Gearbox whine

RandyAB · November 21st, 2010, 18:23

I have and SRC M4A1 and had to replace the piston after stripping the factory one. While I was at it I re-shimmed the gearbox after viewing some how-to videos on the internet. The gun now has a tendency to blow fuses after a bit of sustained firing. I must say as well that there is a bit of a whine to the gearbox. Is this because I shimmed it a bit too tight. I did check that the gears spun freely with fairly minimal resistance, however I didn't have the screws in at the time. I'm thinking that the screws may have tightened things up a bit too much. Is the whining generally a sign of the gears being shimmed too tightly?
Thanks
Randy

DoctorBadVibez · November 21st, 2010, 18:42

Not always, check your motor height in the pistol grip, its its too tight (to far up into the gearbox) it WILL whine....
Cheers

RandyAB · November 21st, 2010, 19:37

Thanks for the reply.

The set screw for motor height is backed off all the way.

Randy

coach · November 21st, 2010, 19:58

Pull the spring and piston and screw the mechbox together and test your shimming again.

Now that your motor screw is back out, screw it back in in 1/4 turn increments and listening to the sound change. Take note that if the screw is really easy to turn, the motor might be hung up. There should be some resistance when turning in either direction.

RandyAB · November 21st, 2010, 20:41

Thanks coachster I'll do that.

THe_Silencer · November 21st, 2010, 21:27

You can also try a 30amp fuse to minimize blowing.

coach · November 21st, 2010, 22:25

Quote:

Originally Posted by THe_Silencer

You can also try a 30amp fuse to minimize blowing.

I highly disagree with this!

I'd figure out what's causing the fuse to blow first before increasing the amperage of a fuse.

HKGhost · November 22nd, 2010, 00:04

if done correctly, you shouldn't need a fuse at all.

coach · November 22nd, 2010, 08:46

Quote:

Originally Posted by HKGhost

if done correctly, you shouldn't need a fuse at all.

Absolutely. None but one of my aeg's have fuses but they wouldn't blow a fuse if one was installed. The one that has a fuse only has one, because it came with the ASCU and I'd like to protect the electronics.

Styrak · November 22nd, 2010, 16:05

ALWAYS check shimming with the mechbox screwed down. It's pointless without doing that.

audi_bhoy · November 22nd, 2010, 17:15

Quote:

Originally Posted by Styrak

ALWAYS check shimming with the mechbox screwed down. It's pointless without doing that.

I agree with that! screws tighten the gearbox, and by the same occasion the gears. I personnally shim each gear separately, but I start by shimming the middle one, then I choose shims for the 2 others, to make sure they have minimal clearance between each, then I shim each one seperately, tightening the gearbox each shim set I try.

GODSPEED|seven · November 26th, 2010, 03:26

Quote:

Originally Posted by coachster

Absolutely. None but one of my aeg's have fuses but they wouldn't blow a fuse if one was installed. The one that has a fuse only has one, because it came with the ASCU and I'd like to protect the electronics.

I have an Old Tokyo Marui MP5 I've recently acquired... I've noticed it has a fuse.. do I really need it? it doesn't have any special electronics. Maybe to protect a hi-speed motor? (EG560, yes it has the Famas motor.. hehe)

coach · November 26th, 2010, 08:05

Quote:

Originally Posted by GODSPEED|seven

I have an Old Tokyo Marui MP5 I've recently acquired... I've noticed it has a fuse.. do I really need it? it doesn't have any special electronics. Maybe to protect a hi-speed motor? (EG560, yes it has the Famas motor.. hehe)

Caveat Lector:
Since it's not my gun not have I opened it to take a look at it, I can't recommend keeping the fuse or not. It's a decision you have to make. Regardless if you have electronics/MOSFET or not, realize a fuse is there for a purpose. It's there to blow in the event of a short or other possibly catastrophic situation. People blow fuses all the time but there is always an underlying cause.

A short 'could' potentially damage your battery, motor or switch assembly. In turn could also lead to striped gears or other broken parts.

Coach

ArcticFox1984 · November 26th, 2010, 08:22

I would also check to ensure that your pinion gear is engaging your bevel gear properly.

If its to high or to low the system will whine.

It's not uncommon to see no shims on the "top" of the bevel gear, if not no bevel shims entirely ( the pinion keeps things in place for the most part anyway. )... alternately, I've seen people remove material from the shim on top of the bevel gear to allow for further engagement with the bevel gear as stock tolerances are not always enough.

This is something that people often overlook and in my experience is the cause of most box whine.

Shell Shock · November 26th, 2010, 12:18

Quote:

Originally Posted by ArcticFox1984

I've seen people remove material from the shim on top of the bevel gear to allow for further engagement with the bevel gear as stock tolerances are not always enough.

done this quite abit for the low end pot metal gears and gearboxes. but then again, ive had to do alot to some pot metal gearboxes just to get them to fire (its amazing what you can do with a dremel)

though to OP: might be your motor is under powered? might be trying to draw to much power (there go blowing the fuses) and is struggling under the weight of the spring. i know for a fact, that as motors age, there performance goes down considerably. the brushes wear out and the reliability and performance go down as well

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November 21st, 2010, 18:23	#1
RandyAB Trader rating Join Date: Nov 2009	Gearbox whine I have and SRC M4A1 and had to replace the piston after stripping the factory one. While I was at it I re-shimmed the gearbox after viewing some how-to videos on the internet. The gun now has a tendency to blow fuses after a bit of sustained firing. I must say as well that there is a bit of a whine to the gearbox. Is this because I shimmed it a bit too tight. I did check that the gears spun freely with fairly minimal resistance, however I didn't have the screws in at the time. I'm thinking that the screws may have tightened things up a bit too much. Is the whining generally a sign of the gears being shimmed too tightly? Thanks Randy

November 21st, 2010, 18:42	#2
DoctorBadVibez Trader rating Join Date: Jul 2010 Location: Scarborough, Unionville, Stouffville and on a Benetti	Not always, check your motor height in the pistol grip, its its too tight (to far up into the gearbox) it WILL whine.... Cheers __________________ "This is my rifle. There are many like it, but this one is mine..." - Maj. Gen. W.H. Rupertus, USMC

November 21st, 2010, 21:27	#6
THe_Silencer Trader rating Join Date: Jul 2009 Location: Hamilton,ON	You can also try a 30amp fuse to minimize blowing. __________________ It is the mark of an educated mind to be able to entertain a thought without accepting it - Aristotle -Founder of Steel City Hamilton Infantry and Tactics -Certified level 43 Autosniper by Commander Amos

November 21st, 2010, 19:37	#3
RandyAB Trader rating Join Date: Nov 2009	Thanks for the reply. The set screw for motor height is backed off all the way. Randy

November 21st, 2010, 19:58	#4
coach aka coachster Trader rating Join Date: Mar 2008 Location: T dot	Pull the spring and piston and screw the mechbox together and test your shimming again. Now that your motor screw is back out, screw it back in in 1/4 turn increments and listening to the sound change. Take note that if the screw is really easy to turn, the motor might be hung up. There should be some resistance when turning in either direction.

November 21st, 2010, 20:41	#5
RandyAB Trader rating Join Date: Nov 2009	Thanks coachster I'll do that.

November 22nd, 2010, 00:04	#8
HKGhost Trader rating Join Date: Nov 2009 Location: Mississauga, ON	if done correctly, you shouldn't need a fuse at all. __________________ Please email me as I'm not on ASC too often. Custom Build \| Upgrades \| Repairs \| Maintenance Contact: ghostgunwork@gmail.com / Private Message

November 22nd, 2010, 16:05	#10
Styrak Trader rating Join Date: Jan 2007 Location: Saskatoon, SK	ALWAYS check shimming with the mechbox screwed down. It's pointless without doing that. __________________ Airsoft Sales and Repair/Upgrade Services

November 26th, 2010, 08:22	#14
ArcticFox1984 Trader rating Join Date: Feb 2007 Location: Toronto, Ontario	I would also check to ensure that your pinion gear is engaging your bevel gear properly. If its to high or to low the system will whine. It's not uncommon to see no shims on the "top" of the bevel gear, if not no bevel shims entirely ( the pinion keeps things in place for the most part anyway. )... alternately, I've seen people remove material from the shim on top of the bevel gear to allow for further engagement with the bevel gear as stock tolerances are not always enough. This is something that people often overlook and in my experience is the cause of most box whine.

Gearbox whine

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