The Naked Scientists
  • Login
  • Register
  • Podcasts
      • The Naked Scientists
      • eLife
      • Naked Genetics
      • Naked Astronomy
      • In short
      • Naked Neuroscience
      • Ask! The Naked Scientists
      • Question of the Week
      • Archive
      • Video
      • SUBSCRIBE to our Podcasts
  • Articles
      • Science News
      • Features
      • Interviews
      • Answers to Science Questions
  • Get Naked
      • Donate
      • Do an Experiment
      • Science Forum
      • Ask a Question
  • About
      • Meet the team
      • Our Sponsors
      • Site Map
      • Contact us

User menu

  • Login
  • Register
  • Home
  • Help
  • Search
  • Tags
  • Member Map
  • Recent Topics
  • Login
  • Register
  1. Naked Science Forum
  2. Non Life Sciences
  3. Technology
  4. Basic dimensioning
« previous next »
  • Print
Pages: [1] 2   Go Down

Basic dimensioning

  • 32 Replies
  • 22008 Views
  • 0 Tags

0 Members and 1 Guest are viewing this topic.

Offline Dansercoer (OP)

  • Jr. Member
  • **
  • 13
  • Activity:
    0%
    • View Profile
Basic dimensioning
« on: 21/03/2009 15:08:12 »

Dear all,

Above is a proposal for a human wheel I would like to make, the inner cylinder would be perforated, similar to http://boards.core77.com/viewtopic.php?t=18087 [nofollow] . The difference with a hamster wheel is that it wouldn’t be stationary and is able to take ( large ) bends. The ribs seem rounded, but that’s only an optical illusion. The intention of the wheel is to give an alternative to the walking paths ( paved green space to keep your shoes clean ) in parks, a new experience with more freedom.

There will be a first estimation of the thickness of the materials (the rings shouldn't be able to amputate a hand, but shouldn't destroy too much grass either), the amount of crossbars and the diameter of the outer rings (wider than the palm of a big hand) using the Cosmos-software. The structure as drawn above would weigh ±80kg in TIG welded aluminium AW-5083 with anti-slip paint, maybe fibreboard is an option too.
But I was wondering how to define the:
- width of the cylinder a
- diameter of the two rings in the middle b

to make sure:
1) the wheel is not too heavy to make it start/stop rolling
2) it is not too difficult to make the wheel lean to one side
3) the wheel is unlikely to fall
( 4)the bends it can take are not too large )


1)

The two forces that I think decide whether the wheel is going to roll or not - rolling resistance and gravity on the person - seem to work in different directions?


2)

The wheel will lean to one side when the combined centre of mass of the wheel and the person in it is not positioned above the resting surface.
(mw.xw - mp.xp) / (mw + mp) = 0
This can be reduced to a function of a and b.


3)

The wheel will not fall when the combined centre of mass is positioned above the resting surface.
But what is the influence of inertia - as a result of the leaning movement - on the position of the combined centre of mass?

All of these could result in a graph with a and b as axes from which I could deduct their ideal value.
Parks are not perfectly flat and there might be wind, so I will have to build in safety margins.
The wheel is not intended for hilly parks with high vegetation that limits sight though.

This product designer is thanking you in advance!
« Last Edit: 29/03/2009 03:51:18 by Dansercoer »
Logged
 



Offline RD

  • Naked Science Forum GOD!
  • *******
  • 9094
  • Activity:
    0%
  • Thanked: 163 times
    • View Profile
Re: Basic dimensioning
« Reply #1 on: 21/03/2009 17:49:19 »
I think this idea is a non-starter: it is impractical and unsafe, sorry.

If this idea is ever realised my suggestion would be take out heavy-duty public liability insurance , you're gonna need it.


 [ Invalid Attachment ]


I would suggest copying a hamster ball, but it's been done.

* SOFT GROUND2.JPG (38.42 kB, 355x455 - viewed 1688 times.)
Logged
 

Offline Bored chemist

  • Naked Science Forum GOD!
  • *******
  • 28880
  • Activity:
    73%
  • Thanked: 1036 times
    • View Profile
Re: Basic dimensioning
« Reply #2 on: 21/03/2009 17:53:41 »
RD, you seem to have just proved that the bicycle won't work.

As long as the ribs on the outside of the wheel are not narrower than bike tyres I don't see a problem with this idea.
Logged
Please disregard all previous signatures.
 

Offline RD

  • Naked Science Forum GOD!
  • *******
  • 9094
  • Activity:
    0%
  • Thanked: 163 times
    • View Profile
Re: Basic dimensioning
« Reply #3 on: 21/03/2009 18:35:45 »
Impractical:-

Will sink into soft ground , (for which it is intended).
 When this occurs changing the direction the wheel is rolling in will be impossible.

