Fire prevention blast deflector

[tooth]

When I built my launch pad I bought a cake pan from the thrift shop for my blast deflector. After using it a couple times I realized if I flipped it around so the exhaust was going into the pan it would actually turn the sparks up and away from the grass. Photos from a couple of the launches I did this morning reminded me how effective this is so I thought I would share with you in case you also launch on grassy fields.

 

[rharshberger]

Same concept only much larger, blast deflector is 2' square with 45 degree raised edges, it sit 3" above the sod, and the sod has only soot damage usually.

 

[Hobie1dog]

excellent way of doing it. 95% of all blast deflectors merely angle the flame directly down onto the ground at a 45 degree angle.... doesn't really do anything does it?

 

[rharshberger]

excellent way of doing it. 95% of all blast deflectors merely angle the flame directly down onto the ground at a 45 degree angle.... doesn't really do anything does it?

Depends on how high above ground it is, most of our blast deflectors which are angled about 15 degrees and sit 2' above the ground leave the sod we fly on pretty much untouched even with big sparkies.

 

[Handeman]

To be honest, the blast deflectors on our clubs 1010 and 1515 pads are really there to protect the pads, not the ground around it.

 

[rharshberger]

To be honest, the blast deflectors on our clubs 1010 and 1515 pads are really there to protect the pads, not the ground around it.

Do you fly on a Sod farm? We have to protect the farmers product as best we can, a little burned sod he has no issue with but a N dark matter can burn away a bunch of sod quick.

 

[teepot]

What's grass. Hard to burn dirt. My blast deflector is an AR 500 rifle gong.

 

[K'Tesh]

Don't have a photo of the actual setup... But here's my idea...



You'd use a large can of tomato juice, cut lengthwise and unrolled... A hole punched in the middle for the launch rod.

 

[lakeroadster]

Well since we're talking fire prevention... my blast deflector is a 5 gallon bucket of water.

Black Powder Single 24mm D12-3

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Composite Motor single 29mm F52-5 motor

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Launch Horse Configuration

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[FredA]

Just a note regarding non-flat or angled blast plates.
While the rocket is on the pad...while chuffing or waiting for full-pressure to build, the thrust impinges on the close-by blast plate with the full force that the motor is generating.

Depending on how you mount the plate, it could be [will be] torqueing your launch rod/rail.
I've seen [photographed] large motors putting serious bends (like 5 degrees tilt) in RAILS when they had a rail mounted 45-degree blast plate mounted about a foot above where the rail was held at the base.

Something to consider when designing your GSE.

 

[jrap330]

Don't have a photo of the actual setup... But here's my idea...

View attachment 568311

You'd use a large can of tomato juice, cut lengthwise and unrolled... A hole punched in the middle for the launch rod.

Bad idea...6 surfaces where you have to worry about cutting yourself wide open. If you put tape on it but sooner or later the tape will come off after awhile. Sorry it is a no-go

 

[K'Tesh]

Bad idea...6 surfaces where you have to worry about cutting yourself wide open. If you put tape on it but sooner or later the tape will come off after awhile. Sorry it is a no-go

It's not rocket science... It's called folding the edges over (twice)... and then there's no chance of cutting yourself (outside of initial production).

 

[jrap330]

OK, fine K'Tesh

 

[rharshberger]

It's not rocket science... It's called folding the edges over (twice)... and then there's no chance of cutting yourself (outside of initial production).

Its a neat idea, but I have seen electrical coverplates (metal ones not plastic) burned through by BP motors, and a tin can is about 1/3 or so the thickness of those coverplates. All of our HPR blast deflectors are 1/4" steel and we cover them with a metal cut-off saw (14") abrasive disc to protect them. I have yet to replace one of those blast deflectors due to burn through, I did have to replace one from last season that had a CATO on it and it bent the 8" diameter by 1/4" thick blast deflector about 15 degrees or so along the line it was welded to the pad.

 

[lakeroadster]

Its a neat idea, but I have seen electrical coverplates (metal ones not plastic) burned through by BP motors, and a tin can is about 1/3 or so the thickness of those coverplates. All of our HPR blast deflectors are 1/4" steel and we cover them with a metal cut-off saw (14") abrasive disc to protect them. I have yet to replace one of those blast deflectors due to burn through, I did have to replace one from last season that had a CATO on it and it bent the 8" diameter by 1/4" thick blast deflector about 15 degrees or so along the line it was welded to the pad.

Indeed: Impingement Happens!

