3x8 motor mounts....are they? - Ferrari Life
 
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post #1 of 20 Old 09-11-2013, 01:12 PM Thread Starter
 
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3x8 motor mounts....are they?

OK here's one for the engineers and mechanics alike. Are the motor mounts really motor mounts?

If you haven't taken one apart they are made up of an assembly of a large spring, steel mesh donut and rubber diaphragm.

I'll let a couple answers and thoughts post in before I share some more interesting research on the stock units....
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post #2 of 20 Old 09-11-2013, 04:00 PM
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Here's a picture of mine for reference. It exploded after I removed it.
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post #3 of 20 Old 09-11-2013, 04:52 PM
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Now if you compare them to the "aftermarket ones" I installed. They are a whole different ball game.

Professional mod done by Bret aka "The Hitman"
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post #4 of 20 Old 09-11-2013, 06:42 PM Thread Starter
 
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Thanks for the pics Chris

How many engine mounts have springs ???

OK, some clues...
2nd order harmonics......
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post #5 of 20 Old 09-12-2013, 01:35 AM
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Great thread , wait in anticipation for the answer .

"Bret" aka " the hit man "

Where is Luckydynes he also put alot of effort into this subject
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post #6 of 20 Old 09-12-2013, 04:19 AM
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They are motor mounts by definition as they are the only thing that holds up the engine. No question there.

They are also pretty good vibration dampers. The inclusion of the spring allows the support and damping functions to be separated and that allows considerably more optimization than is possible in more traditional designs that rely on a visco-elastic material for both and really let you optimize anything but the production cost.

I designed something very similar years ago for a graduate project. The Prof had invented and prototyped and electric generating furnace:
https://www.google.com/patents/US4262209

which used a 1 cyl engine……and vibrated itself and its rubber mounts across the floor. The heart of the problem was that the natural frequency of the system was way too high (aka way to close to the engine’s operating frequency) which allowed way to much energy to be transferred to the floor. The solution was to support the engine on a spring/damper system that oscillated about an order of magnitude below even the cranking frequency….. and transmitted about 1% the vibration energy that the original design transmitted.

The Ferrari flat crank engine, like a 4 cyl is inherently balanced to the 2nd harmonic ( kind of rough) vs the Ferrari 12s that like a straight 6 are inherently balanced to the 3rd (very smooth) harmonic so by Ferrari standards the V8 cars run pretty rough. US V8s do a little better by using a 90 degree crank to allow them to damp the 3rd harmonic at specific rpm ranges but that costs hp, which is a trade off Ferrari wasn't willing to make nor where they willing to accept the vibration the V8s where making…..so they spent money on motor mounts that included a better damping system so even thought the engines were rough no one would ever know it and they'd feel like Ferraris
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post #7 of 20 Old 09-12-2013, 06:06 AM
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...Professional mod done by Bret aka "The Hitman"
Lol.

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Originally Posted by duck.co.za View Post
...Where is Luckydynes he also put alot of effort into this subject
I owe Sean for the idea - he's the first guy who used the Mustang bullet mounts, so far as I know. They definitely transmit more vibration than the stock mounts, but not enough that it's even close to uncomfortable.
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post #8 of 20 Old 09-12-2013, 06:25 AM
 
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...The Ferrari flat crank engine, like a 4 cyl is inherently balanced to the 2nd harmonic ( kind of rough) ... so they spent money on motor mounts...
Excellent explanation. When put on a bell curve with all other papers so far submitted on the topic, I beleive the grade is A+. Thank you for the explanation.

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post #9 of 20 Old 09-12-2013, 07:48 AM Thread Starter
 
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Originally Posted by mk e View Post
They are motor mounts by definition as they are the only thing that holds up the engine. No question there.

They are also pretty good vibration dampers. The inclusion of the spring allows the support and damping functions to be separated and that allows considerably more optimization than is possible in more traditional designs that rely on a visco-elastic material for both and really let you optimize anything but the production cost.

I designed something very similar years ago for a graduate project. The Prof had invented and prototyped and electric generating furnace:
https://www.google.com/patents/US4262209

which used a 1 cyl engine……and vibrated itself and its rubber mounts across the floor. The heart of the problem was that the natural frequency of the system was way too high (aka way to close to the engine’s operating frequency) which allowed way to much energy to be transferred to the floor. The solution was to support the engine on a spring/damper system that oscillated about an order of magnitude below even the cranking frequency….. and transmitted about 1% the vibration energy that the original design transmitted.

The Ferrari flat crank engine, like a 4 cyl is inherently balanced to the 2nd harmonic ( kind of rough) vs the Ferrari 12s that like a straight 6 are inherently balanced to the 3rd (very smooth) harmonic so by Ferrari standards the V8 cars run pretty rough. US V8s do a little better by using a 90 degree crank to allow them to damp the 3rd harmonic at specific rpm ranges but that costs hp, which is a trade off Ferrari wasn't willing to make nor where they willing to accept the vibration the V8s where making…..so they spent money on motor mounts that included a better damping system so even thought the engines were rough no one would ever know it and they'd feel like Ferraris
Mark as always you never fail to dissapoint, A+ (of course none of us is married to him either, )
Is it just us engineers that sit around thinking of these things and find them not only fascinating but worth the research?

Mark pretty much nailed it

I haven't sat down and run the numbers yet but I was wondering about the cases where the dampers are replaced with solid mounts. now the entire vehicle is the mass that has a new natural frequency and the suspension is pressed into service for two functions. how does that effect the ride, handling etc.. There is also the gearbox to consider as well, the shafts run parallel to the crank and have their own harmonics.

the only downside to this setup is that the drivetrain must power the wheels on the ground and thus the TQ causes the engine assembly to rotate and will missalign the shifter rod. though this is more an issue on engines that have considerably more TQ then stock. Reverse is is a great example of watching the engine twist on it's mounts.

in anycase I found it to be a novel way to handle the harmoincs of the flat crank design. now to design/improve the mount to handle the increased TQ of the large displacement and forced induced engines.

oh, and the woven steel mesh is also a cushion with a very low natural frequency, I'd gather that's the failed part in normal cycles aside from a broken or rusted unit. that part is specific to rotating machines over 2k rpm per Vibrachoc.

Most all the info I've dug up came from Vibrachoc. I'll be honest that I hadn't given the part much thought and when I did it was one of those light bulb moments and I went, "I know where I've seen and used this before" I had never really thought about it in an application for road cars. heavy equipment, buildings, transport vehicles for volatile and dangerous cargo, etc.. sure.

maybe as a consequence of getting older I just don't feel like jiggling my teeth loose when out for a spirited drive, or having to collect hardware as it falls off the car! maybe I need to stop driving the 'ol benz for a bit... nahh fast and smoooooth is the way to go, now to find the buckets of money to make it so.
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post #10 of 20 Old 09-12-2013, 07:53 AM Thread Starter
 
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Lol.


I owe Sean for the idea - he's the first guy who used the Mustang bullet mounts, so far as I know. They definitely transmit more vibration than the stock mounts, but not enough that it's even close to uncomfortable.
it's not too bad, the cars make lots of noise and vibration to start with. what I've seen and noticed is the increased propensity of hardware to come loose, specifically the axle CV bolts, exhaust manifolds at the heads and the oil dipstick tube mount on the cover strangely. the rest I just sweep under the rug as unknown parts j/k...
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post #11 of 20 Old 09-12-2013, 09:26 AM
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Is it just us engineers that sit around thinking of these things and find them not only fascinating ......?
Probably, we are an odd bunch

Mark pretty much nailed it


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the only downside to this setup is that the drivetrain must power the wheels on the ground and thus the TQ causes the engine assembly to rotate and will missalign the shifter rod. though this is more an issue on engines that have considerably more TQ then stock. Reverse is is a great example of watching the engine twist on it's mounts.

