EggFinder Mini (AND Fullsized) 3D Printed Sled - Full Sized EF sleds available

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A 29mm coupler version would be nice too... I have an extra RW Mongoose 29 that's just waiting for something like this. The jury-rigged tracker NC sled that I did isn't nearly as nice as this one.
 
A 29mm coupler version would be nice too... I have an extra RW Mongoose 29 that's just waiting for something like this. The jury-rigged tracker NC sled that I did isn't nearly as nice as this one.

What is the ID of the NC coupler on that one to xx.x mm accuracy?
 
OK, so I think this is the 38mm version. I see making an adapter collar that could be put in 54 and 75 NCs to allow the same sled to be used. In these heavier cases the sled would have none of the NC load. The 29mm version will require a major redesign...in time.

The 38mm kit would include 3 parts along with M4 set screws.

1) Sled
2) Aft "bulkhead"
3) Drill Guide

You would supply an eye bolt and (lock)nut (M6 pictured, but hole is meant for 1/4-20 as that is what the stock bulkhead is drilled for), and the kit parts of course.



To assemble you use the drill guide to locate the holes that are drilled with a 1/8" bit. I recommend that you tap these holes for M4. With that the coupler is prepared.



The attachment of the EF-mini is self explanatory, and the battery can be held in place with up to 3 zip ties. The sled includes a capture for a 1/4-20 nut (M6 shown here which is why it appears loose). The stock fiberglass bulkhead is then sandwiched between the aft "bulkhead" and the sled and screwed together with the bolt. The purpose for leaving the stock bulkhead in the system is to provide an extra stiff layer, and there by keep the printed parts "in compression" between the set screws and the fiberglass plate when the NC hits the end of the shock cord. The Eyebolt is also recessed into the "aft bulkhead" to save some space in the main recovery bay.



When it is time to fly just plug in the battery, slide the sled sandwich into the NC and put in the set screws (making sure to get them deep enough that the NC coupler will slide freely in the body tube). I'm showing this one with the NC unglued for clarity, but it doesn't need to be that way.



The entire NC with hardware, tracker and battery is 7 oz. I put 75 lbs of force on the eyebolt without any sign of damage upon disassembly...if you have more than a 150G shock at the end of your cord something went very wrong.

Also, I received a suggestion to make these more visible than purple, so I have orange PETG in hand for producing these.

Thoughts?
 
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Can anyone give me dimensions on the 38mm polycarbonate cone like the one Wildman sells?

I need coupler ID, OD and depth from the aft end of the coupler to the NC inside tip.
 
Has anyone come up with a workable idea for a 3D printed sled/av-bay without needing all thread? I've been having thoughts about running a Kevlar line through, but I'm not sure that would be enough. Could save some weight (and RF interference for transmitters).
 
Review

I took my tester unit out this last weekend to put it through some flights. First off was a 4" Talon'ish missile. I attached the unit to the lower shock cord so that it would be hanging free after apogee. I gave it a nice little nomex blanket to keep it safe. Everything looked ok.
You can probably tell by my grammar that something went wrong.
User error : I have been doing HPR long enough that I should have looked at the unit and noticed an immediate problem. The eye bolt. Mine obviously opened under the shock of apogee deployment. When I got the rocket back, there was no sign of the unit at all. I got tracking data until 56ft off the ground, a second or two before the unit landed. I retrieved my rocket and searched around hoping to pick up a signal, but I couldn't even get a blip. I suspect either battery damage, or the antenna broke off on landing. It is somewhere in the sage. I am hoping that someone finds it at the next launch.

Overall - Really nice unit. The electronics and battery fit in there snug, I love the battery retention with zipties. You dont even have to remove the battery to recharge! If the eyebolt was changed to a closed unit I would highly recommend this as an option for tracking!
 
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I don't want to hijack, but how often do eyebolts open? Is this a big risk?
 
