Full Auto on Semi - but more to it

[Bar1975]

I need to describe the situation first so bear with me..

Been working on a stock VFC 417 AEG and recently added a GATE NanoHard mosfet along with a Tienly motor (GT 35K). I built an entirely new wire harness with milspec low resistance wire to accompany the mosfet install.

I also tuned the gearbox with the standard Sorbo Pad/AOE correction and lightened the piston by replacing the aluminum piston head and bearing with a poly piston head (removed bearings)

Everything else is stock..

When i fired up the gun initially i was using a 11.1V 15C lipo and everything ran smoothly.. ~27 rps with snappy semi auto. I ran Active Breaking with the mosfet initially...

Then i turned off Active Breaking and plugged in my 25C 11.1V and semi no longer worked.. i was getting what seemed like a 2-3 round full auto burst (this wasn't the mosfet as this feature is not available on the nanohard)

I turned Active Breaking back on and the issue went away.. back to super snappy semi auto and i broke the 30rps limit..

i think i know what is happening.. Pre-Engagment... the super high torque motor/mosfet combo is now cycling the gears too fast with the 25C lipo (versus the 15c). The active breaking when ON is fixing this by keeping the cycle controlled....

but should i do the folllowing to remedy this.. (note: the sector gear has a delayer clip pre-installed)

1. replace spring with m120 (i believe the stock is ~m110.. im shooting ~365FPS) That should slam the piston forward fast enough?

2. short stroke the gears/piston by a copule teeth (how many?)

3. Both

4. Neither.. just run the 25C with Active Breaking ON

sorry for the short novel but i like to provide all the details for a more informed response

[ThunderCactus]

using torque up gears? 21:1 ratio?
Sounds like a cutoff lever issue.
AB should only be necessary on motors with weaker magnets.

[Bar1975]

Originally Posted by ThunderCactus

using torque up gears? 21:1 ratio?
Sounds like a cutoff lever issue.
AB should only be necessary on motors with weaker magnets.

everything not outlined above is stock.. believe the gears are standard ratio...

i've read and heard from people that the Tienly motors can cause this if the spring is not strong enough. They are so strong that they just get out ahead of the normal cycle..

Shouldn't be any issues with the cut off lever (gun is brand new i forgot to mention) as it works fine under every other condition but this particular set up/battery

[lurkingknight]

preengagement = sector gear grabbing piston in the middle of the stroke. This is why teeth 4-6 show greater wear or damage. Once those teeth are gone, 1 and 2 get stripped. This is not your problem.


overspin. gear train cycle speed is so fast such that the momentum of the gears after initial shot is enough to cycle the gears 2-3 more times able to overcome the resistance of the spring. This could be part if not all of your problem.

Cutoff lever. As the cutoff wears down, it is possible that when slow enough the lever will work as intended. When the gear cycle speed increases, it sometimes floats when activated, not hitting the trigger shuttle hard enough to knock it free. Sometimes this issue can come from the trigger contacts being too tight to the shuttle block as well.

Solutions?

check the engagement of the trigger contacts, then assemble a portion of the gearbox including the sector gear and trigger and contacts, turn the sector through the cycle slowly while the trigger is pulled to force the shuttle forward, simulating the firing position. As the sector turns and the cam hits the cutoff lever, the lever should trigger early and the shuttle should reset. If it feels like the sector is turning so far that the cutoff lever is being tripped near the top of the cam, the lever needs replacement.

fixing overspin requires knowledge of shortstroking. You need to increase the spring weight to provide more stopping power for the gear train. This requires a stronger spring that raises fps. Short stroking by removing teeth from sector and piston to draw the piston a shorter distance will reduce fps back to desired levels, but you need to know the exact fps the springs will shoot in your setup, and then remove the corresponding number of teeth.

[Bar1975]

Originally Posted by lurkingknight

preengagement = sector gear grabbing piston in the middle of the stroke. This is why teeth 4-6 show greater wear or damage. Once those teeth are gone, 1 and 2 get stripped. This is not your problem.


overspin. gear train cycle speed is so fast such that the momentum of the gears after initial shot is enough to cycle the gears 2-3 more times able to overcome the resistance of the spring. This could be part if not all of your problem.

Cutoff lever. As the cutoff wears down, it is possible that when slow enough the lever will work as intended. When the gear cycle speed increases, it sometimes floats when activated, not hitting the trigger shuttle hard enough to knock it free. Sometimes this issue can come from the trigger contacts being too tight to the shuttle block as well.

