Am hoping to build a couple of stands for sitting dump truck bodies on, the
bodies weight somewhere between 60 and 80tonne. I want them up on stands so
i can get to the bottom of them as well as the top as we need to get a crane
in every time we roll them over. I had in mind to build a 'triangle' shaped
stand so that the part contacting the body would be as thin as possible and
allow the best access for welding. I had no fixed height in mind, but was
thinking either short enough to sit on a chair under the body while welding,
or tall enough to stand under the body while welding. a triangle seems like
the strongest shape, and i was hoping to not do any internal gussets/bracing
except for two pieces of RHS somewhere at mid height to get the tines of a
Anyone with a bit more knowledge than I've got who can tell me what size of
material I'll need to support these bodies? There will be two stands, and a
max body weight of 80 tonnes, so lets be on the safe side and say that each
stand must hold a minimum of 60 tonne. will inch plate get me there or do i
need to be thinking more like 40mm?
This kind of support really needs to be engineered. You might find a unit
you can copy at a local mine site.
My concern with single stands is that you have to ensure the ground
underneath does not shift or sink. I have seen concrete slabs start to sink
under large loads like that. For such loads I would consider sawhorse
designs made out of six inch rectangular tube with half inch wall.
Two sawhorse style stands would provide you with eight contact points with
the ground. If one or two locations should sink or crack it is no big deal.
Four separate stands gives you a one in four chance of settling. The
sawhorses give you one in eight.
The other thing to consider is that when turning and settling the load
onto the horses you could give the supports a shock/impact load double or
triple the static load without actually dropping it.
To make proper supports you will have to spend big dollars on material.
Either get an engineer or ask the manufacturer of the dump boxes. They
might supply you with a design for a reasonable charge.
Remember a credo that has been modified time and again, yet still
stands everywhere: The demands of the job are never so urgent that we
can not take the time to do the job safely.
I can guarantee if your insurance carrier gets wind of this plan
first they'll go white as a ghost, then they'll be calling as soon as
they get over the shock.
You need to have any work stands like this done locally by a
registered structural engineer who can look at all the details, and
give you certified plans with his seal on them, meaning he's willing
to stake his reputation on them - would /you/ go under an 80-ton truck
body supported only by matchsticks? I sure as hell wouldn't.
If these supports give way it wouldn't be very healthy at all for
the guy under there welding on the bottom side - Worse, he's going to
be so busy concentrating on making a good weld he might miss the
initial warning signs of the collapse till the work starts moving in
front of his mask...
Seriously, if this was my problem I'd put in a requisition to buy or
lease a bigger crane for the shop, so you don't have to call an
outside firm every time you want to flip a body over or hoist in a
fresh slab of wear steel. And do your welding work from the top or
side, where there's much less crush hazard. If you want two people
working at once, put it on it's side, and leave the crane attached so
it can't roll.
Besides, with overhead welding and cutting there's a much higher
chance of getting white-hot Slag Dingleberries dropping and bouncing
into places you /really/ don't want them.
"AAUGH! My Biscuits are Burning!!!" ;-P
Try sci.engr.joining.welding and those boys have a lot of experience.
Welders are a "different" lot. If it was me doing what you are doing, the
job would be done already, and either success or failure would be achieved.
Lots of us welders just "fly by the seat of our pants" and try things.
In your post, the thing not stated as being a sure thing, and IMHO, is very
important is: how high will these be? If you are intending to make them
one foot tall, that is worlds away from them having to be six feet tall.
The shorter the better. Even if the welder has to be inconvenienced to weld
in the overhead position. This is no big deal to a real welder, but they
are becoming harder and harder to find in today's job market. Do all the
welding you can in the flat position.
The specificity of your placement system now comes into play. You said
"crane", but there's a world of difference between a crane on treads, one on
wheels with outriggers, and a gantry crane. A lot of difference in the way
they handle loads, and the sensitivity of handling materials. Call it
"touch", or whatever, but when it comes to moving such big things, a smooth
lift with smooth movement is preferable to herky jerky.
Now, lastly. I think for what you want to do, pyramid shaped would be
monstrously strong, as you would have the pyramid outer structure's support,
and could also put in vertical gussets. The compression strength of
anything is incredible on end, as evidenced by the difficulty of breaking an
egg in your hands by squeezing on the ends. But then, something as simple
as a tic-tac-toe box on end would be incredibly strong, too.
Iggy made an outstanding suggestion in that you buy something preengineered
for the purpose. I know in some cases, these things are made up as they go
along, and are really one of a kind, but you might find Iggy's suggestion to
be the shortest time wise, and the most efficient cost wise.
Personally, I would not hesitate to make some pyramid shaped or tic-tac-toe
supports, with fork attachments for moving. I just wouldn't cut anything
out of the supports for forklift tines, but rather add them on in the form
of channel, or do the simple thing and make a dolly to roll them around, and
a short chain to lift them off the dolly. You already have a crane. Maybe
even make it hydraulic so you can pump it up, roll it, then drop it in
EXACTLY the right spot. Or even roll them under the dump body as it is
lowered by the crane.
