When assembling or maintaining an FPV drone,many enthusiasts tend to overlook the selection and installation of motor screws.However,these seemingly tiny fasteners are directly related to the flight safety and performance of the entire aircraft.During high-speed rotation,motors endure continuous vibration and tension.If the screw length is improper or the installation is incorrect,it can lead to minor issues like loosening and resonance,or severe problems such as piercing the stator windings,causing a short circuit and burning out the motor,which poses a significant risk.
If you are not yet familiar with FPV motors, you can first read our FPV Motor Guide before continuing to learn the details of motor screw installation.
Therefore,mastering the specifications,length calculation methods,material selection,and correct installation procedures for motor screws is a fundamental skill that every FPV DIY enthusiast must possess.Only by selecting and installing every screw correctly can a solid foundation of safety be established for the aircraft,making every flight more reliable and secure.
Ⅰ.How is the motor mounted on the frame?
Before choosing the right FPV motor screws,it is essential to first understand how the motor is secured to the frame.As the motor rotates at high speeds,it is subjected to constant vibration and tensile forces.The screws must not only match the motor base but also accommodate the thickness of the carbon fiber arm to ensure a secure installation.Understanding the basic structural knowledge,such as the motor base's mounting hole pattern,screw hole depth,and the difference from propeller screws,is a prerequisite for correctly purchasing screws later on.
1. Mounting Hole Pattern
Most FPV brushless motor bases are designed with symmetrically distributed mounting holes to firmly secure the motor to the carbon fiber arm.There are two common mounting hole patterns:16×16 mm,often found on mainstream 5-inch class motors like the 22XX,23XX,and 24XX series;and 12×12 mm,commonly used for mini motors from 08XX to 14XX(such as those for Tiny Whoops or Toothpick-style drones).
Knowing the motor base's mounting hole pattern helps in correctly selecting a matching carbon fiber arm and appropriately sized screws during assembly,preventing unstable installation due to mismatched hole patterns or length errors.
2. Screw Hole Depth
Each screw hole in the motor base has a specific depth(usually 3 to 5 mm,varying by brand)for thread engagement.If the screw length exceeds the hole depth plus the carbon arm thickness,it could pierce the stator windings,leading to a short circuit and burning out the motor.Conversely,if it is too short,it will not provide sufficient fastening force.
3. Arm Thickness
In addition to the motor base structure,the thickness of the carbon fiber arm also influences screw selection.Common FPV drone carbon arm thicknesses range from 2 to 5 mm.Thicker arms require longer screws to ensure adequate thread engagement,while using screws that are too long on a lightweight frame might pierce the motor's stator windings.Knowing the arm thickness is crucial for accurately calculating the appropriate screw length.
4. Distinguishing Between Motor Mounting Screws and Propeller Lock Nuts
It is important to note that motor mounting screws are inserted from the bottom of the motor,through the carbon arm,and into the motor base to secure the motor to the arm.Propeller lock screws/nuts,on the other hand,are used to fasten the propeller blades to the motor shaft.Their specifications and purposes are completely different and they should not be used interchangeably.
Ⅱ. Common FPV Motor Screw Specifications
FPV brushless motors of different sizes vary significantly in base thickness and mounting hole patterns,thus requiring different diameters and lengths for their motor mounting screws.Choosing the wrong screws can not only lead to a loose motor or installation failure but may also cause the screw to pierce the windings and burn out the motor if it is too long.
