Booby trap flour explosion

Donny Brook · 09-12-2023, 02:35 PM

I was thinking of using a flour explosion as the pay-off for a room trap in my campaign.

Does anyone know, or know where to find, information on how to calculate the force of a flour explosion?

Varyon · 09-12-2023, 02:45 PM

There's a long-ish thread on this very subject here which would likely be worth a look. Optimal air/flour mix results in something like REF 4 (and thermobaric, so ex3 - divide damage by distance in yards rather than twice or thrice this), which can make for a really big boom - but said optimal mixing is very difficult to manage.

RGTraynor · 09-12-2023, 02:49 PM

Quote:

Originally Posted by Donny Brook

I was thinking of using a flour explosion as the pay-off for a room trap in my campaign.

Does anyone know, or know where to find, information on how to calculate the force of a flour explosion?

I'd start with the Wikipedia article: https://en.wikipedia.org/wiki/Dust_explosion. Especially illuminating is the series of photos of inducing a flour explosion: that doesn't look like a cloud of more than a 5 lb sack, and that resulting fireball doesn't look like ANYthing I'd want going off in the middle of my party.

I agree with Varyon that artificially creating such a cloud isn't easy, but if the tech level's too low for the requisite motorized grinder and expeller, it strikes me that a fantasy Big Bad may well have researched a Substance To Cloud spell.

Anthony · 09-12-2023, 03:12 PM

I would note than an explosive mixture is much easier to achieve with gases or extremely volatile liquids, and the resulting explosion is likely to be somewhat more powerful as well. It's also subtler -- pure methane doesn't have a distinctive scent so there won't be much warning until a spark turns the entire thing into a fireball.

Anaraxes · 09-12-2023, 03:15 PM

Finally, another application for Gust of Wind.

Refplace · 09-12-2023, 03:45 PM

Search for FAE or Fuel Air Explosions. ASs others have said its tricky to get the mix just right. the main advantage is the typical substances are not controlled or at least less so. Buying in bulk can get you on a list.

Donny Brook · 09-12-2023, 06:51 PM

Thanks for the replies. I got all I need for this now. My players are really going to hate this. *evil grin*

Fred Brackin · 09-12-2023, 07:40 PM

You might want to also look for Mythbusters. They did many of these sorts of fuel/air explosions and the only way they ever got it to work was to have an open flame in the room and then add the fuel until they reached the minimum viable fuel/air ratio. This is usually not the _optimum_ ratio. It's just the first point where things go "boom".

You'll also need a lot of control over the mixing, especially with a heavier than air solid. Dump too much flour into the room and it'll smother the starter flame rather than go "boom".

A flammable gas or aerosolized liquid would almost certainly be easier to arrange. If the PCs aren't using a magical light source they'll be bringing the ignition source in with them too. :)

Willy · 09-12-2023, 08:26 PM

Only in experimental setups you will get a more or less optimal reaction. But getting it right in a normal environment is next to impossible. I would calculate with 1/3 to 1/2 of the optimal damage at best.

Your trap may be work in the following way, a switch, wire, plate whatsoever does with a little time between the actions first lets powder slowly fall or better blow into the room, if you can use fans. Otherwise a hole in the ceiling opens and the stuff trickles down. Little doses from several spots work best. Second a spark may it be a candle a electrical spark, torch etc lightens it up.

Since you have than 2-3 seconds between the steps canny PCs know what is happening and try to escape.

By the way flour is nice but other free available substances have also high energy and weight less resulting in a better result. Fine powdered sugar or a certain brand of sauce thickener was popular with some ***. That is unless one guy needed new eyebrows.

Pursuivant · 09-12-2023, 08:41 PM

The main problems are getting the flour particles small enough to easily combust and keeping them suspended long enough. Some sort of gentle updraft helps keep particles suspended. Ideal REF is 4, actual REF is likely to be a fraction of that, possibly lower than 1. I'd start with 0.5 + (1d x 0.1) REF.

A Food/Air College spell to make an optimized grain dust explosion would be a vicious Area Effect spell, guaranteed to make the Food college a lot more popular among battle mages.

09-12-2023, 02:35 PM	#1
Donny Brook Join Date: Aug 2014 Location: Snoopy's basement	Booby trap flour explosion I was thinking of using a flour explosion as the pay-off for a room trap in my campaign. Does anyone know, or know where to find, information on how to calculate the force of a flour explosion?

09-12-2023, 02:45 PM	#2
Varyon Join Date: Jun 2013	Re: Booby trap flour explosion There's a long-ish thread on this very subject here which would likely be worth a look. Optimal air/flour mix results in something like REF 4 (and thermobaric, so ex3 - divide damage by distance in yards rather than twice or thrice this), which can make for a really big boom - but said optimal mixing is very difficult to manage. __________________ GURPS Overhaul Last edited by Varyon; 09-12-2023 at 02:48 PM.

09-12-2023, 03:12 PM	#4
Anthony Join Date: Feb 2005 Location: Berkeley, CA	Re: Booby trap flour explosion I would note than an explosive mixture is much easier to achieve with gases or extremely volatile liquids, and the resulting explosion is likely to be somewhat more powerful as well. It's also subtler -- pure methane doesn't have a distinctive scent so there won't be much warning until a spark turns the entire thing into a fireball. __________________ My GURPS site and Blog.

09-12-2023, 03:15 PM	#5
Anaraxes Join Date: Sep 2007	Re: Booby trap flour explosion Finally, another application for Gust of Wind.

09-12-2023, 03:45 PM	#6
Refplace Join Date: Nov 2008 Location: Yukon, OK	Re: Booby trap flour explosion Search for FAE or Fuel Air Explosions. ASs others have said its tricky to get the mix just right. the main advantage is the typical substances are not controlled or at least less so. Buying in bulk can get you on a list. __________________ My GURPS publications GURPS Powers: Totem and Nature Spirits; GURPS Template Toolkit 4: Spirits; Pyramid articles. Buying them lets us know you want more! My GURPS fan contribution and blog: REFPLace GURPS Landing Page My List of GURPS You Tube videos (plus a few other useful items) My GURPS Wiki entries

09-12-2023, 06:51 PM	#7
Donny Brook Join Date: Aug 2014 Location: Snoopy's basement	Re: Booby trap flour explosion Thanks for the replies. I got all I need for this now. My players are really going to hate this. evil grin

09-12-2023, 07:40 PM	#8
Fred Brackin Join Date: Aug 2007	Re: Booby trap flour explosion You might want to also look for Mythbusters. They did many of these sorts of fuel/air explosions and the only way they ever got it to work was to have an open flame in the room and then add the fuel until they reached the minimum viable fuel/air ratio. This is usually not the _optimum_ ratio. It's just the first point where things go "boom". You'll also need a lot of control over the mixing, especially with a heavier than air solid. Dump too much flour into the room and it'll smother the starter flame rather than go "boom". A flammable gas or aerosolized liquid would almost certainly be easier to arrange. If the PCs aren't using a magical light source they'll be bringing the ignition source in with them too. :) __________________ Fred Brackin

09-12-2023, 08:26 PM	#9
Willy Join Date: Dec 2020	Re: Booby trap flour explosion Only in experimental setups you will get a more or less optimal reaction. But getting it right in a normal environment is next to impossible. I would calculate with 1/3 to 1/2 of the optimal damage at best. Your trap may be work in the following way, a switch, wire, plate whatsoever does with a little time between the actions first lets powder slowly fall or better blow into the room, if you can use fans. Otherwise a hole in the ceiling opens and the stuff trickles down. Little doses from several spots work best. Second a spark may it be a candle a electrical spark, torch etc lightens it up. Since you have than 2-3 seconds between the steps canny PCs know what is happening and try to escape. By the way flour is nice but other free available substances have also high energy and weight less resulting in a better result. Fine powdered sugar or a certain brand of sauce thickener was popular with some ***. That is unless one guy needed new eyebrows.

09-12-2023, 08:41 PM	#10
Pursuivant Join Date: Apr 2005	Re: Booby trap flour explosion The main problems are getting the flour particles small enough to easily combust and keeping them suspended long enough. Some sort of gentle updraft helps keep particles suspended. Ideal REF is 4, actual REF is likely to be a fraction of that, possibly lower than 1. I'd start with 0.5 + (1d x 0.1) REF. A Food/Air College spell to make an optimized grain dust explosion would be a vicious Area Effect spell, guaranteed to make the Food college a lot more popular among battle mages.