Articles

Build a Car the Right Way

Posted:  Monday, August 14, 2006
Written By:  Gary Katzer
Copyright:© 2006 Horizon Hobby, Inc.

How To Build a Car the Right Way:
Building Towards Your Future Success

I don’t know how many times I’ve seen it. What is “it” you might ask? “It” is a car that has been assembled poorly, and that poor assembly process normally translates into poor on-track performance. Over nearly 15 years in the hobby, I have built a fair number of cars. Some cars I rushed through, skipped steps and the initial on-track performance suffered accordingly. With other kits, I have been extremely meticulous during assembly and have been pleasantly surprised at the on-track performance the moment I hit the track. So how exactly do you build a car the right way? Follow along with me as I build a new kit, a Team Losi JRX-S, and I will reveal many of the tricks and tips that I have picked up over the years.

The Right Tools for the Job

Most kits include a rudimentary set of tools, be it Allen wrenches, box wrenches, or a turnbuckle wrench. While the included tools may get you through your initial building process, they tend to be made of rather soft metals. This means that after repeated use, the ends of the Allen wrenches may round off and potentially strip your screw heads. A number of years ago, I picked up a set of Allen wrenches with hardened tips, but over time and years of use they had worn out. When I picked up the JRX-S, I also snagged a set of Team Losi Race Wrenches (LOSA99104). These wrenches have color coded caps to make identifying the size easy, and the tips are titanium nitride coated. Additionally, using pliers to tighten the locknuts on your car or truck is not only hack, but you can also damage or round off the hexes on the nut as well. Use an actual set of nut drivers, such as the ones from Dynamite (DYN2812). Other tools that you may find useful would be the RPM Precision Camber Gauge (RPM70992), Dynamite Precision Ride Height Gauge (DYN2527) and Precision Droop Gauge (DYN2528), Team Losi Shock Matching Tool (LOSA99170), some sand paper, and a quality soldering iron such as the Weller Analog Soldering Station (WELWES51).

Prep Work

Ok, I know how exciting it can be to get your new kit, and how tempting it can be to simply dive into building. It is to your benefit to take a deep breath and resist that temptation. Instead of opening up all the parts bags at once and start piecing things together, take some time and read through the manual. I will often use a highlighter as I go through a manual for a new car for the first time to highlight steps that could potentially pose a problem. For example, when I built my Team Losi XXX-S Graphite Plus kit, I discovered that the front and rear shock shafts and bodies are slightly different lengths. If I hadn’t looked ahead, I may have had to disassemble and reassemble my shocks from building them wrong. I know a few racers who have done just that and became frustrated because of it. Before you begin building, you may want to check out the website for the manufacturer of your particular kit to see if there are any building tips or assembly updates. Many manufacturers will even post recommended setups for particular conditions for you to use as well. This will help you stay one step ahead.

After you’ve made any notes or highlights in the manual, it’s time to set up your building area. I highly recommend using some kind of pit towel on your work space. It will prevent any small parts from rolling away, and it will keep you from making a mess all over your work area with things like spilt shock oil, diff lube, or other things such as that. Don’t go grabbing your mother’s good quality towels either. (You know the ones I mean; the ones you never actually use and only get put on display when guests come over!) Additionally, try to set up in an area with the best lighting possible. Finally, I use several inexpensive plastic bowls to empty the contents of a parts bag into. From here, it’s time to get building.

Prepare Your Chassis

For cars that use graphite chassis plates or shock towers, you don’t want to just start bolting things to the chassis. You’ll notice that, out of the box, a plate chassis has squared off edges from when its cut out of the main sheet at the factory. You’ll want to sand down the chassis to round off the edges. The same thing goes for the battery slots, shock towers, and any top decks that your car might have. If you don’t sand down the edges of your battery slots, your battery pack will sit higher in the chassis than it should, affecting the center of gravity and adversely affecting the handling of your car. Additionally, the edges of the chassis can potentially cut through the shrink wrap of the cells, causing a short and potential fire hazard.

After you’ve sanded everything down, you’ll want to seal the edges of the graphite plates to prevent the graphite from splintering or becoming delaminated. The easiest way to do this is with some sort of fast-curing CA (cyanoacrylate) glue. Team Losi’s Todd Hodge recommends that you first sand the edges of the chassis down with 400-grit sandpaper, spray the freshly sanded edges with some Zip Kicker (PAAT50) and wipe down the sides of the chassis with a rag. As soon as you’ve wiped the chassis off, place the tip of your CA bottle against the chassis and squeeze out a small amount, allowing it to run down the edges of the chassis. The application of the kicker will make the CA dry almost on contact, sealing the edges of the chassis. You can also apply some CA to a cotton swab and run that around the chassis edges. Both methods work, it just boils down to personal preference. I normally apply 3 to 5 coats of CA to seal the edges of my chassis, sanding it down between each coat. Once you have the main chassis plate sanded and sealed, it’s time to sand and seal the upper plates and the shock towers. Once everything is dry, it’s time to start building.

Differentials

More times than not, I see people that neglect the differentials and wonder why the performance of their car suffers. The differentials have a huge impact on the overall handling and performance of your car. If a differential didn’t have that big of an impact, there wouldn’t be front spools or one-ways, now would there? If you build your diff right the first time, you will have better overall performance and the diff should last longer between rebuilds.

When you build your diff, you need to remember less is more. If you apply a huge glob of diff lube or thrust bearing lube, you will simply fowl the action and attract dust, dirt, carpet fuzz, or other debris, all of which will force you to rebuild your differential more often. I like to actually coat the differential pulley or gear instead of the balls themselves. I place a small dab of diff lube in each hole, and push the ball into place with my finger. Absolutely do not use an Allen wrench or other metal object to push the diff ball into place. You can potentially flat-spot or otherwise damage your diff balls before you even get everything together.

Once you have the diff balls installed properly, it’s time to build the rest of the diff. Much like the main diff balls, only use a moderate amount of bearing lube on the thrust bearing assembly. When you install the thrust washers, pay close attention to the direction that they are supposed to go into the outdrive. If you don’t install the thrust washers properly, it may be nearly impossible to properly tighten your differential. I’ve also seen diff rings slide off the outdrive when racers go to install the outdrives onto the pulley or gear itself. Some racers use contact cement or CA to glue the rings to the outdrives, but this can raise the diff ring up and create high spots. My recommendation is to simply take your time and be careful when installing your outdrives. It may take a couple tries to get right, but don’t get frustrated. When everything is put together, tighten the diff adjustment screw, but not all the way. When you tighten the diff screw down, rotate the diff outdrives back and forth in your hands to test the resistance and tension on the diff. As you feel the tension increase, hold the pulley and one outdrive while trying to rotate the opposite outdrive. Keep tightening until you cannot move the outdrive, and you should be pretty well set. You’ll need to make the final adjustments in the car, however.

Shocking Results

Next to tires, the suspension will have the biggest impact on the handling of your car. Debuting on the JRX-S, Team Losi has released a new shock design that is top-filled with a bladder. These new shocks are absolutely trick and are so incredibly easy to build and bleed the right way but, again, there are some subtle tips and tricks that will make your shocks operate more smoothly, longer.

Before you even begin the assembly of your shocks, you need to prep the O-rings seals. If you simply insert your shock shafts through the O-rings without prepping them, you could potentially tear or damage them. A torn seal will allow shock fluid to leak out of the body and lead to inconsistent handling. You should coat the O-rings in either shock oil or Green Slime (ASC1105) before you install them in the cartridge or in the bottom of the shock. This extra step will prevent the shock shaft from tearing and damaging the O-ring. Another thing that may damage your O-rings would be a scratched or damaged shock shaft. Use a side or nippy cutters to hold the shock shaft just above the threads while you screw the shock bottom on. This will keep you from scratching or damaging the shaft.

  

Bleeding the shocks is one of the most crucial steps during assembly of any car. Whether you’re building the original Team Losi shock, the new ones found on the JRX-S (or any other manufacturer’s shocks), air and bubbles are the enemy. I’ll walk you through assembling top-filled shocks, like the new JRX-S shocks. I begin with the shock shaft pushed in about ¼ into the body. From here, I’ll fill the shock up to the top of the body. Once the shock is filled, I pull down on the shock shaft, which draws the shock fluid down and under the piston. Work the piston up and down several times to release any trapped bubbles from under the piston. Before I cap the shock off or install the bladder, I let the shock sit in a shock stand, such as the OFNA Shock Stand (OFN10912) to allow any remaining bubbles to rise to the surface. Once I have filled all four shocks, I go back to the one I started with, place the bladder back on, and move the shock shaft up to clear any overflow from the shock body. From here, install the shock cap and you’re pretty well good to go. To ensure that your shocks are all the same length and that the left and right shocks have the same amount of fluid, invest in one of Team Losi’s Shock Matching Tools (LOSA99170). It’s much less expensive than a digital caliper and not only checks the length of your shocks, but also indicates whether one shock has more oil in it than another. The shock matching tool can also tell you if your springs are equal tensions as well.

Electronics Layout

When you think of where you’re going to mount your electronics on your chassis, remember to think not only about wiring but also about weight bias. While the size and weight of today’s speed controllers and receivers is next to nothing, they still have mass to them. Their placement can affect the overall handling and performance of your chassis. When choosing a location, try to keep things as low as possible and as close to the centerline of the chassis as possible. Back in the day, we would mount the ESC to the rear shock tower on off-road cars and trucks but, through testing, it was discovered that mounting an ESC lower on the chassis gave the vehicle more positive handling traits. I have seen some racers mount receivers on top of the servos because the lower chassis is too crammed to fit their electronics. If at all possible, try to avoid this as not only will you raise the center of gravity, you could potentially be more susceptible to RF interference.