Below is a reference table of common FPV motor models and their corresponding screw specifications,which can serve as a quick guide for beginners:
Motor Size (Example) | Mounting Hole Pattern | Screw Diameter | Typical Arm Thickness | Recommended Screw Length (by arm thickness; add soft washer) | Typical Frame Type / Use |
1103 / 1105 | 9×9 mm (some 12×12) | M2 | 2–2.5 mm | 4–5 mm | 2–2.5" Toothpick / Tiny |
1204 / 1207 / 1303 | 12×12 mm | M2 | 2–3 mm | 5–6 mm | 2.5–3" |
1505 / 1507 | 12×12 mm (some 16×16) | M2 | 2–3 mm | 5–7 mm | 3–4" Lightweight |
1804 / 1806 / 2004 | 16×16 mm | M2 | 2–3 mm (thin) / 3–4 mm (thick) | 5–6 mm (for 2–3 mm arm) / 6–7 mm (for 3–4 mm arm) | 3–4" LR |
2203 / 2205 / 2207 | 16×16 mm | M3 | 4–5 mm | 6–8 mm | 5" Racing |
2306 / 2307 | 16×16 mm | M3 | 4–5 mm | 6–8 mm | 5" Freestyle / Race |
2507 / 2508 | 16×16 mm | M3 | 4–6 mm | 8–10 mm | 6–7" LR |
2806.5 / 2807 | 16×16 mm | M3 | 5–6 mm | 10–12 mm | 7" LR / Cruise |
3110 / 3508 / 4004+ | 19×19 / 25×25 mm | M3 (some M4) | ≥5 mm | 10–12 mm+ | 8"+ LR / CineLifter |
Note:This table provides general recommendations.Individual models may have non-standard hole patterns or depths.Please refer to the manufacturer's specifications or use calipers for actual measurements.
Ⅲ.How to Choose the Right Screws for Your FPV Motor?
Before installing the motor,selecting the correct length and specification of FPV motor screws is a critical step in ensuring flight safety.Here are practical methods for selecting and verifying the appropriate screws:
1. Confirm the Motor Base Screw Hole Specifications
Before purchasing motor screws,you must first confirm the specifications of the motor base's screw holes,including the screw diameter and mounting hole pattern.You can check the product specification sheet provided by the motor manufacturer,which usually indicates the compatible screw model(commonly M2 or M3).If the manual is unavailable,you can make a rough judgment based on the motor size:small motors below 14XX mostly use M2 screws,18XX to 20XX models typically use M2,while mainstream quadcopter motors of 22XX and above predominantly use M3.Accurately confirming the specifications can prevent issues like the screw not fitting or thread stripping.
2. Measure the Carbon Fiber Arm Thickness and Motor Base Hole Depth
After determining the screw diameter,you also need to accurately measure the required screw length.Use calipers to measure the thickness of the frame's carbon fiber arm(commonly 2-5mm).Then,combine this with the depth of the motor base's screw hole(usually 2.5-4mm).Use the formula:Screw Length≈Arm Thickness+Effective Thread Engagement Depth(typically Hole Depth-0.5~1mm safety margin).
For example,if the arm thickness is 4 mm and the screw hole depth is 3 mm,allowing for a 0.5–1 mm safety margin,a 6 mm screw(a common size)is recommended.This ensures sufficient thread engagement without bottoming out and piercing the windings.This calculation method prevents screws from being too long and piercing the stator windings,while also avoiding screws that are too short and provide insufficient clamping force.
3. Check for Washers or Vibration Dampeners
If you install soft mounts or washers between the motor and the carbon arm,you must also account for the thickness of these additional components.The presence of a washer increases the distance between the motor and the arm.If you still use the original length screw,the thread engagement may be insufficient,leading to a weak connection.For example,if a 6mm screw was originally recommended,adding a 1mm thick washer would require using a 7mm screw to ensure adequate engagement length and clamping strength.
4. Select the Appropriate Material and Screw Head Shape
After confirming the screw dimensions,you also need to choose the right material and apply threadlocker.Common motor screw materials include stainless steel(corrosion-resistant),alloy steel(high strength),and titanium alloy(lightweight but more expensive).It is generally recommended to prioritize high-strength and cost-effective stainless steel or alloy steel.
Additionally,pay attention to the screw head shape.The most common motor mounting screws are button head or pan head with a hex socket.In space-constrained situations,low-profile screws may be chosen to avoid interference with the propeller or motor bell.Avoid using flat head(countersunk)screws,as their conical base creates stress concentrations on the carbon fiber plate,which can lead to cracks or damage to the arm over time.
It is also recommended to apply a small amount of medium-strength threadlocker(blue Loctite 242/243)to the middle of the threads to effectively prevent loosening caused by high-frequency vibrations.When tightening,be mindful of the feel and use moderate force to avoid stripping the threads or damaging the motor base's threaded holes.
