Eggfinder Bay Examples

Dad Man Walking · Jul 14, 2014

We just purchased the Eggfinder kit with all the trimmings and are looking forward to building and flying it.

I am thinking about putting the tracker/antenna into a small bay so that we can move it between rockets at a launch. I read that Cris is suggesting a 6" BT55 body, which would house the board, antenna, and batteries easily.

I'm looking for examples of how people have done this...what size tubes are they using, how they secure the sled and bulkheads with/without threaded rod, examples of external switches and antennas, attachment points to the nosecone or recovery harness, etc. I'm also interested in seeing minimum size builds using external flexible antennas so that the payload can be stashed into smaller rockets.

I will start searching the forums for examples and will post the links here. And if any of you kind folks have good ideas and pictures that have not been shared yet, I think lots of us would appreciate seeing how you did this.

Thanks in advance...

Area66 · Jul 14, 2014

All my nose cones will have a tracker bay in it

here a photo of my nike smoke nose with a 54mm blue tube kit , I use 2 parts foam between the blue tube and the cone, all my nose cone are fiberglass , so it's more easy to glue something

ksaves2 · Jul 14, 2014

Question:

I thought Cris cautions about having all-thread running through the Egg Finder bay if the antenna is contained parallel within it? Do you run the antenna out aft through the bulkhead? No interference with an aft facing antenna then.

I've taken to using an epoxied in place thick ring bulkhead notched with a press fit plywood carrier held in place with blind nuts and a solid bulkhead. A real pain but no metal other than the eyebolt at the aft end. I'm paranoid and use 4525B epoxy and screws spaced round the ring bulkhead. Pictures later. Kurt

Area66 · Jul 14, 2014

ksaves2 said:
Question:

I thought Cris cautions about having all-thread running through the Egg Finder bay if the antenna is contained parallel within it?........

You think to much and don't launch enough rockets. In the same rocket I have good results with a Eggfinder, a CSI transmiter and of course a Telemetrum.

ksaves2 · Jul 15, 2014

Area66 said:
You think to much and don't launch enough rockets. In the same rocket I have good results with a Eggfinder, a CSI transmiter and of course a Telemetrum.

That's good. But that was a caution the maker of the device mentions in the manual. The phenomena could be frequency dependent. CSI is in the 1.25 meter band and the Telemetrum is 70cm band. I've had experience with poor performance of Rf devices in metallic painted rockets. I would have more of a tendency
to heed the caution of the kit proprietor but if it works for you, great. I suggest you read page 8 in the user's manual:

https://www.eggtimerrocketry.com/attachments/File/Eggfinder_Users_Guide_B4d(2).pdf

Might be you could be hobbling your reception range but if the rocket isn't going that far, you wouldn't notice. Kurt

Area66 · Jul 15, 2014

ksaves2 said:
Question:

I thought Cris cautions about having all-thread running through the Egg Finder bay if the antenna is contained parallel within it?

and why do you presume my antenna is running side by side with the the thread rods ? I have a question for you Kurt; have you ever launch a rocket with an Eggfinder ?, do you own a Eggfinder ?

Dad Man Walking · Jul 15, 2014

Area66 said:
and why do you presume my antenna is running side by side with the the thread rods ? I have a question for you Kurt; have you ever launch a rocket with an Eggfinder ?, do you own a Eggfinder ?

Uh...did I miss something while I was out of the room? Kurt did the same thing I did...read the manual, and then wanted to understand how others are working within or around those guidelines/suggestions/warnings. It wasn't like he was calling your baby ugly or anything.

I learned a lot by looking at your photos and the diagram you posted. Thank you, that is great information and the reason I like these boards.

(By the way, for the record - I do own an Eggfinder, I've not built it yet, so no ground test or flight experience. And you nailed it...I do think too much and don't fly enough rockets. Just trying to learn from others since that is usually more fun and far less expensive than learning everything the hard way.)

ksaves2 · Jul 15, 2014

Area66 said:
and why do you presume my antenna is running side by side with the the thread rods ? I have a question for you Kurt; have you ever launch a rocket with an Eggfinder ?, do you own a Eggfinder ?

