Re: Pros and Cons to buying a motor now

[redsox15]

Hi all,

I am looking to purchase a motor for my lvl 2 cert flight (Aerotech J570 to be exact) and was wondering what the pros and cons would be to buying the motor now if the flight wasnt going to be until june (granted I pass the test first). Right now I can purchase the motor for $60 if I pre order it meaning it will not get shipped out until December so I will be sitting in my house from mid December until June. Anyone done this before? Suggestions?

edit: the pre order offer ends in October so that is why I would be buying it now instead of closer to the launch

Matt

[madsen]

Go to Balsa Machining Service and pay $51.74 any day of the week.

[WillMarchant]

Motor vendors pretty regularly come out with "certification specials" with hardware and reloads at reduced prices. You might want to wait for that next cycle...

[Rocketman248]

edit: the pre order offer ends in October so that is why I would be buying it now instead of closer to the launch

Matt

I'm assuming you're talking about Balsa Machining's pre-order deal. They always have a pre-order. There will still be 1-3 cycles before June.

If you did order it now, it wont be a problem. Just keep the package sealed. I've had motors for much longer than that.

[redsox15]

I'm assuming you're talking about Balsa Machining's pre-order deal. They always have a pre-order. There will still be 1-3 cycles before June.

If you did order it now, it wont be a problem. Just keep the package sealed. I've had motors for much longer than that.

Yes I was talking about the Balsa Machine deal. I did not know that they have multiple pre order deals thanks for the heads up!

Matt

[cjl]

Don't worry about it. Just keep the motor sealed, and you'll be fine.

[Rocketman248]

BTW. Excellent motor choice! It's a sweet motor.

[jadebox]

I don't think it's really a good idea to order the reload too far in advance - especially if you're still working on the rocket. I've designed rockets for a specific motor only to have the rocket end up too heavy for that motor.

But, you might want to buy (or borrow) the casing for the motor you think you'll use. You'll find having it on hand makes it easier to build and test your motor mount and motor retention system. It's also nice to have a length of the right size launch rod or rail onhand while building the rocket. It beats getting to the launch pad and finding out that something doesn't fit or line up right.

-- Roger

[cjl]

I'd be fairly surprised if the rocket ended up too heavy for a J570 - it's quite a violent motor off the pad, and it'll pick up a lot more than an average 38mm J.

[redsox15]

The rocket that I'm building weighs 168Oz (10.5lbs) w/o the motor says rocksim but I know that it could be +/- the rocksim weight because I am using different tubes and making my own nose cone. The sims say it will fly ok on other Js but its a little slow off the pad and flying to about 2000' on the J570 its flying to roughly 3200'. I am building it with a 54mm mount but a 54mm motor is not in my budget right now so I'm chose on one of the biggest 38mm Js I can find. I may wait for another round of the pre order deals so that (a) it is not sitting around my house for a long period of time and (b) the rocket is still a shell so the actual weight is not known yet. Once most of the rocket is assembled I can check and make sure my motor choice will work.

Thanks for all the help!

Matt

[Brent]

I'm assuming you're talking about Balsa Machining's pre-order deal. They always have a pre-order. There will still be 1-3 cycles before June.

If you did order it now, it wont be a problem. Just keep the package sealed. I've had motors for much longer than that.

On the pre-order, do they charge your card when your order or when it is ready to ship?

[Rocketman248]

When you order.

[jadebox]

I'd be fairly surprised if the rocket ended up too heavy for a J570 - it's quite a violent motor off the pad, and it'll pick up a lot more than an average 38mm J.

I was making a general comment on the subject, but chose a specific example from my experience. My point was that some situation may change his choice of motor. For example, maybe his rocket will turn out too light for the motor.

Funny, though, I've never had that happen. :-)

-- Roger

[MarkII]

Most of the reloads and SU motors that I have on hand are at least 3-4 years old. I have some that I bought when I first became a BAR (6+ y. a.) that I haven't burned yet. But I have never obtained a reload or a single use composite motor that wasn't at least a year old at the time that I bought it. Most seem to be around 2 years old at the time of purchase. None of them have ever caused me any problems, though. I don't know that one can ever be assured of obtaining a "fresh" motor through random ordering, or that "freshness" even makes any real difference.

[cbrarick]

That's a sweet motor....should be great in you rocket. I've got a J460 I'm going to throw at my wildman dd - about 13 pounds worth...and I'm sure it will be fine. looking for around 3800 feet, which would be a perfect cert flight.

rick

[G2Rockets]

The rocket that I'm building weighs 168Oz (10.5lbs) w/o the motor says rocksim but I know that it could be +/- the rocksim weight because I am using different tubes and making my own nose cone. The sims say it will fly ok on other Js but its a little slow off the pad and flying to about 2000' on the J570 its flying to roughly 3200'. I am building it with a 54mm mount but a 54mm motor is not in my budget right now so I'm chose on one of the biggest 38mm Js I can find. I may wait for another round of the pre order deals so that (a) it is not sitting around my house for a long period of time and (b) the rocket is still a shell so the actual weight is not known yet. Once most of the rocket is assembled I can check and make sure my motor choice will work.

