47 replies to this topic

[azrael]

This is a quick run through of what I did to a Stryfe I picked up yesterday.
I don't think this is something everyone should do, as technically, what I did is dangerous. There are safer ways to do this, but I was lazy. I'll elaborate later in the post. As electrical engineers, we know what we're doing. mostly, haha.
This is not a tutorial, and this is not in depth. We did this rather on the fly, and will be doing the same process later this week with a Rayven.

What we used:
18 gauge wire, red and black
Plasti-dip spray paint
Hakko FX-888 soldering iron
lead free solder (harder to use, but the fact that it melts at higher temperatures is better for our purposes here)
Tamiya Hyper Dash motors
8.2V LiPo Battery and connectors

I wanted to mess around with an electronic blaster, as opposed to air powered and plunger type ones for a change. A friend of mine got the new Elite edition of the Rayven, so I picked up the Stryfe.
He happened to have some Tamiya Hyper Dash motors lying around from a quad copter project, so we decided on a whim to put them in:


Notice there are no caps on these motors, as on stock ones. They're not necessary, since there is no signal here. We don't care about their effect in a system like this. Just wanted to point that out.

I have read someone tried Tamiya motors in a Rayven before without success. To that guy, I say, "wat a nub". I remembered reading that he kept overvolting it to get the motors started, and even then it didn't work well.
That's not how to use Tamiya motors. They run at a maximum of 4.5V, but draw a lot more current. So that would be one Trustfire in this case - 3.7V. Not good enough - it can't supply nearly enough current. I'll explain my approach later.
Notice I also left the Thermistors out. Why? These motors run hot! Those thermistors will be doing their job too well. Plus we KNOW we're running at a safe voltage here, so there's no chance of burning them out.

Also, I use teflon insulated wire, in this pic, should be able to handle the higher current demands with no problem.
I remembered a cool trick Coop did to his flywheels on his Stryfe, namely painting them with Plasti-dip. Great idea! I just put one coat on, but will be adding more later.

About to reassemble here...

You'll notice I left the locks in. I ended up taking out the jam door electronic lock, but that's it.
To explain, leaving the locks in prevents many possible problems with the motors stalling or jamming - which is something we don't want to do. Motors draw a significantly greater amount of current when starting up or stalling.
Looks like I took this picture before I replaced the wiring...I only brought one color of Teflon insulated wire with me, so I replaced the red and black wires with 18 gauge wire appropriately colored, which will be safer to run all that current through them.

I popped out the orange wall thingies in the battery drawer:

and shaved off the blue divider, too:

Notice the connector. Yep, that's a lithium polymer battery connection. That's how I'll be powering this thing! Way more current supply on tap, way more efficient.
Here it is charging:

We are charging it so that both cells are the same voltage. Why? Because we are going to take it apart! this battery is an 8.2V cell. We need 4.2V.
So we're going to disconnect the cells, and put them in parallel for higher current supply.
This is the extremely dangerous part I referred to. We are charging them first so they are balanced, so we don't want any crazy voltage offset sparking when we do connect them. These discharge can a lot of current, so don't lick them or let them short circuit. YOU WILL DIE. srs bsns.
Here's a picture as we pull it apart:

Connected in series, see?
We're going to connect the positive terminals together, and the negative terminals together. This will give us 4.2V.
Now, I said there was a safer way...They do make one cell LiPos. We just didn't have any, and we didn't feel like ordering them.
I won't go over the exact process because it's not safe for the average nerfer to try. So I didn't want people duplicating it.

Everything back together:



Results?
We don't have actual measurements, but I would say around 80-90 feet.
Comparable to a overvolted Rayven, but here's the best part: at almost less than half the noise!

Hopefully get a video in this week, when we get our proper one cell LiPos in the mail....and our Tamiya Plasma Dashes! Even faster RPM woo!
I will also be installing Dynamat dampening material in it to see how much that helps.

So what did this accomplish?
Hopefully a different approach than just sticking Ultrafires in a blaster.
Put really nice motors in a blaster.
Quieter than overvolting.

EDIT: For people reading this, I no longer use this battery, because it's silly dangerous haha, and also I'm now using Mach Dash Pro motors, which have higher RPM and a more torque than Hyper Dashes. Less current draw than Plasma Dashes, which run far too hot to be useful in this purpose. They might work if you use lead free solder, I guess. The Mach Dashes are almost as fast, though.

