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From: stryped on 22 Jun 2010 17:15
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!


From: hls on 22 Jun 2010 17:31
I dont like the idea of 1/8" steel on something like this that is mean to
carry
a load like a car.

And I dont like the idea of you trying to weld it if you are not sure about
your welding prowess.

If you screw up on this, you can cause a LOT of damage with a loose car
on a dolly or trailer.

If you insist on trying, go down and look at some commercial car dollys or
trailers and check out their design and metal thickness in critical areas.

Without making any calculations at all, I wouldnt consider less than 1/4 "
wall
or maybe a little more depending upon what I was going to haul, and how
the calculations came out.

Now, will your insurance company stand behind what you build?

From: Nate Nagel on 22 Jun 2010 18:11
On 06/22/2010 05:15 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 � 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!
>
>

Before starting something like this, I would try to find some engineered
plans, rather than designing it yourself. This isn't something that you
want to have come apart at speed...

nate

--
replace "roosters" with "cox" to reply.
http://members.cox.net/njnagel
From: chuckcar on 22 Jun 2010 21:49
stryped <stryped1(a)yahoo.com> wrote in news:a427ed4f-7167-4ae1-9b17-
e0e3a1ca05b7(a)x27g2000yqb.googlegroups.com:

> 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!
>
>
Better yet, just buy one second hand locally.


--
(setq (chuck nil) car(chuck) )
From: jim beam on 22 Jun 2010 23:33
On 06/22/2010 06:49 PM, chuckcar wrote:
> stryped<stryped1(a)yahoo.com> wrote in news:a427ed4f-7167-4ae1-9b17-
> e0e3a1ca05b7(a)x27g2000yqb.googlegroups.com:
>
>> 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!
>>
>>
> Better yet, just buy one second hand locally.
>
>

by far the best option.

to the o.p., if you really want to build yourself, do a refresher
welding course at your local community college. you'll be able to pick
the instructors brains about build practices for a project like this -
save you a lot of heart ache down the road.

you can also download a set of plans from the net with trailer designs.
while they seem simple, a dynamically loaded structure like this
should pay proper attention to fatigue as well as just static strength.
this is why there is more to it than just welding. ideally, you'll
have an engineer design or at least review accordingly. if you don't
know someone, this is why it would be important to use a design where
it's already been done for you.

--
nomina rutrum rutrum
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