Quantcast

Got Deflector!

The Rocketry Forum

Help Support The Rocketry Forum:

Johnnie

Well-Known Member
Joined
Dec 31, 2002
Messages
4,289
Reaction score
0
So I'm driving home, with my head in the rocket clouds, when out of the corner of my eye I spy it. Someone else's garbage tossed to the side of the road...Oh! Heaven!

Two disgarded satelite dishes...these make great blast deflectors. One of these is destined to become a blast plate for my HPR PVC Pad.

One main reason that I do not bring my HPR PVC Pad to a launch, is that with it's low center of gravity, the rocket motor balsts right from the ground...I don't think that sod farms would appreciate me burning holes in their livelyhood.
 

Johnnie

Well-Known Member
Joined
Dec 31, 2002
Messages
4,289
Reaction score
0
This dish has an interesting mounting point that allows for some brain teasing possiblities
 

Johnnie

Well-Known Member
Joined
Dec 31, 2002
Messages
4,289
Reaction score
0
The other dish has a swivel mount for adjustable blast deflection :D

Got deflection? I do
 

astrowolf67

Well-Known Member
Joined
Jan 19, 2009
Messages
1,503
Reaction score
6
Hey, I'm interested to see how you use one of these. I've got one laying out behind our shed, and have thought of using it many times!
 

brianc

Well-Known Member
Joined
Jan 18, 2009
Messages
3,220
Reaction score
1
Originally posted by Johnnierkt

Two disgarded satelite dishes...these make great blast deflectors.
HMMMM.... I guess I'm gonna have to drive around a bit this week.

I'm sure the hurricanes knocked a few of these down. ;)
 

JStarStar

Well-Known Member
Joined
Jun 6, 2009
Messages
2,528
Reaction score
56
If you do google searches on ''satellite dish," you come up with quite a few, fairly cheap. How heat-resistant those are, who knows.

Another possibility would be used auto hubcaps from a junkyard, which can probably be gotten very cheap.

Myself, if i were building a whole pad assembly totally from scratch, I'd probably use a corner section of 4" or 6" stove pipe, which usually is very heat resistant. Probably just use a hose clamp to attach it to the launch rod.

Something like this:



My experience is that when you launch rockets off flat blast plates, you get a lot of 'backsmoke' on the tail end of the rocket, because the exhaust cloud kicks back on the rocket before it gets off the pad.

If you use a directional deflector like this, especially a tube section, it sets up suction and airflow through the pipe, and the exhaust smoke basically surges out the pipe and off to the side.
 

Johnnie

Well-Known Member
Joined
Dec 31, 2002
Messages
4,289
Reaction score
0
I have posted the "elbow" idea for blast deflection a few times, as it has a nice cool factor to it.

With the bowl shape of the dish, at least with larger motors, the flame balls at the begining of the flight.

Anyways, I will manufacture a way to mount this thing, and get some pics...it should protect the sod quite nicely.

Here is a picture of my HPR PVC Pad after 1 day of launching in Orangeburg, SC last year. Luckily this sod farm has a road down the middle of it, cause we were cuttin some holes. Picture was taken by none other than the forums very own Rocketmaniac.
 

Ryan S.

Well-Known Member
Joined
Mar 24, 2003
Messages
3,550
Reaction score
0
or you could just throw a couple of steel or aluminum plates on the ground.
 

Johnnie

Well-Known Member
Joined
Dec 31, 2002
Messages
4,289
Reaction score
0
or you could just throw a couple of steel or aluminum plates on the ground.
quick on the trigger there ryan...
you beat me to it...There are four mounting holes thru the STEEL dish, that I will put bolts thru to make legs out of. The finished blast plate will look like half a flying saucer landed under my pad... I will just toss it up under the rail, and it will be slightly elevated off of the Sod, so as to not mash it down with hot exhaust blasts. The bolts can also act as stakes, so the deflector does not get blown away on every flight...did I mention it was free?!

:rolleyes:
 

Rick James

Well-Known Member
Joined
Aug 31, 2004
Messages
103
Reaction score
0
As was alluded to above, I would angle the dish so the blast is deflected to the side... this help will protect the bottom of the rocket...

Originally posted by Johnnierkt
I have posted the "elbow" idea for blast deflection a few times, as it has a nice cool factor to it.
Speaking of "cool" factor... I built a deflector for my LPR stuff using a coffee can - deflecting to the side (see attached pic). One morning I was launching on a grassy field... after a few launches I noticed a really cool little miniature ground fog around the pad. I realized the heat from the launches had vaporized the dew in the grass. It was really, really cool!
 

Johnnie

Well-Known Member
Joined
Dec 31, 2002
Messages
4,289
Reaction score
0
Well, the idea of putting bolts in for legs on my deflector design was a bust. The CG of my pad is so low, that short of just throwing the dish on the ground, it just fits. It is slightly angled to blast away from the base of the rockets, and will curve slightly to keep the blast from singing the sod.
 

Johnnie

Well-Known Member
Joined
Dec 31, 2002
Messages
4,289
Reaction score
0
The other dish I have will be a spare, or might get used on a mega PVC Pad I have been trying to urge myself to build...

Here is a side shot. On satelite dishes, there is the arm that extends off of it that holds the receiver part. Well I merely broke one of the welds loose that was holding the arm in posistion, and now it is used as a steady rest for the dish.
 

JStarStar

Well-Known Member
Joined
Jun 6, 2009
Messages
2,528
Reaction score
56
Rick James, that's a cool-looking pad!!

Back in the olden days, we used to beg a coffee can off our moms, then cut it open with tin shears, then use pliers to bend the sharp edge over itself so it's not sticking out... then just drill a hole for the launch rod and bend the coffee can back to form a double-deflector.

Wasn't fancy, but it worked. I think this is actually illustrated in the HBOMR. After a few dozen launches, the coffee cans weren't holding up too well, but mom and dad used to drink a lot of coffee in those days, so you just get a new one....

You could just use the coffee can lid as a circular deflector, but those basically had a razor-sharp edge, and usually when you're fiddling around down there hooking up clips, etc, you'd snag your finger and get a pretty good cut. So using the coffee lids as deflectors kind of lost favor.
 
Top