Geometrical Problem Solving?

[CAD_Spider]

Hello

 

I started using AutoCAD a few months ago, and I completed a college assessment. During the learning process, I developed some bad habits with regards to geometrical problem solving. The college taught me absolutely nothing on the subject, and I don't want to start an advanced course until I'm proficient with geometry.

 

Can anyone recommend a book or online tutorial, that would enhance my skills in this area? I have attached an image to help you understand my point of view. One task on my course involved drawing a screwdriver. The attached image shows the construction of the screwdriver handle. The solid lines are part of the screwdriver's shape, whilst the dashed lines are construction lines.

 

What tells a draughtsperson to draw a "construction circle" with r27.5, and another construction circle with r12.5, on the far RHS of the horizontal line? Am I overlooking the bleedin' obvious?

 

Thank you!

[Strix]

you've got me stumped!

 

what was the wording on the assignment?

 

still can't figure out what we're supposed to be looking at in that drawing

[CAD_Spider]

you've got me stumped!

 

what was the wording on the assignment?

 

still can't figure out what we're supposed to be looking at in that drawing

 

Sorry .... I've attached a picture of the screwdriver handle. The wording is, "Using relevant commands draw the screwdriver as shown in the diagram".

 

Does that clear things up? Thank you for trying!

[Strix]

ah, that makes a bit more sense

 

what's your arithmetic like? - you're going to need it :wink:

 

which point did you start your drawing from?

[CAD_Spider]

ah, that makes a bit more sense

 

what's your arithmetic like? - you're going to need it :wink:

 

which point did you start your drawing from?

 

My Rithmatic is fairly good

 

I started by drawing the circle with a radius of 15. Then, 30 units below the centre of that circle, I drew the horizontal line (17mm in length). Could you give me guidance about the next stages? I can do this particular task, but only after minimal guidance from a college tutor . I don't understand the logic that led to the construction circles (see the diagram at the top of the thread)

 

Thanks!

[Strix]

look at the smaller circle.... of radius ?.....

 

now what do you get if you subtract the biggest circle from it's inner circle?

[dbroada]

One thing you will find out quickly is that there is almost an infinite number of ways to do the same thing in AutoCAD. I'd say you are pretty much there apart from possibly using the 30 dimension to position the big circle. I use XLINE to draw my known construction but the drawing can get cluttered if I'm not careful. Colouring the lines also helps.

[Strix]

DB - is there an AutoCAD method of positioning that lower arc instead of faffing about finding its centre point as in the pic above?

[CAD_Spider]

look at the smaller circle.... of radius ?.....

 

now what do you get if you subtract the biggest circle from it's inner circle?

 

12.5 ... but ...

 

Imagine those construction circles weren't there!

 

..... what tells you to create a construction circle of 27.5? Also, what tells you to put the other construction circle on the RHS tip of the horizontal line?

 

[CAD_Spider]

DB - is there an AutoCAD method of positioning that lower arc instead of faffing about finding its centre point as in the pic above?

 

Yep, that would be great

[CAD_Spider]

I was told to use this method by the tutor. I would love to know an alternative method!

[dbroada]

possibly a CIRCLE using the TTR (tangent, tangent, radius) option?

 

CAD_Spider - you'll have to look that one up. Strix and me aren't sitting at AutoCAD computers right now.

[Strix]

12.5 ... but ...

 

Imagine those construction circles weren't there!

 

..... what tells you to create a construction circle of 27.5? Also, what tells you to put the other construction circle on the RHS tip of the horizontal line?

 

it's the smaller circle you're drawing that's dictating those figures Spider :wink:

 

what are the construction lines doing for you?

 

DB - I was thinking ARC may be easier to place than a CIRCLE - Start:tangent, endpoint:endpoint, radius ? no? (with no messy construction lines at all)

[dbroada]

remember I'm an old fasioned draughtsman so don't do everything "the modern way". I would...

 

draw my large circle.

put a horizontal XLINE through its centre.

move the xline 30 down.

put a vertical xline through the centre

move the xline 8,5 right

draw the 2 circles you have got.

copy my horizontal xline 44 up.

trim away excess

mirror

 

in other words, much as you have done.

It may be possible to using tracking (or SNAP ) to skip certain steps.

[dbroada]

DB - I was thinking ARC may be easier to place than a CIRCLE - Start:tangent, endpoint:endpoint, radius ? no? (with no messy construction lines at all)

probably - don't use arc very often - don't do curves very often either.

[lpseifert]

Try this

Project const lines up from the end of the 017 dimension to the 15R circle;

draw an arc Start, End, Radius from the intersection of the circle and the const line to the 017 line with a radius of 12.5

[CAD_Spider]

it's the smaller circle you're drawing that's dictating those figures Spider :wink:

 

what are the construction lines doing for you?

 

Ok, thanks

[Strix]

I'd have done the large circle, drawn the full horizontal line from its centre, shoved it back using MOVE and a MID and CENTRE OSNAP, then moved it down with a MOVE/drag/distance entry... then I've have scratched my head a bit, and looked at all the options for drawing an ARC, and if that was stroppy I'd have been searching the net for the method in the OP

 

If there isn't a suitable ARC command I'd have bunged one in with the tangent, then seen if I could fix its radius in the properties or something else that's equally messy and time consuming

 

There's a terribly efficient method of drawing the line where you want it in the first place, but I have no idea how to do that

 

BTW Spider, both me and DB do electrical schematic draughting so we've both got an excuse for not doing 'proper' drawings :wink:

[CAD_Spider]

Try this

Project const lines up from the end of the 017 dimension to the 15R circle;

draw an arc Start, End, Radius from the intersection of the circle and the const line to the 017 line with a radius of 12.5

 

Ok, I'll give that a go later! Thanks

[CAD_Spider]

remember I'm an old fasioned draughtsman so don't do everything "the modern way". I would...

 

draw my large circle.

put a horizontal XLINE through its centre.

move the xline 30 down.

put a vertical xline through the centre

move the xline 8,5 right

draw the 2 circles you have got.

copy my horizontal xline 44 up.

trim away excess

mirror

 

in other words, much as you have done.

It may be possible to using tracking (or SNAP ) to skip certain steps.

 

I'll have a go at this later