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Homemade flywheel gun


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#1 Dart Slammer

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Posted 03 March 2013 - 04:07 AM

I have recently been working on a homemade (totally homemade, not a single nerf gun part in it) flywheel dart launcher. I have got the basics set up (brushless motors, ESCs, microcontroller etc. on a test rig, but I have been totally stumped on the flywheels! I have tried alloy pullies, but they were off-balance and created way too much vibration. I also tried pieces of polyethylene plastic (cutting board) cut to shape with a hole saw. This was able to be spun up to full speed, but still created a lot of vibration. I loaded 10 streamline darts into a piece of PVC pipe, positioned it in front of the wheels, and blew the darts down it. It fired them all out in about half a second. I tried balancing them (the wheels) with a precision balancer (the type used for balancing model airplane propellers), but the vibration and noise was still pretty awful, and I think It has been damaging the motor bearings.
Anyway, that little rant aside, does anyone have any good ideas for what I could use as flywheels? It would need to be strong enough to be spun at 10,000 RPM, and be well-balanced enough to not start an earthquake.
Any advice would be much appreciated.

The device on the test rig (before I added the flywheels)
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#2 DartSlinger

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Posted 03 March 2013 - 09:59 AM

Try RC car wheels.
This is a really good idea. I have thought about this before, and I came up with this conclusion. There are basically two frontiers of homemades left: usable air guns, and flywheels. Both have their problems though.

Edited by DartSlinger, 03 March 2013 - 10:05 AM.

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#3 481IceDragon

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Posted 03 March 2013 - 12:34 PM

Try RC car wheels.


If they are of a rubber-ish material they will basically burn and leave nasty residue on the blaster,as coop stated in one of his stryfe videos.


But as to replacement flywheels have you tried salvaging hasbros flywheels from a barricade or such? I would assume it would have the same balancing problem though being made of similar materials to the polyethylene plastic you used.
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#4 Dart Slammer

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Posted 03 March 2013 - 03:18 PM

If they are of a rubber-ish material they will basically burn and leave nasty residue on the blaster,as coop stated in one of his stryfe videos.


But as to replacement flywheels have you tried salvaging hasbros flywheels from a barricade or such? I would assume it would have the same balancing problem though being made of similar materials to the polyethylene plastic you used.


Thankyou both for the help. Unfortunately RC car wheels don't work too well as the tires bulge out and explode under the centrifugal force. If the tires are taken off, the rims are oddly-shaped and don't do too well for gripping darts. Modified barricade flywheels would do fine for vibration, but as my motors spin (slightly) slower than barricade motors, it wouldn't have very good range.
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#5 azrael

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Posted 04 March 2013 - 12:01 AM

Can you post a video? Are the motors quiet without flywheels?
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#6 Dart Slammer

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Posted 04 March 2013 - 12:11 AM

Can you post a video? Are the motors quiet without flywheels?

The motors are fairly quiet without the flywheels, the vibration is definitely caused by the wheels.

EDIT:
Videos of sound and firing testing :)

Edited by Dart_Slammer, 04 March 2013 - 06:17 AM.

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#7 DartSlinger

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Posted 04 March 2013 - 12:03 PM

A 3.2 decibel increase isn't that much is it? When people on YouTube put Trustfire batteries into their flywheel blasters, it usually sounds much worse.

You could cut down on vibration by putting some sheet rubber between the motors and the wood. When power tools such as a scroll saw are bolted to a workbench, that's what the owner's manual recommends doing to cut down on vibration and noise.

This prototype is pretty cool. It has some power in it. Posted Image
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#8 Meaker VI

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Posted 04 March 2013 - 12:49 PM

If you're worried about unbalanced wheels messing up the motors, could you add a belt drive between the motors and the wheel? That'd also add some stall protection.
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#9 azrael

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Posted 04 March 2013 - 02:15 PM

A 3.2 decibel increase isn't that much is it? When people on YouTube put Trustfire batteries into their flywheel blasters, it usually sounds much worse.

