Shock cord mount printed bay, Anyone make?

[Nick@JET]

I am looking for a mounted bay for GPS. Something along the lines of a plastic printed small bay enough for a battery, the smallest screw switch and an RTx, bullet or torpedo shape as to not catch on anything. Two open slots to put over a cord and zip tie slots.

This would be a very quick change from rocket to rocket.

Does anyone here currently make this, if so I’m interested, if not I may have my Makerspace friends make.

I’ll draw up what I’m thinking and post but with my busy life, don’t want to reinvent the wheel


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[MikeyDSlagle]

Neat idea. What GPS unit?
Rather than zip tie to harness, have some sort of clamp implemented that uses screws to tighten against the harness.

 

[Nick@JET]

Good idea on the clamps
I would say RTX, then RTx, EF, EF mini should then fit as well, even a spot for Com Spec, although if that’s used as a backup maybe should locate on a different harness


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[Cl(VII)]

Good idea on the clamps
I would say RTX, then RTx, EF, EF mini should then fit as well, even a spot for Com Spec, although if that’s used as a backup maybe should locate on a different harness


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I'm going to make a shameless plug for my EFmini mounts here: https://www.rocketryforum.com/showt...gFinder-Mini-Sleds-and-All-Thread-Free-Mounts

Also, Missileworks is offering a similar mounting system for the T3 tracking system: https://www.missileworks.com/store/#!/T3-Modular-Mounting-Systems/c/25679088/offset=0&sort=normal

Neither of these have switch holes, but the shock cord mount sleeve can be attached with as little as one screw; so you open it, connect the battery, close with screw and fly.

 

[afadeev]

I am looking for a mounted bay for GPS. Something along the lines of a plastic printed small bay enough for a battery, the smallest screw switch and an RTx, bullet or torpedo shape as to not catch on anything. Two open slots to put over a cord and zip tie slots.

This would be a very quick change from rocket to rocket.

Does anyone here currently make this, if so I’m interested, if not I may have my Makerspace friends make.

Yes - Chris Bender made one, and I'm using it with EggFinder Mini GPS:
https://www.rocketryforum.com/showt...ized-EF-sleds-available&p=1704713#post1704713

EggFinder GPS info:
https://www.eggtimerrocketry.com/page45.php

Everything fits perfectly into my Formula 38, and looks like this:




a

 

[MikeyDSlagle]

I can mess around with CAD when I get a chance but don't know when that would be, maybe later tonight or tomorrow. When I get caught up and need something to do, I am always looking for something to make in CAD. But I am not familiar with the RTX, RTx or Com Spec. You would have to post some dimensions.

Would you want it to where they can be mounted via screws? On standoffs? If that's the case, hole spacing would be needed as well.
Or wrapped in bubble wrap and just laid in there? Like a simple capsule. That would probably be the easiest.
Size restrictions? Max diameter and length?

Or:
https://s7d1.scene7.com/is/image/BedBathandBeyond/6286613453276p?$478$

LOL

 

[pondman]

I am looking for a mounted bay for GPS. Something along the lines of a plastic printed small bay enough for a battery, the smallest screw switch and an RTx, bullet or torpedo shape as to not catch on anything. Two open slots to put over a cord and zip tie slots.

This would be a very quick change from rocket to rocket.

Does anyone here currently make this, if so I’m interested, if not I may have my Makerspace friends make.

I’ll draw up what I’m thinking and post but with my busy life, don’t want to reinvent the wheel


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Catch up with me at MWP and I will show you what I have done........

 

[Nick@JET]

I'm going to make a shameless plug for my EFmini mounts here: https://www.rocketryforum.com/showt...gFinder-Mini-Sleds-and-All-Thread-Free-Mounts

Also, Missileworks is offering a similar mounting system for the T3 tracking system: https://www.missileworks.com/store/#!/T3-Modular-Mounting-Systems/c/25679088/offset=0&sort=normal

Neither of these have switch holes, but the shock cord mount sleeve can be attached with as little as one screw; so you open it, connect the battery, close with screw and fly.

