Has anyone mounted a gps unit outside a rocket?

FastAsleep · Mar 21, 2015

After months of researching gps units that folks use to track their rockets and reading many of the posts on TRF, I have not see anyone that has mounted one on the outside of the airframe. The units that would be most suited for this are the dog collar type (legality notwithstanding) in that they are fairly durable and readily available.

The issues I have with several of my rockets are:
1. They were not originally built with a payload section in mind.
2. There is no room in the nose cone.
3. The av-bay is too close to the nose cone.

By attaching an external gps unit low on the fincan it would hopefully lessen any interference with internal threaded rods and move the unit a safe distance away from the av-bay electronics. For sub-sonic flights e-tape would be sufficient and though it might be ugly, an ugly rocket is better than one you never see again.

Miles

Buckeye · Mar 21, 2015

FastAsleep said:
After months of researching gps units that folks use to track their rockets and reading many of the posts on TRF, I have not see anyone that has mounted one on the outside of the airframe. The units that would be most suited for this are the dog collar type (legality notwithstanding) in that they are fairly durable and readily available.

The issues I have with several of my rockets are:
1. They were not originally built with a payload section in mind.
2. There is no room in the nose cone.
3. The av-bay is too close to the nose cone.

By attaching an external gps unit low on the fincan it would hopefully lessen any interference with internal threaded rods and move the unit a safe distance away from the av-bay electronics. For sub-sonic flights e-tape would be sufficient and though it might be ugly, an ugly rocket is better than one you never see again.

Miles

I think you over-constraining yourself.

1. Add a small payload section to house your tracker.
2. Trackers fit in 38mm tubes or less. You have plenty of room in a nose cone.
3. Not an issue with some combos of tracker/altimeter. My MAWD and BRB900 sit in the same avbay and between threaded rods. Not a problem.

Titan II · Mar 21, 2015

Funny you posted this today. While at a launch today, I decided to do exactly that (at least test the proposition). Before I started using a GPS and tracker, I completely prepped the rocket for flight in advance of going to the field (minus the igniter for the motor). I now use a GPS and tracker in all rockets. Unless I do some significant modifications, the components must be turned on and installed at the field. This includes installing in locations designed to hold them or taping to shock cords, putting the shock cords and chutes back in the rocket and installing the shear pins. I plan on installing the GPS and tracker in a pod that can be attached on the outside. I have seen too many mistakes made while assembling rockets and motors at the field.

Buckeye · Mar 22, 2015

Yes, I agree with your assessment. Dog collar would be best for outside mounting, if that is your plan. Other GPS units tend to be a little more fragile and need more protection.

JohnCoker · Mar 22, 2015

FastAsleep said:
By attaching an external gps unit low on the fincan it would hopefully lessen any interference with internal threaded rods and move the unit a safe distance away from the av-bay electronics.Miles

I assume you're not planning to use an reloadable motor? If so, that would add a large aluminum cylinder which would affect the signal.

RDF trackers are small enough to tape to the recovery harness. (This was a common way to mount Walston units back in the days before GPS trackers.)

FastAsleep · Mar 23, 2015

JohnCoker said:
I assume you're not planning to use an reloadable motor? If so, that would add a large aluminum cylinder which would affect the signal.

RDF trackers are small enough to tape to the recovery harness. (This was a common way to mount Walston units back in the days before GPS trackers.)

My knowledge of radio signals is lacking but I assumed that the aluminum motor tube and any internal metal would affect the signal, but only when the metal was between the source and the receiver. So at least some signal would get through.

I had considered taping the unit to the recovery harness but that would put the antenna within a foot of the av-bay on any of the rockets I would be using.

I use RRC3's on all of my DD rockets and read on TRF that Missle Works recommended keeping dog collars two feet away. Unless I can find someone locally with a dc 40 collar to place near a RRC3 during powerup I would have to buy the system and see what proximity is acceptable.

Miles

scsager · Mar 23, 2015

Word of caution...

GPS Dog Collars (with the exception of the Garmin units) tend to have limited range and often require a monthly subscription or Cell service or both.

The Garmin collars are a bit bulky. Usually not a problem on a dog, but may not work so well on the outside of a rocket going several hundred MPH.

FastAsleep · Mar 23, 2015

scsager said:
Word of caution...

GPS Dog Collars (with the exception of the Garmin units) tend to have limited range and often require a monthly subscription or Cell service or both.

The Garmin collars are a bit bulky. Usually not a problem on a dog, but may not work so well on the outside of a rocket going several hundred MPH.

Thanks Scott:

I've only been researching the Garmin for the long range and lack of additional payment.

I fly a Booster Vision Gear CAM (which isn't made anymore, apparently). It is 1" x 3.75" and has even survived a couple of shreds so far. I think the fastest it has gone is about 600 mph. The Garmin CD 40 is not a lot bulkier than that. (The trick is finding e-tape that matches the color of the rocket.)

Miles

bobkrech · Mar 24, 2015

Everyone I know using a Garmin puts it inside the payload compartment.....

Bob

rockdoc · Mar 24, 2015

I put my Garmin in the nose cone for my 3 inch and larger rockets, on some I use both a Garmin and a RF transmitter.

FastAsleep · Mar 24, 2015

rockdoc said:
I put my Garmin in the nose cone for my 3 inch and larger rockets, on some I use both a Garmin and a RF transmitter.

Do you allow the antenna to bend if the nose cone is not long enough?

Miles

Has anyone mounted a gps unit outside a rocket?

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