TB216 bent boom

[Kapster]

Hey all,

I have a TB216 that I bought about a year ago through an online auction — it came with a bent boom (lesson learned from relying on pictures only).


Earlier this year, I removed the boom and attempted to straighten it using flame striaghtening, figuring it was already damaged, so what’s the worst that could happen?


I managed to align the boom pivot holes with the dipper arm holes pretty well, but I didn’t pay enough attention to the cylinder mounts.


I've attached some photos showing the cylinder at both ends of its clearance/slop range. It *just* reaches parallel on one side. Ideally, it should move symmetrically both ways (and I’ve flipped it over — same result either way).


Is it safe to say that a new boom would be significantly better? The pins still go in as-is, but I’m not sure they would if I replaced the cylinder bushings.


I also noticed the boom is out of square in the center by about 1/4", but it appears square at the ends where the forgings are welded. Would this be how it came from the factory, or is that more likely a result of the damage?


I've got a quote for a new boom at around $2,600 USD. Should I order it and be done with it? I feel like I’ve taken the current one as far as I reasonably can.

 

[Gecko]

Are you confident the piston rod is straight?

 

[Kapster]

Yea it's good. I did verify other ways that the cylinder pin bores are not parallel with the pivot holes.

I wish there was other machines around for me look at but these aren't that popular in the US. Used parts are almost impossible to find.

 

[V8Druid]

that has had some serious abuse to twist the ram brackets ... having gotten the boom straight again I'd lop the brackets off and re-weld them back on in proper alignment (or make some new ones if they're beyond serviceable)

 

[Storrsy]

My guess is the bucket has been heavily side swiped in to something with the dipper pointing down causing the boom to twist. Can't think of what else could bend it like that- there's some animals out there

 

[Kapster]

Agreed. My dealer said it does happen, not the only one he's heard of.

I wondered if one track fell in a trench while straddling, and as it went in the bucket was side loaded. All I could think of.

You guys would agree then, this can't be normal from the factory and my repair isn't back to original?

I agree it could be cut off and repositioned, I'm just not really confident I could make it look right / not hacked up. I'm tired of messing with it really, just trying to make sure I'm not being to picky and convince myself to get a new boom :x

 

[Storrsy]

Agreed. My dealer said it does happen, not the only one he's heard of.

I wondered if one track fell in a trench while straddling, and as it went in the bucket was side loaded. All I could think of.

You guys would agree then, this can't be normal from the factory and my repair isn't back to original?

I agree it could be cut off and repositioned, I'm just not really confident I could make it look right / not hacked up. I'm tired of messing with it really, just trying to make sure I'm not being to picky and convince myself to get a new boom :x

I'm sure it probably could be done but imagine a twist along the boom will be pretty hard to remedy. Personally id just get a new boom if the rest of the machine is tidy/straight. If you ever want to sell the machine on at a later date I don't think a heavily re-fabricated boom gives a good look

 

[Kapster]

It's in pretty decent shape, it's a "hybrid plug in" with 500hrs on the electric motor, 700 on the machine (so 300 on the engine supposedly). Was planning to concert it to a regular tb216 at some point.

The slew has a little more slop than I would expect but other than that seems to be in good shape.

 

[HuntingHicap]

Not one of ours is it? The hire company I work for used to run Hybrid Tak's. Trouble is they get used as a cheap alternative to a Brokk for indoor demo, so low hours doesn't mean a lot if its been hammering away with a pecker for most of them. Wouldn't surprise me if thats how the boom got bent as well, big lump of concrete or something.

 

[V8Druid]

Not one of ours is it? The hire company I work for used to run Hybrid Tak's. Trouble is they get used as a cheap alternative to a Brokk for indoor demo, so low hours doesn't mean a lot if its been hammering away with a pecker for most of them. Wouldn't surprise me if thats how the boom got bent as well, big lump of concrete or something.

unlikely - he's 'stateside'

 

[Kapster]

I'm in the US. Yea unfortunelty I think your right, it probably wasn't easy hours.

 

[Kapster]

Got a couple general questions I'm hoping you guys can help me with.

*How much side to side play is acceptable in the slew? Is this someone people concern themselves with or not really a big deal?

*Tak shows shims of 1mm, .5mm and and .1mm for all the pivots. The 1mm are some kind of plastic, and it seemed to have them at the outer edges of some joints but not all of them. Is there any reason to use these over steel shims? All I could think is to protect the more expensive components but it doesn't seem they specify using them, just if you need a 1mm thick.

*How close should pivots be shimed?

*What kind of interference is normal for the od of bushings? These are 30mm x 40mm and 35mm x 45mm.

 

[doobin]

Got a couple general questions I'm hoping you guys can help me with.

*How much side to side play is acceptable in the slew? Is this someone people concern themselves with or not really a big deal?

*Tak shows shims of 1mm, .5mm and and .1mm for all the pivots. The 1mm are some kind of plastic, and it seemed to have them at the outer edges of some joints but not all of them. Is there any reason to use these over steel shims? All I could think is to protect the more expensive components but it doesn't seem they specify using them, just if you need a 1mm thick.

*How close should pivots be shimed?

*What kind of interference is normal for the od of bushings? These are 30mm x 40mm and 35mm x 45mm.

For slew do you mean the rotating turret or the boom slew (offset)? Boom slew you'll always have a bit, it's the nature of the beast. Geometrically tight linkage and a lot of leverage. Often those points are not bushed too which exaccerbates the problem, and the 216 was never very tight in that department sadly. For the turret, side to side play isn't a thing- it's supposed to move sideways! What you feel as play is just the necessary clearance in the slew gears. Up and down play is wear in the bearing, this is the type to watch out for.

I'd use steel shims- plastic will be a nightmare to insert into a tight joint. It's common to scrunch up a thin steel one trying to install, plastic would be a lot worse.

Shim them as tight as you can.

By interference do you mean clearance? I'd guess around 0.1/0.2mm, but never really measured. Got to be loose enough to get the pin in. @V8Druid would have a better grasp of this kind of thing than me. Remember that bushes may contract slightly in the ID as you press the OD into the digger. If you get both pins and bushes from the same reputable supplier this will all be taken into account.

 

[Kapster]

For slew do you mean the rotating turret or the boom slew (offset)? Boom slew you'll always have a bit, it's the nature of the beast. Geometrically tight linkage and a lot of leverage. Often those points are not bushed too which exaccerbates the problem, and the 216 was never very tight in that department sadly. For the turret, side to side play isn't a thing- it's supposed to move sideways! What you feel as play is just the necessary clearance in the slew gears. Up and down play is wear in the bearing, this is the type to watch out for.

I'd use steel shims- plastic will be a nightmare to insert into a tight joint. It's common to scrunch up a thin steel one trying to install, plastic would be a lot worse.

Shim them as tight as you can.

By interference do you mean clearance? I'd guess around 0.1/0.2mm, but never really measured. Got to be loose enough to get the pin in. @V8Druid would have a better grasp of this kind of thing than me. Remember that bushes may contract slightly in the ID as you press the OD into the digger. If you get both pins and bushes from the same reputable supplier this will all be taken into account.

Oh I meant to say the turret side to side, sounds like it's normal. The boom slew is really good, no slop in the turret bearing up and down either.

On the bushings, I was referring to the bushing outside diameters in the housings. Hiw much press should they be?

 

[V8Druid]

Oh I meant to say the turret side to side, sounds like it's normal. The boom slew is really good, no slop in the turret bearing up and down either.

On the bushings, I was referring to the bushing outside diameters in the housings. Hiw much press should they be?

depends to a degree on the size ... 2-3 thou usually for interference on say 2" upwards ... that might be a tad optimistic on much smaller sizes - 1-2 thou be more likely easier to press in