When do you need a MOSFET?

[bitofanidiot42]

I think I’ve learned what I came here for.

My conclusion is that a 7.4 Lipo will give a higher rpm than a 7.2 but the fps is always the same, I should probably get an m90 and hack away at the gearbox. It doesn’t matter too much for the rpm as my local site seldom allows full-auto.

 

As for MOSFET’s, they are for high power batteries to stop the carbon hurting the gun so quickly. They can be expensive and fancy and programmable or cheaper but not absolutely necessary for a cheaper gun as replacing the trigger contacts isn’t the end of the world (although they are becoming harder to find in the U.K.).

[Dan Robinson]

Seems fair, although, partly because of my job, id consider a basic mosfet an essential upgrade. 

 

If only to reduce unnecessary/easily preventable repairs going forward. 

[EDcase]

Yeah a MOSFET can be advantageous if you want fancy stuff like Burst, ActiveBreaking, Pre-Cocking etc.

If you don't need all that and you're using 7.4v batteries, something else will fail in the gearbox LONG before the trigger contacts become a problem so better to upgrade everything when you have to get in there to fix something.

 

 

Edited June 17, 2022 by EDcase

[Skara]

Depends on the application.

 

If you play cqb, where you need a snappy gun, then a programmable mosfet is a nice, semi mandatory upgrade.

 

If you don't play cqb and you use full auto quite a bit (e.g. woodland games) then a mosfet becomes less important, it's still s nice thing to have onboard but not strictly mandatory.

 

These two apply to 11.1v batteries as well, and while it is true that a 11.1v will accelerate wear and tear on trigger contacts, it will still take an awful lot of time to render them unserviceable.

[bitofanidiot42]

Thanks lads,

I think I’m getting a bit off topic but toy guns are so complicated…

Shimming a gearbox. 
I know what it is but how necessary, should I do it as soon as I get a gun or only if I notice an issue with the gears’ contacts?

[Adolf Hamster]

5 minutes ago, bitofanidiot42 said:

 I know what it is but how necessary, should I do it as soon as I get a gun or only if I notice an issue with the gears’ contacts?

 

it's generally best to leave a gun alone especially if it's your first/only pew.

 

whilst a lot of ootb pews have less than perfect shimming, they're generally good enough for purpose. the risk is opening up the gun first time is fraught with the potential for making mistakes on reassembly and messing something up. whilst that's just part of the learning process i can say from experience (having not listened when being told this back in the day) that the walk of shame gets real old the tenth time you've done it when your latest build/experiment hasn't gone to plan and left you with a pew that's either performing terribly or straight up not working at all.

[EDcase]

Yep, as Hamster said, best not to tinker at first and just enjoy how it comes (unless it performs really badly then inform retailer)

Changing plugs to Deans is good if you know how but not critical.

Wait until you have a second toy as backup or if something breaks before exploring the wonderful world of teching.

 

 

Edited June 17, 2022 by EDcase

[Rogerborg]

13 hours ago, bitofanidiot42 said:

So 7.2 Nimh would give lower fps than a 7.2 lipo?

 

Oh, crikey, I've just noticed that you said fps rather than rps.

 

The battery and motor are irrelevant to the fps / kinetic energy of the BB.  They'll either pull the piston and spring back until it releases, or they wont.  You'll get the same energy each shot[*], all that will change by shoving more electrons around is the rate of fire and trigger response.

 

[*] Technically, if you're running the gun so fast that the sector gear pre-engages with the piston before it's all the way forward, you'll get lower energy, but that's the least of your concerns at that point since your piston and/or gears are going to shred.  If you ever put together a gun that can do that, then that's a case where you could use a smartish mosfet to reduce the rate of fire, while still retaining snappy semi-auto response.

 

Shimming your is satisfying, but there's always the possibility that you'll make it worse than the Chinese sweatshop child that did it in 30 seconds.  I'd echo the sentiment that it's something to do once you have two usable guns.  A quick-change spring makes the process of getting the gearbox apart and back together a lot less fraught. Some strong flat magnets are handy to stick under it to hold everything in place.

 

As usual, Luke at Negative cuts through the woo and just does it pragmatically, while tripping balls on red wine and gabapentin.

 

 

[Nick G]

Never, no one ever needs one of the things. Granted I am an absolute technophobe and see them as pointless stupid electronic crap that will fail at some point ! 🤣