My first High Speed Build

[Sloth]

M4 cqb 8mm ver 2.

16awg silver wire + deans
VS alum cylinder head
stock ported cylinder
Modify Hi Speed Piston -7 metal teeth short stroked
SHS 13:1 gearset, sector gear short stroked
Element super torque motor
alum spring guide with bearing
M110/120 Spring
Bushings and a sector clip
Need a basic mosfet to use with microswitch and lipo

Suggestions?
This is my first rof project, what am I missing?
I need a piston head and sorbo right?
share your thoughts please!!

[pestobanana]

Did you short stroke from the pickup side or release side of the sector gear?

[Sloth]

Originally Posted by pestobanana

Did you short stroke from the pickup side or release side of the sector gear?

Going to do pick up

[pestobanana]

If you want to use a sector delay clip and you get close to or higher than 30 RPS you need to SS from the release side otherwise you will have tappet plate pre-engagement and have horribly inconsistent FPS.

Sector delay clip is not really necessary anyway, I have a 30 RPS gun feeding fine without one.

I also find short stroking completely unnecessary unless it's to prevent tappet plate pre-engagement with a sector clip.

[Sloth]

Originally Posted by pestobanana

If you want to use a sector delay clip and you get close to or higher than 30 RPS you need to SS from the release side otherwise you will have tappet plate pre-engagement and have horribly inconsistent FPS.

Sector delay clip is not really necessary anyway, I have a 30 RPS gun feeding fine without one.

I also find short stroking completely unnecessary unless it's to prevent tappet plate pre-engagement with a sector clip.

Informative! Should I test the setup before short stroking to see how it goes?
I'd like to throw around 35rps, thats my target. Pre-engagement Badd.

[pestobanana]

Test it before short stroking without a sector clip. If you need a sector clip then SS it.

[K3vX]

Let's clarify the use of shortstroking. It's used to prevent what is called "pre-engagement" of the sector gear to the piston. In a setup where the sector revolution is extremely fast, there is a possibility of the sector gear engaging the piston before it returned to a rest position, thus potentially breaking teeth, pulling the piston too far back and other funny failures. Lightening the piston assembly can reduce this problem, but only to a point. That is when you reduce the travel movement of the piston, so it'll return in place faster.

Now, let's go on the list one by one.

- 16 AWG wire is good, but be sure the gearbox you have can fit it.
- The hell is "VS"? As long as it fits and has a o-ring, it should be okay. I'd personally stick with a more reputable brand.
- Stock cylinder is fine. Check inside if it's smooth.
- Personally not fond on Modify parts, but a piston's a piston. I'd either get the Lonex Red one for the same price, or a cheaper SHS one. Like I said before, there is no need to shortstroke, but I'd remove some weight, even if it's labeled "High speed". My piston weights 12g (without the piston head) for example.
- Gearset is good. Like before, read the shortstroke statement.
- Google can't tell me on this motor, but as long as it works and has Neodymium magnets, it should be okay. SHS are a good choice in that price range too.
- Spring guide with bearings is good, be sure to remove the bearings from the piston head to reduce the weight.

Also, if you want my opinion, and you will hate my answer, but start by making this rifle 100% efficient with 18:1 gears. Change the motor for a neo motor if you want, change the piston if you need, but stay with 18:1. Get a grasp of all the things that could go wrong, make your teeth on the gearbox, learn why each parts need to be replace or not replaced.

Then swap the gears for the 13:1. Normally if you made everything else before, it should be a breeze, and the only thing you'll have to worry will be the shimming if the new gearset.

[pestobanana]

Short stroking and piston lightening to prevent pre-engagement are myths. Piston pre-engagement is caused by jams, not a gun cycling too fast. If a gun could actually cycle that fast you'd have a plethora of feeding problems, the sector gear contacts the tappet plate before engaging the piston again.

VS is a shit-tastic brand that Huang carries, but it's a cylinder head so who cares.

I personally like Modify pistons. I have a Modify Quantum in my 450 FPS 30 RPS gun and it still looks pretty much new. This gun is using a 11.1 with standard 18:1 gears so like K3vX said test it with your original gear set first, you can get a pretty good rate of fire without high speed gears. Also lightening the piston assembly can help increase rate of fire by 1 or 2 RPS but it's not really that important. Unlightened piston, aluminum piston head and bearings, yet I'm still doing 30 RPS with no issues.

[Stealth]

Originally Posted by pestobanana

Short stroking and piston lightening to prevent pre-engagement are myths.

