telescopic boom sections

I realize and accept that larger telescopic cranes get there maximum lift capacity by extending different sections fully or partially, as apposed to boom truck that extend proportionally. What is it that makes this work ie: is the weight or the strength of the boom that adds to or detracts from the capacity? Please educate me.

Basically with a pin and latch boom they are restricted to certain lengths for each section. Since they only have one tele cylinder each boom section has to have latch points. A grove has either 0% 50% or 100% for each section. I think liebherr has more options but your still pretty limited. i don't know that's it better or stronger then each section being proportional but that's pretty much how it has to be for a pin and latch boom. I also assume that kinda like an outrigger beam they are braced in specific places.

It's a lot more complicated then a simple boom cyl and cables and pulleys but I can't even imagine the inside of a seven section boom that was fully proportional. A 4 section boom is packed full enough.

can you have different % of each section and do you always put the first section out first then the second .....

It all depends on what boom configuration you want. Sometimes some sections will be at 50% and others at 100%. You can pick any section you want to run out but you always run your outer sections out first.

https://m.youtube.com/watch?v=ur8nulpGweI

That shows the basic concept of it.

Looks to me like you have to do the inner/boom tip section out first then work your way out. If you do any of the outer sections first the cylinder wouldn't be able to reach any of the inner sections.

Your right. That's what I meant.

Ahh! It's like a light came on I never dreamt that's the way it works, I've heard mention of locking pins but thought it was just for extra safety. Thanks a bunch Kneppune

Heres the kind of proportional boom I prefer.What you see is what you get.My trusty 40 ton coming off the barge.

Not to Knock Hydraulics ,I do enjoy running my Manitex to