quick tech drawin Qs

declan_lgs

1)

How would you approach this: [1989 P1 Q7 (b)]
Find a point D on the edge AB so that the line OD shall be inclined at 60degrees to the horizontal plane.

Can-not figure that out. A cone at O doesn't give much insight. The Q isn't simplified by means of AB's true inclination being in the elevation or anything.

Any ideas?

[I wish I had a scanner, but sorry, I'm relying on someone to know the stuff to approach this]

2)

This is one more of you can relate to easily I would think. Finding the inclination of a line to a plane (one point from the line is on the plane, if it isn't, edge view the plane and continue the line, have never seen that come up). Basic enough but I'm not sure how it's done. I'm looking at 1992 (Q1 (c)) and 1995 (Q1 (c) again).

Can you basically imagine a triangle from the point of intersection, a point on the line and a point UNDER the line and on the plane - and develop it, and mark the angle?

Also, just to clarify - getting the perpendicular line from a point to a plane - edge view the plan, and in this view draw a perp line from the point to the plane, bring the new point back into plan and go parallel to the X1Y1 from the orig point to the new line and this is the line?

Oh how can you follow that. ANY input regardless will be appreciated

blue-army

I'm sorry but I can't answer your question.....(That's why I recently dropped to pass. I only got 38% in the mocks..:( )


Anyway....sorry to go off topic, but....
Do we have to line out our sheets tomorrow...ie. Title Block etc...???
and if I don't will I lose 'presentation marks'??

ZorbaTehZ

declan_lgs wrote: »

1)

How would you approach this: [1989 P1 Q7 (b)]
Find a point D on the edge AB so that the line OD shall be inclined at 60degrees to the horizontal plane.

Can-not figure that out. A cone at O doesn't give much insight. The Q isn't simplified by means of AB's true inclination being in the elevation or anything.

Any ideas?

Difficult to answer it without a diagram, can you not at least do a rough sketch in paint?
I'll assume O isn't vertically above/below A/B. Call the plane through O that is horizontal, y. Can you see where AB meets y? If so then all you need to do is join AB at the point that it intercepts y, with O. Then arbitrarily choose a point on AB, make a cone at 60deg, mark in where it intercepts your new line, then basically move the line up to O. Im sure theres some other convuluted way of using locii etc, but thats how I'd do it.

declan_lgs wrote: »

2)

This is one more of you can relate to easily I would think. Finding the inclination of a line to a plane (one point from the line is on the plane, if it isn't, edge view the plane and continue the line, have never seen that come up). Basic enough but I'm not sure how it's done. I'm looking at 1992 (Q1 (c)) and 1995 (Q1 (c) again).

Can you basically imagine a triangle from the point of intersection, a point on the line and a point UNDER the line and on the plane - and develop it, and mark the angle?

There's loads of ways to do this. Again, the way I'd do it is, first determine the true length of the line. Then look along the plane. Then compass in your length from the point, to see where it intercepts the plane. Voila, your angle.

declan_lgs wrote: »

Also, just to clarify - getting the perpendicular line from a point to a plane - edge view the plan, and in this view draw a perp line from the point to the plane, bring the new point back into plan and go parallel to the X1Y1 from the orig point to the new line and this is the line?

I'm not really following you there. You have the theory though. Basically, just bring back the point through your views, and you should have it.

ZorbaTehZ

blue-army wrote: »

I'm sorry but I can't answer your question.....(That's why I recently dropped to pass. I only got 38% in the mocks..:( )


Anyway....sorry to go off topic, but....
Do we have to line out our sheets tomorrow...ie. Title Block etc...???
and if I don't will I lose 'presentation marks'??

When you say "line our sheets" you mean put borders in? If so, then no - all you need to do is clearly write on the sheet the question. The sheets will all be stamped officially - I can't remember exactly how it was, but I think that the stamp also has space to put your exam number in. When I did it, we got the sheets way before hand (like 15 minutes) and we're allowed into the hall early to set up everything, so I wouldn't be worried about that stuff.

If you're worried about presentation marks, then make sure you spend a good 5 minutes before the test with some tissue cleaning all the lead marks off your T square, set square, protractor etc etc.

declan_lgs

think I got the 1st one at last.

Start off with the cone at O.

Then extend the plane OAB to the XY line, and draw the extended plane in plan lightly. Where it intersects the circle from the cone, line drawn from here to O is inclined at 60deg to horizontal plane, and is on the plan OAB, so draw the line from AB to O.

Sorry about the lack of a diagram, hadn't that idea last night! Here:

and my other Q, from 1992, you can get online. http://www.practicalstudent.com/subjects/td/exampapers/pages/1992hlp1q1.html Forgot that.
I know the solution is there but I never done it that way. My teacher (and he is good) always told me to create a triangle, and develop it. It seems to me that it must be a triangle that is perp to the plane and includes the line? That works, right? And you can't just take an arbitrary triangle? If you've done it this way before, you might be able to help me. Otherwise, doesn't matter so much.

thanks ZorbaTehZ !

ZorbaTehZ

declan_lgs wrote: »

think I got the 1st one at last.

Start off with the cone at O.

Then extend the plane OAB to the XY line, and draw the extended plane in plan lightly. Where it intersects the circle from the cone, line drawn from here to O is inclined at 60deg to horizontal plane, and is on the plan OAB, so draw the line from AB to O.

Ye, thats perfect.

declan_lgs wrote: »

I know the solution is there but I never done it that way. My teacher (and he is good) always told me to create a triangle, and develop it. It seems to me that it must be a triangle that is perp to the plane and includes the line? That works, right? And you can't just take an arbitrary triangle? If you've done it this way before, you might be able to help me. Otherwise, doesn't matter so much.

Yes, you can do it that way. The way I gave is quicker though :pac: