AT F reloads

[cosmodrome]

I don't know if this has been covered elsewhere, but I can't find it... Are there any plans to convert the F reloads (F22, F40, F52) into 2 grain motors? E's and G's can ship USPS with no Hazmat fee, but the F's incure a $20 charge.

 

[rrobe99999]

I don't know what AT plans to do, but I feel your pain. I've started using F motors around 60ns in the 24mm reloads or 29mm LMS variety to avoid the Hazmat fees.

 

[Mike Di Venti]

Just order A LOT of them, then the $20 is spread out.
That's what I do.
If you order enough of them you can get free shipping too.

my :2:

 

[bobkrech]

There are no 24 mm AT F reloads with propellant grains exceeding 30 g, and only (3) C-slot 29 mm AT F reloads with propellant grains exceeding 30 g: the F22 has a 46.3 g propellant grain, the F40 has a 40 g propellant grain, and the F52 has a 36.6 g propellant grain. The APCP total impulse limit is ~2 Ns per gram, so once you get above ~60 Ns you will exceed 30 g of propellant, so ang single use motor exceeding ~50% F impulse will not be mailable.

A manufacturer can cut a Bates reload grain in half and produce a loadable or reloadable F motor that is mailable, and AT has converted several C-slot single grain LMS motors into 2 cored grain LMS motors which are mailable. I'm pretty sure that unless AT redesigns these C-slot F motors into a dual cored grain configuration, you're going to be stuck with a hazmat fee because I don't believe C-slots can be cut in half because if the slots are not aligned, a cato by overpressurization can occur.

Bob

 

[Sandy H.]

I'm pretty sure the G-64 is 2 C-slot grains that you tape together during assembly. Wouldn't that work on the F RMS style motors?

Sandy.

 

[shreadvector]

I'm pretty sure the G-64 is 2 C-slot grains that you tape together during assembly. Wouldn't that work on the F RMS style motors?

Sandy.

The current incarnation of the G64 and several other G RMS loads is indeed "bifurcated".

https://www.aerotech-rocketry.com/resources.aspx
https://www.aerotech-rocketry.com/resources.aspx?id=4
Temporary location of instructions while website is tweaked:
https://208.67.252.6/customersite/resource_library/AT_instructions.html

G53FJ 2-Grain Instructions (60 gram propellant weight)
G64W 2-Grain Instructions (978k)
G71R 2-Grain Instructions (918k)
G76G 2-Grain Instructions

Answers from the manufacturer can be obtained by contacting the manufacturer, as opposed to posting questions about design and release of future products on a public forum where we can simply speculate or make stuff up. (i.e. "phone them")

 

[cosmodrome]

Answers from the manufacturer can be obtained by contacting the manufacturer, as opposed to posting questions about design and release of future products on a public forum where we can simply speculate or make stuff up. (i.e. "phone them")

I know that would have been the quicker way to get an answer, but since I ddin't think this was that pressing of an issue and I know that Gary frequents the forum... Didn't really think that it was worth interupting him with a phone call for a question that I don't need answered ASAP.

As a manufacturer myself, I enjoy answering questions about my products online, if it's important enough for one person... That also avoids the speculation part.

 

[bobkrech]

I'm pretty sure the G-64 is 2 C-slot grains that you tape together during assembly. Wouldn't that work on the F RMS style motors?

Sandy.

You are indeed correct. AT has done a number of internal changes in their single use, loadable (DIY SU motor) and reloads over the past 5 years for economy of manufacture and to comply with USPS regulations. It's sometimes hard to keep track of them all without a scorecard.

My concern about a multiple grain C-slot design is valid but I had forgotten about the "new" G64 reload. I checked both the S&T certified motor listing https://nar.org/SandT/NARenglist.shtml and the AT website before I made my previous post. As a member of S&T I usually remember the motors that I help certify, but I had forgotten that AT made a design change in the G64 from single 62.5 propellant grain into (2) 30 g propellant grain design several years ago. (The caveat that the two grains had to be taped together before insertion into the liner to keep the slot aligned.) The 2 grain design has the same average thrust and only 5 NS less total impulse the the single grain propellant so this manufacturer motor modification did not trigger the need for recertification under the old NFPA 1125 and S&T testing requirements. (IIRC it's not due for recertification until next year, so we haven't static fired the new G64 which explains why it's not listed on the S&T page.)

In some G impulse LMS motors, AT changed the single use C-slot grain to 2 Bates grains to meet USPS regulations to avoid commercial hazmat charges, but if two C-slot grains are aligned and taped, the reload using this design will function properly.

Bob

 

[MarkH]

You could buy from one of the vendors that doesn't charge a hazmat fee, I've heard that some do...:confused2:

Or you could buy from a launch site vendor.

I know the law is the law but it is really kind of silly. Vendors can't legally ship a load over 30 g (w/o hazmat fee) but can ship a pound of individually wrapped 30 g loads with no fee.
op:

 

[bobkrech]

You could buy from one of the vendors that doesn't charge a hazmat fee, I've heard that some do...:confused2:

Or you could buy from a launch site vendor.

