building a small ramp, 1/2" plywood topped. pretty simple one. four
feet long, four inches rise over four feet (I'll 'knife point rip' the
shallow end/bottom of the plywood where it meets the floor). the big
question is: what angle, in degrees or, better yet, 'degrees and parts
of a degree' is a taper of one inch per foot?
add'l info/clarification: finished dimensions, _side_ of ramp: right
triangle, four inches tall by four feet long at base (where it sits on
garage floor its entire length)
I'll need this same info (angle in degrees) to set the rip angle at
the top of the 2 x 4 ripped 'underneath crossbars' I make for it....at
intermediate positions. (ps-I couldn't find any formulas or
calaculators or 'tips' in google for figuring this out...)
I'm gonna guess: if it's 6 in 12 pitch, it's 45 degrees, right? so if
it's 3 in 12, it must be half that, or 22.5 degrees, right? assuming I
got 3 in 12 right, then 1 in 12 pitch must be a third of that, or 7
1/2 degrees, do I have that right?
thanks much :-)
bill yohler wrote:
>
> building a small ramp, 1/2" plywood topped. pretty simple one. four
> feet long, four inches rise over four feet (I'll 'knife point rip' the
> shallow end/bottom of the plywood where it meets the floor). the big
> question is: what angle, in degrees or, better yet, 'degrees and parts
> of a degree' is a taper of one inch per foot?
>
> add'l info/clarification: finished dimensions, _side_ of ramp: right
> triangle, four inches tall by four feet long at base (where it sits on
> garage floor its entire length)
>
> I'll need this same info (angle in degrees) to set the rip angle at
> the top of the 2 x 4 ripped 'underneath crossbars' I make for it....at
> intermediate positions. (ps-I couldn't find any formulas or
> calaculators or 'tips' in google for figuring this out...)
>
For one inch rise per foot, the tangent value is 1/12 = 0.0833
The angle whose tanget is 0.0833 (ArcTanget(0.08333) is 0.0831 RADIANS
There are 2 Pi RADIANS in a circle which is 360 degrees, so there are
57.3 degrees per radian (ok so it's 57.295779513 but 57.3 is close
enough)
0.0831 Radians X 57.3 degrees/Radian = 4.76 degrees. 5 degrees would
probably be close enough.
> I'm gonna guess: if it's 6 in 12 pitch, it's 45 degrees, right? so if
> it's 3 in 12, it must be half that, or 22.5 degrees, right? assuming I
> got 3 in 12 right, then 1 in 12 pitch must be a third of that, or 7
> 1/2 degrees, do I have that right?
Nope. For 45 degrees, the rise must equal the run or 12 inch fise for
a 12 inch run.
But a 6:12 is not 22 1/2 degrees. half of the 12:12's 45 degrees,
but is 26.565 degrees
and a 3:12 is 14.0362 degrees not one quarter of 12:12's 45 degrees
or 11.25 degrees. Tangent to degrees isn't a linear relationship.
>
> thanks much :-)
you're welcome
/ \
< o o >
V
/-\
\___/
Reyd Dorakeen wrote:
>
> A^2+b^2=C^2 A=bottom, or 12
> 12^2+1^2=c^2 B= side, or 1
> 12^2+1^2=145^2 C= slopeing part
> C=12.04159
> 12/12.04159=(cos a)
> cos a= 0.99654
> cos^-1 0.99654=4.76
> A=4.76
> CHECK:
> tan a=1/12 _
> tan a= 0.083
> tan-1 0.08333= a
> a = 4.76
> somebody correct me if I'm wrong
> but I think its 4.76 degrees at the bottom (where it starts to rise)
> and 85.236 at the top(between the right angle of the end and the top of the
> rise)
> No guarantees, but I had to find some actual use for the last week of math
> hell:-/
>
Yup, and it's nice to get confirmation your calcs were right.
charlie b
On 10 Jan 2004 09:16:03 -0800, [email protected] (bill yohler) wrote:
>the big
>question is: what angle, in degrees or, better yet, 'degrees and parts
>of a degree' is a taper of one inch per foot?
>then 1 in 12 pitch must be a third of that, or 7
>1/2 degrees, do I have that right?
Near enough. It's actually 5°, because you're describing an angular
ratio, where we really want a linear ratio:
tan(angle) = 1/12
Strictly it depends on whether "1 in 12" is a rise of 1 in a
horizontal distance of 12, or a slant distance of 12. But the
difference at this shallow angle is only 4.76 or 4.78 degrees.
--
Smert' spamionam
A^2+b^2=C^2 A=bottom, or 12
12^2+1^2=c^2 B= side, or 1
12^2+1^2=145^2 C= slopeing part
C=12.04159
12/12.04159=(cos a)
cos a= 0.99654
cos^-1 0.99654=4.76
A=4.76
CHECK:
tan a=1/12 _
tan a= 0.083
tan-1 0.08333= a
a = 4.76
somebody correct me if I'm wrong
but I think its 4.76 degrees at the bottom (where it starts to rise)
and 85.236 at the top(between the right angle of the end and the top of the
rise)
No guarantees, but I had to find some actual use for the last week of math
hell:-/
in article [email protected], JAW at
[email protected] wrote on 1/11/04 7:00 AM:
> You have a 1" rise per foot, that mean you have a 1:12 slope. Use any
> scale (let's use pez containers), so you have 12 pez containers along
> the 2/4 and 1 pez container perpenduicular to that. Strike a line from
> the end of the board to the top of the perpendicular pez container.
>
> (or use the scale provided here)
>
> |-----|-----|-----|-----|-----|-----|-----|-----|-----|-----|-----|-----|
>
> |-----| = 1 pez.
>
> The lesson hare is that you do not need the angle, or you do not need to
> use math.
>
>
>
> bill yohler wrote:
>> building a small ramp, 1/2" plywood topped. pretty simple one. four
>> feet long, four inches rise over four feet (I'll 'knife point rip' the
>> shallow end/bottom of the plywood where it meets the floor). the big
>> question is: what angle, in degrees or, better yet, 'degrees and parts
>> of a degree' is a taper of one inch per foot?
>>
>> add'l info/clarification: finished dimensions, _side_ of ramp: right
>> triangle, four inches tall by four feet long at base (where it sits on
>> garage floor its entire length)
>>
>> I'll need this same info (angle in degrees) to set the rip angle at
>> the top of the 2 x 4 ripped 'underneath crossbars' I make for it....at
>> intermediate positions. (ps-I couldn't find any formulas or
>> calaculators or 'tips' in google for figuring this out...)
>>
>> I'm gonna guess: if it's 6 in 12 pitch, it's 45 degrees, right? so if
>> it's 3 in 12, it must be half that, or 22.5 degrees, right? assuming I
>> got 3 in 12 right, then 1 in 12 pitch must be a third of that, or 7
>> 1/2 degrees, do I have that right?
>>
>> thanks much :-)
>
thanks much to ALL you guys: doug andy AND charlie :-)
I'm _sure_ glad I posted that inquiry now :-) - turns out my
'guesstimates' on how to convert the two were what I'd call 'way
foggy'. I especially appreciate the 'windows calculator' method reply
(which I had no idea was even 'lurking within' windows :-)
gonna go with that 4.76 degrees/wow, cool, and thanks AGAIN :-)
In article <[email protected]>, [email protected] (bill yohler) wrote:
>thanks much to ALL you guys: doug andy AND charlie :-)
>
>I'm _sure_ glad I posted that inquiry now :-) - turns out my
>'guesstimates' on how to convert the two were what I'd call 'way
>foggy'. I especially appreciate the 'windows calculator' method reply
>(which I had no idea was even 'lurking within' windows :-)
>
>gonna go with that 4.76 degrees/wow, cool, and thanks AGAIN :-)
You're welcome, glad to help -- and thank YOU for the followup. Too many guys
pop in with a question, get the answer, and are never heard from again.
--
Doug Miller (alphageek at milmac dot com)
How come we choose from just two people to run for president and 50 for Miss America?
You have a 1" rise per foot, that mean you have a 1:12 slope. Use any
scale (let's use pez containers), so you have 12 pez containers along
the 2/4 and 1 pez container perpenduicular to that. Strike a line from
the end of the board to the top of the perpendicular pez container.
(or use the scale provided here)
|-----|-----|-----|-----|-----|-----|-----|-----|-----|-----|-----|-----|
|-----| = 1 pez.
The lesson hare is that you do not need the angle, or you do not need to
use math.
bill yohler wrote:
> building a small ramp, 1/2" plywood topped. pretty simple one. four
> feet long, four inches rise over four feet (I'll 'knife point rip' the
> shallow end/bottom of the plywood where it meets the floor). the big
> question is: what angle, in degrees or, better yet, 'degrees and parts
> of a degree' is a taper of one inch per foot?
>
> add'l info/clarification: finished dimensions, _side_ of ramp: right
> triangle, four inches tall by four feet long at base (where it sits on
> garage floor its entire length)
>
> I'll need this same info (angle in degrees) to set the rip angle at
> the top of the 2 x 4 ripped 'underneath crossbars' I make for it....at
> intermediate positions. (ps-I couldn't find any formulas or
> calaculators or 'tips' in google for figuring this out...)
>
> I'm gonna guess: if it's 6 in 12 pitch, it's 45 degrees, right? so if
> it's 3 in 12, it must be half that, or 22.5 degrees, right? assuming I
> got 3 in 12 right, then 1 in 12 pitch must be a third of that, or 7
> 1/2 degrees, do I have that right?
>
> thanks much :-)
In article <[email protected]>, [email protected] (bill yohler) wrote:
>building a small ramp, 1/2" plywood topped. pretty simple one. four
>feet long, four inches rise over four feet (I'll 'knife point rip' the
>shallow end/bottom of the plywood where it meets the floor). the big
>question is: what angle, in degrees or, better yet, 'degrees and parts
>of a degree' is a taper of one inch per foot?
>
[snip]
>I'm gonna guess: if it's 6 in 12 pitch, it's 45 degrees, right?
Nope, actually 6-in-12 is about 26.5 degrees; 45 degrees is 12-in-12.
>so if
>it's 3 in 12, it must be half that, or 22.5 degrees, right? assuming I
>got 3 in 12 right, then 1 in 12 pitch must be a third of that, or 7
>1/2 degrees, do I have that right?
>
No, sorry, that's not right, and it's not that simple. A little bit of
trigonometry is needed here; the angle is the inverse tangent of the ratio
of the vertical distance to the horizontal distance (rise divided by run).
If you're using a Windows computer, you can use the Windows' built-in
Calculator program (click Start | Programs | Accessories | Calculator) to
figure out the angles.
1. Click View on the menu bar, then select Scientific.
2. Make sure that "Dec" and "Degrees" are selected.
3. Enter the inches, click the "divided by" ( / ) key, enter the feet, click
the equals sign.
4. Checkmark the "Inv" box at the left side of the window, and click the
button labelled "tan". This gives you the angle in degrees.
You should get 4.76 degrees.
--
Doug Miller (alphageek at milmac dot com)
How come we choose from just two people to run for president and 50 for Miss America?