Sewdhull
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Posts posted by Sewdhull
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So just out of interest I asked a lab friend of mine to measure the weight some of the BBs I have, all Vorsk ones.
Here's his summary.
Weight .43g .4g .32g
Mean 0.424 0.404 0.324
SD 0.002 0.004 0.001
RSD 0.5% 0.9% 0.5%
Median 0.424 0.403 0.324
The BBs were measured, 10 of each from a bottle, to 4 decimal places.
Mean is the commonly called average, SD the standard deviation, RSD is the relative standard deviation around the mean, and median is the middle value of the dataset.
The .32s had a max and min difference over the 10 samples of .005g, which is just 1.6%. Pretty good I reckon.
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for the thicknesses we can play with, its foams and butyl. Most systems need 25mm or more as the wavelength of the sound reduces ( frequency rises)
That's for polyurethane foam, I'm sure you cold find others.
The goal should be the least noise forward out of the silencer, so we should use diffraction and mass to achieve that.
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5 hours ago, Lozart said:
If you pump air from one tube into a wider tube, the pressure will drop when it enters the larger chamber. Simple physics. By adding wadding the pressure waves will be diffused far better than adding rubber or foam though. Something similar to acoustic wadding or felt would work well, closed cell foam or rubber doesn't actually give the pressure wave far to go.
Because of the differences in the way airsoft works compared to real firearms you need to stop thinking about how something like a real suppressor works and more like how you dampen a speaker enclosure or an exhaust muffler.
More to the point, as mentioned above - if we're talking about a can on an AEG, what comes out the front is way less of a consideration than what comes from the gearbox and piston assembly.
The can has a similar restriction on the front meaning the air will speed up again through the exit hole, I agree this is airsoft and the pressure is pretty low so the pop from the air isn't much and ultimately is probably better managed by voluming.
A firearms silencer is all about the combustion gasses and giving them a place to go depressurise and importantly cool down, decreasing in volume. Silencers cool to reduce the pressure...
In airsoft all we are doing in allowing the pressure to release slowly, however the gas doesn't cool and contract so playing with volume and baffles doesn't have the same effect.
More importantly, absorbing etc, the sound from the piston hitting the cylinder head is the goal, remove the resonance from the can and force the sound through holes which diffract the sound away from the path out the end of the silencer towards the sound absorbent stuff, what ever you use. Simple physics. There's not a lot of room in a can to fit the sort of foam which is effective on walls etc, and foam in speakers isn't about silencing like we are looking at, it is removing resonance from the cabinets so they sound better.
The holes are for diffraction and the spaces between the holes filled with something absorbent, there are many to choose from but space is limited so a denser foam, even closed cell types should be tried, but soft may work better, I don't have a range of foams to try. Rockwool is good, but may not have enough volume.
2mm butyl sheet inside the receiver is an idea I wanted to try, but never got round to it.
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On 25/05/2024 at 18:47, Egon_247 said:
And keep the rest for spares. 👍😁🤣
Hamster spare parts... its wrong.
- Nick G, gavinkempsell and Egon_247
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You can't diffuse the air in an open container, it just comes out the other end. I don't see how it's related to the volume of air. The cylinder air will just push the air ahead of it out. You can mitigate the pressure with squidgy things with a view to slowing the build up of pressure in the can like a spring absorbing energy. Air on its own will absorb this energy.
The pressure wave or sound wave is different and that's what we are looking to get rid of. The air isn't moving in that case, but a wave moving through the air, which you can deflect, absorb or reflect.
Holes deflect the sound direction or surfaces will.
Foams absorb the sound wave or filter it so what you hear is less noticeable.
The air pressure ahead of the BB is way lower than that behind it, when the BB exits the barrel it is unplugged and then the air pops out which whatever pressure is remaining immediately so I guess you want a larger void, a foamy one behind the BB.
A larger cross section of the silencer will slow the expansion more and the idea would be to have a gradual reduction in pressure so there is no pop, you don't need to absorb the pressure.
The amount of air (the mass and pressure) will be that same so the hole out of the silencer can't be too small or you'll get a similar pop when the the air compresses again to leave. That's taken care of by the BB needing an exit , around 10 or 11mm on mine.
I'm unsure I'm clear, it's late, apologies
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What is important is where the noise originates and how loud it actually is. The piston hitting the the cylinder head creates a sound travelling right down the barrel along with the excess air popping out the barrel.
Well volumed guns may have very little pop, but still have the piston slap noise.
You need multiple holes or the sound continues forwards, but honestly the sound levels aren't high to start with so the silencer effects might be lees than expectation and benefit from fewer holes.
The holes change the direction not the volume.
Interesting huh
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My thoughts and musings.
Red is Butyl, grey is hard foam or washer, green is sound. I haven't drawn in the barrel, but there should be a taper ( in butyl maybe) from it to the butyl in the first stage.
Send sound through a hole and it propagates outwards in an arc originating at the hole so long as the hole is small enough ( which it is in this case). The sound level reduces with each hole it passes through if steps are taken to absorb the sound after each hole.
An empty silencer can rings because of resonance, alter the resonance and can will absorb the sound instead.
Absorbent material like butyl is soft and dense, most metals are too hard to use, it will alter the resonance and absorb sound. Foams will only absorb sound. Rubber washers make good separators as does the rubberised foam in HVAC stuff.
The volume of air being moved is the volume of the cylinder, you need to reduce the speed of this to reduce the noise and/or absorb that noise. The diameter of the silencer will do this not the volume as the air will slow to fill a wider space but should be gradual to prevent a sudden release of pressure.