I know the law is the law but it is really kind of silly. Vendors can't legally ship a load over 30 g (w/o hazmat fee) but can ship a pound of individually wrapped 30 g loads with no fee.
op:

I really don't want to hijack this thread, or be overbearing but one of the many hats I wear at work is supervising hazmat shipping, particularly of explosives, where the terminology is meaningful and legally binding If you don't do it properly, and legally, and you get caught, you're in a heap of trouble. The laws aren't silly, and that's why you can drive on the highway, fly on a plane, take a train trip or cruise on a boat which having to worry about being killed in a hazmat accident.

The laws concerning hobby riocket motor shipping require specified packaging that will minimize accidental ignition and projectile formation during an accident, and requires labeling, marking and documentation to identified the materials being shipped and the hazards associated with them. DOT requires significantly more paperwork than the USPS does because common carriers transport all types of hazmat. There are real expenses associated with hazmat transportation compliance and the dreaded hazmat fee is how the common carriers recoup their expenses.

• You ship stuff by common carrier. You mail stuff at the post office.
• A vendor can't legally ship rocket motors by common carrier (UPS, FEDEX, etc.) without paying a hazmat fee. I'm not going to go into the details of what it takes to ship rocket motors because it would take several pages, but it's not cheap and costs much more than jjust the hazamt fee. Whether the vendor passes the hazmat charges and other costs to you is up to the vendor. If he doesn't your lucky that he hasn't figured out how much the shipment really costs.
• A USPS authorized person can mail individually packaged motors and individually packaged reload propellant grains each not containing more than 30 grams of propellant if they follow the procedures listed below from https://pe.usps.com/text/pub52/welcome.htm

341.22 Mailable Explosives



The following specific types of explosives may be mailed only when the applicable conditions are met. Full responsibility rests with the mailer to comply with DOT and Bureau of Alcohol, Tobacco, and Firearms (ATF) regulations before mailing.

• Toy Propellant Devices. The proper shipping name for a toy propellant device is “model rocket motor” or “igniters.” A toy propellant device assigned UN0454 or NA0323 and classed as a Division 1.4S explosive is eligible for mailing in domestic mail via surface transportation only when prior written permission has been obtained from the Manager, Mailing Standards, USPS Headquarters, Washington, DC. A device approved for mailing is subject to the following conditions:
  1. Each device must be ignitable by electrical means only; contain no more than 30 g (1.07 oz) of propellant; and produce less than 80 newton seconds of total impulse with thrust duration not less than 0.050 second.
  2. Each device must be constructed so that all chemical ingredients are preloaded into a cylindrical paper or similarly constructed nonmetallic tube that does not fragment into sharp, hard pieces; must be designed so that it will not burst under normal conditions of use; must be incapable of spontaneous ignition under 500° F; and must not contain any type of explosive or pyrotechnic warhead other than a small, activation–charge, parachute–recovery system.
  3. Each mailpiece containing approved devices must be prepared for mailing following Packaging Instruction 1A in Appendix C. A shipper’s declaration for dangerous goods is required.

USPS Packaging Instruction 1A

Toy Propellant Devices

The proper shipping name for a mailable toy propellant device is “model rocket motor” or “igniter.” A device that is assigned identification number NA0323 or UN0454 and classed as a Division 1.4S explosive is eligible for mailing in domestic mail via surface transportation only, provided that all requirements are met and the device is properly packaged as follows.

Proper Shipping Name and ID Number

• Model Rocket Motors, NA0323.
• Igniters, UN0454.

Required Authorization

Prior written permission must be obtained from the Manager, Mailing Standards, USPS Headquarters, Washington, DC (see DMM 608.8 for mailing address).
Mailability

• International Mail: Prohibited.
• Domestic Mail: Permitted only via surface transportation sent as Standard Mail or Parcel Post and with prior approval. Each device must meet the specifications in 341.22a.

Design Specifications


Mailable devices must meet each of the following conditions:

• Each device must be ignitable by electrical means only.
• Each device must contain no more than 30g (1.07 ounces) of propellant.
• Each device must produce less than 80 newton seconds of total impulse with thrust duration not less than 0.050 second.
• Each device must be constructed so that all chemical ingredients are preloaded into a cylindrical paper or similarly constructed nonmetallic tube that does not fragment into sharp, hard pieces.
• Each device must be designed so that it will not burst under normal conditions.
• Each device must be incapable of spontaneous ignition under 500° F.
• Each device must not contain any type of explosive or pyrotechnic warhead other than a small, activation–charge, parachute–recovery system.

Required Packaging

Primary Receptacle

• Each device must be packed in a securely sealed primary receptacle.
• Multiple primary receptacles are permitted within a single mailpiece.
• Each primary receptacle must be surrounded by sufficient cushioning material to absorb shock and prevent breakage.

Outer Shipping Container

• A strong outer packaging that is capable of firmly and securely holding the primary receptacle(s) and cushioning material is required.
• Each mailpiece must not exceed a total weight of 25 pounds.