Will not protect occupant from ground water & mud, (for which it was designed),
which will enter through metal mesh, (wet/muddy metal is gonna be slippery underfoot).

With dimension “a”  at apparently ~1m this 2.2m diameter aluminium wheel will easily tip over.
(assume worse case scenario when designing with any item for use  by members of public:
some users will deliberately try to tip it over).

Wheel will roll down slopes, (duh!) .
Once it has built up speed, angular momentum is going to make it difficult to stop.


Unsafe:-

The appendages of  occupants and nearby onlookers will be crushed / amputated by the sharp wheel rim.
 More injuries will occur when the wheel is accidentally or deliberately tipped over.

Fingers could get trapped in coarse metal mesh (see your pic below) and injured as wheel rotates.

 [ Invalid Attachment ]

* mesh.jpg (61.14 kB, 600x400 - viewed 1663 times.)
« Last Edit: 21/03/2009 20:19:27 by RD »
Logged
 

Offline LeeE

  • Naked Science Forum King!
  • ******
  • 3382
  • Activity:
    0%
  • Thanked: 3 times
    • View Profile
    • Spatial
Re: Basic dimensioning
« Reply #4 on: 21/03/2009 18:40:40 »
Any wind greater than a brisk breeze could be a problem, from any direction.  Head and tail winds will make it hard to keep going or stop, respectively, and side winds will tend to turn it away from the heading you want or even start it spinning.
Logged
...And its claws are as big as cups, and for some reason it's got a tremendous fear of stamps! And Mrs Doyle was telling me it's got magnets on its tail, so if you're made out of metal it can attach itself to you! And instead of a mouth it's got four arses!
 



Offline RD

  • Naked Science Forum GOD!
  • *******
  • 9094
  • Activity:
    0%
  • Thanked: 163 times
    • View Profile
Re: Basic dimensioning
« Reply #5 on: 21/03/2009 19:25:30 »
This side view is a better illustration of finger / hand hazard...

 [ Invalid Attachment ]


Wheely not a good idea 

* fingers.gif (25.42 kB, 301x375 - viewed 1689 times.)
« Last Edit: 21/03/2009 20:20:39 by RD »
Logged
 

Offline RD

  • Naked Science Forum GOD!
  • *******
  • 9094
  • Activity:
    0%
  • Thanked: 163 times
    • View Profile
Re: Basic dimensioning
« Reply #6 on: 21/03/2009 23:01:29 »
I knew I'd seen this concept before ...

Mono-cycle

Problems when trying to stop (mono-motorbike)...
« Last Edit: 21/03/2009 23:25:28 by RD »
Logged
 

lyner

  • Guest
Re: Basic dimensioning
« Reply #7 on: 22/03/2009 20:19:10 »
The guy in the picture is using a very bright cycle lamp.

btw, have you never seen people Sorbing?
Logged
 

Offline RD

  • Naked Science Forum GOD!
  • *******
  • 9094
  • Activity:
    0%
  • Thanked: 163 times
    • View Profile
Re: Basic dimensioning
« Reply #8 on: 22/03/2009 21:34:36 »
Quote from: sophiecentaur on 22/03/2009 20:19:10
btw, have you never seen people Sorbing?

Like Liza it's with a "zee" ... http://www.zorb.com/main.html

They throw a bucket of water* in the Zorb with the passengers: it must be like being in a washing machine.

[* Maybe this preemptive soaking is to make washing the vomit out easier]
« Last Edit: 22/03/2009 21:50:21 by RD »
Logged
 



Offline Bored chemist

  • Naked Science Forum GOD!
  • *******
  • 28880
  • Activity:
    73%
  • Thanked: 1036 times
    • View Profile
Re: Basic dimensioning
« Reply #9 on: 22/03/2009 21:59:06 »
Quote from: RD on 22/03/2009 21:34:36
Quote from: sophiecentaur on 22/03/2009 20:19:10
btw, have you never seen people Sorbing?

Like Liza it's with a "zee" ... http://www.zorb.com/main.html

They throw a bucket of water* in the Zorb with the passengers: it must be like being in a washing machine.

[* Maybe this preemptive soaking is to make washing the vomit out easier]
I suspect it's because some of the adverts feature young women in T-shirts.
However, since the videos show that essentially the same ide works I can't see why it's impossible. Daft perhaps, but perfectly possible.
Logged
Please disregard all previous signatures.
 

