Engineering project, leaving cert 2012

partyatmygaff · 18-10-2011 10:46pm

A central switching console is just that. A control panel of some sort that controls both power and steering of the front wheels.

As for your power question... Say we have two identical 9v batteries with a maximum current output of 200mA.

Wired in parallel your power supply will be:
9v
400mA

Wired in series your power supply will be:
18v
200mA

Darth Frodo · 18-10-2011 10:53pm

But what if the batteries are completely independent of each other. ie one battery and one side another at the other side. What if they're not wired in a parallel or series circuit??

partyatmygaff · 18-10-2011 11:00pm

Well if they're completely independent of each other there's no change whatsoever to their power ratings.

It won't look too good from a design point of view though. I'd avoid more than one power source as it just adds excessive weight and adds more points of failure.

Darth Frodo · 18-10-2011 11:02pm

Great! Thanks for your input! Much appreciated!

partyatmygaff wrote: »

A central switching console is just that. A control panel of some sort that controls both power and steering of the front wheels.

When you say this do you mean to say that they must be steered independently?

partyatmygaff · 18-10-2011 11:08pm

Darth Frodo wrote: »

Great! Thanks for your input! Much appreciated!

When you say this do you mean to say that they must be steered independently?

No. Sure what good of a steering system would it be if the wheels pointed in different directions? :P

They're just asking for a central control panel of sorts where you can adjust the power and the angle of the wheels. I had one on my snowmobile last year as a matter of fact.

Darth Frodo · 18-10-2011 11:11pm

So when it says "central switching console" what does the switching refer to?

partyatmygaff · 18-10-2011 11:27pm

Darth Frodo wrote: »

So when it says "central switching console" what does the switching refer to?

Switch: To change the direction of something where "something" is your set of front wheels.

It's an odd way of using the word but it's perfectly valid too.

Darth Frodo · 18-10-2011 11:29pm

EXCELLENT!!!!!
Thank you very much. I can now finish off my analysis.

IIIAcHmEdIII · 19-10-2011 9:53pm

Hi guys just wondering if you used two rheostats (variable resistors) on the two motors in the front to steer . This way you could speed up one wheel and slow down the other to turn my interpretation of it would be that im using an electrical mechanism for steering . Would make it a fair bit easier .

Thanks

partyatmygaff · 19-10-2011 10:18pm

It wouldn't work very well unless you had both the back and front wheels connected to the motors. Even at that it'd be very user unfriendly and difficult to use.

Trying to rotate a four wheeled car about its central axis by just rotating a single front wheel is nigh on impossible.

IIIAcHmEdIII · 19-10-2011 10:31pm

Thanks for the reply but my idea does not consist of 4 wheels so i was hoping this would count as my steering mechanism and the switching console and just use the two rheostats and a DPDT (double pole double trow) switch in a wired controller to control it . Thanks

partyatmygaff · 19-10-2011 10:46pm

Well the brief specifies "front" wheels. That implies you'll need wheels at both longitudinal ends of the vehicle.

I'd say just stick to a four (Or more) wheeled front wheel drive vehicle so you don't lose any marks for not meeting the conditions of the brief.

IIIAcHmEdIII · 19-10-2011 10:58pm

partyatmygaff wrote: »

Well the brief specifies "front" wheels. That implies you'll need wheels at both longitudinal ends of the vehicle.

I'd say just stick to a four (Or more) wheeled front wheel drive vehicle so you don't lose any marks for not meeting the conditions of the brief.

Thanks i was thinking along the ines of more than 4 wheels anyway but dont want to give away to much coz the design i have is very out of the box thinking =P but yet the simplest i can think of . Thanks

laoch na mona · 19-10-2011 11:06pm

it seems grand it only took one class brain storming session for everyone to have it figured out more or less

laoch na mona · 19-10-2011 11:13pm

TW Mr Tayto wrote: »

This seems very Scrapheap Challenge, if only!

What materials are people thinking?
Obviously engineering is seen as a follow-on from metalwork; but most of my plan is plastic ATM.
I'm having Aluminium mud-guard looking things on the back, for now.

aluminium and plastic at the moment

joe mc mahon · 20-10-2011 6:08pm

anybody have a portfolio from last year in which they would like to email it to me ?

Cuppa tae · 20-10-2011 7:30pm

partyatmygaff wrote: »

A central switching console is just that. A control panel of some sort that controls both power and steering of the front wheels.

I understand the central switching console to have nothing to do with powering the steering.

I took the central switching console to mean the ability to adjust the speed of the individual wheels independently.

Nowhere in the brief does it say the steering must be motorised

partyatmygaff · 20-10-2011 7:37pm

Cuppa tae wrote: »

I understand the central switching console to have nothing to do with powering the steering.

I took the central switching console to mean the ability to adjust the speed of the individual wheels independently.

Nowhere in the brief does it say the steering must be motorised

No one said that a "central switching console" need be completely electronic either...

Basically, to put it in much clearer English they're just looking for a centralised user interface. One place for all the controls.

One important thing to note about the two motor set up you'll have to use for your front wheels. Use the same type of motor for both wheels and make sure they both receive equal amounts of power. Having one wheel rotate faster than the other is going to cause you all sorts of problems.

Cuppa tae · 20-10-2011 9:59pm

So would i lose marks if i had a completely manual steering system?

The only electronics would drive my two front wheels

mousi · 20-10-2011 10:15pm

Cuppa tae wrote: »

So would i lose marks if i had a completely manual steering system?

The only electronics would drive my two front wheels

No you wouldnt because all the brief says about the steering is that it should hace "a stteering mechanism for the front wheels" it doesnt say it has to be electric or manual, so it can be either.

Neodymium · 20-10-2011 11:20pm

mousi wrote: »

No you wouldnt because all the brief says about the steering is that it should hace "a stteering mechanism for the front wheels" it doesnt say it has to be electric or manual, so it can be either.

Definition of a mechanism:

mechanism

1. (Engineering / Mechanical Engineering) a system or structure of moving parts that performs some function, esp in a machine
2. something resembling a machine in the arrangement and working of its parts the mechanism of the ear
3. (Engineering / Mechanical Engineering) any form of mechanical device or any part of such a device

The brief:

The LRV should:
a) Have propulsion units to provide individual drives for both front wheels;
b) Incorporate a central switching console to operate the front wheels;
c) Include a steering mechanism for the front wheels;
d) Have seating capacity for the driver only.

From point 'a' it says propulsion units (notice the plural) with individual drives for both wheel, so there should be more than one motor. By having a motor for each wheel then you already have an electrical steering 'mechanism'. If the LRV only has to steer using its motors, then point 'a' would encompass point 'c', so why would they include point 'c'? They would be making it far too easy if you only had to have it steering by varying the speed of each motor.

I'd say you would be safer including the individual motor for each wheel and some sort of a mechanical steering mechanism.

I've got something like a rack in pinion in mind, something like this maybe:

The rectangular blocks at each side are a motor and gearbox in one, they're very compact and have a lot of torque. I don't have the pinion shown, but when it is turned clockwise the rack moves to the left and right when anti-clockwise. The rack is connected to the motors by a bracket which pivots where the screw is shown.

conorfitz · 24-10-2011 12:34am

Hi, Just wondering what kind of software you used to make that image?

fullback4glin · 24-10-2011 3:08pm

SolidWorks I'd be guessing

Leftyflip · 25-10-2011 4:50pm

So where are people at in their projects now? Anybody made a start on the actual model?

fullback4glin · 25-10-2011 6:14pm

Just finishing off investigation and research... Next stage is making a cardboard model, might start it over midterm

Sherman_ator · 26-10-2011 3:33pm

Made an account just to offer this idea,As I myself am debating over whether or not it would be accepted;
Why not have 2 arrays of Dual AA batteries?Im not sure what the motor performance would be like but power output would be well below 9V.It would also save me having to dick around with circuits,instead I just have a battery,switch and motor to deal with

spurious · 26-10-2011 9:21pm

Having worked for the SEC, I wouldn't advise candidates to post images or specific details of their exam work on boards.

General discussion of materials or construction is fine, but personally I'd steer clear of anything too specific.

TW Mr Tayto · 27-10-2011 8:17pm

I've never been the best guy for electronics, I love them to bits; but we've never really done more than brush over them in school.

Could I have a 9V battery powering my wheels, and a small (say a watch battery or two) powering something else?
Would the project be discounted if the TOTAL voltage was more than 9V? They'd be on different circuits.

Bigbaddan · 27-10-2011 10:35pm

Hey everyone,
I have read the brief and everythin bout 2 different motors for each wheel but the only real thing thts botherin me is the steering mechanism! Is there sometin I could use that can pivot the wheels and have the both turn left and right??

Cheers

partyatmygaff · 27-10-2011 10:50pm

TW Mr Tayto wrote: »

I've never been the best guy for electronics, I love them to bits; but we've never really done more than brush over them in school.

Could I have a 9V battery powering my wheels, and a small (say a watch battery or two) powering something else?
Would the project be discounted if the TOTAL voltage was more than 9V? They'd be on different circuits.

You won't lose marks for exceeding 9V. You'll lose marks for redundant weight. Unless you've got a solid reason for including two independently powered circuits then you should stick to one power source and just use that to supply power to all your electronics.

If I were you, i'd use stripboard or a simple PCB to make a power supply of some sort. Just connect a 9V battery to different voltage regulators and you'll have your own multi-voltage power supply. A much more impressive solution than mounting batteries on every section of your project.

Engineering project, leaving cert 2012

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