Hi,

I am not an engineer but trying to understand bolt strgth, tensile
strength og steel and some other varribles for something I am wanting
to construct. I am wanting to build a car dolly and/or dual axle
trailer. I have welders and have welded on hobby projects but by no
means consider myself an expert welder. My idea is to both weld and
bolt a square togther to form the frame. I have some 3 inch square
tubing laying around, I believe is is 1/8 thick but not sure. It came
from some material stand at work that got cut up.


My idea was to get some scrap 1/8 inch plate and torch cut two “L”
brackets and weld them togther to form a ¼ inch L bracket. These
would
go on all 4 corners of the square I would bolt each L with bolts
through the L and through the 3 inch tubing. Before doing this I
would
insert a section of black pipe through all pieces for the bolt to
ride
in. After bolting and everything being square I would weld all joints
with 6011 or 6013 rod with either my AC buzzbox or the mIller
generator welder I just aquired on DC. (Not welded with it much yet)
(I have trouble welding with 7018 for some reason.


My question becomes, what size bolts would be adequate? I get
confused
when I see specs on bolts such as shear strength, tensile strength,
yield strength, etc? I suspect the bolt need only be as strong as the
streth of the bolt steel around it. I am having trouble finding the
specs for mild steel strength but think it might be around 38,000
PSI?
Is this true?


Any help is appreciated!

On Jun 22, 5:16*pm, stryped wrote:
I am not an engineer but trying to understand bolt strgth, tensile
strength og steel and some other varribles for something I am wanting
to construct. ...
My question becomes, what size bolts would be adequate? ...
Any help is appreciated!

Mechanical engineering is FAR too complex to explain here. See if you
can find a used textbook on "Statics". A Physics text would help a lot
too.

jsw, who went this route.

You would be far better off buying a used trailer, than building one
from scratch. I built a trailer, but at least I started with A NICE
trailer bed from the military.

i

On 2010-06-22, stryped wrote:
Hi,

I am not an engineer but trying to understand bolt strgth, tensile
strength og steel and some other varribles for something I am wanting
to construct. I am wanting to build a car dolly and/or dual axle
trailer. I have welders and have welded on hobby projects but by no
means consider myself an expert welder. My idea is to both weld and
bolt a square togther to form the frame. I have some 3 inch square
tubing laying around, I believe is is 1/8 thick but not sure. It came
from some material stand at work that got cut up.


My idea was to get some scrap 1/8 inch plate and torch cut two ?L?
brackets and weld them togther to form a ? inch L bracket. These
would
go on all 4 corners of the square I would bolt each L with bolts
through the L and through the 3 inch tubing. Before doing this I
would
insert a section of black pipe through all pieces for the bolt to
ride
in. After bolting and everything being square I would weld all joints
with 6011 or 6013 rod with either my AC buzzbox or the mIller
generator welder I just aquired on DC. (Not welded with it much yet)
(I have trouble welding with 7018 for some reason.


My question becomes, what size bolts would be adequate? I get
confused
when I see specs on bolts such as shear strength, tensile strength,
yield strength, etc? I suspect the bolt need only be as strong as the
streth of the bolt steel around it. I am having trouble finding the
specs for mild steel strength but think it might be around 38,000
PSI?
Is this true?


Any help is appreciated!

Ignoramus9757 wrote:

You would be far better off buying a used trailer, than building one
from scratch. I built a trailer, but at least I started with A NICE
trailer bed from the military.

i

On 2010-06-22, stryped wrote:
Hi,

I am not an engineer but trying to understand bolt strgth, tensile
strength og steel and some other varribles for something I am wanting
to construct. I am wanting to build a car dolly and/or dual axle
trailer. I have welders and have welded on hobby projects but by no
means consider myself an expert welder. My idea is to both weld and
bolt a square togther to form the frame. I have some 3 inch square
tubing laying around, I believe is is 1/8 thick but not sure. It came
from some material stand at work that got cut up.


My idea was to get some scrap 1/8 inch plate and torch cut two ?L?
brackets and weld them togther to form a ? inch L bracket. These
would
go on all 4 corners of the square I would bolt each L with bolts
through the L and through the 3 inch tubing. Before doing this I
would
insert a section of black pipe through all pieces for the bolt to
ride
in. After bolting and everything being square I would weld all joints
with 6011 or 6013 rod with either my AC buzzbox or the mIller
generator welder I just aquired on DC. (Not welded with it much yet)
(I have trouble welding with 7018 for some reason.


