Can anyone link me to a definition of a "firm whack"?

[IndyJay]

A firm whack requires sufficient force imparted at the correct vector with sufficient mass and velocity to result in a auditory detectable sound similar in nature to a 3 pound duck flying into a glass patio door.

It has a particular feel to it as well... when you let the hammer "coast" the rest of the way to the target once you give it just enough swing to establish the proper inertia. When it strikes you are simply supporting the hammer to bring it to a controlled state of rest. The French probably have a word for it but I don't speak French.

 

[Jstpssng]

Start with what you think is a "light whack", then gradually increase the dosage until the truck starts.
If it was mine though, I would crawl underneath with my 2 lb hammer and hit it as hard as can. If that doesn't work I will go back down with my 30" pry bar... either it will start or something will break and I will do a proper fix.
Patience a virtue? Hell, I can't even spell the damned word.
Fix it now, or eventually you will find yourself laying in a 2 foot deep puddle trying to get the starter to work.

 

[JasperFrank]

I could, but it would mess up your brower history.

 

[coast40]

Whack it until it works. That is the sufficient whack. If you whack it until it breaks, that is too much whack. My dad used to say "Come spin or bust."

 

[ranchito]

When working on a PM starter, it is somewhere between firm enough to seat the brushes on the commutator but not enough to crack the ceramic magnets rendering the starter useless. If it has field windings, swing away.

 

[CH4Ohio]

As in "When my Ford F350 starter wouldn't work the tow truck guy told me to just give it a firm whack"
And how hard is a "light tap"?

For me, and in this type of situation, the force of the "whack" is variable. It starts on the low end with a probing experimental "whack" and increases in intensity until results are achieved or I reach the absolute limit of knowing that I'm about to destroy the object being "whacked". The upper limit is directly proportional to the probability that the part is not-salvageable and will have to be replaced.

 

[WranglerX]

Hitting something hard enough with hammer that you don't want to have your thumb in the way....

 

[Smokeydog]

Whacking expensive equipment with hammers was frowned upon where I worked. Applying sympathetic vibration was OK.

 

[YanmarFever]

What a pack of WHACK JOBS.....

 

[oosik]

I looked and could find nothing - by definition.