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Join Date: Oct 2016
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School Project Requires Creative Solutions

10/09/2016 12:43 PM

As part of a Product Design course in my final year of sixth form, I have been given the task of designing and creating something innovative of my own choice. The idea I have chosen is to find a way to create a device that can be mounted onto an existing barbecue that can turn food similarly to a rotisserie but without any mains power required and with minimal input from the user.

My original idea was to use a fan to power the device from the rising heat from the barbecue however i have also explored idea of solar power and intermittent manual input as I am sceptical as to whether the fan idea will work.

My question is, would it be possible to have a device use the energy from the rising air to turn a rotisserie and what be the best way to make this possible such as using gear trains to change the torque required from the fan?

As well as this, what other ways could there be of powering the device? electronics can be used as long as mains power isn't required.

The barbecue I intend for the product to be designed for is the Weber Original Kettle as that is what i have available, it is 590mm in diameter so the product needs to be compact.

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#1

Re: School Project Requires Creative Solutions

10/09/2016 1:04 PM
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#2

Re: School Project Requires Creative Solutions

10/09/2016 1:04 PM

Very unlikely that you can generate enough force from rising flue gases to turn much of anything, let alone a chicken on a spit. Figure out the differential pressure between the ambient air and the flue gases and calculate the volume of flue gas you will need to exert your desired force. A hot air balloon should give you an idea of the relative volumes needed.

Have you quantified the forces necessary to turn a chicken on a spit yet? This is how you start to define your requirements. Be sure to do the systems engineering and lay out all your requirements and constraints.

Not that your idea is a bad one but if I were doing it, I would look at how you can use a "steam engine" that would take it's energy from the heat of the grill. You can also investigate thermopiles to see if you can make something work there. Also research Stirling engine.

Good luck with your quest. This is why we call it an "education".

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#3

Re: School Project Requires Creative Solutions

10/09/2016 1:12 PM

Thanks very much, ill do some more research to find out what the requirements are and ill look into using some kind of small scale steam engine

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#14

Re: School Project Requires Creative Solutions

10/09/2016 7:24 PM

That would make this a real "Steampunk" project.

P.S. Please be very careful if you decide to work with steam. Understand what relief valves are for and ASTM rated pressure vessels. Both burns and shrapnel wounds are nothing to be trifled with. I truly hope your academic advisor will be an active participant all along this process.

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#16

Re: School Project Requires Creative Solutions

10/09/2016 7:27 PM

Maybe that's what they do in final year of sixth form, whatever that is.

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#26

Re: School Project Requires Creative Solutions

10/10/2016 11:59 AM

..."In the education systems of England, Northern Ireland, Wales and some other Commonwealth countries, sixth form (sometimes referred to as Key Stage 5) represents the final two years of secondary education (high school), where students (typically between 16 and 18 years of age) prepare for their A-level (or equivalent) examinations."...

https://en.wikipedia.org/wiki/Sixth_form

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#28

Re: School Project Requires Creative Solutions

10/10/2016 12:40 PM

Thanks. Semantics again.

I think a spring driven motor, as in an old phonograph, may bear consideration.

This was suggested earlier.

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#20

Re: School Project Requires Creative Solutions

10/10/2016 5:50 AM

I like the idea of a hot-air balloon. You could tether it on a long string wrapped round a drum on the axle of the spit/rotisserie. When you release the balloon the spit goes round. The rate of rise of the balloon is limited by a governor which is actually a fan blowing air through the barbecue to ensure good burning.

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#4

Re: School Project Requires Creative Solutions

10/09/2016 2:13 PM

If the goal of the project is to " make life better/easier" then I suggest multiple Hamster wheels connected to a gear box that drives the turning mechanism. This is a two fold winning approach.

1. It is innovative, at least never before done.

2. Hamsters are fairly ubiquitous and cheap. Get some and they will breed rapidly to produce replacement power sources.

3. Once the power source is depleted(dead) it can be cooked on the Bar-B-Q and eaten.

If this sounds silly, think about how silly a steam engine sounds.

