A hard part of a drawing

[Gökhan Gök]

 

I couldn't draw the highlighted part of this drawing. Can anybody help?

 

 

 

 

 

 

Edited December 20, 2021 by Gökhan Gök
Edit

[Dadgad]

Welcome to CadTutor Gokhan Gok.  

I would suggest that you start by drawing the Radius 4 circle, for which the center location is defined, and then work back towards

the part which you have already done.

You will be relying on your TANGENT snap a lot, and I would probably just create circles first, and once

I felt comfortable about them, I would use the TRIM command (with the ALL option) to delete any arcs which you don't want.

Once finished and after rechecking I would use the PEDIT command to join them. 

[f700es]

Got me as well, this is as far as I got....

 

[eldon]

I think that the Ø4 dimension might mean a minimum dimension there, so there are two R10 arcs with a small straight between the two arcs of just under 0.5.

 

Will have a go at drawing it later.

[eldon]

Something like this

 

 

[SLW210]

My attempt

[CyberAngel]

Try drawing one side of the shape, you can mirror it when it's done. Have you ever used the TTR option for drawing circles?

[steven-g]

I think these are the important measurements to construct that part.

[eldon]

After drawing the R4 circle and a couple of offsets from the centre line, I drew three circles using the option TTR, trimmed, mirrored the three arcs and the straight line, and then trimmed the 4R circle - job done.

 

I think the Ø4 refers to the diameter parallel to the centre line, although why that could not be shown similar to the outside limit of 12 remains with the exercise setter!

[eldon]

I have just realised that when one uses the TTR option for drawing a circle, you do not have to activate the Tangent snap, the command does it for you.

[lrm]

The OP also posted the same question here.

 

It is surprising to see the variety of solutions yielding slightly different shapes that have been offered by experienced user.  It's clearly not a well dimensioned drawing!

 

 

[eldon]

i think this exercise was conceived to problem solve. There was a deliberate anomaly in the given dimensions, and full marks to whoever produced an "acceptable" solution. But zero marks if the solution was sought on Forums!!

[vuxvix]

Reup

Ps:Looks like the litle is wrong. There is no arc tangent to 2 arcs R10 and R4 intersecting the line 6mm from the center.

Edited December 22, 2021 by vuxvix

[SLW210]

Probably the result of rounding errors IMO.

[eldon]

It irks me when an apparently simple drawing exercise should prove not straight forward.

 

After much pondering, I think the dimension of 12 is the red herring and does not add to the information necessary to draw the figure.

 

 

[lrm]

Here's my interpretation.

Note the small gap between the R10 and R22 arcs.  I added a line tangent to the two arc to complete the profile. 

With no decimal places on most dimensions the gap of 0.24 could assumed to be 0 with roundoff.

 

[nukecad]

I'd approach this old school and draw it out as we would have done with pencil and paper.

 

That part of the drawing seems to me to be double-dimensioned, (or over dimensioned if you prefer) which is always bad practice. As this thread shows because that double-dimensioning is throwing things into doubt.
In my opinion the dia 4 should be marked 'ref', so I'm not using it in the construction.
Instead I'm assuming that all the arcs are tangential.
I admit that I could be wrong in that assumption though, and there may be a small straight section between the R22 and R10.
(Or alternatively the R22 and R4 may not meet at a true tangent).

 

Start with the R4 and the R12.5 the centres of which are given.

 

The R22's are tangental to the R4 so from that centre draw a construction circle with R18 (22-4). The centre of the R22 will lie on that circle.
Next draw a construction line parallel to the centre line and offset either side by 16 (22-12/2), Where they cross the R18 circle is the centre point of the R22 so you can now draw those in.

 

The R10 is tangental to the R22 so from the centre of the R22 draw a construction circle of R32 (22+10). The centre of the R10 lies on that construction circle.
The R10 is also tangential to the R12.5 so draw another construction circle from the centre of the R12.5 with R22.5 (12.5+10).
Where the two construction circles intersect is the centre of the R10 so you can now draw those in.

 

Hopefully that should automatically give you something like dia 4 between the two R10's.
I haven't drawn it out to check (don't have cad on this laptop) but it's probably not exactly dia 4 - because it's double-dimensioned.

Edited December 24, 2021 by nukecad

[eldon]

If one magnifies the given sketch, the "12" dimension is not at the apex of the curve and is therefore not tangential to the R22 arc. However everybody's eyes are different!!

 

 

[nukecad]

18 hours ago, eldon said:

If one magnifies the given sketch,

Always a dodgy thing to do, magnifying an image and scaling from it.
(Especially an image that is probably a scan from a printed book in the first place).

 

We've all done it of course, in a pinch it's sometimes the best you can do.

 

You find that depending on which dimension you use to magnify (and on how thick the lines are) other given dimensions will not be correct once scaled.
You will most often see that difference in Horizontal vs Vertical dimensions, which of course also throws out anything angled.

 

TBH that's a pretty old looking drawing/part anyway. Which is why I used old school construction in my post above.
A modern equivalent would not have a cast handle like that, there would be a (tapped) hole to take a plastic handle.

Edited December 25, 2021 by nukecad

[eldon]

6 hours ago, nukecad said:

Always a dodgy thing to do, magnifying an image and scaling from it.
.......

 

I really think you should confine yourself to denigrating my thoughts until AFTER you have tried drawing it.

 

I have many years experience in using unequal scaling mapping. Both Northing and Easting gridlines shown, and yet unequal. I believe the early photo-copiers were not very particular in preserving equal x and y scaling.

 

In this instance, I have NOT relied on scaling, rather I am using the parallelity of lines where the unequal x/y scaling has equal effects at both ends of the lines.

 

I took a copy of the posted image, drew a line along the centre line and copied that line to the appropriate place, which to my eye showed the 12 dimension, whilst being a valid dimension, was not an appropriate dimension to constructing the shape.

 

I would welcome your comments after you have tried drawing my method. I have been using "old school construction" for 60 years.

Edited December 25, 2021 by eldon
corrected number of years