Replacing on board pumps?

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Neptune
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Replacing on board pumps?

Postby Neptune » Mon Feb 03, 2014 7:12 pm

I want to have a ss100 have a bigger pump, much like an(a?) xp105, but would like the pump to still be attached/tracked to the main thing. I have a general idea of how I'm going to do this, but was wondering if anyone had done something like this before?
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DX
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Re: Replacing on board pumps?

Postby DX » Mon Feb 03, 2014 8:48 pm

You can just glue/attach the end of the new pump to the existing handle. It's only difficult if you want to make it clean. Note obviously that you need to replace the pump with one that seals in both directions, no bike pump will suffice and most nerf pumps won't, either. Ben plans on replacing his 100 pump to make it larger, not sure if he's had time to do it yet, PM him.
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Re: Replacing on board pumps?

Postby marauder » Tue Feb 04, 2014 9:48 am

Hey Neptune, I am wanting to do this on my own 100 as well. I have some ideas in my head, but I need all the parts in front of me first in order to figure out a way to describe it. If you are going to replace your pump you probably will want to replace your check valves with something larger. In fact, this project may call for rehauling over 50% of your internals. My 100 is still in my parents attic, and I'm focused on school so I've only gone so far as to look at check valves an other parts online.

FWIW I replaced the stock nozzle with a Max D nozzle and it has a thicker stream. Something to think about doing. I just cut off the orange tip that sticks out, smoothed it out, and then glued a tapered Liquidator Nozzle over the opening and used water weld on the outsides to reinforce it. Works better than before.
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Re: Replacing on board pumps?

Postby Neptune » Tue Feb 04, 2014 8:32 pm

I do have a broken max d gun... The thing is is that I have my only 100 at the moment and it is pretty good quality for a 24 year old gun, I had to reinforce the backing of the pump with some E resin and mesh tape to fix a snapped pump but otherwise thinking of keeping it at least externally looking super clean.

Though, I may take one of the worse nozzles of a 200 and put the max D on it, I'm getting a leaky 200 off of ebay I want to try to repair and improve, this will most likely go to that. I am thinking of using a 105 for the pump, or even that same max d 5ks pump with some teflon tape under the o ring to make the seal better so it sucks water as well. I like the old soakers for nostalgia purposes so really if I could get a 100 or 200 just good enough to compete with basic xps I would be more than happy.

I wonder though if you could get away with a slightly larger pump, and somehow convert that (bushings?) to strongly and snuggly fit over the stock pump. The check valves would be sort of lack luster but that may actually work. Maybe a new head on the pump rod to match the new tube and everything will look... mostly clean.
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Re: Replacing on board pumps?

Postby marauder » Sun Feb 16, 2014 12:10 am

*bump*

I'm looking at replacing the Gorgon's stock pump with a larger diameter pump. I am wondering, do I need to expand the size of the other internals to do this?
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Re: Replacing on board pumps?

Postby HBWW » Sun Feb 16, 2014 9:35 am

~3/4" pump:
http://www.isoaker.com/Tech/Internals/i ... xp150.html

http://www.isoaker.com/Tech/Internals/i ... ss300.html

~1/2" pump:
http://www.isoaker.com/Tech/Internals/i ... s2100.html


In addition, the pumping process does not move water quickly enough for the flow of the other internals to be a bottleneck. There's no real rule about how much flow must be in the other internals before and after the pump either (although perhaps there's a range of ideal ratios); it takes extreme cases of too little or too much flow provided for that to be a problem. Your standard APH or CPH design reaches that "too much" area, with 1/2" sch. 40 PVC. It still works, but there's excess volumes of water in the internals to fill and clear out, so that's the main reason you don't want too much flow in the internals. However, someone with more knowledge of fluid dynamics would provide a better explanation.

But to actually answer the question, for a Gorgon it shouldn't make a difference unless the internals are so small that they contribute to pump lag. (I'm not sure how the pump lag is being caused in the Gorgons DX has, but if the problem wasn't there before, then it definitely shouldn't be an internals flow problem.)

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Re: Replacing on board pumps?

Postby Drenchenator » Sun Feb 16, 2014 10:33 am

No, you shouldn't have to expand the diameter of any other parts to accomodate the extra flow. And even if the flow rate becomes to high, you can always pump more slowly, but I highly doubt that will ever be an issue. I think the biggest issue with replacing a pump in a stock gun is finding the right size tubing to use as a pump shaft, since you have to consider the space provided by the chamshell exterior.

The reason APHs and CPHs have smaller diameter pumps has to do with the pressure, not the flow rate. Typically APHs and CPHs have much higher pressures (40 or more psi), and these higher pressures directly lead to a higher force to pump. A 3/4" pump on an APH will be extremely hard to pump unless you are a strong adult. I made a chart comparing this problem to other stock guns a few years ago, and concluded that you can only generate about 30 psi with a 3/4" PVC pump and about 60 psi with a 1/2" PVC pump (within the range of forces used by Larami and Hasbro).
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Re: Replacing on board pumps?