Edited by azrael, 19 June 2013 - 09:00 AM.

[Nerfmodderdude]

Wow! Great job on the write up. :-D I have been thinking about doing this with Tamiya Plasma Dash motors. How many amps are you pulling? Also what are the ranges? How many C is that battery rated for?

[azrael]

Based on the battery's label, and paralleling it, I'd say, 40A continuous, 80A burst.

Also gonna put a mini voltmeter in there so I don't run it below 3.7v.

[DartSlinger]

Also what are the ranges?

We don't have actual measurements, but I would say around 80-90 feet.

Also, do extremely fast flywheels such as these have any adverse effects on darts?

[azrael]

I haven't noticed any dart wear, but I haven't done too much testing yet.

I got this mostly because I thought this would pair well with my 35 dart drums. So I've fired them off a couple of times through.



I'll get current readings tomorrow maybe, tonight I'm getting silly drunk.

Edited by azrael, 21 January 2013 - 10:18 PM.

[Jeo]

16v Stryfe on stock motors is starting to melt darts.

[azrael]

16v Stryfe on stock motors is starting to melt darts.

Whoa. I certainly haven't seen that.

My friend has noticed scuff marks on the tips of his overvolted Rayven, though.

[TheWiredDJ]

If you don't mind me asking, what are the specs on the single cell LiPo you ordered? I'd assume it would have to be ~4100mah to keep up with Plasma Dash motors.

Edited by TheWiredDJ, 22 January 2013 - 04:08 PM.

[azrael]

If you don't mind me asking, what are the specs on the single cell LiPo you ordered? I'd assume it would have to be ~4100mah to keep up with Plasma Dash motors.

6000mAh

I'm thinking people are melting darts because the flywheels aren't gripping them well, so the darts end up being rubbed the wheel several times before being pulled forward correctly.
The Plasti-dip is what works against this, making it more efficient, and this is why I haven't melted any darts.

As far as why it's quieter, I think it's the quality of the motors. They're probably more balanced.

[0reo]

Be careful your flywheels don't come apart at those high RPMs. Probably not too much to worry about while the blaster is assembled but when you have it apart on the work bench testing remember to wear eye protection just in case.

[azrael]

Be careful your flywheels don't come apart at those high RPMs. Probably not too much to worry about while the blaster is assembled but when you have it apart on the work bench testing remember to wear eye protection just in case.

they snap on, I don't think there's much risk.

[Crater]

I don't see how snapping on is going to save you.

Edited by Zorn's Lemma, 24 January 2013 - 01:12 PM.

[azrael]

I think you guys being a bit ridiculous, I'm never turning on the motors when the gun is open. Why would I? And I initially understood "come apart" to meant come off the motor, that's why I responded like I did. In any case, I'm pretty sure there will be no issue.

Right now at 19000 RPM, they're fine, not in any danger of exploding like that. Shouldn't be a problem at 25000, the same motors have been used to spin plastic propellers just fine. the diameter is also much smaller than a CD, and the edges of the flywheel are stronger since there's an outer lip.

That CD exploded because it's not meant to be run faster than 10000 RPM or something like, whatever 52x read speed is. Plus it's using what, a vacuum motor? It's gonna vibrate like hell, because it's not meant to be spinning a disk like that.
You've brought up a ridiculous comparison, I think.

Edited by azrael, 24 January 2013 - 09:50 AM.

[ice]

How much where the motors?

[azrael]

The Hyper Dash 2s were something he had lying around, so I'm not sure.
The Plasma Dashes I ordered were 10.50 each.

[0reo]

Its low risk, sure. But at 40,000-60,000+ RPM that some of these racing motors spin at its definitely possible for someone to have an anomalous weak flywheel disintegrate at speed. Low risk but high penalty. It only takes a pair of safety glases to protect your eyes if you're bench-testing.

The Tamiya Dash series of motors run $15-$20 shipped. There's a very good $5 alternative that I'm going to post about in a few days. I'm also going to test some $40ea AtomicMods motors just for giggles. I'm currently trying to decide whether torque or speed is more important for our application. If it is speed then the Plasma Dash motor is probably as good as its going to get, but I'm leaning towards torque being more important and these boutique slot-car motor manufacturers don't publish very good performance data so its a little tricky selecting the right motor.

