47 replies to this topic

[azrael]

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.

a BJT is a transistor. A relay can work too, that's a pretty good idea.

[Crater]

What's a BJT?

Bipolar junction transistor, the most basic (as far as I know) type of transistor.

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.

Why would you use a BJT instead of a MOSFET? I thought MOSFETs were more popular for this kind of thing. (MOSFET = metal oxide semiconductor field effect transistor)

[0reo]

Any advantage of a MOSFET over a relay?

On another note, anyone considered replacing the mechanical trigger mechanism with a solenoid and then using a circuit to effect select-fire capability?

[azrael]

well, I've used BJTs (specifically in a Darlington configuration) before switching, they're cheaper and pretty simple to set up. Technically faster at switching usually, because of the FET gate capacitance.
I've had better experience with current handling too. Something with the capacitance in the MOSFET gate...

Either one could be used.

[Ivan S]

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.

Would something like this work?

I understand that brushless motors are more efficient than standard ones, but what advantages would they have in a flywheel gun? More torque, therefore less downspin from firing?

Edit: I now realize that these are only 10k rpm, half the speed of the mod here. So I guess they wouldn't work? Or could torque make up for it? I really don't know much about flywheel guns.

Edited by Ivan S, 28 January 2013 - 03:36 AM.

[0reo]

Brushless motors come in all sizes and specs too. I've got a pair for a ducted fan RC airplane that will do 70krpm. But you can get them in an "out-runner" style and my thought was to let the motor body spin as the flywheel itself. This would allow for MUCH more torque, and fw mass, as well as high rpm. But of course the build would require massive reconstruction of the gun internals. Might be better of constructing from scratch. It'd be an expensive build too.

[azrael]

Would something like this work?

I understand that brushless motors are more efficient than standard ones, but what advantages would they have in a flywheel gun? More torque, therefore less downspin from firing?

Edit: I now realize that these are only 10k rpm, half the speed of the mod here. So I guess they wouldn't work? Or could torque make up for it? I really don't know much about flywheel guns.

Actually, because the 25k RPM spec is taken at 2.4V, my motors should be running at around 40k RPM since I use 4.2V.

[0reo]

Just received the AtomicMods Stock R Evolution motors. WOWZA! You can't stall these motors by pinching the motor shaft with your fingers. I tried. Got burns on my finger tips! Unfortunately it doesn't look good for me getting these installed today. Too much important stuff to do.

On a side note, if I decide to not use them in the Stryfe they'll make great motors for a hand-held rotary tool. Think dremel but less bulky.

[0reo]

Another thought- wonder if there's room to swap out the trigger mechanics and replace with a solenoid that would push the dart into the flywheels. Then the gun could be made select-fire. Hell, you could even do a 3rd burst mode.

Use the edit feature to avoid talking to yourself sequentially.

Edited by Zorn's Lemma, 28 January 2013 - 11:19 PM.

[Crater]

Brushless motors come in all sizes and specs too. I've got a pair for a ducted fan RC airplane that will do 70krpm. But you can get them in an "out-runner" style and my thought was to let the motor body spin as the flywheel itself. This would allow for MUCH more torque, and fw mass, as well as high rpm. But of course the build would require massive reconstruction of the gun internals. Might be better of constructing from scratch. It'd be an expensive build too.

Some laser printers use brushless outrunner motors. I don't know how fast they spin, but they are large and look powerful. To get some, go to your electronics recycling center and disassemble some large laser printers. All of the ones I've seen come with integrated drivers, and are designed for 24 V. Here's a video in which one is connected to a separate driver and presumably driven at a much higher voltage.
http://www.youtube.com/watch?v=v_Cx1eTP_8w

[0reo]

I don't have that kinda time. They make all kinds of brushless motors for RC Aircraft. I'd just find one with the right specs and buy it off the shelf. Then again, I'm not taking on that project at all because I don't have the time.

[Coop]

I just got finished installing the Hyper Dash motors into my Stryfe. I must say, I like the stock motors more. The RPM is significantly higher on a much lower voltage with the Hyper Dash motors, but they seem to lack torque to a point where it's annoying. Waiting in between shots for a second or two is just not worth the slightly higher range they were allowing. The motors seemed to nearly die every time a dart traveled through the fly wheels.

Although, temporarily running these motors on a higher voltage was pretty crazy. I thought my shell was going to fly apart during some of my tests.

