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One of the most popular forms of low end slot car racing is the almost scale proportioned 4.5" wheelbase NASCAR or NASTRUCK. Where the Techman races, these slotcars are not only popular, but subject to a considerable body of lore as to their construction and tuning. They also tend to run in a fairly unrestricted rules environment, allowing quite a bit of racer modifications without losing the 'flavor' of the class. Readers of this article will from time to time be reminded to check local rules for variences, but should in all cases keep in mind that if a change from bone stock is reccommended, its probably illegal somewhere. Most of the mods on this vehicle, however, will pass tech at most of the venues I race at. While this car (or truck) will have a super 16d motor, almost all of the chassis tuning tips will apply even if the reader utilizes the stock 16d, or even a C can motor. This is exactly what I would build one of my raceway patrons if they come asking for the ultimate vehicle in the class, but my particular choice of parts does not constitute a rejection of other possibilities. Once this article is online, feel free to experiment with other combinations, and if you hit on a good one please post it on the BB for all of us to review. Progress should never be static. For the core of the car/truck, I use the Parma Flexi 2 4.5" chassis. While not my choice in a 4" chassis, the Parma does seem to have advantages over its direct competitor from JK in the 4.5" size. These advantages are related to ease of driving and durability. If you race on an extremely long and swoopy track, the lighter weight of the JK might give it the nod. When rules allow, I build these cars with 3/32 axles and 64 pitch gears, but if you MUST do otherwise, the rest of the construction should not be effected. Lets begin! Insert the square Parma oilites in the chassis with the hole in the lower, forward position. With an axle through the bushings, solder them in place using acid flux and plenty of heat. Clean thoroughly, first using a damp Q-tip or rag to remove flux residue, and then a fresh wirebrush to shine the parts and reduce solder lumps. The Parma chassis is pretty accurate, but now would be a good time to use dial calipers and make sure the axle is parrallel to the flat bottom of the chassis. Next, slip an axle washer up againt the gear side oilite, and a JK 38 tooth plastic spur up against the spacer with the hub side facing OUT. A small flat spot should be ground in the axle to help keep the gear from spinning. I do this with my dremel hand grinder, but for a few bucks more you can buy axles with flats. In this configuration, .765 diameter tires will work on the car, providing legal, but minimal clearance. You may use larger tires for more tire life, but the car won't handle as well. Tire selection will be covered later. Add axle washers until you are close to the 3.250" maximum width. This is wider than the chassis, so do so evenly with a similar amount of tire overhang on each side. Now move forward to the motor bracket. Most rules will allow some modification here to enhance gear mesh. I cut out the horizontal strip of metal which separates the screw holes from the motor bushing hole. The motor will be soldered in without use of screws (and without the stock endbell bracket). Tweak the top of the bracket to bend it in towards the centerline of the car about .060". This allows you to install the pinion gear centered on the spur, but keep the spur close to the axle bushing, for best mesh. Move furthur forward. The body mounts consist of JK stainless pin tubing with Sonic .050 retainers soldered with the flat side out, just .040 from the ends of the tube. Its easier to solder the retainers to the tube first, and then install the tube by gently bowing it to get the ends to pop into the stock body mounting holes. The tubes should, at this point, rattle a bit in the holes without falling out. Now for the front axle assembly! I use the bushings in the lower, rear orientation. Solder as before, but this time solder the axle in place too. You will need a longer axle for this. Generic 2.5" axles are available, or you can cut the shaft from a 3/32" extension type drill bit. Try to avoid using piano wire or the long JK axles, as both bend too easily. I turn my front tires down to .720 diameter. If you are not allowed to do this, you may have to use the upper oilite orientation. Running smaller fronts with a lower axle will be useful in getting the body low, and to lower the center of gravity on the car. Take the set screws out of the front wheels, and mount them to the front axle by soldering a flat washer over the end of the axle. Now the fronts are independant rotating. Complete the assembly by using clear nail polish or super glue to coat the front tires, eliminating traction from the foam. Alternatively, JK and Sonic have hard rubber fronts, but they are noisy on the track! The guide is going to require some spacers to get the ride height correct. Slip braid into the guide, grap your Koford or RPM bronze spacers, and go to the track. Select a place where the braid recess is at its lowest. Add spacers on the guide shaft until the front tires are barely OFF the surface. If you press down over the tongue at this point, the chassis should NOT pivot over the front wheels and lift the rear