Routing your wiring is also extremely important. Keep any ESC, personal transponder, or servo leads as far away from moving parts as possible. Spur gears and wiring don’t play well together, so keeping them separated is for the best. In most electric cars and trucks, this won’t be a major issue, but sedans and gas cars that feature 4WD have more moving parts that could potentially snag a wire and damage the lead. Use wire ties to bundle up any extra length of wire. Keep your power leads from your speed controller and battery pack as short as possible, but not so short that they would be pulling on the connectors, battery pack, or the speed controller itself. Finally, use servo tape or wire clips mounted to the chassis itself to hold wires in place and keep them from working loose and getting damaged.

The Jig Is Up!

Before you hit the track, you need to make sure your car is squared up. I know some of you just read that and wondered how you make a car with round tires square, but I am actually talking about your camber and toe adjustments. You wouldn’t expect your personal car to drive right on the freeway if you had 6-degrees of negative camber in the left front and 2-degrees of negative camber in the right, and your RC racecar won’t work right like that either. Just about every manual I’ve seen has a photo or image of your different camber and steering links, but that’s not an exact replica. As a friend of mine says, if you can’t measure it, you can’t manage it, so you’re going to need some basic tools to check your angles. Before you even think about checking your settings, you need to make sure that your car or truck is set up as you would run it. That means race tires, battery, motor, pinion, transponder—basically everything you would hit the track with except for a body.

When you get ready to set up your car, you’ll want to place it on a very flat surface, such as a piece of glass or a setup board like the Integy Setup Board (INTC22348). Any sort of imperfections or unevenness in the surface where you take your measurements can throw off your readings rather dramatically. The first thing to do is set your ride height on both ends of the car. It is very important that you set ride height before adjusting camber or toe, as when you raise or lower your ride height, you also change the angle of your camber links and steering links. For on-road cars, use a Dynamite stepped ride height gauge (DYN2527) for accurate measurements. You should give your car 5mm’s of ride height for rubber tires, 4mm’s for foam, and depending on the track, 3 to 4mm’s for 1/12-scale cars. Once this is set, you need to check the camber angle. I’ve used both the RPM camber gauge (RPM70992) and the Integy Setup Station (INTC22305), and both work well. The RPM gauge is convenient if you are in a hurry and need to make a quick or last minute change, while the Integy Setup Station is a little more precise and eliminates rim flex or distortion from affecting your readings. The Integy Setup Station also gives you the ability to check front and rear toe and front steering throw. Once you’re finished setting your camber and toe, you’re almost ready to hit the track.

Where the Rubber Meets the Road

Before you hit the track, you’re going to want to use some sort of traction compound or tire dressing on your car to increase traction during the opening laps, before your tires have had a chance to build up any heat. How you apply the traction compounds makes a big difference in the performance of your car. As a general rule of thumb, for foam tires you’ll want to apply traction compound to the full face of the rear tires and only the inside half of the fronts. If your car has too much front traction, you can cut back on the amount of traction compound you apply to the fronts to ¼ of the inside edge. If you need more front grip, then apply more traction compound to the front tire. Rubber tires are a bit different, as you’ll generally apply traction compound to the full face of all four tires. In fact, at many big races you’ll see drivers apply traction compound onto their tires and then use tire warmers to further soften the rubber to enhance grip. With foam or rubber tires, the length of time that you have the traction compound on your tires will affect the grip of the tires. If you allow the sauce to soak in longer, your tires will generally be softer; shorter, and they won’t be as soft.

On extremely high bite surfaces, the higher cornering speeds will literally try to rip the sidewall of the tire from the rim. There are a few tips to help reduce this effect, and increase the useful life of your tires. Before you run your rubber tires for the first time, apply a thin bead of Team Losi Tire Glue (LOSA7880) around where the rubber meets the rim. This will prevent the bead from pulling off the rim and affecting the handling of your car. For foam tires, you’ll want to true them down quite a bit to reduce the sidewall size and reduce the rotational mass. If you only plan on running sedans, you can’t go wrong with the Truecut-Light Tire Truer (INTC22338) as it comes with the right arbor pre-installed for you for the standard 12mm sedan hex. As a rule, for indoor racing, true your tires down to between 58–60mm’s for sedans or roughly 42–48mm for 1/12-scale cars. Before I true my tires down, I like to apply a thin bead of Team Losi Tire Glue around the tire where the foam is bonded to the rim. This guarantees that the sidewall shouldn’t deflect when the foam is being cut or when the tire actually hits the track. This will also help prevent the tires from chunking in the event of a crash.

Anytime you build a new car, you have a completely clean slate. A new kit doesn’t have a history of handling issues, parts falling off, leaky shocks or other issues. Most, if not all of these problems can be avoided altogether by taking your time when initially building your kit. Building a new car or truck isn’t rocket science, but many people are surprised at the levels of intricacy involved with a “toy car.” Most, if not all, hobbyists are capable of building their own kit if they take their time, read the manuals, and have the proper tools. Just remember that building a kit is only one step in the long life of a car, buggy or truck.


Tips & Tricks