Build a rocket around the motor "The J Rider"

I have build most of my rockets because i'm interested in the kit. Sometimes its just that life will not be complete with out it. So far all of my HPR rockets till now have one small design flaw most through no fault of my own due to size or ejection baffles, making my selection of motors limited.

This will be the first time I will build a rocket to fit a motor, of course I will add design elements that I been wanting to see in a rocket. Only problem really is the motor hasn't even been certified yet, soon though soon. The Loki 38/1200 J-1127.

My initial OR sim shows the rocket reaching 1400 ft per sec with the 38mm J-1000 that is certified. I'm sure the rocket will need to be fiber glassed or built from glass tube to stay together. The design is not finalized but the basic shape is what I'm after, how its built and exact lengths are still being tweaked. The OR file will give you the basic idea.


I have done some slow motion studying of this video and as far as I can tell this motor is producing roughly 6 feet of flame that is more than 12 inches in diameter!
:headbang:
I can some it up in two words, I got to have it! err humm...


TA

[video=youtube;ns9uFMzkRIo]https://www.youtube.com/watch?v=ns9uFMzkRIo[/video]

View attachment TLJR.ork

I too need to make a rocket which will fit the 38/1200. I MUST have that Tropical Cocktail motor.

Did you see the red 1200? Its a baby K!


TA

Awesome design, TA.
Those Loki 1200 motors look INSANE!

I'm looking forward to seeing you launch one of these!

Alex

I rounded up all the parts and got to building, the bottom tube is already glassed and drying. I also have the fins and rings attached to the motor tube. I should have the upper air frame gassed by tomorrow. Only parts left to make is the transition and the AV bay.


TA

Glassed the upper tube today, and put some final touches on the OP file. I still have to tweak the final weight just as soon as I get the last of the parts finished and weighed. You cant really see it in the pictures but I have the fins sanded to a semi airfoil.

View attachment TLJR.ork

I'm actually surprised more folks don't do precisely this > Design the rocket around the motor <.

With Rocsim or OpenRocket it's so easy to play "What-if" and try out unlimited combinations until you are satisfied. I have done this a lot over the past couple of years, and it has worked out very well. I'm currently building an upscale BT80 Cherokee D clone designed specifically for the Cessaroni I-204 29mm 6 grain.

Design the rocket around the motor = Smart, very smart !!! :dark:

Well I have the tubes all glassed and the transition made. I also have the bottom tube glued in place, and added an extra piece of tube to the the inside of the bottom to beef it up a bit and give some backing to the fin slots that I cut out.

TA

Here is the dry fit.



TA

scsager said:

I'm actually surprised more folks don't do precisely this > Design the rocket around the motor <.

With Rocsim or OpenRocket it's so easy to play "What-if" and try out unlimited combinations until you are satisfied. I have done this a lot over the past couple of years, and it has worked out very well. I'm currently building an upscale BT80 Cherokee D clone designed specifically for the Cessaroni I-204 29mm 6 grain.

Design the rocket around the motor = Smart, very smart !!! :dark:

Click to expand...

It might be smart, but it's a lot harder to design the rocket for a range of motors. A 38mm L1 for example. Something that flies low enough on 29mm H128W to fly in 15-18 mph winds so you can still fly without loosing it, or push a mile high with an I435T on those days with no wind. I think having one rocket you can fly on multiple motors so you can adapt the flight to the site size/conditions and weather/wind conditions is much smarter. And you have to be smart enough to build it right by setting reasonable and workable limits. H and I may be the smarter choice then going for G - J ranges. Of course, you also have to be smart enough to fly the right motor in the right conditions. That's a whole other conversation. After 10 years, I've had a whole lot of "that was dumb!" moments to prove it.

Here is the J Rider just in primer, the AV bay is all but done. I still haven't thought of a final paint scheme yet, most likely a florescent pink and checker board pattern.


TA

It's all done minus the laundry and name, I just need to decide on what to call it. I'm thinking MAXX J or J Rider. This would be the first time I'm at a loss on what name to give a rocket.

Anyway if all goes well I'm going to try and launch it on the 21st of Sep, that is if we don't get rained out.


TA

Good luck with the flight, TA. Unfortunately, I wont be out there . ACT prep class that morning and all. Try and get some good pics! What's she going up on first?

Alex

thobin said:

It's all done minus the laundry and name, I just need to decide on what to call it. I'm thinking MAXX J or J Rider. This would be the first time I'm at a loss on what name to give a rocket.

Anyway if all goes well I'm going to try and launch it on the 21st of Sep, that is if we don't get rained out.


TA

Click to expand...

Love the paint scheme! I vote for J Rider as the name.

Aksrockets said:

Good luck with the flight, TA. Unfortunately, I wont be out there . ACT prep class that morning and all. Try and get some good pics! What's she going up on first? Alex

Click to expand...

What? Aww man how am I ever going to give your chute back? Sorry only have my phone camera and unless you are five feet away it blows. I may go with a Loki J-320 or an I-405.

rocketgeek101 said:

Love the paint scheme! I vote for J Rider as the name.

Click to expand...

Thnaks, i'm leaning towards J RIDER.


TA

Go with the Loki J320. It's an great motor with a nice red flame and a 2.5 sec. burn. I burned one at Airfest and I'm going to attempt a mile high on the 28th. Can you post any pics of your av-bay set up, and what was the final weight? Cool paint job btw.