My question becomes, what size bolts would be adequate? I get
confused
when I see specs on bolts such as shear strength, tensile strength,
yield strength, etc? I suspect the bolt need only be as strong as the
streth of the bolt steel around it. I am having trouble finding the
specs for mild steel strength but think it might be around 38,000
PSI?
Is this true?


Any help is appreciated!



There are trailer plans with engineers stamps for sale from various
places. Northern Tool has a collection of them available for various
types of trailers.

Pete C. wrote:



There are trailer plans with engineers stamps for sale from various
places. Northern Tool has a collection of them available for various
types of trailers.

Unfortunately, nothing there that will fill my bill.

I need a trailer for a 26' long x 10' wide sailboat.

6000 pounds would be realistic.

Fortunately shoal draft with a 4' wing keel.

While a flat bed and custom cradle would be the cheapest solution
I'd never be able to launch from that without a crane.



--

Richard Lamb

cavelamb wrote:

Pete C. wrote:



There are trailer plans with engineers stamps for sale from various
places. Northern Tool has a collection of them available for various
types of trailers.

Unfortunately, nothing there that will fill my bill.

I need a trailer for a 26' long x 10' wide sailboat.

6000 pounds would be realistic.

Fortunately shoal draft with a 4' wing keel.

While a flat bed and custom cradle would be the cheapest solution
I'd never be able to launch from that without a crane.

--

Richard Lamb

The key here is to find the closest match size and capacity wise to what
you need and then adapt from there maintaining comparable material specs
to the original plans. You need a starting point with appropriately
sized materials to base your adaptation on.

On Jun 22, 7:30*pm, cavelamb wrote:
...
One issue is that DOT seems to want the trailer to come all the way to the
back of the boat - little to no overhang.
...
Richard Lamb

Do you think they would notice the joint where it folds upward to be
your gantry crane?

jsw

"Pete C." wrote:

cavelamb wrote:

Pete C. wrote:
cavelamb wrote:
Pete C. wrote:

There are trailer plans with engineers stamps for sale from various
places. Northern Tool has a collection of them available for various
types of trailers.
Unfortunately, nothing there that will fill my bill.

I need a trailer for a 26' long x 10' wide sailboat.

6000 pounds would be realistic.

Fortunately shoal draft with a 4' wing keel.

While a flat bed and custom cradle would be the cheapest solution
I'd never be able to launch from that without a crane.

--

Richard Lamb

The key here is to find the closest match size and capacity wise to what
you need and then adapt from there maintaining comparable material specs
to the original plans. You need a starting point with appropriately
sized materials to base your adaptation on.

One issue is that DOT seems to want the trailer to come all the way to the
back of the boat - little to no overhang.

The only plans I've found anywhere near that length are for goose neck types.

Most likely a *very* easy issue to resolve. I expect the real
requirement is to have a "bumper" area with the plate and lights
(particularly the three clearance lights for over 80" width) back there.
There are probably no structural requirements for that area.

I expect your functional trailer structure can stop well short of that
point, and if you make the frame rails from something like rectangular
tube, you can have the extension section telescope from inside that
frame out the required distance and lock it in place with a hitch pin on
each frame rail so that when you are ready to launch the boat you can
remove the hitch pins and push the rear part in and out of the way and
lock it in that position with the hitch pins.

I would also note that 10' wide is well over the 8'6" width limit and
will require wide load markings and permits.

"cavelamb" wrote in message
m...
Pete C. wrote:



There are trailer plans with engineers stamps for sale from various
places. Northern Tool has a collection of them available for various
types of trailers.

Unfortunately, nothing there that will fill my bill.

I need a trailer for a 26' long x 10' wide sailboat.

6000 pounds would be realistic.

Fortunately shoal draft with a 4' wing keel.

While a flat bed and custom cradle would be the cheapest solution
I'd never be able to launch from that without a crane.



--

Richard Lamb



Go find a trailer that will work and copy it. My 6000# boat trailer from
EZloader had bigger tube than 2". Look at http://www.championtrailers.com/
and look at their parts and axles.

Pete C. wrote:
"Pete C." wrote:
cavelamb wrote:
Pete C. wrote:
cavelamb wrote:
Pete C. wrote:

There are trailer plans with engineers stamps for sale from various
places. Northern Tool has a collection of them available for various
types of trailers.
Unfortunately, nothing there that will fill my bill.

I need a trailer for a 26' long x 10' wide sailboat.

6000 pounds would be realistic.

Fortunately shoal draft with a 4' wing keel.

While a flat bed and custom cradle would be the cheapest solution
I'd never be able to launch from that without a crane.

--

Richard Lamb
The key here is to find the closest match size and capacity wise to what
you need and then adapt from there maintaining comparable material specs
to the original plans. You need a starting point with appropriately
sized materials to base your adaptation on.
One issue is that DOT seems to want the trailer to come all the way to the
back of the boat - little to no overhang.

