j.kenzie@sbcglobal.net

I assume (yeah, I know) that with time the tensioner will move if it has room to move in oversized holes. Clamping force in aluminum block will not be enough to prevent slipping. It needs to be constrained for lateral movement, at least somewhat, and enough that it will remain within spec.
I could be wrong too.
Thanks,
Dave

Imo000

The clamping force will probably be fine....probably. But if it ins't, the tensioner will move back to a location that will let the tensioner rod go past the operating limit. This should't be allowed in any design. The only option would be to drill and tap a hole after the tensioner, in the bracket and install a screw that would physically block the tensioner from moving back.

ptuomov

I don't understand why a screw like that would withstand more load than the shear load that a standard bolt interface clamping two surfaces can withstand. How's that goint to work out? A single AN-4 bolt in standard bolt interface will hold about 4,000 pounds of force. What size screw are you suggesting you would put in there?

PorKen

Aluminum T/D is clamped between three 10.9 steel flange head bolts fastened with Loctite into a steel bracket.

Think of any number of manual tensioners like on the 944. Adjust roller into place (w/helper spring), tighten bolt and nut.

There is lot of leverage there and it is slotted. Compare to the Audi T/D which is not leveraged and is damped and sprung to absorb shock and vibration.

j.kenzie@sbcglobal.net

OK Ken.
I'm a big fan of yours. If clamping force is enough to prevent movement, then there may be something else going on here. Obviously out of spec installs are already pinned against the bolt so that is not the problem. We have no evidence of an enlarged hole tensioner that then went on to fail. I think they are rare though.
Take care,
Dave

Imo000

Not more load, but some the load if the main bolts loosen enough for the tensioner to move. It's a fail safe like the OE tensioner rod was.

ptuomov

I'm just questioning the magnitudes here. How large would that screw have to be to for it to make any difference if there's a load that is large enough to overcome a clamping force of those bolts?

Cosmo Kramer

Umm... it's your product. It's your job to know. I just performed the modification and it is far from ideal. Because of the enlarged holes it is very easy to change the angle that the t/d piston touches the lever, not sure what the tolerance is for that but I am thinking it has to be bang on.

I think more data is needed regarding how many needed to be modified, and how many haven't been measured and running around out of spec before we know if modification to the existing design is warranted.

I wish the t/d had a 15 mm stroke. That would allow a fixed design with enough tolerance to get the belt on and account for variations from engine to engine. There has to be one out there with a longer stroke that can be adapted to a bracket.

PorKen

No problem, Dave. Sorry if I sound a little grouchy at this point.

No offence meant or taken, but that's what perplexes me. Why is it my job to know everything? At the moment, if the standard bracket does not fit your needs, you have the option to modify the T/D as others have done successfully. Or not, according to your comfort level.

The T/D modification has been in the manual for years. If there was a problem, I would have heard about it from Roger or directly from a customer and made further changes.

In regards to the point of contact, it changes as the lever rotates. Best to rotate up and CW as far as possible. In fact, I am adding an additional tweak to the modification text in the manual. Besides using a 7mm or 8mm bit, to drill only the two holes on the same side first, rotating around the third, unless more extension is needed. Ultimately, the housing around the third bolt will limit the travel unless clearance is made for the lever.

Imo000

"Why is it my job to know everything?" You can't be serious Ken.

bureau13

How on earth could he know why someone else's unmodified engine seems to be out of spec? If this is not something that has been noted before, how could anyone know, without tearing that motor down and analyzing every piece? It's my understanding that the installs that generally have to be modified have machined heads, etc. That's what that modification is for (correct me if I'm wrong). Unless this is something that's been seen and analyzed in sufficient numbers, I don't think it's even possible for him (or any of us) to know the answer to that question.

Cosmo Kramer

The tensioner has an install range according to the manual with a new belt of 2-7 mm extension. I highly doubt many are close to 2 mm, from the few pics I have seen many are installing in the 6-7 mm range which is 1-2 mm from the maximum allowable with a new belt.

Why not design it so it installs with a new belt at 4-5 mm on most engines? That way more engines will be in range without modifications. Worst case scenario is the tensioner has to be drilled and slid back if it's impossible to string the belt. If it was designed this way mine would have installed at the maximum without modifications.

JBGold07

^^^ common sense

bureau13

Sure, unless a very tiny percentage of cars have this problem. Which is why I asked that question a while back. I never really got an answer, but it was implied to be very small, certainly so with unmodified cars.

Imo000

Is it a tiny percentage or are there many that run with the thesnioner fully extended but they just don't know? There is no data to back up either assumption.