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A long time ago, a chap called Sang set up an Aces strobex to tune astar hammers in the hangar using a soft hammer and it worked very well. spot on to be excact .

I'm just wondering if anybody knows how to set up the box for this procedure as it is minus 25 not including this wind chill effect.

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Many moons since I worked on Astars, but if I remember correctly... I was using a Vibrex 2000, set on Spectrum Anaylis. Mount the accelerometers on the seat rails as per the manual. When you hit the start button to read the Spectrum, tap the hammers. You want to see a peak at the same vibration level as the 3per. If it is not there, adjust the hammer in or out.

Hope this helps, and I didn't forget anything.

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I've worked with Sang, and his compatriot, Fred.

 

I'm not sure about the particular equipment you are using, but what he would have showed you is to tune the hammers to 19.7 hertz.

This is the frequency to tune out the 3 per rev for a rotor system set at 393 rpm.

 

393/60 X 3 blades.

 

I had worked with Peter Swinnard and had this process down quite nicely using the ECL 'shaker box', but the units broke down and ECL has since replaced it with a modern tuning system.

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  • 2 months later...

I can't say I see the logic in getting the hammer to oscillate at 3/ REV frequency in responce to a dead blow hammer hit, when it is supposed to oscillate at 3/ REV freqency in reaction the ACTUAL main rotor. That is what the ECL hammer "shaker" did, simulated the M/R operating.

 

I just minutes ago finished tuning the 3/REV on one of our B2's that had been "rough" since new. We drilled the holes in the floor 20mm aft of the rivet line in front of the seats and installed the accelerometers. The first flight (looking for the peak @ 1182 RPM at MCP) was .28 L/H and .6 R/H.

 

I shortened the R/H hammer exactly 1mm and the next flight was .2 L/H and .27 R/H. It felt amazing, ride was excellent (though the book says the "3 OMEGA comfort level is .47"). Even though it was lower than they recommend we did not seem to notice the 6/ REV coming out.

 

I think one of the biggest mistakes people make is moving the hammer too far, the recommended (by EC) adjustment is 1mm at a time.

 

Happy tuning.

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