[/Q

Cripes, Don`t get yanked about it. Built 3 of them and your diagram says it all. Perfect non-interfering seup.
Launching has to wait until the corn is in but I've used APRS in several flights of my own and recovered for others.
When I flew in the past, I made mistakes because the information wasn't out there. Now it's a heck of a lot easier to find the info
to have a successfully tracked flight. Kurt

Dad Man Walking · Jul 16, 2014

Area66 said:

What are the two holes in the bulkhead for?

Area66 · Jul 16, 2014

Dad Man Walking said:
What are the two holes in the bulkhead for?

The bulk head come with them, for now they are plugged, but I can unplug them to pass wire for the ematch, I did it twice for dual deployment with cable cutter

Wayco · Jul 16, 2014

I have two Eggfinders, the first one was installed in the N/C of my 5" Jart:

Plenty of room in a 5" rocket, so there were no metal parts within 2" of the antenna:

I built a handheld case that holds my RX with a 6 dbi antenna, a HC-06 Bluetooth module and a 9v battery that is pictured in the above shot.
The second one was installed in the N/C of my MD Blackhawk 54:

With both installs, I made the N/C bulkhead/retention using a kevlar Y harness looped around a hardwood dowel that was mounted in the N/C coupler. The only metal near the antenna is three 6-32 screws and pem nuts that hold the coupler into the N/C.

The space was so limited that the antenna sticks several inches into the payload tube.

I also adapted the original Eggfinder into my 3" Dark star and my 4" Dark star Extreme:

It fits easily into the N/C and the antenna is inside the coupler:

The sled is held in place by a zip tie that goes through holes in the hardwood dowel and around the antenna:

I have four Eggfinder flights in the 5" Jart, from 4600 ft. to 10,126 ft. All held lock throughout the flight and were recovered using the handheld RX linked to an Android phone using the "Rocket Locator" app.
I have one flight in my 3" Dark star on an AT K513 Fast Jack that lost lock but got it back before apogee. Same easy recovery.
The Blackhawk 54 and 4" Dark star have not been flown yet. Ground testing indicates that the smaller the N/C, the less range I get. Flight testing will resume at Airfest over the last weekend of August. Planned flights include the Blackhawk test flight on a J460 to 6700 ft., the 5" Jart on an L1115 to 12,000 ft. and my L-3 attempt with the Dark star Extreme on an M1297 to 11,000 ft.
If the first flight on the Blackhawk goes good, and conditions permit, I have a CTI L935 that could test the range of the Eggfinder to over 17,000 ft.

Fdog · Jul 16, 2014

Dad Man, although this tracker bay was built for a Big Red Bee 70cm GPS, the basic principles are congruent; an EggFinder would slide right in and be happy.

The bottom of the nose cone showing the tracker bay. The hatch is held closed with 4-40 Thumbscrews from McMaster.

Removing the hatch shows the BigRedBee. I wrap the tracker with a strip of foam to eliminate rattle.

Here you can plainly see the 38mm body tube that forms the tracker bay.

The tracker bay sub assembly before being epoxied into the nose cone.

As seen above, the antenna tubes are lightweight acetal tubing. These seemed like a good idea, but, when foaming the nose cone, the tubing gets hot and melts; the tubing can squish closed. To prevent this, I had filled the tubing with lead shot, which in smaller pours had easily prevented "tubing squish". In this case, it almost didn't work. In the future, I will use lightweight fiberglass tubing on projects this size.

There's two different tubes to accommodate different tracker designs. One has a 1/4 wave antenna, the other a 5/8 wave. If all you're using is an EggFinder, then you'd only need a single antenna tube.

A close look at the bottom of the assembly. Note the 4-40 PEM nuts for the bay door, and, the 1/4-20 forged eyebolt.

If you look carefully behind the eyebolt, you can see a 1/4" hole that is the injection site for foaming the nose cone. I have had great success mixing my foam in 40cc batches, and injecting it using a 10cc syringe. Each batch starts to "kick" in about 45 seconds, which is plenty of time for aspirating 4 syringe-fulls of foam mix and injecting it. Also, incremental foaming like this reduces the amount of "overfill" that happens occasionally when you pour too much foam.

