Riptide's "How To Make a Gearbox Lipo-Ready" Guide *Update 6/4/10*

[aznriptide859]

This guide started off originally as an inquiry on ASM regarding the qualifications of such mods, but of course, with some testing I've so far deemed it good enough to suggest to other players.

I usually don't like it when retailers claim a gun is "lipo ready", because to me mass produced guns can't have the precision that allow them to be ready for lipos. But over time when I've worked on GB's, I've noticed certain upgrades can go a long way that help your gun last longer. I'm testing this method to see if a stock GB, if done with these upgrades, can handle a 11.1v lipo with at least a 25A discharge rate over an extended usage of time (note: hunterseeker5 on ASM has suggested that a gun is "lipo ready" on a 11.1v lipo on an UNLIMITED amperage discharge; unfortunately I do not have larger, higher powered lipo's to do this with, nor do my guns have the space).

Disclaimer - these are simply steps I go through to make sure my guns are lipo ready. I am not responsible for any issues you come up with during GB breakdown/incorrect modification - I am assuming the reader/modifier is well read in GB maintenance/know's his way around a GB very well.

Before beginning, I will suggest reading Infected's thread regarding LiPO batteries - it gives a very good explanation about how they work and whatnot. There are 4 parts in total.

http://infectedairsoft.wordpress.com/tech-info/lithium-polymer-batteries-part-1/

This is NOT a thread regarding general LiPo info or questions - if you want to read more about that, see here: http://www.airsoftretreat.com/forums/index.php?topic=89308.0

Here are the steps I go through to make sure such a gun is ready for lipo's:

1.Thorough cleaning/regreasing of gearbox
This should be a no brainer - cleaning a stock GB for any tech should be the first thing to do. I personally don't trust any of the grease manufacturers use, especially ACM companies, so I just go ahead and clean it all out. Wiping them should be the 1st step, then for deeper cleans, use carb choke cleaner/spray (found at any auto parts store). Once sprayed on parts it will immediately help remove oil residue off the parts/GB.

Regarding regrease, I generally use generic white lithium grease (found at any hardware store) for all moving parts (piston, gears, tappet plate) and TM silicone grease for compression parts (piston O-ring). Of course, there are alternatives - if anyone has any suggestions, let's hear them.

For more specifics about cleaning, read here: http://pageproducer.arczip.com/daedalus03/mechbox.html (goes into specifics regarding greases too)

2. Reshimming Gears (on Metal Bushings)
To me, a metal bushing upgrade for longevity is a no brainer - it costs less than $10 to get and is simply one of those upgrades that "should" be had for any "lipo-ready" project. Of course, with a bushing replacement you'll need to do a reshim job. Any choice of shims should be fine - I have tons of G&P 0.1mm and 0.2mm shims simply because I can easily adjust between heights at 0.1mm increments. I've used Systema ones in the past, but they only come in 0.2/0.3/0.5 increments.

As for guides, here are the ones I use/reference to:

http://pageproducer.arczip.com/daedalus03/shim.html

http://www.858airsoft.com/upgrades/shim.html

http://www.airsoftretreat.com/reviews/showproduct.php?product=67&cat=49 (that's right, my first AEG shim job was based on ASR's guide )

After practice and time, you'll know what kinks to look for, but some of the more important things are to make sure the gears aren't contacting anything they shouldn't (i.e. each other level-wise, GB shell, etc).

3. 2nd to Last Tooth Removal

This term has been tossed around too, but I want to clarify it here today - this is taking the 2nd tooth from the spring hole end of the piston, NOT the piston head end of the piston. This has NOTHING to do with short stroking - please make that clear.

The purpose of this modification is to prevent premature engagement, where in a situation the gears rotate back faster than the piston has to return to its normal state. In this case the gear picks up the piston in a position where it's not supposed to (i.e. not the last tooth), so the piston will travel from there. This over time can damage the piston, eventually leading to piston stripping. By taking off the 2nd to last tooth, this helps ensure when the piston is returned/close to the returned state, the sector gear does not pick it up at any tooth but the last one.

