So, the handle and the mechanism of the door opening device will be coupled by custard... a well known shear-thickening liquid. This will ensure that only vigorous (non-sneaky) attempts to open the door will cause thickening of the custard and operation of the mechanism. Slow, sneaky quiet attempts to open the door will simply leave the custard in a very liquid state decoupling the handle and the mechanism and leaving the sneaky ninja trapped outside.

Should the movement of the handle not be enough to cause thickening of the liquid... some form of expensive and needlessly complex epicyclic gearbox should be employed.
-- bs0u0155, Sep 04 2011

Yeah, I'd have no respect for a ninja who entered via the door. That's just a rookie mistake, right there.
-- Alterother, Sep 04 2011


Except for the skilled veterans, who can enter through a door and make you THINK they came in a window.
-- normzone, Sep 04 2011


But certainly they'd spot even the most elaborately- concealed custard traps immediately.
-- Alterother, Sep 04 2011


Surely a ninja would just open press the handle down very quickly but totally silently?
-- pocmloc, Sep 04 2011


[+]
-- FlyingToaster, Sep 04 2011


This idea embodies the best in the spirit of the halfbakery and I nominate it for my new Golden Custard award.
-- Voice, Sep 04 2011


// no respect for a ninja who entered via the door //

A really good ninja would dress as a cleaning person and get you to open the door. (I understand that the classic ninja black garb is really that of the stagehands of Japanese theater. They disguised themselves as non-noticed people--that particular garb somehow stuck. (A modern "ninja" disguises himself by dressing like a paparazzo, for instance, which mostly involves carrying a camera.))

Bun for a creative use for non-Newtonian fluid. [+]
-- baconbrain, Sep 04 2011


This is an outstandingly idea.
-- MaxwellBuchanan, Sep 04 2011


Agreed; this is quite definitely the finest idea incorporating both custard and ninjas that we have ever read in the last two hours.
-- 8th of 7, Sep 04 2011


More like old lady proof. Oh noes, the old ladies are coming to get me.
-- rcarty, Sep 05 2011


childproof depending on how fast you have to twist it.
-- FlyingToaster, Sep 05 2011


In childproofing, I recommend twisting the little buggers very fast.
-- baconbrain, Sep 05 2011


I see a happy ninja eating custard from a shiny brass knob-shaped bowl. [+]
-- sninctown, Sep 09 2011


I like this.
If you alternated dilatant and thixotropic fluids of varying densities as in-line tumblers you could make an ergonomic handle turning lock.
-- 2 fries shy of a happy meal, Sep 09 2011


I would suspect a clever ninja would heat the custard up before attempting to open the door slowly.
-- quantum_flux, Sep 09 2011


"I would suspect a clever ninja would heat the custard up before attempting to open the door slowly"

Or freeze it, which would work for both Newtonian and non-Newtonian fluids.

However my clever lock design would have expanding ice pushing a spring loaded second bolt into the door frame for freeze resistance.
-- bs0u0155, Sep 09 2011


Also the custard would be celery-flavour. Rendering it eat-proof...
-- bs0u0155, Dec 07 2011


You could get round this with a vibrating device, it should keep out zombies though.

How about a door handle that is a hand wound air raid siren with a centripugal clutch that engages at a certain speed to open the door.
-- marklar, Dec 07 2011


Or a door handle which consists of a peg and a sledgehammer, like one of those ‘try your strength’ machines at the fair - whack the peg, and the little thingy zooms up the frame and unlatches the door at the top?
-- pocmloc, Dec 07 2011



random, halfbakery