WTB Hobby line reloadable casings

[RocketDog]

I am looking for a used set of RMS casings 18mm, 24mm and 29/40-120 with enclosures.

[ghrocketman]

Every once in a great while you will see someone selling used hobby-line cases on ebay, but it is VERY rare & usually only happens when someone leaves the hobby altogether.

More often one can find used HPR 29 and 38mm cases & closures.

I think the HPR cases are more commonly for sale due to fewer and fewer people willing to put up with the ridiculous draconian regulations imposed by the BATFE requiring Low-Explosive Use Permits for NON EXPLOSIVE rocket engines just because they contain some equally ridiculous arbitrary limit of over 62.5gr of propellant.

[RocketDog]

With any luck someone will spot my ad. Thanks for the advice! I'm watching ebay too.

[Race58]

You can buy a whole new set of Aerotech at Hobbylinc for $134.19

http://www.hobbylinc.com/htm/aro/aro91849.htm

Or a Rouse Tech set for 112.95 at Red Arrow

http://www.redarrowhobbies.com/rouse-tech.htm

[RocketDog]

Yes, thank you. Thats why I advertised for a used set.

[ghrocketman]

I bought one of my RMS24 cases used and my RMS180/240 used.
Quite frankly, for the amount of materials contained in any of the hobby line cases the prices are ridiculously EXCESSIVE for any mass produced item.
You get a tube worth about 15 cents with fine threads cut at each end (maybe 50 cents tooling, engineering, and labor cost per case) and a couple of closures that could not have more than $3 total in material and labor/engineering costs. Add that together and you are at about an estimated lets say $3.65 cost.
Add say $2 to that cost for liability insurance, executive salaries, and other no-value added GARBAGE costs (and I think even that $2 is WAY high) and you are up to $5.65 for each Hobby-Line case.
Add a profit of $3 to that to get a $8.65 sales price to the un-needed zero-value-added middle man distributor (selling directly to the retailer is ALWAYS much better for the consumer)
The middle man than doubles that price to all the hobby shops, and web stores so they buy them for around $17.00 and then they still want over $35 each when selling to customers.
most costs in virtually any hobby result from distribution channels, middlemen, and other Zero-value add garbage fees.
Most companies would make more $$$ and customers would be much happier spending less $$$ for any given product if companies would directly sell to individuals for 15% above what they sell to distributors. The distributors would be cut out of business and customers would be happier as well.

[RocketDog]

$112 for the set is a lot.

[Doug Sams]

Yes, thank you. Thats why I advertised for a used set.My experience is that the hobby line cases are rarely available used. I tried to find a used 24mm once, and got 0 hits. I think that's partly why you're getting pointers to new stuff - others have struck out trying the same tactic.

If you do buy new, IMNSHO, you can forego the 18mm case and save a bit.

Yeah, there are a couple good applications for it. I have at least two birds in my fleet that could really use it. But there are a zillion applications for the 24 and 29 mm cases. They're way more useful.

Doug


.

[RocketDog]

Thats good advice. I'm mulling over different options like that. Someone did have the 24 and the 29 hobby line on ebay, but they wanted almost what the new ones are selling for.

[ghrocketman]

In my opinion, the 18mm RMS is the ONLY way to get any sort of a decent flight out of an Estes or Semroc Mars Lander since the demise of the Estes C5-3.
There are NO decent 18mm single-use BP model rocket engines that a Mars Lander can fly safely in ANY wind with.
The C6-3 will fly a Mars Lander in zero wind to a lack-luster low flight.
The B6-2 (why has this ever been on the engine list for the ML) more often than not results in a chute pop about 20' above the ground with the corresponding junk-heap trash-bag recovery of the ML.

I REALLY like the Semroc Mars Lander in that it does faithfully reproduce the Estes kit, but I wish they would have made the kit the way Estes SHOULD have, with 24mm power. It really needs it with the drag/weight it has.

Every once in a while I send up one of my Mars Landers with one of my 30+year hoarded supply of 18mm SU BP Cox D8-3's; that engine bar-none was the best BP SU engine for the Mars Lander.
I wish Aerotech would return the 23 n-sec RMS 18 "baby E" to the offerings for this case.

[RocketDog]

Will the C11-3 lift the ML?

[Doug Sams]

Will the C11-3 lift the ML?It will...IF you built it with a 24mm mount, in which case you have lots and lots of effective motor options (in addition to the C11).

Doug

.

[ghrocketman]

The C11-3 certainly will lift the ML, but if you had a 24mm mount I don't see why anyone would choose it over a D12.
It won't go very high on a D12 with only 17n-sec of total impulse.
It doesn't go very high on the Aerotech 18mm full 20n-sec D's.

[RocketDog]

Whats your definition of really high? Heh heh, semroc claims 350 feet on a C6-3 is that rocksim numbers, is rocksim incorrect? I kinda would expect that a D would put this up to 1000 feet..

[ghrocketman]

I'd guess a full-20nsec-impulse Aerotech 18mm RMS "D" doesn't put it much over 600'....it is REALLY draggy.
An estes D12 with it's lower 17 n-sec total impulse and higher weight being 24mm would probably only go 500' MAX.
I do not consider that very high.

