Blast Deflector Gauge?

[gary7]

Working on my own launch pad and need advice on the thickness of a blast deflector. Is 22 gauge steel enough for A-I motors or do I need something heavier for the G, H and I motors? I am quite happy with my efforts so far and will post a picture with details when it is done. Thanks.

 

[Handeman]

If you're going to I motors, I would go with something in the 16 to 14 ga range. The 22 ga may hold up, but the thicker stuff will last longer and should hold up if something hangs on the rail. I watched a K hybrid hang on the rail without the steel blast deflector. The third mach diamond ended up melting a 2.5" hole through the top and bottom of a 3" x 4" extruded aluminum bar, digging a 8" hole in the dirt underneath. Hang fires happen.

 

[powderburner]

Or you can go get a cheap ceramic floor tile at the hardware store

Or pour a batch of cement into a pie tin or the bottom of a litre soda bottle(with a straw through the middle to leave room for the launch rod)

 

[Handeman]

Or you can go get a cheap ceramic floor tile at the hardware store

Or pour a batch of cement into a pie tin or the bottom of a litre soda bottle(with a straw through the middle to leave room for the launch rod)

The ceramic tile is what we used for the clubs LPR rack. I glued a bunch of 4 x 4 tiles to some 1/2" plywood and used a 1/4" ceramic drill to put a hole through the middle. They work great and the wood backing keeps them from breaking.

 

[Micromeister]

On all the Narhams systems we try to stay with 16ga Stainless steel. but event they take a beating under the Higher impulse AP motors. They do clean up nicely tho with white vinegar and a very little elbow grease.

 

[Handeman]

On all the Narhams systems we try to stay with 16ga Stainless steel. but event they take a beating under the Higher impulse AP motors. They do clean up nicely tho with white vinegar and a very little elbow grease.

Stainless is great for tough environments. Do you happen to have a pic of a used and abused plate and what size motors abused it, to give us an idea of how the 16ga SS stands up to a specific level of AP motors?

 

[Bone Daddy]

The DARS club pad uses metal cut off wheels. Even have a ready to use hole. These things will last forever and are easy to replace if lost. Pic for an example only.

Simple but elegant. My hat goes off to whomever thought of this.

 

[JAL3]

The ceramic tile is what we used for the clubs LPR rack. I glued a bunch of 4 x 4 tiles to some 1/2" plywood and used a 1/4" ceramic drill to put a hole through the middle. They work great and the wood backing keeps them from breaking.

I liked the ceramic tiles but stopped using them because I kept breaking them.

Thanks for the idea on the plywood backing!:bang:

 

[Rex R]

I've seen pictures of folks using terracotta flowerpots...just curious whats wrong with using plant saucers(terracotta)? aside from having to drill a hole .
rex

 

[Micromeister]

Stainless is great for tough environments. Do you happen to have a pic of a used and abused plate and what size motors abused it, to give us an idea of how the 16ga SS stands up to a specific level of AP motors?

Well Not exactly: I have a couple pics of the 22ga 304 Stainless deflector I use on my Solar Launcher that has taken everything from 1/8A to H motors and is still kicking very well after all these years. The 22ga deflector is more the 15 year old. At the point the photos were taken the deflector and launcher head had be cleaned with Fantastic spary cleaner but not yet with White Vinegar to remove the black AP build-ups.

We've been using the same 16ga 304 Stainless deflectors for about 20 years in several systems. Our newest (2003) rack is the only one that I've had to replaced one plate involved with a G80 Cato that folded the plate so that I couldn't straighten it out well enough to lay flat in it's storage holder. The last pic below shows the well used but cleaned 6- 4" x 4" x 16ga deflectors stacked in their bottom of the rack storage space.

 

[MarkII]

One thing to keep in mind is that club launch pad deflectors probably need to be tougher than one that you would use for your own personal pad because they get much more use. (Many more rockets are fired from them.) So a deflector for your own pad may not need to be quite so heavy-duty. For my own pad, I use a backing plate from an electrical junction box. I purchased it at a local hardware store for something like $0.89. I bought the biggest one that I could find, which was the backing plate for a 4-outlet box. I use a double-threaded nipple for the support for the rod (which gets clamped inside of it). I removed the center knock out from the plate so that I can fit it onto the top of the nipple and hold it in place with a couple of conduit nuts. When I break down the pad, I just unscrew the nipple at its lower end from its attachment point on my Rube Goldberg-like quad-footed pad, leaving the blast deflector and launch rod attached. (Some day I ought to write up a description of that pad. It will be good for a laugh or two.) After 4 years of use, the galvanized steel plate shows no pitting or corrosion. I use a little bit of white vinegar and baking soda to clean off the residue at the end of the season each year. That is the only maintenance that I have ever given it.

MK

 

[gary7]

So I decided to have a 16 gage sheet made at a metal shop. It came out very nice but I made a big mistake. Steel, not stainless. Now, after one day out and two launches, the thing is rusted. What can I do to it to get the rust off and keep it off that will also be flame proof?