Removing the tooth can be done either with dremel (easier) or an Exacto knife (harder). For higher ROF setups, most suggest to remove the 2nd to last and half of the 3rd to last as well. For even more extreme setups, removing both the 2nd and 3rd to last teeth are recommended.

More info (with picture) on ASM: http://forums.airsoftmechanics.com/index.php?topic=956.msg6627#msg6627

4. Angle of Engagement

Most techs have heard of this term more than once - it refers to the angle at which the 1st tooth of the sector gear engages the piston's last tooth. The reason this is important is that all pistons do not have the same length, nor are all gears built to the exact same spec. When the sector gear engages the piston at an incorrect angle, the tooth on the gear will put extra stress on just the tip of the tooth, which in the long run can lead to uneven piston teeth wear and eventually GB failure.

This is easily solved with either spacers (check my Hardware Guide for parts) or sorbo pads placed in front of the piston head. I like the former method as it gives a more precise incremental way to adjust for AoE.

Additional links:

http://forums.airsoftmechanics.com/index.php?topic=956.msg6626#msg6626

http://www.arniesairsoft.co.uk/forums/index.php?showtopic=152291

5. MOSFET

This should be a given to techs as well - for higher voltage battery powered guns, a MOSFET is almost needed to ensure the longevity of the gun's trigger contacts. Any basic MOSFET will do, as long as the product directs the voltage away from the contacts which will prevent trigger arcing. Ironically I use no MOSFET's in my guns, probably because I don't have the space for them XD.

Additional link: http://forums.airsoftmechanics.com/index.php?topic=2784.msg25030#msg25030

The following are optional upgrades. I simply put them in my guns (as do other seasoned techs) because I'm used to doing it, but they are not exactly necessary for a lipo-ready GB.

(Optional) X-rings for Improved Cylinder Compression

I've been using X-rings for the longest time in my AEG's simply because they provide better compression (at least over stock O-rings I've seen) which leads to higher FPS. However, some people on ASM have claimed that the X-ring's unbelievable seal with the cylinder can lead to problems in the long run. I still use them in my guns, but it is purely for an extra FPS factor - using these is optional. I still however suggest them to anyone who still run stock ACM pistons.

X-ring info can be found in the Hardware Guide on top of this subforum.

(Optional) Wiring Harness Replacement

As XM suggested, depending on the gun and how low quality the wiring is, the extra power/voltage flowing through the wiring may over time damage it. I've seen this personally happen on two Classic Army guns, where the trigger contacts actually melted...and this wasn't even on a lipo. If your gun shows up intermittent trigger issues, such as poor trigger response or even failure to shoot, replace the wiring harness - these don't go over $20-30 in most cases. In the past when I've bought them, I usually went Guarder or G&P. Systema is also good, but they're around the $45 price range.

(Optional) Deans Plug Replacement

A growing number of airsofters (and manufacturers, such as King Arms and G&P) have realized that the mini Tamiya and large Kyosho connectors found on most AEG's are not exactly of the highest quality. The design isn't the greatest (i.e. the pins inside the connectors can deform/wobble a lot) and don't provide the best connection. Deans Ultra plugs have been found to be a very good alternative - they are smaller, connect better, and provide a larger surface area of contact between the power source and the wiring to ensure even current flow.

Deans can be found at hobby stores across the nation, but usually they for $2-3 a pair, which is ridiculously expensive. I got a 10pack pair for around $10 on Hobbyking - not sure if they still offer those or not. If you need help regarding Deans wiring, simply go to my Hardware Article: http://www.airsoftretreat.com/reviews/showproduct.php?product=343&cat=49

The Power Source

Now, of course is the question - what lipo would you get for your gun? Of course, it depends on the gun, but keep in mind, since lipo cells are much more variable than NiMH/NiCD cells, you have a lot more options. This is a reason why many Armalite/AR15 users are going towards buffer tube lipo's, as they take up VERY little space and allow for a larger variety of RIS' and retractable stocks. Keep in mind though that your motor will draw whatever it needs, so usually having a higher amperage rating than needed is preferred. However, if space is an issue, most of the time around 25-30A should be enough for most airsoft applications.

