Measuring compression - consistently - measuring

so i’ve decided to actually build / buy (probably build) something to measure the exit pressure of the barrel which will tell me if i have an air leak indicating an issue or general maintenance wear

pretty easy to build but it dawns on me i have no clue what pressure range i need to be building for.

a quick search for HPA indicates that its somewhere between 450 and 800

wondering if anyone has gone down this route already and can provide a lessons learned


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How will you measure the exit pressure ?
Blocking the end of the barrel and checking the pressure is not good nor usefull ?
The pressure you want to measure is behind the gel on it’s way up the barrel so you would need to install the pressure gauge just in front of the t piece which would seem difficult.
FPS checks on a regular basis is the best test for an air leak.
But the pressure range could be as low as 30psi up to 100psi or more depending on the spring used.

Blocking the end as it were with an upper pressure relief valve.

The aim isn’t to know what is behind the gel but to be able to measure when maintenance is due

Fps checks are gel dependant and at present, a reasonable indicator

But why do something properly when you can do it to excess?

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Because blocking the barrel puts the whole system under very high pressure load that it wouldn’t normally be expected to withstand in normal use and if you were to hit auto fire you could potentially destroy the piston rack or gears.

Maybe squeeze a car wheel valve body over the inner barrel and put a tyre pressure gauge on it? I doubt it will read much pressure tho… the nozzle to T piece will let pressure out.

A gel blaster doesn’t really push the gel out with ‘pressure’ as such… it pushes it out with air flow… like a blow g*n (pea shooter)… movement of air, not compressed air

This is not correct, pressure is required to increase velocity :wink:

If you use an identical spring but gels varying in dia. The gels that are too small will leak pressure and therefore be slower , gels that are too large will have higher pressure but more drag so will also be slower and this can be tested easily .
The best gel will be the one that creates the highest pressure with the lowest drag.
And this is why fps is the best measure available.

I disagree, there is a greater pressure behind the gel caused by the movement of air from the cylinder being pushed by the spring/piston… but for the air to be compressed, the gel would have to be able to basically block the barrel until the build up of pressure forces it to move.

If a gel was so tight in the barrel, tight enough to cause compression… the friction would just rip apart the gel.

A gel blaster is like a glorified pea shooter… when you blow a pea shooter, the air is not compressed… otherwise you would go to blow it and pop out another couple of haemroids… a pea shooter and gel blaster use air movement :grin:

A pea shooter also needs pressure, try blowing a small pea out of a larger dia. tube.
Your just imagining very high pressure but the pressure behind the ball isn’t very high and it doesn’t need to be, in a blocked system the pressure would be high.
30 or 40 psi is a lot of pressure and most people don’t realise how much that is.

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Seen somewhere vid,
Hpa using gels.
They messing around with volumes
The pressure they said set @70 psi.
Must hav sum herbs in it for that.
Rattler more tech knowledge than me.
I tried figure out someway to calculate earlier.
I sorta cam up with a rough rule of thumb… might be wrong?
Giv or take, in a sqr inch of atmospheric pressure is about 1 bar /14.5psi.
Giv or take depending on cylinder i’d and stroke.
Roughly Equiv from cm3 to 1 inch.
X that by force of spring.
Guestimate a 1.1 spring utilise 2kg
2x 14.5 = 29 psi.
1.3 spring rough utilise about 3kg = 43.5 psi.
And So forth.

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Very true. Most car tyres run pressures in that range.
Even if you could somehow connect a blaster to a tyre valve, I don’t fancy your chances of actually inflating it :roll_eyes:

Love your attitude mate :+1:


i want one of THOSE o’rings!


To give you an idea how much 40psi is, it’s the equivalent of placing a 1600lb weight on you hand, this equates to appox. 40psi. :thinking:

so some really good side thoughts have come out of this thread and it seems to me that what we really need is to measure air volume under meh pressure at the end of the muzzle.

in this way we can simulate airleaks without creating them whilst measuring how effective the whole assembly is at delivering the full air volume to the end of the blaster.

dawns on me this would be easily done with a low tech brewer’s vapour lock (the S bend variety) and a small reservior of water.

volume would then merely be the displacement of water.

so tall and thin would give me more of a gradient for accurate measurement.

as i type this out though, and as simple as it is to do, fresh gels and the chrono …

on that front…armourTech here i come! my last batch of gold milkies have been rubbish :frowning:

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Or you could just buy a small regulator and set it at 45psi then pressurize the system and hold it to check for leaks.
The piston would need to be in front of any porting to test and nozzel closed
But your method sounds far more scientific :rofl:

Btw don’t get too excited about the ArmourTech’s , I found them to be as inconsistent as anything else available :frowning:

in a bizarre similarity my present process to check for leaks is to ensure the breach is closed, and blow down the barrel.

if i lose pressure in my face…its leaking which recently means i forgot to lube the nozzle…because i’m old and forgetful like that.

armourtech :frowning: hopefully not as bad as my last batch of gold milkies…struth…what’s a muppet got to do to get a decent supply of fungible pellets :sob:

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There is no compressed air in a blaster. It would need something to hold compressed air and a mechanism to release it. The piston pushes the amount of air in the cylinder through the nozzle and the gel moves down the barrel with the flow of air

Like those little electric fans (so called compressors) you put on a car intake… supposedly an electric ‘supercharger’. They are not a compressor as they don’t compress the air, they are a fan that moves the air

A gel blaster and a pea shooter use the flow of air provided by lungs or the piston or cylinder/piston… the only time a cylinder on a blaster compresses air is if you put your finger over the end and push the plunger towards the nozzle (like testing a seal) … a gel ball is incapable of blocking the end of the nozzle (like a finger)… the increased pressure from the flow of the air from the cylinder moves the gel easily at the same velocity as the air flow…as long as the gel ball is the correct size for the id of the barrel… too big for the barrel, the gel will break, too small, it will be overtaken by the airflow and dribble out of the barrel.

A gel blaster and gel ball is not unlike you and a water slide… the gel ball is introduced into the barrel via the T piece like a person getting into the ‘breech’ of a waterslide (although the water is already running)… the blaster piston comes forward and pushes the gel… the person drops into the flow of the water…the gel goes with the air flow, the person goes with the water flow the gel flies out of the barrel and the air dissipates… the person flies out of the end of the waterslide and the water goes back in the pool.

It is flow, no compressing laughing%20(1)

Wrong on every point above :+1:

I know you are wrong on every point :+1: