Ignoramus3507 wrote:

Overhead bridge cranes, at auctions, sell either for outrageous money,
or for next to nothing. The reason is that, while expensive to order
and install, they are difficult to take down and built to suit a
particular building. So, unless there is an auction bidder who needs
this crane, there is no one to bid on them.

And here comes my thinking, I want to be able to bid on them and and
remove, economically and safely, for scrap metal.

I am talking about the "big ones", say 30 ton capacity and 60 feet
sapan, not little ones.

The $64,000 question is how to take them down.

I have a 30,000 lbs capacity forklift and a 11 foot boom for it, that
can be raised by forklift to about 11 feet, giving me about 22 feet of
vertical reach. I also have a number of smaller forklifts like 15,000,
18,000 etc.

What do you think, can I take down biggish cranes with it, if they are
say at the height of 20 feet?

I am not stupid and I can think of various possibilities and
attachments, however I also see that things can go very wrong at such
great heights and leverages.

Anyone seen this done?

Maybe add outriggers to the forklift?

i

Three forklifts makes it sort of easy. Position one forklift mid span,
and two on either side of it some reasonable distance away. Make sure
all three are adequately supporting the load, then torch/plasma cut out
the middle section and remove. Move the mid forklift over to one side to
support the span from the track and cut the section that the other
forklift is supporting loose. Repeat as necessary. If you throw four or
five people at this you should be able to play musical forklifts and
have the whole thing down safely in an hour or less.

A lot of resources at it, but not a lot of time, so you need to do the
math to see if it makes sense. Obviously for lighter spans you could
support with two forklifts near the ends, chain the ends to the tracks
and cut out and lower the entire span in one shot, then just grab the
ends with the forklifts, unchain and lower. Either way, you have enough
equipment to attack the project with overwhelming force and just get it
done quickly.