The only plans I've found anywhere near that length are for goose neck types.
Most likely a *very* easy issue to resolve. I expect the real
requirement is to have a "bumper" area with the plate and lights
(particularly the three clearance lights for over 80" width) back there.
There are probably no structural requirements for that area.

I expect your functional trailer structure can stop well short of that
point, and if you make the frame rails from something like rectangular
tube, you can have the extension section telescope from inside that
frame out the required distance and lock it in place with a hitch pin on
each frame rail so that when you are ready to launch the boat you can
remove the hitch pins and push the rear part in and out of the way and
lock it in that position with the hitch pins.

I would also note that 10' wide is well over the 8'6" width limit and
will require wide load markings and permits.

Yep. I know about that.
She's for sure fat!
(the boat - not the girl! )

But the width is all up at the rail and it doesn't really look that wide
(until you get the tape out).
I don't ever intend to pull it myself.
My little Blazer bitched about the 18 - which barely totaled 2000 pounds.

But a trailer would give me a place to "park it" when hauled out.

And make it possible to visit other places.

Normally there are pads on the end of a telescoping tube to hold the boat
in place. One clever trick I saw a while back was to use a piece of pipe
that fits inside the fixed part, and a floor jack to raise the pads and
snug them up against the hull. The guy who built these liked to hear the
hull groan! I'm not quite that aggressive, but I still like the trick.
That lets the pads drop way down out of the way so they don't interfere
with getting the boat centered up on the trailer.


-

Richard Lamb

Jim Wilkins wrote:
On Jun 22, 7:30 pm, cavelamb wrote:
...
One issue is that DOT seems to want the trailer to come all the way to the
back of the boat - little to no overhang.
...
Richard Lamb

Do you think they would notice the joint where it folds upward to be
your gantry crane?

jsw


??? Ah, Jim, I'm not reading that?

The trailer would wind up something like this one...

http://www.home.earthlink.net/~capri26/trailer.htm

--

Richard Lamb

On Jun 22, 5:16*pm, stryped wrote:
Hi,

I am not an engineer but trying to understand bolt strgth, tensile
strength og steel and some other varribles for something I am wanting
to construct. I am wanting to build a car dolly and/or dual axle
trailer. I have welders and have welded on hobby projects but by no
means consider myself an expert welder. My idea is to both weld and
bolt a square togther to form the frame. I have some 3 inch square
tubing laying around, I believe is is 1/8 thick but not sure. It came
from some material stand at work that got cut up.

My idea was to get some scrap 1/8 inch plate and torch cut two “L”
brackets and weld them togther to form a ¼ inch L bracket. These
would
go on all 4 corners of the square I would bolt each L with bolts
through the L and through the 3 inch tubing. Before doing this I
would
insert a section of black pipe through all pieces for the bolt to
ride
in. After bolting and everything being square I would weld all joints
with 6011 or 6013 rod with either my AC buzzbox or the mIller
generator welder I just aquired on DC. (Not welded with it much yet)
(I have trouble welding with 7018 for some reason.

My question becomes, what size bolts would be adequate? I get
confused
when I see specs on bolts such as shear strength, tensile strength,
yield strength, etc? I suspect the bolt need only be as strong as the
streth of the bolt steel around it. I am having trouble finding the
specs for mild steel strength but think it might be around 38,000
PSI?
Is this true?

Any help is appreciated!

Hunh, you got pretty much the exact same reply on s.e.j.w, imagine
that!

If you keep on trying to bull ahead the way you're going despite
getting an aswer you don't like (which your asking the same question
over here strongly implies) then the next answer is this: Doing it
yourself responsibly will take $60-100+k and four years. Professional
liscensure will tack another few years onto that...

You know, maybe $50 or so for a set of plans isn't such a bad idea?
Copying a friend's trailer would cost even less.

But it's pointless, since you'll just go ahead and do it your way
anyway. I don't understand why you insist on asking for advice you
won't follow for every little madcap idea you come up with. Either
listen, or just do it the way you want without asking.

--Glenn Lyford

On Jun 23, 8:58*am, Glenn Lyford wrote:
On Jun 22, 5:16*pm, stryped wrote:
...

But it's pointless, since you'll just go ahead and do it your way
anyway. *I don't understand why you insist on asking for advice you
won't follow for every little madcap idea you come up with. * Either
listen, or just do it the way you want without asking.

* --Glenn Lyford

You know, even if we might hack something together ourselves we
shouldn't suggest that in a permanently-recorded public forum.

jsw