Recommended Screw Length Reference:
Arm Thickness | Screw Hole Depth | Safety Margin | Recommended Screw Length |
2 mm | 3 mm | 0.5 mm | 4.5 mm → 5 mm |
3 mm | 3 mm | 0.5 mm | 5.5 mm → 6 mm |
4 mm | 3 mm | 0.5–1 mm | 6–6.5 mm → 6 mm |
5 mm | 4 mm | 1 mm | 8 mm |
Ⅳ.What are the Installation Steps for FPV Motor Screws?
After selecting FPV motor screws of the appropriate length and specification,correct installation is equally crucial.Improper installation can not only cause the motor to become loose,eccentric,or even detach during flight,but it can also damage the carbon arm or the motor itself.The following is the recommended standard installation procedure:
Step 1:Prepare Necessary Tools and Materials
Before starting the motor installation,prepare the necessary tools and auxiliary materials.Common tools include a hex driver or Allen key that matches the screw size(e.g.,M2,M3),medium-strength threadlocker(blue Loctite)to prevent screws from loosening due to flight vibrations,and optional washers to protect the carbon fiber arm surface and increase friction.It is also advisable to have calipers on hand to confirm that the screw length is appropriate for the motor and arm thickness,thereby avoiding errors during installation.
Step 2:Perform a Test-Fit to Confirm Screw Length
Before the final installation,perform a dry fit(test installation)to confirm the screw length is correct.Do not apply threadlocker at this stage.Pass the screw through the carbon arm and into the motor base.After tightening it fully,check if the screw turns in smoothly without bottoming out against the windings.You can gently touch the bottom of the motor to feel if the tip of the screw is protruding.If it is,the screw is too long and must be replaced with a shorter one to avoid piercing the motor windings and causing a short circuit.
Step 3:Apply a Small Amount of Threadlocker
Once you have confirmed the screw length is appropriate,apply a small drop of medium-strength threadlocker(blue Loctite)to the middle of each screw's threads.This will effectively prevent the screws from loosening due to high-speed vibrations.Be careful not to apply threadlocker to the screw head or in excessive amounts,as it can be squeezed into the motor during tightening,contaminating the stator or increasing rotational resistance,which can affect motor performance.
Step 4:Tighten Evenly in a Cross Pattern
Place the motor correctly on the arm and tighten the four mounting screws sequentially in a diagonal(cross)pattern.First,lightly screw each one into place,then gradually and evenly tighten them.Avoid fully tightening one side first,which could cause the motor base to tilt.Control your force when tightening;the correct feel is when you sense resistance and the screw no longer advances easily.This ensures a secure fit while preventing thread stripping or damage to the motor base's threaded holes.
Step 5:Post-Installation Inspection
After all screws are tightened,a thorough post-installation check is necessary.Gently wiggle the motor by hand to confirm there is no looseness or gap between it and the arm.Then,spin the motor by hand to ensure it rotates smoothly without any eccentricity or strange noises.Once everything checks out,let the threadlocker cure.It generally takes about 5-10 minutes for an initial set,and 6-24 hours to fully cure.It is recommended to avoid aggressive flying immediately after installation.
Ⅴ.Daily Maintenance and Inspection of FPV Motor Screws
Even if you have used the correct FPV motor screws and installed them according to specifications,regular maintenance and inspection are still necessary to ensure they remain secure under high-RPM vibrations.Neglecting routine screw checks can lead to a motor detaching,propellers hitting the frame,or even a crash during high-speed flight.
Here are some common maintenance and safety check points:
1. Quick Pre-Flight Check
Performing a brief safety check of the motor screws before every flight is very important.You can start by gently wiggling the motors by hand to check for any looseness or abnormal gaps.Then,inspect the screws at the bottom of the motor for any missing,loose,or visually abnormal signs.Finally,spin the motors by hand and feel for smooth rotation without any eccentric wobble or strange noises.If you find any issues,you should immediately ground the drone and perform maintenance to avoid damage caused by a loose motor in flight.
2. Periodically Check Screw Torque
In addition to the daily pre-flight checks,it is also recommended to periodically re-check the torque of the motor screws.Generally,after every 10-20 hours of accumulated flight time,all motor screws should undergo a comprehensive tightness check.Using a torque driver can help avoid over-tightening,which can cause stripping,or under-tightening,which leads to loosening.If you find a loose screw,first clean off any old threadlocker residue,then reapply a proper amount of new threadlocker and tighten it according to the specified procedure to ensure long-term flight reliability.
3. Timely Replacement of Damaged or Rusted Screws
If a motor screw shows signs of a stripped head,cracks,rust,or deformation,it must be replaced immediately to prevent it from breaking and detaching due to insufficient strength during flight.It is recommended to use screws made of stainless steel or titanium alloy,as they offer better corrosion resistance and higher strength,reducing fatigue damage over long-term use.It's also a good idea to carry a spare set of motor screws for timely replacements after a crash at the field or outdoors.
4. Cleaning and Maintenance Tips
Good cleaning and maintenance practices can help extend the service life of both the motor screws and the motor itself.After each flight,use a brush or compressed air to clean dust,sand,and debris from around the motor,preventing foreign objects from getting stuck in the screw holes and affecting the clamping force.Do not use corrosive lubricants,as they can reduce the effectiveness of the threadlocker.It is also not recommended to frequently disassemble and reassemble the motors,as this can cause wear on the threaded holes,affecting the screw's holding power.
FPV Motor Screw Maintenance Checklist:
Task | Frequency | What to Check | Action |
Pre-Flight Quick Check | Before every flight | Wiggle motor, check for loose or missing screws | Stop flying if any issue is found |
Torque Recheck | Every 10–20 hours of flight time | Use torque driver to check screw tightness | Remove old threadlocker, reapply and retighten |
Screw Condition Check | Monthly or after crashes | Rust, deformation, stripped heads | Replace immediately if damaged |
Cleaning & Care | After every flight | Remove dust/debris, prevent corrosion | Avoid corrosive lubricants or frequent disassembly |
Ⅵ.Frequently Asked Questions(FAQ)
Q1:If I lose one motor screw,can I still fly with just three?
It is not recommended.Missing one screw will cause uneven force distribution on the motor,leading to wobbling or resonance during high-speed rotation.This can accelerate the loosening or even fracture of the remaining screws,posing a safety hazard.You should replace the missing screw before flying.
Q2:The screw hole on my motor base is stripped.Can it be repaired?
You can try using a slightly longer screw of the same specification to engage deeper threads,or use a thread repair compound and then re-tap the hole.If the damage is severe,it is best to replace the motor.
Q3:Are titanium alloy screws better for FPV motors?
Not necessarily.Titanium alloy is lightweight and has high strength,but it is relatively less ductile and can fracture suddenly upon strong impact.For beginners,stainless steel or alloy steel screws are more suitable as they are cheaper and have better toughness.
Q4:Why is blue threadlocker recommended instead of red?
Blue threadlocker is medium-strength and can be disassembled with hand tools,making it suitable for motor screws that may require maintenance.Red threadlocker is high-strength and is nearly impossible to disassemble manually,which is not ideal for future maintenance.
Q5:How can I determine if the screw length is correct without disassembling anything?
You can use the"test-fit method":pass the screw through the carbon arm and into the motor base.Check if the tip protrudes from the bottom.Then,spin the motor to ensure there are no strange noises and wiggle it to confirm there is no looseness.
Q6:Can motor screws be reused?
They can be reused a limited number of times,but long-term reuse is not recommended.Repeated tightening can wear down the threads and reduce their strength.If you notice any stripping,rust,or deformation,you should replace the screws with new ones.
Q7:What should I do if a screw breaks off inside the motor base?
Do not try to force it out by twisting.You can use a small drill bit to drill out the broken section and then use needle-nose pliers to pull it out,or use a screw extractor.If the threads in the hole are damaged,it is recommended to replace the motor.
Q8:Are motor screws from different brands interchangeable?
Most are interchangeable,but you still need to confirm the screw diameter,mounting pattern,and hole depth.Some brands may have non-standard hole patterns or shallower holes,so you should check the specifications or measure them before purchasing.
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