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slipperysquid

Nightmare gearbox/mosfet setup HELP!

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I'm having a bit of a time with new mosfet setup :( It's driving me crazy and I'm out of ideas, so was wondering if there's any techies on here that could maybe give me some pointers?

 

Right so I've installed a jefftron programmable mosfett, I've used the V2 microswitch version on another build with no problems so to speak but this one has got me confuddled.

 

So I've installed a new SHS high torque motor, new piston, gears and cylinder head.

 

At first I corrected the aoe on in the gearbox using reinforced sorbo pad, filed teeth down etc on piston, put everything back together test shot and it did the following.

 

Piston moved back on first shot and then second shot fires twice. Auto seems to fire ok.

 

Fiddled about with it for ages,including trying a sector delay chip (I'm running on 7.4v lipo by the way but thought it was worth a shot)  installed original gears, still does the same, first shot piston moves back second shot fires twice, it does this consistently.

 

Spoke to the guy from jefftron, that advised it could have been a few different things and recommended a new cut off lever or trigger contacts. So...got a new cut off lever, trigger, piston and cylinder head (incase my AOE correction had fluffed it up) installed and same thing happens.

 

Now I just seem to be throwing cash at a problem...I've yet to rewire everything back to stock which is what I'll do at some point today and check again. I'm thinking the new motor may be overspinning the gears etc, but that's what the mosfet is for (active breaking)

 

Any help or ideas would be great!

 

Cheers.

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List gears & battery/juice

how fast is it going - 25rps on a m100 you will get double firing or serious overspin

is the mosfet an AB one or just regular mosfet

 

either too much juice or knackered Cut Off Lever popping switch trolley late

tight trigger contacts can pinch or grab the switch trolley causing it to pop late too

 

stuff like worn COL or tight contacts is my first guess unless you are pushing 11.1v @ about 25-30rps

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Have you got the pre cocking turned on?

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Thanks for the replies,

 

Using SHS 13:1 gears on a 7.4v 1300mah 

SHS high torque

Jefftron programable mosfet with AB on (doesn't matter what I set the AB strength to, it doesn't change) pre cocking is off.

Have put in new trigger contacts and new cut off lever.

I tried a weaker motor which help but it did what I wrote below.

The weird thing is as I shoot in semi I've noticed that the piston gradually comes further and further back, so fire one shot, end of piston can be seen just entering the cut out window second shot, a bit more visible etc it does this until the piston is fully back then goes forward and cycles twice. (pre engagement????).

 

I'm going to start all over again from the shimming onward and see where it gets me.

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That gear and motor set up will run at over the recommended maximum ROF for the module. I'm wondering if there is a timed minimum trigger period before the AB kicks in. It would be a quick and dirty fix to try and ensure a full cycle. But if the actual gearbox cycle time was slightly shorter than the minimum trigger time of the Mosfet you'd get that gradual pre cocking.

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Right I'll have a word with mister Jeffetron and see what he says, I use the  V2 micro switch version on another gun that according to the site is rated to 25bps and that works fine with a 12:1 gear set.

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Thinking on how would the rps effect semi?

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My thinking was that if the Mosfet is only switched by the trigger contacts being closed, then there can be a problem if the trigger contacts only touch for an instant rather than properly latching and being released by the cut off lever. In that instance instead of the timing being properly controlled by the trigger shuttle latching and then being released at the right moment by the cutoff lever, you just get a little jolt that is enough to move the gears to a position where the trigger jams, at which point you have to give it a quick squirt in full auto to reset things.

This also happens with microswitch 'bounce' and the quick and dirty way to avoid it is to switch the Mosfet for a certain amount of time as soon as any contact is detected, which is what may be happening here, as the same processing unit appears to be used with their microswitch trigger module.

If this amount of time is more than the single shot cycle time it'll over spin a fraction every time you pull the trigger, gradually winding it up to the point where it's fully pre cocked. Then you'll get a double shot before starting the cycle all over again.

The fix might be to make sure the trigger shuttle is fully engaging with the contacts so the timing is controlled mechanically. A common cause of semi auto lockup is the end of the safety not allowing the trigger to push the shuttle fully forward causing it to release early instead of when it's kicked free by the cutoff lever.

Too many words.... :P

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Excellent reply sir! Really appreciate you taking the time out to write that mate!

I'm thinking of throwing this mosfet into an a standard MP5 and putting the Jefftron v2 into my 416 and then throwing a load of cash away and getting the gate titan for my main gun...I've spent to much time stripping down and faffing about with this mosfet to worry about it anymore :( 

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Before you do, try filing a bit off the end of the safety bar. With the gearbox out of the receiver, put the selector in the correct position for semi auto and pull the trigger fully with your finger on the little lug that the selector bar pushes to engage the safety. If you can feel that moving at all then its in the way of the trigger.

I must have taken my DSG apart about three bloody times before I figured out that was the reason it was jamming in semi auto. Also make sure the trigger contacts are fairly close together so the shuttle engages them nice and early.

 

Bloody toy guns.... ;)

 

PS, don't get the Titan, because you'll hate it so much you'll want it in all your guns. You especially won't like the tunable trigger pull or the fact you can turn the pre cocking on and off in two seconds with the selector and trigger rather than twatting about trying to remember how many trigger presses it was while attempting to reconnect a battery with one hand.

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Having done a bit more reading, it appears that the unit needs to relearn the trigger timing every time its powered up, hence the requirement to make three semi shots after connecting the battery. What's not clear is whether it is capable of adjusting the applied timing on the fly. So if your cutoff lever set up is slightly off, and it 'learns' the wrong timing initially its possible it keeps applying it, causing the issue you're having. The microswitch version won't have the problem as it's reading the gear timing straight off the cutoff lever cam, albeit via the cutoff lever.

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Problem solved..

 

IMG_0106.JPG

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