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I haven't done it on 35 years, but at least your equations look familiar.
I find that comforting.
If the capability is questionable, would solid wood blocks of a suitable
height to support the channel somewhere near the center help?
On Fri, Jul 2, 2021, 06:34 Donald H Locker <dhlocker@comcast.net> wrote:
> First oops - I used 10ft length, not 8ft. At 8ft, the numbers look
> better by about 20%
>
> Donald.
> --
> *Plain Text* email -- it's an accessibility issue
> () no proprietary attachments; no html mail
> /\ <https://www.georgedillon.com/web/html_email_is_evil.shtml>
>
> On 2021-07-02 6:16 a.m., Donald H Locker wrote:
> > BIG NOTE: please check my calculations and assumptions; I haven't
> > actually done any of this for nearly 40 years.
> >
> > TLDR: They might not work.
> >
> > The significant supporting bits are the two flanges (3in x 0.5in); the
> > plate across the top adds very little strength.
> >
> > All calculations below in pounds and inches.
> >
> > The maximum stress on the webs (if the weight is perfectly divided
> > between them; more on that later) will be (equation 1-1 in reference 1)
> > with the weight at the center of the ramp. Fb (bending stress in the
> > flange of the channel) must be less than the yield stress of the channe=
l
> > material.
> >
> > Fb =3D M*c/I
> >
> > [Ref 2] M for each web: PL/8 =3D P*120in/8 =3D P*15in [P is point load,=
lb]
> > [email] c for each web: 1.5in
> > [Ref 4] I for each web: (b*(h^3))/12 =3D ((0.5in)*(3in)^3)/12 =3D 1.125=
in^4
> >
> > Fb =3D (P*15in*1.5in)/1.125in^4 =3D P*20 lb/in^2
> >
> > For the given situation, p=3D3840lb, so Fb (max) is 3840*20 =3D 76800lb=
/in^2
> > distributed between the two channels, each with two flanges. Since Fb
> > must be less than the material yield stress, 10000 psi for some kind of
> > structural Al, but not high-strength material [Ref 3], this doesn't loo=
k
> > very good. Each flange would be loaded to about 19200lb/in^2 if all
> > loads were perfectly distributed. (Note that high-strength Al (e.g.
> > 6061) can have a yield stress of 45000lb/in^2 so looks much more likely
> > to succeed, but I don't know how much I'd trust that.)
> >
> > My biggest concerns would be the division of stresses between flanges
> > (if one channel tilts a little or is not sitting perfectly flat on the
> > trailer or ground, stress sharing will be uneven and one flange make
> > take all stress) and the potential for flange instability (see notes in
> > 1.3.1.5 in Ref 1.) This may not be a problem because the flanges are no=
t
> > particularly deep, but I watched a boat hung from I-beams drop when a
> > structural I-beam twisted slightly from imperfect loading and the entir=
e
> > structure quickly twisted into a totally unsupportive mess.
> >
> > References:
> > 1 Beam stress/strain:
> > <
> https://engineeringlibrary.org/reference/simple-beam-bending-air-force-st=
ress-manual
> >
> >
> > 2 Beam force/reaction:
> > <
> https://engineeringlibrary.org/reference/beam-forces-moments-air-force-st=
ress-manual
> >
> >
> > 3 Material properties:
> > <https://www.engineeringtoolbox.com/properties-aluminum-pipe-d_1340.htm=
l
> >
> >
> > 4 Area moments:
> > <https://www.engineeringtoolbox.com/area-moment-inertia-d_1328.html>
> >
> > ATB,
> > Donald.
> > --
> > *Plain Text* email -- it's an accessibility issue
> > () no proprietary attachments; no html mail
> > /\ <https://www.georgedillon.com/web/html_email_is_evil.shtml>
> >
> > On 2021-07-01 10:56 p.m., john niolon wrote:
> >> I'm thinking about using aluminum channel for a set of ramps for my ca=
r
> >> hauler. I have some 'available' that is 10" wide with .50 web
> >> thickness and almost 3" flange... about 15# per ft.
