Guides / Design
Machining the parts that isolate a payload from the airframe
August 20, 2026
Every rotating part on an aircraft puts energy into the structure. The payload is the one place that energy is unwelcome, which is why almost every camera, lidar and survey sensor sits on isolators.
The rubber gets the attention. The machined parts either let it work or quietly stop it working.
What the system is doing
An isolator plus an isolated mass is a spring and a mass. That combination has a natural frequency. Above roughly 1.4 times that frequency the isolator starts attenuating, and below it, it does nothing useful. At the natural frequency itself it amplifies.
So the design job is to put the natural frequency comfortably below the disturbance you want to remove, and comfortably away from anything the flight controller or the structure is doing.
That means three numbers have to be known before the machined parts are designed:
- The isolated mass, including the plate, the sensor, the cables and any ballast.
- The isolator stiffness, from the manufacturer at that load.
- The disturbance frequencies, from the motor and propeller orders at normal hover RPM.
Mass matters as much as stiffness, which is why a damping plate that has been aggressively lightened can perform worse than a heavier one. This is one of the few parts on a UAV where removing weight is not automatically good.
The machined features that decide performance
Seat flatness. An elastomer loaded unevenly has a different stiffness on each side and it ages faster where it is pinched. Flatness of 0.05 mm across the seat is usually plenty, and a seat that was machined before the plate was pocketed may not be flat by the time it ships.
Bore or spigot fit. Most isolators locate on a hole or a stud. Oversize the hole and the isolator rocks and adds a mode. Undersize it and you preload the elastomer in a direction its maker never intended.
Preload height. Sandwich mounts are set by the gap between two plates. That gap is a machined dimension, and it is often the single dimension nobody toleranced. Call it out.
Symmetry. Four isolators on a plate whose centre of mass is not in the middle will droop and will have a different stiffness in each direction. Either move the mass or design the mount positions around it.
Cable strain relief. A cable bridging the isolators is a structural short circuit. It carries vibration straight across the joint and undoes the isolation. Design a service loop, and give it somewhere to be anchored on each side.
What the drawing should carry
| Feature | Call out |
|---|---|
| Isolator seat face | Flatness 0.05 mm, surface finish as machined |
| Locating bore or stud | Fit per isolator data sheet, stated by number |
| Plate to plate gap | Dimension and tolerance, not a reference |
| Isolated mass target | A note, so the assembler knows ballast is intentional |
| Isolator part number | On the drawing, because the fits come from it |
The isolator part number on the machined drawing is unusual and it is the detail that stops a well made mount being assembled with whatever rubber was in the drawer.
Materials
6061-T6 for the plates. Stiff, light, easy to machine and easy to anodise. Keep the isolated plate stiff rather than light, because a floppy plate has its own modes inside the range you are trying to isolate.
POM or PA66 for spacers and washers in the isolator stack, where you want a defined bearing surface without metal to metal contact. Nothing about an isolator stack wants a hard point.
Practical mistakes worth avoiding
- Isolating everything. Isolate the sensor, not the flight controller. The flight controller needs to feel the aircraft, and most modern units have their own internal damping designed around that.
- Isolators at the end of a long arm. They see amplified motion and they add a pendulum mode.
- Choosing the isolator by colour. Durometer and load rating decide the stiffness. Colour codes vary by manufacturer.
- Ignoring temperature. Elastomer stiffness changes with temperature. A mount tuned in a warm workshop behaves differently at 2,000 m on a cold morning.
- Forgetting the tether. If an isolator fails, a safety tether keeps the payload attached. That tether needs an anchor point machined into both plates.
Getting one made
Send the two plates, the isolator part number and the isolated mass. We will check the seats and the fits against the isolator data before quoting, flag anything we think will rock, and come back within 24 business hours. Flatness on a thin plate is a process question rather than a drawing question, and the answer is in designing for weight and in how the plate is held while it is cut.
See also: vibration and fatigue testing of drone arms and mounts for the test methods.
Frequently asked questions
What frequency does a drone isolator need to handle?
Mostly motor and propeller orders, which for a commercial multirotor sit somewhere between about 50 and 300 Hz. An isolation system works well above its own natural frequency, so the mount is usually tuned well below the lowest disturbance you care about.
Why does adding isolators sometimes make footage worse?
Because the isolated mass and the isolator stiffness set a natural frequency, and if that frequency sits inside the flight control bandwidth or near a structural mode, the payload swings instead of staying still. Isolation is a tuning job, not a part you bolt on.
Does the machined part matter, or just the rubber?
Both. The elastomer does the isolating, and the machined seats decide whether it is loaded the way its maker intended. A seat that is not flat or a bore that is oversize changes the stiffness and the damping you actually get.
Need this part quoted?
Send the model and the quantity. Price and lead time come back within 24 business hours.