How come shooting on semi a few times reset the nozzle?

[KraftaN]

I've noticed that if I look into the hop-up unit through the magwell after shooting on full auto, the nozzle will be a little all over the place, but if I shoot some 3 shots on semi the nozzle returns to where it usually sits. I am curious as to why this happens?

 

Also, please forgive me if I used any terms incorrectly since I am quite new to Airsoft.

 

Edited December 20, 2022 by KraftaN

[Adolf Hamster]

when shooting on semi auto, the motor spools up, completes a cycle, the cutoff lever trips and the motor spools down.

 

as the time when the motor stops is controlled by a mechanically timed cam from the sector gear, it usually stops in a consistent place every shot, depending on friction etc in the box.

 

when firing in full auto, the cam is disengaged so the timing of when the motor stops running is dictated entirely by whenever you decide to release the trigger, which could be at any point in the cycle hence the nozzle stopping in seemingly random positions.

 

for a gun in good health, this is just a normal part of how they work.

 

depending on the state of the motor and gear train you can sometimes get instances where a gun might fire twice in semi auto (usually a fast motor that's not too strong at slowing down) as it's got enough momentum after the cutoff lever trips to freewheel round a whole second shot. likewise you can get the inverse of a motor that's not quite strong enough to do a standing start when the spring is compressed, which means if you get unlucky with the timing after a burst of auto, it'll stall when you try to fire the next shot.

 

this can be controlled by some mosfets, the term "active brake" means a mosfet that uses electronic braking on the motor when it's disengaged, think of how a cordless drill can stop almost instantly from full speed. can be useful for curing double taps but more often than not it'll cause the opposite issue, stopping the motor so quickly the cutoff doesn't reset properly making the gun lock-up on semi.

 

the term "precocking" applies to mosfets that intentionally run the motor a little longer than the normal cutoff time, by dialling this in you can have the gearbox stop with the spring very nearly about to release, with a motor strong enough to start in that state it means you can have a very quick response time (ie time between pulling the trigger and the gun going pew) without having to speed up the gun in auto (which can cause problems). if you take the same idea of a precocking timer and make it longer that's how you get burst fire.

 

some mosfets can even do "cycle detection", which basically means they don't bother using a cutoff at all and instead use (usually optical) sensors to keep track of where the sector gear is and control it's position. they're expensive but it means you can control where the gun stops wether you're firing in semi, burst or auto meaning it always stops in the same place.

[KraftaN]

42 minutes ago, Adolf Hamster said:

when shooting on semi auto, the motor spools up, completes a cycle, the cutoff lever trips and the motor spools down.

 

as the time when the motor stops is controlled by a mechanically timed cam from the sector gear, it usually stops in a consistent place every shot, depending on friction etc in the box.

 

when firing in full auto, the cam is disengaged so the timing of when the motor stops running is dictated entirely by whenever you decide to release the trigger, which could be at any point in the cycle hence the nozzle stopping in seemingly random positions.

 

for a gun in good health, this is just a normal part of how they work.

 

depending on the state of the motor and gear train you can sometimes get instances where a gun might fire twice in semi auto (usually a fast motor that's not too strong at slowing down) as it's got enough momentum after the cutoff lever trips to freewheel round a whole second shot. likewise you can get the inverse of a motor that's not quite strong enough to do a standing start when the spring is compressed, which means if you get unlucky with the timing after a burst of auto, it'll stall when you try to fire the next shot.

 

this can be controlled by some mosfets, the term "active brake" means a mosfet that uses electronic braking on the motor when it's disengaged, think of how a cordless drill can stop almost instantly from full speed. can be useful for curing double taps but more often than not it'll cause the opposite issue, stopping the motor so quickly the cutoff doesn't reset properly making the gun lock-up on semi.

 

the term "precocking" applies to mosfets that intentionally run the motor a little longer than the normal cutoff time, by dialling this in you can have the gearbox stop with the spring very nearly about to release, with a motor strong enough to start in that state it means you can have a very quick response time (ie time between pulling the trigger and the gun going pew) without having to speed up the gun in auto (which can cause problems). if you take the same idea of a precocking timer and make it longer that's how you get burst fire.

 

some mosfets can even do "cycle detection", which basically means they don't bother using a cutoff at all and instead use (usually optical) sensors to keep track of where the sector gear is and control it's position. they're expensive but it means you can control where the gun stops wether you're firing in semi, burst or auto meaning it always stops in the same place.

 

Thank you! This was really insightful and super well explained. I wish you nothing but the best of luck on the fields, and that your BBs strike true.

[Rogerborg]

That was an excellent explanation, but the tl;dr version is: don't worry about it.  Even the semi-auto reset position will be effected by battery voltage and amp supply, how cold the spring and how viscous the gearbox lube is, and whether you're dry firing, or actually shooting BBs to provide some back-pressure.  That last one in particular is why it's not worth trying to "tune" for a perfect nozzle position unless you're doing it by shooting the BBs you intend to use with the hop set for them, and pulling the mag repeatedly.

 

Airsoft is an inexact science, and while trick mosfets can give you a little more consistency, you really don't need them. If it cycles and shoots most of the time, it's good.