After a while crocodile.

[azrael]

Its low risk, sure. But at 40,000-60,000+ RPM that some of these racing motors spin at its definitely possible for someone to have an anomalous weak flywheel disintegrate at speed. Low risk but high penalty. It only takes a pair of safety glases to protect your eyes if you're bench-testing.

The Tamiya Dash series of motors run $15-$20 shipped. There's a very good $5 alternative that I'm going to post about in a few days. I'm also going to test some $40ea AtomicMods motors just for giggles. I'm currently trying to decide whether torque or speed is more important for our application. If it is speed then the Plasma Dash motor is probably as good as its going to get, but I'm leaning towards torque being more important and these boutique slot-car motor manufacturers don't publish very good performance data so its a little tricky selecting the right motor.

After a while crocodile.

The Plasma Dash is rated for 25000 RPM, 29k without a load. Nothing insaaaaane, IMO.
EDIT: Just looked up the AtomicMods you mentioned, definitely take care with those!

What's a good amount of torque, in your opinion?

The Hyper Dash 2s in mine now have no trouble gripping and flinging darts, I believe they have 10 grams per cm.
The Plasma Dash has 20 grams per cm.

The Plasma Dash is probably the priciest one, it's not hard to get it for less than 11 dollars each if you look. I just used Google. Shipping was like 5 bucks altogether for 4 motors.

Edited by azrael, 24 January 2013 - 06:57 PM.

[0reo]

I don't think its possible to get enough torque out of a 130 size motor to keep the flywheel speed up while firing a dart. The best we can do is reduce the problem. If you listen carefully you can hear it even on my "high-torque" robotics motors. The moment the dart head contacts the flywheels the RPMs take a massive dump and have to spin back up after. It happens fast, and definitely faster then with the OE motors but its still audible.

Also, do the math. The flywheels are approximately 4" in circumference. Multiply (RPMs X 4" X 60sec)/12" and you get your theoretical dart speed. My darts shoot≈90ft ptg and leave the gun going 100fps (measured with a balistics chronograph.) That calculates to 17,000rpm. My motors are 25,000rpm. You can't make real use of those high RPMs unless the motor has the torque to maintain that speed under load. That tells me the only thing these high RPMs are doing is storing inertial energy in the flywheels, which does help but not enough (hence the drop in RPMs.) I suppose there's an argument to be made for adding mass to the flywheels as long as the post-shot re-spin-up isn't too slow but more torque helps there too.

Someone please be my hero and convert their blaster to larger diameter brushless motors. It would require major reconstructive surgery on the blaster but the results would be in a whole 'nother universe.

After a while crocigator

(Edited to correct my mathematical blunder as I posted about below.)

Edited by 0reo, 26 January 2013 - 02:36 PM.

[azrael]

I don't think its possible to get enough torque out of a 130 size motor to keep the flywheel speed up while firing a dart. The best we can do is reduce the problem. If you listen carefully you can hear it even on my "high-torque" robotics motors. The moment the dart head contacts the flywheels the RPMs take a massive dump and have to spin back up after. It happens fast, and definitely faster then with the OE motors but its still audible.

Also, do the math. The flywheels are approximately 4" in circumference. Multiply (RPMs X 4")/12" and you get your theoretical dart speed. My darts shoot≈90ft ptg and leave the gun going 100fps (measured with a balistics chronograph.) That calculates to 300rpm. My motors are 25,000rpm. The problem is obvious. That tells me I don't even need 1000rpm free-running speed if I can get a motor strong enough to pass a dart without losing more then 50% of its speed. The only thing these high RPMs are doing is storing inertial energy in the flywheels, which does help but not enough. I suppose there's an argument to be made for adding mass to the flywheels as long as the post-shot re-spin-up isn't too slow.

Someone please be my hero and convert their blaster to larger diameter brushless motors. It would require major reconstructive surgery on the blaster but the results would be in a whole 'nother universe.

After a while crocigator

surely you don't need much torque to toss a dart that only weighs 50 grams?

Can you explain your math? I'm not following where you derived that from... It definitely seems like an oversimplified model to follow.

