L3 Build - Spikey

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Wow how did I miss this one. This is how I plan on doing my L3, good on you for doing something, risky but calculated and interesting. The tee nuts are something I would pick up if you ever plan on selling them. Also what servos are you using for the canards and I am assuming you will have a 2D or 3D axis controller, if so will you be running in 2D just for yaw and pitch or 3D including roll?
 
Wow how did I miss this one. This is how I plan on doing my L3, good on you for doing something, risky but calculated and interesting. The tee nuts are something I would pick up if you ever plan on selling them. Also what servos are you using for the canards and I am assuming you will have a 2D or 3D axis controller, if so will you be running in 2D just for yaw and pitch or 3D including roll?

I made a few hundred Tee nuts/counter sink washer pairs and then treated them so they would stick to epoxy, figured I would see how others liked them. I am using Hitec HS-5485HB servos with a bit of gear reduction, all from Servo City. Eventually I will run 3D control, that will come later. I need to get the rocket flying nice a stable before trying the active control. Using a pair of SCC1300 gyro's for the primary stabilization feedback.

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I made a few hundred Tee nuts/counter sink washer pairs and then treated them so they would stick to epoxy, figured I would see how others liked them. I am using Hitec HS-5485HB servos with a bit of gear reduction, all from Servo City. Eventually I will run 3D control, that will come later. I need to get the rocket flying nice a stable before trying the active control. Using a pair of SCC1300 gyro's for the primary stabilization feedback.

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Thanks for the information, this is something I have been looking at, from an early preliminary perspective, and want to go down a similar road for my L3, which is likely 2 years off. I would love to pick your brain and learn from your mistakes. When it comes to the canards, how are you balancing the hing point, also how are you attaching the canards to the hinge pins and are you using a bearing through the airframe, any insight you're willing to impart on the mechanics of the canards is appreciated. I am very impressed with the staging technologies you're using, quite a step up from a basic timer.
 
I don't have much to add, but WOW, I'm intrigued! Found this looking to see what others have done with RJ45 jacks on rockets, as I have a few, and am struggling fitting all my JST-type connectors in my av-bay. Want to rewire with 2 RJ45, and now have the confidence that it will work!
Looks like yours, Random Flying Object, are going to be exposed to BP charge, or am I misreading the photo of your av bay bulkheads?
 
I don't have much to add, but WOW, I'm intrigued! Found this looking to see what others have done with RJ45 jacks on rockets, as I have a few, and am struggling fitting all my JST-type connectors in my av-bay. Want to rewire with 2 RJ45, and now have the confidence that it will work!
Looks like yours, Random Flying Object, are going to be exposed to BP charge, or am I misreading the photo of your av bay bulkheads?

No, my RJ45's are not exposed to a BP charge. Take a look at the photo I have attached. My BP charges are inside of the 4" tube and the RJ45's are in the annular space between the 4" and 5" tube. The picture shows only the 4" chute tube coupler, another 4" tube runs the full length on the inside of the 5" recover body section. My chute tube containing the BP is completely closed off from the surrounding area inside of the 5" main body tube. All of the mass terminals, RJ45's and SMA's are in a clean area. I DO NOT recommend using RJ45's in a BP charge area, there is no good way to clean the connections, at least that I have found. In BP areas I stick with a positive clamping contact or good pin and sleeve connectors. Another note about RJ45's, be careful of the orientation and cable stress. The pins themselves have very low mass, but the connector and cable can get ripped apart with enough g force. Go check out Mouser, Digikey or Allied Electronics, you can shop for connectors until you pass out. Good luck with your project.

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No, my RJ45's are not exposed to a BP charge.

Thanks for the clarifying explanation and accompanying photo- makes sense now that I look back, the 4" bulkhead now fits in with what I was (or wasn't) seeing. My jacks will be on the av-bay sled, so no exposure to residue for me, but my fear was exactly as you point out- the mass of the jack and plugs. I am planning for a strong mechanical connection between the punch-down keystone and the sled, oriented as you have, in line with the Z-axis. It's encouraging to see someone with so much more experience already there!
 
