Ye Olde Rocket Forum

Ye Olde Rocket Forum (http://www.oldrocketforum.com/index.php)
-   Ask the Doctor (http://www.oldrocketforum.com/forumdisplay.php?f=22)
-   -   Q-Jet motor max lift weights ? (http://www.oldrocketforum.com/showthread.php?t=19015)

Flash 11-18-2020 08:02 AM

Q-Jet motor max lift weights ?
 
The max lift weights of the C Q-jets seems very low to me? Less than 4oz?

Estes C5-3 is rated at 8oz

Estes C11-3 is rate at 6oz

Any thoughts?

C18-4 W
Motor Diameter: 0.698" (18mm)
Casing Length: 2.75" (70mm)
Total Impulse: 9.8 N-sec
Burn Time: 0.52 seconds
Average Thrust: 18 newtons
Delay Time: 4 seconds
Propellant Weight: 5.6 grams
Propellant Type: White Lightning
Motor Weight: 20.9 grams
Maximum Liftoff Weight: 113 grams

D16-4 BJ
Motor Diameter: 0.698" (18mm)
Casing Length: 2.75" (70mm)
Total Impulse: 12.4 N-sec
Burn Time: 0.79 seconds
Average Thrust: 16 newtons
Delay Time: 4 seconds
Propellant Weight: 9.9 grams
Motor Weight: 25.7 grams
Maximum Liftoff Weight: 128 grams

Scott_650 11-18-2020 08:17 AM

Iíve always treated max liftoff weight as a guideline more than a rule - a small diameter, low drag rocket over the limit by a bit (on a calm day) will probably be fine, while a lighter but draggy rocket may not work well at all. Iíve used the initial version C/D QJets in heavier, low drag rockets and theyíve worked well, while my Estes 1/200 RTF Saturn V definitely doesnít like the D motors. What I havenít tried, other the the SV, is heavy draggy rockets over a C/D QJet.

TigerHawk 11-18-2020 10:50 AM

I've used the A3-4, A3-6, B4-4, B4-6, C12-4 and D16-4 Q-Jets and they've all been great launches and recoveries. I use the D16-4 in my Estes 1:200 RTF Saturn V and it works great. I've used the C12-4 and D16-4 in my MPC Red Giant and it launches it way up there. All in all great experience with them so far and looking forward to using the C18 and D20 Q-Jets.

ghrocketman 11-18-2020 11:01 AM

I'm looking forward to the C18 and D20 as well.
Will try the short delay ones of each in my Mars Landers then get a bulk-pak of Ds.
Might even get out one of my old 1284 Space Shuttles to try the Ds too.

tbzep 11-18-2020 11:11 AM

Quote:
Originally Posted by ghrocketman
Will try the short delay ones of each in my Mars Landers then get a bulk-pak of Ds.

They will be particularly good for heavier Outlander models.

Scott_650 11-18-2020 11:20 AM

Quote:
Originally Posted by TigerHawk
I've used the A3-4, A3-6, B4-4, B4-6, C12-4 and D16-4 Q-Jets and they've all been great launches and recoveries. I use the D16-4 in my Estes 1:200 RTF Saturn V and it works great. I've used the C12-4 and D16-4 in my MPC Red Giant and it launches it way up there. All in all great experience with them so far and looking forward to using the C18 and D20 Q-Jets.

My Looney Tunes equivalent of the Red Giant and my MPC Enterprise both work great on QJets. Love using the D motors with an adapter in my Estes Vagabond, the faster takeoff is a fun change from the slower BP launches.

5x7 11-18-2020 12:42 PM

I think the weights on the Q-jet As and Bs should be heeded. I started out trying to fly models that flew well on Estes B6-4 but were too heavy for the Qjet B4-4.
There is a mistake in The Cs max weight recommendation since the C12-4 and C12-6 are both listed at 113 g. 200 would probably be a good number for C12-4. The C18 uses the same flawed recommendation for 4s and 6s. The C18 and D20s should probably also be higher since they have double the initial thrust.

Beyond that, the delays for the 4 sec are a full four or more. The C5-3 is the exception but the delays for Estes are usually shorter than listed.

As long as itís low enough to be safe.

Scott_650 11-18-2020 12:59 PM

Quote:
Originally Posted by TigerHawk
...I use the D16-4 in my Estes 1:200 RTF Saturn V and it works great...

The QJet C motors work fine in my RTF SV but for some reason it just doesnít fly right on the D motor - I get a squirrely tail waggle that doesnít happen on a C motor. If I ever get one of my Dr. Zooch Saturns done the 1/200 Estes is being retired to display status anyway so itís not that big of a problem.

5x7 11-18-2020 01:09 PM

Quote:
Originally Posted by Scott_650
The QJet C motors work fine in my RTF SV but for some reason it just doesnít fly right on the D motor - I get a squirrely tail waggle that doesnít happen on a C motor. If I ever get one of my Dr. Zooch Saturns done the 1/200 Estes is being retired to display status anyway so itís not that big of a problem.

Check the nozzles on the D, I have had the nozzle surface and a bit of throat break out of a C and D. There was a pronounced jog in the flight path and both flights seemed lower than normal.

TigerHawk 11-18-2020 01:26 PM

I actually have to use a engine adapter when I launch my 1:200 Estes Saturn V, with the Q-Jets, because I converted it to a 24mm with the FlightSketch conversion. Haven't even tried it with a 24mm motor yet, so I guess I should try it sometime.


All times are GMT -5. The time now is 08:31 AM.

Powered by: vBulletin Version 3.0.7
Copyright ©2000 - 2021, Jelsoft Enterprises Ltd.