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SAW M249


Busydad
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Hi, I'm after a bit of advice. My son has a airsoft Saw M249 which he has had for about a year. When he brought the gun second hand he had a faster gear set fitted & shimmed with a m130 spring also fitted. The motor runs off a 11.1 lipo battery with no mosfet fitted. We both rewired the gun completely with good quality 18awg silicone wire as the original wire was badly damaged & had a load of fixes where it had broken. The gun came with a nuprol high torque motor which stopped working after a couple of games so we replaced like for like & again the motor has stopped working after a few games. We have taken the motors out of the gearbox when they stopped working & wired them directly to the battery but they are dead so can only think the motors have burnt out (the fuse hasn't blown). We have checked the gearbox for tightnes of gears or jamming gears & all move freely. Is the motor to weak for the workload or is something else wrong. If so please can you advice.as we don't know what could be wrong. 

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Nuprol gear has a bad name. I’m not as savvy as Hangtight or Sitting Duck and the others when it comes to motors, but I would recommend the SHS high torque as a good motor, if you have the funds, I’d stretch to the ASG 30k as it’s very good.

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This is a question I'm posting more to further knowledge.
Could it be the lack of MOSFET? Though that the MOSFET was needed for 11.1 LiPo usage?
Or what? I have no idea lol.

I mean to kill off 2 motors without blowing the fuse, then have it not even work when wired directly to the battery. Seems like the motor internal wiring is breaking down (high voltage in thin wires and all that). 

Like I say though, no idea lol, just wondering why you wouldn't have a MOSFET yet use 11.1s

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We were told by the guy who tuned up the gearbox that we didn't need a mosfet. The worse the battery could do was to burn the contacts on the trigger which we have replacements. I'm just hoping it is the nuprol motors not being up to the job.

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2 minutes ago, Busydad said:

We were told by the guy who tuned up the gearbox that we didn't need a mosfet. The worse the battery could do was to burn the contacts on the trigger which we have replacements. I'm just hoping it is the nuprol motors not being up to the job.

 

ah yeah, you know what? I think I remember seeing something about burning the trigger contacts and just assumed it would also burn the motor out lol.

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What fps are you getting? An M130 spring should be good for well over 400fps. That combined with a high speed gear set will pull a lot of current. Do you know the gear ratio and rate of fire?

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You have an Airsoft gun that is close to being an illegal firearm, and with a better air seal certainly would be. Generally support weapons are field limited to a maximum of 350fps measured using 0.2g BBs. A M100 spring should get you to that output, and would put a lot less strain on the motor etc.

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5 hours ago, Busydad said:

Hi, thank you all for your advice. We will down grade the spring to a m100 & fit a ASG30k motor. We will keep our fingers crossed that it's third time lucky with the motor. 

 

The motor will be fine, but with a 30k motor on 11.1v and 16:1 gears you are just the wrong side of a safe rate of fire to avoid smashing gears and piston due to premature engagement.

A 22TPA motor (22k) will give you a solid 20-21 rps and run cool with a low current draw.

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