Why the "curved/bent" boom on mini excavators?

[Henro]

As compared to my tractor backhoe, which has straight boom and stick pieces, the mini ex has a bent boom and straight stick. Actually excavators of all sizes seem to share this trait.

This difference must add something, but I do not see what it is...

Is there some significance to this difference? Easier to load a truck maybe?

 

[dirtydeed]

I can think of two:

1) reduces chance of curling bucket into the boom (allows for more room) and may allow more room when loading over the side of a truck

2) The curved boom allows the bucket to dig closer to the back of the tractor/hoe. A straight boom would come into contact with the leading edge of the trench before a curved boom model would.


Picture this with a straight boom, and you'll see that the geometry of the curved boom allows for more digging before the boom would contact the top of the trench.

 

[GreensvilleJay]

3) cheaper to make straight ones,on low volume runs ,like tractor BH units...

 

[shiraz627]

My BH has a curved boom which allows you to dig closer to the machine.

 

[Henro]

My BH has a curved boom which allows you to dig closer to the machine.

I also heard that the curved boom helps when digging over something like a fence...

 

[Bulldog]

I think the curved boom allows for deeper digging depth and also has much higher lift capacity because of the way the hoist cylinders are able to be mounted.

 

[SidecarFlip]

I think the curved boom allows for deeper digging depth and also has much higher lift capacity because of the way the hoist cylinders are able to be mounted.

EXACTLY.

 

[Henro]

I think the curved boom allows for deeper digging depth and also has much higher lift capacity because of the way the hoist cylinders are able to be mounted.

You could very well be right.

I keep thinking that whatever shape the boom has, it still has two end points, so it could be replaced with a straight piece.

BUT that may not be the case at all. There may be some geometry at work here!

 

[Bulldog]

You could very well be right.

I keep thinking that whatever shape the boom has, it still has two end points, so it could be replaced with a straight piece.

BUT that may not be the case at all. There may be some geometry at work here!

A straight boom probably wouldn't affect the lift height but digging depth would suffer. I can remember cleaning our settling pond with a standard machine and the end of the boom would be sticking in the water. A straight boom would run out of cylinder travel before the boom ever got close to that low.

 

[torch]

Curved booms are used on excavators because they are mounted closer in on a platform that rotates 360°. A backhoe is a little different, as it pivots much further out and only 180°.

Given the same mass of steel in the boom, a curved boom can dig deeper, and with greater lifting power below grade (because of the cylinder angle) but a straight boom offers greater horizontal reach, so less repositioning when trenching.

Or so Google tells me, anyway.

 

[BAP]

Curved booms are also used to keep the total height of the boom in the upright position lower. That helps for working under objects like power lines and building overhangs.