Motor Overspin

[VeniVidiVici]

So recently I was at the field and while in semi I noticed that instead of single shot I was getting two round burst. I was told that this was a gearbox issue. Any other possible reasons behind the 

 

[Sitting Duck]

Gun & battery used ???

In "general" overspin starts to occur at say 20rps

but all guns overspin/cycle a smidge to what some say is pre-cocking

double firing is when a gun is firing so quickly it pre-cocks or overspins so much that at times it double fires

often on most shots - this tends to happen at around 25 rps in a std 350fps gun

This speed or rps of pushing the gun's speed is basically the gun "talking to you" in a way

continue to push this at say 25rps long term or foolishly push it further at 30rps

then you can get PME where the piston & sector meet earlier than expect and munch up

as piston gets caught by sector before fully returning.....

That is the general rule of thumb - roughly speaking.....

HOWEVER......

IF gun is quite old or well used then the Cut Off Lever (usually weak alloy than steel)

if you have a well worn COL it fails to pop the trigger trolley properly or fails to raise/pop the trolley switch

and thus double fires or triple fires or just goes full auto regardless of fire selector

So you could get overspin or double/triple firing or in bad cases full auto on semi with a badly worn COL

So depending on how fast gun cycles you either need to:

tone down the juice a bit if running fast with 11.1v or high speed motor

or

replace a worn Cut Off Lever - a nice steel hard wearing one like SHS COL

An AB mosfet "might" help reduce the overspin a bit but not if your COL is shagged

(it will only brake the motor if COL operates correctly)

most of the COL stuff applies to guns that actually have one of course

 

[Rogerborg]

I got double-firing on semi simply by putting in an 11.1V high-capacity / high C battery.  You can have too much of a good thing.

 

[VeniVidiVici]

Gun & battery used ???

In "general" overspin starts to occur at say 20rps

but all guns overspin/cycle a smidge to what some say is pre-cocking

double firing is when a gun is firing so quickly it pre-cocks or overspins so much that at times it double fires

often on most shots - this tends to happen at around 25 rps in a std 350fps gun

This speed or rps of pushing the gun's speed is basically the gun "talking to you" in a way

continue to push this at say 25rps long term or foolishly push it further at 30rps

then you can get PME where the piston & sector meet earlier than expect and munch up

as piston gets caught by sector before fully returning.....

That is the general rule of thumb - roughly speaking.....

HOWEVER......

IF gun is quite old or well used then the Cut Off Lever (usually weak alloy than steel)

if you have a well worn COL it fails to pop the trigger trolley properly or fails to raise/pop the trolley switch

and thus double fires or triple fires or just goes full auto regardless of fire selector

So you could get overspin or double/triple firing or in bad cases full auto on semi with a badly worn COL

So depending on how fast gun cycles you either need to:

tone down the juice a bit if running fast with 11.1v or high speed motor

or

replace a worn Cut Off Lever - a nice steel hard wearing one like SHS COL

An AB mosfet "might" help reduce the overspin a bit but not if your COL is shagged

(it will only brake the motor if COL operates correctly)

most of the COL stuff applies to guns that actually have one of course

Click to shrink...

Rifle I use is a modded krytac crb mk2 with a 45k motor and Prometheus bucking and inner barrel. I use it with a three cell 11.1 lipo.

By the way you are describing the issue it seems like the cut off lever is having issues because I’ve had moments where in semi it went full auto. Do you know how much it would cost for a new cut off lever

I got double-firing on semi simply by putting in an 11.1V high-capacity / high C battery.  You can have too much of a good thing.

Click to shrink...

I’ll try with a 9.6

 

[Adolf Hamster]

you're using a 45k motor on 11.1 and your gearbox hasn't exploded?

colour me impressed.