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Swarmpede wiring question


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#1 ChIck3n

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Posted 12 July 2012 - 09:36 PM

Ok, so I've decided to build a swarmpede for hvz and need a bit of help with the wiring. The others I have seen done have all had various switches, batteries and circuits to run in various fire modes (stampede, swarmfire, or both). What I would like to do is have them both run off of one battery pack, and have two triggers instead of switches. The normal one for the stampede, and some sort of momentary thumb trigger (i'm thinking use one of the unneeded locks in the stampede) for the swarmfire so I can drop/change mags in the stampede with my index finger and fire the swarmy with my thumb. Here is a high quality rendering of the circuit I tediously thought out...

Posted Image

Now, I have no intention or need to fire both guns at the same time. The swarmy will basically be a super fast firing cover gun while I reload the stampede. The problem with my design is that it still ALLOWS the two to be fired at the same time if my finger were to slip while firing either one. Would both guns firing at the same time put too much load on the 4 trustfire 3.7 volt batteries to cause an issue? Or would it just cause both guns to fire at a lower rate? I'm not quite sure about the electrical aspect of these batteries, but know that they are a bit more finicky and risky than your basic protected batteries. I'd rather not add a second battery pack to the gun to put each one on a separate circuit, but if there is a safety issue I can probably find somewhere to stick them. I usually don't mind just trying stuff and seeing if it works, but when it comes to electricity I'd rather be on the safe side and ask someone with more experience.

Any advice is welcome, as well as more ideas for my "frankengun". So far the stampede has volt, spring (6kg), AR removal, the back half cut down like SGnerf's SMG mod with a longstrike stock attached to it, and a 2.5' blowgun lashed on to the top rail. Still debating cutting down the front of the stampede as I heard it may decrease accuracy for the sake of range, and I have the blowgun for range. The swarmfire is still on the way.
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#2 Xellah

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Posted 12 July 2012 - 10:29 PM

I've worked on many a Stampede (14+) for various players on campus for HvZ so I might be able to help.

Yes, you will most likely experience problems when firing both blasters through a single 4 Trustfire battery pack. Your replacement spring in the Stampede (it's from OMW, correct?) will require your motor to use up most of the current in order to compress the spring and cycle the action. I have tested a Stampede with an OMW spring replacement + ACE #115 + stock spring with 5 Trustfires before without a problem (cycling that is; the spring rest shattered from the force after ~150 darts). But 4 Trustfires between two blasters is iffy, even when accounting for the small amount of energy required to cycle the Swarmfire.

I would recommend having a battery pack for each blaster on independent circuits to keep it simple. Trustfires have a high enough mAh to run for quite some time in a Stampede alone but when run through both blasters (with different motors and spring constants) it may deplete their charge at an unexpected rate. For the purposes of use in your blaster combo it might not matter though. I have run 4 TF packs through many different spring combos but never through two blasters at once.

Some additional info to help in your modding:
-Trustires hate the cold. If it's 45 degrees or below out, expect your Pede to not cycle properly. Especially with a spring replacement, as this requires even more work to be put on your batteries.
-Watch out for breakage on the spring rest of the Stampede's plunger tube. I usually reinforce this piece with epoxy putty whenever I do spring replacements.

I hope I could help! Here's the Stampede I mentioned earlier(shameless additional picture):

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#3 ChIck3n

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Posted 14 July 2012 - 01:43 AM

Thanks for the advice! I'm just a bit confused, how would running two blasters at separate times deplete the batteries faster? My main question (probably lost in the wall of text) was if running both at the same time would damage the batteries or anything else. I have no intention of doing this on purpose, but the wiring I have set up would allow it on accident. Just want to make sure my blaster won't catch fire if I accidentally hit the swarmfire while firing the stampede! When I get the swarmfire I'll see if I can find a place to put another battery pack on it, but don't really have a place to put another one on the rear of the stampede since I put the longstrike stock on it.

What part exactly is the plunger tube spring rest? The little round part on the back that screws on to the bigger tube?
Doubt I'll have much of a temperature issue, as I'm playing in Texas! But I'll keep it in mind if something goes really wrong with the weather.
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#4 Aeromech

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Posted 14 July 2012 - 10:47 AM

This really is just a question of circuitry. To accomplish what you wish to do, invest in one or more momentary switches. You expressed your desire to use two triggers, but it may be easier to have two momentary swtches inside the magwell of the stampede. May I suggest setting up a circuit in which a momentary switch is placed inside the magwell, which when depressed, completes the circuit to the stampede; have another momentary switch, but when this one is depressed, it opens the circuit to the swarmfire. The Swarmfire and Stampede circuits would be in parallel, but only one "loop" would be closed at a time. I am not an electrical engineer, (I don't know what to call the complete-when-depressed switch vs. the open-when-depressed momentary switch,) but if these two switches are placed side by side inside the magwell, you may alleviate the need for two triggers. When the Stampede mag is depleted, and subsequently released, the swarmfire would take over from the same trigger until you replaced the magazine.

Edited by Aeromech, 14 July 2012 - 01:05 PM.

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#5 Darthrambo

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Posted 14 July 2012 - 01:49 PM

Wiring like that should be perfectly fine, and since its parallel you shouldn't see any drop off in rate of fire even if both are being shot at the same time. (Not an EE but I pretty certain this is the case)

If you are worried about draining your battery I recomend picking up some 18650 size ultrafires. They are basically just AA ultrafires but bigger with the same voltage but longer life. They are actually cheaper than AAs and you can buy trays for them of ebay for cheap.
Because of the make up of these batteries they weigh almost the same as AAs too.

If you do cut off the front, where would you put the swarmfire?
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#6 zx532

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Posted 14 July 2012 - 07:22 PM

Another thing you could do is put some sort of toggle switch right in front of the trigger, and instead of wiring it "on/off" wire it "swarmfire/stampede"
toggle switch

(I don't know how much you know about electronics, if you decide to go with this method, you will need a switch with three prongs on the back, not just two)

Good luck
(send me some pictures when you're done, this sounds awesome!)
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#7 ChIck3n

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Posted 14 July 2012 - 11:55 PM

Ah, thanks for all the help. I may look into that toggle switch if I can find a place to stick it, as the goal I have in mind is to be able to operate it quickly and easily with one hand while changing mags with the other.

Though if there is anyone out there who knows more about the electronics aspect I would love to hear from you. If there is no safety risk of occasionally firing both at once I'll just stick with the second thumb trigger. Not really overly concerned about a little extra discharge rate, as I can charge it between HvZ missions. If I go through enough darts to discharge the batteries I still have a backup set, and if I go through them the zombies have earned their kill. Dead batteries = OK, exploding batteries = not OK! I've done wiring and stuff before, but am not sure what exactly an "unprotected" battery means and what is no longer being protected.

And I'll be sure to post pics and maybe a writeup when I'm done.

Edited by ChIck3n, 14 July 2012 - 11:57 PM.

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#8 Darthrambo

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Posted 15 July 2012 - 02:28 AM

You are fine man the draw from the batteries from a parallel circuit will be faster but wont be dangerous at all.
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