.......

maybe as a consequence of getting older I just don't feel like jiggling my teeth loose when out for a spirited drive, or having to collect hardware as it falls off the car! maybe I need to stop driving the 'ol benz for a bit... nahh fast and smoooooth is the way to go, now to find the buckets of money to make it so.

.

Yeah, the stock mounts work pretty well on stock cars and I agree I enjoy the smooooothness they deliver.

I haven't really decided what to do with my car. With the blower motor I left the stock mounts alone and really had no issue, but I wasn't running on the track either.

With the V12 I probably don't need the stock mounts but I'm pretty sure I don't want urethane either. I think I read that daytona rubber mounts can be used.

Another option I've been considering that might be of general interest to to simple add snubbers of some kind. The goal would be the new snubbers don't do anything most of the time so the car stays smooth, but do limit motion (and therefore transmit more vibration) under heavy loads. I haven't got far enough to actual try to design any to know if it's actually possible, but I think it's the right idea.
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post #12 of 20 Old 09-12-2013, 01:28 PM
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Hmmmm?

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Mark as always you never fail to dissapoint,


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post #13 of 20 Old 09-12-2013, 08:37 PM
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I do not envy the engine mount engineer's job. Trying to balance dampening capability, torsional load strength and some sort of longevity is not easy. The mount in the modern cars do a very nice job, for a relatively short period of time. The cars feel quite smooth when new, then slowly begin to feel as though they run "rough". Replacement of the mounts makes a car with 20k on the clock feel like brand new again. That job seems about as rewarding as being a weather man.

I will say that I see the new "tripod" configuration to be a weak design. The newer Ferraris and Maseratis using an engine mount on each side and a single transmission mount really use up the mounts. The Lamborghinis and even older Ferraris which used a 4 mount system see a better service life.


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post #14 of 20 Old 09-15-2013, 05:36 AM
 
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The Ferrari flat crank engine, like a 4 cyl is inherently balanced to the 2nd harmonic ( kind of rough) vs the Ferrari 12s that like a straight 6 are inherently balanced to the 3rd (very smooth) harmonic so by Ferrari standards the V8 cars run pretty rough. US V8s do a little better by using a 90 degree crank to allow them to damp the 3rd harmonic at specific rpm ranges but that costs hp, which is a trade off Ferrari wasn't willing to make nor where they willing to accept the vibration the V8s where making…..so they spent money on motor mounts that included a better damping system so even thought the engines were rough no one would ever know it and they'd feel like Ferraris
Enzo's acceptance of 8 cylinder engines is still a mystery

I finally learned why 4 cylinder engines vibrate...
At TDC, two pistons are at the top of the bore and two are at the bottom. The CG of all the pistons together is at the midpoint of the stroke.
90 degrees later, all the pistons are lined up, but because of rod angularity, they're actually *BELOW* the midpoint of the stroke.
So the combined CG of the pistons goes from the midpoint of the stroke to just below the midpoint and back twice per revolution.
Because this is a purely vertical motion, it takes a counter-rotating pair of double speed balance shafts to cancel it out.

On a V8, the vibrations of the the two banks are 90 degrees out of phase with each other, resulting in a rotating couple that can be cancelled with a single balance shaft... but that costs power AND weight... so just build better mounts, like you said
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post #15 of 20 Old 09-15-2013, 06:51 AM
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Wil,
I have to admit that I'd never giver the rod angle and mass much thought but that does make sense.
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post #16 of 20 Old 09-15-2013, 07:19 AM
 
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Someone on SpeedTalk explained that one. There are some crazy mofos there.


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On a V8, the vibrations of the the two banks are 90 degrees out of phase with each other, resulting in a rotating couple that can be cancelled with a single balance shaft... but that costs power AND weight... so just build better mounts, like you said
Actually, it's not really a couple. A cross-plane V8 has a rotating couple... it rocks back and forth in a way that rotates with the crankshaft. 90 degree V6's do this a lot worse, though.

Single plane V8's have a "rotating vibration"... not sure what to call it other than that. A single balance shaft could cancel it out, so it's fairly simple.

