Can anyone help for the school assignment

[kushab]

the circles are not concentric and the line is vertical.

Drawing5.dwg

[kushab]

the circles are concentric sorry

[JD Mather]

Then draw the second circle again. (you did erase it and the line like I instructed - correct?)

 

When drawing the second circle

type C and hit Enter

Click ON the first circle (AutoCAD will find the center point for you)

type D and Enter

type 3.5 and hit Enter (Edit: I see you now have this correct in Drawing5)

 

type L and hit Enter

click on the circle (AutoCAD will automatically find the center of the circle)

 

click above the circle (in Drawing5 you attached the line is not vertical and is not a simple Line)

 

It should look like this

[kushab]

after the vertical line what is the next step

Drawing6.dwg

[kushab]

Which is the next step

[JD Mather]

OK, now go back and look at posts #11 & 12 (or was it 12 & 23? I hate to go back and check because my internet connection is painfully slow)

 

Click on the vertical line to select it.

Click on the handle of the line that is at the center of the two circles.

 

Now comes the most difficult function of the entire process to draw this mechanism -

click the Right Mouse Button and select Rotate

click the Right Mouse Button again and select Copy (pure logic here - we want to copy the vertical line with a rotation of 65°)

type in -65 and hit Enter

 

Save and attach the file here.

[kushab]

I also finished the two circles, if they are wrong tell me . My internet conection is slow too!

Drawing7.dwg

[JD Mather]

OK, you got it correct.

 

I would have told you

draw the Ø.75 circle at the intersection as you did.

I then would have told you to draw a R3.75 circle at the same intersection (center of the .75 circle)

This would give you the location for the Ø.5 circle at the intersection of the vertical line and the R3.75 circle.

I'm not sure if you did it my way, but you have it in the correct location.

 

Now

type L and hit Enter

hold the Shift key down on the keyboard and click the Right Mouse Button.

Select Tangent

and click the 1.75 circle at about the tangent location

Shift Right Mouse Button select Tangent again and select the .75 circle

repeat on the other side.

 

Repeat between the .75 circle and the .5 circle.

 

Save and attach the file here.

(we will worry about changing the hidden lines to dashed later)

[kushab]

You are really helping and learning me at the same time .Thanks a lot.

Drawing8.dwg

[JD Mather]

Well, I have to go away for a while - so I am going to go ahead and explain the LOGIC of why I would do the Crankshaft first and the Piston as the last part. Of course you can do the parts in any order, but the logic -

 

at some point I assume you are going to want to design REAL mechanisms. (and this means 3D digital prototyping of mechanisms that work like they will in the REAL world.

 

First you would want to pick the MOST logical datum.

In this case the Crankshaft has one Degree of Freedom (DOF) - a rotational DOF. (assuming X to right and left, Y up and down, and Z in and out of the screen) this DOF is rotation around the Z axis.

 

You would model the part (doesn't matter what it is, in this case it is a Crankshaft) and test the motion to verify that it has the one desired DOF, rotation about the Z axis and no other DOF.

 

Then you would model the Connecting Rod.

The Connecting Rod has 3 DOF at the crank end (translate in X and Y and rotate about z at connection) and 2 DOF at the connection to piston.

 

In digital prototyping the initial kinematic testing would show that the X translation would need to be constrained at the piston end.

 

We would then create the piston. Initially it would have 6 DOF (three rotational and three translational)

We would constrain to Y axis (or to cylinder wall) and to the connection rod. Kinematic testing would show only one translational left for the piston and one translational and one rotational DOF for the connecting rod at the piston end.

 

By following the logic of how the mechanism works (or is supposed to work) in the digital prototyping process we don't get ourselves into a case where the mechanism doesn't work as expected and we can't (easily) figure out why. I see lots of beginners not follow a logical process and then pull their hair out taking wayyyyyy too much time trying to get their mechanisms (again, I am using this simple mechanism only as a basis for ANY mechanism) to work.

 

Develop a disciplined, logical, step-by-step process and you will become more accurate and faster than your competitors.

[JD Mather]

You are missing a step.

You MUST Shift Right Mouse Button select Tangent for placing BOTH ends of the lines (there is an automatic way, but I want you to master this way first.)

 

Your lines are not tangent at both ends.

 

[kushab]

ok Thanks a Lot .

[JD Mather]

Then next steps would involve creating a horizontal line through the center of the Ø.5 and then a bunch of Offsets of the horizontal line(s) and the vertical line, followed by trim(extend?)s.

[JD Mather]

Are you making any progress on your own?

 

I think most would consider it alarming that you have been given an assignment like this without prior instruction on creating concentric circles or tangent lines. Does your instructor know how to use AutoCAD? How much did you pay for this class?

[kushab]

THe course is free and the teacher isn't good enough. I arrived until here it has a mistake between the 0.75 and .50 circles i do not now how

Drawing10.dwg

[JD Mather]

There are mistakes with most everything you have done except for the bottom and sides of the piston.

 

First

all of the tangent lines between the 1.75 and .75 and between the .75 and the .5 circles are incorrect.

You must follow this procedure precisely (this is the third time now I've explained.

 

Delete your four tangent lines.

 

1. type L and hit Enter

2. hold Shift key and Right Mouse Button then select Tangent

3. click on the bottom of the 1.75 circle

4. hold the Shift key and Right Mouse Button then select Tangent

5. click on the bottom of the .75 circle

 

6. Hit Escape

 

7. type L and hit Enter

8. hold Shift key and Right Mouse Button then select Tangent

9. click on the top of the 1.75 circle

10. hold the Shift key and Right Mouse Button then select Tangent

11. click on the top of the .75 circle

 

Now repeat steps 1-11 on the SIDES of the .75 and the .5 circles.

 

Attach the file here.

[kushab]

Can you post every step until the end here, because I finished one with mistakes and sent to the professor and told him that I have some mistakes, I told him that i will fix later. Thanks for your time

[JD Mather]

Attach file here with the corrected tangent lines, then we can continue to the end.

[mikekmx]

Can you post every step until the end here, because I finished one with mistakes and sent to the professor and told him that I have some mistakes, I told him that i will fix later. Thanks for your time

 

 

 

lol dude, without wishing to blow smoke up JD's ***, you have by chance/luck got an autocad uber-user/teacher to assist you with this. you will not find better advice.

 

my advice: do exactly as he says, no more no less & do it promptly. you could've easily had this done by now.....

[ReMark]

Next he'll be asking JD just to do the assignment for him.