TECHNICAL SUPPORT
Published 2026-03-17
When engaging in product innovation, especially when making robots, robotic arms, or various automated gadgets, the pairing ofservos and connecting rods is definitely the core that cannot be avoided. But you will definitely find that putting them together is not as simple as you think. Either theservocan't move, the connecting rod is stuck, or it's shaking like Parkinson's disease. It's a good idea but it just can't move. Don't worry, we will solve these problems one by one.
The most common and safest way to connect the connecting rod to the steering gear output head (that is, the steering wheel) is to put it on directly and then lock it with the small screws that come with the steering wheel. You have to make sure that there is no empty space at this connection point, that is, there can be no wobbly gaps. Think about it, if the connection is wobbly, then the movement of the rear connecting rod must be full of errors, and there is no way to control it accurately.
Sometimes the movement of theservoneeds to drive a slider or change the direction of movement, and direct connection alone is not enough. At this time, you have to use adapters such as fisheye bearings or couplings. For example, a fisheye bearing is first fixed on the steering wheel, and the connecting rod is then inserted into the bearing. This can not only transmit power but also adapt to swings in different directions. If you can’t buy a suitable one on the market, you might as well try using a 3D printer to draw an adapter yourself. Many makers do this. It’s low-cost and fits your needs.
The length of the connecting rod directly determines how fast and powerful your mechanism can run. Behind this is the lever principle at work. Simply put, the longer the connecting rod, the greater the range of motion at the end, but the greater the effort required by the steering gear. In turn, the linkage is shorter and the end range of motion is smaller, but it feels powerful. So you have to calculate whether you need speed range or torque power. You have to find a balance between the two.
I suggest that you don’t rush into metal processing directly. First make a simple model with cardboard or wooden sticks, put the servo on it, and move it with your hands to simulate the movement trajectory. In this way, you can intuitively see whether the connecting rod will hit other parts during the entire movement and whether the movement is the effect you want. This method is very crude, but it is very effective and can help you save a lot of wasted money on repeatedly modifying metal parts.
If the completed mechanism cannot move, or it gets stuck halfway through movement, the first reaction must be that the servo is out of power. At this time, you need to calmly analyze whether the torque is really insufficient, or the structure of your connecting rod makes it unable to work hard. For example, at a certain angle, the load just completely presses on the steering gear, and the required torque instantly increases several times, and it will definitely not be able to drive it.
It will be easier to find the reason. If it is indeed overloaded, it is the easiest way to directly replace the servo with a larger torque. But sometimes adjusting the fulcrum position of the connecting rod and making the moment arm longer can also save labor. Or add a spring to the structure to help it share a little gravity during the most strenuous part of its journey. This is also a very clever method. This idea is used in many complex robotic arms.
The made thing can move, but it moves every now and then, and the sound of the motor is hoarse, which makes me feel distressed just looking at it. This is most likely due to mechanical interference. You have to carefully check the entire process of movement to see if link A and link B collide at a certain angle, or if the link rubs against the fuselage frame. When designing, you have to leave enough space and don't dig too hard.
In addition to interference, another common cause is joint instability. If the connecting rod's rotating shaft is screwed directly through two plastic parts, it will not turn if it is tightened too tightly, and it will wobble if it is loosened. The professional approach is to use copper inserts or flange bearings, which can ensure smooth rotation and eliminate gaps. If conditions are limited, you can add a thin shim between the screw and the connecting rod to adjust it so that it can rotate freely without significant shaking. This step requires patience.
Fixing is the easiest thing to ignore, but it is also the most fatal. The servo itself must be firmly fixed on the bracket, and all four screws must be tightened. If the servo body is shaking, then all its power will be removed. It is strongly recommended to use a little bit of screw glue on the small screw that connects the steering wheel and the connecting rod, otherwise the machine will vibrate, the screw will loosen and fall out, and the entire mechanism will fall apart.
For the hinged fixation between connecting rods, if fisheye bearings are used, the bearing itself is threaded and can be directly screwed on the connecting rods and then locked with nuts. If the connecting rod is drilled by yourself, after inserting the screw, it is best to use a lock nut (the kind with a ring of nylon inside), and do not lock the screw to the bottom, but leave a little gap to allow the connecting rod to rotate freely. This degree must be grasped well. If it is too tight, it will not turn, if it is too loose, it will be empty.
The hardware is all installed, don’t rush to power it on yet. Use your hand to move the servo output arm to the middle position (usually 90 degrees), and then install the connecting rod to ensure that your mechanism is positive in the initial state. This step is called "back-to-center installation", which can avoid deviation as soon as the power is turned on. If possible, use a servo tester to debug, which is much safer and more convenient than directly connecting to the main control board.
Slowly increase the range of motion of the servo, observe whether the entire stroke is smooth, and listen for any abnormal friction sounds. Put your hand on the servo to feel the temperature. If it gets hot quickly, it means it has been holding back its strength and there must be something wrong. Write down the best motion parameters found during the debugging process, such as the maximum and minimum angle limits, and running speed, so that you will have a basis for subsequent programming control.
Having mentioned so many pitfalls in debugging, which aspect is the most troublesome for you when you are working on your own project? Is it uncertainty when calculating dimensions or repeated rework during installation? Welcome to share your experience in the comment area, and let’s talk about the servos and connecting rods that we have struggled with over the years. If you find the article useful, don’t forget to like it and forward it to your friends who are also creating!
Update Time：2026-03-17
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