One thing that your analysis doesn't explain is that dart speed remains pretty constant with rapid fire shots for me. If it was losing that much energy I would think it be apparent after a shot. I'm pretty sure these motors have plenty of torque for our purposes.

Edited by azrael, 25 January 2013 - 10:44 AM.

[infamous]

I am the guy who was doing the mods with azrael.

Oreo has a few good points.

However, the gain of the kinetic friction coefficient from a reduced relative speed difference of the flywheel and bullet is not enough to justify the trade-off of having a lower flywheel speed. This is because at these speed differences, the kinetic friction coefficient is approximately constant.

The 300 rpm is a idealization that can never be achieved. First, nothing in the world has perfect grip. Even if your static friction coefficient is 1, your maximum grip force is only as much as the bullet's force on the flywheel. So unless you construct a mechanical grip system (which will involve making custom bullets probably with slots in them for the flywheels to grab), this concept is pointless.

Nevertheless, torque is still an important figure. Not to determine the speed of the exiting bullet, but rather to determine the rate of fire as you need to replenish the flywheel speed as fast as possible for optimal performance.

I did notice a relatively slower recovery time with the hyperdash2s than my 3s (12.6V) over-voltaged stock rayven (with stock motors). But with the plasmadashs' double torque gain, it should be enough to match that of the stock rayven, which is quite high even for "war" applications.

The most ideal flywheel design using stock streamlines is probably a brush-less motor driving very heavy flywheels. Although you can argue that heavy flywheels will reduce recovery time, you also have to consider that heavier flywheels will also mean a relatively less loss in speed from the flywheel to bullet momentum transfer. So yes, it will take longer to spin-up overall. But you loss less speed from bullet fires and thus, need less time to recovery back to original RPM.

All of this "over-engineering" is pretty pointless for this gun in my opinion. No matter what you do, how fast the bullet is, how far the range is, the accuracy will be complete crap due to the nature of the design. This is just a nice side weapon to have for close combat as the rate of fire is much faster than a conventional cock mechanism.

If you feel like it, throw on some nice 130 motors and plasti-dip the flywheels. Otherwise, just over-volt the stock gun with some nice lipos and call it a day. Just don't be a noob and use trustfires as they are severely limited by output current. Put it this way, people use 16.8 V trustfires without triggering the stock therm-resists. My 12.6 V lipos triggered them after 10 seconds of firing... If anything at least parallel your trustfires to pump the correct current. Over-voltaging to compensate for current limitation is terrible design and engineering.

Edited by infamous, 25 January 2013 - 05:44 PM.

[0reo]

Ok, I have to confess to a mathematical error. In my formula to calculate RPMs and Dart Velocity I forgot to convert RPMs to rounds per second which means my calculated RPMs were off by a factor of 60. My general premise that torque is limiting, not RPMs still stands.

Redoing the math:

FPS = RPM x C / 60
FPS = Dart muzzle velocity
RPM = Flywheel rounds per minute
C = Circumference of flywheel
So 100fps x 60seconds/min x 12inches/ft / 4.131" = RPM = 17,429

Does that make better sense?

So, 17k RPMs is still a big drop from the ≈25krpm free-running speed of my motors.

The blue darts only weigh one gram give or take 10%, not fifty. But I don't think it's the propelling of the dart that takes so much torque as it is the squishing of the rubber dart tip between the flywheels. Have you ever tried to push a dart through by hand? It takes a bit of force. Have you ever held a 10g or 20g weight in your hand? Its not much and the motor torque spec is only at one cm from the motor shaft. The flywheels are actually 1.67cm radius so if your motor puts out 20g-cm of torque you're only seeing 12g at the flywheel surface. Double it for two motors but its still not much.

I think that squishing provides enough pressure and friction between the flywheel and the dart tip to keep slipping at a minimum. I could be wrong but that's my take: slipping isn't a problem and plastidipping the flywheels is unnecessary. Maybe even detrimental, to the extent that the plastidip coating thickness has to squish the dart tip that much more to pass the dart, and it probably unbalances the flywheels a little which makes more noise and is harder in the motor.

As for consistent shot-to-shot performance, these motors can get from 15krpm back to full speed faster then you can pull the trigger.

After a while allodile.