Thanks, the AV bay is being reworked as we speak and with out electronics installed it weighs 61.6oz, with the motor its 88.5oz. It sims to just over 4300ft. As soon as I finish the AV bay I post it.


TA

In all honesty, I always figured ALL HPR rockets were built around the motors. I mean let's face it, you are limited with your aesthetics unless it's with the finish job. Most all HPR rockets I have seen are simple by design. They sort of have to be. This is by a LPR designers point of view of course.

Ok I finally got to launch this rocket we had a great day out on our field no wind not to hot. I opted to send this bad boy on its maiden voyage in style and I flew it on the Loki J-1000 White. I figured its not called the J Rider for nothing why not use the baddest J on the market!

Well the up part was spectacular the down part not so much, I had a high velocity deployment and according to the data from the altimeter and overly energetic deployment charge. Combined together meant a shredding of the recovery laundry and the subsequent fall to earth which surprisingly looks to have caused the least part of the damage.

Unfortunately for now my camera is not connecting to my computer for some reason so a pictures will have to be added tomorrow. I do have a video that Alex took for my of the launch.



TA
[video=youtube;Xwnk4fQk6Lo]https://www.youtube.com/watch?v=Xwnk4fQk6Lo[/video]

Well after a night of looking over the data from the altimeter, the motor ejection went off while it was still going 260ft per sec. Which was only half the problem from the same data it shows the the AV suddenly accelerating which I have concluded was the ejection charge going off and shooting the AV bay forward, not only picking up speed but gaining a spike in altitude which leads me to believe that the rocket was still pointed up, a lack of any zipper would support that or zipper type damage.

The big problem is the amount of speed that spiked at this event, I think the ejection charge was overly energetic and only added to the problem. There had to be one wicked of a snap back because a fin was torn off a rail button almost bent off and a nice gouge from the nose cone left on the body tube. The eye bolt was stretched out and the Kevlar shock cord while intact was shredded pretty bad.

The chute deployed at one point during all this and helped work the body over before it shredded and floated off alone never to be seen.

TA

So the lessons that were learned ground test your ejection charges, I did use a grain calculator but I guess my numbers where off. Weld or use a forged eye bolt, on these high speed flights let the altimeters do the eject at apogee. And zip ties will not hold a battery no matter how tight you think it is.

The simulation software I guess can only take you so far, my projected altitude for the motor and rocket where only 4800ft and it made it to 5711 before it all came apart. It needed a 12 second delay and I ignored my gut feeling to just let it go and not drill the delay.:bangpan: Let the altimeters decide when it reaches the top.

Back to the drawing board for a new AV bay.

Even with the loss of this rocket it was still a great flight and had a great time reading the altimeter data and deciphering what the problem was. Plus I found all the parts except one fin and the chute, which was good I have 200 bucks alone in the AV bay. And no damage to the motor.


TA

Too bad T. I bet next time you use welded eye bolts.

Gary Byrum said:

I always figured ALL HPR rockets were built around the motors. I mean let's face it, you are limited with your aesthetics unless it's with the finish job.

Click to expand...

Rockets that are optimized for performance have a more constrained appearance (whether LPR or HPR), but not all HPR rockets are about performance. There are lots of exotic HPR rockets; they're just more challenging to build because the forces increase non-linearly.

thobin said:

So the lessons that were learned ground test your ejection charges, I did use a grain calculator but I guess my numbers where off. Weld or use a forged eye bolt, on these high speed flights let the altimeters do the eject at apogee. And zip ties will not hold a battery no matter how tight you think it is.

The simulation software I guess can only take you so far, my projected altitude for the motor and rocket where only 4800ft and it made it to 5711 before it all came apart. It needed a 12 second delay and I ignored my gut feeling to just let it go and not drill the delay.:bangpan: Let the altimeters decide when it reaches the top.

Back to the drawing board for a new AV bay.

Even with the loss of this rocket it was still a great flight and had a great time reading the altimeter data and deciphering what the problem was. Plus I found all the parts except one fin and the chute, which was good I have 200 bucks alone in the AV bay. And no damage to the motor.


TA

Click to expand...

Wait, you used motor eject with an altimeter?

CarVac said:

Wait, you used motor eject with an altimeter?

Click to expand...

Yes motor eject with altimeter backup.

Honestly I thought this rocket was done for, it had a buckle the tube that made the rocket off center at the transition, you can see the crack.



I figured I wasn't going to get it out with any means other than tearing it all down. I decided to give it a try I was able to pull it strait with very little effort the problem was it wouldn't stay put with out some kind of support.

I squeezed a ton of thick CA in the crack and pulled it tight and gave it a shot of accelerator and it seemed to do the trick. Not very confident that that would be enough I drilled a bunch of 1/4 inch holes and took some expanding foam and shot it in all the holes I drilled.

I'm certain it had fill the whole cavity of the tube and transition, it came out some relief hols at the top and it oozed for about a day.



I got on it today and it is strait and stiff as a board with not much extra weight. I think I can save this one.


TA

I cut the tube around the fins off and pulled out the broken fin, took me a bit to get then new fin sized just right but I think I got it.



The centering rings are 1/4 inch so i'm going to split the difference with a cut and glue the new tube section to that, and I may fill it with foam to give it that add bit of strength.


TA

Fin is glued in paint sanded away and a new section of tube all glassed and ready to go.




TA

Well played Sir. Keep up the great work and bringing this thing back to life, such a sweet looking rocket!