Yet another 5" Jart build thread - M power

ECayemberg said:

Claude,

Looking really nice! Exciting build so far; and looking forward to watching a screaming flight at Tstruck!

Very nice!

-Eric-

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Thank you sir. :cool2:

mannyskid said:

Okay, so mine won't meet an N10,000 for a long time, probably MWP (that's if I'll have time with school and everything).
Mine is probably going to fly at Thunderstruck as well, and probably with a 6G M840 White (because I've had it sitting in my motor box for a while too). I think we should drag race, because it is going to fly without the extension for that flight...



One question Claude, did 'ya bag it? Interesting approach, mine is similar except I'm only doing outter lays of carbon because I didn't want to widen the fin slots. Tim did give me one of the black Jarts, but I told him what I was going to punish it with and he took it away and gave me a normal one

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Drag racing two 5" Jarts on M motors??? Sounds good to me.

Preliminary Rocksim file. Weights will be finalized later, but I thought I would share.

View attachment jart.rkt

Claude,

Looking forward to seeing this fly at TS4, looking really good! Will you be there all (3) days?



Justin

mannyskid said:

One question Claude, did 'ya bag it?

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Manny,

Sorry, I overlooked that part of your post. No, I did not bag it. Just standard reinforcement method.

Justin,

Thank you. I am planning on Friday and Saturday for now.

More pics of the av-bay setup, with the altimeters mounted.

Others may have more insight on this, but this is potentially a high vibration environment for the Raven. The piece that the sled is epoxied to is free floating on the motor and could experience chattering. Not sure the implications it could have on deployment and what not, but I assume it will pollute your acceleration data to some extent.

Anyone do something similar and have it work okay?

patelldp said:

Others may have more insight on this, but this is potentially a high vibration environment for the Raven. The piece that the sled is epoxied to is free floating on the motor and could experience chattering. Not sure the implications it could have on deployment and what not, but I assume it will pollute your acceleration data to some extent.

Anyone do something similar and have it work okay?

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Good observation.

I have had some rockets where the altimeter / accelerometer were connected to the MMT without any issues. In this case the av-bay section will slide over the motor, but there will be two threaded rods that will secure this sliding part to the fincan. In other words it is removable but will be secured in place during the flight. I also plan on adding some tape to the motor casing if it is too loose, to prevent side to side movement, or wobbling of that section.

Is heat ever an issue when mounting electronics that close to the MMT tube?

Whodunit13579 said:

Is heat ever an issue when mounting electronics that close to the MMT tube?

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Time to revive this thread!

Whodunit13579, Good observation.

I do not see this as an issue. There is first the motor mount tube, then the mounting plate, then the nylon spacers, then the altimeters. I doubt the heat from the motor will be an issue. In addition, I have flights on two other rockets where the altimeters were mounted between the motor mount tube and the airframe in a similar fashion, all without issues. Hopefully this one will work well too.

I have not done a whole lot on the rocket since the last update, but again, what is left is mostly finishing. With the cold temps we keep having it is hard to find an opportunity to paint the fins and spray a clear coat on the rest of the rocket. Despite all that, I will be ready for Thunderstruck! More importantly, a couple weeks ago I had an epiphany (or some will say an episode of lunacy): If I am going to fly this thing on an M motor, why not fly it on a ferocious M. :cool2:

Hence I decided to replace the M-2150 with the M-3700 White Thunder :shock:. Mach 2 in 1.6 seconds should be pretty cool for a 5 inch Jart.

I think I also have a name for it: "Sudden Jart"

nh4clo4 said:

Time to revive this thread!

Whodunit13579, Good observation.

I do not see this as an issue. There is first the motor mount tube, then the mounting plate, then the nylon spacers, then the altimeters. I doubt the heat from the motor will be an issue. In addition, I have flights on two other rockets where the altimeters were mounted between the motor mount tube and the airframe in a similar fashion, all without issues. Hopefully this one will work well too.

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For some reason, this comment sparked an idea in my head: I have a 4" LOC Bullet that has a Featherweight Parrot located about 1/2" away from the 38mm motor mount. The altimeter is on a plywood sled in between two fins, and subsequently has a hatch over the top of the cavity retained with 4x pop-rivets at the four corners. This entire section has a 4" coupler installed, so it's fairly well insulated.

Then I thought "wait a minute, Featherweight units measure temperature, let's have a look!



This graph shows the Accel plot vs. the Temperature plot. You can see the 1.5s burn time on the left, and the green plot for the temperature that increases by only about 0.5 degrees following the burning of the motor, over the next 9 seconds or so.

Keep in mind that the 76mm motor will put out a lot more heat, but I HIGHLY doubt that heat will be an issue. Be sure to provide feedback on the increase in temperature experienced by the altimeter(s)!!

Now, this issue is something a little more interesting. I am not fully up to snuff on this theory, actually not up to snuff at all, so I will mention it and hope that the educated individuals make themselves known!

From what I understand, a magnetic field is generated by a rocket motor as it burns. Strength is determined by the amount of mass flowing through the motor (I think) and it becomes more severe as motor size increases.

I think that I recall Adrian of Featherweight state that the Delta that they flew a few years ago actually experienced toggling of the magnetic switches as a result of this phenomenon.

Butalane, Daveyfire, MClark, and Adrian will have more knowledge on the subject.

patelldp said:

Now, this issue is something a little more interesting. I am not fully up to snuff on this theory, actually not up to snuff at all, so I will mention it and hope that the educated individuals make themselves known!

From what I understand, a magnetic field is generated by a rocket motor as it burns. Strength is determined by the amount of mass flowing through the motor (I think) and it becomes more severe as motor size increases.

I think that I recall Adrian of Featherweight state that the Delta that they flew a few years ago actually experienced toggling of the magnetic switches as a result of this phenomenon.

Butalane, Daveyfire, MClark, and Adrian will have more knowledge on the subject.

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Wow! Never heard of that one. Thank you for bringing this up, it could prevent a major disaster.

OK, so I posted a question about the magnetic field in another thread and was told the motor burn should not create a magnetic field and therefore should not impact the functionality of the magnetic switches.

With that in mind I have made the executive decision eyeroll to move forward with the current design.

The M3700 reload should be here this week. :drool:

nh4clo4 said:

The M3700 reload should be here this week. :drool:

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I like what i see Claude.......Please fly it on Saturday, sometime in the early afternoon. (After i get there.) Please.........:grin:

I am sure that can be arranged. :wink:

Ohhhh... I can't wait to see this thing fly, and the M3700 will be awesome!

BOOOOOOOOOOOOOX !!!

The AP has arived.

I never saw this fly at thunderstruck... Did it???????

This was one of the coolest flights I've ever seen if not the coolest.

[YOUTUBE]-MYvMyGeTGI[/YOUTUBE]

I have been smiling since yesterday :grin:

I just (finally) downloaded the data, and I have an even bigger smile on my face.

Altitude 14,546 feet
Accel 52Gs
Decel right at motor burnout -15Gs
Speed... 1601 mph at 1.9 seconds into the flight, at about 3,000 feet.


I DID hit Mach 2 with my Jart :grin: :grin: