Motor cert question

[Neil]

I was just in a local hobby shop, and there were 3 packs of E27-4Ts, and an 18MM reload case. My dad and I said "hey, what the heck. How many other times are you going to come across such great motors"? I obviously had not read the list of certed motors in Sport Rocketry lately, so I tohught they still had cert. They are not on ATs website, NARs website, or Sport Rocketry magazine. Is there something wrong with this type of motor? are they safe to use, if we forget about the cert problems? I could always fly them on my own, couldent I? They would make one heckuva flying sauver flight if you ask me.... My bet is they have been sitting on that hook at Ray and Robins for years, I have seen that case there for at LEAST a year and a half now and not given it any thought. Well, now I have an 18/20 case, and 9 possibly un-certed motors sitting in my range box. Well, at least I have a field with more than enough space for a flying saucer powerd by one of these buggers!

Well, no loss to me if I cant use em, my dad paid! Plus at the very least I get a good case.... I do hope nothing actually WRONG with them, they look like some pretty cool motors!

 

[rbeckey]

Certification is an artifact of NAR/TRA and is not applicable unless you are at a launch sponsored by one of them. It has little to do with the actual safety of that particular motor at this time. If the manufacturer decided to stop making them and let the cert expire, they didn't suddenly become less safe or effective because of that alone. Age and storage conditions are another matter. I never used one of these, so maybe someone who has can comment on their characteristics.

 

[Neil]

Safety due to loss of cert is not what I was asking about, I was wondering if they lost cert (or manufacturer didnt want to renew cert) as a RESULT of not being safe, such as some strange malfunction.


Who knows..... I still cant wait to fly a saucer on one, cert or no cert.... Half the flights I make are at club launches, so cert is kinda important to me, or at least it is untill I get a 12V controller.....

 

[Ryan S.]

You can fly them wherever you want to (as long as you have permissions etc) as long as it is not at a NAR or TRA sanctioned launch. Saucer would be fun, just put them up in the back yard, The 18mm case is so little, it is awesome

 

[Neil]

PLEASE tell that to my parents.... They wont hear anything of it untill we "get to know the neighbors" (we just moved in here last night). We have more than enough room for most flying saucers, but an 18MM E sounds like overkill. Proabably at Twin Brooks rec facility, though. They have plenty of room....

 

[n3tjm]

There is nothing wrong with the E27. It is a very nice motor. Unfortunately they decided to cut back on their line of 18mm loads, and the E27, along with the B6, C4, C6, and C12 motors died with them. I hope they bring them back, and if they do… put three nozzles in each reload!

 

[Initiator001]

The B & C reloads for the 18mm RMS system started out as an experiment to see how small a reload could be made for the 18mm system.

Once it was discovered reloads as small as a B6 could be made that's when the idea of making these part of the product line took hold.

Another driving factor was that these reloads would give AeroTech a way to directly compete with the 'other guys'.

However, while the cost for the reload package was competitive, the additional $40 cost of the reload casing did not work in the favor of these smaller reloads. This may have been the indirect reason these reloads were not popular and were discontinued.

As to why only one nozzle for three loads, testing showed that one nozzle would last three flights. Also, adding two more nozzles would have required the cost of the reload package to be raised above the competiton or accept a lower profit margin.


I was hoping that an 'A' performace reload could have been created but calculations showed that the nozzle throat would be too small to allow an igniter to fit through.

 

[Neil]

Um, I dont know where you are getting the idea that they come with only one nozzel... Mine came with 3. Thats strange... Its a pity they discountinued thos other loads... I hope whoever buys AT brings them back....

 

[n3tjm]

The B6, C4, C6, and C12 reloads came with a single nozzle.

The nozzles were a pain to clean, especially with the White Lightning loads...

I would pay the extra 0.50 to 1.00 for two more nozzles.

Also, looks like 18mm cases are available again

 

[Neil]

Were they OOP? if the age of the loads is any guide, that case has been collecting dust for several years, so I dont think you can count this as proof they are still making them.... "still", not "again" would be the more apropriat word.... Dont you have to reuse USR nozzels? THat sounds like a bother....

 

[Ryan S.]

yeah but they are graphite, you really dont want to reuse phenolic because it errodes to much

 

[Neil]

Does that corroding lower the thrust of the glass-phenlolic burns on initiallly high thrust motors? If the high thrust really took its toll, wouldent the rest be less powerfull because the throat was enlarged? You would think that this would be very bad on motors such as the F10, G25, H45 ETC, since they have such a long burn.... what actually MAKES it corrode, is it the heat, the hot gasses passing through the throat or the propellant type, or something I have not thought of? thinking out loud here....

 

[MarkABrown]

Actually, the word is Erode. Corrosion is a chemical reaction. Erosion is the wearing away of material. Erosion in nozzle throats can be caused by metals in the propellant for fuel. I'm not familiar with these particular motors but, I suspect that the reason they thought they could get away with only 1 nozzle is that the propellant probably had a very low metal content and short burn time. This would result in a relatively low erosion rate thus allowing the nozzle to be reused.

 

[Ryan S.]

thanks Mark, sorry for being an idiot.

Your right about metals. I saw the staticstics somewhere and I think they were; with a graphite nozzle you will get about 8-12 firings with regular propellant. With a sparky propellant you only get 4-6 because the Ti does such damage to the nozzle.