Designing Mechanism - Updated

1. Nov 30, 2012

pikachoo

Designing Mechanism -- Updated

Anyone got any idea on how to design a mechanism that…
◦Translates rotational motion (clockwise OR anti-clockwise) to linear motion
◦Linear motion ONLY to the right
◦Upon release, the mechanism returns to its initial state

2. Nov 30, 2012

Simon Bridge

Re: Designing Mechanism

Is it the device itself that has to have linear motion or is it supposed ti be some sort of launcher?

That last one will probably require an energy store - particularly if it is a launcher.

Look at a tennis ball launcher or those flywheel-powered toy cars.

If the idea is that you turn a wheel either way and the machine goes to the right, you are looking for some sort of ratchet mechanism and/or gears... so you either engage the drive wheels in one direction or the direction of turn engages either forward or reverse gear.

3. Nov 30, 2012

pikachoo

Re: Designing Mechanism

I had to do this based on the information i learned such as cams,linkages for eg.

most probably it should just be a part...

4. Nov 30, 2012

Simon Bridge

Re: Designing Mechanism

OK then - enjoy :)

5. Nov 30, 2012

pikachoo

Re: Designing Mechanism

so what kind of mechanism do you suggest cause i really dont get what you mean :(

Last edited by a moderator: Dec 31, 2012
6. Dec 1, 2012

CWatters

Re: Designing Mechanism

The problem statement appears incomplete. I think that's what Simon is saying.

I can imagine making something like that from the crank shaft, connecting rod and piston from an engine (and perhaps a spring to meet the last condition).

7. Dec 2, 2012

Simon Bridge

Re: Designing Mechanism

Even with a spring - you won't get return to initial conditions .... unless you used the spring as a reservoir for energy. The design description we have would involve violations of the law of conservation of energy otherwise: it's doing work remember.

The problem statement is wide open.
We don't know if this is to be a launcher or an engine for example.
Post #3 suggests that it has already been done anyway.

You can design a 2-wheel system, for example, where one wheel drives the other - the driven wheel always turns the same way regardless of the direction of the first. That do?

8. Dec 30, 2012

pikachoo

Some mechanism to work on

1. Does anyone know why does the wind up toy only allows rotation in one direction?

cause i have to think of a mechanism that
Allows rotation in one direction
CAN’T use ratchet & pawl

i am trying to build the idea upon the wind up toy ._.

next up i have to think of a mechanism that
Translates rotational motion (clockwise OR anti-clockwise) to linear motion
Linear motion to the right
Upon release, the mechanism returns to its initial state

i am thinking of using cams and maybe spring for return to its initial state but i dont really know how to link them up.

May i also find out how does the cam-follower is being joined to the cam?

Thanks

9. Jan 1, 2013

pikachoo

Re: Designing Mechanism -- Updated

does anyone why does wind up toy only works when it is being rotated in one direction? i cnat find any answer on9 >_>

10. Jan 1, 2013

MrWarlock616

Re: Designing Mechanism -- Updated

How about something like this with a spring?

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11. Jan 1, 2013

pikachoo

Re: Designing Mechanism -- Updated

thanks, but i dont get what u mean

12. Jan 1, 2013

Staff: Mentor

Re: Designing Mechanism -- Updated

A windup toy being one with a windup key? It uses a clock spring, and you can wind up a clock spring only one way. It doesn't use a linear [coiled] spring.

13. Jan 1, 2013

Simon Bridge

Re: Designing Mechanism -- Updated

The key tightens the coil-spring. The spring, therefore, unwinds in only one direction - opposite the winding - determining the direction the mechanism turns. You'll find this in every diagram of clockwork.

It is technically possible to store energy in a coil spring by unwinding it - but this is not usually efficient. There are usually mechanical constraints (i.e. the spring has to fit inside a small watch-case) restricting this choice.

You could as easily make a clockwork mechanism with a linear spring - you'd have to choose whether to energise the mechanism by compressing or extending the spring and that would determine the direction of the mechanism too.

14. Jan 2, 2013

CWatters

Re: Designing Mechanism

Rotating the crank in either direction causes the piston to move.

The piston only moves to the right of the rest position.

Upon releasing the crank the spring returns the crank and piston to the initial position.

Ok so rotation of the crank is limited to half a turn but you can fix that with gearing.

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15. Jan 2, 2013

Simon Bridge

Re: Designing Mechanism -- Updated

I still think the description of the problem is incomplete.