Discussion in 'Propulsion' started by RIB, Aug 14, 2017.
Actually, 0.69" converts to 17.5 mm, not 18 mm.
????????? Did I miss something? Who mentioned .69"?
0.695 inches is the diameter of an Estes 18mm motor...so is a comfortable fit in BT-20 with an ID of 0.710 inches.
Ahh, I see. Thanks for clarifying that. Just an aside, did you ever notice that the nozzle end of an Estes engine is slightly bigger than the front end? So I guess the .695" figure might be an average?
Now you're going to make me measure a few....
Probably has to do with the nozzle making process, the extra pressure causes the case to bulge slightly.
Saw someone fly a Q-jet for the first time yesterday. He also had to work to get the motor to fit into his 18mm mount. Nice flight, I liked the smoke. The delay seemed to be longer than advertised; ejection finally happened fairly close to the ground.
I'll definitely be interested in the Cs and Ds once the various issues are all ironed out.
0.69" (11/16") is the original standard. 18mm was just a shorthand approximation.
To BEC and anyone who experienced the aforementioned problems with their Q-Jet order:
Strongly suggest you e-mail Quest customer service and notify them. I e-mailed them a couple of days ago asking if they are giving at least a partial refund since the first batch has limited functionality.
Received a reply today from Mr. Karl Baumann, VP of R&D at RCS. He says that they are reducing the OD and recessing the front end of the newer motors to address the fit and engine hook problems. He also offered to replace the Q-Jets that I ordered with the revamped ones, when they are available.
Now that's what I call great customer service! Will be ordering the Cs and Ds when available. Keep on rock(ateer)in'!
Thanks for that. I saw your post in the YORF thread as well. I will do so.
Yes, Aero-Tech/Quest customer service is AMAZING!
I've always had a great experience with them, and they've always fixed their mistakes, if they ever do (Which is pretty rare)
5 stars for their customer service!
I just received a few packs of Q-Jets I had ordered a few weeks ago before I read about the problems some are having. One thing I discovered is they fit very well in the Estes 18 to 24 plastic adapter. If you have a rocket with a 24mm mount that is light enough for the Q-Jet it may be a way to use them.
I need to do more measurements but am finding that it's not as simple as "they don't fit in BT-20". As it turns out, sometimes they do. I'm learning both that some of the Q-Jets I have on hand are larger in diameter than the quoted spec (per Gary R on Facebook, casings are supposed to be 0.698 +/- 0.003) and that some "BT-20" tubes, notably those blue Estes motor mount tubes that have been in kits for 25+ years seem to be a tiny bit undersized. Put the two together, add a little tube shrinkage around a motor-tube-to-centering ring joint and you have a situation where a Q-Jet just won't go in. But they slide right into the Citation Patriot I just built for example - without even threatening to peel the label off.
As I say, more measurements are in order.
I flew five more Q-Jets today....and the two A3-4s had KILLER ejection charges. But no misfires and one flight in particular was really nice.
added later: now I'm really confused. I just tried some of today's spent Q-Jets and a couple of others in the same blue motor tube that made me draw the conclusion yesterday that it's undersized - and except for the ones with the label partially peeled back and wrinkled, they went into it.
I also found my old (well, 9 years or so old) Quest Astra - they won't go into it. ....more measurements....and taking better notes....needed.
I took a few minutes this morning to do some measuring and experimenting. The B4-4 and B4-6 I have both measure exactly 18mm at the ejection end which is the same or very slightly larger than the nozzle end. My A3-6 went a tiny bit smaller at 17.95mm. Most of my low power rockets are built from Semroc parts. The Q-Jets fit in all my Semroc #7 tubes as well as the one or two Estes BT-20 tube rockets I have. Strangely enough, the one very tight fit is an old Quest Nike Smoke, it went in but after firing getting it out may be a challenge.
I went ahead and removed the labels from one motor out of every pair while in the comfort of my shop. They all peeled right off and a quick swipe of 3M Adhesive Cleaner removed all traces of goo. Probably took less than 10 minutes to do 3 motors.
One of our members flew a B4-4 in an Estes Monarch on Saturday.
He got the motor from Charlie at NSL. I do not know the date code since our club member removed the label for fit.
Flight was perfect.
Delay time seemed to be very close to 4 seconds - the longest I would estimate was 4.5 seconds.
Ignition was perfect using the 3/64" heat shrink tube installed next to the initiator.
Ejection charge was perfectly sized. I suspect that this was from a batch of motors produced after the initial feedback provided, as they stated that all motors were now being made with the reduced-to-proper-levels ejection charge.
I have no idea why the first batch of B4-4 motors dated 050118 have the 6 or more second delay time. it would be pure speculation to guess that maybe the motors were either built with the 6 second delay installed or mislabeled.
I'm itching to buy a very large number of all these motors since I like the performance and initiators.Just waiting to get official word of the casing diameter revision and updated instructions (which will include max liftoff weights for each motor and delay time as well as the info on using the 3/64" dia heat shrink which will be included).
I haven't looked but have they been approved for import into CA?
They are classified by the CSFM as "Model Rocket Motors".
When we expect the C & D motors to go on the market?
Gary was saying mid to late July.
Just wanted to drop in and let you all know that we have been monitoring the thread and absorbing your feedback. The issues that were mentioned will all be taken care of with the next iteration of Q-Jets. C and Ds will be shipping Late July/Early August and will fit all brands of 18mm motor tubes. Thanks again for the feedback!
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