One inch steel is GAWD awful strong in compression strength. It's just the
sideloading you have to watch out for. I would use a welding positioner, in
your case, the crane. You have it, and it's free, where a welding
positioner would cost more. Do HOT welds in the flat position, and pour the
metal in there, 7018 being my favorite, but in this case, even 9018 or
Have someone who at least is proficient in engineering help you arrive at a
configuration as to angles and reinforcement and safe working loads.
But, I would think a baseplate, pyramid, and internal compression bracing of
1" steel would be adequate for what you want to do. I like the tic-tac-toe
And remember that the more you use, the more you divide by. IOW, four
supports will hold 1/4 the weight, where three would support more weight for
Lastly, don't forget that if you can leave the crane attached, that the
crane will be supporting some of the weight, and the stands won't be holding
all that much.
Lots of things to consider. To a welder, it's like a puzzle. Let's try
Hmmmmmmmmmmm. That didn't work worth a flip. Where did it fail? Lets try
Welders love puzzles. We're problem solvers while everyone else is standing
there scratching The Twins.
Keep us posted.
Those are big loads but I'm less worried about the strength of the
assembly than I am about the side loading when setting the assembly
down, the base to height ratio, and the surface you are setting these
down on. Even if you are working on 10" of reinforced poured concrete,
I'd have some issues of point loads, tipping, etc. If you are working on
any sort of soft surface exposed to the elements, you need some serious
review of what you plan on doing.
As others have said, buy off the shelf or get an engineer in to review
and sign off on what you do. Really cheap compared to the alternatives.
Shaun Van Poecke wrote:
If I was forced at gunpoint to make something like that (say 2 feet
tall), and if I had no access to an engineer, I would simply stack
squares of plywood, 1.5-2 ft in size, glued one to another, lying
horizontally on top of another, and put a 1" steel plate on top.
My preference would be to just buy something off the shelf.
Then you might have gotten shot in the head ;-)
I had a talk today with another local business owner who had done this sort
of work in the past, he said avoid timber at all, even hardwoods as these
sort of weights will make timber explode. If they sold 60 tonne stands on
the shelves, I'm sure I could talk our accounting department into buying a
Those are big loads, but even big loads are just small loads on a bigger
scale ;-) Side loads are important, and the height to base ratio is
absolutely critical in this application. Im looking at a base on the
pyramid being (excuse my jumping across metric and imperial here) 2400mm x
1500mm or about 8'x5'. this gives an extremely optimistic contact patch
(assuming all parts of the base are in positive contact with the ground) of
5,546"sq. Now, lets be generous and say a load of 100 tonnes per stand,
being a total or 200 tonnes which would give us a pressure of (in an ideal
world) 39lbs per square inch.
Of course, there's every chance Ive got my math wrong here, since i just
added it up now with my cell phone, but that sounds about right to me. In
reality, the weight on the ground would be a lot less.
Id agree with you in normal situations; i rarely have made a tool for a job
that couldnt be bought, not even for the (sadistic) pleasure in it. I
wouldnt waste my time builsing stands for my car, even though i could easily
make stands that are better than anything i could buy in my local auto
store, and i dont even have to pay for materials. Its just *easier* buying
But when it comes to something like this, there just isnt that much
available. I dont know what the situation is like in the states, but even
in a town like the one im living in, surrounded by nothing but desert and
mines for the next day's drive, there isnt that much *really* heavy
equipment around, despite being surrounded by 240tonne dump trucks. What
most places do is pretty much what some of the guys on RCM have done; pass
the buck. They say they cant handle it, havent got the cranes, havent got
the stands, havent got the experience, havent got the labour.
I work at the biggest shop for about 1200 miles. But even we dont have the
stuff to deal with this job. Yeah, We've got a few cranes, a few 50 tonners
and a 130 tonne. Despite calling around to the other shops that were 1200+
miles, All they could tell me is that they had to build their own stuff. I
could have said that we couldnt deal with it either, but I think we can. By
following appropriate safety procedures and taking things one step at a
time, im sure we'll get there.
I dont come from an engineering background myself, i come from a
boilermaking background. I was lucky enough to get a chance to move up into
managing projects this year, and im doing the best that i can. Around here
(as im sure it is in most places) many supervisors are well behind the eight
ball when it comes to project management. Materials are ordered after they
are needed, drawings are examined when the shop staff dont know whats going
on, plans are drawn up after the fact.
I try to be a bit more proactive.... This project isnt coming up for another
month or so, but im trying to get in early, think about the logistics of how
to handle the job, what equipment and consumables to use, materials that
will need to be ordered, as well as the nitty gritty of who will be doing
what, and in what order. Rest assured, RCM wont be the final say on what
happens, especially in terms of safety ;-)
But its still a good place to start. For stands above 750kg (1650lbs) in
australia they require engineers certification. 60 tonnes well exceeds
that. But the usual process is for someone involved in the actual work to
draw something up, run it by an engineer who will either approve it, or give
some suggestions about what needs to be changed. Once the engineer signs
off, neither the specs, the material or the process can be changed. The SWL
as specified by the engineer must be welded onto the stand.
Calling around to suppliers was my first port of call, then i asked others
who were doing the same or similar work. RCW was my next port of call, then
i asked contacts i know locally who have had some experience in the past.