[azrael]

I just got finished installing the Hyper Dash motors into my Stryfe. I must say, I like the stock motors more. The RPM is significantly higher on a much lower voltage with the Hyper Dash motors, but they seem to lack torque to a point where it's annoying. Waiting in between shots for a second or two is just not worth the slightly higher range they were allowing. The motors seemed to nearly die every time a dart traveled through the fly wheels.

Although, temporarily running these motors on a higher voltage was pretty crazy. I thought my shell was going to fly apart during some of my tests.

What battery are you running it off of? You can't just run them off Trustfires. The Tamiyas have a large stall current draw, and a fairly large constant current draw - Trustfires can't supply enough current, that was the whole point of my mod haha. I'm only running it at 4.2V, off a Li-Po that can deliver 25A of continuous current, and even more in bursts. Also, they're supposed to be run off a max of 4.5V.

I experience no wait in between shots. I'll try to take a video this weekend.

Edited by azrael, 31 January 2013 - 05:22 PM.

[0reo]

I agree. It could be the current draw. However, part of the trade-off of designing an ultra-high rpm motor is that the torque curve suffers. So it might be both.

I think I'll be able to get my AtomicMods motors installed tomorrow. I may have the same problem with the batteries not being able to keep up. We'll see.

[Coop]

What battery are you running it off of? You can't just run them off Trustfires. The Tamiyas have a large stall current draw, and a fairly large constant current draw - Trustfires can't supply enough current, that was the whole point of my mod haha. I'm only running it at 4.2V, off a Li-Po that can deliver 25A of continuous current, and even more in bursts. Also, they're supposed to be run off a max of 4.5V.

I experience no wait in between shots. I'll try to take a video this weekend.

I tested alkalines, UltraFires, NiMH battery packs, and a 15c constant/25c peak discharge (1200 mAh) lipo pack with the same results. The lipo resulted in the shortest rev up time, but the motors still seemed like they were complaining every time a dart was shot. After 3 or 4 rapid fire shots, the motors sounded like they were at less than half of their normal RPM, which led to a stream of darts traveling shorter and shorter distances.

I'm not suggesting a motor replacement is a bad idea. I just think these motors are not ideal for our use.

Edited by Coop, 03 February 2013 - 03:44 PM.

[azrael]

well, there is something you are doing differently.
my Stryfe is very consistent, recovery time didn't seem any different than stock.

I'll record something tomorrow.

[Coop]

well, there is something you are doing differently.
my Stryfe is very consistent, recovery time didn't seem any different than stock.

I'll record something tomorrow.

If you're comparing it to stock, then sure they do fine. I'm comparing to "over volting" the stock motors with four UltraFires. Xellah and I ran four UltraFires/Trustfires for a 4 hour war and didn't seem to damage the motors at all. Using that set up allows for ridiculously fast follow up shots without the motors getting bogged down.

[azrael]

I don't have the battery on me, and I only tested the stock setup for a few seconds before modding so I don't have a good frame of reference.

I definitely just don't describe my Stryfe as "bogged down" in the very least.

[Crater]

a 15c constant/25c peak discharge lipo pack

The discharge rate (C number) means nothing without the capacity.

[azrael]

Here's a quick test I took. Just mostly to show the recovery time.

http://youtu.be/HQnS0wkgEA4

Range is actually closer to 60-70 feet, using elites and modified streamlines (chopped stem and covered hole on the tip).

Here's a pic of the spread.


unrelated, also I put a shotgun grip on my Recon ;D

Edited by azrael, 04 February 2013 - 12:03 AM.

[azrael]

I put some Mach Dash Pros in my Stryfe. I like these a lot better. Only 3 bucks, too!
Almost no heat generated in the bushings. I can't feel any, TBH.
Current draw is a bit greater, haven't measured yet.
Range is at least 10 feet greater than before.

Mach Dash Pros are double axle motors, so you'll have to cut one side down. The RPM is higher, and I'd like to think torque is higher since it was designed to be a double axle motor haha.

Edited by azrael, 24 February 2013 - 09:06 PM.

[xXhunter47Xx]

Sorry for the necro, but I would like to know if 3 AA nimh batteries would provide enough current to run the motors. I'm planning on putting these in my rapidstrike.

[azrael]

Sorry for the necro, but I would like to know if 3 AA nimh batteries would provide enough current to run the motors. I'm planning on putting these in my rapidstrike.

No idea, It's very hard to find discharge rates on NiMH batteries. The mod on the nerf reddit has done it using eneloops, and the spin up time isn't great. Try using 6 - 3 in series paralleled with another 3 in series.