You could cut down on vibration by putting some sheet rubber between the motors and the wood. When power tools such as a scroll saw are bolted to a workbench, that's what the owner's manual recommends doing to cut down on vibration and noise.

This prototype is pretty cool. It has some power in it. Posted Image

If you look up how the decibel system works, you'll see that a 3dB change is 2x greater than before. So it's pretty loud.

Very interesting work so far, could you give me some info on what motors you selected? You've gotten my interest up enough where I might do some testing of my own, after I finish some robot projects.

I imagine in an enclosed system lined with Dynamat, it might not be as noisy. And I agree, much of your vibrational noise may just be due to your setup.

Edited by azrael, 04 March 2013 - 02:15 PM.

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#10 Dart Slammer

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Posted 04 March 2013 - 03:23 PM

I imagine in an enclosed system lined with Dynamat, it might not be as noisy. And I agree, much of your vibrational noise may just be due to your setup.

While that would reduce how loud it is, my big problem is the vibration damaging the bearings of the motor, even if it is dampened. Already the bearings are starting to feel a bit sloppy.

Very interesting work so far, could you give me some info on what motors you selected?

Hobbyking Donkey 730kv 35A 11.1-14.8v brushless motors. They are a good choice, the only problem seems to be that they use bushings, so I'll probably have to replace them with ball races. For comparison, the Hailfire's motors are (i think) 130 size motors, which run at 6 volts and draw 800ma at stall. So basically the Donkeys are close to 3x the voltage and over 40x the current.
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#11 Dart Slammer

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Posted 04 March 2013 - 03:35 PM

If you're worried about unbalanced wheels messing up the motors, could you add a belt drive between the motors and the wheel? That'd also add some stall protection.


At that speed a belt (or evan a chain) would wear out very quickly. The ESCs have stall, overheat and overlod protection built in.

A 3.2 decibel increase isn't that much is it? When people on YouTube put Trustfire batteries into their flywheel blasters, it usually sounds much worse.


The reason Trustfire'd blasters sound worse is because they might be spinning at 15,000 or 20,000 RPM, where mine is only spinning at 10,000 RPM. The difference is that nerf flywheels are small and light, whereas mine are large and heavy, so an imbalance will exert a lot more force on the bearings due to the increased centrifugaal force of the wheels.

(I haven't quite got the multiquote thing figured out yet :/)
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#12 azrael

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Posted 04 March 2013 - 08:44 PM

Current supply isn't an issue to me. I run 130 sized Tamiya motors, which are drawing probably somewhere like 5-10A at stall, at 4.2V. I use high discharge LiPos, so it's a none issue.
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#13 DartSlinger

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Posted 04 March 2013 - 11:11 PM

(I haven't quite got the multiquote thing figured out yet :/)

To multi-quote, click on the MultiQuote button on each post that you want to quote.
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#14 Dart Slammer

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Posted 20 March 2013 - 01:49 AM

I have been looking into the vibration problems. I am getting new adapters (Precision machined stainless steel), an anti-vibration mount, and I may also be trying new motors that have more solid bearings. I have also decided to reduce the overall speed, as 120+ FPS is too fast for what I intend to use this for (wars with friends, HvZ), as I will be shooting at close range, rather than a NIC war, where everyone has a blaster with a heaver draw than your average compound bow. I think I might go more for a speed like 80-90 FPS, this will still far outperform stock Nerf guns (which get about 50-55 FPS), but it will be safe to use, conserve battery power, and the decreased speed will help counteract the vibration problems.

To anyone who is making something like this, I would advise NOT to use the motors that I did. The type of bearing makes them very susceptible to vibration and vibration damage.

I'll post any updates here, and possibly post a video.
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#15 BuffNerd

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Posted 20 March 2013 - 10:16 AM

I have been looking to do this with two large motors I recived from an old copier that I disassembled. I am unsure of what the voltage should be. If someone could tell me how to find the required voltage I would be very appreciative. Here is a picture.

Posted Image

Thanks for any given help.

Edited by BuffNerd, 20 March 2013 - 10:39 AM.