Coming up next will be an educated guess based on all these factors plus my
own experience, then flipping through some engineering books. Then submit
the drawing to an engineer, see what the feedback is, if good, go ahead.
If someone ends up crushed (most likely to death) because of something i
design that an engineeer signs off on then the engineer will be going to
prison, not me. Getting engineers to sign off on things releases my duty of
care, which is all that anyone cares to do in this day an age of so called
'safety awareness', but that kind of safety is only a way of looking out for
number 1 as far as i can see. The way i see it, I wouldnt want to get
crushed to death (or even hurt at all!) myself, and I'd have a pretty hard
time living with myself if someone else suffered because of my effort or
lack thereof, so i put the time in and find out as much information as i can
before going ahead with anything.
Thanks for the suggestions Bruce. We dont have any local structural
engineers, and the ones who are distant prefer to sign off on work that to
actually do any of it themselves. If they design something and it doesnt
'fit' then they have to pay for the cost of materials/alterations to be
done. To give you some idea of the cost involved, a simple drawing in
autocad (basically measuring up then drawing) with no engineering work costs
somewhere between AU$5,000-AU$7,000 - with no liability. Getting something
as basic as a stand measured, designed, engineered then drawn would likely
cost more than my entire years wages. I was hoping to go with something a
bit more substantial than mathcsticks in the end though. I usually start my
viewpoint on these things by looking at the chassis and pivots on the actual
truck being used. If the truck can hold the tray at only 4 pivot points (2
hinges and two ram attachments) fully loaded up at a couple of hundred
tonnes, then a similar structure has an excellent chance of supporting the
same tray empty.
We have a few cranes that are big enough for this, but its an ongoing
refurbishment contract, and last time i checked the cost of a 50T crane came
in at about AU$500,000. A 130 tonner costs a fair bit more than that. We
hire our cranes out on site, and if we were to have them in the shop 7 days
a week holding up trays while they were being welded then I'd probably lose
my job, just shortly before everyone else in the shop lost their job due to
the company going bankrupt. After having analysed the situation, a stand
seems like the most logical way to go, for many reasons. It just needs to
be made right.
Ive done my share of overhead, and burnt more parts of myself than i care to
mention in the process ;-) Thankfully the guys on this crew wont have it
quite so hard as i did..... they'll have fully enclosed speedglass helmets
withforced air respirators (almost like air con for your head), hoods,
leather jackets, aprons and spats. Best of all, they'll be welding with 715
supercore wire and a 75%argon 25%CO2 shielding gas giving some of the
easiest spatter free vertical up/overhead that there is to be had. Almost
makes me want to go back to welding. Nah.
Right. Wood timbers can take a few hundred pounds per square inch
perpindicular to the grain (actual number is a function of species,
grade, and condition) and they don't take point loads well (they crack
and split) Much stronger in axial compression.
Shaun Van Poecke wrote:
Your math is in the right ballpark. And the height to base ratio is
indeed critical. Redoing your numbers shows about 5000 pounds per square
foot of base. This is well within the range where many soils start
flowing like viscous liquids. Expect to have issues with things sinking
and tilting. If you are on concrete, you will always have point loads
since the base and the concrete will always have irregularities. This is
where you may need to put a layer of timbers down between the stand and
the concrete to provide a certain amount of cushioning.
Shaun Van Poecke wrote:
Have you checked into getting some really big I-beam?
There is a piece locally here a scrap yard uses as a sign
that is maybe 5 foot tall. I-beam would have specs already
published for loading and such. If it was just setting on
the floor it would be pretty robust, just have to keep it
from tipping over.
Another thought is building a trench/pit in the floor where
the work area is located. Without really seeing what parts
you need to get at (to weld) hard to say if it would work.
You might be able to drag the bodies into place then and
never even have to lift them.
Just some thoughts...
I was thinking the same thing. A pair of suitable beams, properly
supported, properly braced, spaced about 2/3rds the length of the truck
box. Slide, roll, or lift the box on to the beams, then slide it into
position. If you need working clearance, a couple of fat hydrualic jacks
will lift it the few inches you need to insert some shim plates.
With a bit of brainpower, you could probably set this up so it was the
right height to be able to drive the truck up next to it, unbolt the
dump body, insert some transfer beams, slide it right onto the fixed
beams. The housemoving crowd does this all the time. I've seen those
guys use some machinery moving rollers with side flanges that grip a
beam. Things like this:
A quick check on my beam calculator shows for a 20' long beam supported
in the center and the ends it needs a suprisingly (to me anyway!) small
beam would be suitable.
Done right, I'd expect to be able to drive a truck over to the weld
station, have the dump box sitting on the rack ready to work on in an 8
hour shift with a couple of guys and NO CRANE needed. OK, maybe a front
end loader to wrestle the transfer beam into place.
That business sounds like they don't have a clue what timber can do.
Maybe visit a shipyard where they are laying a ships keel and take a
look at the the WOOD blocking they are using. The entire ship gets built
on that timber. When complete there is FAR more than 60 tons on it and
it doesn't move. Might compress it some.