Postby HBWW » Sun Feb 16, 2014 11:44 am

I've never gotten a chance to work with a CPH with decent pressure. McMaster LRT is nowhere at that of a CPS 2000's bladder. APH's, on the other hand, are different. After building my first one, I found that I don't need the ridiculous pressure it can offer; the high pressure seems to lead to bad stream lamination and range no matter what nozzle I try, which is a good reason to switch to a 3/4" pump; faster pumping, lower pressure ceiling, and less dropoff.

The pressure is more important for water weapons designed for it, such as thick-bladder CPS's (*ahem: DX's ridiculous 21k's)

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Re: Replacing on board pumps?

Postby marauder » Sun Feb 16, 2014 3:57 pm

That's a great article. I seem to imply from it that PSI isn't the most important factor in power and range. Consider the SS 300, it has a 3/4" pump and yet is capable of shooting up to 50 ft. So with that in mind, I shouldn't have to worry about my Gorgon's range dropping if I up the pump size to 3/4".

The stock pump stroke is 6 and 3/8" long. I measured this by disassembling the blaster and then actually measuring how far the pump moved. It provides about 25 ml per stroke, which comes out to 3.921ml per in for the 1/2" stock pump. Does anyone have the formula for predicting how much water a 3/4" pump would move? I currently do not have a stock blaster with a 3/4" pump on hand to test.

It would be easier for me to just lengthen the stock 1/2" pump, but I don't think it would be worth it vs the gains I could make with a 3/4" pump. Making the pump longer would just make the gun more awkward. I did some testing and figure that I could add about 2.5" more to the 1/2" pump, before the gun starts getting more awkward to pump/use. 2.5" length gain would give me an overall pump volume of about 35ml or about 1.18oz/pump. This would be comparable to the pumps featured on the XP 110/XP 310. Here are some stats to consider for larger pumps on AP blasters: SS 300 89ml, XP 150 82ml, , XXP 275/250 68ml, XP 105 60ml

With a stock PC capacity of 17 oz/503ml it takes about 20 pumps to pressurize, adding 2.5" would in theory bring this number down to 14 pumps, but replacing the pump with one comparable to the 150's would bring the number down all the way to 7. Another way to look at it is how many shots can you get between pumps. After doing some simple calculations I'm getting a 29% increase in shots or shot time per pump with a 2.5" extension, and 330% increase with a pump replacement. The first would be a good improvement in combat performance, the second would be huge. I'm looking into transparent nylon tubes for the replacement or extension. I love the idea of being able to see the water being pumped. I may go with a clear tube, or I may go with an orange, yellow, or cyan tube.
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Re: Replacing on board pumps?

Postby the oncoming storm » Sun Feb 16, 2014 5:09 pm

Pardon me, but the 300 has a 1" pump diameter and hits 55' (with 20 pumps of precharge and 18 of water)
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Re: Replacing on board pumps?

Postby Drenchenator » Sun Feb 16, 2014 5:48 pm

Pressure isn't always the determining factor in performance -- flow rate, nozzle size and type matter too -- but it's still important. The pressure given in the article is peak pressure for the air pressure guns. The pressure increases as you pump in an air pressure gun, so the peak pressure would be the one you'd care about when designing the pump, since it determines the maximum amount of force you need to pump it. In air pressure guns, the pressure drops quickly, so this peak pressure is kinda useless as a performance measure.

Still, 20 to 30 psi is usually good enough for high performance assuming everything else is right. In fact, the SS 300 patent is titled "Low pressure, high volume pressurized water gun," which just shows that they weren't too concerned about the pressure, and still got a top-notch performance.

A 3/4" pump with the dimensions you gave has a volume of 46 mL. To calculate this I just found out the total volume of a cylinder that size ( V = 0.25 * pi * d^2 * l ). I used inches for the units, so the volume was given in cubic inches. I converted this to mL by typing in "2.8164 cubic inches = ? mL" into Google, which did the rest.
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Re: Replacing on board pumps?

Postby HBWW » Mon Feb 17, 2014 9:24 am

It's easier if you convert everything to metric, then calculate the volume of said cylinder in CC's, which is equivalent to mL. I have my 6th grade science teacher to thank for that!

I don't know the SS 300's pump, but I figured it's the same diameter as the 150's, which is just slightly higher than the ID of sch 40 3/4". I ended up simply referring to it as 3/4" even though it's 1", so thanks for the correction, storm.

The problem with APH's is pre-pumping. Homemade water pumps have more dead space than stock, and the higher pressures required more air. You can't reach a good ratio (reference the LPD thread at SSC), so you can't get much shot time at full pressure. Even when you do, the flow is far too turbulent to be of any use.

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Re: Replacing on board pumps?

Postby Neptune » Fri May 16, 2014 9:47 pm

Tiny update! I have a ss200 I fixed, and a cps 1200 with a broken tank and check valve. I don't feel like fixing the 1200 it's in bad shape, but the pump fits snuggly over a 200. So I'm probably going to cut back the 200's pump a lot, leave maybe a centimeter of dead space, and then have the 1200 replace it. It's a little but it's something, plus not so much I can't make it all fit in the shell. If the CPs 1200 grommets on the pump go, I can repair those right?
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