That amount of air will still be pushed out the end of the silencer so it is always important to not be over volumed or the exit hole of the silencer will behave just like the barrel end but with a larger, quieter exit.
The holes in the end of the silencer system will get larger further from the barrel.
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Tube comes in all sorts of wall thicknesses and diameters and tends to be telescopic too.
I forget the diameter, but a standard tube size fits inner barrels. I can look when I'm home.
You can use a thread lock or epoxy, sometimes it's an interence fit or requires heating/cooling
I've just got a hot melt glue gun, I don't know how I managed without one
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4 hours ago, ak2m4 said:
Looks to me like the aeg was left for a few weeks / months with the spring in a fully compressed state - imprinting onto the cylinder head pad.
Surely in an uncompressed state, but with the preload of installation?
Leading to the same thing. Rubber is soft and that alloy looks sharp.
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We only have some low pressure air and the sound of piston slap to get rid of.
The air needs a place to go and the sound needs holes to go through so it bends into the absorbent material of your choice.
You do need to deaden the metal tube.
I keepeaning to get some butyl in for speriments
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for shimming I use brass or stainless tube slipped over the barrel or fitted in the outer, none of this tape malarky
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Get the rubberised foam used on Hvac stuff, I got mine on amazon, also I have use drubber washers to provide the separation between elements. Or yoga mat material.
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I've looked at the video and spring tension reduction is probably not going to help, the is only a little resistance it looks like.
What would help is increasing the circumference of the round lever, with a rubber ring of suitable diameter. Making the lever heavier will help too.
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Perun do just a MOSFET, a simple switch, you'll need to solder it.
Acetech do one too. I have one of those, it's very good.
There's very little to them and they will prolong the life of your contacts.
Having said that you are on a 7.4v battery and a brushless so your currents will be low. You may not see any benefit for a very long time. If you put an 11.1 in you'll want a MOSFET.
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Without knowing how it works it difficult. Maybe a heavier striker, get some tig electrodes if you need tungsten, about 2-3 times as dense as steel, almost doubled the density of lead.
If it's sprung, a stronger spring from springs r us or similar online
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On 16/05/2024 at 22:54, Leo Greer said:
The one question I have (and this is hearsay, so mind yourselves), is that I've heard most airsoft brushless motors actually incorporated a ramping program specifically to slow down the startup, as early models had a habit of snapping their shafts. No clue where I heard this, but maybe something to look out for...
I don't believe motor shafts snap on starting like that, unless it's the pinions that fracture, but if there is ramping to start off with it's likely to keep the current down through the MOSFETs.
Start up currents can be much larger on brushlesses than brushed
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365nm emitters are cheap and as UV as you need. White LEDs will do the same thing, which ironically are UV LEDs with a phosphor coating. Shine a torch on the bbs and you will see a wide range of light wavelengths will activate the phosphors. It will depend on what phosphor is used.
I do not think it matters about the tracer colour. Red is not as bright to our eyes as green at the same energy and phosphors favour the green...
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The cost of getting a motor, any motor from good to great is really high as the differences tend to be small once you have for example moved to Neodymium magnets.
The start up delay comes down to the board driving the coils and sensing the position of everything, and honestly you aren't going to notice it unless you go measuring it. 7ms will be noticed by no one. Even 13ms. Your reaction time is about 250ms, if a semi shot takes 7 or 13ms longer to happen what is the effect and it's only relevant comparing brushless to brushless. That's if the experiment I saw can even be understood and is accurate.
I would ignore this factor.
Parallel windings are a way of getting more copper into the coils as thinner wires will sit more densely than a single wire of the same cross sectional area when they are all bundled together. It's harder to wind them so it costs more.
Each winding is made up of 8 parallel conductors each .3mm ( squared I presume) and there are 6 windings. 2 for each pole. The magnets on the rotor will have 4 poles so they don't line up with the 6 poles of the stator and stall the motor.
Magnet strength (the number in N45SH) is affected by temperature they get stronger when cooled below 20C and weaker as they get above 20C but the letters after the number tell you the temperature rating which changes because the manufacturer stabilises them for temperature to preserve their magnetic properties.
No letter and its 60C, SH is 150C again letters cost money.
It is still better to select a motor of the right speed and torque for your application. The problem with PWM is that the torque drops so the speed does which may not be a problem, but proper gearing or motor winding would be preferable. It's also less efficient. It's an added feature which may or may not be useful.
I used brushless motors extensively with drones and the software in the esc was really important to good performance and was adjustable, I think it's less important in Airsoft as they are single speed motors so the software can be simple.
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A slight aside, the Perun hybrid mosfet has power out put for such things as magazines and tracers.
Also I'd be tempted to connect the LEDs in series or parallel/series ( since you have 4 leds), you'd only need one resistor for limiting if any.
A project I'm interested in myself.
I notice that my UV torch makes for less bright tracers compared to pretty much all my white torches. Did you test the LEDs shining on a bb to gauge the effectiveness of the white or UV leds?
Sorry for all the input.
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Well at 60 fps the nozzle to bucking relationship is losing the air. I'm assuming all else is well.
So your options are worn or broken tappet plate, nozzle or bucking. Nozzles get wear inside and at the tip whacking the bbs all the time, tappet plates wear on the fin and buckings get worn lips...
Inconsistent air seal issues often fall to the nozzle and bucking meeting offline due to wear and then things get gradually worse. If a bb always comes out that's where I would start and just replace both the nozzle and bucking with the same thing as is there already.
BB Variation
in General Discussion
Posted
Well I would suggest if they are getting the weight right they are half way there at least. Perhaps I'll see if my lab buddy can look through a scope at a couple. I'm unsure how you would measure sphericity... Do you?