[infamous]

Sure but that's only the acceleration from torque. You also have to consider acceleration from momentum transfer between the flywheel and dart. And guess what? Faster flywheel = more momentum = more acceleration. The point of the flywheel system is to store energy by "charging up" the system with flywheels and releasing it rapidly to the dart. This released power is much greater than the power rate that charges up the system. By prioritizing torque as oppose to RPM, you are defeating the purpose of the design.

Obviously there is a trade-off on how fast RPM you should achieve (without considering available motor options). The answer is: you should get motors that can go as fast as possible (RPM) that will also recover at a rate you want (because the faster RPM, the slower the recovery speed).

Also I highly doubt that you will find any better 130 motors besides Tamiya ones... Even with their RPM specced motors, they will probably still have higher baseline torque figures than anything else of that size (their magnets are insane).

[0reo]

The inertial energy is negligible. The flywheels don't have enough mass to store that kind of energy. The dart can only exit at the same speed as the flywheels retain. That there is such a large drop in RPMs when a dart is passed means that the motors lack sufficient torque to maintain their speed, even with whatever inertial assistance they get.

Try this: on a blaster with locks removed spin up the flywheels and then cut power to the motors a split second before firing a dart with the trigger. If the inertial energy matters the dart will still fire. If the dart doesn't fire or only goes a few feet then the vast majority of energy imparted in the darts comes directly from motor torque. I bet you jam the gun.

I'm not saying a faster motor does no good. It does good. But once you're in the 20krpm range you stand to benefit a great deal more from additional torque then you do additional no-load motor speed.

Edited by 0reo, 25 January 2013 - 08:46 PM.

[azrael]

Quick update.
We tried the Plasma Dashes, and got some Dynamat.

The Plasma Dashes draw too much current, and since our batteries can actually supply the current they need, the momentary switches in the acceleration trigger switch fry. I would guess they are only rated for 2A of continuous current, which is what the current draw of the Hyper Dash 2s just clocks under. According to my multimeter, they have a continuous current draw of 1.8A.

Plasma Dashes easily draw twice that, and their stall current is even greater than that.

Hah, totally forgot about checking the current rating for the switches. So that's the limiting factor.
The system can totally work, if you want to do a work around. You can either get higher rated switches, which are usually significantly bigger or the other idea we had. We were thinking about using the stock switches to actuate a BJT to do the switching. However, the BJT will still be dissipating a good amount of heat, so it will need to properly rated and heatsinked as well.
All in all, the Plasma Dashes run really hot, to the point where continuous fire is not too sustainable.

I ended up putting back in the Hyper Dash 2s, and infamous used some Torque Tuned Tamiyas we had lying around. The Torque tuned feature 14g per cm, compared to the Hyper Dash 2's 10g per cm, but have a lower RPM.

We are considering getting Mach Dashes, which have 20g per cm, and still have a high RPM. These have almost half the current draw of the Plasma Dashes, but a bit more than the Hyper Dash 2s.





I installed a voltmeter, which is hooked up the acceleration trigger, so I know how much of the battery is drained.
You can see the Dynamat lining. It does work, and it does help. My gun is quieter than before, all vibration has stopped. There is still noise of course, but it's only from the motors. Pretty cool.
I also redid all my wiring with teflon insulated wire.

It's worth noting that while the Dynamat helps in the Rayven infamous owns, since the flywheel enclosure isn't bolted, there's a lot more rattling than in a Stryfe.

Edited by azrael, 27 January 2013 - 05:40 PM.

[0reo]

Good idea on the dynamat. I like that idea.

I was thinking the same thing about those switches the other day. What's a BJT? You could use a relay and there's probably one that will handle the current and fit in the gun easy enough. Looks like I'm gonna have to hit the local electronics geek-shop tomorrow for one. My AtomicMods motors are coming tomorrow and they too draw a lot of current. My hope is that the Eneloop AAs will deliver the current so I don't have to resort to exotic batteries. I've heard of Eneloops delivering 4A without too much voltage drop. Guess I'm gonna find out.

After that I guess I'm gonna have to see about redesigning these darts because I'll be satisfied that at 40krpm and 50g-cm of torque (both motors combined) I've come as far as is reasonable and a little beyond with modifying the gun. The darts still leave much to be desired.