Deutz big-end bearing and locating dowel headache

[towbar]

It's not a great picture but it shows the F6L912 connecting journal and the bearings. The dowel (red arrow) is not easy to locate properly and since during disassembly I had found a crushed dowel due to a misplaced and a bulging bearing subsequently worn down by the journal ....I wanna do this like RIGHT.

I'm having a hard time lining up the dowel, the manual is rather superficial & vague, I'm soliciting wisdom from any Deutz gurus lurking in the ether

(I think I had posted a picture of that too but can't find it)

 

[towbar]

Since corrected the rod being in backwards, but that doesn't solve the difficulty. I don't have an engine stand so I'm trying the initial install with engine on its side, the idea being to next turn it upside down for the final long-end work and torque.

 

[Vetech63]

The dowel (red arrow) is not easy to locate properly

I'm not sure what you're asking. Did you compare the old bearings with the new ones?

 

[towbar]

Yes, one of the old bearings (probably installed during an in-frame repair with the mechanic lying on his back in a ditch underneath ) had been installed on top of the dowel, totally out of place, pushing the dowel in until it bottomed and forcing that bearing to flatspot (the crank remained in 'new' specs). The engine was still running, the pushed-in dowel has been replaced (3 in all were pushed in some but only one bearing had flatspotted). My problem is related to this ONLY in the sense that installing this bearing is NOT as easy as it should be; in fact, I cannot remember how I managed to do it in 2008 when I built my then first and until recently last Deutz, an F4L912.

I would not want to do this blindly without very positive feedback and confirmation THROUGHOUT the procedure that the dowel is locked in the bearing slots. Maybe there's a trick of the trade as we say, as for so many other tasks?



I always refrained form badmouthing the farmer who owned the tractor before me, well I know that many struggle with their backs to the (bank) wall, and I can see how easily this can happen.

 

[56wrench]

They are a bit of a pain to assemble. It takes a bit of finagling to get everything properly located. After you get it together and lightly snugged, make sure the rod has the proper sideplay and also has easy sideplay after it is fully tightened. Tight or no sideplay would indicate a problem with the shell or the dowel

 

[towbar]

It's the 'locating' that's a task

I watch {@34:10} these 'keystone' rebuilders install the rods before the pistons in the jugs, maybe that makes for an easier big-end assembly. One can first assemble the big-end correctly and then split it, the piston-side bearing might stay in place waiting for the other half after it's been butted up against the journal.

Three sunny days ahead, so I'll be outside but next are 4 rainy ones; that's when I'm likely to maybe try this other method.

 

[towbar]

Got around to it this morning, and spent a good 4 hours just getting the big ends onto the crank! This engine has a good reputation but as far as this bit is concerned the only thing I'm prepared to call it is a "design atrocity". SHAME on Deutz.

The first attempt was the rear hole with the block on its side as this allows the rods to swing on the piston pins 'relatively' freely. I've seen some videos with the block on one of its ends and the rods can easily become difficult to manipulate. Got this first one done but the second rod in the next to rear hole quickly became a headache. I couldn't get the cap on strictly finger tight but all the way or almost. I kept getting into a situation where the last bit of screw tightening had to be done with a small ratchet even though still with a finger tight fit but ended up with some bindding and no free play. I went at it about ten times before gettin' totally fed up. Then it was "out with the *%$&#^ crank"!

Once the crank was hanging on the hoist I tried the same rod on the same journal and AGAIN it started giving me a hard time. After a few tries I took another rod and cap and that one wen on like butter. Finally got the remaing 4 done this way also but the problematic rod and cap continued giving me some difficulty. In the end they all went on OK and tested with little but free play and next to no radial clearance.

THE problem is hsitty design, and a crank that's like new in specs with new standard bearings. You cannot SEE the dowel remaining engaged while mating the cap and its bearing to the rod and its bearing, or any time after first approaching the crank with the cap and its bearing. Also the bearings are bent at a slightly wider radius which doesn't help in the already difficult assembly. The other engines, at least the ones I have done (Ford, Perkins, Cummins) with the punched lock at the bearing joint coinciding with the cap joint, are far superior in this respect. You 'pee' around blindly throughout a task that requires confirmation of POSITIVE dowel engagement until closed finger tight but you CANNOT provide this. It's like shooting at an enemy you last saw 30 seconds ago in the fog.

So there, remains to torque and recheck for play, reinstall the crank and torque, but I feel good about the job done. Otherwise I would have gone on never knowing if I had left a bearing jacked up on a dowel just like the last guy who did this engine. Made some videos, they'll be part of the build tutorial later.

 

[towbar]

Got it done, not exactly directly though.

When several of the dowels were a little on the short side I couldn' figure it out, they might have been designed not to bottom but to go deeper in the event of a misplaced bearing. Better to risk a spun bearing then a destroyed crank I guess. So when I took them to my local 'blacksmith' he was really busy and I had to twist his arm to change more than just the 3 shortest dowels. I think he changed 3 of 6. The problematic one described above was another one that should have been changed but wasn't, initially.

Rechecking one last time I just wasn't happy with the amount a free play (even before final torquing) so I took it apart again but then couldn't for the life of me repeat another successful install, tried about 20. Taking a closer look I saw that it was the dowel that should also have been changed but wasn't. Took it back to 'smithy' who then changed it. NOW it's good!

For the benefit of those who might google for such info in the future (I hope the forum keeps at least the text postings for ever) here's my take on the thing.

1
I insert the cap bearing into the cap up against the dowel and carefully mate it to the crank journal

2
Next, with the cap relaxed just enough but not one mm more than necessary I insert the other bearing into the same side of the cap with its slot up against the now invisible dowel. THIS is where too short a dowel can lead to FUBARVILLE. As soon as I relax the cap to get the other bearing in, the first bearing jumps the dowel and is now on top of it but this all remains INVISIBLE and may go unnoticed. With fingers holding the halves together they both turn together just as if the dowel were engaged.

3
Hand closing the caps is impossible in the case of a new-specs crank and new bearings. So I go finger tight on the screws as far as I can while continuously rattling the big end. When I run out of fingerpower and if the big end is still free I start very lightly with a 1/4" ratchet still in finger-mode with relentless continuous rattling. If any binding at all is sensed before the halves are completely closed ...ABORT mission and START ALL OVER as many times as required! THIS I think is how the previously short dowels got to be too short, one of the bearings (shown earlier) actually getting a wear-spot over the dowel.

So this last time with the new dowel I got it in perfect, free play remaining all the way to final torque and extra angles.

 

[56wrench]

Glad you got it figured out. Its nice to see progress on a project like this without giving in and having somebody else sort it out