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It's on a M&H C. Is there a specific procedure for tightening them? Deflection of the long rod to the back or torque. I snugged it up pretty good but what should I be looking for?

Is it loose?

You could always contact Mason & Hamlin to see what they recommend regarding their tension resonators. They are very nice people to deal with.

It was loose in my my estimation. What part of the rim am I trying to suck in. The belly rail seemed thick so I would think that if a 3/4" x 1/4" x 18" stick will stiffen the belly rail on a S&S, any tension will be good. I still have some side deflection of that rod.
You know the direction of grain on the board so the cross one from the corner to the S seems to be the one to get the most out of.

I would take a guess: since they help stabelize the rims, once the rims are where you want them to be the tensioners should be tightened. Possibly an accurate measurement could be made to see when the rim/s just begin to move and this would be tight enough - or maybe back off one hex turn at this point.
Do you think that the %MC of the wood in the rims makes any difference to the adjustment?

I think that's why it's loose. She moved up here from Sebastapol.
I tightened it till I thought it was getting there. You know. Its a tensioner. It should have some tension. I gave it some. I could go for the first ka-pop!

I have never adjusted the tension resonator myself, but there is a video of it being done here:
http://www.pianoworld.com/how-a-piano-is-made.html
I am sure the video does not do justice to the process, but they make it look straight forward. Giving it a good thump in the end seems to be the secret trick :^)

Hey Jurgen, I need DSL to view youtube. When I'm at my moms I can watch it.
Describe the thump. What did they hit it with? wood, plastic or metal? It's obviously the way they check to make sure they have it tight enough or too tight and on the edge of breaking loose.

The installer thumps the center hub quite hard with the bottom of his fist. (He is wearing a glove.) It is only briefly shown in the video. I hope someone wit some practical experience can chime in here.

Doesn't seem like there is much practical experience on this matter.

You may have screwed the pooch here. It was my understanding that the tension resonator was set at the factory when new, never to be adjusted again.
The video was of a new piano being manufacturered. You may have noticed that the tension resonator was installed and tensioned before the soundboard or plate were installed.
If you adjusted it during a particular dry period it may get too tight when the rim takes on moisture.
Please check with M&H soon. They may have some sort of torque setting combined with a moisture reading.
Good luck.

It was very loose in my estimation. The piano came from a damp coastal climate to a dry inland one. I will check with M&H Thank you.

I don't believe that "never to be adjusted again stuff." Usually when I'm called in to solve a problem nobody else can figure out and I hear that phrase, that is the first thing I look at. The problem goes away somehow.

Another question; There is an aftermarket tensioner available, what is the procedure for installing that. Does it come with instructions???

Well I called M&H and there is no known installation procedure/ torque per climate/ etcetera for the tensioner . He said these go through to a head on the inner rim. The one I was doing I thought was lagged (wood screw) into the rim. Did they make some that were?

Keith,

As far as I know they have always been installed through the inner rim before the outer is put on.

The turnbuckles are to be made tight. Since it is a stabilization device rather than an active part of tone production, there is no scientific formula for setting it. If the rim changed and the turnbuckles become loose, then just tightening it until it is solid when banged on is good.

It's a carrige bolt type head and the function is to make the inner frame rigid. The board is glued on the inner frame and the outer frame glued to the inner. The bolt heads go thru the inner frame. The boards are Bolduc and rib crowned. I was there this summer for a 4 hour tour. As long as the thing is snug it's a go.

As an aside they've resurrected "Wessel Nickle and Gross" as a name for their actions. Wonder how many buyers will recognize the name? Nice romantic touch.