Project: Ultimate Rustler
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With Phase I of the Ultimate Rustler project, I earned the respect of many an Associated and Losi driver at the track. I also earned such novel titles as "maniac" and "Dremel savage." It had been my first hobby-level R/C, and it had hardly seen the charge of a 1500mah pack run through it before the modifications began.
The Ultimate Rustler took the "Swiss cheese" concept to a whole new level while turning Traxxas into a force to be reckoned with in the local racing scene. However, it has been two years since those fun, early days of reckless experimentation. I've since built and run a Stampede, the Spyder and Valkyrie E-Maxxes, a 4-Tec, and many, many other R/C's. I've done modifications to and raced a 1:1 scale car. I've studied aerodynamics and the physics of racing suspensions and I've extensively practiced rally racing through a computer simulation.
After going through all of this, I finally went back to try out my old trusty Rustler, remembering the joy of powering it around the track at great speeds, passing high-end graphite racing trucks and drawing curiosity from fellow drivers. This time, though, much to my suprise, I was completely unhappy with what I saw. Without even putting it on the track, I noticed a laundry list of things that could be improved. Once I began to drive it, I was downright disgusted!
The time had come to put some of the past two years' experience to work, to shelve my old ideas and assumptions and make the Ultimate Rustler into a refined machine that I could once again be proud of.
** Be sure to click on the images below to see the large, zoomed-in versions **
|Stretching Performance: The Suspension|
Note that in Phase III, some of the following changes were changed again, for the better. At the end of the Phase III project, these changes will be merged together.
Weight savings are a great thing, but to continue to live up to the name of "Ultimate Rustler" and have a fair shot at toppling the supremacy of the XXX-T's at the local track, I decided to do some major, but ridiculously inexpensive changes to improve the truck's handling.
Laying the shocks down a bit (angling them inward) would contribute to increased progressiveness of the suspension action. This means that when the suspension is level, the wheels can move up & down with relative ease to "soak up" small bumps, but as the shocks are compressed, they become stiffer at an increasing rate, diminishing the tendency to bottom out over jumps.
When I tried to move the upper mounting point of the rear shocks inward, the shock bodies would rub against the chassis tub when the suspension was not compressed. Moving the mounting points down and back outward a bit would get around this, but then I ended up with far too much downtravel. I ended up switching to front shocks in the rear to solve this problem. Click the top picture on the left to see the detail. On each side, I drilled a hole through the shock tower and mounted the shock with a 3x12mm bolt and locknut, one thin plastic washer/spacer (from the parts tree that the spring preload spacers come on) and one long step-sided spacer (from the same tree -- don't know what it's called, looks like two cylinders butted end to end, one smaller in diameter than the other -- the top of the shock fits over the smaller end perfectly). This left me with a huge portion of unused shock tower, so what did I do? Cut it off to save weight, of course!
Up front I was conveniently able to reuse my rear shocks! I stole the Nitro Rustler stock front shock tower from the Ultimate Stampede to take advantage of its closed top and used the same mounting trick, though using two of the thin washer/spacers on each side this time. I then cut off the stock shock mounting posts to save a few hundredths of an ounce or so.
The end result of this suspension conversion is a significantly more agile truck that lands the jumps with much greater ease. I have much, much more suspension travel now (over 2" vertical travel at each front wheel), which also helps to smooth out the jumps by giving the shocks more of a chance to do their job on the landings.
At the front corners, I switched to Nitro Rustler caster blocks and Kyosho Ultima EP ST Type R steering knuckles with aluminum spindles. This allows me to accept standard Associated wheels with 3/16"x3/8" bearings in the wheels instead of the 5x11mm knuckle-mounted bearings and spinning stub axles I had before (the standard RPM bearing carrier upgrade). The wheels are attached with standard 4mm locknuts.
I had considered doing the full Nitro Rustler conversion with the N.Rustler's knuckles, spindles and wheels, but that would have weighed quite a bit more (solid steel 5mm spindles, bigger bearings, and slightly heavier wheels). I had to drill out the spindles & knuckles to accept the N.Rustler kingpins. Also, the N.Rustler c-hubs accept larger suspension arm pins than the E.Rustler uses. I didn't want to bore out the holes in the suspension arms to accept the larger pins as this would dramatically decrease their durability. Instead, I inserted into each knuckle a length of thin-walled 1/8" aluminum tubing (available at a general hobby shop, around where they keep either balsa or tools) that I sanded on the outside and bored on the inside with a small drill bit in a pin vice. The Kyosho knuckles are also not tall enough to fill the space in the c-hub, so I used another two plastic spacers from the shock accessories part tree (one above, one below) plus a clear Nylon washer from a stock shock rebuild kit (see the 3rd picture down, at left). For proper geometry, eliminating bump-steer, I mounted the steering linkage to the inner hole on the knuckle arm and assembled the ball end to the knuckle arm without any spacer (the Kyosho manual specifies the use of one medium spacer to raise the ball). I was left with some unused length of knuckle arm and ball end thread, so I cut those off to save precious milligrams. Finally, the outer camber link was mounted to the upper hole in the c-hub (mounting it to the lower hole would give you too much negative camber on the outer wheel in a turn).
In the rear, I mounted Associated rear wheels directly to the axles, with pins, by simply removing the hex hub. It's a snug fit and requires a bit of squeezing to get on, but it increases the rear width to a full 13", the maximum allowed by NORRCA rules.
This wheel-mounted bearing setup with immobile spindles allows easier free-wheeling than the old spinning stub axle system. This translates to less rolling resistance which means higher top speed, lower amperage draw, and faster acceleration. I also end up with far less rotating mass than before, which also contributes to more brisk acceleration. Lastly, the decreased weight of the whole assembly means less unsprung weight, allowing for more responsive suspension action.
The rear springs are Duratrax Maxximum ST progressive-rate beauties. They are medium-firm when extended, but become very firm as you compress them. This change in spring rate is the result of having the spring wound more tightly in one section at the top (see the photo at top left).
Phase II Stats-At-A-Glance
The pictures above were taken of my very first Phase II setup. As I raced it, I tweaked it, and the specifics of shock oil/spring setup changed. Here you can see what I settled on for racing before Phase III came around:
(with everything except battery)
|Motor||DudeMann Extreme Racing tuned
|Batteries||Ballistic Sanyo 3000 (gen. 1)|
|Servo||Airtronics 94257 (0.06 sec, 110oz/in)|
(note custom setup -- will not work well w/ stock suspension)
|Light blue 2.5"
|Hole Shot M3
|Wheels|| One-piece T3 dish
|AE T3 Dish
Summing it all up...
In these pages you have the forumulae to turn the tough, incredibly inexpensive Traxxas Rustler into a lean, mean machine that can and will win races. Please be my guest and copy and extend any of the ideas you see anywhere on this site. I don't make all of this information public because I want to keep it to myself! My only request (demand, actually) is that you don't take credit for my ideas, and don't try to sell them! Now go check out Phase III!
Now go have some fun and help me to show the world that Traxxas cars & trucks ain't just toys!
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