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Beeline Tracker Pods
#1
Beeline 70cm RDF Beacon Mounts


As you probably know, MARS is taking a more proactive stance on rocket recovery to avoid insurance claims and potential field loss due to rockets being left behind in downwind crops.  The club is investing in Beeline trackers for loan and sponsoring members who wish to purchase their own.  Other tracking systems are of course acceptable- ComSpec, Walston, GPS units like the BigRedBee 900Mhz, others.

This series of posts will be about a pair of modular mounting solutions designed around the BigRedBee Beeline 70cm transmitter with a wire whip antenna.  The mount is nearly as small as possible, robust, and due to CNC design and production parts are interchangeable.

UpscaleCNC was founded to provide custom and wholesale parts for the rocket market, some of you have used our services.  While I am advertising and offering a product for sale, please know this:  for MARS club members these mounting solutions will be sold at material cost, ONLY.  I feel radio tracking rockets is smart and responsible-  you get your expense back (are rockets investments?!) no matter which corn field it lands in and the hobby can stay in the good graces of landowners and farmers.  I hope this program will be a success, UpscaleCNC will help in any way possible.

So, next post, some pictures and descriptions.

Nat Kinsey

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#2
What the heck is this "beeline"?

A Beeline is a small, low power, radio transmitter.  It operates in the 70cm radio frequency range which is around 432MHz on your FM dial, this is also a ham radio frequency range which is why these devices must be operated by licensed hams.  A technician license is required.  The transmitter emits tones- a series of long beeps and occasionally the call sign of the owner, in Morse code.

What good is this you say? Well, go lose the transmitter in a corn field preferably with a rocket attached.  To find it, we use a highly directional antenna.  Most antennas you are familiar with (the ones on cars) are designed to receive signals from all over, good for listening to tunes.  We use a "Yagi" antenna that looks a little like the TV antennas on roofs.  It receives signals only from one end.  So when you point the antenna at the transmitter you get a strong signal, when you point it away from the transmitter the signal drops off rapidly.  Following the strong signal will take you in a line towards your rocket. 

Distance can be estimated by how strong the strong signal is but this is NOT GPS.  It is however much cheaper, smaller, and requires less receiver equipment to decode GPS location transmissions.

Here's a picture of the Beeline and its battery.  The unit ships with the battery shrink wrapped to the transmitter, for these mounting solutions we separate the two.  The razor blade is for scale, or cutting the shrinkwrap!?



Nat Kinsey

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#3
1st Mounting method:  Pod on the recovery harness

Both methods use the same piece of blue-tube.  The tube is a 2.4" length of 29mm coupler, the smallest bluetube available.  Blue tube is much stronger than phenolic or paper tubes and lighter and easier to work with than fiberglass.

The mount is constructed like a small altimeter bay.  A fiberglass bulkhead is glued into one end with a threaded rod (4-40) bolted to a central hole and a small hole to allow the antenna to extend outside the tube.  The tracker slides into one side of the tube, the battery the other- separated by the threaded rod.  The threaded rod is used to secure the closure on the other end, in this case, a cap of airframe tube and a 1/4" plywood bulkhead.  The bulkhead has a three holes- a central one for the threaded rod, the other two are for a loop of kevlar cord to provide a mounting point.  The cord can be clipped into a swivel, a quick link, or passed through itself around a shock cord. 

This mounting method is EASY to retrofit into rockets with a little extra space.  Place the mount above the parachute protection to keep it away from ejection charges.  The downside of this is the antenna will get abused and bent.  Note, however, that the wire whip antenna is easily replaced as it solders to a single large solder pad on the board. 

Pictured here, the cap is a piece of white LOC paper tube.  It will be Blue Tube airframe in production.



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#4
Bulkhead mounting option

The alternative to having the tracker mounted in a pod in with the recovery gear is a bulkhead mount.  In this case, the bulkhead is designed to fit inside the shoulder of a 4" PML plastic nosecone.  The end of the cone coupler is cut off and the bulkhead shoved through the coupler, then turned and pulled against the internal shoulder.  Epoxy will hold it in place; the shoulder will keep it from ever pulling out.  A bulkhead for a large altimeter bay can support a tracker, a bulkhead for the end of a payload bay can work too.  Nosecones are good places for trackers-  far away from the controlled explosion at the rear and the shell provides extra protection.  It's also the first thing to hit in a ballistic recovery.... nothing's perfect.

To secure the tracker pod to a bulkhead, the lid is changed out.  A flat plate lid made from .093" G10 has three holes and a circular groove in the back.  The groove centers the lid on the end of the tube.  The central hole is for the threaded rod, the other two holes are clearance for 4-40 socket head cap screws (not pictured here, don't have any yet) that bolt the cap to the bulkhead.

The bulkhead gets a set of three holes:  clearance for the tracker pod tube, and two holes to hold 4-40 PEM nut threaded inserts.  In this case, the bulkhead is large enough to also have a 1/4-20 eye bolt.  Smaller bulkheads may not have the space, a loop of strong kevlar cord takes up less space and is strong enough to secure a cone.  The cap may require sanding to fit the curve around the edge, or another cap can be made to fit.  Small cones will require a special mount be made- the tube must be glued into the cone as the bulkhead won't be large enough.  There will be a special-case post later about these.



Nat Kinsey



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#5
One more picture....

Dumb web admin only allows 4 per post.  :Smile

This picture shows the pod from the backside of the bulkhead.  Tracker isn't installed, the whip antenna would extend forward into the nosecone.

Nat

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#6
Other Mounting Options

This isn't the only way to mount trackers, of course.  Some in the club have been using them in pods made from narrow PVC pipe and PVC pipe caps, with a loop of kevlar or nylon cord to secure them.  Glue one cap on, drill the other one for a screw.  Some have flown trackers in plastic film cans (remember those?!) taped to a shock cord.  They can be bolted down inside altimeter bays to the electronics sled.  My tracker flew electrical taped to the shock cord of a 5.5" Honest John that shredded at near Mach 1... it survived the trip.

Point is, these two solutions are just one option that is easy to produce and use.  These may work for you and your rockets, maybe there's a better way for you.  If you're using an alternate tracking device, those probably won't fit in these mounts.

Nat Kinsey
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#7
Pricing and Availability: 

Coming very soon.  I need to determine costs-  the threaded rod, pem nuts, and tubing. 

Bulkhead designs will require individual discussion and design for some sizes.  Cones are different, etc. 

Nat
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