Review

I took my tester unit out this last weekend to put it through some flights. First off was a 4" Talon'ish missile. I attached the unit to the lower shock cord so that it would be hanging free after apogee. I gave it a nice little nomex blanket to keep it safe. Everything looked ok.
You can probably tell by my grammar that something went wrong.
User error : I have been doing HPR long enough that I should have looked at the unit and noticed an immediate problem. The eye bolt. Mine obviously opened under the shock of apogee deployment. When I got the rocket back, there was no sign of the unit at all. I got tracking data until 56ft off the ground, a second or two before the unit landed. I retrieved my rocket and searched around hoping to pick up a signal, but I couldn't even get a blip. I suspect either battery damage, or the antenna broke off on landing. It is somewhere in the sage. I am hoping that someone finds it at the next launch.

Overall - Really nice unit. The electronics and battery fit in there snug, I love the battery retention with zipties. You dont even have to remove the battery to recharge! If the eyebolt was changed to a closed unit I would highly recommend this as an option for tracking!

I am really sorry to hear that...never trust a non-forged nut I guess. In the revised version I'll post shortly the eyebolt will be left up to the purchaser. The capture for the nut will accept an 11mm wide nut, which is about perfect for a 1/4-20 nylon lock nut, or slightly oversized for an M6.

Thank you again for testing this...your feedback has been very helpful in designing a better unit.
 
OK, the nose cone mount version did not show any damage at the 110 lb max of my scale. The shock cord attachment version broke at 72 lbs of force. I have made an adjustment and am printing that version now. If it passes the 110 lb test tomorrow evening everything will be finalized.
 
I don't want to hijack, but how often do eyebolts open? Is this a big risk?

It's something that only happens under suboptimal circumstances, such as deployment at speed, but it's always a surprise and disappointment. I'll never fly anything other than a forged or welded eyebolt (or a u-bolt) in anything that carries expensive motor hardware and electronics. It's one of those things that's so easy to mitigate that it's ridiculous to ignore.


Steve Shannon
 
Because it will be easier to see some features in the CAD model here is the modular system. It is made of 4 parts:

1) sled which fits in a 29 mm body tube (not coupler tube).
2) Outer casing that can be put on sled directly to protect and strengthen sled for shock cord attachment. Simply using the middle screw only gave a system that only broke under 72 lbs force...adding the other two screw holes should increase that markedly.
3) Bulkhead for 38 mm Nose cone mounting. This fits Wildman available injection molded composite cones and Madcow available RW filament wound fiberglass cones with one wrap of masking tape (the IDs are really close, but not the same).
4) Drill guide so the holes in a nose cone shoulder/coupler line up with the holes in the bulkhead. This fits both NC types as their IDs are very close.

I will be offering a limited number of these for sale as a test of the manufacturing and shipping process as a way of making an informed decision about going forward with becoming a niche vendor. I have been contacted by several folks so far and have 3 units committed, so if you have interest please let me know via PM. I will be invoicing through PayPal, so you will have PayPal protections, and I won't invoice anyone until I have the desired unit ready to ship. I would expect to be ready to ship units next week as I have all screws and shipping supplies in hand.

The kit will come with appropriate screws for NC and outer case mounting (along with a few extras too). The buyer will provide eye bolt and associated hardware (nut capture is 11 mm), and mounting screws for EggFinder mini. I have to get final print times before I can firmly set pricing, but I plan to offer three versions:
1) NC mounting kit: Sled, Bulkhead and Drill Guide...~$20
2) Shock Cord mounting kit: Sled and Outer case...~$20
3) The Works: Sled, Outer case, Bulkhead and Drill Guide...~$30

Shipping will be standard USPS for a flat rate of $4 (CONUS) for up to 4 units.



I want to thank the folks that have beta tested the earlier version, and provided really helpful suggestions. I'm very sorry for the eyebolt failure with Salvage-1's unit...I was so focused on the printed part that I didn't give appropriate thought to the hardware.

I'll post up some real pictures tomorrow evening along with updated breaking strength info. I've used almost a Kg of filament designing, test fitting, breaking, and redesigning these so I think I have reached a sound design. Also of note, these are printed at 100% infill, so there is no void space within the printed parts. As a test one of these sleds has also been sitting in my car for the last 2 weeks spending parts of each day (up to 97 deg) in the direct sun with no sign of deformation or warping...I love PETG.

Comments are welcome as I've tried to do this as transparently as possible.
 
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1) The Shockcord Mount: Contains - (1) Sled, (1) Outer Shell and (5) 4-40 screws - Price $21



What you need to add: (1) Eyebolt and Nut, (3) Zip Ties, Eggfinder Mini, LiPo, (2) Mounting Screws for EF-minir (I like 4-40 nylon shearpins).



Mounting is pretty self explanatory, but be sure to pull zipties tight and pay attention to the location of the ziptie's "head"...keep them away from edge of LiPo as it will interfere with Outer Shell alignment.



Slide sled into case making sure rear hole in Sled aligns with that on the Outer Shell...there are guides printed into the outer shell to ensure alignment as long as you start out within about 15 degrees of aligned. Once the sled bottom is level with the case the holes should be aligned and the screws can be inserted...the top screw alone provided strength to 72 lbs of force at which time the sled snapped. With all three in place the scale was maxed at 110 lbs with no sign of damage. Also, the sled will fit inside a 29mm body tube (Estes PSII Motor Mount pictured).

 
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2) Nose Cone Mount: Contains - (1) Sled, (1) Bulkhead, (1) Drill Alignment Guide and (5) M4 set screws - Price $20



What you need to add: (1) Eyebolt and Nut, (3) Zip Ties, Eggfinder Mini, LiPo, (2) Mounting Screws for EF-mini (I like 4-40 nylon shearpins), 38 Nose Cone (Wildman/CTI Injected molded or Madcow/RW Filament wound, and NC bulkhead (if available and desired)...could substitute a fender washer or wooden bulkhead (could go without, but I wouldn't recommend it).



Mounting is pretty self explanatory, but be sure to pull zipties tight and pay attention to the location of the ziptie's "head"...keep them away from edge of LiPo as it will interfere with Outer Shell alignment. Use the Eyebolt to make a bulkhead sandwich as shown.



Next you need to prep the nosecone. Specifically the holes must align with those already printed into the bulkhead. To accomplish this use the included drill guide. Place the drill guide THIN SIDE AFT on the NC shoulder/coupler, and drill one hole with a 1/8 drill bit. Ideally remove the guide and tap the hole for an M4 screw. Realign the guide to the hole and insert an M4 set screw to ensure proper alignment is maintained, and repeat process for remaining holes. This isn't as hard as it may sound...as long as the aft end of the guide and the aft end of the NC shoulder/coupler stay flush and square (helps to stand the NC/coupler on the table top for this), and the first hole doesn't lose it's relationship to the guide everything will come out fine.



Lastly, slide the bulkhead in and screw in the set screws making sure they are properly recessed into the coupler. For the Madcow/RW cones one wrap of masking tape around the coupler will ensure a snug fit)

 
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3) The Works: Includes - (1) Sled, (1) Outer Shell, (1) Bulkhead, (1) Drill Guide, (5) 4-40 screws and (5) M4 Set Screws - Price $30



Directions same as with above options. You could also use the Outer Shell with the full bulkhead stack of The Nose cone mount system for shock cord attachment too, but the nose cone mount setup will not fit indie the 38mm nose cones with the Outer Shell in place.
 
If you only want the sled you can buy that for $15.

I want to emphasize that this is a limited run. I'm not trying to end run the vendor rules as I am really still up in the air on the idea, but I'm doing a "vendor beta test" that I have discussed with one of the mods beforehand. I also do not plan to directly compete in any existing niches like those occupied by Additive Aerospace.

If you would like something PM me what you would like, and I will invoice you via PayPal when your item is ready to go. That way you have all the PayPal protection, and I'm not taking money for something I don't have in hand...we've seen that go wrong around here before.

