The Futaba S9157 was designed and released intended for use in airplanes. With impressive specs such as 425 oz. in. of torque at 6.0v and a 60° transit time of 0.14 seconds it quickly caught our eye. I placed my order as soon as I saw the specs. I had previously been using the Futaba S9156 which has 340 oz. in. of torque at 6.0v which was plenty of power to steer by Berg based comp rig where I wanted it. However the transit time of the S9156 is slower and had been my only complaint up to that point, and more power never seems like a bad thing when you are talking about steering in a crawler.

Installation: 

The S9157 arrived and the first thing I noticed was that they reinforced the case by adding two more screws that go in from the top of the servo. These screws were added to help fight any case deflection that may occur when the servo is delivering maximum power. I bolted up the same servo horn I had been using previously with my S9156.

Performance:

The steering configuration on my Berg based comp rig uses a high steer knuckle designed for an AX-10. I have the tie rod mounting point moved back towards the king pin about ¼” to give me more clearance and better steering throw. This does require more power from the servo to move the wheels but with a good servo it has never been a problem. I run 8 oz of lead weight on each front wheel, so this does not add up to a rig that is easy to steer.

Upon turning the truck on for the first time I also noticed a significant reduction in the typical “whine” you normally hear from high power servos, less noise is always a plus. After the first run I was extremely pleased with the servo’s performance. The quicker transit time and 25% more power were clearly apparent. No matter the situation I was not able to stall the servo out, even when the entire weight of the vehicle was resting on the face of a single wheel. The only downside that I found was that the servo horn I had been using just wasn’t going to cut it. I had nearly bent the tip of the horn at a 90° angle and had elongated the hole to the point that I ripped to 3mm screw right out. A high quality servo horn is strongly recommended with this servo, I chose to install a Robotronics servo horn and have to say that it is the perfect match for this servo. Overall this is the best servo I have tested to date.