Float a motor results

[Russ/40]

I appreciate that the Float a Motor mounts are contrary to Henry's way so I'd like to not argue that point in this thread. I am curious though about the performance of this modification. It appears all marketing focuses on the elimination of vibrations. I guess this is a bandaid solution that should be solved in a purest fasion, but, I'd like to hear from users of Float a Motor mounts. We're you satisfied that the ride quality was significantly improved?

[Jacksonlll]

I have them on both of my cars and think they are great. A lot less shake.

[ryanheacox]

Been thinking about getting rears for mine. Would you guys recommend replacing the rubber pads and spacers first or jumping right into the float a motors?

[denis4x4]

FAM mounts make it easy to remove and replace an engine. Been using them for 30 years and have had to replace the rubber biscuits every now and them as they can become harder than a hockey puck

[Paul Bjarnason]

My engine rebuilder, Schwalms, recommended the floatamotor mounts for the rear but not on the front. So, that's what I am doing, but I don't yet have my car on the road. This recommendation seems logical, as the stock front mounts seem pretty well sprung, i.e., on springs.

[CWPASADENA]

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I have FAM's in 2 of my cars and I like them.


Only use them only at the rear, not the front.


They have to be carefully "tuned" for best results.


The thru bolt can not be too tight or there is not much improvement.


Just my opinion,


Chris W.

[Russ/40]

I would especially like to hear from those who chose to use FAM mounts to deal with motor vibration.
And, how well did it work?

[Synchro909]

Originally Posted by Russ/40

I would especially like to hear from those who chose to use FAM mounts to deal with motor vibration.
And, how well did it work?

When I put my latest Model A on the road, my wife and I went for a test drive. The motor was on the original solid mounts with new rubbers. We'd only gone a few hundred metres when we looked at each otyher and said "NO" (too harsh due to an engine vibration). I put in the FAMs and we haven't repeated the discussion. Very happy with it now but to raise another issue, do the FAMs, being soft and flexible, affect the handling of the car? Remember, the drive is throught the torque tube, gearbox and bell housing to the chassis. The soft connection between the flywheel housing and the chassis might affect handling. I have driven many tens of thousands of miles with them so I don't really remember what the cars were like before FAMs in that regard.

[MikeK]

I have FAM's in one of my A's. Very smooth on acceleration. The trade off is more primary I-4 imbalance felt at the top of the shift stick. Better than having it transferred to the frame. Since my butt is always on the seat and my hand is only occasionally on the shift lever it is a good trade for me.

The mount donuts need to be unequally tightened left/right to achieve maximum dampening during acceleration. The instructions do not explain how to judge, measure, or do any of this.

Your specific situation may vary, but for my ~75 Hp engine in a 160B the best is with the left two full turns past the point of inability to rotate the lower cast donut cover by hand, and ¾ turn on the right. This is, of course with the proper third element-the center cross member bracket and rubber holding the motor in proper height and angularity alignment with the frame.

If that’s enough of an answer, stop here. Otherwise be prepared for my two cents on the matter.
=============================================
Float-a-motors permit more movement in both vertical and side directions than stock A mounts if the rubber donuts are not too hard or over-tightened. That’s a big ‘IF’, but achievable. To facilitate dampening up/down pulses a third element, the rear tranny support with a rubber pad, is added. Failure to use it will shift the paradigm. Float-a-motors will always damp more side thrust toward the frame rails than stock mounts, but at a cost. There is less driving force delivered to the frame at the attachment point, as it flexes slightly forward, increasing the driving load on the rear spring/cross-member.

FAM setup is critical for maximum improvement. The donuts may need to be shimmed or trimmed to achieve the proper engine height and tilt. Often eliminated, the third element, the transmission to center crossmember needs to be present. Without it the engine will never truly 'float', it will only 'sit' on more flexible mounts.

WHY ALL THE VIBRATION? Inline 4 cylinder Otto-cycle engine running vibration is attributable to three sources:

1) Primary dynamic imbalance of moving parts. THIS MAKES THE ENGINE WANT TO GYRATE AROUND THE CRANK CENTER. Ford did a good job of keeping this below the noticeable threshold, something many rebuilds do not achieve. If you have a dynamically balanced rotating assembly comprised of weight-matched parts in your engine this is not an issue. Contrary to layman belief, crankshaft counterweights have nothing to do with this running balance. Henry’s un-counter weighted cranks were in very close dynamic as well as static balance. Adding counterweights does nothing to make an already dynamically balanced assembly ‘smoother’. The counterweights do two things: a/reduce crankshaft bending force against the main bearings, and b/add mass forward of the flywheel, reducing crank wind-up or twist by storing and slowly releasing the pulsed piston power. This second part, b/, DOES reduce overall vibration, but that fits into category 3) below. The primary dynamic vibration frequency is 1X (equal to) RPM.

2) Second order harmonic imbalance. THIS MAKES THE ENTIRE ENGINE VIBRATE UP/DOWN. This is caused by non-linear and mis-matched piston acceleration/deceleration profiles between pistons traveling up and those traveling down. Four design factors contribute to this: a/connecting rod length (infinity is best but impossible). b/ Ratio of bore to stroke. (Over-square is best, A’s are under-square). c/ Different crankshaft torsional load during the four Otto cycle strokes, causing opposing stroke pistons (two go up as two go down) to impart mismatched cancellations. (less horsepower is better, negative cylinder line offset is better). Model A’s that are ‘modernized’ to give more HP deliver more second order vibration. A’s were designed with positive (+0.125”) cylinder offset to produce more usable torque at a lower rpm. That added second order vibration. The only way to effectively reduce second order imbalance in an I-4 is with an opposing weighted and intentionally out of balance countershaft geared to the crankshaft. Even then, the I-4 design is never perfect at all speeds and power output levels. The second-order vibration frequency is 2X RPM.

3) Torsional pulsation about the crankshaft axis. THIS MAKES ONE SIDE MOUNT PULSE UP WHILE THE OTHER SIDE PULSES DOWN. If you had an infinite number of cylinders there would be none. Adding rotational mass to the crankshaft and flywheel reduces this but a compromise must be made. More mass = sluggish engine acceleration. A four cylinder engine delivers a torque pulse every 180 degrees of crank rotation. The torsional vibration frequency is 2X RPM.

ARITHMETIC: Remember physics? You need to sum all the vectors, both in magnitude and time. That’s what your butt actually feels! Adding #2 & 3 above, the left side engine mount will always transmit more ‘up’ force and the right side more ‘down’ force, in pulses twice the engine RPM. Parts of #1 will add to the 2&3 up/down/ and parts of #1 will force the engine sideways, back and forth between the frame rails.

MODEL A ENGINE MOUNTS and WHY THEY DIDN’T CARRY OVER TO ‘32:
Applying more than 40 HP to stock mounts passes exponentially more vibration during acceleration. Stock design permits very limited up/down movement with very little frame loading if the rubber has not age-hardened and the assembly is not over-tightened. Side thrusts can compress the large flat rubber sheet very little and flex the frame alternately left, then right. Part of the forward driving force of the vehicle is delivered to the frame through the top of the rear spring to the rear crossmember, part is delivered through the two side engine mounts. The design was an adequacy compromise for slightly less than 40 horsepower. As soon as Henry upped it to 50 horsepower (the Model B) engine mounting changed. The range of movement was changed and a third element was added in '32 to transfer some load to the firewall. That ‘32 ‘hanger’ assembly on the firewall is essentially what the third tranny float-a-motor mount does. It takes the weight load off the frame at the engine side mount points and allows the rotational pulses to ‘float’ on those mounts.

[chap52]

What Mike said, I think? Chap

[Jim Baskin III Pa.]

I have had both style mount using the same engine and car,and yes I installed the originals correctly .The motor was rebuilt by Schwalms Babbating Service. There was a noticeable lack of vibration in my steering wheel with the float-a-motor mounts,even my wife noticed the difference.That is my hands on experience.

[BRENT in 10-uh-C]

My father's cars used them during the 60's & 70's until we learned the adverse affects in other areas. I have removed sets from customer's vehicles, -but maybe this is the two thoughts I would have.


If you have a severe enough vibration that you need the FaM mounts to mask them, is it possible the vibration is damaging other items left ignored? I guess the best analogy I ever heard was if you have an infected wound on your arm and you choose to cover it up with a large bandage, does that mean it is healed because you cannot see it any longer?

Also, when an engine/transmission is allowed to move axially, it affects the braking force on mechanical brakes.


.

[Jim Brierley]

My tudor had FOM's when I got it, clutch chatter was way too much. I changed engines, with new V8 clutch and flywheel, still much chatter. I replaced the FOM's with the stock mounts, this eliminated most of the chatter but not all. I later replaced the clutch with a diaphragm type, end of problem.