NASA floods the pad with water... my tax dollars at work... guud nuff

 

[K'Tesh]

Its a neat idea, but I have seen electrical coverplates (metal ones not plastic) burned through by BP motors, and a tin can is about 1/3 or so the thickness of those coverplates. All of our HPR blast deflectors are 1/4" steel and we cover them with a metal cut-off saw (14") abrasive disc to protect them. I have yet to replace one of those blast deflectors due to burn through, I did have to replace one from last season that had a CATO on it and it bent the 8" diameter by 1/4" thick blast deflector about 15 degrees or so along the line it was welded to the pad.

Were the coverplates flat to the direction of the jet of flame?

 

[rharshberger]

Were the coverplates flat to the direction of the jet of flame?

I have seen it both ways, heat transfer is heat transfer, slightly less for angled, full for flat. We replace several blast deflectors every year, they will eventually burn through.

 

[Imaknow]

Don't have a photo of the actual setup... But here's my idea...

View attachment 568311

You'd use a large can of tomato juice, cut lengthwise and unrolled... A hole punched in the middle for the launch rod.

Make it from a coffee can, mount that to a 1x12 about 18 inches long and you have my first launch pad circa1968.

 

[prfesser]

Make it from a coffee can, mount that to a 1x12 about 18 inches long and you have my first launch pad circa1968.

Yep. It's in the old Estes Technical Report 6 on clustering. The edges of the coffee can are tacked down to the board to minimize lacerations.

 

[David Schwantz]

We also fly off a sod farm. On the 1010 rails we use 3/16th plate that is3' off the ground. Most flyers will use a standoff above that. On the 1515 rail we have a 3' x 3' 1/4" plate that lies on a 30' x 20' welding blanket. Have never had it burn through but a cato did put a really big dent in it.

 

[waltr]

Yep. It's in the old Estes Technical Report 6 on clustering. The edges of the coffee can are tacked down to the board to minimize lacerations.

That is the launch pad my brother & I build back in the '60s.
Worked great.

 

[OzHybrid]

please all read the guidelines on cleared areas required for a launch before posting pictures launching in an area that clearly has 12" high dried grass underneath. Safe launching practices are required for insurance. If we lose insurance, we lose the ability lo legally launch at many sites.

 

[Steve Shannon]

NASA floods the pad with water... my tax dollars at work... guud nuff

That’s for sound control, isn’t it?

 

[lakeroadster]

That’s for sound control, isn’t it?

Water, Water, Everywhere​

Thousands of gallons of water flood the launch area at the crucial moments surrounding ignition, serving two purposes. Water keeps flames from spreading and prevents damage caused by sound waves.​

 

[ep29030]

Go get a disc blade at a tractor store (Tractor Supply, Rural King, Farm and Fleet). Heavy steel with a square hole in the center and a nice curve to the disc. Even better, find a farmer who has some old ones. Tractor Supply:

 

[Grog6]

I built a pad back in the 80's, where I used some left over pipe pieces to build a pad; the blast deflector was a 2" diameter section of iron pipe, with90's on each end. It deflected the blast straight up, and we never had any fire issues. We discovered, after it sat in the launch site overnight, that filling the pipe with water was spectacular! Water, steam, and hot gas, 20 feet in the air. It was only a d or E motor.

 

[Blast it Tom!]

I built a pad back in the 80's, where I used some left over pipe pieces to build a pad; the blast deflector was a 2" diameter section of iron pipe, with90's on each end. It deflected the blast straight up, and we never had any fire issues. We discovered, after it sat in the launch site overnight, that filling the pipe with water was spectacular! Water, steam, and hot gas, 20 feet in the air. It was only a d or E motor.

I've daydreamed about a water deluge for my pad... maybe some day...

 

[BMAT]

I built a pad back in the 80's, where I used some left over pipe pieces to build a pad; the blast deflector was a 2" diameter section of iron pipe, with90's on each end. It deflected the blast straight up, and we never had any fire issues. We discovered, after it sat in the launch site overnight, that filling the pipe with water was spectacular! Water, steam, and hot gas, 20 feet in the air. It was only a d or E motor.

See my avatar..........

 

[Ogre3713]

I've always thought that a fiberglass welding blanket would make for some great ground cover under the pad. Harbor Freight has an 8'x8' for $50. Not bad investment if your really worried about scorching the earth.

 

[Steve Shannon]

I've always thought that a fiberglass welding blanket would make for some great ground cover under the pad. Harbor Freight has an 8'x8' for $50. Not bad investment if your really worried about scorching the earth.

8x8 is great for small rockets but we’ve had fires start 30 feet away from the pad for L3 size rockets.
We weed-eat the grass and rake it away and we check the pad area immediately after the launch.