75mm MD L3 Build

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Flyfalcons said:
Chop those and get a couple male/female sets of whatever you want to use. JST or standard JR servo plugs work great, and you can get connector locks for the standard JR plugs.
Click to expand...

What standard connectors have a locking mechanism to them?

I'll be experiencing high G's so I want to make sure the power connector stays together.
 
dixontj93060 said:
Personally I like the Molex .062 connectors: https://www.ebay.com/itm/2-circuit-...263407?hash=item33bd5c1fef:g:MhQAAOSwU9xUPDwG. Can usually pick these up locally if you have a Fry's nearby.
Click to expand...

I'll look into getting a few pairs of those. Thanks!

....Ugh. Not really related to building, but I just spent the last 30 minutes getting this little b**** out of my finger. Photo of tweezers and hand for scale.



It's that little black streak on the translucent piece of skin...

 
No matter what you use, duct tape and ziptie to the sled if going to extremes. Plus I take it you are going to be
doing this out West at a site that has a moderately large waiver radius. Technically if your rocket lands outside
the waiver radius it's a certification failure even if it survives. Food for thought. Kurt
 
Yep,I think the more surface area grabbed onto the better- just don't cover the baro sensor :)

It sounds silly but I use the hell out of hot glue in all my avbays. If you're holding something down with screws, spray a bunch of hot glue under it and screw it down- it'll prevent movement, dampen vibrations, and provide a lot of extra anchoring but still be removable.
 
caruolo said:
What standard connectors have a locking mechanism to them?

I'll be experiencing high G's so I want to make sure the power connector stays together.
Click to expand...

Servo plugs. The mechanism isn't built in but they are readily available.
 
Reinhard said:
Molex SL are wide spread types that uses latches. You can get them pre-wired from Doghouse Rocketry.

Reinhard
Click to expand...

I ended up using those from Doghouse, just didn't know what they were called.

Anyone have tips on gluing in the retainer? It's the last major construction step I have.
My idea was to slather epoxy inside the airframe where I would be putting the retainer, and slowly push and rotate the retainer into place.

Thoughts?
 
caruolo said:
I ended up using those from Doghouse, just didn't know what they were called.

Anyone have tips on gluing in the retainer? It's the last major construction step I have.
My idea was to slather epoxy inside the airframe where I would be putting the retainer, and slowly push and rotate the retainer into place.

Thoughts?
Click to expand...

This is correct, but must be JB Weld (or other high-temp, metal compatible epoxy).
 


Been busy with school, work, and my L3, but here she is!

Headed to BALLS later today, and plan to attempt my cert. on Saturday.

See you guys out there!
 
All the best of luck Alex....
The flight is going to go perfectly....

Teddy
 
Hope the cert flight goes well for you. Have a great trip to Balls anyway!

Just a couple of things you may want to watch out for. I see your telemetry is near your altimeters. Do plenty of testing on the ground with the telemetry running to check that there are no EMI problems. I have had a NC blow off with my rocket sitting on the pad. Problem was EMI between the telemetry Tx (higher power than what you are using though) and the altimeter.

Another possible gotcha is that many of the baro sensors used in altimeters are sensitive to light. Not normally a problem with them as the manufacturers normally put them on the bottom of the PCB which keeps the light exposure down (next to the sled). Small portholes (static ports) only periodically let in the sun as the rocket rotates. Your sled is clear which may allow light a bit closer to the baro sensors. A flash of light is interpreted as a change in pressure and can lead to unintended outcomes for the deployment.

Love the possibilities of 3D printing. Some people will tell you that it isn't going to work, especially if you are doing structural parts for rockets. Don't believe them! Do the calculations and the design properly and it will work. I have an ABS NC that I am taking up to a relatively tame Mach 1.2 in the next few weeks. It does take some time to learn what is possible with 3DP, but it opens up creativity enormously.

Again, good luck with the certification.
 
Forgot to mention. If you are concerned about battery connectors, like those pictured, coming out during hard accel just put a small dab of hot-melt glue between the connector and the sled. It holds in place nicely during the flight and is easily cut away afterwards to extract the battery.
 
Way to go BALLS out on the L3 certification .

Thanks for sharing the build with us ..very clean indeed . . .how about some pics from the playa and some quick and dirty altimeter report when flown ?

Kenny
 
I hear this one was a huge success.

Congratulations Alexis! I knew you were going to kill it.
 
Would love to hear a flight report! Question for you guys, while we wait- I've used only JST connectors on my flight computers, and have yet to really push any limits. The Dean's connectors are intriguing to me since they have greater surface area (and therefore more current handling), but I'm not at all clear on how these are soldered- is it just the little tab that gets connected to the lead? There doesn't appear to be a hole to assist with a mechanical connection prior to soldering, nor is there any "shape" to them to help with wrapping, or for grabbing onto the heat shrink. Any tips?
Other question- I use hot glue periodically as well (sealing passthroughs, prepping charge canisters, etc), but have avoided requiring it for flight prep, since I have only ever seen plug-in models, but this thread inspired me to search, so are you guys using something like this on the range? https://www.amazon.com/Pros-Kit-GK-368-Battery-Operated/dp/B00EY4ZA7Q? I don't know why I didn't think to look sooner! This will make prep of e-match charges and spot-reinforcement of av-bay wiring so much easier!
 
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That's correct. Deans Ultra plugs have simple flat plates to solder your wire onto. There is no crimping.
 
IMHO Deans plugs are way too large for this purpose (molex too). You can get JST extensions from Sparkfun that have a male and female plug. They snap together and hold tight. Even at 50g the amount of strain on the connectors is negligible. If you attach the wires to your sled a couple inches from the connector they aren't going to come apart.
 
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I always use JST's now...
Even for the airstart in Europa Express...
I think the tension it takes to yank them apart is consistent..

Teddy
 
It might help to provide a link, "JST" makes a ton of connectors. The ones I think of when I hear that are commonly used in R/C https://www.sparkfun.com/products/10501. Those aren't a great choice for rocketry IMO, as they pull apart with very little force. One of the other varieties may well be a good option.

On my recent setup for an Eggtimer Quantum, I used XT60, mostly because I had a bunch of them already and most of my lipos use them. They are oversized for this application, but they aren't very heavy and take a lot of force to pull them apart. If I were ordering new parts right now, I'd probably try XT30 as they are much smaller, but still have a strong connection. I believe Deans makes a mini type as well if you prefer those.

Most types will work if you provide some strain relief to prevent the G forces from pulling on them. That's probably a best practice for HPR anyway.
 
rharshberger said:
Not sure why they call it a DMS when it is actually like the LMS motors, prossibly the are cutting down the different nomeclatures they use. Technically a LMS is a DMS. ��
Click to expand...

They are different product lines from different eras, and use different material. I think Aerotech has basically phased out LMS except one or two motors that were too cool to kill off.

My understanding is that LMS is basically cheap RMS hardware that would not make the cut for multiple uses, whereas DMS is explicitly single use by virtue of being bonded and possibly ablating. DMS is supposed to require no assembly though the 75mm and 98mm versions need some basic work due to regulation and shipping practicality.
 
watermelonman said:
They are different product lines from different eras, and use different material. I think Aerotech has basically phased out LMS except one or two motors that were too cool to kill off.

My understanding is that LMS is basically cheap RMS hardware that would not make the cut for multiple uses, whereas DMS is explicitly single use by virtue of being bonded and possibly ablating. DMS is supposed to require no assembly though the 75mm and 98mm versions need some basic work due to regulation and shipping practicality.
Click to expand...

LMS is single use. They can be shipped with no hazmat thru US mail and they are still in production.

Loadable Motor System™

In 2006, AeroTech re-introduced the K250PW as its first Loadable Motor System™
(LMS™) motor. The LMS is a single-use motor in kit form that is assembled by the
user. The LMS concept was subsequently expanded
into the model rocket line of motors between 2006 and 2007 with the F20W/L,
F23FJ/L. F27R/L, F42T/L, G77R/L and the G79W/L. All the model rocket LMS kits,
including the G77R/L and the G79W/L, use all-disposable components and may
also be shipped via USPS Parcel Post without incurring a hazmat fee.
 

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