> >>
> >> ramps will be 7-8' long =E2=80=A6.. and will go from ground to 17" hi=
gh trailer
> >> deck... truck weight is 5300 +/- =E2=80=A6 with front end weighting 3=
840. I
> >> can't find a table telling me weight capacity of
> >> channel with the load traveling up the wide web... like this any
> >> ideas on capacity ??
> >>
> >> Image87ABA31D
> >>
> >> thanks
> >> john
> >>
> >>
> >>
> >> _______________________________________________
> >>
> >> Shop-talk@autox.team.net
> >> Donate: http://www.team.net/donate.html
> >> Suggested annual donation $12.96
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> http://autox.team.net/archive
> >>
> >> Unsubscribe/Manage:
> http://autox.team.net/mailman/options/shop-talk/dhlocker@comcast.net
> >>
> _______________________________________________
>
> Shop-talk@autox.team.net
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> Suggested annual donation $12.96
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<div dir=3D"auto">I haven't done it on 35 years, but at least your equa=
tions look familiar.=C2=A0 I find that comforting.<div dir=3D"auto"><br></d=
iv><div dir=3D"auto">If the capability is questionable, would solid wood bl=
ocks of a suitable height to support the channel somewhere near the center =
help?</div></div><br><div class=3D"gmail_quote"><div dir=3D"ltr" class=3D"g=
mail_attr">On Fri, Jul 2, 2021, 06:34 Donald H Locker <<a href=3D"mailto=
:dhlocker@comcast.net">dhlocker@comcast.net</a>> wrote:<br></div><blockq=
uote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1px #ccc =
solid;padding-left:1ex">First oops - I used 10ft length, not 8ft. At 8ft, t=
he numbers look<br>
better by about 20%<br>
<br>
Donald.<br>
--<br>
*Plain Text* email -- it's an accessibility issue<br>
() no proprietary attachments; no html mail<br>
/\ <<a href=3D"https://www.georgedillon.com/web/html_email_is_evil.shtml=
" rel=3D"noreferrer noreferrer" target=3D"_blank">https://www.georgedillon.=
com/web/html_email_is_evil.shtml</a>><br>
<br>
On 2021-07-02 6:16 a.m., Donald H Locker wrote:<br>
> BIG NOTE: please check my calculations and assumptions; I haven't<=
br>
> actually done any of this for nearly 40 years.<br>
> <br>
> TLDR: They might not work.<br>
> <br>
> The significant supporting bits are the two flanges (3in x 0.5in); the=
<br>
> plate across the top adds very little strength.<br>
> <br>
> All calculations below in pounds and inches.<br>
> <br>
> The maximum stress on the webs (if the weight is perfectly divided<br>
> between them; more on that later) will be (equation 1-1 in reference 1=
)<br>
> with the weight at the center of the ramp. Fb (bending stress in the<b=
r>
> flange of the channel) must be less than the yield stress of the chann=
el<br>
> material.<br>
> <br>
>=C2=A0 =C2=A0Fb =3D M*c/I<br>
> <br>
> [Ref 2] M for each web: PL/8 =3D P*120in/8 =3D P*15in [P is point load=
, lb]<br>
> [email] c for each web: 1.5in<br>
> [Ref 4] I for each web: (b*(h^3))/12 =3D ((0.5in)*(3in)^3)/12 =3D 1.12=
5in^4<br>
> <br>
>=C2=A0 =C2=A0Fb =3D (P*15in*1.5in)/1.125in^4 =3D P*20 lb/in^2<br>
> <br>
> For the given situation, p=3D3840lb, so Fb (max) is 3840*20 =3D 76800l=
b/in^2<br>
> distributed between the two channels, each with two flanges. Since Fb<=
br>
> must be less than the material yield stress, 10000 psi for some kind o=
f<br>
> structural Al, but not high-strength material [Ref 3], this doesn'=
t look<br>
> very good. Each flange would be loaded to about 19200lb/in^2 if all<br=
>
> loads were perfectly distributed. (Note that high-strength Al (e.g.<br=
>
