Question: Slightly bigger launch pad and controller?

[bobdros]

I have the standard Estes launch pad and controller. I'm ready to launch my Der Grosser Vati (Big Daddy) and I'm just about ready to take the plunge and launch my Saturn V that's been in the works for about the past 8 years.

I've read mixed reviews about the Mantis and it's a tad expensive. I'm also not sure about the Aerotech controller. Would the next size up Estes pad and controller be suitable for bigger rockets like these? How about the length of the launch rod? What's the best size (diameter and length)?

I also bought a 2001 Saturn V from eBay and I'd like to build it to get a bit higher. I'm not sure if I should cluster it. If I DID cluster it, should I get the Aerotech controller? And If I did, what would I have to do to make it work with my smaller rockets and igniters (B6-4s, C6-3s, etc.)?

[stefanj]

I wasn't impressed by the Mantis.

You could try building your own launcher. There are lots of designs out there, using PVC pipe and the like.

Something that can handle 1/4", 3/16", and 1/8" rods would be ideal. A 4' long 3/16" diameter rod is a good choice for mid-power rockets, including the Saturn V.

A controller built for 12V is what you're looking for. 25' of zip cord, battery clips, push button, key switch, continuity light, etc. should run you much less than a commercial launcher and be way sturdy. You can use your car battery, or spring for a motorcycle or mower battery.

[Shreadvector]

I wasn't impressed by the Mantis.

You could try building your own launcher. There are lots of designs out there, using PVC pipe and the like.

Something that can handle 1/4", 3/16", and 1/8" rods would be ideal. A 4' long 3/16" diameter rod is a good choice for mid-power rockets, including the Saturn V.

A controller built for 12V is what you're looking for. 25' of zip cord, battery clips, push button, key switch, continuity light, etc. should run you much less than a commercial launcher and be way sturdy. You can use your car battery, or spring for a motorcycle or mower battery.

NAR MRSC and NFPA code = 30 feet of wire to the pad for 30 N-s or more installed total impulse.

3/4" Schedule 40 PVC pipe. 4 legs 2 feet long inserted into a central cruciform PVC union. Drill a 1/4" hole for the rod. Secure the rod with a shaft collar above and below the PVC central hub. Use a deflector of your choice - pot lids are great as are ceramic flower pots. Cost is around $10.

I've made a LOT of these pads for local TARC teams to use.

[Feyd]

I built a pad not long ago out of PVC and it's working out great for me. It was more expensive than the one mentioned above, but it also has multiple holes of different sizes so I can launch from all three common lowpower sized rods.

Multi-rocket Launch Pad (http://spotteddragon.com/dungeons/launchpad.html)

Also, I bought 4' launch rods from an on-line metals company and they are working out well. They came shipped in a sturdy tube and all were straight. Inexpensive rods but shipping was a little much (at least to me).

Launch Rod Steel (http://www.speedymetals.com/c-8227-cold-finished.aspx)

Any questions, let me know.

Another nice thing about my launch pad is I can put it together with only one of the crosspieces if I'm not doing a bunch of launches. Easy to assemble, store, and transport.

[Jerry Irvine]

PVC union. Drill a 1/4" hole for the rod. Secure the rod with a shaft collar above and below the PVC central hub.
http://www.amazon.com/Climax-Metal-C-025-Shaft-Collar/dp/B000IL82SI

http://www.amazon.com/Cold-Rolled-Steel-Rounds-Alloy/dp/B001W26V9E/ref=sr_1_4?s=industrial&ie=UTF8&qid=1282157472&sr=1-4

[bobdros]

Thanks for the recommendations! I read that the Saturn V might experience something like launch suck if it's too close to the deflector. Apparently it creates a kind of vacuum and it doesn't launch. Is this something I can do something about with the design of the launch pad?

[Shreadvector]

Thanks for the recommendations! I read that the Saturn V might experience something like launch suck if it's too close to the deflector. Apparently it creates a kind of vacuum and it doesn't launch. Is this something I can do something about with the design of the launch pad?

