Pre-engagement and FPS issues.

Varjeal · November 23rd, 2014, 13:56

Greetings.

I've a VFC M4 that I've recently installed with the following:

SP120 Lonex gearbox
Lonex A-1 motor
SMU-non ab
7.2V lipoV battery or 9.6V nunchucks are all I use.
363mm 6.03mm VFC Psalm barrel (yeah I know its gimmicky but I wanted to try it out.)
Varied between madbull 3in1 hopup, prowin, and stock. (having feeding issues but that's for another topic)
Black madbull bucking w/shredder nub

The story is that I need this to shoot a maximum of 420 fps and I'd prefer to stay closer to the 400-410fps mark. The advert for the mechbox states an fps range up to 440, and after a shim adjustment and compression check (compression was actually quite good) this easily attains the advertised maximum fps and more, which is a problem.

Second part of the equation is that the motor *overspins* (corrected from previous) (ie locks up solid) with a 110 spring after only a half dozen shots, so simply down-grading the spring isn't going to work with this combo.

I'm looking for possible solutions and need some advice on what is the most practical and reliable method of "down-tuning" to achieve reliable operation. I'd really like to keep the A1 motor in the equation if at all possible.

Thanks for your time and consideration.

Styrak · November 23rd, 2014, 14:37

How are you getting pre-engagment with only a 9.6v or a mild lipo, on an M120 spring?

pestobanana · November 23rd, 2014, 14:56

Sounds like you don't know what pre-engagement is.

Take a video of the gun locking up.

lurkingknight · November 23rd, 2014, 15:12

what they said.

You done something else wrong.

Varjeal · November 23rd, 2014, 15:19

Piston locked halfway back with sector gear in wrong part of rotation. Wrong terminology apparently. Something else I should be looking for? re: oops...ah nevermind..not pre engagement...overspin....yeah that's it.

pestobanana · November 23rd, 2014, 15:24

Its normal for the piston to be halfway back after a shot.

Varjeal · November 23rd, 2014, 15:25

Not when it locks up the gearbox. Erratic FPS where one shot might be 440 the next three 167, etc.

Ranger11 · November 23rd, 2014, 15:52

Drop an active braking mosfet in it.

Wrath144 · November 23rd, 2014, 15:58

Alternatively you could use the M120 spring but short stroke the sector gear to lower the fps.

pestobanana · November 23rd, 2014, 16:01

A MOSFET with braking will not do anything to help his issue.

Erratic FPS would be from your hop up unit not feeding properly, or nozzle misalignment. It has nothing to do with the spring.

Varjeal · November 23rd, 2014, 16:20

Thanks Wrath. Issue resolved.
@pesto: Yeah, I was aware of the feeding issue, but I dealt with that seperately.

The primary issue I wanted to deal with first was the overspin while trying to use a lighter spring to lower fps. The solution was basically to continue use of the heavier spring and short stroke the sector as mentioned. I needed that working properly before trying to sort out the feed issue.

Turned out the erratic FPS was due to too short a spring on the front of the hopup unit leaving space between the hopup and gb face. The "bounce" sometimes worked and sometimes didn't.

pestobanana · November 23rd, 2014, 16:31

So is the issue that your gearbox is jamming or that there is overspin?

Varjeal · November 23rd, 2014, 16:34

Overspin. As soon as the 120 spring went back in the overspin went away.

ThunderCactus · November 23rd, 2014, 17:19

So it overspun, precocked the piston half way, then didn't have enough torque to start back up?

If that's the case with the LiPo, you need a stronger motor. The A1's aren't torque motors, and if you're running standard 18:1 gears, you'll need a neo magnet motor for an SP120. It will also reduce overspin as neo magnets offer more resistance than ferrite magnets to help stop the armature.

pestobanana · November 23rd, 2014, 17:24

So is it getting locked up or not? You just told us it was getting locked up, now you're saying its just overspin...

A1 isn't a torque motor, but it should be plenty for pulling a meager M120 on 18:1 gears. Even a 16TPA ferrite motor has no problem pulling a M120 with a 9.6.

If you are saying its jammed simply because you can see the piston in the rear windows, there's nothing wrong with that. Its normal if you have overspin. You can reduce overspin by adjusting your cutoff timing, there is no need to use a heavy spring and short stroke. That is the method of dem nabs.

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November 23rd, 2014, 13:56	#1
Varjeal Banned Trader rating Join Date: May 2011 Location: Beaumont, Alberta	Pre-engagement and FPS issues. Greetings. I've a VFC M4 that I've recently installed with the following: SP120 Lonex gearbox Lonex A-1 motor SMU-non ab 7.2V lipoV battery or 9.6V nunchucks are all I use. 363mm 6.03mm VFC Psalm barrel (yeah I know its gimmicky but I wanted to try it out.) Varied between madbull 3in1 hopup, prowin, and stock. (having feeding issues but that's for another topic) Black madbull bucking w/shredder nub The story is that I need this to shoot a maximum of 420 fps and I'd prefer to stay closer to the 400-410fps mark. The advert for the mechbox states an fps range up to 440, and after a shim adjustment and compression check (compression was actually quite good) this easily attains the advertised maximum fps and more, which is a problem. Second part of the equation is that the motor overspins (corrected from previous) (ie locks up solid) with a 110 spring after only a half dozen shots, so simply down-grading the spring isn't going to work with this combo. I'm looking for possible solutions and need some advice on what is the most practical and reliable method of "down-tuning" to achieve reliable operation. I'd really like to keep the A1 motor in the equation if at all possible. Thanks for your time and consideration. Last edited by Varjeal; November 23rd, 2014 at 15:24..