Offline Dansercoer (OP)

  • Jr. Member
  • **
  • 13
  • Activity:
    0%
    • View Profile
Re: Basic dimensioning
« Reply #10 on: 23/03/2009 03:19:07 »
When the outer rings are sufficiently wider than the palm of a big hand - which will be the case -  it will be very hard to grab them the way you would grab a line. The wheel is able to change direction because it behaves like a chopped cone, not like a bicycle where you have to force a wheel to change direction. This same bicycle analogy proves that it won’t sink that much into the ground like bored chemist said; the wheel is heavier and the rings are thinner, but the contact surface is bigger because of the diameter and the fact that most of the time there is more than one ring touching the ground.
Of course the tracks are deeper than footprints, but I have the impression that they are not as harmful to the lawn as a shortcut worn away by pedestrians, just think about lawn aerators. Small rocks shouldn’t be a problem either, the diameter and width of the wheel are too big to feel much of an impact, large rocks can be seen.

I got some good advice though:
I’ll keep the perforations in the metal mesh smaller than the smallest finger without making it non-transparent.

I’ll put the project aside for a little while to think about the worst case scenario, maybe I’m getting too attached to it as well.  [;)]
You’re right, people could deliberately tip over the wheel, there might be a storm (putting the wheel on its side helps) and the angular momentum makes that the braking distance is relatively long (it won’t be anything like the monowheel crash though, this wheel is much wider).
Logged
 

Offline RD

  • Naked Science Forum GOD!
  • *******
  • 9094
  • Activity:
    0%
  • Thanked: 163 times
    • View Profile
Re: Basic dimensioning
« Reply #11 on: 23/03/2009 09:23:17 »
Just noticed yet another problem: muddy water on the wheel will rain down upon the occupant...

 [ Invalid Attachment ]


If you made the wheel double skinned: an inner and outer mesh separated say 30cm, the wheel would be less likely to sink into soft ground and at 30cm impossible to grip, (the outer mesh could be more open than the inner one to maximise visibility). However producing a curved outer mesh would be difficult to manufacture and increase the weight and particularly the angular momentum of the wheel, making it very difficult to start and stop. 

Even ignoring safety issues, this human hamster-wheel idea is a non-starter, sorry.

* mudguard.jpg (51.85 kB, 665x556 - viewed 1625 times.)
« Last Edit: 23/03/2009 09:32:31 by RD »
Logged
 

Offline RD

  • Naked Science Forum GOD!
  • *******
  • 9094
  • Activity:
    0%
  • Thanked: 163 times
    • View Profile
Re: Basic dimensioning
« Reply #12 on: 23/03/2009 10:10:23 »
Even with a 20cm rim it is still possible to run over ones own forearm / hand / digits ...
 [ Invalid Attachment ]

* 2.jpg (44.38 kB, 500x418 - viewed 1541 times.)
Logged
 



Offline Dansercoer (OP)

  • Jr. Member
  • **
  • 13
  • Activity:
    0%
    • View Profile
Re: Basic dimensioning
« Reply #13 on: 23/03/2009 18:08:01 »
It’s like putting a hand between the spokes of a bicycle, but yes it can happen, so I’ll add it to the worst case scenario list.
I don’t agree with the mud though, nothing dripped off when I did a little simulation with a thick knife aka ring.
Dewed grass won’t touch the mesh either as it is too short, which is different in the video.
Logged
 

Offline RD

  • Naked Science Forum GOD!
  • *******
  • 9094
  • Activity:
    0%
  • Thanked: 163 times
    • View Profile
Re: Basic dimensioning
« Reply #14 on: 23/03/2009 20:22:26 »
Quote from: Dansercoer on 23/03/2009 18:08:01
I don’t agree with the mud though, nothing dripped off when I did a little simulation with a thick knife aka ring.

The purpose of the wheel is to prevent feet getting wet, now you're saying the wheel itself will not become wet (?)
The amount of contact between the wheel and the ground & grass will be greater than footprints, (wheel is rolling not stepping),
 i.e. the wheel will gather more water than shoes would, some of which will rain down on the occupant.


Quote
Dewed grass won’t touch the mesh either as it is too short,
[ Invalid Attachment ]


Here's an idea: try going for a walk on park land after rain, wearing ice skates, to see how deep you sink in.

* indexb.jpg (41.98 kB, 355x455 - viewed 1534 times.)
« Last Edit: 23/03/2009 21:32:22 by RD »
Logged
 

Offline Dansercoer (OP)

  • Jr. Member
  • **
  • 13
  • Activity:
    0%
    • View Profile
Re: Basic dimensioning
« Reply #15 on: 23/03/2009 23:35:47 »
Let’s say there’s one footstep of 200cm2 every 75 cm.
200cm2 / 75 cm = 2.7 cm (width for two tracks)
This is a lot more than we need.
No need to make the calculation for the ice skates.

Also, aluminum doesn’t absorb water or mud the way most shoes do, just take your ice skates and make a rotating movement in a puddle. I said the mesh won’t get wet (unless it rains on it), of course the supporting rings will be wet where they touch the ground.
« Last Edit: 23/03/2009 23:42:27 by Dansercoer »
Logged
 

Offline Dansercoer (OP)

  • Jr. Member
  • **
  • 13
  • Activity:
    0%
    • View Profile
Re: Basic dimensioning
« Reply #16 on: 24/03/2009 01:27:10 »
I see RD's response is gone, but anyway, here’s my reply;
Let’s say your (rectangular?) feet sink 1cm.
The width of the smallest ring should be minimum 13cm - the length of a large hand palm - for the digits not to get amputated.
So for the wheel to sink until the mesh you will need a supporting length of 1200 cm2 / (13 x 1,2cm) = 77cm
The wheel would only have to sink 6cm into the ground to get this length as the outer diameter of the small rings is 220cm + 2 x 13cm = 246cm
-> This leaves 7cm until the mesh.
I deliberately took 13cm rather than the bigger central rings, and 1,2cm rather that the fat 2,7cm, both of these are in “your” favour.
Top soil is normally softer too.

Having said this; I still didn’t get any further with my initial questions (in red), could somebody point me in the right direction?
If not, a recommendation for easy to use simulation software might help too.
I’m not ignoring the tips, but making those calculations won’t hurt.
« Last Edit: 24/03/2009 01:29:03 by Dansercoer »
Logged
 



Offline Bored chemist

  • Naked Science Forum GOD!
  • *******
  • 28880
  • Activity:
    73%
  • Thanked: 1036 times
    • View Profile
Re: Basic dimensioning
« Reply #17 on: 24/03/2009 20:05:36 »
People can walk on their hands. The hand is therefore perfectly able to stand the weight of the body. As long as the wheel rim is wide enough to spread the load across most of your hand then, while it might hurt a bit and may even bruise, there wouldn't be any lasting damage. OK, to allow for the weight of the wheel itself you should be careful to err on the side of caution but I still think it's possible.

The talk of ice skates is just silly. Nobody was sugesting an "edge" that thin.

I don't see how anyone can say "Even ignoring safety issues, this human hamster-wheel idea is a non-starter, sorry." when there are videos on YT of essentially the same thing.
Logged
Please disregard all previous signatures.
 

lyner

  • Guest
Re: Basic dimensioning
« Reply #18 on: 25/03/2009 00:00:15 »
Your hands don't need to be outside the periphery of the wheel - they can be on a handle inside, protected.
But, far from protecting you from the wet, the wheel will rotate and lift water from the ground to above your head, dumping it all over you - plus other, not such pleasant things. There is no way it could be going fast enough to shed stuff away from the passenger.
Logged
 

Offline Raghavendra

  • Hero Member
  • *****
  • 833
  • Activity:
    0%
  • Quantum
    • View Profile
    • Raghavendra
Re: Basic dimensioning
« Reply #19 on: 26/03/2009 09:13:17 »
 I should re-open my old books and study again...
Logged
 



  • Print
Pages: [1] 2   Go Up
« previous next »
Tags:
 

Similar topics (5)

Discuss: Can we create a living organism from basic elements?

Started by thedocBoard Chemistry

Replies: 1
Views: 5646
Last post 13/02/2006 00:18:58
by wim
Can a cell phone replace a basic laptop computer?

Started by KarstenBoard Technology

Replies: 37
Views: 27620
Last post 09/02/2011 23:17:38
by briligg
QotW - 12.06.10 - Can we create a living organism from basic elements?

Started by thedocBoard Question of the Week

Replies: 7
Views: 6892
Last post 30/05/2012 21:45:47
by CliffordK
Could basic life have formed in the suns accretion disk?

Started by acecharlyBoard Physics, Astronomy & Cosmology

Replies: 2
Views: 4417
Last post 14/06/2012 08:20:33
by chris
Want to see my FREEZERBATON? Freezer-baton for basic cryosurgery on a budget!

Started by Peter DowBoard Technology

Replies: 22
Views: 15151
Last post 24/05/2014 08:29:42
by alancalverd
There was an error while thanking
Thanking...
  • SMF 2.0.15 | SMF © 2017, Simple Machines
    Privacy Policy
    SMFAds for Free Forums
  • Naked Science Forum ©

Page created in 0.159 seconds with 80 queries.

  • Podcasts
  • Articles
  • Get Naked
  • About
  • Contact us
  • Advertise
  • Privacy Policy
  • Subscribe to newsletter
  • We love feedback

Follow us

cambridge_logo_footer.png

©The Naked Scientists® 2000–2017 | The Naked Scientists® and Naked Science® are registered trademarks created by Dr Chris Smith. Information presented on this website is the opinion of the individual contributors and does not reflect the general views of the administrators, editors, moderators, sponsors, Cambridge University or the public at large.