If using a flat deflector, simply make sure the aft end of the rocket is a few inches above the flat deflector so you don't get Bernoulli Lock.

Do this by propping it up with a few spent motor casings or use tape on the launch rod.

http://rocketry.wordpress.com/2006/10/17/the-krushnic-effect-and-the-bernoulli-lock/

[Jerry Irvine]

If someone has a better basic schematic, post it.

I like using a 1/4" phone plug as the safety key with the zip cord wire going to the pad. That way different lengths, or even thicknesses, of wires can be easily exchanged.

http://v-serv.com/usr/pubs/air7.htm

Jerry

[Feyd]

I use a couple oif threaded nuts, 2" long, to keep the rocket off the deflector. Also, since I use clips to hold the launch rod on, the blast deflector is angled so the rocket is never sitting flat on the plate.

My blast deflectors are metal electrical switch box covers with a hole drilled in the middle.

[Jerry Irvine]

As a general rule you want a curved blast deflector so the effluent does not blast either back onto the rocket or in any direction in a concentrated way. Heat is one thing, but concentrated heat is the source of most safety issues.

Just Jerry

There is a FAQ for that.

[bguff]

Get a pad with 3 legs, since 3 legs will always be stable:
http://mikesrocket.com/index.php?main_page=product_info&cPath=3&products_id=3&zenid=t1pbueivshdg6uf6tr8b3sjfq7
http://members.buckeye-express.com/turbopig/tri.htm
http://store.heavenlyhobbies.com/01-003-0011.html

Bob

[Jerry Irvine]

Get a pad with 3 legs, since 3 legs will always be stable
I see your point. A 4 leg or similar style pad can be aimed by a single, simple 16 oz beer can (or in a pinch a rock).

Oh, and have a far lower CG, and far wider rod and rail compatibility.

Jerry

http://v-serv.com/usr/start.gif

[bobdros]

I really liked Feyd's link to his launch pad build. That looks like the way to go! (That and an Aerotech controller.)

[Blushingmule]

[QUOTE=Feyd]

Also, I bought 4' launch rods from an on-line metals company and they are working out well. They came shipped in a sturdy tube and all were straight. Inexpensive rods but shipping was a little much (at least to me).

Launch Rod Steel (http://www.speedymetals.com/c-8227-cold-finished.aspx)

Which grade of steel/metal did you buy?

How bad was the shipping?

Thanks,

Bob
p.s. Nice fleet/build pile!

[blackshire]

If using a flat deflector, simply make sure the aft end of the rocket is a few inches above the flat deflector so you don't get Bernoulli Lock.

Do this by propping it up with a few spent motor casings or use tape on the launch rod.

http://rocketry.wordpress.com/2006/10/17/the-krushnic-effect-and-the-bernoulli-lock/Yes. Also, a homemade downward-angled (Centuri-type, see: http://www.ninfinger.org/rockets/nostalgia/82cen26.html ) jet deflector will direct the exhaust plume or plumes away from the base of the rocket while requiring less "wasted rod" because the rocket doesn't have to be suspended as high above an angled jet deflector.

[Feyd]

Here is what I ordered from Speedy Metals and what it cost:

Product Quantity Length Sub Total:
1/8" {A} Rd Cold Finished 1018-48"
SKU: 18r.125
Cutting Tolerance: Plus or Minus 3/4"
6 48 $3.12

3/16" {A} Rd Cold Finished 1018-48"
SKU: 18r.188
Cutting Tolerance: Plus or Minus 3/4"
2 48 $1.20

1/4" {A} Rd Cold Finished 1018-48"
SKU: 18r.25
Cutting Tolerance: Plus or Minus 3/4"
2 48 $2.14

Subtotal: $6.46
Shipping (UPS Ground): $11.53
Tax: $0.92
Total: $18.91

[Blushingmule]

Feyd,

Many thanks.

Bob