Has anyone else noticed the poor reliability of Aerotech RMS motors and delays manufactured post-fire? I'm not a big AP flyer, but have probably flown 10-12 "fresh" ones over the past couple years, and I'm getting terribly early delays---4's that go right after burnout. I've zippered Apogee Saturn V twice! I'm not at all impressed with these, especially after seeing prices jump 30-40% as well.

Upon reentering into the Wild World of Rocketry preliminary research indicated that the Aerotech RMS system was the motor of choice, so I purchased both 24mm and 29mm RMS casings. To date, the 24mm casing has yet to have a successful flight or, for that matter, a successful burn. The first catastrophe was a static test of the ejection system for my scale Spaceship Friede using an E18-4. At ignition the motor seemed to fire but was rather weak and just before the ejection charge ignited I noticed smoke seeping from around the nose cone and below the airframe. At ejection the nose cone popped and hellish flames and smoke burst forth, my worst fears were realized, the entire internal structure of my magnificent creation was charred beyond recognition. Analysis of the carnage indicated that exhaust gases had blown by the forward closure scorching it and the motor tube. RIP Friede. The 24mm casing was given a second chance at life with the maiden launch of my 3FNC design on an E18. As feared, when the rocket reached the end of the launch rod it began doing loops at an altitude of about seven feet. RUN!! Finally she power pranged just inches from the launch pad miraculously unharmed. While the pictures of the event turned out well the flight was exciting but a bust. Analysis of the photos and engine casing indicated that there had been blow-by just after ignition forcing the nose cone off and thereby saving the airframe, but the ejection charge didn't fire until the third loop. I am debating whether or not to send this casing back to Aerotech; two CATO's are a bad indicator. On the other hand the 29mm RMS has worked like a champ without fail; I was so pleased with it I purchased two additional casings. On the second launch attempt of my 3FNC, this time with the 29mm RMS, she roared off the pad straight as you please and flashed away into the sky. Thus demonstrating that the design is stable and that the 24mm RMS was at fault. Conclusion - The Aerotech RMS system, while more complicated and messy than single use motors, is of the highest quality, a definite money saver and well worth the investment, when it works. My recommendation - Buy the 29mm RMS, you will be happy you did but be cautious of the 24mm RMS.

Sorry to hear about your troubles... don't throw away your case (I'll take it). I have NEVER had a 24mm RMS failure in any way shape or form. I have some tips for you if you'd like: 1) follow all instructions for where o-rings and propellant goes (for short propellant the gap is between the propellent and delay; 2) place a piece of masking tape that covers the propellant slit and top of propellant slug, leaving about 1/3rd exposed; 3) apply grease to the delay charge o-ring; 4a) If delay is real loose, common in 24mm, then apply tape around it until it is snug when pressing into the forward closure; 4b) If delay is good fit (or after applying tape), grease to the tube grooves (or outside of tape) prior to sliding it into the forward closure; 5) lightly grease the inside of the main 24mm casing (makes for easier clean up); 6) when everything is ready, slide the propellant slug into the main case and hold with your finger from the nozzle end so that it is just about in position. Place the fiber ring and lightly grease forward o-ring and then thread on the forward closure (delay charge) only 1 turn; 7) Place in nozzle and slightly greased o-ring (thicker one if I recall) and thread on the aft closure one 1 turn; 8) Slowly tighten down the forward closure; 9) Tighten the aft closure to as tight as you can or when it touchs the casing?.That's it. Hope it helps.

