Im starting to build larger rockets. I thought i would just go ahead and invest in a reloadable system because i plan on launching often.

I have a few questions.

Is it true that anything above the RMS-24mm F-39 requries a hazmat fee to ship?
Where can one buy motors for the longer Rouse-tech casings?

With what im building right now i would probably launch it on the 24mm F-39. That would reach around 800 feet according to rocksim.

Would i be better off getting a 29mm reload case if i plan on launching these larger rockets? I know these only come in 1 pack reloads though.

Is there a way to modify the longer Rouse-tech casings to accept shorter 29mm motors?

If I'm not mistaken, the 24/40 and 29/40-120 (ie, hobby cases) reloads all fall in the under-30g-per-slug range and are hence free of hazmat fees.

Some older reloads, the G33 for example, used one piece slugs which exceeded the 30g limit, but newer reloads have been engineered using smaller, multiple slugs. The total propellant mass is approximately the same, but the multiple, smaller slugs enable them to be shipped USPS and hazmat-free.

Specifically which cases?

Frankly, IMHO, you should buy both the 24/40 and 29/40-120 cases. You have lots of option between them. The 18mm case is not so compelling.

Generally, no. But, which cases are you specifcally asking about?


Doug


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I guess i just dont really understand how the 29/40-120 rouse-tech compares to the RMS 29mm D E F casing.

Do they take different motor reloads?

Im asking about any thats longer than the RMS 29mm D E F casing.

The 29/40-120 takes E-F-G loads. The lower impulse grains (slugs) are short. The higher impulse loads have multiple grains (or longer grains for some of the older loads). The grains slide into a liner tube which in turn slides into the motor case. For the short loads, a spacer tube also slides into the liner. The higher impulse loads completely fill the liner.

With the other 29mm cases (29/60, 29/100 and 29/120), no spacers are employed. The 29/60 uses one grain. The 29/100 uses 2 odd-length grains (or one normal and one short). The 29/120 uses two grains identical to the one used in the 29/60.

The HPR versions (29/180, 29/240, et al) just use more of the same grains as are used in the 60 and 120. Instead of spacer tubes, the motor length is varied thus requiring the user to have multiple sizes of motor cases.

The advantage of the 29/40-120 system is that you get three ranges of impulse - 40, 80 or 120 - with a single case. You cover pretty much the same range of motors as you would get having the other three (29/60, 29/100 and 29/120).

The key difference is the closures. The 29/40-120 closures are different than those used on the 29/60...29/240. They are not interchangeable.

FWIW, I own only the 29/40-120 (& 24/40).

For the bigger stuff, I skipped to the 38mm line. IMO, the 29/40-120, 38/120, 38/240 and 38/360 cases cover the same range of impulse and give me about the same variety as having the entire 29mm HPR line. That is, I can get about the same impulse and propellant options and also have the added ability, using the longer 38mm cases, of flying HPR up to hefty J's (J570).

As long as you put 38mm motor tubes in your mid-power/H-I class birds, you can get by without needing any 29mm cases other than the 29/40-120.

For me, after reviewing all the reload options for the 29mm and 38mm HPR lines, I decided that the 29mm HPR line (including the 60-100-120) didn't really offer anything special not already covered by the 29/40-120 and low end 38's.


Doug


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I say go for them. If you plan on getting into MPR or overpowering kits (make sure you have a big field), then these will really come in handy. Rousetech cases are of superb quality if they are taken care of properly. Some reloads need HAZMAT, like the F40 for example, but newer motors like the G71 or the redesigned G64 have two grains to eliminate HAZMAT. Although HAZMAT is usually $20, it's worth it. Places like Hobbylinc sell reloads for so cheap, that your savings can basically pay for the HAZMAT. Other places like BMS have normally priced reloads, but pay for the HAZMAT if the motor order is $150+. And then, there's the usual places that have reloads for decent prices, not the best or worst, and you have to pay HAZMAT no matter what. I would also get the entire Hobbyline set (18/20, 24/40, 29 40/120) for a variety of motors. The 18/20 could be used for the usual kit with an 18mm mount, like the Big Bertha. Faster, higher, louder flights is basically what the 18/20 can give. The 18/20 has two reloads; the D13 and D24, which are the same size as Estes/Quest 18mm motors. The 24/40 can be used with kits using 24mm mounts, like the Big Daddy. The 24/40 case is the same size as Estes 24mm motors and can accept the D9, D15, E11, E18, E28, F12, F24, and F39 reloads. Remember, for those two cases to fit a motor mount with a motor hook, the top part of the hook that sticks into the motor tube as an anchor and motor block must be filed down a bit for the ejection cap (holds the ejection charge in the motor) to fit. The 29 40/120 is the biggest Hobbyline case available. It is around 5.5" long and can accept many reloads. It accepts the E18, E23, F22, F40, F52, G53, G64, G71, and the soon to come G76. Also, keep in mind that all Aerotech/Rousetech cases do not need a motor block at all. The aft closure has a lip the is a bit larger in diamter than the rest of the motor that acts as a motor block since it will prevent the motor from going any farther into the tube. As long as positive motor retention is used (for example, Kaplow clips [mirror clips that are secured with small screws via T-nuts through the centering ring; plywood rings would be best for this], the wire-like motor clips that have zip ties or twist ties around the motor/clip, etc.), the motor cases will save a bunch of money when compared to single use AP motors. Positive motor retention will keep the motor secured in the rocket so it will not kick out. Reloads are packed with a more powerful ejection charge, enough to pressurize the body tube to a certain extent that it will kick the motor out of the back, even with a motor clip (without zip/twist ties, which will ensure that the clip will not bend back). As for shortening the cases for shorter 29mm reloads, that cannot be done. However, you can purchase the Easy Access cases that use F and G reloads (the 29/60, 29/100, 29/120, 38/120). The 29mm Easy Access cases that use F and G reloads are all shorter than the 29 40/120 except for the 29/120. However, the 29/120 is only about .1 inch longer than the 29 40/120. These lengths that I am using right now include only the case and forward closure. But IMO, I don't think you'll need to worry about motor length. As long as the motor tube is longer than about 5.5", there is nothing to worry about (besides, any rocket big enough to use 29mm motors will probably use a motor tube of more the 5.5", usually even longer).

