Looking for potential solutions/pointers on a tricky problem, but one a hand can do easily. 1

[Mechbob1]

I have a problem I'm struggling to solve.

Think of hand-dropping a mortar round down a tube then moving away. I want to be able to do that, but remotely and without electronics/solenoids etc. An video example of what I'm trying to achieve is here:

https://www.youtube.com/watch?v=QTbuGpCBUQE

I've got a potential solution, but I'm stuck on how to 'release' the mechanism (ie, let go of the round and move away from the tube).

So, I've got a way to hold the 'round' in place, but unsure how to release and get it out of the way.

The current solution is below (from above vantage):

Here, in Position A, it is holding the object. Once released and it changes to Position B, the mechanism springs apart and falls to the ground. What I haven't yet solved is how to release/hold the mechanism together. We've toyed with the idea of a cable to remove whatever captures the two square ends, but I keep running into challenges.

Without going too far in a certain direction, I'm thinking of a cable pulling on a ball-pin which is holding the two parts together, as per below image.

Can you poke holes in current idea, and suggest improvements/better ideas? Thanks.

PS, apologies for shoddy drawings, just playing with designs at this stage.

 

[BrianE22]

I don't think it is any better but maybe try an extension spring instead of a compression spring - so spring tends to open the hinge. Use a clip to hold it closed then pull the clip off.

 

[IRstuff]

In order to come up with a "solution" you need to describe the functionality:
> what is the purpose of the spring?
> what is the purpose of the pull-pin?
> how far away is the operator?

A step-by-step description of how the mechanism is to be used should be the starting point

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

https://www.youtube.com/watch?v=BKorP55Aqvg

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[desertfox]

hi Mechbob1
How does the ball pin re-engage with the holes after realease?

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein

 

[Mechbob1]

Good idea, Brian. That would simplify the release. I presume you mean to use the extension spring at the bottom of the picture with a release pin through one end?

IRstuff:

> what is the purpose of the spring?

To ‘open’ the device quickly once the hold-shut mechanism is released.

> what is the purpose of the pull-pin?

The pull-pin is what is the go/release mechanism. Ie, drops the object down the tube. Safety is super-important.

> how far away is the operator?

About 15m.

Step-by-step: device is opened as per Position B, above. Object is placed in device, and shut and held in Position B. Device is placed over tube and people move approx 15 metres away to ‘release’ device. Upon release, device falls away from tube onto ground.
Rinse and repeat.

Desertfox, after release it’s manually reinserted. There’s a fair time gap between iterations

Hope this helps.

 

[desertfox]

When you place the device over the tube with the round in position, what keeps the device in position over the tube while the pin is pulled out remotely? It appears to me that the device will fall off the top of the tube when you try to remove the pin.

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein

 

[LittleInch]

More importantly why?

Mortars are short range rapid fire simple devices that have been used for 100 years without anything like this.

I would use a tube the same size and just stick a bar through it to stop the round from falling in the simply pull the bar out with a long piece of string

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[3DDave]

I guess if one wanted to be in a foxhole before the return fire hit, this would give a little more time.

One thing that used to be used is a pneumatic release - a squeeze bulb and a length of tubing. This allows the path from the bulb to the tubing to be less constrained and simply snagging or tripping on the tubing won't release the item. Until the squeeze bulb is in place the device is safe. One can then use a high-force, low motion actuator (pancake pneumatic actuator) attached to a moderately sensitive release without worry. Since the release loads aren't carried to the unit from the squeeze bulb, it cannot pull the tube over. Small diameter stiff plastic tubing should work, The bulb could be sized to be stomped on or triggered with a CO2 cartridge instead.

 

[hydtools]

Something like a long cable gripper/releaser.

Ted

 

[MintJulep]

https://www.mcmaster.com/quick-release-shackles/

 

[IRstuff]

Seems very dubious; 15 meters is about probably less than a 3-second run, but your contraption will easily suck up 3 seconds to set up for each shot, since you cannot afford to have each round already set up. Additionally, you're adding another "thing", or two, that the crew will need to carry in addition to the mortar and ammo and their own weapons, plus the likelihood of losing the release mechanism, which means you probably need to carry two or three of them per mortar.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

https://www.youtube.com/watch?v=BKorP55Aqvg

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[Mechbob1]

Fox, the weight of the item holds it in place.

Inch, it's for testing/safety purposes.

3D Dave - that's a good idea. Sometimes we use compressed air as an actuator, but this is even simpler.

Hydtools - thanks. That's the sort of thing we're after (albeit with a very long cable).

Mint - I like those shackles. Nice find.

IRstuff. When I say 15 metres away, that's how far the nearest person is and they'll be behind some form of protection/wall. The intent is to 'release' the thing from that distance.

FWIW, the design has had a few changes but several initial tests were successful. It released as planned. Not at finished stage yet, but here's where it's at:

 

[kjoiner]

Hello,

I see your mechanism is spring loaded. How about adapting a rotary latch to hole the device shut. You can pull a lanyard or a cable mechanism like Ted mentioned to actuate it.

Kyle

 

[rb1957]

I was just thinking the same ... ditch the spring and latch ... go with an over-center lever.

another day in paradise, or is paradise one day closer ?

 

[LittleInch]

The biggest issue I have with that design is it is not fail safe. If something happens with the holding catch then the clip open and the shell falls into the mortar and goes bang.

Your opening device should be the thing which causes the shell to fall by positive action.

I would not trust the weight of the item to hold it in place myself.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[rb1957]

is this actually handling muntions (things that can blow up) or is it "like" hand-dropping a mortar round down a tube ?

another day in paradise, or is paradise one day closer ?

 

[IRstuff]

How does your mechanism ensure that it doesn't get in the way of the mortar shell? You could potentially damage the mechanism, or even cause the shell to explode on the way out

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

https://www.youtube.com/watch?v=BKorP55Aqvg

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[moa1]

A little pricey. Slip it over the top and fasten. Good luck

https://www.youtube.com/watch?v=HjbxsJ_ZHLY