Was hoping you would chime in Chris, Love this setup and will likely buy one - waiting on time to figure out the nose cones I need because they are already closed up. Also I Only gave the RTx. Probably just need to buy one of your setups anyway and EF but the EF won’t happen for awhile. The quick change of a tracker has always been issue for me except for the Garmin Astro - throwing in NC works good but must be a 3” or larger cone.

Having said that, it’s not quite what I’m looking for this application. Was looking something that has smooth edges as to not interfere with shock cord while it’s deployed and spinning. Then I cut 2 zip ties, boom right on the other rocket without disturbing the NC. This will go onto any shock cord probably 38 or 54 on up easily and fast- so special modification of any kind.


Mikey - I’m traveling right now and don’t have any dimensions or picture yet, just putting a feeler out there, thanks for your willingness to help.


Gary, yes I’ll look you up this weekend!


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[Cl(VII)]

Was hoping you would chime in Chris, Love this setup and will likely buy one - waiting on time to figure out the nose cones I need because they are already closed up. Also I Only gave the RTx. Probably just need to buy one of your setups anyway and EF but the EF won’t happen for awhile. The quick change of a tracker has always been issue for me except for the Garmin Astro - throwing in NC works good but must be a 3” or larger cone.

Having said that, but it’s not quite what I’m looking for this application. Was looking something that has smooth edges as to not interfere with shock cord while it’s deployed and spinning. Then I cut 2 zip ties, boom right on the other rocket without disturbing the NC. This will go onto any shock cord probably 38 or 54 on up easily and fast- so special modification of any kind.


Mikey - I’m traveling right now and don’t have any dimensions or picture yet, just putting a feeler out there, thanks for your willingness to help.


Gary, yes I’ll look you up this weekend!


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Gotcha. I was after shock cord mounting too. That was what originally got the sled design going. Doesn't hook on like you suggest, and would be a tight fit in a 38 tube.

Is one of the the below kinda what you are talking about. They differ only in that one has a recess for the cord to travel in. I'm trying to understand the ask, because it may be really straightforward to modify what I already make.

 

[Nick@JET]

Gotcha. I was after shock cord mounting too. That was what originally got the sled design going. Doesn't hook on like you suggest, and would be a tight fit in a 38 tube.

Is one of the the below kinda what you are talking about. They differ only in that one has a recess for the cord to travel in. I'm trying to understand the ask, because it may be really straightforward to modify what I already make.

Yes that’s it! Just need to make the ends like a torpedo so nothing can grab onto it. Dare I say like a cocoon of sorts..

Forgive the poor picture on a napkin while in a car


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[Cl(VII)]

The issue I think would be making it universal while keeping it a reasonable size. The trackers vary in size a great deal from the RTx down to the EFmini and Comspec. If you want it to fit in a 38 tube that is going to be really tough. I'm sure I could make something for the EFmini that would do this, but the RTx would be much more difficult (and much longer).

 

[afadeev]

Yes that’s it! Just need to make the ends like a torpedo so nothing can grab onto it. Dare I say like a cocoon of sorts..View attachment 331153

You may be over-estimating the amount of real estate you have to work with in sub-1.5"/38mm airframe rockets.

First of all, the sled has to be wide enough and long enough to in-line accommodate: {antenna | circuit board | wiring connection | battery | attachment point/anchor }. Figure at least 7-10", or longer, depending on the type of the antenna you use. If the sled goes inside the main airframe/booster, you will want to fully insulate the GPS circuit board from the ejection charges, so plan on fully enclosing the entire antenna. Then add another 5-8" for a packed parachute, then another 8-12" reserved for the H/I 29mm motors (I assume you intend to fly big motors if you are worried about recovery).

Next thing you know, you will only be able to fly your enclosed sled in rockets with 20-30+" long airframes/boosters. They do exist (e.g.: Madcow 1.6" Go Devil) , but that's way longer than 90+% of the commercial rockets you are likely to own or consider buying.

