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ryanassis

Help Im a massive Newbie. just broke my gun

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Right so about a week ago I installed a new SHS high torque motor and an M120 spring into my G&G CM16 (Non BB)

all was working well however the shimming was a bit off and it squeaked a bit so I decided to reshim....

I spent a good 2 hours sorting it out and making sure it wasn't too tight (Screwed the gearbox shut every time to check)

I go to put the motor back in and shoot it.... works fine for a bit.... stops working, Now me being a huge moron I decide to keep pulling the

trigger and still nothing

 

So I remove the motor from the gun and leave it for like 20 minutes. I then go back and just plug the motor in (not inside the gearbox) and instantly

the motor spins up without my pulling the trigger. And ive just blown my mosfet... great

I then spend the next few hours creating a new wiring harness without a mosfet and just doing it the good ol' way. and yet again I put it back together

pull the trigger once and BAM my entire wiring harness has just melted completely. What the actual F***

 

Now I don't see how it could be the shimming as it is not tight at all! I get around 2 spins when doing it by hand and there is even some slight side to side movement in the gears (not visible but I can tap the gears and they move)

What do I do now? Im not sure I want to buy another mosfet as ill just blow it again. what should I check first?

 

BTW im using a 7.4 Turnigy nanotech 2200mah 35-70C LIPO

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Guest alberty

Just to check, did you start shimming your gears in relation of the bevel gear and the pinion gear? If not, that's an important thing to consider.

 

Do you have another battery to try? I notice that your lipo that you listed has a pretty high C number, stepping down would be something to try out to see if that works safely.

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I was using ASG Ultimate Silver Plated wire...

 

I adjusted the motor hight when shimming the bevel so it shouldn't have had to change once put together.

I totally forgot this but when the wires melted there was no spring or anything in the gun. Just the gears which makes this even

more odd seeing as I could get at least 2 spins by hand and the motor couldn't turn it.

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things I would check off the top of my head (ie. things I have done)

make sure the wires aren't getting crimped/pinched somewhere. can cause things to get damn hot really fast (as with my brothers Sig)

make sure you have the motor contacts on the proper sides. (worked on a buddies gun where that happened)

 

Another wiring issue might be that you are grounding out to the body somewhere. Generally this will cause a short when working with metal bodied devices like lamps but I don't know if your G&G is metal bodied or not.

 

Something else that just occurred to me though I don't run lipos I have done a lot of wiring (former VW bug owner) is to check the rating on the wire. Could be your dumping too much juice into an inferior wire and it just cant take it.

 

 

But, I think if the motor isnt turning or at least kicking but not rotating I would check the polarity again.

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things I would check off the top of my head (ie. things I have done)

make sure the wires aren't getting crimped/pinched somewhere. can cause things to get damn hot really fast (as with my brothers Sig)

make sure you have the motor contacts on the proper sides. (worked on a buddies gun where that happened)

 

Another wiring issue might be that you are grounding out to the body somewhere. Generally this will cause a short when working with metal bodied devices like lamps but I don't know if your G&G is metal bodied or not.

 

Something else that just occurred to me though I don't run lipos I have done a lot of wiring (former VW bug owner) is to check the rating on the wire. Could be your dumping too much juice into an inferior wire and it just cant take it.

 

 

But, I think if the motor isnt turning or at least kicking but not rotating I would check the polarity again.

I am no expert but your C rating is ridiculous your runnin a battery for a r/c car, I wouldnt go over 25 myself, do you have the proper size wiring? with that C rating I would think you should be using cable not wire

 

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I am no expert but your C rating is ridiculous your runnin a battery for a r/c car, I wouldnt go over 25 myself, do you have the proper size wiring? with that C rating I would think you should be using cable not wire
First off, C rating is meaningless on its own, it is one variable in a formula to obtain the battery's max amperage supply, nothing more. I'm not sure who decided to sell batteries on the basis of C rating, but it has caused a lot of needless confusion.

 

Secondly, said amperage supply does not matter after a certain point. You motor will never use more than a certain amount of amperage. If that happens to be a 20 amp draw with peak amperage of 35, and the battery can supply at least that amount, that is exactly what the battery will supply, It doesn't matter if the battery is capable of supplying a 100 amp draw, or even more.

 

The only time when this makes a difference is when the battery is not capable of fully supplying the motor's "request", and the worst that can happen in that case is that motor performance is cut down to the point that the system will not draw your spring back.

Edited by Daishain

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Esp. when trying to diagnose, use a fuse. It's much easier to replace a fuse than a whole wiring harness.

 

Daishain, you're right about C rating except for this last statement.

"The only time when this makes a difference is when the battery is not capable of fully supplying the motor's "request", and the worst that can happen..."

Actually the worst that can happen is the battery can fail. The C rating is the maximum 'safe' discharge. The battery can very well cross that limit (most LiPos can easily supply 100A or more of shorted), it just goes from 'safe' to 'unsafe' in doing so.

 

A few general notes --

When working with a MOSFET, esp. if it does not have ESD protection around the GATE, always take care to control ESD (properly ground yourself before beginning work, use a soldering iron that is grounded, etc.)

 

A lot of the MOSFET designs are poor, if the trigger is stuck or held down, or if the motor is spinning and you remove the battery, it can kill the MOSFET.

 

You need to diagnose our wiring system from an electronic standpoint, measure the resistance when the trigger is not pressed and make sure it is infinity, push the trigger and the resistance should drop to less than an ohm or two. If neither of these things is true, something is wrong; either condition can cause a failure.

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Okay guys. just bought a whole new wiring harness (lonex) with trigger contacts. Re shimmed the gearbox and all is working well again!

Its a bit whiny but I can live with that for a while!

 

Cheers for all the suggestions and help. Was quite a mystery.

I am however running it without a MOSFET at the moment as I don't want to waste money on ruining another.

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