Float-a-Motor

[DaWizard]

Original Thread



Hey Bill, you awake yet?

I am wondering, yesterday I installed the FaM from Bratton's, the ductile steel one, and noticed that the far rear mount has an barely interference fit to the cross member.

Dig into your FaM memory and tell me about how much weight, if any, should be on the cross member?

I have the ability to make a spacer thick enough to make the friction there as heavy as needed.

Thanks, J.C.

[BNCHIEF]

Wiz on mine I found the front mount worked quite well, ductile steel like you have and the back mount an interference mount as you say. If it fits snug then it will help support the weight. I get no engine vibration out of my car but my crank is counter weighted and everything balance and is good if not over revving the engine.

[Mitch]

Wiz make sure your cranker-up hole still lines up

[BNCHIEF]

Good tip had to work on that myself and forgot that.

[BILL WILLIAMSON]

I "CANNED" the far rear mount & it worked well!---Do as you wish, I'm TIRED of FAM ARGUEMENTS.
Bill Quiet

[BNCHIEF]

No arguments from me Bill it is not my car, the rear is not the best design but I do not think it does not hurt either.

[Mitch]

Dadarooooni is our VFF Fam expert..

[DaWizard]

The last thing I checked yesterday was the hand crank line-up. It was perfect, just like I had not changed a thing!

Chief, I do not have a balanced crank, and I found that the vibrations I do have have been moved from the steering wheel to the gas pedal, which is fine by me. Also, I have not tweaked it, or tried adjusting the weight around on the mounts either. That is something I will play with when I get used to the new feeling it gives me so I can determine how the adjustments I do affect the vibrations.

[Mitch]

Put rubber hose washers between the engine and your throttle control

[BNCHIEF]

That is a great idea Mitch Red Black, Rubber or the plastic thingy's

[DaWizard]

Well, I just finished a 20 mile jaunt across part of the county to get needed tools, and if I didn't know better, I'd say the engine seems happier to be driven. It wants to rev a wee bit higher in 1st, and in 2nd, and just feels like it wants to go faster. Now, I did sorta fill up the tank with the crap gas, and forgot to refill by measuring bottle of MMO, so it didn't get that boost, so I am attributing all this new found energy to the FaM.

I don't care what anyone says, the FaM does make a difference, for the better!

[Mitch]

Now give her a good waxing and you'll really fly.

Thanks for the report, Dad was right all along HEHE

[plyfor]

The mounts perform with the new donuts; they should be checked perhaps every year or so to make sure they are not squashed and not too compressed.
Do you have the stock front engine mount ?

[DaWizard]

Yes, stock front Y mount, and about 5# weight on far rear mount. (I didn't pick it up to measure the exact weight, but after measuring I found I had a gap between the rubber and mount of .120 so I made a piece of .250 shim to give it some weight to the mount.)

[DaWizard]

Also, as a side note. The compression on the left side is donut snug plus 2 revolutions on the nut, right side, snug plus 1 revolution of nut.

Snug=just unable to turn donut with hand.

[BNCHIEF]

Sounds good to me Wiz enjoy.

[plyfor]

OK . Yes , we've found sometimes the rear rubber block needs a little help at the cross member.

[BILL WILLIAMSON]

I've written LOOOOOOOOOOOOONG step by step directions of HOW I quieted Minerva, with FAMS, front & rear & a flexible exhaust hanger & step by step instructions on how to modify the mounting on the FRONTS! Instructions that the Manufacturer should include!---Hardly ANYONE replied, or said "DIDDLEY SHIT"!---If I sound PISSY, I AM!----GOOD ADVICE warrants an acknowledgement------My time is "VALUABLE"---LOL
Back to our MOVIE!
Bill Tiredtypin'

[Mitch]

If you would kindly repost your FAM tutorial here on the VFF I guarantee you will not only be acknowledged but your article could be enshrined in the tech forum.
We appreciate great advice!!

[CarlG]

I would be one to download and print out said instructions if they are placed here. I searched for them on the "other" site some time back, but could never find them.

Thanks Bill, You are our hero!

[BNCHIEF]

I did not comment on your post Bill as I was busy having fun with the car ,but I can tell you I sure payed attention to what you wrote. Post it again the tech section would be great . I especially like that section because you do not have to hunt and search for advice or answers.

[BILL WILLIAMSON]

Due to popular demand, I'll post it AGAIN ! Soon as I complete the HOT deal, to sell VERMIN !
Bill Rich

[Mitch]

[old31]

I've written LOOOOOOOOOOOOONG step by step directions of HOW I quieted Minerva, with FAMS, front & rear & a flexible exhaust hanger & step by step instructions on how to modify the mounting on the FRONTS! Instructions that the Manufacturer should include!---Hardly ANYONE replied, or said "DIDDLEY SHIT"!---If I sound PISSY, I AM!----GOOD ADVICE warrants an acknowledgement------My time is "VALUABLE"---LOL
Back to our MOVIE!
Bill Tiredtypin'

Dear Mr Bill Tiredtypin, could you post that article just one more time so that we could read it.

Promise, we will reply.

