Overspin/Double-firing on first cycle only

[jem]

Hi all,

 

Recently did some work on my Specna SA-H02 (416). First gun I've taken apart, definitely a learning experience.

 

I'm noticing some double-firing (occasionally triple-firing) in semi-auto, but only on the first trigger pull after connecting/disconnecting a battery.

 

Thinking this is just a little overspin caused by the 11.1v batteries I'm now using, and the Aster's AB is just taking a second to kick in after that first cycle.

 

Does this sound reasonable an assumption?

 

Changes I made:

- Installed a Gate Aster v2, following Gate's video and documentation

- Reshim of the stock gears, following Chupacabra Outdoor's video exactly

- SHS piston, rocket cylinder head and nozzle

- SHS motor

- Cleaned the entire gearbox and shell with hot, dish soapy water and relubed following TheAirsoftTech's video, using Superlube

 

Thanks!

 

 

Edited January 22 by jem

[Lozart]

What have you set up on the Aster? Is there precocking on semi?

[jem]

14 minutes ago, Lozart said:

What have you set up on the Aster? Is there precocking on semi?

 

Sorry, meant to include this!

 

I've tried Active Braking on both Adaptive and various manual levels, no difference in the overspin on that first cycle.

 

I did play around with both manual and auto pre-cocking but noticed no difference in the overspin with it on or off. It's off for now.

 

Also set a 20 RPS limit, though this unsurprisingly didn't change the overspin either.

[Adolf Hamster]

Auto precocking could cause this.

 

When it first powers up it doesnt know the timing of the system, so intentionally overruns on the first shot to time it, then from that info it can set a more appropriate precocking timer.

 

 

[jem]

40 minutes ago, Adolf Hamster said:

Auto precocking could cause this.

 

When it first powers up it doesnt know the timing of the system, so intentionally overruns on the first shot to time it, then from that info it can set a more appropriate precocking timer.

 

 

Interesting! thanks.

 

This still happens even with precocking disabled though

[Lozart]

When you shimmed the gearbox, did you make sure that the sector gear cam is still reliably being seen by the Aster sensor? It may be a bit borderline.

[jem]

1 hour ago, Lozart said:

When you shimmed the gearbox, did you make sure that the sector gear cam is still reliably being seen by the Aster sensor? It may be a bit borderline.

 

Good point, but surely the issue would occur more randomly in that case than just the first trigger pull after a battery's connected? 😭

[Lozart]

Good point, well presented.

 

Does it do it with a 7.4v battery?

[jem]

20 hours ago, Lozart said:

Good point, well presented.

 

Does it do it with a 7.4v battery?

 

Thanks!

 

I'm yet to test this (all my 7.4v are Tamiya, don't have the means to rewire them right now and a friend's borrowing my adapter...)

 

Will try to remember to post the results when I get to it

[AttackBunny]

On 22/01/2024 at 12:18, jem said:

 Reshim of the stock gears, following Chupacabra Outdoor's video exactly

never seen this video before, crazy detail for anyone looking to shim a box. Thanks! 
 

 

[Colin Allen]

2 hours ago, AttackBunny said:

never seen this video before, crazy detail for anyone looking to shim a box. Thanks! 
 

 

It is a great guide to shimming; I have been using his approach recently with excellent results.

[Sewdhull]

Wish he'd done one for the mp5, I've been busy this evening...

[jem]

On 23/01/2024 at 20:07, Sewdhull said:

Wish he'd done one for the mp5, I've been busy this evening...

 

Does that not just use a regular v2 gearbox? should be the same no?

[ak2m4]

What's the SHS motor out of interest?  Be careful with that Adaptive AB setting and 11.1v, can easily spanner a motor.  As Loz says try with a 7.4 and well worth getting a basic soldering kit for the battery connector conversion.

[Sewdhull]

1 hour ago, jem said:

 

Does that not just use a regular v2 gearbox? should be the same no?

Yeah the gearbox is the same, but the grip covers the whole gearbox so when the motor is installed you can't see it where the pinion meets the bevel.

I cobbled some tube etc together to position the motor, shimmed the bevel then I'll sort motor height in due course. Maybe this eve...

[Sewdhull]

Braking a brushed motor creates at least as much damage as running it.

 

Voltages will be higher (limited by the speed the magnetic field collapses at) and you are effectively shorting the motor for varying periods of time(MOSFET switching on and off) and that energy all turns into heat.

Brushes don't like it either.

 

Higher torque motors suffer more since they produce more braking torque.

[ak2m4]

58 minutes ago, Sewdhull said:

Braking a brushed motor creates at least as much damage as running it.

 

Surely if the motor has a hard brake instead of a soft break that's going to impact the motor quicker?  I'm just going on what I've seen in the past ten years.  I'd say 90% of the motor returns / failures I've had from customers have been caused by the Titan adaptive AB feature, or at least that's the one thing they all have in common.  Perhaps it's something else that's going on with the feature.

[Dan Robinson]

1 hour ago, ak2m4 said:

caused by the Titan adaptive AB feature

 

Interesting information.   Do you have a suggestion for the best setting for this feature? 

[Sewdhull]

Yes hard braking will be worse for the motor than softer.

Running any brake also means there's less time for the motor to cool between instances of running.

 

Because motors are enclosed cooling can be an issue anyway.

Brushes have a hard time as well as the armature windings.

 

Most neodymium magnets will permanently lose magnetic strength(even after they have cooled again) if they get near 80C which will increase the current the motors run at, because the back EMF which limits voltage will reduce and therefore current will increase at the same revs making the motors heat up even quicker.

Once the motor is out of its design parameters it will go south quickly.

Ferrite magnets tolerate around 3 times that temp.

 

The best setting is none, but if you need it, the weakest braking is the next best.

 

Even in the cold the motor can get very warm in use as your hand tends to warm up the grip limiting heat transfer away from the grip, which has poor thermal transfer from the motor because it's surrounded by air anyway.

 

Not running your motor hard is the key to motor longevity I think.

[AttackBunny]

10 hours ago, Sewdhull said:

Not running your motor hard is the key to motor longevity I think.

you’re just trying to ruin the sport for everyone with an ARP 9 and a drum mag by saying this! 

[Lozart]

On 26/01/2024 at 21:07, Dan Robinson said:

 

Interesting information.   Do you have a suggestion for the best setting for this feature? 

 

Titans have an issue with cheaper/low TPA motors. They may have changed this with later firmwares as the Asters I have don't seem to suffer the same problems.

 

AB is best turned off if you can and use the bare minimum you actually need, but as far as the Titans go, use better motors (I replaced mine with an ASG Ultimate CNC 28000 and it's been fine ever since).

[ak2m4]

On 26/01/2024 at 21:07, Dan Robinson said:

 

Interesting information.   Do you have a suggestion for the best setting for this feature? 

 

It's only a very small percentage, few years back I've spoken to a few other retailers about this and they have report the same issue.  I've only ever had it reported on 1 of my XT 22TPA motors since selling (about 3 years).  More people using short-stroking in combination of 7.4v batteries seem to have reduced the issue.  

 

I've come across at least 2 ASG motors that exhibited the same symptoms so I'm not convinced it restricted to any certain grade of motor.

[Sewdhull]

High currents can stress etus, some never had great MOSFETs, but also low tpa, poor magnets don't give you great braking, you need TPA to give you braking effort and low tpa give the braking more to do...