Author Topic: Fuse delay for bombs (Read 2644 times)

AKDejaVu · « **Reply #60 on:** August 08, 2002, 10:38:38 PM »

OK.. time to arm is no more/less accurate than distance to arm. Its based on veign rotation. Number of revs equals arming. The revs/sec varry on speed so the time can quite simply vary. I've not seen digital or quarts mechanisms in veign operated fuses that do any actual "timing". Distance is just as accurate of a measurement.. so no need to get technical on time vs distance here. Neither is completely accurate, but both are still relatively accurate (especially with these planes).

Once again, as ammo touches on, the fuzing is a minor point. What the bomb does before the fuze arms is a much more significant point.

What would a bomb do if it hit the side of a hangar with a delayed fuze?

What would a bomb do if it was dropped into the ground with a delayed fuze?

These questions are still going un-answered by people making the request.

AKDejaVu

AKDejaVu · « **Reply #61 on:** August 08, 2002, 10:39:28 PM »

Zizu · « **Reply #62 on:** August 08, 2002, 10:54:27 PM »

quote:
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Originally posted by AKDejaUu
BTW.. any idea how long it takes for a bomb (or anything) to drop 500 feet?
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quote:
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I don't think anyone answered this yet...

3.9 seconds neglecting drag.
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Nope, something's wrong with the math here. Distance covered with a constant acceleration follows the formula

s = 0.5a t^2

where s is distance, a is acceleration, and t is time. Rerranging this formula to solve for time yields

t = sqrt(2s / a)

Acceleration due to gravity is approx. 32 ft/sec squared, so

t = sqrt((2 * 500 ft) / (32 ft/sec squared)) = 5.6 seconds

See? Undergraduate physics is useful after all.

Also note that a non-spherical object dropped at significant forward speed on an irregular surface can indeed bounce higher than its originally dropped height depending on the forward speed, the distance dropped, how it hits, the coefficient of restitution, etc. Think of a football thrown hard at a shallow angle and you will know what I mean.

Zizu

gatso · « **Reply #63 on:** August 09, 2002, 05:12:57 AM »

lol, ty Zizu. That'll teach me to try and do maths with a bottle o beer in my hands.

Forgot the 0.5.

Thanks for the link ammo, I'll have a read now.

Gatso

Revvin · « **Reply #64 on:** August 09, 2002, 07:26:29 AM »

Quote

What would a bomb do if it hit the side of a hangar with a delayed fuze?

What would a bomb do if it was dropped into the ground with a delayed fuze?

These questions are still going un-answered by people making the request

And that's for Hitech to decide on what limitations the game engine (if any) will put on these questions.

FACT: fuse delays were used in WW2 against buildings and other hardened targets, vehicles and shipping. The request was simple enough to ask if it could be done and only HTC can answer that.

AKDejaVu · « **Reply #65 on:** August 09, 2002, 07:45:36 AM »

Quote

Originally posted by Revvin
FACT: fuse delays were used in WW2 against buildings and other hardened targets, vehicles and shipping. The request was simple enough to ask if it could be done and only HTC can answer that.

Fact: we have no hardened targets.

Penetrating a target is a non-issue in AH.

Its the wonderfull thing about reality... the physics is already in place.

AKDejaVu

Revvin · « **Reply #66 on:** August 09, 2002, 07:51:08 AM »

We have shore batteries, vehicles and shipping as well as other targets to destroy that would be aided by a fuse delay.

gatso · « **Reply #67 on:** August 09, 2002, 10:07:41 AM »

This is interesting:

From here

REMARKS: Stachebomben, or "Stabo" for short, are used in low altitude attacks to ensure the bomb does not ricochet.

gatso · « **Reply #68 on:** August 09, 2002, 10:42:29 AM »

This is a very interesting subject. I've had to dig quite a lot to get any info out of the web and I'll probably be getting a visit from someone working for MI5 wanting to talk to me about the amount of searches I've done for 'bomb fuses' and similar

Conclusions.

Lots of places quote the 11 second fuse delay for allied aircraft as being the most common.

Bomb ricochet was a known problem for low altitude drops. (see my above post)

Mosquitos in particular did a lot of high profile low alt raids (Amiens and the Gestapo HQ in the Hague probably being two notable ones).

US forces did use parachute retardation although not much.

I guess there's nothing much we can do now, the 'bomb skipping' thing is nothing any of us here can fix so I'm just going to sit back now and see if anything comes of it.

a few links for you to finish:

German bombs (pics of layouts and fuzing mechanisms)

British Bombs, useful background

Bombs rockets and other ord

The site ammo linked is Excellent too. TY for that.

Lets try and keep it constructive now and not just nit pick at each others post.

Gatso

ccvi · « **Reply #69 on:** August 09, 2002, 12:36:05 PM »

Quote

Originally posted by Zizu
t = sqrt((2 * 500 ft) / (32 ft/sec squared)) = 5.6 seconds

See? Undergraduate physics is useful after all.

Zizu, you failed to give the answer to the right question. A bomb doesn't have zero velocity at drop. It's at the same speed as the ac that drops it.

Doing math in those units is forbidden by international standards anyway.

Revvin · « **Reply #70 on:** August 09, 2002, 12:56:08 PM »

Quote

Lots of places quote the 11 second fuse delay for allied aircraft as being the most common.

Thanks for the links, 11 sec delay was a figure that came up again and again in documentaries I've watched and books I've read. Fused bombloads have just as much a place in AH as all the various types of cannon rounds modelled.

gatso · « **Reply #71 on:** August 09, 2002, 04:10:37 PM »

Quote

Zizu, you failed to give the answer to the right question. A bomb doesn't have zero velocity at drop. It's at the same speed as the ac that drops it

It has zero vertical velocity if you drop it level and thats what we were talking about, dropping low and level. Yes if your dive bombing you need to add the initial vertical component of the velocity.

OK I refuse to give up on this

I thought i would but it's gonna bug me now.

Some interesting figures, estimates really, no drag included because we don't know what value drag the bombs have in AH. As the times are relatively small there should be minimal error involved.

Minimum alt to drop bombs level and have them explode at the moment: 75 feet
Time for bomb to hit the ground: 2.2s
Angle of impact at 75 feet assuming 300mph horizontal velocity: 9 degrees.

9 degs is not an awful lot, it does seem sensible that such a flat trajectory would mean the bomb not stopping dead when it hits the ground, it flatter the faster the drop speed of course.

Interestingly the angle of impact I have from 500feet and 300mph is only 22 degrees, the higher you go the more 'out' the figure will end up I know, but it's interesting all the same. I thought it'd be a lot higher than that from gut feeling.

I guess one solution would be for bombs with a delay to 'bite' into the ground if they hit the deck above a certain angle and horizontal/vertical velocity, if they don't reach this angle they bounce until they run out of energy or hit something. This seem sensible? Changes in terrain angle (hills in the way) wouldn't matter then if you applied the same criteria to every bounce.

One thing i've not thought up any ways to get round is when a large heavy bomb moving at a huge rate of knots hits something as small as a field ack or similar, Is it reasonable to have the bomb 'stick' to it even though in RL it would smash straight through and keep going? Any larger structure and the bomb sticks to the point it hit before blowing up when the 11 secs or whatever are up. Bombs that don't hit anything just go boom after X secs whatever they are doing.

Thoughts?

Gatso

(P.S. A lot less drunk while doing the calcs this time

so they might even be right

)

gatso · « **Reply #72 on:** August 09, 2002, 04:11:11 PM »

double post

-ammo- · « **Reply #73 on:** August 09, 2002, 06:28:53 PM »

Quote

Originally posted by Revvin

Thanks for the links, 11 sec delay was a figure that came up again and again in documentaries I've watched and books I've read.

We are talking about a 11 second time to arm delay, right? An 11 second detonation delay after an impact would not work for a general purpose frag or incendiary bomb.

-ammo- · « **Reply #74 on:** August 09, 2002, 06:42:05 PM »

To piggy back on my last post, I dont know what value a time to arm delay woul bring to AH, in fact its kind of implemented already but for a different reason. Time to arm delay is purely a safety measure, to allow seperation of the bomb from the delivery AC before arming of the fuze/bomb. The idea behind non airborn AC not being able to explode bombs is basically the same thing, but was implemented to stop the dweebishness. Functional delay in a bomb could have some use against very hard targets and hangers, only if the correct bombs were modeled. I dont even know if hardened bombs were in existence in WW2, but I am betting they were:) Mechanical fuze functional delays range anywhere from a tenth of a second up through one full second nowadays, and the theory would hold true in WW2 as well.