Getting closer. Nearly time to start populating the AV bays and installing the recovery system.

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Epoxied the glass to fill in all the small imperfections and fillet the tee nut inserts. I was very pleased with the result.


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Epoxied the glass to fill in all the small imperfections and fillet the tee nut inserts. I was very pleased with the result.


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That does look nice! What kind of epoxy did you use?

And did you pass the test (or rather, did you get any of the questions wrong)?

Jim
 
I gotta ask, what's the KitchenAid stand mixer used for?


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That does look nice! What kind of epoxy did you use?

And did you pass the test (or rather, did you get any of the questions wrong)?

Jim

I did pass, not sure if I got any wrong. For anyone in high power rocketry I highly recommend getting a HAM license. I put it off as long as I could. It is much easier and interesting than you may think. Enabling more options for tracking and the use of a higher power radio and repeater when you are way out in the field is a plus. For those of you thinking of getting a license I highly recommend hamtestonline, it is a great site and a great way to prepare for the test.

Epoxy = West Systems, I wanted to use Proset but I don't have an oven that big.



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I can't recall reading the specifics on the usage of the breakaway wiring harness and how it will work, can you expand on this?

The harness in the picture runs between the aft AV bay and the forward AV bay, in the annular space next to the recover tube. The recovery tube is a 4" tube containing the drogue and main parachutes, it is housed within the 5" main body tube. The bulkheads for the two AV bays sit on each end of the recovery tube. When the main tube separates, causing the recovery tube to separate, the harness must breakaway from the aft bulkhead to allow full separation and chute deployment.



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The harness in the picture runs between the aft AV bay and the forward AV bay, in the annular space next to the recover tube. The recovery tube is a 4" tube containing the drogue and main parachutes, it is housed within the 5" main body tube. The bulkheads for the two AV bays sit on each end of the recovery tube. When the main tube separates, causing the recovery tube to separate, the harness must breakaway from the aft bulkhead to allow full separation and chute deployment.



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Are these the same bulkheads with the RJ45 jacks, if so are you removing the lock tabs, if so how are you mitigating the cable from popping out?
 
Are these the same bulkheads with the RJ45 jacks, if so are you removing the lock tabs, if so how are you mitigating the cable from popping out?

The RJ45's connected to the forward bulkhead have tabs and click in to place as usual. During acceleration the cable harness is pulled down and the tabs have stress on them.

The RJ45's connected to the aft bulkhead have the tabs removed. The connector has a good friction fit and requires a bit of force to disconnect. This connection can be broken by heavy deceleration or separation for chute deployment. The connectors do not spontaneously pop out, the friction fit seems good enough to maintain the connection. It is possible that extreme vibration could cause an issue. Hence this connection is only used for non critical data acquisition during flight and for ground support on the pad.

Hope that clears it up.


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The RJ45's connected to the forward bulkhead have tabs and click in to place as usual. During acceleration the cable harness is pulled down and the tabs have stress on them.

The RJ45's connected to the aft bulkhead have the tabs removed. The connector has a good friction fit and requires a bit of force to disconnect. This connection can be broken by heavy deceleration or separation for chute deployment. The connectors do not spontaneously pop out, the friction fit seems good enough to maintain the connection. It is possible that extreme vibration could cause an issue. Hence this connection is only used for non critical data acquisition during flight and for ground support on the pad.

Hope that clears it up.


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You have obviously put a great deal of thought into this build, very impressive and looking forward to seeing more on it.
 
Assembly of the fore AV bay, OSD & flight computer boot test, and fully assembly fit check.

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What type of disconnect are you using for the retract system at the pad. I assume you will have a air tank at the pad to hold pressure to the retract cylinder. Most retract systems I have worked with have a turn lock system.
 
What type of disconnect are you using for the retract system at the pad. I assume you will have a air tank at the pad to hold pressure to the retract cylinder. Most retract systems I have worked with have a turn lock system.

Self contained pneumatic system controls retracts, stage separation and primary recovery separation.

No pneumatic disconnects at the pad, only electrical.



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