November 23rd, 2014, 14:37	#2
Styrak Trader rating Join Date: Jan 2007 Location: Saskatoon, SK	How are you getting pre-engagment with only a 9.6v or a mild lipo, on an M120 spring? __________________ Airsoft Sales and Repair/Upgrade Services

November 23rd, 2014, 15:12	#4
lurkingknight "bb bukakke" KING! Trader rating Join Date: Jul 2011 Location: Ottawa	what they said. You done something else wrong. __________________ I futz with V2s, V3s and V6s. I could be wrong... but probably, most likely not, as far as I know.

November 23rd, 2014, 14:56	#3
pestobanana Squid Porn Superstar, I love the tentacles! Trader rating Join Date: Nov 2008 Location: Richmond Hill and Waterloo, Ontario	Sounds like you don't know what pre-engagement is. Take a video of the gun locking up.

November 23rd, 2014, 15:19	#5
Varjeal Banned Trader rating Join Date: May 2011 Location: Beaumont, Alberta	Piston locked halfway back with sector gear in wrong part of rotation. Wrong terminology apparently. Something else I should be looking for? re: oops...ah nevermind..not pre engagement...overspin....yeah that's it. Last edited by Varjeal; November 23rd, 2014 at 15:23..

November 23rd, 2014, 15:24	#6
pestobanana Squid Porn Superstar, I love the tentacles! Trader rating Join Date: Nov 2008 Location: Richmond Hill and Waterloo, Ontario	Its normal for the piston to be halfway back after a shot.

November 23rd, 2014, 15:25	#7
Varjeal Banned Trader rating Join Date: May 2011 Location: Beaumont, Alberta	Not when it locks up the gearbox. Erratic FPS where one shot might be 440 the next three 167, etc.

November 23rd, 2014, 15:52	#8
Ranger11 Extra Salty and vinegar Trader rating Join Date: Apr 2013 Location: Red Deer, Alberta	Drop an active braking mosfet in it.

November 23rd, 2014, 15:58	#9
Wrath144 formerly steyr Trader rating Join Date: Sep 2005 Location: Winnipeg, Manitoba	Alternatively you could use the M120 spring but short stroke the sector gear to lower the fps. __________________ BROFORCE Admin - Winnipeg Airsoft

November 23rd, 2014, 16:01	#10
pestobanana Squid Porn Superstar, I love the tentacles! Trader rating Join Date: Nov 2008 Location: Richmond Hill and Waterloo, Ontario	A MOSFET with braking will not do anything to help his issue. Erratic FPS would be from your hop up unit not feeding properly, or nozzle misalignment. It has nothing to do with the spring.

November 23rd, 2014, 16:20	#11
Varjeal Banned Trader rating Join Date: May 2011 Location: Beaumont, Alberta	Thanks Wrath. Issue resolved. @pesto: Yeah, I was aware of the feeding issue, but I dealt with that seperately. The primary issue I wanted to deal with first was the overspin while trying to use a lighter spring to lower fps. The solution was basically to continue use of the heavier spring and short stroke the sector as mentioned. I needed that working properly before trying to sort out the feed issue. Turned out the erratic FPS was due to too short a spring on the front of the hopup unit leaving space between the hopup and gb face. The "bounce" sometimes worked and sometimes didn't.

November 23rd, 2014, 16:31	#12
pestobanana Squid Porn Superstar, I love the tentacles! Trader rating Join Date: Nov 2008 Location: Richmond Hill and Waterloo, Ontario	So is the issue that your gearbox is jamming or that there is overspin?

November 23rd, 2014, 16:34	#13
Varjeal Banned Trader rating Join Date: May 2011 Location: Beaumont, Alberta	Overspin. As soon as the 120 spring went back in the overspin went away.

November 23rd, 2014, 17:19	#14
ThunderCactus Not Eye Safe, Pretty Boy Maximus on the field take his picture! Trader rating Join Date: Feb 2007	So it overspun, precocked the piston half way, then didn't have enough torque to start back up? If that's the case with the LiPo, you need a stronger motor. The A1's aren't torque motors, and if you're running standard 18:1 gears, you'll need a neo magnet motor for an SP120. It will also reduce overspin as neo magnets offer more resistance than ferrite magnets to help stop the armature.

November 23rd, 2014, 17:24	#15
pestobanana Squid Porn Superstar, I love the tentacles! Trader rating Join Date: Nov 2008 Location: Richmond Hill and Waterloo, Ontario	So is it getting locked up or not? You just told us it was getting locked up, now you're saying its just overspin... A1 isn't a torque motor, but it should be plenty for pulling a meager M120 on 18:1 gears. Even a 16TPA ferrite motor has no problem pulling a M120 with a 9.6. If you are saying its jammed simply because you can see the piston in the rear windows, there's nothing wrong with that. Its normal if you have overspin. You can reduce overspin by adjusting your cutoff timing, there is no need to use a heavy spring and short stroke. That is the method of dem nabs.

Pre-engagement and FPS issues.

Doctor's Corner