HOWTO Wiki Fuse Mod with Resistor

From Heli-Wiki

This modification will help protect the 3n1 (or 4n1) from current spikes caused mostly from motors that decide to die. This will be a precursor to the dual tail motor modification that will be coming in the future. Many of the ideas for this project came from the bladecprepair.com forums and especially from user Vector57. Thank you everyone!

Contents 1 Parts List 2 Introduction 3 Procedure 4 About Me

Parts List

• 20 AWG red wire (optional)
• 20 AWG black wire (optional)
• 26 AWG red wire
• 26 AWG black wire
• 4 female spade connectors for use with 20-22 AWG wire
• 1 2Ohm 2W resistor
• 1 10A fuse (like for use in an automobile [not sure of the exact name])
• 1 4A fuse (like for use in an automobile [not sure of the exact name])
• 2 2-pin molexplugs
• 4 Female pins for the plugs
• Various sizes of heatshrink tubing

Introduction

I started this modification by looking at the power wires that go to the main and tail motors. I could tell that they are very small in size, but wasn't exactly sure what size when I bought the rolls of 20AWG wire. After comparing the sizes and seeing that 20AWG wire is much larger than the stock (26AWG) wire, I decided to replace all motor power wires instead of splicing 20AWG and 26AWG together. This worked out great until I found out that 20AWG wire was definitely not going to slide down the tail boom, but we'll get to that. In very basic terms, I am going to change hte circuit from going directly from the 3n1 to the motors, to fusing the RED wire for each motor. The black wire needs only to go from the 3n1 directly to each motor.

Procedure

• The first step is to prepare our spade connectors. The spade connectors that I used were fully insulated, so I used a small pair of clippers and twisted the connctors inside to cut off the insulation where I wanted to solder the connection together. Here is a before and after shot of what I'm talking about.

Here is another picture that might help

• I did this 4 times, one for each spade connector, that will eventually hold the fuses.

• After the spade connectors were prepared, I decided to solder the resistor directly to one of them which will eventually lead to the tail motor. It came out nice after shrink tubing it all up.

• At first, I planned on placing the fuses right on top of the 3n1 and receiver, but I urge against this. They did not fit when all was done and I had to move them.

• In the above configuration, I cut my wires in an attempt to fit them nicely here. Luckily, when I had to move them later on due to the canopy not fitting, it was not a big deal.

• This is where I decided to use 20 AWG wire for power to the motors. For the main motor, the only problem I ran into was in connecting the wire to the molex plugs, as they tend to like much smaller wire. It worked out okay though!

• Below is a picture of the final circuit used for the main motor.

• The procedure is very similar for the tail motor. The only differences are wire length and the addition of the (already connected) resistor. Here is how the resistor connection looks. This is using 20 AWG wire, which later had to be changed to 26 AWG wire.

And after shrink wrapping it.

The completed circuit looks almost exactly like the main motor circuit. I had to move the fuses away from their original location because the canopy would not fit on. They are both attached to the 3n1 unit via velcro and everything seems to be working as normal. Here are a few more pictures that show the final setup. Be aware though that when I took these pictures, I had the main motor plugged into the tail motor spot and vice versa. I'm sorry for the confusion. I hope this will be able to help some people out, and I'm sure to be adding more to it!!

About Me

Background: I am 31 years old and have wanted to fly RC helicopters since I was a child. I never had the chance to until this year, so I do not have much experience flying. I have an MSEE and work as a software technical support engineer right outside of Boston, MA. I am using the RealFlight G3.5 simulator and practicing hovering my BCPP in my living room. This it my second modification to the BCPP but my first real “big” one. I have previously swapped out the stock Main Shaft and Drive Gear (050) with the Microheli equivalents with autorotation. I believe this to be a great modification and taught me how the whole head assembly goes together. I can be reached directly at jay427@gmail.com

--Jay427 11:35, 14 March 2007 (EDT)