Buildup -- Step 8: Steering & throttle servos

At last, final preparations towards making things move. Steering, throttle control & braking will define how this truck behaves, so this part of the buildup is not to be taken lightly. Make sure you center your servos with your radio gear before beginning.

I robbed the Hitec 945 coreless, metal-geared ultra-torque servo (153 oz/in, .12 sec at 6V) from the famous Valkyrie project. If this servo won't do the job, there aren't many that will. In my ongoing quest to create a precise steering assembly, I purchased an aluminum servo horn from Ofna (fig. 36).

Fig 36

The problem with this horn is that the holes for mounting linkage hardware are too small. That's ok, though, I thought -- I could drill out the desired hole (the outermost) and attach the ball stud with two nuts, one above, and one below. Unfortunately, the Kyosho ball stud doesn't have a long enough shank. I quickly went to one of my many Traxxas parts bins and pulled out a Rustler/Bandit/Stampede rear lower shock mounting ball stud and an end to mate to it (fig. 37, right -- Kyosho parts on left for reference). Now I was able to drill out the horn, and mount the stud with two 3mm nuts and Loctite as planned (figs. 38, 39), replacing the Kyosho ball end on the steering input linkage with the Traxxas one for a proper fit.

Fig 37	Fig 38	Fig 39

Mounting the servo to its mounting struts is effortless, as is mounting the throttle servo afterwards. I grabbed the first servo I could find to use for the throttle & brake, a Traxxas 2018. For more braking strength, though, I may later switch to a Traxxas 2055 ('Maxx stock steering servo) for a little more "oomph."

Fig 40	Fig 41