tires from the track, but it should come close to doing so. Do whatever it takes to get the stack of washers to sit flat on the top of the guide. Magnehone and Proslot both make tools to help seat the washers and square up the threads on the guideshaft. Run the nut onto the shaft and tighten as far as possible without hindering the guide from turning. Be prepared to fiddle with this for a while: its worth it! Now lets get to the motor! I use the Trinity Midnight motor and the Proslot 38 degree super 16d arm. Give the chinese arm, spacers, brushes, and springs to a less fortunate racer, and if you are really particular, have the arm preconditioned. Its a lot better than the import, but I have yet to see an arm from any manufacturer that couldn't be improved at least slightly by one of the better balance and true specialists. The Trinity brush hoods are just a bit too tight for the Bigfoot II brushes you should use. I solder the hood to its underplate, glue the assembly to the endbell plastic, and then use the Magnehone hood hone to enlarge the hoods to suit the brushes. Be careful if you use one of the many aftermarket blueprinted motors. Many hurry around this step by just rebending the hoods, and get sloppy loose hoods as a result. The Techman prefers to aviod assassination and will not name brands here, but look carefully and you will see what I mean. This, incidentally, is the most important reason that I don't use the new Parma setup, as the hoods are already too big when you get them. Koford M313 springs (or the FastOnes equivalent) work well, but carefully tweak the short end to fit flat against the end of the brush. If on major hot power, try Champion light (the red ones) springs. Always, if you can get the tools, preradius the brushes so they will wear in before the comm wears out! The comm will be around .200 diameter when first run, so use the appropriate end of the Magnehone Turtle tool rotor. The only other motor modification I reccommend is soldering the can to its bushing. Of course, I expect you will use good, domestic brand spacers and the TQ or FastOnes screws. As many of the recent postings on the bulletin board indicate, I do not advocate shimming magnets on a super 16d, and in my races it wouldn't be legal anyway. On most tracks, this motor should run well with a 10 tooth pinion (I like Camen), but if for any reason you used a 25 degree arm, or less, try an 11 first. Solder the motor in across the top of your modified bracket, and again at the bottom in front, right to the chassis center section. Clean up the flux, as before. I shouldn't have to mention it, but use good leadwire such as Proslot, TQ midflex, or Koford in place of the stock wire. Slick 7 and TQ both make nice clips for leadwire. Route it under the front axle, but over the body mount tubes. Mess with it until you can use its tension to bring the guide to center after it gets twisted sideways during a deslot. Now, the body. Check on your rules for roof height minimum and bumper dimension, and mount the body as low as possible within the rules. I even mount the rear of the body low. 'Rake' on a 4 1/2 car will just make a naturally slimy car even worse, and any useless height in the body could also introduce tilt. A car that slides AND tilts is a real menace to itself and others! Next, check the rules and cut out as much of the rear bumper or tailgate as you can. This will allow more air to be sucked out from beneath the shell, increasing desireable downforce. This can be worth a full .15 second per lap on a truck, so go to the limit of the law on this item. Use Slick 7 stars or plastic with double face tape to reinforce the pinholes. Use the plastic under the hood and reardeck to reduce body flex due to wheelwell cutouts. The body should move a bit on the shaker tube body mounts. If it doesn't, you probably have one or more pinholes placed off center relative to the body mount holes in the chassis. Check the rules once more (or, in this case, ask the tech inspector) and if you can, bow the center of the chassis to lower it. Where I race, a full 1/16" is required under the axle and gear, but is not otherwise teched. When you bend the center down to about .030 clearance, another .20 seconds come off the laps, as well as a lot more driveability! Now, to the track! Drive the car alone on the track and push it to deslot in each corner. Note how it comes off, whether by sliding, rolling, nosing out, or bouncing. Refer to Paul Pfeiffer's tire selection guide elsewhere in Slotside for tire selection. In most cases, the proper rear tire will eliminate any need for lead weight. The exceptions would be an extremely tacky track, where weight at the corners of the chassis will encourage slide, or on an oval track, where it is usually desireable to bias the car in a single direction. You should now be ready to race. Remember, that to finish first, first you must finish. Avoid walls and assorted obstacles (such as your ill handeling competitors) around the track. Set a pace commensurate with your newfound speed, but which you can maintain without deslotting. Trust me, if you go the whole eight heats without coming off, you will probably win! Actually, just come off less than the other racers and you will probably win, since you now have the vehicle to keep up with the best! GOOD LUCK, AND GOOD RACING! Techman Back to Techman index Back to tech index |