Estes TARC Parts OpenRocket

Does anyone have a good OpenRocket model of the "egg capsule" from the Estes Large TARC assortment? The nose cone and transition are apparently from the Estes Titan III.

I'm helping with a local high school's engineering class, and they are designing their own egg lofters using OpenRocket and the large TARC kit. Having them design a biconic nose cone by hand is a bit much for day 1 in OpenRocket, so I was hoping someone out their had done the dirty work.

This is not canon... It is only offered as a template that you can use to create a correct model. Since I don't have one to model from it's the best I can do.




There are only two dimensions in the whole simulation that I'm 100% on. the BT-70 section was documented, and the inner/outer diameters of a BT-60

BTW... this took about 15 minutes to create...

View attachment Titan III Nosecone, Payload Section, and Transition (Thought Exercise).ork

Thanks K'Tesh, that's awesome - much better than my crude attempt. When I get the parts in-hand I'll try to measure it up and modify your file with real numbers, and we can get a canon part on here.

Not a problem...

I've broken it down into four parts: The nosecone (an elliptical section), and three conic transitions (one is cylindrical and includes the shoulder).

One thing to look for on the nosecone... When you get your part, I'm guessing that it will have a short flat (cylindrical) section just like I modeled (but not necessarily quite so long). Estes likes to do that, but many of the sims I've seen people don't try to model that. The more accurate you model your part though, and the better your sim should be.

Similarly, there will likely be a cylindrical section on the forward end of the aft transition, just like I modeled.

Oh, and the way that the nosecone bulges at the joint with the first conic section... Try as I might, I am not able to get that to look right, I never have.

Looking forward to seeing the updated figures when you get them.

Pointy Side Up!
Jim

Sorry this took so long, finally got hands on the parts. The classroom didn't have a micrometer handy, so I had to dimension these off a photo.

Only other edit I made was to take the end caps off the nose cone and transition piece - figured most would hack these off to be able to use the interior of the cone/transition for additional payload space.


View attachment TARC_TitanIIIE_Nose.ork

Also, a question - anybody ever experiment with spin stabilization on egg lofters? One of the student teams is considering using angled fins to spin up the rocket, in the theory that it will reduce weather cocking. I'm not really worried about the stability of the design (if anything the egg lofter is over-stable) but I did have a couple of concerns:

1) The angled fins are going to experience more stress, and attaching them at an angle may make it harder to get a solid bond. These rockets are already going to be pretty "sporty" (standard Estes parts on F engines) and I don't want them to hit the speed of balsa.

2) Unless the deployment is perfectly at apogee, it's still going to be rolling pretty good at deployment, possibly tangling the chute.

3) It probably won't work to reduce weather cocking - I don't think a model rocket has enough rotational inertia to really gyroscopically stabilize except at a very high roll rate. Since most weather cocking occurs at low speed just after take off, the rocket won't be fully spun up in the region of interest anyway.

So does anyone have more practical experience? I'd like the students to learn and implement their own designs, even if they don't make the "right" decisions, but obviously I don't want to let them do anything unusually unsafe. Is spinning the egglofter enough of a concern that I should nix it and make them change the design, or just let it rip and let them find out for themselves?

Thanks for the update. I'll have to check out my original file to see how far off I was.

Oberon said:

Also, a question - anybody ever experiment with spin stabilization on egg lofters? One of the student teams is considering using angled fins to spin up the rocket, in the theory that it will reduce weather cocking. I'm not really worried about the stability of the design (if anything the egg lofter is over-stable) but I did have a couple of concerns:

1) The angled fins are going to experience more stress, and attaching them at an angle may make it harder to get a solid bond. These rockets are already going to be pretty "sporty" (standard Estes parts on F engines) and I don't want them to hit the speed of balsa.

2) Unless the deployment is perfectly at apogee, it's still going to be rolling pretty good at deployment, possibly tangling the chute.

3) It probably won't work to reduce weather cocking - I don't think a model rocket has enough rotational inertia to really gyroscopically stabilize except at a very high roll rate. Since most weather cocking occurs at low speed just after take off, the rocket won't be fully spun up in the region of interest anyway.

So does anyone have more practical experience? I'd like the students to learn and implement their own designs, even if they don't make the "right" decisions, but obviously I don't want to let them do anything unusually unsafe. Is spinning the egglofter enough of a concern that I should nix it and make them change the design, or just let it rip and let them find out for themselves?

Click to expand...

I can't say that I've got any experience with spin stabilized rockets (other than making an Estes Spin Fin as my first rocket).

That said, I highly doubt that a spin stabilized rocket would be a very good flier in such a small scale. Besides the issue of having the additional stresses on the fins, you'd also have to sacrifice a lot of the motor's power into inducing the spin. I also suspect that the spin rate needed to stabilize a rocket would be well and truly beyond the ability of the body tube to handle the stresses involved.

I'd suggest a more traditional method (such as fins, or tube fins).