maths expert required

[sunnybob]

ok, I have a numbers puzzle on my latest project.

Regardless of reasons (long story), I want to build a drawer unit onto a compound sloping floor.

This isnt an elegant piece of furniture, its for my workshop. I am using 12 mm ply for the two sides, but heres where its hurting my brain.

Imagine a square box 850 mm wide, x 900 mm high x 600 mm deep, with the four corners as if there were legs.

Because of the slope, the front left corner is the lowest point, the rear right is the highest, but its not a consistent slope.

So, using a metre spirit level and pieces of wood as spacers at the corners, I have arrived at the following numbers.
Starting at the rear right (highest point) and going to front right, theres a 14 mm drop.
Going from front right to front left, the drop (from the start point) increases to 37 mm.
going from front left to rear left, the drop (from the starting point)rises slightly to 27 mm.
Obviously, rear left to rear right is an uphill 27 mm.

I have two pieces of plywood 900mm x 600mm for the sides. The 900 is the height. (still with me?)

So, if the front left is the lowest point, that height will be 900mm.
Heres the question....

how much do I have to cut the other three edges to, to make a vertical sided and flat topped box?

 

[Jacob]

I can't see what the problem is - you've got all the dimension corrections haven't you?

 

[Billy Flitch]

No need for maths Bob build the cab set in place wedge up till its plumb, set a compass to the widest point then scribe it in cut it and then put it back in place.

 

[sunnybob]

I can't see what the problem is - you've got all the dimension corrections haven't you?

well yes, I have all the dimensions, I also have worked out the cutting length 4 times and got three different answers.
i was hoping someone (a maths expert or similar) would give me the lengths of each side so i could confirm I finally have the right answer.
I'm ok at adding up, but always struggled with multiple facets.

 

[sunnybob]

No need for maths Bob build the cab set in place wedge up till its plumb, set a compass to the widest point then scribe it in cut it and then put it back in place.

The thing is, i'm tyrying to keep the lower drawer as low to the ground as i can and still have it level. Also I dont want to lose any more than I absolutely have to from the 900mm height.

 

[dc_ni]

Cant you put it into sketchup?

 

[sunnybob]

Cant you put it into sketchup?

Well (hanging my head in shame), thats something else my worn out old brain cant work out. #-o #-o

 

[Billy Flitch]

Bob keep it simple the height you want is 900m/m the biggest difference is 37 m/m make the whole cab 937m/m tall then scribe it in place and cut, end of job.

 

[Jacob]

Obviously, rear left to rear right is an uphill 27 mm.
.....

Seems to be wrong. 14 + 37 - 27 = 24
Front left = 900
Rear left 900-27=873
front right 900-37=863
rear right 863-14=849

 

[sunnybob]

Bob keep it simple the height you want is 900m/m the biggest difference is 37 m/m make the whole cab 937m/m tall then scribe it in place and cut, end of job.

cant do that, the 900 x 600 is already cut.

 

[sunnybob]

Obviously, rear left to rear right is an uphill 27 mm.
.....

Seems to be wrong. 14 + 37 - 27 = 24
Front left = 900
Rear left 900-27=873
front right 900-37=863
rear right 863-14=849

you know what? apart from the front left 900, every one of those measurement are different to my answers.
I just cant get it right in my head.

I make the left panel heights as 900 front, and 890 rear
and the right panel heights as 887 front and 873 rear.

See why I asked for help?
I think I should have asked for a surveyor rather than a mathematician

 

[Terry - Somerset]

This seems simple to me if you look at is as a variation from the lowest point, not the highest. The lowest point can be 900mm - all other corners are cut down from this.

Take the sheet to be used for the left hand side. The left front is the lowest point and can be 900mm. The rear left is 10mm higher than this so trim a triangle off the bottom edge to leave the front 900mm and the back 890mm.

Take the sheet for the right hand side. Mark a point 23mm up from the bottom at the front and 37mm up from the bottom at the back. Cut.

This should get the corners correct but if the floor is not planar(??) it may still wobble if it catches the ground part way along an edge. Small feet on each corner may be sensible.

Or have I completely missed the point??