> 6061) can have a yield stress of 45000lb/in^2 so looks much more likel=
y<br>
> to succeed, but I don't know how much I'd trust that.)<br>
> <br>
> My biggest concerns would be the division of stresses between flanges<=
br>
> (if one channel tilts a little or is not sitting perfectly flat on the=
<br>
> trailer or ground, stress sharing will be uneven and one flange make<b=
r>
> take all stress) and the potential for flange instability (see notes i=
n<br>
> 1.3.1.5 in Ref 1.) This may not be a problem because the flanges are n=
ot<br>
> particularly deep, but I watched a boat hung from I-beams drop when a<=
br>
> structural I-beam twisted slightly from imperfect loading and the enti=
re<br>
> structure quickly twisted into a totally unsupportive mess.<br>
> <br>
> References:<br>
> 1 Beam stress/strain:<br>
> <<a href=3D"https://engineeringlibrary.org/reference/simple-beam-be=
nding-air-force-stress-manual" rel=3D"noreferrer noreferrer" target=3D"_bla=
nk">https://engineeringlibrary.org/reference/simple-beam-bending-air-force-=
stress-manual</a>><br>
> <br>
> 2 Beam force/reaction:<br>
> <<a href=3D"https://engineeringlibrary.org/reference/beam-forces-mo=
ments-air-force-stress-manual" rel=3D"noreferrer noreferrer" target=3D"_bla=
nk">https://engineeringlibrary.org/reference/beam-forces-moments-air-force-=
stress-manual</a>><br>
> <br>
> 3 Material properties:<br>
> <<a href=3D"https://www.engineeringtoolbox.com/properties-aluminum-=
pipe-d_1340.html" rel=3D"noreferrer noreferrer" target=3D"_blank">https://w=
ww.engineeringtoolbox.com/properties-aluminum-pipe-d_1340.html</a>><br>
> <br>
> 4 Area moments:<br>
> <<a href=3D"https://www.engineeringtoolbox.com/area-moment-inertia-=
d_1328.html" rel=3D"noreferrer noreferrer" target=3D"_blank">https://www.en=
gineeringtoolbox.com/area-moment-inertia-d_1328.html</a>><br>
> <br>
> ATB,<br>
> Donald.<br>
> --<br>
> *Plain Text* email -- it's an accessibility issue<br>
> () no proprietary attachments; no html mail<br>
> /\ <<a href=3D"https://www.georgedillon.com/web/html_email_is_evil.=
shtml" rel=3D"noreferrer noreferrer" target=3D"_blank">https://www.georgedi=
llon.com/web/html_email_is_evil.shtml</a>><br>
> <br>
> On 2021-07-01 10:56 p.m., john niolon wrote:<br>
>> I'm thinking about using aluminum channel for a set of ramps f=
or my car<br>
>> hauler.=C2=A0 I have some 'available' that is=C2=A0 10&quo=
t; wide with .50 web<br>
>> thickness and almost 3" flange... about 15# per ft.<br>
>> =C2=A0<br>
>> ramps will be 7-8' long =E2=80=A6..=C2=A0 and will go from gro=
und to 17" high trailer<br>
>> deck...=C2=A0 truck weight is 5300 +/- =E2=80=A6 with front end we=
ighting 3840.=C2=A0=C2=A0 I<br>
>> can't find a table telling me weight capacity of<br>
>> channel with the load traveling up the wide web...=C2=A0=C2=A0 lik=
e this=C2=A0=C2=A0 any<br>
>> ideas on capacity ??<br>
>> =C2=A0<br>
>> Image87ABA31D<br>
>> =C2=A0<br>
>> thanks<br>
>> john<br>
>> =C2=A0<br>
>> =C2=A0<br>
>><br>
>> _______________________________________________<br>
>><br>
>> <a href=3D"mailto:Shop-talk@autox.team.net"; target=3D"_blank" rel=
=3D"noreferrer">Shop-talk@autox.team.net</a><br>
>> Donate: <a href=3D"http://www.team.net/donate.html"; rel=3D"norefer=
rer noreferrer" target=3D"_blank">http://www.team.net/donate.html</a><br>
>> Suggested annual donation=C2=A0 $12.96<br>
>> Archive: <a href=3D"http://www.team.net/pipermail/shop-talk"; rel=
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>><br>
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t</a><br>
>><br>
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