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#16 DartSlinger

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Posted 20 March 2013 - 12:50 PM

I have been looking to do this with two large motors I recived from an old copier that I disassembled. I am unsure of what the voltage should be. If someone could tell me how to find the required voltage I would be very appreciative.

The white sticker on the side should have all the information needed for wiring, voltage, and current. If it does not, then you can use a power regulator to slowly increase the voltage or current. Here is an informative article about motor diagnostics.
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#17 snickers

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Posted 20 March 2013 - 07:57 PM

I have been looking to do this with two large motors I recived from an old copier that I disassembled. I am unsure of what the voltage should be. If someone could tell me how to find the required voltage I would be very appreciative. Here is a picture.

Posted Image

Thanks for any given help.


You can use any voltage you want. The question is how many volts will these motors run on until they burn out? I would start with 6v and move up to 12v. If you start to smell something burning, don't use that same voltage for extended periods of time.
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#18 BuffNerd

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Posted 20 March 2013 - 09:13 PM

How many volts do you thing I should go up to? I just tried 28v and still no burning smell. Thanks for the help
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#19 snickers

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Posted 20 March 2013 - 09:21 PM

How many volts do you thing I should go up to? I just tried 28v and still no burning smell. Thanks for the help

How fast are they spinning? Faster than a standard flywheel? Keep going until you get your desired RPM. I also don't know the specs of your motors such as the torque and such.

Edited by snickers, 20 March 2013 - 09:21 PM.

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#20 Dart Slammer

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Posted 21 March 2013 - 02:45 AM

I have been looking to do this with two large motors I recived from an old copier that I disassembled. I am unsure of what the voltage should be. If someone could tell me how to find the required voltage I would be very appreciative. Here is a picture.

Posted Image

Thanks for any given help.


They will most likely be low-voltage (maybe 24v) DC motors. They would undoubtedly have the power the spin flywheels. Getting those pullies off the shafts could cause problems though, they are often press-fit on. You might need something like a wheel puller. The thick metal plate on the front would provide an excellent mounting point. There should be some sort of specification plate on them somewhere, maybe those white stickers?

They only problem is they might be lower-than-optimal RPM. You can measure this with a handheld RPM meter. For reference, stock barricade motors spin at 10,700-11,000 RPM. If the motors are too slow, bigger diameter wheels would give them an increased linear velocity.
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#21 Dart Slammer

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Posted 21 March 2013 - 04:15 AM

UPDATE

I have drawn up some concept sketches of how I think the design might go. The ring of pipes you can see will all hold dart tip-to-tail, like a hopper but bigger. This is obviously a very rough sketch, I made it just now.

Posted Image

Posted Image
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#22 Super0dp

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Posted 21 March 2013 - 07:28 AM

UPDATE

I have drawn up some concept sketches of how I think the design might go. The ring of pipes you can see will all hold dart tip-to-tail, like a hopper but bigger. This is obviously a very rough sketch, I made it just now.

Posted Image

Posted Image


Great, you made a PowerStrike 48
I advise you use a magazine instead of a turret like thing, makes reloading easier.
You could cut off the magwell of a recon/retaliator or a rampage to use.

Edited by Super0dp, 21 March 2013 - 07:29 AM.

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#23 BuffNerd

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Posted 21 March 2013 - 08:23 AM

Thanks DartSlinger, snickers, and Dart Slamer. I will probably be using a pully system on the Flywheels.

Dart Slamer, I'm sorry if my questions have taken away from the main topic of this thread.
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#24 Dart Slammer

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Posted 21 March 2013 - 03:19 PM

Great, you made a PowerStrike 48
I advise you use a magazine instead of a turret like thing, makes reloading easier.
You could cut off the magwell of a recon/retaliator or a rampage to use.


It is more like an oversized barricadde than a powerstrike. I thought about mags, but I don't own enough to be practical. Plus a magazine machanism would be more complex and harder to make.
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#25 HasreadCoC

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Posted 21 March 2013 - 04:04 PM

Honestly, it'd be easiest just to use a recon shell with a 36 dart drum mag (they're not that expensive; you could get one for probably $10 or less). If the 50 dart drum mag ever came/comes out, that'd work even better.
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