An arguably cleaner and lighter (don't need full hermetical enclosure, just the mounting frame) solution is placing the GPS sled into the nose cone. Now you can fly in the vast majority of mid-power rockets, and all you need is a 33mm ID coupling tube to be permanently attached to the root of the nose cone via an epoxied centering ring. Then you can move your (or Chris Bender's) GPS sled between multiple nose cones/rockets, and off you go. The only remaining concern is making sure that the battery lasts long enough across multiple flights. Good problem to have!


a

P.S. Having said all that, I did also buy the cylindrical cover for Chris's sled, just in case I need to throw the tracking into one of my larger 2+" diameter rockets, by attaching it to the shock cord. This buys me a "plan B" to fly Eggfinder GPS inside larger airframes for which I have not have yet fabricated a nose cone recepticle for the eggFinder GPS sled.

 

[MikeyDSlagle]

Something like this?



Scratched it together. Not very roomy but it is 7" long. A small 2 cell Lipo will fit and so should an Eggfinder, but I haven't double checked for sure. Not sure on the printability either.

 

[Cl(VII)]

That is a very cool looking solution. I was tinkering with this too, and there is one problem I can't get away from using zip ties to tie onto the cord. That is, unless the zip ties are at the very end, you run the risk of the cord doubling back and wedging between the case and the cord against the zip tie. I'm not sure how that would play out if it happens during a recovery, or if it would be an issue at all.

Edit: I don't want what I wrote to sound disparaging. I think this is a solvable problem. I'm just not seeing the elegant solution at the moment.

 

[MikeyDSlagle]

I think I get what you are saying and having the flat part extend farther toward the ends, like the doodle on the napkin, would help. But I don't see it being an issue. This was my first time messing with ellipsoids and wasn't really sure what the heck I was doing. The only way to make it a flat bottom will limit inside space and it will not fit into a 38mm tube. This one will be iffy with zip ties, the harness, and my two screw pylons, but the pylons may can be eliminated; the zip ties and the screws on the end would hold it together. But the OP hasn't mentioned 38mm I don't think. Making it to fit 54mm+ should be fairly easy...I think.

How difficult would something like that be to print anyway? I don't have a printer and just get random stuff printed from time to time on 3dHubs.

 

[Cl(VII)]

I think I get what you are saying and having the flat part extend farther toward the ends, like the doodle on the napkin, would help. But I don't see it being an issue. This was my first time messing with ellipsoids and wasn't really sure what the heck I was doing. The only way to make it a flat bottom will limit inside space and it will not fit into a 38mm tube. This one will be iffy with zip ties, the harness, and my two screw pylons, but the pylons may can be eliminated; the zip ties and the screws on the end would hold it together. But the OP hasn't mentioned 38mm I don't think. Making it to fit 54mm+ should be fairly easy...I think.

How difficult would something like that be to print anyway? I don't have a printer and just get random stuff printed from time to time on 3dHubs.

It would probably need supports in a couple places, but I think it would be doable. With a few tweaks you could probably eliminate the need for supports. There is really nothing wrong with using supports. I just don't prefer them because I've never really dialed in the settings for my preferred filament, so anywhere I use them ends up looking too rough for my liking. Also, my print bed moves (Y-axis) so sometimes a support will shake loose before it is used, and then the print is often ruined.

As for my concerns with the cord wedging, you are probably right that it isn't an issue. I'm a worrier, especially when I'm making something for other people.

I like the elipsoid look too. I way working more "bullet train" shape.

 

[MikeyDSlagle]

The harness could get wrapped just wrap and maybe snap the zip ties but like you say, zip ties farther out would help. But a hard jolt could easily snap the ones on the ends and possibly even the capsule itself. A small kevlar lanyard would be a good idea.

I see a few improvements that can be made. I know I can squeeze out a bit more internal space, but not much. I will fiddle with it some more and see what I can come up with.

 

[Mendal]

This is a very interesting question, I might have to put a bit of time to seeing if I can help solve it. I've gone to a sled that I fit into my nose cones, I want to refine it to more of a universal system that I can move from rocket to rocket but right not its a sled that bolts to the nosecone bulk head. Maybe I should do a write up on how I make removable nosecone bulk heads, basically I print a ring with nut traps that is epoxied into the nosecone, then the bulk head is bolted to the ring. prior to closing up the NC bulk head I connect the battery to my gps tracker which are both attached to a sled attached to the bulkhead.