[steve s]

Originally Posted by MikeK

..... It takes the weight load off the frame at the engine side mount points and allows the rotational pulses to ‘float’ on those mounts.

MIke,
thanks for the detail. I don't understand the part above: I went back and forth between using the third mount many times, trying to perceive a difference. I never could. It's hard to believe that that flimsy thing actually was intended to carry much weight. I could (as I recall) move the little rubber cube in and out by hand. THanks.

Also, are the rotational pulses really perceived by a passenger? I thought they were only felt by the crank.
Steve

[MikeK]

Originally Posted by steve s

MIke,
thanks for the detail. I don't understand the part above: I went back and forth between using the third mount many times, trying to perceive a difference. I never could. It's hard to believe that that flimsy thing actually was intended to carry much weight. I could (as I recall) move the little rubber cube in and out by hand. THanks.

Also, are the rotational pulses really perceived by a passenger? I thought they were only felt by the crank.
Steve

Good questions! Yes, you may be able to move that rubber cube by hand and may even need to secure it in place somehow. One thing I didn't get into was the gyroscopic forces from trying to accelerate or decelerate a spinning mass (crank + flywheel) in an axial direction. This will cause the engine to either want to nosedive or lift up, placing load on that little rubber block. Add that to the added engine inertia down-force when the vehicle accelerates up from a bump and you have the little rubber cross-member mount taking a lot of temporary and intermittent vertical load pulses off of the frame.

It is for the above reason (lack of using that cross-member mount) that FAM's may have gotten a bad rap for frame bending. In this I totally concur with Brent-in-10uhC - If you remove the more rigid stock mounts that act as a quasi- crossmember, then drive potholes and rough rail crossings you may have problems. The FAM tranny mount prevents those occasional excessive down-force flex excursions at the engine mounts.

Last, the rotational pulses- Since it is an I-4 there is a pulse only every 180 degrees. If you lug the engine a bit you can really feel it. Now, speed the engine up and that portion of the vibration becomes part of the more normal I-4 buzz. Yes, you feel them. Ok, then where is the confusion?

What you DO NOT feel are the end to end crank power pulse twists, or axial flexes. The crank behaves just like a torsion bar, with the torque loading periodically applied as pulses at four different points along the length. I didn't address them. Although the un-counter weighted stock crank was/is in perfect dynamic (spinning) as well as static balance, it does twist and rebound from four different points with each cylinder firing. This adds to the cyclic cycle 'mean time between failures' of the crank itself. Adding counterweights does not add dynamic balance, it was already there. The weights simply serve as inertial reservoirs/dampers. With the weenie Model A mains and throws this addition serves to prevent snapped cranks. Henry (well, his engineers!!) knew AA's and BB's could snap cranks, thus the later add of the counterweights. Most modern engines also have an external inertial mass (damper) in front of the engine, opposite the torque drive loading at the flywheel.

Anyone who reports a seat of the pants improvement after going to a counter weighted crank is likely seeing two things- first an old crank and/or flywheel that was not in excellent balance has simply been replaced, and second, there was likely an increase in rotational inertial mass. Unfortunately this second part also manifests itself in a more sluggish engine acceleration. If the flywheel is lightened to compensate there will be zero seat-of-the pants difference between an untouched factory engine and the countered crank/ lightened flywheel combination. Only the crank will know, with much reduced cyclic loading on stress risers.

[Russ/40]

OK, who experienced clutch chatter, who had none before FAM mounts.
And who experienced worse chatter with FAM.

I have both chatter and a chassis vibration. I am deciding if it is worth the effort to go FAM experiments.

[katy]

I'm wondering if adding the rear tranny support will help reduce the vibrations?

[Jim Brierley]

As stated above, my clutch chatter was worse with the FAM's. The diaphragm pressure plate was the final cure. That clutch needs a rounded throw-out bearing but is very smooth.

[Russ/40]

Jim, I had about the same chatter with the stock PP, as I do with the Borg and Beck (Long ). Do you think the Diaphragm version would be any different with that in mind?

Jim, do you know if there is a diaphragm PP using the same bolt pattern as the 9" Borg and Beck?

[woofa.express]

Originally Posted by Russ/40

I would especially like to hear from those who chose to use FAM mounts to deal with motor vibration.
And, how well did it work?

I have installed FOM at rear. It has stopped my hands tingling from steering wheel vibration even after a long drive.