[BILL WILLIAMSON]

TIP# 187
WELL, here goes!
Added a flexible KZhaust hanger.
Installed FAM rear mounts & "canned" the far rear rubber bumper "thingy" DON'T remember if I used the Cast Iron or the Alujimum rear mounts??? ("Probably" was the one that wuz CHEEPEST!)
Bolted on the FRONT FAM bracket (It's much like the '32 4 Cyl mounting)
"Centered" the engine & "determined" where to drill the 3/8" crossmember holes. NOW, IF you use the 3/8" holes, like the instructions say, the long bolts WILL transmit vibrations directly to the crossmember & it will be as NOISY as STOCK !
Here's where my "MAGIC" comes in! With a Harbor Freight Uni-Bit, I enlarged the holes to 3/4" to let the Rubber Biscuits "squish" into, so the vibrations could be stopped in their TRACKS! I DID have to add 2 large flat washers, to center the Crank NUT.
MINERVA was SO QUIET, like a DIFFERENT car!!! She didn't sound like she wuz "tearing" up her motor, past 45 MPH.
Dad Tired

[Big hammer]

Thank you very very much !

[plyfor]

Mitch: can you explain a little more in detail where the rubber hose washers are placed for the throttle control ?
Thanks.

[Mitch]

I never attempted this fix. I just came up with it (brain storm) as a suggestion for Wiz's throttle pedal vibration

[old31]

TIP# 187
WELL, here goes!
Added a flexible KZhaust hanger.
Installed FAM rear mounts & "canned" the far rear rubber bumper "thingy" DON'T remember if I used the Cast Iron or the Alujimum rear mounts??? ("Probably" was the one that wuz CHEEPEST!)
Bolted on the FRONT FAM bracket (It's much like the '32 4 Cyl mounting)
"Centered" the engine & "determined" where to drill the 3/8" crossmember holes. NOW, IF you use the 3/8" holes, like the instructions say, the long bolts WILL transmit vibrations directly to the crossmember & it will be as NOISY as STOCK !
Here's where my "MAGIC" comes in! With a Harbor Freight Uni-Bit, I enlarged the holes to 3/4" to let the Rubber Biscuits "squish" into, so the vibrations could be stopped in their TRACKS! I DID have to add 2 large flat washers, to center the Crank NUT.
MINERVA was SO QUIET, like a DIFFERENT car!!! She didn't sound like she wuz "tearing" up her motor, past 45 MPH.
Dad Tired

Thank you bill.

OK everyone, now lets all respond to Bill's info so he feels the love.

[Dennis]

Bill I now understand your point about the front FAM after reading your explanation about the hole size in the frame. Now 28's and some 29"s (??) had the tab that reached up on the crossmember from the ujoint housing. If you don't install the ujoint far rear bumper don't you think it would help to cut the tab off to reduce vibration? You are the FAM guru meister and think you know best and THANK YOU FOR ALL THE FAM INFORMATION.

[old31]

Yes, Bill is the official FGM.

FAM Guru Meister

Talking about vibration. My rubber pads are on the outside of the frame. Shouldn't they be on the inside? Or doesn't it matter.

[Dennis]

My directions said how yours are.

[Kevin in NJ]

Ummm, I think you need to get shorter bolts.

The cotters are several threads away from engaging the castles on the nut. You can get the nuts to be very loose and not fall off. I somehow do not think you want these bolts to be that loose.

[plyfor]

The pads are on the outside frame web as in post 13

[BILL WILLIAMSON]

I'm a VIBRATION Master (braggin')
Once bougtht a Jaguar MK-2, that had been through 3 owners, because of a horrible ROAR/DRONE. L/F motor mount bolt wuz TOO LONG & threaded through to the FRAME! QUICK fix & I made a BUNDLE, on that car!
Dad Quiet

[Denis4x4]

I just rebuilt my Model A powered Zipper roadster and replaced the rear FAM rubber biscuits. Because it has a custom frame, I used a '32 front engine mount with small block Chevy motor mount rubber that I also replaced with a $20 kit from Speedway. I was amazed at how hard the rubber had become and it was compressed at least 3/8" thus creating a loose mounting bolt. The car runs so much smoother and the fix was cheap.

[plyfor]

Denis, how much did you tighten the rear FAM nuts, if you can quantify that some how? We're try to get an experience check from others. The instructions from the "old days" said to tighten just enough so that the top (metal) cover over the top donut can just be barely moved by hand. Some say just to rotate the rubber donut which seems to be too loose.Others suggest tighten until the top donut just starts to compress which is difficult to gauge.This gets confusing for those not used to FAM's compared to normal stock mount vibrations.. One would think the engine doesn't want to rock around and too loose may be an issue.

[MikeK]

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 upper 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/crossmember. Setup is critical. The donuts may need to be shimmed or trimmed to achieve the proper engine height and tilt. Proper loading on the third transmission support element needs to be present.
WHY- 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-countered 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 useable 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 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.

[plyfor]

OK, thanks. Assume "left" is the driver's side for the "up" force. We have a 5. 5 head with counterbalanced crank, lightened flywheel, etc.and heavier F150 tranny (approx 80#) .

[BILL WILLIAMSON]

Are we OVERTHINKING FAMs AGAIN???
Bill W.

[old31]

Kevin, thanks. I will change to shorter bolts. Good find.

[Mitch]

More FAM Info:

https://www.vintagefordforum.com/for...-float-a-motor

[Chevmn56]

Setup is critical. The donuts may need to be shimmed or trimmed to achieve the proper engine height and tilt. Proper loading on the third transmission support element needs to be present.

Great write up!!!!!!! you mention that proper "setup is critical", and you also mention mounts need to be shimmed for proper engine height and tilt, where can we get this info on what mounts and what the height and tilt should be?????