Shipping will be standard USPS for $4 CONUS on up to 4 units.

I expect that invoices will go out over the holiday weekend and shipment will begin on the 5th, but again I will not invoice until your order is ready to go.
 
Several people mentioned they would like a version for the full sized EggFinder, me too. This is the second attempt (first was an unmitigated disaster). So many things different things wrong it was barely a starting point.

Anyhow. this version fits in the RW NC using the same bulkhead as with them mini version (I made the nut capture the wrong size in the sled which is why it is shown with a machine screw here). This thing is never going to fit in the Wildman/CTI cone, and as you can see it needs a small antenna to fit in the RW version. However it does fit in a 38 mm coupler, so that opens a lot of possibilities for mounting). This need several more versions, but the thing I think it is really missing is antenna support. Not a good way to tackle that based on the wide variety of antennas people use. Other than that, does anyone have any comments or suggestions about how to improve it? Ignore the hairs all over it...I can mostly fix that adjusting the seam location.

 
I see 3 types of antennas on full size EFs: wire stick, stubby, and full size. For antenna support, you could put a little 'nub' sized for the stick, and the end user could simply sand/cut/file/dremel to fit their specific configuration. Maybe make the nub stepped so that the user would know where abouts to start fitting.
 
I see 3 types of antennas on full size EFs: wire stick, stubby, and full size. For antenna support, you could put a little 'nub' sized for the stick, and the end user could simply sand/cut/file/dremel to fit their specific configuration. Maybe make the nub stepped so that the user would know where abouts to start fitting.

Thing about antennas is that the Nubs might not be so optimal if one is trying to get the best range out of their system. Nice thing about it though is it's least
likely to be damaged by the jostling and recovery forces placed on the antenna. That said, there is a potential that the antenna could be damaged and in the
case of the EF Mini, the board could be trashed. Me? I'm willing to take that risk with my two. I certainly would not count on a Mini as the primary tracking source above 20k where the drift might be for miles. Maybe as a secondary backup to a Ham band based (higher powered) primary GPS tracker or a higher powered 900 Mhz tracker.
Don't get me wrong. For sport flying this is a really great thing. Under 10k flight with decent terrain (ie. flat land) and one stands a much greater chance of recovering a completely "sight unseen" flight. I've done it a lot with small projects and it's something to walk right up to the rocket lying on the ground with
an obviously deployed recovery system that worked fine. Otherwise run the risk of losing a "perfectly reusable" rocket" !
The "longer" ie. higher gain antennas tuned for 900Mhz have the potential of increased performance but if one's rocket
isn't expected to be going "that far" it's superfluous. Especially if one simply wants to get that "last known" position and put it into
a mapping GPS device to get one close to the rocket in hopes of finding it or picking up a new position to "home in" on it. Kurt
 
If you need someone to play with the "just the sled" full size eggfinder version, I'd be happy to volunteer.

I have a 4" Madcow Patriot with a nose bay built using the John Coker method (4" x 54mm centering ring epoxied into the cone, 4" coupler bulkhead attached to that using t-nuts and machine screws). I've got a couple of different antenna sizes I could play with (no stick antenna unfortunately).
 
I see 3 types of antennas on full size EFs: wire stick, stubby, and full size. For antenna support, you could put a little 'nub' sized for the stick, and the end user could simply sand/cut/file/dremel to fit their specific configuration. Maybe make the nub stepped so that the user would know where abouts to start fitting.

I like this as accommodating even my antenna selections would require multiple spacings. Something I experimented with in the first iteration was a removable nub (held on with 1 screw and a tab). I guess I could keep that a separate piece in case you bugger it you don't bugger the whole sled. Maybe 3 removable nubs with each kit to give a few shots at it, or accommodate different length antennas for different sized bays. The idea is for this to be as easily swappable as possible.

Gotta finish my L3 paperwork, then I'll be back at this.
 
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