As for shot longevity, the basic rule of thumb is you get 2 shots per mah. For lipo's this varies from battery to battery, at least in my experience - both my buffer tube lipos, rated 11.1v 1200mah 20C last about 2/3's a day, while my 11.1v 1600mah 18C last me a whole day of play. Just keep in mind the dimensions of your battery and your application. If it doesn't work, measure out your space first, or, if you have a Dremel, mod more space in the gun.

Some have asked regarding the use of 7.4v lipo's. They are not as powerful as 11.1v lipo's, and achieve about the same performance as a 9.6v NiMH battery depending on the discharge rate. Of course, since the stress put on the parts is a lot less than it would from a 11.1v, not as much modding is required. Metal bushings are still a must, as well as shimming, but AoE and piston adjustment's aren't always needed. It's still safer to do all the modifications, but again - depends on the situation.

The Proof

The immediate question is that, if these upgrades are done, can the gun really run on a higher powered lipo for longer periods of time?

I've done these mods to almost every gun I've received/owned/sold, but my latest gun (the COD MW2 M4) has been upgraded with nothing but the stated mods, and has lasted over 2k rounds on a 11.1v 1200mah 20C lipo with no issues whatsoever. Of course this is a pretty short run for any AEG, and only time will tell if the gun will last longer using the lipo. However, so far I feel that this list of upgrades, if done correctly, can make any gun ready for a high powered lipo.

And for a few more:

CYMA AKS74U - over 5k rounds on 11.1v 1200mah 20C lipo. Sold.
JG 2008 M4 - over 2k rounds on 11.1v 1200mah 20C lipo. Sold.
JG MP5SD6 - over 3k rounds on 11.1v 1200mah 20C lipo. Still going strong.

Comments/suggestions are welcome, plus if anyone has more field tests or even methods of making gearboxes lipo-ready, I'm open to them.

[Lord Merlin]

Comment/suggestion: this thread should get a sticky. That way at least some of the regular questions/threads could be eliminated...

Suggestion: You should also put in a small section about using 7.4V LiPo packs instead of the normal 8.4 or 9.6V packs, as making a gearbox safe for a 2S LiPo is way easier to do...

[MetallicaFatCat]

^ I agree on sticky and 7.4v lipo packs. The only thing, that I don't really like about 7.4v lipos is the extra risk from lipo batteries. Sure there smaller and have more amps (most cases) but you still need a special charger and an over-voltage protector, which you should add in there or else you, your gun and battery may go up in flames.

[aznriptide859]

Well to me, 7.4v/2s lipo's barely perform better than normal 9.6v batteries - almost nothing should be done for those in reality.

[MetallicaFatCat]

^ Exactly why I don't like them.

[coolbeans]

Good write up, I do every one of these mods not only when I use a Lipo, but for every gun I own.

Quick questions:

1. Does removing the second and third tooth make the piston less durable at all? I used to run a DSG setup in my gun so I removed both teeth on my supercore piston to avoid premature engagement at that speed (40+ rps). However, I am converting it into a DMR, so its back to a normal, full stroke system. Without those two teeth, can the piston still handle an M130 spring?

2. Do you think there are MOSFETs that are actually unsuitable for Lipos? I just feel that with a high enough discharge Lipo, the MOSFET could just overheat and burn up.

[aznriptide859]

1. For a Supercore, yes. I have both the teeth in my HS P90 removed as well - though it's short stroked 2 teeth on a M120, it's still fine. For other pistons that depends - my A&K M4 was running a stock spring.
2. Hmm, never thought of that - most of the bigger name ones (Extreme Fire/AWS) come with lipo-protection or something along those lines.