Your first goal should be to select a feasible project.

Back to the drawing board.

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#19

Re: School Project Requires Creative Solutions

10/10/2016 4:59 AM

While it may not have been done with hamsters, it was often done with small dogs.

There was even a breed of dogs developed specifically for the purpose.

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#22

Re: School Project Requires Creative Solutions

10/10/2016 9:50 AM

Wow, who would have ever thought.

I recon that it would take 12 hamsterpower to equal one dogpower.

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#27

Re: School Project Requires Creative Solutions

10/10/2016 12:12 PM

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#29

Re: School Project Requires Creative Solutions

10/10/2016 1:39 PM

Quite. They've had (long disused) dogspits in a couple of old pubs I've visited. They've stiĺl had the fire and done roasts on the spit, but the treadmill's been disconnected and the spit was turned by an electric motor .

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#5

Re: School Project Requires Creative Solutions

10/09/2016 2:23 PM

Two ideas come to my mind right away: a spring-drive mechanism, like in an old fashioned wind-up watch , that can be rewound as needed. The second is a weight-drive mechanism, like a grandfather clock, which also can be reset as needed.

But these are MY ideas, so you're not allowed to use them.

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#33

Re: School Project Requires Creative Solutions

10/11/2016 10:25 AM

I agree with the spring driven device but you have to keep it wound. So my suggestion is design an added shelf with a special device that attaches to a can of beer. Now that device is attached by a string that when pulled, winds the spring. Obviously the spring will be wound at regular intervals keeping the rotisserie going as long as needed. Done.

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#6

Re: School Project Requires Creative Solutions

10/09/2016 2:43 PM

The more 'Geewiz' technology, the more expensive...To keep something affordable and practical you need to stick with the KISS principle...There are plenty of battery powered rotisseries on the market....you could add a solar charger....15 watt motor can handle 25lbs according to the manufacturer...The rotisserie needs to be stainless touching any food surface....

http://spitjack.com/category/ROTISSERIES.html

Charge controller...

If you want to throw reason and practicality out the window, and you have nothing but time on your hands, and deep pockets, you could go with an organic rankine cycle device...

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#7

Re: School Project Requires Creative Solutions

10/09/2016 3:23 PM

It doesn't seem very "innovative" when I can do a search for "Cordless Rotisserie" and get a bunch of hits.

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#8

Re: School Project Requires Creative Solutions

10/09/2016 3:25 PM

But, has it ever been done with Hamsters?

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#9

Re: School Project Requires Creative Solutions

10/09/2016 3:39 PM

Lots of things done with hamsters, but . . .

Anonymous Poster #1
#11

Re: School Project Requires Creative Solutions

10/09/2016 5:03 PM

You should see the engine room on Holland America Lines' Hamsterdam.

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#15

Re: School Project Requires Creative Solutions

10/09/2016 7:25 PM

Who shovels it out?

Anonymous Poster #1
#17

Re: School Project Requires Creative Solutions

10/09/2016 10:08 PM

The same sort of guys that used to be called "stokers"; just shoveling out rather than in.

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#10

Re: School Project Requires Creative Solutions

10/09/2016 4:07 PM

I have to admit that being able to eat the "power supply" when you are done with it is quite innovative!

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#18

Re: School Project Requires Creative Solutions

10/09/2016 11:33 PM

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#12

Re: School Project Requires Creative Solutions

10/09/2016 5:04 PM

A spinning marshmallow on a stick could be what you need.

It may sound like novelties, but it's simple.. Low cost and could be driven by a small fan.

I know there's market because I've seen a lot of people that couldn't roast one if their hamies life depeneded on it! ��

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#13

Re: School Project Requires Creative Solutions

10/09/2016 5:45 PM

Once you have defined the required power to turn the spit, then you can look at what technologies will fit the application.

Since you are talking about a barbecue grill, the difference in temperature between the bottom of the pan and the ambient air suggests using a TEG.

Good luck!

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#21

Re: School Project Requires Creative Solutions

10/10/2016 6:15 AM

Have a look at "Hero's Aeolipile" for some inspiration. The heat from the cooking creates steam and the direted outlets create movement.

You would need some gearing.

CAUTION: Since you say you are in year six, I'll state what will be obvious to others here. The steam device must NEVER be sealed.

A more complicated device could be based on the "Ctesibian Pump" connected to the rotisserie shaft.

I am suggesting that you use these for inspiration, not to copy. Innovation is he outcome of you seeing the hidden capabilities that have always been possible.

(The Egyptians could have produced functional hang gliders using bamboo and cloth that was available at the time, but nobody did since nobody recognised the possible innovation that would make the outcome possible.)

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#31

Re: School Project Requires Creative Solutions

10/10/2016 6:33 PM

As a case in point, Time magazine once published a sidebar article that claimed that, according to court records, some bright someone actually did build (something similar to) a hang glider, somewhere in South East Asia, maybe a thousand years ago. Being justifiably proud of his creation, he took it to his (regional governor, local authority, grand poobah, other) and tried to give it to him as an honor to (the big-shot). However, the local (advisors) dismissed his claims as impossible, of course... But, the builder persisted, until the court business was all settled, and the advisors thought the (Big Deal) would enjoy a good laugh, while watching this presumptuous ignorant peasant make a fool of himself, and probably killing himself in the process. The relevant players in the drama gathered at a remote spot and bade the builder commence to demonstrate his contraption. But, against all odds, he actually flew the thing at some notable height for some notable distance. The court was shocked with disbelief, and furiously discussed what to do about it all. The (supposedly wizened advisors) finally told the (big Cheese) to confiscate the apparatus, throw it down the deepest well, and then, behead the builder for (disrupting the court's peace of collective mind), which was all subsequently done... It seems that they were afraid that if anybody else had seen the flight, that they too would dream of flying also. This could just not be allowed to happen. And so, in all their supposed wisdom, they lost a chance to gain potential (control of the air) over all their military opponents, and were eventually replaced by the next in a long line of conquerors, once again. So, it may not pay to create a breakthrough invention until the (power-structure) desperately needs it... (ie: it's not enough to have a great idea, if you don't have great timing, as well...)QED

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#34

Re: School Project Requires Creative Solutions

10/31/2016 1:06 PM

The further point being:

Don't just ask what could be done;

Don't just ask what people want to be done;

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#23

Re: School Project Requires Creative Solutions

10/10/2016 10:53 AM

I don't know if this matters or not:

A. The weber kettle uses charcoal briquets.

B. Briquets in their burn process will produce different degrees of temperature and that will affect flue pressure.

C. A method would need to be devised to regulate the inflow of briquets to regulate a constant in the flue gas pressure and temperature.

D. Regulation would be necessary to ensure that the spit turns at a constant controlled speed and for the necessary duration as required to completely cook whatever food was placed upon the rotisseries spit.

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#25

Re: School Project Requires Creative Solutions

10/10/2016 11:18 AM

Hamster on a stick, turn it yourself.

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#24

Re: School Project Requires Creative Solutions

10/10/2016 11:12 AM

they make peltier run fans for wood stoves to circulate hot air. Take the fan off and put on a small pulley.

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#30

Re: School Project Requires Creative Solutions

10/10/2016 5:50 PM

So, get on with it already...

Pick a method, any method, and build a simple prototype, fix it when it breaks and/or upgrade it if it doesn't break...

At least you'll have something done by the due-date...

(to a receptive inventor, failure can be a great mentor...)

(''tempis'' just keeps on ''fugit''-ing whether you watch the clock or not...)

(and show us some photos when you're done...)

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#32

Re: School Project Requires Creative Solutions

10/11/2016 10:15 AM

The way I see it if people are too lazy to turn their own food over while cooking with a BBQ grill the odds are they are too lazy to ever bother cooking with a grill to begin with thus the whole food flipping problem is not a real issue.