Post by Honus on Sept 15, 2014 3:53:39 GMT
On the Predator AVP cannon project I used a RobotZone Power Gearbox to raise and lower the cannon arm. Due to the high leverage ratio of the arm I needed a super powerful servo to move it and this fit the bill perfectly.
The model is used is the SPG400A Top Mount with a 3.8:1 gear ratio. The nice thing about these gear drives is they are designed to be used with standard size servos. The servo has a brass gear attached to its output shaft and this in turn drives a machined Aluminum gear and multiplies the servo torque. The gearbox frame is machined Aluminum and there are dual bearings supporting the hardened stainless output shaft. The large Aluminum gear is attached to the output shaft with a clamping hub that mates to the rest of the Actobotics product line. The gearbox output shaft has a small potentiometer fitted to it so the gearbox output shaft turns the same amount as a normal servo. The only tricky part in building the kit is you need to disassemble your existing servo and modify it. The internal potentiometer needs to be disconnected and the servo needs to be modified for 360 degree rotation. This really isn't that hard to do but if you're not comfortable modifying the servo ServoCity will do it for you.
The servo I chose to power the gearbox is the Hitec HS-7955TG. This is a top of the line high torque programmable digital servo with coreless motor, Titanium gears and dual ball bearings supporting the output shaft. While the official specs show this servo rated at 6.0V Hitec has confirmed it can be powered at 7.4V. At 6.0V its torque output is 333 oz/in. Multiply that by 3.8 for the gearbox and you get a torque output of 1265.4 oz/in @6.0V. The biggest gear ratio available for the SPG400A is 7:1 and with that gear the output at 6.0V would be 2331 oz/in.- that means with a one inch output arm the servo would just be able to lift 145 pounds (that's technically the stall torque.) That is one powerful setup!
If you need a powerful servo drive for your project this is certainly an extremely potent combination at a very reasonable cost.
The model is used is the SPG400A Top Mount with a 3.8:1 gear ratio. The nice thing about these gear drives is they are designed to be used with standard size servos. The servo has a brass gear attached to its output shaft and this in turn drives a machined Aluminum gear and multiplies the servo torque. The gearbox frame is machined Aluminum and there are dual bearings supporting the hardened stainless output shaft. The large Aluminum gear is attached to the output shaft with a clamping hub that mates to the rest of the Actobotics product line. The gearbox output shaft has a small potentiometer fitted to it so the gearbox output shaft turns the same amount as a normal servo. The only tricky part in building the kit is you need to disassemble your existing servo and modify it. The internal potentiometer needs to be disconnected and the servo needs to be modified for 360 degree rotation. This really isn't that hard to do but if you're not comfortable modifying the servo ServoCity will do it for you.
The servo I chose to power the gearbox is the Hitec HS-7955TG. This is a top of the line high torque programmable digital servo with coreless motor, Titanium gears and dual ball bearings supporting the output shaft. While the official specs show this servo rated at 6.0V Hitec has confirmed it can be powered at 7.4V. At 6.0V its torque output is 333 oz/in. Multiply that by 3.8 for the gearbox and you get a torque output of 1265.4 oz/in @6.0V. The biggest gear ratio available for the SPG400A is 7:1 and with that gear the output at 6.0V would be 2331 oz/in.- that means with a one inch output arm the servo would just be able to lift 145 pounds (that's technically the stall torque.) That is one powerful setup!
If you need a powerful servo drive for your project this is certainly an extremely potent combination at a very reasonable cost.