[MetallicaFatCat]

The only ones I would avoid are the Infected ones and the ones in the classifieds. I'd personally go with Extreme-Fire's because Terry is very helpful.

[XavierMace]

You should also add in, no cheap Chinese crap.  You know, like Element High Speed gears.  :p  It's just going to cause you headaches in the long run.

Quality parts and a good shim job are by far the biggest factors in the gun running reliably.  I run 11.1v 20C+ LiPo's in pretty much all of my guns, only one of which has a MOSFET.  The only failure I've had was on the high speed TM P90 (nylon bushings melted after 10k+ rounds).  All of the ICS's as well as the KWA have been running perfectly, most of which are stock guns.  I've never had to adjust my AOE or remove teeth from a piston.

I would also add in, replacing the plugs with Dean's and replacing the wiring on cheaper guns.  It's certainly possible to run most LiPo's on the stock connector but you are just choking your guns performance and adding in another point of failure.  Tamiya/Kyosho connectors weren't designed for the kind of amperage LiPo's put through them.

^ I agree on sticky and 7.4v lipo packs. The only thing, that I don't really like about 7.4v lipos is the extra risk from lipo batteries. Sure there smaller and have more amps (most cases) but you still need a special charger and an over-voltage protector, which you should add in there or else you, your gun and battery may go up in flames.

They are smaller, lighter, and perform better in the cold as well.  If you know where to look, the battery is cheaper as well.  I paid $20 a pop for 7.4v 5000mah 30C LiPo's, they work great.  I've never seen someone use an over-voltage protector and you only need a low voltage alarm if you have no common sense.  The degradation of your guns performance is clearly noticeable far before the alarm goes off.  Any half decent LiPo is not dangerous as long as you follow the instructions.  I know that's asking a lot for some people but that's not the batteries fault.

[ctres94]

I think xm has some very good points here, I would also like to add that you might want to expand a little bit on what greases and lubricants should be used. here is something I found very helpful.
http://www.airsoftforum.com/board/Airsoft-Lubricants-Sili-t114544.html

[The Conqueror]

Regarding regrease, I generally use generic white lithium grease (found at any hardware store) for all moving parts (pistol, gears, tappet plate) and TM silicone grease for compression parts (piston O-ring).

Just thought I'd help a little in the spelling  Haha, so you misspelled piston, and then here's another!

I've done these mods to almost every gun I've received/owned/sold, but my latest gun (the COD MW2 M4) has been upgraded with nothing but the state mods, and has lasted over 2k rounds on a 11.1v 1200mah 20C lipo with no issues whatsoever.

Guess that's supposed to be "stated"..

I definitely second the sticky vote, as this will stop all the "Is my gun LiPo ready?" threads, hopefully  Great guide Riptide, keep up the good work!

[aznriptide859]

^Fixed.

I'll add the parts later this week - finals week

[Webster_XC#23]

Ahh good luck on your finals

I would also add in, replacing the plugs with Dean's and replacing the wiring on cheaper guns.

Definately. I had a LiPo wiring disaster in my KWA when my stock motor began to wear out. There was like 18ga wiring or something in there that was low quality (cause I made my own AB mosfet and didn't know much about wires back then...) and as my motor "backed up" with excess voltage, the insulation on all of my wires melted, and I'm damn lucky I didn't short my LiPolly. My gearbox looked like a rainbow after that I've also had friends melt their tamiyas together when they want to try my LiPolly, and end up ruining all of my deans-->tamiya conncetors. I also agree with the sticky. There are many people out there who have questions and dont realize how simple it can be to do this.

[aznriptide859]

Updated with more info. Let me know what else you'd like to see in here. I don't want this to be a lipo-reference thread though - I remember writing one some time back, but I don't know where it went

Also put a few examples in - some of the recent guns I've sold are all lipo-ready, and through their testing I've found them to work very well.