Marking

• Each outer packaging must be clearly marked on the address side with “Toy Propellant Devices,” followed by the applicable proper shipping name and UN or NA number. The markings “Surface Only” or “Surface Mail Only” and “Handle With Care” must also appear on the address side of the mailpiece. A DOT hazardous materials warning label must not be affixed.
• A complete mailing address and return address must be used.

Documentation

• A properly completed shipper's declaration for dangerous goods must be prepared in triplicate and affixed to the outside of the mailpiece.

Note: Full responsibility rests with the mailer to comply with DOT and ATF regulations before mailing. A legible photocopy of the Mailing Standards Manager's approval letter must be presented by the mailer to the postal acceptance clerk at the time of mailing.

 

[MarkH]

Thanks for the info Bob. What's silly is, or maybe arbitrary is the better word, is the 30 g limit. I'm sure this has been hashed an rehashed. But is an Estes E engine any more hazardous to ship than a D? Hardly. Or 25 pounds of bi furcated properly mailed G loads, less dangerous than a single 40 g F load. Not trying to be argumentative, it's just that the codes should be revisited. But that probably takes resources from the motor manufacturers and or the NAR to get things changed.

 

[Garoq]

I know that would have been the quicker way to get an answer, but since I ddin't think this was that pressing of an issue and I know that Gary frequents the forum... Didn't really think that it was worth interupting him with a phone call for a question that I don't need answered ASAP.

As a manufacturer myself, I enjoy answering questions about my products online, if it's important enough for one person... That also avoids the speculation part.

We tried a bifurcated F40W some time ago and found that the time delays weren't repeatable for some reason. The short grains exhibit a really long tail-off relative to the overall burn time, that may adversely affect the timing of the delay.

Now if the users could reliably epoxy the grains back together, that might work...

 

[Rocketjunkie]

We tried a bifurcated F40W some time ago and found that the time delays weren't repeatable for some reason. The short grains exhibit a really long tail-off relative to the overall burn time, that may adversely affect the timing of the delay.

I much prefer the original single grain G64 over the 2 piece grain. It's not the loss of the 5 N-s but the fact the new version is very strongly regressive with a much higher initial thrust. Although the total impulse and burn time are within the NFPA variation limits so recertification wasn't necessary, the thrust curve is very different. All you have to do is watch flights with the one piece grain vs. the 2 piece grain and the difference is obvious. Since the F motors still require hazmat, let's go back to the original G motors, even though they require hazmat shipping.

 

[Garoq]

I much prefer the original single grain G64 over the 2 piece grain. It's not the loss of the 5 N-s but the fact the new version is very strongly regressive with a much higher initial thrust. Although the total impulse and burn time are within the NFPA variation limits so recertification wasn't necessary, the thrust curve is very different. All you have to do is watch flights with the one piece grain vs. the 2 piece grain and the difference is obvious. Since the F motors still require hazmat, let's go back to the original G motors, even though they require hazmat shipping.

Retailers were insisting that we convert as many products as possible to USPS-shippable, so that was the main reason for the change.

Epoxy the grains back together with 5-minute and you have the original.

 

[cosmodrome]

Now if the users could reliably epoxy the grains back together, that might work...

What about epoxying one end of each grain at Aerotech and shipping in seperate bags? I know that this would add a step to the manufacturing and add some cost to the motor, but if it offset the hazmat fee... Even though the grains arn't epoxyed together, would this still have the same effect by inhibiting burn on two ends? Oh course, even if this works, there would now be 4 ways to assemble the grains.

 

[Garoq]

What about epoxying one end of each grain at Aerotech and shipping in seperate bags? I know that this would add a step to the manufacturing and add some cost to the motor, but if it offset the hazmat fee... Even though the grains arn't epoxyed together, would this still have the same effect by inhibiting burn on two ends? Oh course, even if this works, there would now be 4 ways to assemble the grains.

I think that most people are happy with them the way they are now, for those that want them in the old style they have that option, and I don't want to add more to the cost.

I haven't tried it but a layer of grease between the grains might be just as effective...

 

[cosmodrome]

Ya, it just stinks not being able to get F's without paying extra for shipping. I don't have an on-site vendor, nor do I fly enough F's to make the hazmat fee worth it. guess I'll just have to wait until I have enough bigger motors to order and remember to stock up on them.

 

[Donaldsrockets]

Most of the RMS F motors I fly are the 24mm.

Try the F35W sometime, awesome little motor.

I also love the F39T, 3..2..1..BANG, it's gone!!!

 

[dpower]

We tried a bifurcated F40W some time ago and found that the time delays weren't repeatable for some reason. The short grains exhibit a really long tail-off relative to the overall burn time, that may adversely affect the timing of the delay.

Now if the users could reliably epoxy the grains back together, that might work...

Thanks for this informative answer Gary, I was wondering what was driving the decision. Its nice to know that there was an effort to solve this issue, and that there is a good technical reason for maintaining the single grain.

 

[Bill P]

Most of the RMS F motors I fly are the 24mm.

Try the F35W sometime, awesome little motor.

I also love the F39T, 3..2..1..BANG, it's gone!!!

The F39T is a fabulous motor.