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Old 10-22-2012, 11:01 AM   #379 (permalink)
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Join Date: Oct 2007
Location: Oakville, Ontario

Well it's not hard to think of an easier way to adjust the velocity, really. The SL-68 II has an easier method of adjusting velocity than down the barrel, and it's also a Nelson design. The only thing is that it adjusts velocity not by increasing or decreasing mainspring tension but by obstructing airflow through the bolt by varying degrees, just like a Tippmann blowback. Certainly an easier adjustment to make, but it also means that the marker has to be sprung in such a way that it can get up to velocity with the screw all the way out, in case it's cold and you're using CO2, or your paint is really tiny, or whatever other factors. Then when you need to shoot a lower velocity, say it warms back up or you buy new paint and it's a better fit to your barrel, you chrony back down but you're still using the same amount of gas. It ends up being kinda wasteful, and also means your pump stroke will be heavier than necessary.

If you have a regulator on your Nelson then you can adjust your velocity that way just fine as well, but most Nelsons don't have regs on them, especially not at the ~$150 pricepoint, so that's out.

What's left? We aren't going to adjust velocity through mainspring tension since that's too annoying to get to. We aren't going to diffuse the airflow because it's inefficient. We aren't going to regulate airflow because it puts us over budget and adds too much complexity compared to the problem we're trying to solve. So perhaps we can try reducing the volume of gas used per shot from the other end of the marker.

We could have a threaded back cap on the valve and easy-swap valve springs - but that leads to some pretty coarse adjustments and you also need to degas between adjustments. Not the best, especially for anyone without some kind of on/off system. Especially if they're using 12 grams. Ok, so what if we have a threaded nut on the back cap that adjusts the tension of the valve spring, rather than having the cap come off to swap springs? That sounds pretty good actually, however now we have to think about how easy it will be to turn that screw when the valve is pressurized, and consider if it will come unscrewed when under pressure. This means higher precision for the machined parts back there and a little more design time into how to thread the body. We also need to make sure that you can't accidentally remove the screw while the marker is pressurized, and also make sure that you can't easily screw it in so far that you damage the cupseal or powertube. This is getting a bit complicated and might drive the budget up as well.

So it looks like the best system overall is to change velocity with a regulator, but that's not going to make it into the $150 budget, and also adds complexity and isn't necessarily the most compatible with the varying gas systems used on pumps. 12 grams are usually not used with regulators, and you would also need to make sure your regulator works with both CO2 and HPA if you're going to sell it bundled with a budget marker and be necessary to adjust velocity. Seems like a tall order for the price point. The other best option was direct mainspring tension adjustment, which is gas system agnostic, and best of all, cheap and simple. The only problem is that it takes a little longer to do than most of the other methods when you're using a 14" allen key down the barrel. How else can we adjust the mainspring tension? We could make the body easy to open up and swap mainsprings, but that's again a coarse adjustment and not optimal for bring up your velocity by 10-20 FPS or so, and also requires more thought into how to build the marker body that way.

And now I've exhausted my list of ideas on how to adjust the velocity on a Nelson and come to the conclusion that the best overall system, especially at the price point of the Hammer 7, is indeed sticking a long allen key or flathead down the barrel.

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