Looking For a Place to Launch F-Series Motor
Is there any other solution? I do not have access to my 3D printer, so I can’t make any modifications.
I believe the caliber is around 1.5, but will check in the morning.
You'll need a standoff of some kind. Here are some versions that Apogee sells, but you could easily 3D print something similar.
And 1.5cal is a good number (with the engine installed).
Uploaded files:
Here's another option that might be easier to build yourself. For a larger rocket, this should fit a 1/4" rod.
Uploaded files:
Quote from SkyEpstein on July 23, 2024, 10:14 pmOne problem: the nose cone is larger than the actual body of the rocket, meaning that launch lugs or rail buttons cannot easily be added. Again, the simulations did not indicate any problem with not having a launch rail.
Why don't you post an image from your simulator of your rocket? If you're using OpenRocket, use "Print Design Info" and save as a .PDF. I've included an example. From this, we can see better what you are planning to fly and the simulation data as well. The dimensions can help us help you with the best solution for launch readiness.
Uploaded files:Here is the rocket. Some more info: it is fully 3D printed, out of black PLA aero filament from Bambu Labs,
Uploaded files:Nice looking rocket.
I'm sure Brian will comment on the 3D aspects.
Yes, you will definitely need a launch lug (with standoff) of some kind.
Also, I think an engine with a bit more thrust is needed. Maybe an E30-4 or an F32-6.
Unfortunately, I don’t think I will be able to get new motors in time, especially since they are out of stock everywhere I have looked. The simulations show that the F15-4 will work, and since those were out of stock I got F15-6 motors, which should work the same.
Good news and bad news.
Bad news is that no, the simulation shows it will NOT work. You need a velocity off the rod of about 25mph or more, or 11m/s (although we could lower that slightly if no wind). Your file shows 0.6m/s, but that's probably with a 0 rod length. Increase it to 4ft and you'll have a better number, but I'm guessing still too low. Try it and correct me if I'm wrong. The other indication is the thrust to weight ratio. Usually we'd like to see 5.0 or more. You're about half that. Bottom line is that it's a little heavy, so you need a higher thrust to get it moving fast enough before it leaves the rod to be stable.
Also, the delay is a little long, showing a pretty good speed at deployment. While the rocket can fly with a longer delay, it's not a good idea to eject at high speed. That can cause separation of the nose cone/parachute from the body, which can be a hazard. Not to mention possibly destroying your rocket. Or if the flight is low and the delay long, the rocket could "land" before opening its parachute.
The good news: we are expecting a vendor to be there who will have plenty of suitable options for purchase. Joe from Rocketship Games (link here) treats us well with good discounts (about 15%). He hasn't confirmed, but we do expect him to be there. You can order in advance and note the delivery is for the CENJARS launch (saving that expense). You can also send him an email with what you'd like and he'll make sure to bring it.
And if that doesn't work, I'll likely have something in my motor box that would work, and can sell it to you at cost (the same as Rocketship Games).
Please be assured that we are not trying to give you a hard time. We welcome everyone and only want you to succeed. There are always plenty of people available to answer questions and help anyone who needs a hand. But we also have to protect our use of the field we fly on, and the neighbors around the site. If we have a lot of dangerous flights that impact the area, that permission could be revoked. Or worse, there could be damages or injuries from such unfortunate events. So while "stuff happens" on occasion, we must try to avoid unsafe flights as much as possible.
2 additional comments on Mr. Epstein's design.
1. It should have a longer shock cord. Think 2x body length.
2. It needs a name.
Look forward to seeing it fly. Vertically would be best. Trust me.
Chris Oliver