Why are blowbacks "low end"?

[paintballfiend]

I agree completely. While we always strive for zero tolerance, we do accept a standard deviation from design, this is usually within a set specification. This is referred to as the rejection region when performing tests.

Conclusion, while the manufacturer accepts a deviation of +/- .010, they are actually designing and aiming for +/- 0.000. They are willing to sacrifice to amount tooling/material required because the product falls within an acceptable deviation of the spec.

http://www.uwsp.edu/psych/stat/z.htm

The above link is an example of a z-table. The shaded region shows the acceptable outcomes. This is a range of deviation that is determined to be acceptable. If a manufactured product falls outside of the shaded region, it is rejected.

I am now speaking inferrential statistics, ugh. Paintball is supposed to be fun, not technical! Still an enjoyable discussion though.

Them internets is hurting my head.

I have a question, how many engineers or guys studying to be engineers are on here? I know it's off topic but I'm undecided right now.

[Lohman446]

I agree completely. While we always strive for zero tolerance, we do accept a standard deviation from design, this is usually within a set specification. This is referred to as the rejection region when performing tests.

Conclusion, while the manufacturer accepts a deviation of +/- .010, they are actually designing and aiming for +/- 0.000. They are willing to sacrifice to amount tooling/material required because the product falls within an acceptable deviation of the spec.

http://www.uwsp.edu/psych/stat/z.htm

The above link is an example of a z-table. The shaded region shows the acceptable outcomes. This is a range of deviation that is determined to be acceptable. If a manufactured product falls outside of the shaded region, it is rejected.

I am now speaking inferrential statistics, ugh. Paintball is supposed to be fun, not technical! Still an enjoyable discussion though.

The unfortunate thing is, that sometimes when it comes to it its better to have something that will work with an allowed deviation - that being said the Spyder design that allows deviation, and works, has some distinct advantages (cost wise, production, etc) over a design that allows minimal (Yeh, Im looking at the Mag). I would hate to think of the amount of scrap AGD had to refuse because of there design and quest for that perfection.

I don't think we are really disagreeing on anything. I just like to sometimes point out that although from a design aspect allowing 0 tolerance sounds like a great thing, tight tolerances are not always an advantage in the manufacturing world - or in the end the retail world.

[tae]

I think I may have confused things a bit. How I read things, was designing a better blowback was giving inconsistencies in performance. With the higher tolerances being more precise machining/engineering,(as I would expect from AKA )what exactly is this "abnormal reliability" experienced?

[shartley]

[emumikey]

Shartley

this is a great example of the point I was trying to make, thank you. You are referring to the AR15 and later the M16 I assume. Another great example is the AK - an incredibly sloppy rattle trap that is indestructible.

[mag_lover05]

i think they are low end because they always work...i mean who wants a gun that always shoots? i sure dont.

[shartley]

Shartley

this is a great example of the point I was trying to make, thank you. You are referring to the AR15 and later the M16 I assume. Another great example is the AK - an incredibly sloppy rattle trap that is indestructible.

You are welcome. Yes, those are two examples, but there are many others as well.

[Lohman446]

Actually in the discussion of tolerances in relation to blowbacks (low end blowbacks) do you think that is "designed slop" or simply a great allowance of lesser tolerances because the system has "slop" in it.

[Toll]

From what I understand of the system, loose tollerances were worked in because they were low end, rather than vice versa.

Chances are the new player with a spyder will not take care of it very well, they need to give him a bit of leeway as to not make him throw it to the ground in frustration.


I'm very tempted to pick up a merlin body and see what can be done with it in the way of a blow back spring return, but I have no real idea how to manufacture one...which would probably make the test rather poor

[emumikey]

Actually in the discussion of tolerances in relation to blowbacks (low end blowbacks) do you think that is "designed slop" or simply a great allowance of lesser tolerances because the system has "slop" in it.

I would think it would vary from manufacturer to manufacturer. Some design for slop, say exactly .5 mm free play (for the o-rings). Others may just get luck.

I would say designed slop might be found in autocockers in the fittings for the ram and 3-way arms to prevent binding (make sense?)

manufacturing slop (not designed and not within tolerance) would be found in the stingray. believe me I know, I have one!

[Lohman446]

The thing is, if you design something that is designed to allow slop (for function issue) does that not make it more likely to allow looser tolerances as well?

[emumikey]

The thing is, if you design something that is designed to allow slop (for function issue) does that not make it more likely to allow looser tolerances as well?

No. Looser tolerances are an error on the part of the manufacturing side. We are still getting confused between tolerance and "slop."

If you design for 1 mm of slop and get it, that would be ideal.

If you design for 1 mm of slop, and get a range between .5-1.5, that would be a big problem.

Example, an interface between an autococker bolt and body. Assume it is designed to have one mm of slop as opposed to a zero fit. They allow for a .05 tolerance in manufacturing. If all goes well, they end up with a range in fit between .95 and 1.05, this is acceptable because it is negated by the oring effected area.

If the manufacturers produced the same design with a range between .80-1.20, this be unacceptable. The tighter end would cause bolt stick and the looser end of the range would cause air loss. Simply unacceptable.

Make sense? I wish I was better at examples but I think we have covered it pretty well.

[Lohman446]

However, you set tolerances. Some designs by nature will work with +/- .01 (just an example, number has no meaning). Others will not work without tolerances of +/- .001. Obviously the one with the great allowable tolerance should be cheaper to produce.

[emumikey]

However, you set tolerances. Some designs by nature will work with +/- .01 (just an example, number has no meaning). Others will not work without tolerances of +/- .001. Obviously the one with the great allowable tolerance should be cheaper to produce.

Wrong. Sorry to be so blunt. I think we mean the same thing, just speaking a different language. A design will always work better the closer the tolerance is to zero, regardless. Any +/- variation in tolerance is only acceptable as long as it doesnt hinder the design.

You are interpreting tolerance as the gap between parts? This is a misinterpretation. tolerance is the deviation from the designed looseness.

Picture this: You are trying to design a box to hold a ball. The requirements are: the box must hold the egg, and if I shake the box, the ball will not wiggle inside...

Wierd analogy. But, if you design the box so that the surface of the ball touches each side of the box, it will fit, but not wiggle. The tolerance would be the deviation in the size of the ball that allows you to squeeze the ball into the box, yet without any free play. This is your +/- tolerance. Anything too big, and the ball doesn't fit. Anything too small, and the ball will move around inside.

are we getting warm?

[Lohman446]

I understand what you are saying... but take the difference between a ball and an egg

If the outside of the egg fits at 10 and will not break until 9 you might shoot the design to be 9.5 +/- .5.

If you have a ball - ie less likely to break, say to 8 it allows you to design to 9 +/- 1. A great tolerance usually means cheaper to build.