Killing the vibration......how?

[narider]

Thanks, good info and have to agree with the digital, the programmable part still works in my old VDO, it's the spring and all went out in the mechanical area of it.

Of course an old school guy prefers to see the needle..... 

Even us young (new school or preschool) guys prefer to see the needle too...
but then again so does a junkie, that doesn't necessarily make it right. 
Todd

[Dean Los Angeles]

Vibration comes in two basic forms. Plain old shaking and harmonics. Harmonics are related to something reacting to the primary vibration and reacting with a secondary vibration. If you want to see it in action, open the top of a piano and shout into it and listen to the piano answering back.

Harmonics vary with the resonant frequency, in this case the rpm of the engine and the rpm of the wheels. Your tach could be smooth as glass at 7,000 rpm and shake like a mother at 8,000. If you put a vibration analyzer on the frame you would see multiple peaks as you raise the rpm. Small changes affect it. Bolting a small piece of lead weight will change the frequency. Lead dampens everything. Tuning problems with carburetors is sometimes related to severe vibration. I fixed a persistent tuning problem on a Triumph dirt tracker with solder wrapped around the carb.

I would use a digital tach and skip the mechanical version.

Trying to analyze it to come up with a solution is a huge waste of time. There are tons of commercial vibration isolators that were designed by engineers.

Bolt it solid? Guaranteed to destroy it. Not just the tach, but everything electronic. Everything.

The Lord corporation makes a gazillion different products.
http://www.lord.com/Home/ProductsServices/VibrationShockMotionControlProducts/tabid/3280/Default.aspx

[manta22]

The Cosworth 180 degree crank V-8 was notorious for its severe vibration. A good friend related the story of the first track test of their Gulf Mirage with a newly- installed Cosworth DFV. I think it was Derek Bell who took the car out for a few laps and brought it into the pits. "Well, how was it?" my friend asked. "I don't know" the driver replied. "What do you mean?" questioned my friend. "Look" said the driver, pointing to all the needles of the instruments lying at the bottom of the dials.

Now THAT is vibration! The DFV vibration eventually broke almost everything on the car.

Regards, Neil  Tucsun, AZ

[saltwheels262]

have gone through another autometer mc tach . this weekend i should have new solid state
tach installed and motor fired up. it's 2x3x3/4 , $72 and 3 diff. ign. settings w/ hi recall. will know if it works for v-twins, though not in a race environment. try sendec-products.com. model sts 5000 . anyone know of this tach?

franey

[saltwheels262]

still waiting on new tach.

franey

[saltwheels262]

the sts 5000 seems to be accurate and the hi rpm recall works. it will be hard to see at speed because of size. will try to break it next sept.

franey