25 replies to this topic

[blastron]

I am attempting to add semiautomatic capabilities to my Maverick via electromagnetism. In order to calculate the amount of resistance I would need in my circuit and the number of turns in my solenoid, I need to know how much force it takes to cock a Maverick. Unfortunately, I am without any way to measure the properties of the compression spring within the Maverick's firing mechanism. Does anyone have this information?

For those interested in the details of this modification, I will briefly summarize. In order to easily dual-wield my two Mavericks, I will be adding a solenoid to the top of the gun, above the turret. A metal bracket will be added to the existing slide (much like frost vectron's slider repair) and attaching the solenoid's armature to that. A battery door would ideally be integrated into the Maverick's grip, allowing relatively easy battery changes in mid-combat. A sensor would be added to trigger the solenoid when the trigger is released. While this mod is still well within the design stages, I will most certainly document the construction process when I perform this rather involved mod.

[sn1per]

I am attempting to add semiautomatic capabilities to my Maverick via electromagnetism. In order to calculate the amount of resistance I would need in my circuit and the number of turns in my solenoid, I need to know how much force it takes to cock a Maverick. Unfortunately, I am without any way to measure the properties of the compression spring within the Maverick's firing mechanism. Does anyone have this information?

For those interested in the details of this modification, I will briefly summarize. In order to easily dual-wield my two Mavericks, I will be adding a solenoid to the top of the gun, above the turret. A metal bracket will be added to the existing slide (much like frost vectron's slider repair) and attaching the solenoid's armature to that. A battery door would ideally be integrated into the Maverick's grip, allowing relatively easy battery changes in mid-combat. A sensor would be added to trigger the solenoid when the trigger is released. While this mod is still well within the design stages, I will most certainly document the construction process when I perform this rather involved mod.

You lost me after "Via".

[blastron]

You lost me after "Via".

Hm, perhaps a rephrase, then: Does anyone know approximately how much force it takes to pull back the slider on a Maverick with the stock spring?

[sn1per]

You mean with one of those newton-science lab-force measurement things?

[zaphodB]

Don't solenoids actuate pretty fast? Why not replace the spring with a soloniod?

Why don't you just hang paper clips on a string off of your maverick until it cocks. Then see if your solonoid can lift that much weight? That should be a fairly accurate way of finding out that information. You should probably start with one pound weights, then when you have enough 1lb's to cock it, remove one and start with the paper clips (or something similar) until you can narrow it down to the exact force. Then it's just a few simple calculations and you're done.

[sn1per]

A solenoid is a coil of wire...electric wire is bendy. Therefore, you wouldn't be able to fire. The solenoid would just coil tighter and stay that way.

[blastron]

Don't solenoids actuate pretty fast? Why not replace the spring with a soloniod?

I thought about this, and decided against it for three reasons: 1, because I want to still be able to fire this without a battery, and removing the spring altogether would prevent that; 2, because I would have to make the back of the Maverick longer in order to fit the solenoid; and 3, because I really want the slide to be thrown back during the firing process to make the blaster more handgun-like.

Why don't you just hang paper clips on a string off of your maverick until it cocks. Then see if your solonoid can lift that much weight? That should be a fairly accurate way of finding out that information. You should probably start with one pound weights, then when you have enough 1lb's to cock it, remove one and start with the paper clips (or something similar) until you can narrow it down to the exact force. Then it's just a few simple calculations and you're done.

Ah, thank you, that would work nicely. Now to find some paperclips, string, and a scale! I'll be sure to post approximately how much force it takes to cock the slider, in case anyone else happens to need that information.

A solenoid is a coil of wire...electric wire is bendy. Therefore, you wouldn't be able to fire. The solenoid would just coil tighter and stay that way.

Actually, the solenoid would generate a magnetic field that would push a metal bar forward. The coil itself wouldn't do any physical pushing, so it doesn't matter how bendy it is.

Edit 1:

Rounding up to compensate for errors in measurement (I used a fairly inaccurate bathroom scale, as that's the best my parents' house has to offer), it takes about 50 newtons (or 11 pounds) of force to pull back the slider on my Maverick.

