Gearbox lock-up, motor issue

[SCAR_Jester]

Hi all,

Last night I changed my G&P's stock m120 speed motor out for an SHS high torque, apart from the pinion gear having "slightly" different angle on the teeth, both motors were about the same.

Shot a couples times and it locked up altogether.

Took out the SHS motor and the pinion gear screw was lose and the gear almost fell off, to my knowledge I did not pull it against the gearbox wheel to loosen it.

Putting in the old motor allowed me to "unlock" the gun.

Can anyone advise possible faults and fixes?

A thought I had was to A: replace the pinion with a new one.

B: swap motor arms and pinion gears.

thanks for any advice, other than the pinion gear lodging itself in a gear this one has me stumped!

- Corky

 

[Hangtight]

Don't just shove a new motor in a gun. That's a really good way the ruin the gears. You can get away with it if you're really lucky, but you should really start from scratch with motor height and then reshimming the gears to suit if neccesary. A motor only needs to be fractionally longer from base to tip of the pinion to bind the gears together if you just swap them over.

 

[SCAR_Jester]

Don't just shove a new motor in a gun. That's a really good way the ruin the gears. You can get away with it if you're really lucky, but you should really start from scratch with motor height and then reshimming the gears to suit if neccesary. A motor only needs to be fractionally longer from base to tip of the pinion to bind the gears together if you just swap them over.

Understandably yes, I will try that soon however, that could cause grinding noise at best being out of place, it would not explain a total gearbox lockup and the battery nearly exploding.

Thank you though 

 

[Hangtight]

It doesn't take much to push the pinion and the bevel together hard enough to lock the gearbox. If the motor was stalled due to this that would overload the battery.

 

[SCAR_Jester]

It doesn't take much to push the pinion and the bevel together hard enough to lock the gearbox. If the motor was stalled due to this that would overload the battery.

I don't mean to be rude but could you be more specific?

For instance, is it possibly that it was just too tight?

See it fired a fair few shots on semi and full auto before locking, that would be my only argument that I believe it has something to do with the pinion gear simply not fitting right with the spur gear

 

[Sitting Duck]

What Hangtight is saying

the motor's height is too high

OR

the bevel's current shimming is too low for SHS bevel

The motor's gear or pinion is now shoving the poor bevel against the side of the box/bushing

causing great resistance/heat/amp draw - this getting sluggish & warm on wiring & fuse blowing etc...

Most motors are about 88mm in length top to bottom give or take 0.5mm

HOWEVER - different pinions and bevels mesh better/worse

some pinions on some crap or not so good motors are fatter at the base that they are tight to enter the motor entry in box

They are more flared at the base or the angle the teeth are cut can alter the meshing & the shimming

Now - I presume the pinion is affixed correctly and perhaps some mild loctite to keep the grub screw from undoing

Perhaps wind back the motor height screw 1 full turn counter-clockwise - NOTE THIS ADJUSTMENT !!!

(if it all goes tits up you need to put it back)

normally I would say 1/2 turn but if you got lockup then it must be ramming the poor bevel right into the box

put some grease on the pinion gear - not loads but a light smear to help the teeth to mesh a tiny bit smoothly

place gun on semi & flick the trigger - don't need to try to complete the cycle

if she sounds like a swarm of wasps then it is too low and you might need to go 1/4 to 1/2 turn clockwise

if she sounded ok-ish then fire some shots

Now this is still very much guesswork at best & though you have dropped the motor height

nobody will know just how much/well the pinion is meshing with bevel gear now

realistically you want max teeth engagement with both gears set correctly to each other

What Hangtight is referring to is the bevel might need a reduction in the shimming on top of bevel

So that the two gears mesh as best as possible

But we mush be careful in adjusting for different tolerances we don't end up like this:

The first example has little teeth engagement

in this case the motor set to correct height would force the bevel up into the box

what really needs to happen is the bevel needs to sit higher by reducing the shims on top of it

(and then the motor pinion can move inwards a little to mesh fully or more fully)

BUT nobody knows just how the two are actually meshing without ripping her open to check....

Now yes you can try to lower the motor height a little - 1 turn say

but this is still guesswork which is far from ideal especially if you have modest experience & untrained ear

Even then I still say listening to the sound is a poor second to having a bloody good idea the bevel height is correctly set

Even then I use a power meter now to check the amps and fine tune

Realistically once the height is checked you should only need to tweak the height say 1/4 turn to find the perfect spot

listening & checking amps etc....

