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I have a Mongoose 54 that's been close to flyable for at least a year, if not two. The holdup? Bothering to get the electronics mounted!
Since I plan to fly it at BALLS this year, I figured it was time to get off my butt, and get things finished up. There are two things that are needed -- the altimeter mount, and a mount for a tracker. In my case, a Big Red Bee.
Being Carbon Fiber, I need to get the antenna outside the airframe. But, at the same time, it would be ideal if I can protect the main body of the tracker. That means putting it in either the nosecone or the coupler.
Thinking about how to do it, I realized that I can easily fit a Raven inside the coupler, and have plenty of room left over for the tracker. Even easier is to use the Raven AvBay, and avoid having to run arming wires through a hole in the airframe!
So, that's what I did. The coupler itself is setup as an AvBay with two pieces of 1/8" threaded rod run between the bulkheads on either end. This provides somewhere to mount electronics, while at the same time, holding things together during deployment.
I then cut several 1/4" plywood bulkheads that fit inside the coupler, and drilled holes to slide over the threaded rod.
Two of those bulkheads then received holes that line up with the 29mm Raven AvBay's holes. This way, I can run 4-40 threaded rod through the two bulkheads and retain the Raven AvBay in between. A piece of 29mm tube around the Raven AvBay helps keep the battery where it belongs.
The bottom bulkhead gets a set of 4-40 nuts and washers on the underside, followed by another set on the top. This secures the 4-40 rod in place where I want it. Next, I slide the active bulkhead for the Raven AvBay down, and secure it with more 4-40 nuts. Now, I have the active bulkhead and the Raven secured in place, as well as having positive contact from the active bulkhead to the threaded rod, by virtue of sandwhiching it between the sets of nuts.
Next, the battery goes onto the active bulkhead, the 29mm tubing is slipped over the assembly, then the battery restraint goes on. Finally, the top wooden bulkhead is slipped over the 4-40 rod, and secured in place with more 4-40 nuts and washers.
That whole assembly is then slid over the 1/8" threaded rod that is part of the main electronics bay, and the top bulkhead gets a pair of 1/8" nuts to hold it in place.
Over this, I'll place a mounting board for the Big Red Bee, which I haven't yet built. It will be secured in place via another bulkhead.
I'll wire the ejection charges to the 4-40 threaded rod, just like a standard Raven AvBay setup.
By paying attention to the orientation of the active bulkhead when I marked the holes for the 4-40 rod, I was able to position the magnetic switch near the wall of the coupler tube, making it possible to arm and disarm the AvBay using a magnet.
One thing to note with all of this is that I've added a *lot* of hardware, which will reduce altitude. That's something I'm not overly worried about, as is evidenced by the presence of forged eyebolts on either end of the main avionics bay.
Also, when doing something like this, it's important to realize that the holes on the 29mm Raven AvBay are not equally spaced. Orientation matters, if you want to be able to activate the magnetic switch!
I'll post more pictures once I get the tracker mounting completed.
-Kevin
Since I plan to fly it at BALLS this year, I figured it was time to get off my butt, and get things finished up. There are two things that are needed -- the altimeter mount, and a mount for a tracker. In my case, a Big Red Bee.
Being Carbon Fiber, I need to get the antenna outside the airframe. But, at the same time, it would be ideal if I can protect the main body of the tracker. That means putting it in either the nosecone or the coupler.
Thinking about how to do it, I realized that I can easily fit a Raven inside the coupler, and have plenty of room left over for the tracker. Even easier is to use the Raven AvBay, and avoid having to run arming wires through a hole in the airframe!
So, that's what I did. The coupler itself is setup as an AvBay with two pieces of 1/8" threaded rod run between the bulkheads on either end. This provides somewhere to mount electronics, while at the same time, holding things together during deployment.
I then cut several 1/4" plywood bulkheads that fit inside the coupler, and drilled holes to slide over the threaded rod.
Two of those bulkheads then received holes that line up with the 29mm Raven AvBay's holes. This way, I can run 4-40 threaded rod through the two bulkheads and retain the Raven AvBay in between. A piece of 29mm tube around the Raven AvBay helps keep the battery where it belongs.
The bottom bulkhead gets a set of 4-40 nuts and washers on the underside, followed by another set on the top. This secures the 4-40 rod in place where I want it. Next, I slide the active bulkhead for the Raven AvBay down, and secure it with more 4-40 nuts. Now, I have the active bulkhead and the Raven secured in place, as well as having positive contact from the active bulkhead to the threaded rod, by virtue of sandwhiching it between the sets of nuts.
Next, the battery goes onto the active bulkhead, the 29mm tubing is slipped over the assembly, then the battery restraint goes on. Finally, the top wooden bulkhead is slipped over the 4-40 rod, and secured in place with more 4-40 nuts and washers.
That whole assembly is then slid over the 1/8" threaded rod that is part of the main electronics bay, and the top bulkhead gets a pair of 1/8" nuts to hold it in place.
Over this, I'll place a mounting board for the Big Red Bee, which I haven't yet built. It will be secured in place via another bulkhead.
I'll wire the ejection charges to the 4-40 threaded rod, just like a standard Raven AvBay setup.
By paying attention to the orientation of the active bulkhead when I marked the holes for the 4-40 rod, I was able to position the magnetic switch near the wall of the coupler tube, making it possible to arm and disarm the AvBay using a magnet.
One thing to note with all of this is that I've added a *lot* of hardware, which will reduce altitude. That's something I'm not overly worried about, as is evidenced by the presence of forged eyebolts on either end of the main avionics bay.
Also, when doing something like this, it's important to realize that the holes on the 29mm Raven AvBay are not equally spaced. Orientation matters, if you want to be able to activate the magnetic switch!
I'll post more pictures once I get the tracker mounting completed.
-Kevin
