cyma m14 electrical issue ??

[dalem94]

just bought a cyma m14, complete gutted it internally on the gearbox and replaced motor and fitted gate mosfet, running a 11.1v Lipo 25c it shoots 3 or shots then completely does nothing. it is an electrical short within the motor..

internally:

metal bushings 

shs unrated gears

ball bearing spring guide (metal)

m140 spring

shs metal teeth piston

can't remember the cylinder head I bought

motor is a lonex a2 high torque motor

shs air nozzle and tappet plate

gun shot fine for like 200 shots then sounded like battery was dying rapidly then just completely stopped, tried a new fully charged battery then shot 3 shots then stopped again. if I leave it for about 30 mins I can get 1 shot then stops. 

took it apart and motor is cover in black like soot, is the motor shorting or is it a wiring issue (it has 16 gauge wire at the moment) how can I get it working ? 

 

[Samurai]

I would say that since it's a complete custom gun, no-one can tell until further experiments.

Is it an AB FET? That stops the motor by giving it a quick pulse of reversed polarity and that usually arches big time, burning the commutators. But not in 200 shots.

Or maybe the gearbox is too tight and with heat, it locks up, hence the wait for the cooldown.

 

[dalem94]

I will experiment later, and no it's just a normal mosfet it isn't an AB FET it is just a simple gate one.

I am thinking that due to the heat my gearbox needs another look at and maybe re-shimming or something else. 

I'll update when I have time to look. 

thanks 

 

[Iceni]

Does it have a fuse?

Might be that the fuse is rated right at the amp draw of the system. Not enough to blow it, but enough to heat it to the point of been very high resistance. If you have a fuse bridge the connections and try again.

I has a similar issue when I moved onto 30c 7.4 lipo's. I ended up taking the fuse out all together. If you opened the holder and shot the fuse would glow like crazy and get stupid hot, And the gun would slow down with the head build up.

 

[dalem94]

It doesn't have a fuse.

I have managed to solve it, the motor case is metal on a v7 gearbox and I had both the + & - touching the metal completely slipped my mind and it was just arching out over the body of the gearbox. Just covered both contact points in the motor with insulation tape 

 

[dalem94]

I managed to solve the electrical issue but now I am having problem in that I am building up too much carbon within the motor and its temperature cut off kicks in and doesn't work for 30 mins etc... it building up to much carbon from what I think is because I am running an 11.1v 3cell 25c 2200mah which is going straight to the motor from the mosfet.

if I were to run a 7.4v 2cell would I be right in thinking there would be less arching within the motor because the volts aren't as high and wouldn't build up carbon as much ? 

 

[Samurai]

There seem to be some problem with the motor. A normal motor should be able to handle 11.1V, even more, with the max 55A the battery can supply. The mosfet removes high amps from the trigger contacts, so it doesn't make a real difference with the motor, unless it's an AB fet, which does arc a lot on the motor.

 

[Hangtight]

The lonex motors have notoriously soft brushes which wear very quickly, hence the carbon buildup up on the motor. From memory the A2 is a 16 or 17TPA motor, so on standard gears and 11.1v that's going to be drawing a lot of current pulling a 130 spring, especially if the shimming is a bit tight because it'll be trying to do around 27rps.

You'd be a lot better off with a 22TPA motor, like a ZCI High Torque. The current draw will be lower, less heat, less stress on the gearbox and battery, plus it's arguably a better motor than the Lonex.

 

[dalem94]

Thank you I will look at getting a different motor then and then feedback. Would running a 7.4v battery benefit as well as the 22TPA motor ?  as I'm only running a dmr platform so not needing ROF 

 

[Hangtight]

On the 11.1 it'll still have a nice snappy trigger response and a short cycle time. With 7.4v then 13:1 gears with the 22TPA is nice. About the same cycle time and current draw with the benefit of a quieter gear train. Either of these combinations would be very nice with a Mosfet that supports pre cocking, but I'm not sure if anything is available to fit the M14.

 

[dalem94]

Okay lovely, I've had to switch back to the standard gears as I can't seem to find any v7 gear sets, I have tried a v3 and v2 but they keep stripping my piston as the pinion gear teeth are too thin. anyone know of any gear sets that have worked in a cyma m14 ? 

 

[Sitting Duck]

Okay lovely, I've had to switch back to the standard gears as I can't seem to find any v7 gear sets, I have tried a v3 and v2 but they keep stripping my piston as the pinion gear teeth are too thin. anyone know of any gear sets that have worked in a cyma m14 ? 

Click to shrink...

Little bit puzzled but how does the pinion gear (motor's gear) strip a piston ???

AFAIK M14 uses the v6/7 gear set as the spur & perhaps but don't quote me bevel gear is different to a v2/3 gear set

Think I remember reading that the L85 uses the same type of gear set but L85 is a 19 tooth sector

The sector should be a std 18:1 or 16:1 sector as siegetek offer 2 basic std SSG sectors compatible with v2/3 as well as v6/7

(they call them the Revolution or Balanced gears or something - way out of my price range)

The std v6/7gear set is about 21:1 aprox (same as L85 ratio I think) and SHS make:

CL6010 - 10 tooth bevel gear set - most likely a 10 tooth bevel set you have

or

CL6010 - 9 tooth bevel gear set (that may alter ratio to about 23:1 ??? )

There is an expensive high speed Prometheus v7 set but only reason that is faster coz of the 12 tooth bevel

So that will cost money for a hen' tooth set imported no doubt - not worth it

Or Siegetek crazy mofo set:

http://www.brillarmory.com/index.php?main_page=product_info&cPath=36_55_69&products_id=694

So you are stuck with stock gears or SHS v6/7 set

though it is possible they could be inter-changeable perhaps the Cyma std & SHS set

The only gear you might be able use from a reg v2/3 is sector gear from a 18:1 set

TBH - sounds like your shimming of bevel to pinion gear was out and motor pinion jammed in

either forcing bevel tight against wall of box if bevel was over shimmed or too low

or pinion tip hitting the AR lugs on bevel

I'd take a stab and say bevel over shimmed/too low - so the motor wasn't wound in correctly

Which may have allowed the low sitting motor to short on cage & everything struggled to turn as bevel is smashed against bushing

And quite likely - almost certainly the amperage draw going through the roof

(been there my first few times)

You can suss out the gear set ratio by setting sector to say 12 o'clock

Mark bevel gear with a pencil (not borrowed from John Wick)

rotate the sector one full revolution, counting the amount of rotations on bevel gear

At a guess I'd say 7.5 turns perhaps ???

multiply the amount of turns by 3: 7.5 x 3 = 22.5 which should be the aprox ratio

(this works on v2/3 gear sets so don't see why it wouldn't work on v6/7 sets but not tried it myself)

Do this to both sets if you like - they should be the same I would have thought

You might be able to mix/match the Cyma & SHS sets if they are similar - should work

See which stuff spins best - I have mixed/matched gears

Though we normally say DON'T MIX GEARS - you can if you are careful and same ratio sets etc...

I have swapped stuff about when a CAREFUL mixture seems to run smoother than a complete set

However - this mixing of gears is not your real problem - though some gears runs better than others in some boxes

The REAL issue is very very likely bad shimming - mainly on the bevel gear height & its motor height

Get that bit wrong and don't matter if you got top banana siegetek gears - it will run $hit

EDIT - small minor update & stuff to check...

shs metal teeth piston

Click to shrink...

^THIS^

SHS Pistons "can" bind and really slow the piston's movement, low rof, even fps

So check for any piston, especially a SHS one for binding in the gearbox rails etc....

Never assume this crap will just work as is....