Mechanical Engineering

# double crank mechanism

## Recommended Posts

i want to make double crank mechanism project

is it right that link (2) =link (4)

and link (3)= the (o2 o4) and parallel???

##### Share on other sites

It is certainly possible that links 2 and 4 have the same length. However, it is not necessary for this to be true. If L2 = L4, that is a special case.

Whatever sort of project can you make from this super simple mechanism?

DrD

##### Share on other sites

it must be fallow the Grashofs law i.e short link+longer link=<sum of other two links.when mechanisim fallow the equal criteria then it will be double crank(locomotive) or crank rocker mechanism.

##### Share on other sites
13 hours ago, MHESWAR REDDY said:

it must be fallow the Grashofs law i.e short link+longer link=<sum of other two links.when mechanisim fallow the equal criteria then it will be double crank(locomotive) or crank rocker mechanism.

The word you want here is "follow," not fallow. To follow is to go with someone or thing, to go where they go. "Fallow" is an adjective that describes a field left for a season to rest without a crop.

##### Share on other sites
On 4/25/2017 at 2:19 AM, DrD said:

It is certainly possible that links 2 and 4 have the same length. However, it is not necessary for this to be true. If L2 = L4, that is a special case.

Whatever sort of project can you make from this super simple mechanism?

DrD

is it known as deltoid mechanism?

##### Share on other sites
9 hours ago, Himanshu Ranjan Dwivedi said:

is it known as deltoid mechanism?

I don't think I have ever heard that term, but who can say?

DrD

##### Share on other sites

I never heard of it either. This claims to be it!

##### Share on other sites
On 5/13/2017 at 1:25 AM, DrD said:

I don't think I have ever heard that term, but who can say?

DrD

I have read that in the book "theory of machines by SS Ratan".

It is a special mechanism of four bar linkage in which the two equal links are adjacent to each other.when any of shorter link is fixed, a double crank mechanism can be obtained.and when any of longer link is fixed two crank-rocker mechanisms are obtained

##### Share on other sites

So, the mystery is solved! We have a name for this gadget!

Sadly, having a name for it makes it no more or less useful. From my perspective, it is the ability to describe this motion mathematically that is important, far more than the name of the mechanism.

DrD

##### Share on other sites

If link 2 and 4 are the same length, the mechanism is unstable at 0° and 180°.  It's possible for the mechanism to "invert" at those locations.  When that happens, link will no longer be horizontal.

## Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

Only 75 emoji are allowed.