Terry

 

[Jacob]

....
Take the sheet to be used for the left hand side. The left front is the lowest point and can be 900mm. The rear left is 10mm higher than this so trim a triangle off the bottom edge to leave the front 900mm and the back 890mm.......

Or have I completely missed the point??

Terry

No you've just completely got it wrong! The rear left is 27 higher than front left (according to OP)

though on second reading "going from front left to rear left, the drop (from the starting point)rises slightly to 27 mm is ambiguous - which is "starting point"? front left or rear right? If "rear right" you are going from rear right to rear left, not as above.
I'm confused now!

 

[sunnybob]

This seems simple to me if you look at is as a variation from the lowest point, not the highest. The lowest point can be 900mm - all other corners are cut down from this.

Take the sheet to be used for the left hand side. The left front is the lowest point and can be 900mm. The rear left is 10mm higher than this so trim a triangle off the bottom edge to leave the front 900mm and the back 890mm.

Take the sheet for the right hand side. Mark a point 23mm up from the bottom at the front and 37mm up from the bottom at the back. Cut.

This should get the corners correct but if the floor is not planar(??) it may still wobble if it catches the ground part way along an edge. Small feet on each corner may be sensible.

Or have I completely missed the point??

Terry

Terry, my numbers match your numbers =D> =D>

Must be because we must have been very near neighbours at one time. We lived in Taunton for over 30 years before moving to cyprus in 2008. What part are you in?

The floor is a mess, hand poured and stamped concrete. I'm actually considering shuttering the area of this cupboard and pouring concrete to get it level.

 

[sunnybob]

....
Take the sheet to be used for the left hand side. The left front is the lowest point and can be 900mm. The rear left is 10mm higher than this so trim a triangle off the bottom edge to leave the front 900mm and the back 890mm.......

Or have I completely missed the point??

Terry

No you've just completely got it wrong! The rear left is 27 higher than front left (according to OP)

though on second reading "going from front left to rear left, the drop (from the starting point)rises slightly to 27 mm is ambiguous - which is "starting point"? front left or rear right? If "rear right" you are going from rear right to rear left, not as above.
I'm confused now!

the numbers go clockwise, starting at the highest point (rear right) then front right, front left, front rear, back to the starting point. All measured in relation to the rear right (highest point).

 

[Jacob]

....
Take the sheet to be used for the left hand side. The left front is the lowest point and can be 900mm. The rear left is 10mm higher than this so trim a triangle off the bottom edge to leave the front 900mm and the back 890mm.......

Or have I completely missed the point??

Terry

No you've just completely got it wrong! The rear left is 27 higher than front left (according to OP)

though on second reading "going from front left to rear left, the drop (from the starting point)rises slightly to 27 mm is ambiguous - which is "starting point"? front left or rear right? If "rear right" you are going from rear right to rear left, not as above.
I'm confused now!

the numbers go clockwise, starting at the highest point (rear right) then front right, front left, front rear, back to the starting point. All measured in relation to the rear right (highest point).

Right! It's the way you set out the problem.
I now get 863, 877, 900, 890
How does that feel?

 

[scotty38]

Why don't you just make the box square and fashion yourself four odd legs from 2x2 or whatever. At least if you get them wrong you can try again but the box remains just so?

 

[sunnybob]

the numbers go clockwise, starting at the highest point (rear right) then front right, front left, front rear, back to the starting point. All measured in relation to the rear right (highest point).[/quote]Right! It's the way you set out the problem.
I now get 863, 877, 900, 890
How does that feel?[/quote]

nope, still differ on the right panel 900 and 890 for the left, but 887 and 873 for the right (subject to confirmation)

 

[sunnybob]

Why don't you just make the box square and fashion yourself four odd legs from 2x2 or whatever. At least if you get them wrong you can try again but the box remains just so?

This is a part of the "long story"
I live in Cyprus, on the edge of a village with farm land around me. I have to make every thing proof of mice, rats, chameleons, and even snakes (there are 8 varieties here and two are very dangerously poisonous). Any small or thin gap is a potential nest, thus I need it flush to the ground.

 

[Distinterior]

I agree with Jacob!

Left Front = 900
Left Rear = 890
Right Front = 877
Right Rear = 863