I buy my Luer-slip tip 10cc syringes in bulk. IIRC it was $14 for a box of 100. Buying in bulk this way, my mindset is they're truly disposable, so I use them like the tools they are to do things like injecting messy, sticky foam - there is no way you can get a syringe easily clean from foam mix. (BTW, when buying syringes make sure they are Luer-slip, not Luer-lock.)

The parts to build the bay. Glued into the 38mm tube is a regular old bulkhead of plywood.

This is just one way to build a tracker bay, hope it gives you some ideas.

All the best, James

accpool · Jul 16, 2014

Wayco said:
I have two Eggfinders, the first one was installed in the N/C of my 5" Jart:

Plenty of room in a 5" rocket, so there were no metal parts within 2" of the antenna:

Wayco, is there any way you could show more detail of the kevlar - dowel area? I really like it.
Why wouldn't you have turned the Eggfinder 180 and had the antennae go up into the point of the nosecone, just curious?

accpool · Jul 16, 2014

This is just one way to build a tracker bay, hope it gives you some ideas.

All the best, James[/QUOTE]

James, Very elegant design and simple solutions to the issues with the antennae. Why do you foam the nosecone?
Thanks.

Wayco · Jul 16, 2014

accpool said:
Wayco, is there any way you could show more detail of the kevlar - dowel area? I really like it.
Why wouldn't you have turned the Eggfinder 180 and had the antennae go up into the point of the nosecone, just curious?

Wayco said:
I have two Eggfinders, the first one was installed in the N/C of my 5" Jart:

Plenty of room in a 5" rocket, so there were no metal parts within 2" of the antenna.

When I built the 5" Jart, the only Eggfinder I had seen mounted was in a 38mm tube strapped to the shock cord. If someone would have posted up ANYTHING about how to mount a GPS in the N/C, I might have had a better idea how to do it. This is the first thread that has done that. I'm not a rocket scientist, I just figure things out.... I think at the time, I didn't want the antenna near the metal tip at the top of the N/C.
The 1/2" kevlar strap you see in the pic. you posted is my Y harness around the hardwood dowel. It goes out through the bulkhead and connects with a loop to the shock cord. Here it is on the other side of the bulkhead:

The loop connecting to the shock cord is out of the frame below.

accpool · Jul 17, 2014

Wayco, Thank you i see it now, i think i was confused buy the series of pictures above not being the "same" in both rockets and got disoriented.

accpool · Jul 17, 2014

Would there be any issues with putting the Eggfinder on 1 side of the sled and the battery on the other side? This would allow the sled to be shorter and possibly fit in the smaller rockets we have.

Wayco · Jul 17, 2014

The battery I used (900 mAh) is overkill for the Eggfinder, LiPo batteries come in an amazing assortment of sizes. I'm sure you could come up with a more compact design.
Copied from the Eggfinder users guide:

Battery: 300 mAh (min.), 7.4V (2S) LiPo battery recommended

Fdog · Jul 17, 2014

accpool said:
James, Very elegant design and simple solutions to the issues with the antennae. Why do you foam the nosecone?
Thanks.

Thanks for the good words Lance. I foam the nose cone to give the components support, with the foam they can sustain 100's of g's. The foam in this 4" 5.5/1 nose cone is ~80 grams. I certainly don't have the skills to build a structure as similarly robust using plywood and fiberglass, within the same weight budget.

The foam also makes the nose cone stronger, although in all honesty I don't believe my flight profiles have needed the extra strength.

All the best, James

accpool · Jul 17, 2014

Thanks

accpool · Jul 17, 2014

Wayco said:
The battery I used (900 mAh) is overkill for the Eggfinder, LiPo batteries come in an amazing assortment of sizes. I'm sure you could come up with a more compact design.
Copied from the Eggfinder users guide:

Are there any issues with interference or range, I know nothing about radio waves? Would there be any issue with the wires being on the back side and causing a shielding effect, such as the threaded rod in an av bay has been noted?

Wayco · Jul 18, 2014

Don't overthink it, (we'll let Kurt do that) just build what you think will work and fly it. I was worried about pem nuts and 6-32 screws, but decided that a good antenna on the receiver would overcome any attenuation they might cause. This is all new stuff with the Eggfinder, I'm sure we haven't found the range it could get with the right antenna at both ends.

accpool · Jul 19, 2014

OK, will just build and see.

ksaves2 · Jul 19, 2014

Wayco said:
Don't overthink it, (we'll let Kurt do that) just build what you think will work and fly it. I was worried about pem nuts and 6-32 screws, but decided that a good antenna on the receiver would overcome any attenuation they might cause. This is all new stuff with the Eggfinder, I'm sure we haven't found the range it could get with the right antenna at both ends.

,

Yeah, I think the reception range is going to be a lot farther in the air. I must apologize as I couldn't picture Gerard's arrangement until he posted the diagram. I have made many mistakes in the years past before the howto information was readily available. Nothing is more sickening than launching and not having any idea as to where to look. Kurt

Dad Man Walking · Jul 19, 2014

accpool said:
James, Very elegant design and simple solutions to the issues with the antennae. Why do you foam the nosecone?
Thanks.

James, I agree with Lance about the design & execution. If I understand it, the sled you use runs the full length of the bay and it held in place fore/aft by the bulkheads, and the foam wrap is to take up a bit of the slop side-to-side...is that right? Also...instead of messing around with tubing to make tunnels for the antennas, couldn't you just fabricate the n/c and bay without the tunnels, and then drill holes in the foam afterward?

ksaves2 · Jul 19, 2014

accpool said:
Would there be any issues with putting the Eggfinder on 1 side of the sled and the battery on the other side? This would allow the sled to be shorter and possibly fit in the smaller rockets we have.

Lemme overthink this one. I don't think you'll have a problem Lance as long as the battery doesn't parallel your antenna on the other side of the sled.
Putting it opposite of the the EF should be fine. Works O.K. with the Beeline GPS units as the battery is shrink wrapped to the board.

All the bays shown here show the antennas free and clear of parallel metal. That's the only thing you need to shoot for plus not using a metallic paint outside of the radio bay. I dorked the Rf from a 70cm Beeline GPS with a metallic painted rocket so the range was dramatically attenuated. Would it do the same with the 33cm 100mW Egg Finder? I'm not willing to make that mistake a third time.;-) Kurt

Fdog · Jul 19, 2014

Dad Man Walking said:
James, I agree with Lance about the design & execution. If I understand it, the sled you use runs the full length of the bay and it held in place fore/aft by the bulkheads, and the foam wrap is to take up a bit of the slop side-to-side...is that right? Also...instead of messing around with tubing to make tunnels for the antennas, couldn't you just fabricate the n/c and bay without the tunnels, and then drill holes in the foam afterward?

Thanks Dad Man!

I should clarify, there is no sled. I had considered doing that, but it made the system excessively complicated. Hence, I designed the tracker bay to be a snug fit on the tracker (length and width) alone.

Here is a better view of the GPS tracker sliding into the bay

Because the tracker is inserted by itself, I use a slim strip of foam to eliminate rattle. The "tail" of the foam also pops up and is convenient for removing the tracker. The design does not rely on the foam, BTW - I have launched it often without it, the snug fit has been fine by itself.

The BRB with a strip of 1/4" foam

It's worth pointing out that the battery for the Big Red Bee is held to the circuit board with a piece of shrink tubing. This works amazingly well, and is how it comes from the factory. The switch is the wire connector. Since I'm ordering an EggFinder, I will do the same with it as the BRB.