Solutions?

check the engagement of the trigger contacts, then assemble a portion of the gearbox including the sector gear and trigger and contacts, turn the sector through the cycle slowly while the trigger is pulled to force the shuttle forward, simulating the firing position. As the sector turns and the cam hits the cutoff lever, the lever should trigger early and the shuttle should reset. If it feels like the sector is turning so far that the cutoff lever is being tripped near the top of the cam, the lever needs replacement.

fixing overspin requires knowledge of shortstroking. You need to increase the spring weight to provide more stopping power for the gear train. This requires a stronger spring that raises fps. Short stroking by removing teeth from sector and piston to draw the piston a shorter distance will reduce fps back to desired levels, but you need to know the exact fps the springs will shoot in your setup, and then remove the corresponding number of teeth.

yes Overspin is the word i was looking for.. not pre-engagement! Your absolutly correct.

i have short stroked various AEG's before so no concern there.. i'll have to upgrage the piston though as it only has 1 metal tooth.

Think i will start with an M120 spring and see what that does first..

the 15C lipo works fine as well so maybe no need for the bigger battery...

[lurkingknight]

15C is not enough for a tienly motor. You're overdrawing that pack or very close to doing so. 30C-1500mah or better on one or both values would be more ideal.

constant draw will probably be around 20-25A tienlys draw hot, so you can safely assume 50-75A startup amperage is needed with that motor. If you have stock gears you might see a bit less but I would err on the side of caution and go bigger battery. That also means you're going to run out of juice pretty quickly because the teinly will consume more, faster to drive the gun.


A little bit of anecdotal evidence: I had a 13:1 setup with a lonex A1, constant draw was about 22A. I would get about 1800-2000 rounds out of the battery before needing a change. Since switching to a zci motor, it's slower top speed so I lost a few rounds per second but the motor turns with more torque so reaches top speed faster, so trigger response is just as snappy as the lonex a1, but the amp draw is now 13A. The same battery lasts almost twice as long. Before I would have to change the battery at lunch time during a game, now in similar circumstances it lasts the whole day.

[ThunderCactus]

I might have to try out a ZCI motor.
My tienly 30k draws the same as my ASG 30k on 13:1 gears, 22A.
Does about 18A on 16:1s

On 18:1, wouldn't be surprised if that 35K was drawing 18-22A.
Higher speed motor draw more amperage to start, but it only gets exponentially higher under load.

[Styrak]

Why not just run with active braking on? That's what it's for.

[lurkingknight]

because active braking kills motors.

[ThunderCactus]

active braking only kills motors when they're already drawing high amperage.
But it shouldn't be necessary on a tienly 35k...

[BenG]

Sounds more like overspin then PME, you need to use a heavier spring and short stroke the piston to get back down to your desired fps, and revolume your cylinder appropriotly to match the shorter stroke.

[BenG]

Originally Posted by lurkingknight

because active braking kills motors.

Ive used AB on every gun ive built in the past 4 years and ive yet to have one of the guns ive built ruin a motor, all with hundreds of thousands of rounds on them, yes AB will ruin your motor if you have a super high amp load, but if your drawing enough amps 30< then you have other issues.... lol. on regular builds AB might add a bit of extra pitting on the comm but nothing that a quick lap on the comm lathe every million rounds cant fix.

[Bar1975]

Originally Posted by BenG

Sounds more like overspin then PME, you need to use a heavier spring and short stroke the piston to get back down to your desired fps, and revolume your cylinder appropriotly to match the shorter stroke.

I have a Prometheus 407mm inner barrel with a 4/5 cut cylinder...

My field limit is 400FPS so if i add an M120 id imagine my FPS is upwards of 410+ FPS.. (compression is fantastic on this gun right now)

How many teeth would i need to short stroke and what would the resulting Cylinder need be? How exactly do you 'revolume' a cylinder?

NOTE: i have a sorbo pad on the cylinder head as well so already loosing some air volume.

[lurkingknight]

probably don't need to revolume the cylinder. Every manufacturer for springs is different Go 1 tooth at a time until you find the right fps.

[pestobanana]

Braking should almost never be necessary, and it destroys motors. I've had motors die in 20A setups with braking on. Yes you can repair the commutator, but if you let the pitting go deep and you turn it on the comm a lot, you will remove too much material and the copper will begin to come off.

Pretty much all double shooting issues can be resolved without the use of braking. Ensure that the trigger sled is releasing in a timely fashion without a lot of resistance. You can also bend the contacts apart to reduce release distance, and bend the cutoff lever up so it cuts off sooner.