Edit 2:

I apologize for my ignorance, but should I keep using this thread for further questions and updates relating to this mod, or should I create a new thread?

Edited by blastron, 27 December 2007 - 05:57 PM.

[Squishy]

if you DO do this mod, make sure that you cut notches into your maverick so that the plunger can be pulled back and fired at appropriate times.

[Blasphemy]

if you DO do this mod, make sure that you cut notches into your maverick so that the plunger can be pulled back and fired at appropriate times.

Errr... the Maverick plunger doesn't prime that way. It isn't like your standard plunger rod setup, because it doesn't have a plunger rod. The Maverick uses a reverse plunger, it uses nubs to catch. You'd have to somehow create more nubs which I'd imagine wouldn't be too easy.

[Wisey]

I apologize for my ignorance, but should I keep using this thread for further questions and updates relating to this mod, or should I create a new thread?

I'd use the same thread, and if you need to change the name of it you can (I know you can, I just can't remeber how, I think you just edit the first post...).

This mod is going to be very intresting, that is of course IF you manage to pull it off. Acctualy, even if you don't pull it off, it will still be quite intresting. If you do, please post pics and videos =] What size battery(s) are you thinking of useing/going to use? I'm guessing too big to fit in the handle of the Mav itself...?

[Squishy]

if you DO do this mod, make sure that you cut notches into your maverick so that the plunger can be pulled back and fired at appropriate times.

Errr... the Maverick plunger doesn't prime that way. It isn't like your standard plunger rod setup, because it doesn't have a plunger rod. The Maverick uses a reverse plunger, it uses nubs to catch. You'd have to somehow create more nubs which I'd imagine wouldn't be too easy.

you misunderstand. The trigger mech has a hole in it that makes it only able to be fired when the slide is all the way forward. If he wants semi auto, this small modification would allow a faster RoF.

[zaphodB]

The force required may be slightly less than what you measured, because there are two springs at work. The big one is the compression spring that fires the dart. But there is a small expansion(?) spring that pulls the slide back into position during normal use. That could be removed for your purposes, and it would subtract a little bit of force your solonoid needs to apply. 11 lbs is a lot. Good luck.

[sourskttles772]

Hmm. I dont think this is realistic or makes it have any potential gain. With Notches your range will suck. And with converting it to air it just wont be the same.

[CaptainSlug]

Two problems

1. The current load needed to move 11 pounds is really high and this won't lend itself to being friendly to battery power.
2. As far as I'm aware solenoids don't usually travel far enough to be of any use for this application.

[zaphodB]

maybe a step motor?

I dunno. I feel like air pressure would be the best fit, but then why not just make it an air pressure gun.

[M30]

This thread got me thinking...
[I should caveat this with the statement that I'm currently a 2nd year Physics Major, and so "one of those newton-science lab-force measurement things" is kindof my life, day-in, day-out]

Since I started reading up on Nerf guns, I've been frustrated by the lack of uniformity in how spring strengths are communicated. BBB, NF, LS, and so on refer simply to the stock springs that come in their guns. I've even read that a NF Spring to one person is an entirely different thing another! Which is a little silly, if you ask me.

The actual task of rating these springs in a scientific fashion is not that difficult at all. Hooke's law states that F=-k*x, which means that the force (f) is equal to the displacement (x) multiplied by a constant (k) which is an intrinsic property of the spring. This is a pretty simple idea, which means the procedure for determining a Nerf gun's spring constant would be quite easy:

1. Get an object of substantial and known mass. (EG: 10 kg weight)
2. Measure the length of the spring. (li = .1 m)
2. Attach it to the spring, and let it hang down directly.
3. Measure the length of the spring now. (lf = .15 m)
4. Do the math. [Force is determined by the constant acceleration of gravity: F=m*a = (10 kg)*(9.81 m/s2) = 98.1 Newtons. Displacement is simply the difference in lenghts: x=(lf - li) = (.05). Finally, divide: F/x = (98.1)/(.05) = 1962 N/m]

So the spring constant of our example spring is around 2,000 N/m.

Maybe this is excessive, I don't know. I just feel like knowing this data to a more exact degree could be helpful in some way; specifically to perform mods like the one blastron is attempting. People could perform these relatively simple motions on any random spring they decide to stick in a gun and knowing the spring constant would probably clarify a lot of things in terms of troubleshooting new mods.

I'd be willing to begin taking data of this type, if anyone were interested.

That aside, I'd like to hear more details on how this EM-Powered gun will function. It's a really cool idea that could open up a lot more possibilities in the future.

[el swifto]

I don't know if this will help, but This has a bunch of info on springs.

[M30]

Yeah! That's really helpful. I'm not surprised that someone already had the bright idea to take that data, I just wish that more users would follow jhd's lead and take the time to rate their spring replacements.

I don't really expect people to, I can just see situations in which it could be useful information (like the idea suggested by the OP). Blastron, I hope the method I outlined above, and the suggestions of the others is enough to get you the information you need to start this mod.

Let me know if you've got any more questions specifically on the math/physics aspect of this idea.

[blastron]

Alright, I am in need of some help here. After lots of Wikipedia work and some deriving, I came up with the equation (where F is the force, L is the length of the solenoid, μ is the permeability constant of free space, N is the number of turns, and A is the area) to calculate the amount of current needed in order to exert as much force as I want. The units work out nicely, but when I plug in my numbers, I get ridiculously high values for either my number of coils or the current required.

F = 50 newtons
L = 1.75 inches = 0.04445 m
μ = 4π E-7 Henries/meter
A = .0625*π square in. = 0.00012667687 square meters
N and I variable.

The way things are looking now, I will either have to get a very good conductor or wrap a lot of wire in order to get 11 pounds of force over 1.75 inches. I've already looked into linear actuators and other motor-driven solutions, and those are far too expensive for my tastes.

For constructing this solenoid, I was originally intending on using a 7/16" steel rod inside a 1/2" PVC pipe, wrapped with however much wire I needed.

Are my numbers off somewhere?

[M30]

What I get (just running through it quickly, so I make no promises!) is that if you pull the number of turns (N) out of the square root, and multiply it so it's on the left side, you get N*I = a constant, which I calculated to be around 167,000.

Which... yeah, is a lot.

This means that if you have 3-4 amps, which is a lot, and rather dangerous, you still would need almost 42,000 turns of wire. So yeah, these numbers are ridiculous. Forcing relatively weak electromagnetic principals to act on the macroscopic world is a difficult task, so this should come as no surprise.

Your issue of current is also linked to one of voltage, which then begs the question of power.
What, in an ideal world, would you be using to power this?

I think you're better off going with low-current-zillion-turns than high-current-few-turns, but that's just me not wanting you to die of cardiac arrest.

[blastron]

This is likely to involve very large capacitors as an immediate power source, likely charged by 9-volt batteries. As I'm working through this, I'm realizing how impractically heavy this thing might end up being. I'll experiment with winding the solenoids tonight and tomorrow to see if I can come anywhere close to the amount of force necessary without making the solenoid ridiculously huge. I've already looked into things such as linear actuators, and those are slightly too expensive for my tastes. If I can't get anywhere with this, I will likely spend time attempting to design a motor-driven cocking mechanism.

At least there's a lot of room in the Maverick to tuck things away...

[bobafan]

You might want to try a firefly instead because there is more space for electronics and would be more comfortable with larger amounts of weight.

[blastron]

Thanks for the suggestion, but I already have two Mavericks that I'm working with, and would prefer to spend my money on more parts instead of more guns. Plus, the sidearm of choice at my college is the Maverick, so making an awesome Maverick mod would probably get me a bit more geek cred.

[Peter]

If you still want semi auto, you could just use compressed air instead of solenoid.

[blastron]

The trick here is to not use compressed air. Mods that use compressed air already exist, and I want to try something different.