Oh really? Have you tried to build a gun around an M100 spring, unlightened piston assembly (with bearings), 10:1 gears, Lonex A1 motor and 11.1v 60amp lipo?

After 3 separate failures, I'm not a fan of Modify Quantum pistons. I've 3 separate failures on them - front of piston cracking, 2x piston under pick-up tooth caving in. The ABS plastic used isn't ideal and could use a mixture with more nylon fiber.

[pestobanana]

Originally Posted by Stealth

Oh really? Have you tried to build a gun around an M100 spring, unlightened piston assembly (with bearings), 10:1 gears, Lonex A1 motor and 11.1v 60amp lipo?

After 3 separate failures, I'm not a fan of Modify Quantum pistons. I've 3 separate failures on them - front of piston cracking, 2x piston under pick-up tooth caving in. The ABS plastic used isn't ideal and could use a mixture with more nylon fiber.

No, but I've test fired with M90, 13:1, unlightened piston assembly, Lonex A1 and a 11.1V 80 amp lipo and only had tappet plate pre-engagement. Does that count?

Maybe I've just had good luck with Modify stuff. I've only ever used one quantum piston and it's survived in that gun for a year and a half so far.

[wind_comm]

Originally Posted by pestobanana

No, but I've test fired with M90, 13:1, unlightened piston assembly, Lonex A1 and a 11.1V 80 amp lipo and only had tappet plate pre-engagement. Does that count?

Maybe I've just had good luck with Modify stuff. I've only ever used one quantum piston and it's survived in that gun for a year and a half so far.

sure, it'll test fire fine, but anything short of Riots and an SHS 15 that'll shred itself in a hurry

to the OP, 30 rps isn't exactly "high speed". there's guys pushing 50 full stroke on ASM with no problems. before I switched my build to the slowest motor known to man, it pushed 35 pretty much by accident.

I think I said this before, but the fastest setups have m150s.

[ThunderCactus]

80A lipo? Where did you put this 80,000Mah battery on your gun?

[Stealth]

Originally Posted by wind_comm

sure, it'll test fire fine, but anything short of Riots and an SHS 15 that'll shred itself in a hurry

to the OP, 30 rps isn't exactly "high speed". there's guys pushing 50 full stroke on ASM with no problems. before I switched my build to the slowest motor known to man, it pushed 35 pretty much by accident.

I think I said this before, but the fastest setups have m150s.

+1

A piston of a particular weight, traveling at y velocity based on the spring strength, will not move faster than the gear train and you just can't defeat physics like that.

Unless of course you've come up with a phenomenal super-glide piston rail system that allows the it to move much faster than normal thus creating a larger pressure system, increasing FPS. But the increased FPS would negate the requirement of using an M90 spring in the first place, so what's the point?

[pestobanana]

Originally Posted by ThunderCactus

80A lipo? Where did you put this 80,000Mah battery on your gun?

3.3 Ah x 25C = 82.5 A discharge doesn't it?

Originally Posted by Stealth

+1

A piston of a particular weight, traveling at y velocity based on the spring strength, will not move faster than the gear train and you just can't defeat physics like that.

In order for pre-engagement to happen because of sheer speed you'd have to have massive feeding issues first. The nozzle would be halfway back by the time the the pickup tooth engages the piston again. With a sector clip and M90 I start getting tappet plate pre-engagement somewhere around the 27 RPS mark, at 25 RPS I'm fine, which tells me that at 25 RPS the piston is at the full forward position before the sector gear turns the 20 degrees or so necessary to begin engaging the tappet plate again.

Piston weight doesn't seem to have a significant affect on FPS output, that says to me it shouldn't have a significant affect on piston return speed.

[wind_comm]

particularly awesome lipos are available in something like 90C, so 80 amps isn't hard to do at all.

Originally Posted by pestobanana

3.3 Ah x 25C = 82.5 A discharge doesn't it?

In order for pre-engagement to happen because of sheer speed you'd have to have massive feeding issues first. The nozzle would be halfway back by the time the the pickup tooth engages the piston again. With a sector clip and M90 I start getting tappet plate pre-engagement somewhere around the 27 RPS mark, at 25 RPS I'm fine, which tells me that at 25 RPS the piston is at the full forward position before the sector gear turns the 20 degrees or so necessary to begin engaging the tappet plate again.

Piston weight doesn't seem to have a significant affect on FPS output, that says to me it shouldn't have a significant affect on piston return speed.

your singular good luck (unless something about the reality we live in has changed recently) doesnt change physics or the documented cases of failure in the manner we're describing, nor would I want to ever recommend somebody to build something badly.