If I have to go more than 1/2 a turn then something is out and my setting of bevel height was out to begin with

It sounds like your bevel is being forced into the box way too much most likely

I would consider dropping it at least 1/2 turn probably 1 full turn as she is binding in the box

NO MORE

See how she runs with a quick flick - very quick flick of trigger

(you don't wanna munch up gears this early stage)

if ok turn a 1/4 either way to see how she runs

Yes you could swap the pinions if push comes to shove - BUT you would still be guessing the motor height

But yes you could try that if no joy

However you can't afford to munch the gears up too much

So in some respects see if you can get the SHS to run ok by dropping the height 1 turn

this should be about 1mm maybe depending on the adjustment screw thread pitch

normally too much but you could be smashing the bevel into box so yeah I'd go to say 1 full turn counter-clockwise

If no joy, then perhaps reset the height back to its original position and go with old motor for now

then at some point you or a tech can reshim the box perhaps with new faster gears next service with shs motor

SHS are normally quite good - bad meshing motors/pinions are Dream Army & some Big Dragon motors on some bevels

hope some of this helps but try not to munch your bevel/pinion up guessing the motor height

(been there - seen it - done it - got T shirt etc....)

Spend too long messing about stabbing in the dark guessing the meshing....

By the time you nearly got it right - the gears are muller'd and need replacing - so a quick go but give up if no joy)

Hope some of this helps - but don't munch ya gears if you can help it

 

[SCAR_Jester]

What Hangtight is saying

the motor's height is too high

OR

the bevel's current shimming is too low for SHS bevel

The motor's gear or pinion is now shoving the poor bevel against the side of the box/bushing

causing great resistance/heat/amp draw - this getting sluggish & warm on wiring & fuse blowing etc...

Most motors are about 88mm in length top to bottom give or take 0.5mm

HOWEVER - different pinions and bevels mesh better/worse

some pinions on some crap or not so good motors are fatter at the base that they are tight to enter the motor entry in box

They are more flared at the base or the angle the teeth are cut can alter the meshing & the shimming

Now - I presume the pinion is affixed correctly and perhaps some mild loctite to keep the grub screw from undoing

Perhaps wind back the motor height screw 1 full turn counter-clockwise - NOTE THIS ADJUSTMENT !!!

(if it all goes tits up you need to put it back)

normally I would say 1/2 turn but if you got lockup then it must be ramming the poor bevel right into the box

put some grease on the pinion gear - not loads but a light smear to help the teeth to mesh a tiny bit smoothly

place gun on semi & flick the trigger - don't need to try to complete the cycle

if she sounds like a swarm of wasps then it is too low and you might need to go 1/4 to 1/2 turn clockwise

if she sounded ok-ish then fire some shots

Now this is still very much guesswork at best & though you have dropped the motor height

nobody will know just how much/well the pinion is meshing with bevel gear now

realistically you want max teeth engagement with both gears set correctly to each other

What Hangtight is referring to is the bevel might need a reduction in the shimming on top of bevel

So that the two gears mesh as best as possible

But we mush be careful in adjusting for different tolerances we don't end up like this:

The first example has little teeth engagement

in this case the motor set to correct height would force the bevel up into the box

what really needs to happen is the bevel needs to sit higher by reducing the shims on top of it

(and then the motor pinion can move inwards a little to mesh fully or more fully)

BUT nobody knows just how the two are actually meshing without ripping her open to check....

Now yes you can try to lower the motor height a little - 1 turn say

but this is still guesswork which is far from ideal especially if you have modest experience & untrained ear

Even then I still say listening to the sound is a poor second to having a bloody good idea the bevel height is correctly set

Even then I use a power meter now to check the amps and fine tune

Realistically once the height is checked you should only need to tweak the height say 1/4 turn to find the perfect spot

listening & checking amps etc....

If I have to go more than 1/2 a turn then something is out and my setting of bevel height was out to begin with

It sounds like your bevel is being forced into the box way too much most likely

I would consider dropping it at least 1/2 turn probably 1 full turn as she is binding in the box

NO MORE

See how she runs with a quick flick - very quick flick of trigger

(you don't wanna munch up gears this early stage)

if ok turn a 1/4 either way to see how she runs

Yes you could swap the pinions if push comes to shove - BUT you would still be guessing the motor height

But yes you could try that if no joy

However you can't afford to munch the gears up too much

So in some respects see if you can get the SHS to run ok by dropping the height 1 turn

this should be about 1mm maybe depending on the adjustment screw thread pitch

normally too much but you could be smashing the bevel into box so yeah I'd go to say 1 full turn counter-clockwise

If no joy, then perhaps reset the height back to its original position and go with old motor for now

then at some point you or a tech can reshim the box perhaps with new faster gears next service with shs motor

SHS are normally quite good - bad meshing motors/pinions are Dream Army & some Big Dragon motors on some bevels

hope some of this helps but try not to munch your bevel/pinion up guessing the motor height

(been there - seen it - done it - got T shirt etc....)