It is interesting to hear you suggest pouring the foam and drilling/milling it out when cured, since I did try to go this route. I went so far as to purchase an extra-long drill bit, and a Forstner bit, from McMaster. The foam I use, a Urethane 4 lb. density two-part pour foam, still has a fairly open cellular structure and crumbled easily after I drilled out the holes in a block of test foam cast in a cardboard tube. These crumbles were messy and I could see where the holes would erode with use. So, I had to go up to a 16 lb density to get a firm, dense foam that milled nicely and was durable. The added density eliminated all the weight gains from not having the internal tubes, and was actually heavier!

Hence I went back to the 38mm tube to give a hard sided hole for a long life.

This has been very easy to use on the launch range - just turn on the tracker and drop it in the hole. About 10 seconds to secure the two thumbscrews and it's done.

All the best, James

ksaves2 · Jul 20, 2014

Here's an old basic nosecone bay with a ring bulkhead, blindnuts, sockethead screws and a sled for a BeelineGPS.
I like James' design better though. I started with a solid plywood bulkhead, drilled the center hole for the eyebolt, screwed the G10 bulkhead to the plywood bulkhead to drill the 6 holes for the sockethead screws on a drill press. Secured blindnuts to the plywood bulkhead, cut out the center hole and notched the bulkhead for the sled.
The sled is press fit into place. The bulkhead is 5/8" thick and secured with Duralco 4525B epoxy, (That's the black color one sees in the pictures.) My hat's off to the other designs here.

Nosecone base (string is for storage from a ceiling hook)

With bulkhead off

G10 bulkhead

G10 with metal shielding which is unnecessary for low powered trackers. I fancied putting a high powered tracker in and laminated the metal shielding on the back of the bulkhead after I had altimeter failure with 150Mw 70cm tracker (pad deployment of charges) and witnessed a 2watt Garmin GPS dog tracker shutdown two altimeters in a 12 inch diameter 16.5' tall O powered rocket. It went ballistic.

Nosecone and sled for BeelineGPS. The sled was sanded to press fit with bulkhead attached.

As I said, I like the idea of a fixed bulkhead with a tube carrier and offset eyebolt. Much easier to build. I built two of these nosecone tracker bays for two 4 inch projects. Kurt :jaw:

cerving · Jul 20, 2014

Did either one of you have to add ballast to the NC? I'm building a FG Patriot that's going to need some, I'm planning on putting a 29mm AV tube in the NC for an Eggfinder, but obviously I can't put ballast in the tip of the NC. I was thinking about putting in another centering ring in the middle, then filling in the space between the centering ring and the bulkhead with steel shot/epoxy. Or, I could just put in a full-size sled and put some ballast on the sled opposite the Eggfinder... that would probably be easier, but much less elegant.

ksaves2 · Jul 20, 2014

Did either one of you have to add ballast to the NC? I'm building a FG Patriot that's going to need some, I'm planning on putting a 29mm AV tube in the NC for an Eggfinder, but obviously I can't put ballast in the tip of the NC. I was thinking about putting in another centering ring in the middle, then filling in the space between the centering ring and the bulkhead with steel shot/epoxy. Or, I could just put in a full-size sled and put some ballast on the sled opposite the Eggfinder... that would probably be easier, but much less elegant.

----------------------------------------------------------------------------------------------------------------------------------------------------------------------

My projects are long necked and the weight distribution is right. I didn't have to add weight.

I forgot I built a third nosecone/carrier for an early Dominator 4 kit/collection of parts.

There's a thrust block to support the tracker.

I'd say build it with the ballast opposite the EggFinder. It will be easier to add weight if you underestimate. The two
bulkhead suggestion is elegant and neat but is also permanent if you epoxy the two together. You get it wrong, you're stuck unless you buy the fix'ins for another nosecone carrier.:rant: Ok, ok. You could leave extra space in
between the two bulkheads, drill a hole to add extra but that's a pita.

Anyhow, is your antenna going to go all the way out to the tip of the nosecone? If not, you might be able to get away with a little ballast encased in epoxy at the tip. But then again, if you'll be needing a substantial amount of weight, it would be easier to put it on the opposite side of the EF carrier board where you could adjust it if need be.
Kurt (I think too much) :grin: Anyhow, who the heck is going to know (besides you!) when you show/fly the rocket? :wink:

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