Flat 4's have an oscillating vertical couple... not sure about flat 6's.

Just about the only engines that don't have some weird vibration are I6's and V12's.
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post #17 of 20 Old 09-15-2013, 07:49 AM
 
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Enzo's acceptance of 8 cylinder engines is still a mystery ... build better mounts ...
Out of curiosity, what is the boxer 12 cyl (e.g. Testarossa) like for vibration?

Thanks all for the explanations as to how the vibration is damped out.

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... the only engines that don't have some weird vibration are I6's and V12's...
My prior love were the glorious BMW i6s. Before owning a Ferrari V8, I was expecting the flat-plane V8 to buzz like crazy. I was shocked at how there is nothing of the sort: there is the flat-plane sound but no vibration.

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post #18 of 20 Old 09-15-2013, 07:58 AM
 
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Out of curiosity, what is the boxer 12 cyl (e.g. Testarossa) like for vibration?

Thanks all for the explanations as to how the vibration is damped out.

My prior love were the glorious BMW i6s. Before owning a Ferrari V8, I was expecting the flat-plane V8 to buzz like crazy. I was shocked at how there is nothing of the sort: there is the flat-plane sound but no vibration.
As Mark said, Ferrari spent a lot more on engine mounts for the 308's than most MFG's are willing to. I'm interested in seeing what the 348 engine mounts are like.

BMW I6's are nice. I had a '92 535i for a couple of years. Really liked it, and the engine was smooth and tractable.

Because the I6 is inherently balanced, any combination of I6 banks is inherently balanced. That includes V12's, flat 12's and the "broad arrow" W18 in Bugatti's 18.4 Chiron concept.
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post #19 of 20 Old 09-15-2013, 09:45 AM
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I will say that I see the new "tripod" configuration to be a weak design. The newer Ferraris and Maseratis using an engine mount on each side and a single transmission mount really use up the mounts. The Lamborghinis and even older Ferraris which used a 4 mount system see a better service life.

It is not a bad design, it is Ferrari's obsession with sourcing the cheapest possible parts from subcontractors that is the problem. The engine mounts in all the cars from the 456, 550,575, Enzo, all 360 and 430 are the same with different rubber compounds to isolate varying degrees of vibration.

It was just a crap design born from frugality.

The trans mount in the 360/430 is the same. Cheap crap. The same idea was used on some of the Mond t/348's but was a better part. Have you ever changed one of those?

I have replaced more of the 456/550/575/Enzo/360/430 engine and transmission mounts than all other engine and transmission mounts in all other Ferrari automobiles combined in my 36 years or Ferrari experience.

Cost cutting, pure and simple.

308 engine mounts last 20 years and never needed a revision.

360 engine mounts last 3 years at the outside and that is the "Improved" version.
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post #20 of 20 Old 09-15-2013, 09:58 AM
 
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Replacement of the mounts makes a car with 20k on the clock feel like brand new again.
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It is not a bad design, it is Ferrari's obsession with sourcing the cheapest possible parts from subcontractors that is the problem. The engine mounts in all the cars from the 456, 550,575, Enzo, all 360 and 430 are the same with different rubber compounds to isolate varying degrees of vibration.

It was just a crap design born from frugality.

The trans mount in the 360/430 is the same. Cheap crap. The same idea was used on some of the Mond t/348's but was a better part. Have you ever changed one of those?

I have replaced more of the 456/550/575/Enzo/360/430 engine and transmission mounts than all other engine and transmission mounts in all other Ferrari automobiles combined in my 36 years or Ferrari experience.

Cost cutting, pure and simple.

308 engine mounts last 20 years and never needed a revision.

360 engine mounts last 3 years at the outside and that is the "Improved" version.
I don't have your depth of experience, but that's what I thought when I read the above about engine mounts being replaced after 20k miles... just inappropriate cost cutting.
There are, after all, a WHOLE LOT of cars on the road with engine mounts that last 5 to 10 times that long.

At least they don't use fluid covered engine mounts like MFG's who field V6's or large 4 cylinder engines do...
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