Chris I used to avoid supports, still actual do as much as possible, but I have found switching to simplify3D has improved my use of supports. in simplify you can manually control the placement of supports. Also the supports it creates breaks away much more cleanly than anything I sliced with cura. Hit me up if you would like to know more.

Mikey, nice start of the design there I'm interested to see where you go with it.

 

[Nick@JET]

Thanks for looking to into this guys - I like the bullet design.
Originally what started this is I have some NC already closed up and the RF tracker peeps tape the transmitter right to the shock cord - easy peasy but I would also prefer some protection. So this would just make it so easy - tape or zip tie to cord and done. If it doesn’t fit into smaller than 54, so be it, then I’ll do Chris nose cone kit for those rockets

I’ve been in contact with Chris via PM to see what we can come up with.
Keep the ideas coming ! Thanks for you inputs.

PS I’m not interested in selling / marketing these, simply want one that I don’t think exists.


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[ksm2001]

Here is a sled I designed to fit the Egg Finder. I designed the sled to fit the cardboard tube the 29mm CTI motor reloads come in. The cap threads onto the sled after the cardboard tube is installed. Use electricians tape to secure it to shock cord.

I printed using supports, If you position the sled in your slicing software as it shows in the photo with the battery it will use the least amount of supports.







View attachment 34mm Egg Finder GPS Sled.stl

View attachment 34mm Egg Finder GPS Cap.stl

 

[Cl(VII)]

First attempt at an EFmini "torpedo" underway. I'll be asleep before this thing is done, so I'll see if everything fits tomorrow.

 

[MikeyDSlagle]

Cool. I'll wait and see how it turns out before I dive off into redesigning mine. Got a few ideas in my head but if yours works, no need for me to keep fiddling with it, except maybe to eliminate the need for zip ties.
Digging through my fleet in preparation for Saturday's launch, I realized something like this will be the only way I can add tracking to my Wildman Sport without stretching the rocket.

 

[Cl(VII)]

Cool. I'll wait and see how it turns out before I dive off into redesigning mine. Got a few ideas in my head but if yours works, no need for me to keep fiddling with it, except maybe to eliminate the need for zip ties.
Digging through my fleet in preparation for Saturday's launch, I realized something like this will be the only way I can add tracking to my Wildman Sport without stretching the rocket.

I'll post some pics tonight. I came out pretty good for a first crack. I need to make the zip tie channels deeper across the top, and make a few other tweaks. Battery and EFmini fit, but it ends up about 7,5" long. I am going to change it from banded with zipties, to loops to thread through.

 

[Nick@JET]

I'll post some pics tonight. I came out pretty good for a first crack. I need to make the zip tie channels deeper across the top, and make a few other tweaks. Battery and EFmini fit, but it ends up about 7,5" long. I am going to change it from banded with zipties, to loops to thread through.

Awesome! Means I have to buy an EF now . Will the loops still be a quick change between rockets?


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[Cl(VII)]

Awesome! Means I have to buy an EF now . Will the loops still be a quick change between rockets?


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Will connect with up to 3 zip ties directly to the shock cord. Cut the ties, and change cords. We'll see how it turns out.

 

[MikeyDSlagle]

How'd it work Chris?

 

[Cl(VII)]

I need to adjust one of the parts. The slope was too steep at one end. Try again this evening.

 

[Cl(VII)]

OK, here is what I got. It does not have a switch hole. It is 25 mm tall, 32 mm wide, the length is about 7 3/4" and the hole spacing for the zip ties is 1/2" (shown is a 7/16" kevlar cord). Still needs a few tweaks; one more screw spot added at the other tip to make sure it doesn't gap at all, move zip tie tiedown toward tip at one end, recenter other zip tie point, but basically done.



It is obviously too long to be a solution for a space is premium MD rocket...the NC is still your best real estate there, but if you want to quickly slap a tracker (or backup tracker) in a rocket with some space this would probably work.

 

[GrouchoDuke]

Very cool, Chris. Nicely done.

 

[cwbullet]

Chris,

That is peachy keen.