Vibration - what is normal?

stouchton

stouchton

Senior Member
Hi folks - I did search and read many posts, but this is such an intangible thing I just wanted to ask in a different way.

This is actually real simple - I have a vibration when running above idle. The rear view mirror vibrates so that the image is distorted. The car itself seems smooth - just the windshield and mirror vibrating.

I ask this because I am a Model A Newbie, and the mechanics of the engine are unknown to me. The car runs well, climbs significant hills in 3rd gear at 30 to 35mph, no tapping or knocks from motor. So I think the motor was rebuilt well - just wanted to know if the vibration is normal or if it seems excessive. She does have the stock front engine mount, and Float-a-Motor on the back.

I do understand that the motor is not properly balanced by modern standards and there will be vibration. I want to take real good care of this car - so did not want to continue driving if one of you experts out there think something may be amiss.

And yes - it is an open car, so the windshield is hanging out there unsupported and probably much more prone to vibration.

Thanks for the hand holding
 
I don't know any way to get an answer to your question other than taking an experienced Model A guy for a ride. There must be a club in your area, with lots of members who would be glad to advise.

Steve
 
Hi stouchton,

Or ................ you find a club or other Model A owner(s) & ride in his/their Model A(s) to witness how much shaking goes on; otherwise, sounds like you are blessed with a very good one.
 
Thanks Will and Steve.

Great advice on the local club, and I have been researching that angle. Shot an email to the gent that runs the local MAFCA chapter but have not received a response yet.

In all honesty, if the car did not have a rear view mirror I would not have noticed the vibration!
 
Oooops - thanks to All that responded (our posts overlapped) :)

I was actually real proud of myself for curing all my squeaks and rattles :p

Miracle what new rubber bumpers and door shims can accomplish:eek: (the door shims were for the side mount spares :rolleyes: )
 
Possible that Jerry Lee Lewis wrote the song with words: "Whole lot of shaking going on" while riding in a Model A.

Hope this helps.
 
I think we have talked about this before, H.L.'s elephantine memory must have failed on this one JK HL. How these cars sounded and rode when new is a big conjecture to the extent that any original owners that might have told us are long since gone. I think people that have heard near-original engines are amazed at how smooth and quiet they ran. How much rattling the open car bodies made or should make today is an interesting question.
 
Hi ericr,

No doubt there are engine rebuilder today who can rebuild Model A engines to original specifications -- have seen it done on all types of engines at the two (2) Army Depots, one in Nevada & one in Alabama.

Anyway, yesterday I was trying to think back how many unrestored original Model A's I remembered in our rural area during the late 1940's -- I counted (7) Model A cars, (1) large Model A truck, & (1) Model B -- had a couple more Model A's (10) miles away up the road, but I did not know the owners.

One guy who worked for my father had a Tudor we rode in often; another was his daughter who worked for us with another Tudor -- rode with her husband often.

Our local highways were all gravel -- the road grader had mechanical blade adjustments as opposed to hydraulic, & was not self propelled -- it was towed by a bulldozer.

The gravel roads were so rough & full of dust it was a miracle that cars lasted,

Everything in houses along these roads had to be dusted often -- every grocery store, (& there were so many because people walked to stores), had art least (4) feather dusters that clerks used every day to dust canned goods.

As far as vibrations, with these gravel road conditions, appears one could experienced instant rattle traps if one drove often -- especially when riding on the rough washboard effect on gravel roads immediately before crossing railroad tracks -- could make false teeth jar loose.

I had heard many rebuilt engines came from Sears -- with no air or oil filters, heard 10,000 miles was a miracle before one looked like a smoke bomb.

Really can't remember if it was the engine vibrations, or the roads which shook cars the most -- but with roads like this, coupled with dust mixed with smoke in the rear, nobody expected to see out of the rear view mirror anyway!

Hope this helps.
 
Last edited:
H. L. Chauvin said:
Hi ericr,

No doubt there are engine rebuilder today who can rebuild Model A engines to original specifications -- have seen it done on all types of engines at the two (2) Army Depots, one in Nevada & one in Alabama.

Anyway, yesterday I was trying to think back how many unrestored original Model A's I remembered in our rural area during the late 1940's -- I counted (7) Model A cars, (1) large Model A truck, & (1) Model B -- had a couple more Model A's (10) miles away up the road, but I did not know the owners.

One guy who worked for my father had a Tudor we rode in often; another was his daughter who worked for us with another Tudor -- rode with her husband often.

Our local highways were all gravel -- the road grader had mechanical blade adjustments as opposed to hydraulic, & was not self propelled -- it was towed by a bulldozer.

The gravel roads were so rough & full of dust it was a miracle that cars lasted,

Everything in houses along these roads had to be dusted often -- every grocery store, (& there were so many because people walked to stores), had art least (4) feather dusters that clerks used every day to dust canned goods.

As far as vibrations, with these gravel road conditions, appears one could experienced instant rattle traps if one drove often -- especially when riding on the rough washboard effect on gravel roads immediately before crossing railroad tracks -- could make false teeth jar loose.

I had heard many rebuilt engines came from Sears -- with no air or oil filters, heard 10,000 miles was a miracle before one looked like a smoke bomb.

Really can't remember if it was the engine vibrations, or the roads which shook cars the most -- but with roads like this, coupled with dust mixed with smoke in the rear, nobody expected to see out of the rear view mirror anyway!

Hope this helps.
Click to expand...

-pretty fascinating, H. L. I have also often wondered how much service cars in that era actually received...didn't people tend to take trains for longer trips? Or how much night driving was actually done. I recall Dad's contemporaries who had these cars when new or slightly used stated the cars had the reputation of being able to run-run-run with minimal maintenance, that they were very economical. Not quite what we experience today.
 
stouchton said:
This is actually real simple - I have a vibration when running above idle. The rear view mirror vibrates so that the image is distorted. The car itself seems smooth - just the windshield and mirror vibrating.

I ask this because I am a Model A Newbie, and the mechanics of the engine are unknown to me. The car runs well, climbs significant hills in 3rd gear at 30 to 35mph, no tapping or knocks from motor. So I think the motor was rebuilt well - just wanted to know if the vibration is normal or if it seems excessive. She does have the stock front engine mount, and Float-a-Motor on the back.

I do understand that the motor is not properly balanced by modern standards and there will be vibration. I want to take real good care of this car - so did not want to continue driving if one of you experts out there think something may be amiss.
Click to expand...



Unfortunately I think this is a misconception many here have. Contrary to what some here say, they did not vibrate as being suggested. If someone wants to debate me on this, I am open to that however I want to know exactly what the culprit is, and not just an answer that it is in the design.

The reason I say this is, for several years I have been collecting factory blueprints that often specify exactly what the tolerances and balance specs are on that specific component. For example, the connecting rod print specifies that the big end of the connecting rod was to weight 525 grams with a tolerance of 1 gram, ...and the small end was to weigh 198 +/- 1 gram!! I see freshly re-babbitted rods in engines that miss that by 50-60 grams between the 4 rods!!

On the blueprint of pistons, it states that all machined pistons must be between 319-323 grams, ...and must be balanced within 1 gram. The pistons most rebuilders are using today are around 590-600 grams :eek: right out of the box, ...and often will have 10-15 grams difference between them. Even the modern wrist pins are nearly 200 grams which is WAY heavier than was originally spec-ed.

It also states on the crankshaft blueprint that crankshaft is to not run out more than .002" in the center main journal, the pin journals are not to be out of round more than .00025", and the pins & bearings are not to taper more than .0005" in the entire length of the journal. And, ... it specifically reads in capitol letters "SHAFT MUST BE WITHIN BALANCE DYNAMICALLY WITHIN 3 OUNCE INCH AT ANY POINT OF REFERENCE. SHAFT MUST BE IN BALANCE STATICALLY WITHIN 3 OUNCE INCH.