Spend too long messing about stabbing in the dark guessing the meshing....

By the time you nearly got it right - the gears are muller'd and need replacing - so a quick go but give up if no joy)

Hope some of this helps - but don't munch ya gears if you can help it

First off, fantastic description of full work through.

And secondly thank you, I have a game coming up soon so I'm just going to leave it till after first, and I might just go ahead and throw in some SHS 13:1 gears if I have it open anyway..

On a side note, any idea why the trigger reset feels so strong? And occasionally pulling it on semi it gets caught and needs to be really forced to fire, an auto burst fixed this..

Thanks again!

 

[Sitting Duck]

On a side note, any idea why the trigger reset feels so strong? And occasionally pulling it on semi it gets caught and needs to be really forced to fire, an auto burst fixed this..

Thanks again!

DON'T FORCE IT FFS !!!!

What that is most likely is the dead zone when firing on semi coming from Auto

The Cut Off Lever has not fully dropped down and it catching or hitting the lug on the trolley

On Auto the COL is raised upwards and no issue

ON Semi - the COL slips under and pops the whole trolley off the trigger's sear

Now when you feel resistance it is most likely the COL hasn't quite dropped under the lug

and/or over time being forced it has got a bit worn/damaged so it isn't so clean or sharp

or for some reason the COL spring is weak or COL itself is not dropping quite enough

That is the basics:

COL UP for Auto so it slips over the lug

COL DOWN for Semi so it slips under lug to pop trolley off sear/trigger itself

Usually new players force it in this dead zone - the COL is still partially raised

when you need to cycle a smidge to get COL to drop or no longer be partially raised

Forcing it will damage the trolley's lug and not wise

if it is still iffy when firing on semi shot after single shot after shot

then it will need close attention possible replacement of some or all parts:

Cut Off Lever - though usually this is if it doesn't pop high enough to disengage trolley

Trolley (might be ok to leave switch as is but they come as a set)

selector plate - but doubt it unless original has been replaced with an aftermarket one and needs slight mod

But yeah forcing stuff is not wise and will only make stuff worse in the end

Small update coz couldn't be ar$ed to locate it yesterday..

A good video showing just how the semi/auto trigger functions

the semi & COL popping the trolley off the trigger sear etc....

at about 0:30 you see what does what

tbh if the lug is a bit damaged at the tip you "might" be able to clean it up a little

or slightly sharpen it at the very tip if it has a burr on it from being forced @ dead zone

Yes order a new switch and perhaps use the new trolley if switch contacts are ok

BUT sometimes certain trolleys/switches work great/crap with certain triggers

(usual high quality TM compatible part is not always 101% compatible with all stuff)

By that I mean sometimes the trolley can jump off the trigger at full pull

(in cases like this it is worth considering a reduced trigger pull mod perhaps

though only if ya bored, know what you are doing as you have little to lose anyway)

In your case - inspect the existing trolley - you have to remove it to replace it anyway

maybe clean it up at the very tip ofthe "lug" & retry it if it looks ok

SHS triggers are nice and probably will work ok too

just if you replace some bits n bobs you can find instances the new part is not fully compatible

(welcome to the world of toy guns)

Anyway - video shows how the semi/auto trigger works in operation  

 

[Hangtight]

What SD said, but I didn't have time to type this morning. The amount the gears mesh and how closely they mesh is critical. You need to have the gears fully engaged or they will tear each other apart under any significant load. But if the motor height is too high or the bevel gear is shimmed to low then fitting them together will cause the bevel gear to try and 'twist' as it gets wedged over by the pinion causing a massive load on the bushes /bearings. Or the pinion will be too low and only partially engaged with the bevel. And in the first case it will turn over until the lubrication fails and the fiction rises, but by this point damage may well have been done. In the second case it'll tear teeth off the pinion.

This is why when you do a motor change you start by checking the motor is raised enough to fully engage with the bevel, and then shim the bevel gear to get the correct operating clearance.