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Editor's Note: The original version of this FAQ contained references to Teflon(R) brand PTFE, a material used in lubricants. While PTFE is made by several companies, only PTFE manufactured by DuPont carries the Teflon(R) name. After WARPIG, and some of WARPIG's sponsors received letters from the DuPont corporation threatening legal action in response to Mr. McComber's mentioning their product by name without listing the trademark registration, we have removed these references and simply replaced them with PTFE.
Teflon is a registered trademark of the DuPont corporation.
This text covers some of the basic information concerning lubricants and their use in paintball guns. It is intended as a guide to help the owners of paintguns in their selection of proper lubricants. This is not a complete tribology text.
A description of some of the composite and synthetic materials
used in paintguns is included, as well as a section on o-ring use.
The non-metallic components are suseptible to chemical
attack from solvents and incompatible oils and greases. The results of
such attacks can cause damage in the form of deformation, deterioration,
reduced service life, and accelerated failure rates. These types of damage
to o-rings and plastic parts cause paintguns to develop abnormal operating
characteristics such as sluggish actions, excessive drag of moving parts,
CO2 leakage, valve malfunction, frequent ball breakage, as well as high
maintenance. It is impossible to list all compatible
and incompatible substances here, but here are a few common ones:
O-RING/SEAL COMPOUND -------------------- S - SILICONE (*) P - POLYURETHANE N - NITRILE T - PTFE S P N T COMPATIBILITY RATING LUBRICANT +--------------- -------------------- --------- | SILICONE GREASE | 3 1 1 1 1 - GOOD VASELINE | 4 1 1 1 2 - FAIR SEMI LUBE V.14 | 2 1 1 1 3 - DOUBTFUL MOTOR OIL | 4 1 1 1 4 - UNSATISFACTORY KC TROUBLE FREE | 2 1 1 1 X - INSUFFICIENT DATA WATER | 4 1 2 1 BRAKE FLUID | 3 4 3 X CONSIDERATIONS: Temperature range, swelling, degradation, seal integrity, both static and dynamic. (*) Silicone o-rings should not be used as dynamic seals, and require special considerations. (see O-RING SEAL USE)
One common measurement of viscosity is Kinematic. It is done by measuring the time it takes a fixed volume of oil to travel through a capillary tube with gravity, at a certain temperature. The unit of measure is called a Centistoke (cSt).
Not all oils respond to temperature in the way described
above. The property of resisting changes in viscosity due to temperature
change is expressed as Viscosity Index. The higher the V.I. of an oil,
the less tendency for its viscosity to change with temperature. Look for
a V.I. of at least 250.
The viscosity of the oil will increase as the oxidation progresses, as will the presence of sludge and acids. These sludges may deposit on sliding surfaces, causing them to stick or wear. The acids may be corrosive to metal components of the paintgun. The addition of an anti-oxidant to the oil's base component, will improve its resistance to oxidation.
Silicone is good at resisting acids and will operate over a very wide range of temperatures, however it is not a very good choice for use as seals in paintguns because of its susceptibility to damage from petroleum products. Silicone rubbers tend to absorb silicone fluids, resulting in swelling and softening of the compound. Silicone o-rings are usually blue-white, clear or rust-brown in colour.
Nitriles are one of the best choices for use in paintguns. O-rings with a high nitrile content are good at resisting chemicals and can be designed to endure wide temperature variations. Nitrile o-rings must contain some plasticizers in order for them to function at extreme temperatures. Silicone lubricants tend to remove the plasticizers from the nitrile, causing excessive hardening and/or shrinking. Almost all nitrile o-rings are black in colour.
Polyurethane o-rings are used in paintguns because they are resistant to petro-chemicals and wide ranging temperatures and weather. They offer very good performance in abrasive environments, but lack the ability to withstand acids, ketones and chlorinated hydrocarbons. Polyurethane o-rings range in colour from yellow to off-white.
Polycarbonate resins (Lexan) are not used in the mechanics of paintguns, however they they are worth mentioning here for safety reasons. When lexan comes in contact with most petroleum products, fine cracks begin to appear, called "crazing". Crazing weakens the polycarbonate and eventually leads to complete failure of the structure. This effect is most severe when the lexan is under stress. ALL PAINTBALL GOGGLE SYSTEMS USE POLYCARBONATE LENSES. Most paintguns, ESPECIALLY SEMI-AUTOMATICS, will at some level, spray lubricant out and away from the paintgun. CHECK YOUR GOGGLES FREQUENTLY FOR CRACKS, they tend to form at the edges of the lens, where the lens contacts the frame of the goggle.
Nylon like PTFE and delrin is mainly used as a structural component, and in some cases as a fastener. As a seal, nylon is used in washers for static crush type applications. It is generally compatible with petroleum fluids.
Delrin is used to produce machined composite parts, such as bolts, pump handles, ball indexing ramps, and other mechanical parts. It is used where weight savings and durability are are required. Delrin is a known as a "self-lubricating plastic". This is because the compound has built in friction reducing ingredients similiar to PTFE.
PTFE is used primarily as a structural component in areas that require smooth operation, like valve guides, and bolt/hammer connecting rod sleeves. As a o-ring seal, PTFE is too stiff to be used in anything except static, compression type seals. PTFE is almost completely non-absorbant, and will not hold enough oil to aid lubrication. It is also finely ground and added to some lubricating oils to enhance the oil's slipperiness. When used in this type of application, PTFE (PolyTetraFluoroEthylene) is typically used in resin form, . PTFE o-rings are usually white in colour.
Static seals like the one under the power-tube retaining cap on a Nelson- based valve system, uses nitrile because it doesn't move during use. The o-ring around the top of a CA tank is static during use, but the compound used is polyurethane. This is due to the abrasive threads that it must pass through during installation.
Dynamic, or moving seals like the o-rings around the bolt and/or hammer in a semi-auto paintgun generally are made of polyurethane. These seals need to be abrasion resistant, yet flexible due to the reciprocating action. Silicone o-rings should not be used as reciprocating dynamic seals because of their lack of shear strength, low abrasion resistance and high coefficient of friction.
Another type of dynamic seal is the "cup" seal. These are not o-rings, but generally, made of the same polyurethane material. Silicone is sometimes used in brass "cup" seals.
Here are a few tips: Use a lube that is non-toxic. If you play
in cold, wet climates, use a lubricant that has a low viscosity, high V.I.
and has good oxidation stability. Hot, dry climates dictate an higher viscosity
or a very high V.I. rating. The best advice I can give is to use a lubricant
designed for paintball guns, or one recommended by the paintgun manufacturer.
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