Author Topic: Vibration Proof Tach  (Read 4994 times)

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Offline Viau Boys

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Vibration Proof Tach
« on: January 06, 2010, 05:23:39 PM »
One of our dumber decisions last year was going with an el cheapo Summit brand 3" tach. :?

We're looking to replace it with a 5" version that will remain accurate and readable even under high vibration conditions, any suggestions would be greatly appreciated.

We were also thinking of using a digital tach but I have no experience with them so any advice on those would help too, thanks. :cheers:
Matt Viau
Car #1305, Brampton Michigan's Fastest Brick

Offline Dean Los Angeles

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Re: Vibration Proof Tach
« Reply #1 on: January 06, 2010, 05:41:16 PM »
Well, it used to be Los Angeles . . . 50 miles north of Fresno now.
Just remember . . . It isn't life or death.
It's bigger than life or death! It's RACING.

Offline manta22

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Re: Vibration Proof Tach
« Reply #2 on: January 06, 2010, 07:14:02 PM »
If you mount your tach (and other instruments in a panel and then mount the panel with shock mounts you won't have vibration problems. I mounted my instrument panel to the chassis with small Lord aircraft vibration mounts.

Regards, Neil  Tucson, AZ
Regards, Neil  Tucson, AZ

Offline dennisg

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Re: Vibration Proof Tach
« Reply #3 on: June 13, 2012, 12:58:56 AM »
If you mount your tach (and other instruments in a panel and then mount the panel with shock mounts you won't have vibration problems. I mounted my instrument panel to the chassis with small Lord aircraft vibration mounts.

Regards, Neil  Tucson, AZ

  I had two stroke engine vibration regularly destroy my ultralight's analog instruments.. I used little lord mounts on the panel, to no avail.  I  used special engine mounts which helped my comfort greatly( before I used that there was a deep thrumming in my chest when the engine ran)    but they did not keep instrument needles from shaking off etc.

 Digital instruments are immune to vibration.  They are the best solution to extreme vibration levels.
 

Offline manta22

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Re: Vibration Proof Tach
« Reply #4 on: June 13, 2012, 02:22:23 AM »
"I used little lord mounts on the panel, to no avail."

Those mounts are rated for a range of suspended weight; it is necessary to use the appropriate ones.

Regards, Neil  Tucson, AZ

BTW, a friend ran GT40s and Gulf Mirage years ago with a Cosworth DFV with a flat-plane crankshaft. The vibration broke lots of stuff on the cars.
Regards, Neil  Tucson, AZ

Offline kiwi belly tank

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Re: Vibration Proof Tach
« Reply #5 on: June 13, 2012, 03:42:03 PM »
Digital gauges of any type take too much time to read taking your attention away from driving the vehicle. You can glance at a needle, you can't glance at a bunch of digits. Set up a shift light & you don't have to look at all unless the engine is falling on it's face.
  Sid.

Offline 55chevr

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Re: Vibration Proof Tach
« Reply #6 on: June 13, 2012, 03:53:15 PM »
No such thing as a vibration free tach

Offline JimL

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Re: Vibration Proof Tach
« Reply #7 on: June 13, 2012, 10:36:43 PM »
Rubber mounts, heavy solid core solder wound around the case between layers of good duct tape.  Keep adding weight until the mounts settle down with the engine revved up.  The lightest mounts I've found are holding A/C condensors and lines on 4 cykinder front wheel drive cars in the junkyards....pick the ones from non-balance shaft engine models.  Watch for the hour glass shaped ones....dont get caught hauling them out of the pick.a.part in the bottom of the toolbox!

When you get it right, get a piece of the BIG heat shrink tube from the local electric guys to keep everything neat and anchored.

Youll know you got it right when you have to carry spares because they are delaminating from time to time.  Have one mount with a thru bolt, loose, through a rubber donut, so the tach cant get completely loose on a run.  I have to run one side of a tank different from the other.....similar problem when fuel load gets down on return runs.  No more cracks since getting the mounts right, but didnt add mass.

Tune it by feeling the part with your fingertips, trust your feel (use the force, Luke!)

Offline wobblywalrus

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Re: Vibration Proof Tach
« Reply #8 on: June 13, 2012, 11:30:43 PM »
The vibration that is trashing the tach is not doing anything else any good, either.  Some serious thought about vibe reduction might be the best.  Sorta like curing the disease instead of treating a symptom.   

Offline Jack Gifford

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Re: Vibration Proof Tach
« Reply #9 on: June 14, 2012, 12:27:11 AM »
... looking to replace it with a 5" version...
... any suggestions...
I used a Stewart-Warner mechanical 5" (Vertex mag had tach-drive) in mini-rod pulling for many (14?) years. Lots of vibration (blown alky hemi up to 9,000 RPM) with no isolation mount on tach. Sometime during those years a needle fell off, but the replacement unit from S/W has an improved-design needle and is still working fine.
M/T Pontiac hemi guru
F/BFL 1-mile Loring record 2020

Offline panic

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Re: Vibration Proof Tach
« Reply #10 on: June 14, 2012, 10:31:47 AM »
Harley used a mini-trampoline as a frame, with surgical tubing holding the head.

Offline dennisg

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Re: Vibration Proof Tach
« Reply #11 on: June 27, 2012, 02:09:17 AM »
 A lot of good observations have been made:

 1. gauges with needles are much quicker to read but they die ( another of mine did 4 days ago) my Westach egt gauges have an average life of 3 to 4 hrs and their prices have doubled so I'm going digital.

 2. digital readouts don't mind vibration but are slow to read, easy to forget and the meter often hunts around rather than giving a single value.

 3. The most useful one could be a digital meter which lights a warning light when things get dangerous.
     
  Rubber mounts and the object they hold are a tuned system. The resonant frequency of the object and the mounts  has to be well outside  generated vibration frequencies ( harmonics included) or it can vibrate enough to shear the mounts.  Soft mounts lower that frequency as does adding weight (mass) to the system.