"Scott Vernon" wrote in message

| So you've never seen one. It is at 25% and less when the
| boom is extended out. Here's a pic of one my little Canuck
| friend.
| http://www.jcwhitney.com/autoparts/P...lay/s-10101/p-
| 1498/c-10101

Sorry.. got an error message on that link

|
|
| | A bascule type draw bridge?
|
| It's only lifting the bridge [boom] .. and again not at
| only 25% of the span
|
|
| Only the bridge? You have any idea what a bridge weighss?
| And the gear is at about 5%, I'd say.

Lifting the bridge / Lifting the boom - Geared rams / Solid Vang ... hang a
boat off the end of the ramp and see if it still lifts.


|
|
|
| | Any hydraulic crane with the boom out?
|
| Not at less than 25% of the boom.... extend the boom and
| the capacities
| decrease exponentially.
|
| Here's a pic of a Grove Crane, very popular in this area.
| See where the hyd cylinders are connected to the boom? I'd
| guess that's about 10%. What do you say?
| http://www.marcelequipment.com/Misc/grovert58c.htm

That rig will lift only it's own boom when the boom is fully extended in a
horizontal position Scotty. The max. capacity is of this model at 18 tons is
reached only with the stick up fully [vertical] and the load as close to the
rams as possible. This would base the weight closer to the rams.[and
counterweights]
Now anyone who has worked around such equipment would understand that the
crane's capacitiy decreases exponentially the further down the boom is
lowered. That's because the distance between the rams and the load point is
extended. At the point the rams reach less than 25% of the distance to the
load capacity is reduced to less than a 1/4 of it's maximum rated capacity.

BTW - I operated both Crane & Excavators many years ago.

Just for your benefit since it seems you have not bothered to read my
initial reply.. I'll just repost it below to refresh your memory.

"Look Scotty... if you place a pair of hydraulic rams to the end of the
boom.... or a distance greater than 50 % of the span.. then the issue
becomes moot. The specific point I'm making is that the rigid vang is badly
situated to handle loads delivered to the end of the boom.

I'll stand by that claim..."




| | An excavator?
|
| Double Hydraulic rams to the main boom at 50% distance or
| better to the
| elbow and a third along the top of the stick to control
| breakout and curl.
| Limits imposed are with bucket size and hydraulic
| capacity.
|
|
| Guess again office worker. Here's another pic for you.
| Can you say 10%?
|
| http://usediron.point2.com/Xhtml/Equ...ails/P2/Excava
| tor-Long-Reach/CATERPILLAR/320C/153870/ByManufacturer.html

First off I'm in the field not the office.
Secondly you'd better do some research on why that long stick has such a
small bucket.
The sixty foot long stick I worked with this spring could not lift anywhere
near it's same sized standard boom excavator. Long Sticks are generally used
for dredging work.. light loads, long reach. It has reduced break-out
abilities. Probably because the load is further away from the rams!!....
DUH!

Maybe you should google for serious excavators... drag lines used to do
really heavy lifting...


| | need more?
|
| Sure... the examples you provided so far hasn't done
| anything to convince me
| that the capacity of a lifting device secured to a
| location less than 25% of
| the span of the boom can lift as much as one located at
| the end of the boom.
|
| How about a diving board?

Dopey!! ... put Bob at the end of a diving board and see if you can lift
it from below close to the base? Now put a block and tackle [1ton] to the
end of the diving board and you should be able to lift it level.. even with
Bob on it.

|
| look at the pretty pictures again. Study them, measure them.
| Take a few days, then get back to me.

Yes Jax

CM