I could go on with flywheel specifications, pressure plate specifications, and even show pictures of the engine components being balanced at the factory but the issue is most rebuilders (-both past & present) have taken the attitude that restoring to original specifications really does not matter. Now, hobbyists have accepted those deviations in machine work & parts until the mindset is that is just the way they were originally and we should just accept it. When the weight values and tolerances are kept at factory specifications, they do run smooth. Therefore don't kid yourself about "they all vibrated" because they didn't, ...and they shouldn't. ;)



.
 
Hi ericr,

Many could add lots to this, it really was not that long ago:

A. In rural areas in the late 1940's appears there was a strong tendency to still have this very early American or Colonial Frontier attitude; i.e., do everything yourself.

B. The majority of older people I remember in our rural area were proud to say that they painted their own houses, did their own plumbing work, electrical work, carpentry work, auto or truck mechanic work, masonry work, built their own boats; also they had gardens, shared & helped one another, visited others often, & we even knew the names of everybody's horses & dogs -- still remember the names -- no organized labor for construction or anything -- everybody did everything one could imagine in rural construction & rural industry -- men often whistled tunes often, & many men & women played music.

C. Most walked to church if the weather was nice -- some of the very few who had cars would drive only if it was raining or cold.

D. Most people went to bed early -- long work days with many chores -- not all had electricity -- night driving mostly on Saturday nights -- all Saturdays were work days for 1/2 day -- Saturday afternoon was dress up time to get out of the house.

E. The so few deputies were courteous "local" peace officers who knew everyone in the community -- no uniforms -- no blinking lights -- no sirens -- no marked cars -- no pistols worn on hips -- when teens got into trouble, deputies met with teens & parents amicably to resolve problems -- the few jail cells stayed empty most of the time.

F. Shoes got resoled & re-heeled, socks & underwear got mended, no garbage cans or garbage pick up -- excess food was either fed to chickens or animals, or someone came by to pick up same for their animals -- everything else was burned on site -- car maintenance was top priority & because money was so tight, many cars had to last at least 10 years.

G. If one went to the city at this time to visit cousins, many of the city folks I remember came from the country & were not much different.

H. Also had downsides, such as less medical technology, & people still complained as much about weather, politics, & what not.

Ford, like many others did a great service for all of America by striving to produce affordable individual transportation.

Hope this helps
 
Brent makes a very good point -- by the time most of us saw Model A's, most had at least partially re-built engines, either by Sears or others.

Recently had my crank professionally balanced with attached flywheel & pressure plate & I weighed (4) pistons, rings & connecting rods to within one (1) gram on both ends & one (1) gram total weight -- much smoother than before.
 
Seeing there is no torsional damper, there will be uncontrolled crankshaft deflection that will manifest itself as a vibration.

I could not spot anything in the Model A engine design that would correct for torsional vibration. The flywheel can dampen, but there is no element to absorb the energy.
 
stouchton said:
Seeing there is no torsional damper, there will be uncontrolled crankshaft deflection that will manifest itself as a vibration.

I could not spot anything in the Model A engine design that would correct for torsional vibration. The flywheel can dampen, but there is no element to absorb the energy.
Click to expand...

Again, this is where confusion often interferes. A 'Harmonic Balancer' (sometimes referred to as a dampener) is purposed to counteract harmonics. What then must be defined is what is the RPM of the first stage and the secondary stages of harmonics in a Model-A engine? Imbalanced engine parts greatly affect that particular RPM of harmonics. Not all engines have, -nor need a harmonic balancer. It is proper engineering that can control crankshaft deflection.

Also, 1st stage harmonics are almost never noticeable by human feel when the vehicle is in motion. 3rd stage harmonics are generally felt in a Model-A/B engine just prior to it "grenade-ing", ...and 2nd stage harmonics are affected by balance/imbalance at a given RPM. Often times when the engine's reciprocating parts are matched and balanced, that RPM of those harmonics is greater than the normal driving RPM operating range. They will always be there, ...just never felt during the normal course of driving.

.
 
Chief said, "To REALLY enjoy A Model vibrations & rough road escapades, one should wear their TIGHTEST Jockey shorts"!! WHAT DID HE MEAN??? bILL w.
 
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