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 beforedoing so. The idea is to grind the teeth not get the gears spinning at 50 million rpm. Keepthe gear rpms to a minimum if possible and work on the teeth. You will notice a differencein smoothness. This is the easy method. There is a messier method called lapping in thegears with paste or polishing compound. Works better though to lap them in but the wirewheel 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 whenit really isn't. I used to use the old "ear dyno" but it lies to you big time. So the simplestsolution is to make an inexpensive dyno. Radio Shack or eBay sells this voltmeter. I got amotor from a tape deck and glued it onto the voltmeter. Then I soldered the leads to themotor, 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 clipsto the pickup shoes of the chassis and then lower the rear wheel until it contacts and spinsthe 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 againstthe motor brushes on the underside and if the motor wants more spring pressure then it willrespond 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 topplate and motor brushes to be able to properly adjust the pressure of the motor brushsprings. Remember to match your power supply to what the power supply will be for thetrack that you are going to be running on since some motors run very well at 18 volts butterrible at 13.8 volts. One simple solution for an adjustable power source is an old traintransformer 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 tracktransformer.



Air Gap Adjustment

What is air-gapping? It's cutting/grinding down the outside dimension of the metal lams tomake them all the same distance from the motor shaft. Sort or making the outside of thecircle center around the motor shaft. Why do it? It allows the motor to be centered in thechassis 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 isshimmed 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 Huffybike as a kid and each time you'd push downward on a pedal the bike would surge forwardthen slow down until you pushed downward on the other pedal. The motor behaves like thisif 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 highrpm. Make sure you do this step before you balance your motor as you are removingmetal.



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

doesn't have much metal removed.



Balancing The Armature

How to balance a motor? I like razor blades, long ones too. I bought some at Home Depotand then got a couple bolts, washers & nuts and sandwiched the razor blades in betweenthe washers. Works well enough for me. I do the initial balancing on this device then movethe motor over to a jeweler's balancing tool. It's got very fine/sharp edges to rest the motorshaft on to do very detailed balancing.

Once the motor stops turning I use a Dremel diamond wheel to cut a slot into the metal lamand remove metal. Remember it is the side that ends up on the bottom that you want togrind away at. Remember it's a diamond wheel - it will buzz clean through the metal lam ina hurry so go slow and don't take off too much. You'll also cut into the wires and ruin yourmotor if you get careless. (BTDT).



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



Another method of balancing is to add lead weight. You can cut slivers of lead off fishingweights to add to the motor. Remember, if you use this technique that you will have to addthe lead weight to the TOP of the motor when it stops on the razor blades. You can see asquare of lead on the right side of the motor that I added on the top of the comm plate andto 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 isrounded at the top and a tiny bit more narrow, the other has sides that go straight up and isa bit wider. If you've used the wire wheel trick to grind at the teeth of the top plate gearsbut your car still sounds loud & raspy then you might have some sloppy gear lash. Hold themotor pinion and keep it from moving then use your other free hand to move the rear gearon 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 centergear when you go back and forth with the outside gears.



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



Solution??? A fellow named Rick Terry at RT-HO.com has built a tool that will expand youranemic round top post outward and therefore eliminate the slop in your drivetrain. Noticethat his tool drives a metal point into the plastic idler post and therefore expands it. Makesure your idler gear is ON the post when you are smashing the post otherwise you couldmash 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. Theydon't necessarily have to be even - I just adjust upward the one that responds to higherrpms 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 tonot push too much at first - start small and see what happens.



Here it is after adjustment.

Here are some that have been adjusted for LOTS of pressure. Of course you can adjustthem too much and totally dork them up ruining the chassis.



Ruined motor brush spring:

Something that can rob horsepower is the motor brushes spinning in the brush cups. The JLbrush 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 Xactoblade. Be careful when doing so as you can slice through the motor brush with too muchdownward 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 brushspring 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 rulesstated "motor brushes cannot be altered in any manner" then this is a good method fromkeeping the motor brush from spinning in the brush cup while the motor is running. (Bunnyhairs on the chassis are no charge).





Trued Parts

How round or out of round are your parts? Things spinning perfectly around an axle workbetter than items that are out of round. Both of these are stock crown gears - I'd prefer theone on the left.

Is the hole in your idler gear centered? I marked the idler gear then made measurementswith a micrometer.



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 movethe air through it determines how fast you go then it stands to reason that a t-jet is anelectric pump. You need to make sure that the electrical connections are optimum and thatthe electricity flows unrestricted through to the motor. How many electrical connections areon 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 motorbrush 5. motor brush to motor comm plateYour job is to make sure there is little or no arcing across those connections. How to do it? Idunno - I've been trying to figure out all those connections ever since I've been racing thesethings.

Notice the pickup shoe on the right is properly adjusted since the whole shoe is contactingthe track rail. Now notice the left rail needs some adjusting as the rear portion isn't incontact 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 diamondwheel I cut a slot into it.



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



Truing The Wheels

What about your hubs - if you are using stock hubs I can probably guarantee that they willbe out of round. Here is an AFX hub on an axle inserted into the Dremel. I hold it verysteady 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 onone 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 whatabout these tips.

I bevel the bottom edge of the top clip so that if the idler gear bounces up while the motoris 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 niceramp to ride up onto and not a sharp edge then it will most likely make a smooth transitionto the next copper plate. Otherwise I'd imagine that it would bounce the brush when it hitsthe 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 thatcomes off the motor brushes conducts so if enough of that dust got in between the commplates 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 comeswhere the gear is located. Notice there is a gap between between the 9 tooth gear and thebottom 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 ittoo far and bind up the gear against the top plate.

Lastly - remove the motor magnets and motor brushes. Re-assemble the t-jet without thosetwo components and then spin the rear tires to see how smooth your drivetrain is. It shouldspin 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.rt-ho.com/tools.html

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 hispost.

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 withthe cut off wheel. Here is what my test track looks like after completing.



A view from below. You can see the front of the shoe is up a little

From the side

-SKR



Attaching W eight

How are racers attaching extra weight to the chassis for the Super Stock race? Super Gluedoes not seem to be doing the trick.Any chance we could modify the Super Stock rules to allow the weight to be attached to theunderside 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 .018putting 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.



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 hadbetter 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 Depotand 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 gettingthe 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 isinterested. Kim and I are running silver motor brushes that can be found through Jags here

on this pagehttp://www.jaghobbies.com/ho_slot_cars/parts_aurora.htm 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 herehttp://www.lucky-bobs-slot-cars.com/bsrt-t-jet.html 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 getthe cars back.



If your running RRR wheels and tires. Try the same size orings I mentioned above on thefront. 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, whichshould help on the 1/8th mile.

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