derived specs on Deutz 1011 timing belts

[nilespf]

Hello all, Just purchased a Bobcat 873 with the Deutz 1011F engine, oil cooled, turbo diesel. Began the effort to replace filters and oil along with the timing belt. Spent time trying to find the tension specs for the belt. Finally gave up. As you know, nothing exists from Bobcat or Deutz as to what the timing belt tension is set to. After a lot of analysis I backed into what the numbers mean when we use the infamous Deutz tension meter. Bottom line is the meter measures force (in Newtons) used in deflecting the belt. The amount of deflection corresponds to a predetermined belt tension based upon the span distance and bending modulus of the belt. Sounds like a bunch of jargon but the Deutz meter is nothing but a customized device used in the "force deflection" method of measuring belt tension. Manufacturers usually provide the deflection force and we have to measure the deflection, force and determine the span length. This is what I have come up with:

Pretension = .73 lbf @ .166" deflection or 3.25 N @ 2.7 mm deflection
Final distrubuted (locked cam) tension = 1.82 lbf or 8 N corresponding to a belt tension of 25 lbf.
There is a bunch of background to these numbers so post away with questions.

 

[Tazza]

I'm guessing this model isn't running a spring loaded tensioner?

We rebuild this model a few times a year, we do not have the fancy tension tool, the mechanic must just know what seems right. Also be aware, that it will loosen up after the belt beds its self in.

 

[nilespf]

Your right, essentialy just adjust the slack out with a bit of tension then lock it down.. If your careful you can properly read the .75 lbf (3.25 N during freewheeling). Deutz has us then lock the cam to the shaft, spin the crank and the torque moment created by the a locked down cam distributes itself around the loop for the final 1.8 lbf (thats the 8N miracle reading). At this point the belt has bedded it at a 25 lbf tension. It's actually quite clever so why not just tell us!
Do you have any thoughts on how much dynamic moment the oil pump shaft will add when the engine is spun up? I cannot find any info. I suspect it is non trivial with cold oil. Hope someone knows.

 

[Tazza]

I'd like to think that with constant load, there will be minimal shaft movement when rotating, so the figure shouldn't change.

Hopefully you are over thinking it, these engines are a little more complicated than most, but they do run very well.

 

[863H-SkidSteer]

nilespf,

I plan to replace the timing belt on my 863H with the Deutz engine this spring.

The Deutz tension gauge that Bobcat specifies does not appear to be available. The OTC 6673 gauge that Foley Engine recommends seems like a wild guess.

Spring scales that measure up to 10 Newtons are available on Amazon, but where did you come up with the belt deflection?

I have looked, but have reached a dead end. You have my attention.

 

[863H-SkidSteer]

I have done a little more investigation. Here is what I have so far….

• The OTC gauge will accurately measure the tension in the timing belt. I will explain later.
• The tension Deutz wants on the timing belt is not specified in Newtons or pound-force in the Bobcat shop manual. The scale on their gauge is not calibrated in Newtons.
• Amazon is plain wrong when they say that the OTC gauge will measure ft. lbs. This is a unit of torque not tension. The gauge does not measure torque. That confused some of their customers.
• Apparently if you let the OTC gauge snap close without a belt in it, you risk breaking the gauge. There are a lot of failures on Amazon.

The OTC gauge is calibrated by measuring the tension in a "single-strand" belt suspending a known weight. I have a used timing belt taken from my machine 6+ years ago. I suspended 80# of weights from the belt. This is a "double-strand" belt. I then measured the tension is one strand. It was 40#, half the load. I wasn't expecting this. It is exactly what it should be.

 

[Firefighter]

I have done a good many of those, i guess i never really paid that much attention to belt tension,
always set them by feel, i have never had any issues

 

[863H-SkidSteer]

Firefighter,

I agree with you 100%. If this were the fan belt on my old truck, I would tension it with a pry bar and forget about it. As you know, this thing is a timing belt on an interference engine. I am moving forward with a little bit more caution.

Manufacturers want to build consistent products. They come up with different tools to make this happen. That is all the Deutz tensioning gauge is.

Lacking any new information, I will probably proceed as I did 6 years ago.

Thank you for responding.