Thanks for all the help!

Matt

If you sim out at 3200 feet with the j570, I think you'll be golden. that's low enough for a apogee deploy. I apogee deployed my level 2 at 4400 feet and watched it the whole way. Your average thrust to weight ratio looks real good.

If you can wait until spring to pick up the motor, it is just that much less time that you have to keep it dry. otherwise I have had them that long and never had problems.

Let it rip and send us pics!!!

John

[RandyT0001]

In May I think I bought one of the last "38mm Specials" from Aerotech's first production run from Performance Hobbies and a 38/720 motor on sale. With this combination I could cert Level I and II with 38mm reloads. Unfortunately the J reloads for the 38/720 are small, just barely into the J range. So I started to look at the various 54mm motors from various rocketry retailers. After some research I determined that the 54/1706 motor with 54mm reload adapter system offered the most reload choices, expanding across the J class into the bottom third (or thereabouts) of the K class of impulse. I come across this thread about motors and BMS's pre-order sale was mentioned so I check it out. After some quick comparisons three combinations of motors/casings, aft closures, and the proper sized reload adapter system I find appealling based upon price and the wide number of available reloads. I don't work for BMS just pointing out what I consider to be good deals.


First is the 38mm combination. It almost recreates what I bought from Performance Hobbies in May. With this combination there are 28 reloads available. Useable 38mm Reloads: G61W, G67R, H73J, H123W, H170M,
H242T, H148R, H112J, I161W, I218R, I245G, I357T, I154J, I211W, I225FJ, I285R, I300T, I195J, I284W, I305FJ, I366R, I435T, I364FJ, I600R, J340M, J350W, J420R, J500G

Catalog #	Item						Pre-order Price ($)
3872M		RMS-38/720 Motor (Includes Forward Seal Disc)	 54.74
3836C		38mm 360 N-sec Casing				 30.00
38RAS		38mm Reload Adapter System			 22.49
								------
38mm Sub-Total							107.23	(+$6 S&H)=	113.23

	Option
38AC2 		Extra 38mm Aft Closure (Prep 2 motors)					 28.50
											------
											141.73

Costs less than the pre-order RMS-38/240-480 System at 148.50 w/S&H that can service only fourteen reloads, one at a time, "straight out of the box".

Second is the 54mm combination. This is the one I pre-ordered for future expansion into larger J's and lower end K's. With this combination there are 14 reloads available. Useable 54mm Reloads: J180T, J250FJ, J275W, J315R, J460T, J401FJ, J415W, J540R, J800T, K513FJ, K540M, K550W, K695R, K1100T

Catalog #	Item						Pre-order Price ($)
5417C 		54mm 1706 N-sec Casing (Includes fwd Seal Disc)  90.00
54RAS 		54mm Reload Adapter System 			 37.49
54ACC 		54mm Aft Closure 				 33.75
								------
54mm Sub-Total							161.24		(+$6 S&H)=	167.24

Costs less than the pre-order RMS-54/852-1706 System at 257.25 w/S&H but can service the same reloads "straight out of the box" but at a savings of $90.01

The third combination is made by adding the two above together. There are five power ranges (G thru K) with three casings. It's capable of having two motors pre-prep'd before flight. It spans two high power levels (I and II) and has 42 available reloads (28 in 38mm and 14 in 54mm).

38mm & 54mm Combination Sub-Total				268.47


BMS On-line orders S&H						  6.00
								------
								274.47

Add $17.22 to the cost of the pre-order RMS-54/852-1706 System at 257.25 w/S&H and you get both the 38mm and the 54mm bargains.

	Optional Additions
38AC2 		Extra 38mm Aft Closure (so 3 HP motors can be prep'd early)	 28.50
										------
										302.97


T082510-1 	RDDT (Rms Delay Drilling Tool) RMS & RMS PLUS 	 		 11.24
										------
										285.71

Both 38AC2 (38mm aft closure) and T082510-1 (Rms Delay Drilling Tool)			 39.74
											------
											314.21

For those stuck with 29mm motor mounts there is this combination.

Catalog #	Item							Pre-order Price ($)
2924CA 		29mm 240 N-sec Casing (Includes Forward Seal Disc) 	41.25
29AC2 		29mm Aft Closure 					15.00
29RAS 		29mm Reload Adapter System 				22.49
									------
									78.74
BMS On-line orders S&H						  	 6.00
									------
									84.74

Costs less than the 29mm RMS 60-120 or 180-240 Systems but offers more reloads than either.

Useable 29mm reloads (11)
G79W, G77R, G75J, H128W, H165R, H238T, H97J, H180W, H220T, H210R, H250G

If you are looking to make the move from low/mid power into high power next year maybe one of these appeals to you. If you pre-order before Nov 1st they will start to ship at the beginning of December, just in time for gift giving holidays. But who knows? There might be a big certification push/sale by all the retailers come next spring.