TLDR - Amazon had a sale last week, and I picked up a new Mega Mastodon. I replaced all three motors with Hellcats, and now it doesn't work because the pusher motor is too fast.
The Mastodon requires 6 D batteries. How am I supposed to indulge my megalomaniacal fantasies of world domination when I'm being held back by the bulk of a bunch of D batteries? It's just not fair.
I never actually installed D batteries. In fact, I don't even own any D batteries. Instead, as soon as my Mastodon showed up, I took it straight to my laboratory to be dissected. The stock motors are wider than Hellcats and similar in length, so I decided that all 3 motors would need to be upgraded. To make Hellcats fit in holes that are too large, all I needed to do is make a few adapters.
I also traced the wires. The Mastodon contains 2 safety switches and 3 functional switches: the dart check, the jam door lock, the acceleration trigger, the main trigger, and the pusher switch. Once the dart pusher starts to extend, the pusher switch forces the pusher motor to keep running until the cycle is complete and the pusher is retracted.
Rather than try to replace the 3 functional switches with high-current versions, I decided to add 2 relays. The result? This mod includes more sins than I care to confess.
Much to my dismay, the Hellcat pusher motor is too fast for the rest of the blaster. When I press the trigger, the blaster fires one dart and then the drum fails to turn. When I release the trigger (but not the acceleration), the pusher fails to stop firing. I strongly suspect the problem is that the pusher is not retracting fast enough. Since the pusher uses a return spring to retract, I could try upgrading this return spring, but then I might have to upgrade the thin rubber shock absorber at the back of the gearbox.
Now that I have cut the original motor mount and added an adapter, I cannot easily go back to the stock pusher motor. I could try to replace it with a slower 180-size 12V motor. Another possibility would be to make the pusher motor run slower by supplying it with a lower voltage.
It looks like my fantasies of world domination will have to wait another day.
- NerfHaven
- → Viewing Profile: Topics: oddron
oddron
Member Since 31 Jul 2016Offline Last Active Private
Community Stats
- Group Members
- Active Posts 12
- Profile Views 3,564
- Member Title Member
- Age Age Unknown
- Birthday Birthday Unknown
User Tools
Latest Visitors
Topics I've Started
Modifying a Mega Mastodon
14 August 2016 - 10:46 PM
Stryfe Mod - 3D Printed FWC
07 August 2016 - 01:12 AM
I wanted to modify my Stryfe, but I didn't want to wait to order a FWC, so I decided to make my own. I tested this in the superstock rounds at APOC.
In testing, I noticed that my darts have a tendency to curve or even whirlybird. I also lost one dart when the head was ripped off, leaving the remainder to jam the blaster. I am going to add a guide to help center the darts as they enter the FWC.
As for the rest of the blaster, I used a relay to run the motors, and I used copious amounts of duct tape to hold the wiring. The relay coil is controlled by the stock trigger switch.
I was advised to replace that relay with a transistor and internalize my wiring. The puzzle is finding a transistor that won't require a heat sink, and I think I have a solution. After I test my blaster with a transistor, I'll post an update.
I am currently looking at the AUIRFB8409 in a TO-220 package, which has an internal on-resistance of just 1.3 mΩ.
http://www.mouser.co...g4noEfhEQ3IYw==
The TO-220 package, with no heat sink, has a thermal resistance of 62.5°C/W.
To be paranoid, I'll calculate the temperature at 48 A continuous. My stryfe has 2 hellcat motors, and their stall current is 24 A each. At 48 A, this MOSFET will generate 3 W of heat.
With no heat sink, 3 W will make the transistor 187.5°C warmer than the surrounding air. If the surrounding air (inside the blaster) is 30°C, then the transistor will heat up to 217.5°C. Not surprisingly, it will burn out at this temperture. In other words, if the flywheels are completely jammed, and I hold the trigger anyway, then the transistor will burn out.
Realistically, I'm only drawing 48 A momentarily when I start the motors, so the transistor will not get as hot as my calculation would suggest. To calculate how hot, I would need to know how long is "momentarily" and I would need the thermal mass of the transistor. Alternatively, I could just test it and find out.
Finally, MOSFETs can be safely operated in parallel, and parallel configurations are regularly used in power supplies to produce higher output current. Sticking with my paranoid scenario of 48 A, I could use two MOSFETs in parallel. If they're perfectly balanced, each one would generate 0.75 W of heat and become 47°C warmer than the surrounding air. The on-resistance of a MOSFET increases as it warm up. After accounting for this fact, the transistors will reach 91°C each, which is well below their burn-out temperature of 175°C. Even if the motors burn out, as long as they don't short out, a parallel pair of transistors would survive.
- NerfHaven
- → Viewing Profile: Topics: oddron
- Terms of Service and Privacy Policy
- Code of Conduct ·