I highly doubt a C6-3 hits 350'....my guess is more like 250-300' tops.

[RocketDog]

The rocksim data may be off. My original ML (1st Ed.) didnt fly very high either as I recall.

[ghrocketman]

I do know mine flies about 50' higher on a C5-3 vs. a C6-3.
Brilliant that they kept the C6-3 around instead of the C5-3 huh ?

[RocketDog]

One for the books, IMHO

[ghrocketman]

Yep, one for the books....

Now if we could just get someone to start manufacturing a SU BP 18mm and 24mm engine line that has some REAL variety and "specialty" engines we would be all set....

[RocketDog]

Hmmmm maybe a letter writing campaign to Estes and Quest would do the trick, or maybe Aerotech! Or if I win the powerball... (yeah thats gonna happen)

[ghrocketman]

Don't even bother writing/campaigning to get Estes to offer different rocket engines.
If you are lucky they will listen THEN ignore the request, if not lucky they won't even listen.
Rocket Doctor was a consultant to Estes and tried for quite some time to zero avail.

[RocketDog]

Well that still leaves two alternatives.

[RocketDog]

Hmmmm, I will have to go 24mm with the ML. The rocksim data is incorrect. Here are my calcs for the ML using another altitude software that confirms whats reported in this thread.

First the B6
Air density CF = 1.000

Number of stages = 1

Lift-off weight = 4.780 oz
Total burn time = 0.830 sec

*** Stage 1 ***

Engine type: B6-2 [1 engine(s)]

Engine weight: 0.680 oz
Propellant: 0.220 oz
Average thrust: 21.573 oz
Thrust duration: 0.830 sec

Rocket weight: 4.100 oz
Rocket diameter: 3.744 in
Rocket drag coef.: 0.750

Burnout altitude: 36.630 ft
Burnout velocity: 80.995 ft/sec
Altitude gained after burnout: 61.302 ft
Coast time: 1.803 sec

Total altitude: 97.932 ft
Peak altitude time: 2.633 sec

Crash city.

The C6 is next
Air density CF = 1.000

Number of stages = 1

Lift-off weight = 4.980 oz
Total burn time = 1.700 sec

*** Stage 1 ***

Engine type: C6-3 [1 engine(s)]

Engine weight: 0.880 oz
Propellant: 0.440 oz
Average thrust: 21.573 oz
Thrust duration: 1.700 sec

Rocket weight: 4.100 oz
Rocket diameter: 3.744 in
Rocket drag coef.: 0.750

Burnout altitude: 122.949 ft
Burnout velocity: 113.568 ft/sec
Altitude gained after burnout: 91.242 ft
Coast time: 2.114 sec

Total altitude: 214.191 ft
Peak altitude time: 3.814 sec

Thats better, but here is some 24mm data

The C11 didn't lift it as high, I have to check my data and redo
Air density CF = 1.000

Number of stages = 1

Lift-off weight = 5.240 oz
Total burn time = 0.810 sec

*** Stage 1 ***

Engine type: C11-3 [1 engine(s)]

Engine weight: 1.140 oz
Propellant: 0.390 oz
Average thrust: 39.047 oz
Thrust duration: 0.810 sec

Rocket weight: 4.100 oz
Rocket diameter: 3.744 in
Rocket drag coef.: 0.750

Burnout altitude: 61.792 ft
Burnout velocity: 134.075 ft/sec
Altitude gained after burnout: 111.795 ft
Coast time: 2.299 sec

Total altitude: 173.587 ft
Peak altitude time: 3.109 sec

The D9 aerotech rms
Air density CF = 1.000

Number of stages = 1

Lift-off weight = 5.680 oz
Total burn time = 1.880 sec

*** Stage 1 ***

Engine type: D9-4 [1 engine(s)]

Engine weight: 1.580 oz
Propellant: 0.350 oz
Average thrust: 35.883 oz
Thrust duration: 1.880 sec

Rocket weight: 4.100 oz
Rocket diameter: 3.744 in
Rocket drag coef.: 0.750

Burnout altitude: 207.854 ft
Burnout velocity: 160.873 ft/sec
Altitude gained after burnout: 139.715 ft
Coast time: 2.522 sec

Total altitude: 347.569 ft
Peak altitude time: 4.402 sec

and now the Estes d12
Air density CF = 1.000

Number of stages = 1

Lift-off weight = 5.590 oz
Total burn time = 1.670 sec

*** Stage 1 ***

Engine type: D12-5 [1 engine(s)]

Engine weight: 1.490 oz
Propellant: 0.880 oz
Average thrust: 36.710 oz
Thrust duration: 1.670 sec

Rocket weight: 4.100 oz
Rocket diameter: 3.744 in
Rocket drag coef.: 0.750

Burnout altitude: 185.369 ft
Burnout velocity: 163.150 ft/sec
Altitude gained after burnout: 132.129 ft
Coast time: 2.426 sec

Total altitude: 317.499 ft
Peak altitude time: 4.096 sec