__________________
Josh
NAR #87993

I've never seen studies using a big empty void in a casing, but I'd think it would screw up the numbers at the very least. I do know that individual grains will center themselves and still burn evenly on each end if there's a bit of slack for them to move, but I wouldn't want several inches of space in there.

The only way I could see using long cases for short motors to work well is to turn a big long bulkhead to fit down inside the tube, effectively making it a shorter casing. This would work great for everybody's cases except the Aerotech/Dr. Rocket/Rouse Tech cases that use screw cap end closures. Since cases are easier to make than end closures, it would make a lot more sense to have multiple length tubes instead of end closures.

Re-reading your question, I get a different take, so let me try this: The RMS D-E-F case is the 24/40. The 29/40-120 is an E-F-G case. Both cases are available from Aerotech and from Rouse. The same reloads are used for both vendors' cases.

(Comparisons of the 29/40-120 to the other 29mm (HPR) cases are in other posts.)

Doug

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WARNING! Long post follows!
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Let me begin by stating that I am a fan of reloadable motors; I have reload motor casings that range in size from 24 to 38 mm, and I would not want to have to fly without them. With that being said, if you want to get into composite propellant motors, one way to get started is with single use (SU) motors. There are 18 mm D motors available from Aerotech and Apogee Components, 24 mm E and F motors from Aerotech, Apogee and Ellis Mountain; EM also makes a 24 mm G! The 29 mm diameter is where you will find the largest variety of single use motors; in addition to the three previously mentioned companies, 29 mm single use motors are also available from Road Runner. Motors in this diameter range from E to G. Aerotech has a line of 3.75" long (same length as an Estes E9) 29 mm F and G motors called Econoline motors that are sold in 2-packs; these are less expensive per motor than equivalent-impulse SU motors sold individually. Ellis Mountain SU motors are also usually among the least expensive single use composite propellant motors available.

The main advantages of single use motors are their lower initial cost and their ease of use. Because you don't have to purchase an expensive reload casing, the per flight cost of using SU motors is less than that of equivalently powered reloadable motors for the first few flights. If you plan to fly mid-power rockets on composite motors only occasionally, then single use motors make more sense from an economical standpoint. Yes, although reloadable motors really do lower the cost of flying with composite propellant eventually, you will have to use them fairly often to recoup the high initial expense. Which is fine if you already have or are planning to eventually build a fleet of more than a few mid-power rockets and are planning to do a significant amount of your flying with them. And you had better plan on doing all or most of that flying on large fields with no nearby obstructions (trees, power lines, rivers or large bodies of water) and that possess favorable wind patterns, because nothing will raise your cost-per-flight like losing the rocket that contains your just-purchased reload casing (or by having the ejection charge kick the casing out at 1200 ft.).

The other main advantage of SU motors is their ease of use. Basically, that boils down to this: no assembly required! Yes, knowing how to assemble an RMS motor is a good thing to learn (and is surely in your future if you stick with mid-power rocketry), and yes, it is not all that hard to do (building your rocket is harder). But keep in mind that to build an RMS-type motor (Aerotech, Rouse-Tech or Dr. Rocket), you will need a place to work that is calm (not rushed), relatively distraction-free, and, most importantly, clean. Not always so easy to find at the range, especially if you also have to do range duty, for instance, or if you need to keep an eye on the kids. Not impossible, though; in fact, if (or when) you go for your certification, you will have to assemble your motor at the range. CATO's involving mid-power composite propellant motors are relatively rare, but when they do occur, they almost always involve improperly-assembled reload motors (which can usually be traced to dirt contamination on the O-rings or on the threads of one or both of the enclosures). In your first few composite motor flights, you can dispense with this step by just using SU motors, which will leave you time to focus on other things, like prepping your rocket and getting that all-important pre-flight photo taken of you either holding or standing next to your beautiful space-bound creation. The most assembly that you will have to do with an SU motor is to make a thrust ring on the aft end with masking tape.

Oh, one other thing: you can purchase any of the available mid-power SU motors without certification, an LEUP, or the need to pay a hazmat shipping fee.

You will probably receive plenty of advice from this forum on the uses and advantages (and there are many of them) to using reloadable motors (and remember that I am a fan of them, too). I just wanted to present the case for the alternative of flying with single-use motors, at least at first. I do apologize for the long post, but I wanted to get everything said on behalf of that alternative in just one post.

Mark

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SAM # 0011

Mark, AFAIK, most of the 29mm SU motors will need hazmat, or at least should have it, but some vendors may not be shipping properly. While the hazmat threshold for reloads is the grain weight, for the SU motors, it's the total propellant weight. Any motor over ~60Ns will have over 30g of propellant and thus be ineligible for USPS and hence have to be shipped UPS with a hazmat fee.

Some vendors have been known to ship things like the E9 or old G33 via USPS, but should not have been doing that.

Doug


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Excellent information! Thanks a bunch. I'll probably start out with the 29/ 40-120