The RMS series of motors are like thoroughbred horses - they perform well, but can be temperamental. I had my first experience with this when flying the D15 kit in the 24 RMS. The motors are designed so that the double thickness of cardboard, as well as the flat smooth, solid double thickness end are essential to getting a good seal. The problem is the cardboard spacer tube. The fit within the insulating outer sleeve is TIGHT!! I had two where the grain spacer stuck about 1/16th of an inch out from the top. I tried to trim it to length, but that didn't work. The seal leaked, and blew the delay charge out through the top of the motor. The smaller the engine, the bigger problem. It is never the propellant grain itself. That part is notched, and rubber, so it will fit by slight squeezing, without any problem or permanent deformation. By contrast, the adapter / spacer tube fits VERY tightly, and cannot deform without crushing. The lower power in the motor, the longer the adapter tube, hence the greater likelihood (2/3 so far) that will stick most of the way in, without a way to remove them. That's why this problem showed up when I was flying D's in the 24. The E's were much easier to insert -- shorter adapter tube due to more propellant. In my opinion, the factory should insert the adapters into the outer tube. In the alternative, they should let the rest of us know the acceptable way to obtain a fit. Graphite? OD sanding of the adapter / spacer tube? Strip outside layer of paper on grain adapter/spacer?? Same plus glue? I believe that this problem is likely behind a lot of the complaints about the RMS series of motors. If you ding the top or bottom of the grain assembly, you won't get good seal. Given the pressures needed to get (or attempt) assembly, you stand a good chance of deforming a cardboard tube on one end or the other. Again, the more the propellant, the less you need to worry about the then smaller spacer tube. The friction is proportionate to the surface area. A small spacer means greater likelihood of assembly. PS: So far, I've had 100% reliability of copperhead ignitors in these motors, because I always put a couple of decent vent holes into the nozzle cap prior to assembly.

I have used both the 18mm and 24mm RMS and I love them. I have never experienced any kind of failure. They really give my Estes rockets a "kick in the pants". I highly recomend them to anyone who likes the idea of "more power" and is a bit of a tinkerer. (like me!) Rumor has it that Aerotech is going to come out with a 3.75" (Estes E motor length) 24mm RMS casing soon. I'll be "all over that"!

(Supplement to my earlier post 06/05.) The Aerotech 24mm RMS casing has redeemed itself; it had its first successful flight this morning. But there are no images to show off the great flight, the camera media glitched and lost them all. Thanks to everyone that offered advice and suggestions on using the 24mm RMS.

I got my 24mm RMS case about 1 year ago. I find it very reliable. I have flown mine 5 times and it has not had one CATO. I recommend this RMS case to any one who is getting into mid power rocketry. Sam

I've had mixed results with 24mm RMS motors over the years. Way back in 1994, my first RMS 24 blew out the forward seal and suffered ejection at speed, completely destroying a custom built Astrocam carrier. AeroTech did replace the reload--in fact, they sent a new 3-pack! Over the years, I had owned one more casing and borrowed several with a 100% success rate. I purchased Rouse-Tech casing last year and trust it enough to launch my "American Flyer" on it. This bird is a "proof of concept" for some lightweight building techniques. It has a BT-101 main tube, is 3' long, but only weighs 14-15oz ready to fly. The 24mm E15-4 reload is perfect for it and kicks the large, draggy "American Flyer" off the pad with authority! Eyeball estimate for altitude is in the 600-800' range. Not too shabby, and it can be flown relatively cheaply on the RMS reloads. The secret to keeping them reliable? Fitting issues of the liners can be sharply reduced, or eliminated entirely, by keeping them DRY. Moisture swells them, and they WILL hang up, sometimes to the point of being impossible to assemble right. I tape shut opened reload bags with a silica gel bag inside (which you can get from eBay or electronics store). The other thing is, DON'T overdo the grease! It can block proper burning of the delay element and trigger failure. Just use enough to coat the O-rings. Mine has been 100% reliable when used with due care.

I have both an 18mm Aerotech and the 24mm and am just getting used to them, but I have had no problem with them except for the Copperhead igniters. It seems all the people I fly with have had problems with the Copperheads. I wonder why AeroTech hasn't fixed this problem. One thing I have found useful is to tighten the forward and rear closures tightly. This saves a lot of grief.

Im sorry to hear about all of the bad flights. Ive flown the 24mm casing plenty of times, and havent had a problem yet. All of my motors lit on the first try, and the delay seemed spot on. The only motor I have heard bad things about has been the E18. Aparently the Aft Closure continously blows out and the case is ruined, but other than that, Im happy. Just remember that most of the problems are probably operator error. If you get grease on the delay element, it either wont burn or will burn very slowly, and having the O rings in the wrong spot is just another thing that can cause a CATO.