 

[MarkII]

So I decided to have a 16 gage sheet made at a metal shop. It came out very nice but I made a big mistake. Steel, not stainless. Now, after one day out and two launches, the thing is rusted. What can I do to it to get the rust off and keep it off that will also be flame proof?

Steel wool or Scotch-Brite and elbow grease to remove the rust. Give it a very light coating of oil (or Vaseline) in between launches to keep it from rusting. Start planning to replace it with one of the other suggestions. But who knows; with diligent care, it could last awhile. If you don't want to get stainless (which can be expensive), try galvanized steel plate.

 

[terryg]

We have started using old frying pans for blast deflectors at our club launch.
They are always in plentiful supply and cost nothing since they were going to be thrown away.

 

[MarkII]

We have started using old frying pans for blast deflectors at our club launch.
They are always in plentiful supply and cost nothing since they were going to be thrown away.

Now there's a thought...Where do you get them?

 

[Handeman]

So I decided to have a 16 gage sheet made at a metal shop. It came out very nice but I made a big mistake. Steel, not stainless. Now, after one day out and two launches, the thing is rusted. What can I do to it to get the rust off and keep it off that will also be flame proof?

Other then aesthetics, the rust doesn't hurt anything. A quick spray of WD-40 after a launch will help keep the rust from getting worse.

The blast deflectors on our club's rail pads were painted with black high temp grill paint when they were new. They sit out in the field from Nov - April and after two years the rust isn't bad at all.

 

[cwilliams]

I liked the ceramic tiles but stopped using them because I kept breaking them.

Thanks for the idea on the plywood backing!:bang:

That's why I went with a 12"x12" granite tile Took forever to drill through even with a carbide tip, but it will definitely last a long time and looks good too!

 

[sodmeister]

Here`s a pic of the blast plate I made for my launcher.It`s made of 18 g. stainless steel with a cross break for strength.Been using it for two years now and is still as good as new ,but a little dirtier.I use vinegar and a scrub pad to clean it.

Paul

 

[Micromeister]

I strongly suggest folding a 1" UP bend on the lower outer edges of all down sloping jet deflectors to redirect the flaming sparks and burning propellant grain back up and way from the Grass or other combustables under you Launch pad.
Another way is to place a larger Flat plate defector under the sloped deflector.

I can't begin tell you how many small grass fires I've seen caused by angled deflectors like the one shown, unless they are used with a Nomex Pad Blanket under the launcher. I Know lots of launchers use this type deflector and hopefully others will pass this fire safety warning along.

It's quite amazing the amount of flame, sparks and buring debris coming out of our motors not seen during daylight launches. Perhaps a couple of these night launch shots will help illistrate what I'm talking about. Note that the rack flat deflector plates in these photos are 36" above the ground, my HD launcher deflector 40".

 

[Rex R]

I'm 'testing' a terracotta plant saucer(5") for C engines and below they are fine...D engines will errode them but, a simple fix, a layer of elmers glue seems to prevent the errosion. have not tried anything bigger than a D though.
rex

 

[bobkrech]

16 gauge stainless steel is 0.0625" (1/16") thick. 18 guage stainless steel is 0.050" (1/20") thick. A 16 gauge stainless steel bast protector will survive about 1000 low/mid-power launches.

For high power pads, we use a steel harrow disk. They are heavy, but will last a lifetime of launches.

Bob

 

[spacecadet]

So I decided to have a 16 gage sheet made at a metal shop. It came out very nice but I made a big mistake. Steel, not stainless. Now, after one day out and two launches, the thing is rusted. What can I do to it to get the rust off and keep it off that will also be flame proof?

What's wrong with rust? Leave it.

 

[tsai]

I use ceramic tiles. For small rockets/motors, a 4" tile is sufficient. 19 cents at Home Depot. 6" or 12" tiles should work for larger rockets. Just make sure you get a true ceramic tile. Non ceramic tiles won't have the same heat resistance and may shatter.

 

[GregGleason]

... Just make sure you get a true ceramic tile. Non ceramic tiles won't have the same heat resistance and may shatter.

Good point and ... welcome!

Greg

 

[sodmeister]

16 gauge stainless steel is 0.0625" (1/16") thick. 18 guage stainless steel is 0.050" (1/20") thick. A 16 gauge stainless steel bast protector will survive about 1000 low/mid-power launches.

For high power pads, we use a steel harrow disk. They are heavy, but will last a lifetime of launches.

Bob

Yessir ,18 gu. is plenty me thinks

Paul T (Local 511 ,sheet metal workers union)

 

[cwilliams]

Good point and ... welcome!

Greg

I used granite tile instead I've put 3 low powered rockets on it so far and there isn't even a mark on it. Any residue wipes right off.

 

[MarkII]

Isn't granite expensive, though?

 

[cwilliams]

$5 at Home Depot for a 12"x12"