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Another Flatty tech question...

Discussion in 'The Hokey Ass Message Board' started by 3blapcam, Sep 17, 2004.

  1. 3blapcam
    Joined: Jul 15, 2004
    Posts: 526

    3blapcam
    Member
    from Austin, TX

    Ford V8 Flatty question that is...

    How do these motors run without a harmonic balancer? Do they not spin enough RPM's to be concerned?

    It doesn't make sense to me - and the only guess I would have is that they hadn't designed them yet or designed them into the build.

    Curious minds want to know.

    Alec.
     
  2. mtflat
    Joined: Jan 28, 2003
    Posts: 422

    mtflat
    Member

    internal balance, and they run the same rpms any other engine does
     
  3. Bruce Lancaster
    Joined: Oct 9, 2001
    Posts: 21,682

    Bruce Lancaster
    Member Emeritus

    On the internal balance, compare the weights on the Ford to an SBC--more stuff, better distributed, bigger.
    Early SBC's had forged cranks with no center weights due to the difficulties of forging there. They had no balancers in their early years--and racers had to weld on center weights to get a truly stable assembly for high RPM--this was actually a routine mod for seriously raced Chevies.
     
  4. 3blapcam
    Joined: Jul 15, 2004
    Posts: 526

    3blapcam
    Member
    from Austin, TX

    Thanks mtflat and Bruce...

    I've seen a lot of internally balanced race motors from the machine shop my buddy works at, but they still have balancers on them. I'll have to agree that the flatty has very large counter weights compared to later model engines. And, I'll have to take that as my answer even though that may take a while to sink in fully.

    Alec.
     

  5. Deuce Rails
    Joined: Feb 1, 2002
    Posts: 2,016

    Deuce Rails
    Member

    [ QUOTE ]
    internal balance, and they run the same rpms any other engine does

    [/ QUOTE ]

    Won't a SBC be able to turn more rps than a flathead?

    What's the max rpm you flathead guys are seeing?
    Do you get valve float like you would in a monkey-motion OHV motor?
     
  6. 3blapcam
    Joined: Jul 15, 2004
    Posts: 526

    3blapcam
    Member
    from Austin, TX

    [ QUOTE ]

    Won't a SBC be able to turn more rps than a flathead?

    What's the max rpm you flathead guys are seeing?
    Do you get valve float like you would in a monkey-motion OHV motor?

    [/ QUOTE ]

    I would think that valve float could be a problem, but you don't have to worry as much about piston and valve coming together. That's what breaks valves and pistons. You just have to worry about the valve hitting the cyl. head - but I don't know what the clearence is there. OHV Piston to valve clearence (hopefully) is no less than 0.075".

    That's my 2 cents worth. I haven't built my flatty yet, but my expectations are that it won't be as big of a deal when it comes to valve spring pressures and floating valves.

    Alec.
     
  7. Hot Rod To Hell
    Joined: Aug 19, 2003
    Posts: 3,032

    Hot Rod To Hell
    Member
    from Flint MI

    One thing to consider is the fact that a "harmonic balancer" is not actually a balancer at all in many applications. It's actually a harmonic DAMPENER, meaning it lessens the harmonics that the crankshaft (and therefore the cam, valvetrain, and distributor) sees.

    I would guess that was just technology that hadn't been engineered yet at the time of the flatty.
     
  8. 3blapcam
    Joined: Jul 15, 2004
    Posts: 526

    3blapcam
    Member
    from Austin, TX

    Hot Rod To Hell - That's what I was kind of getting at. My buddy who studied Mech. Eng. was telling me about Harmonics and how important the 'dampener' is to the engine. He's a gear head also, so it's something that he was thinking about as he was studying it.

    But, since the flatty didn't have a dampener, I figured it could get away with it if it only spun to about 4500 RPM's. It's greek to me.

    Alec.
     
  9. Digger_Dave
    Joined: Apr 10, 2001
    Posts: 2,517

    Digger_Dave
    Member

    [ QUOTE ]
    One thing to consider is the fact that a "harmonic balancer" is not actually a balancer at all in many applications. It's actually a harmonic DAMPENER, meaning it lessens the harmonics that the crankshaft (and therefore the cam, valvetrain, and distributor) sees.

    I would guess that was just technology that hadn't been engineered yet at the time of the flatty.

    [/ QUOTE ]

    Mike Davidson, (the Aussie flathead guru; owner of Flatattack) discovered that flathead engines benefited (less vibration) with the use of a HARMONIC DAMPENER.

    I have been studying the types available and several companies make them for flatheads. I intend to use one on my new engine.
     
  10. Bruce Lancaster
    Joined: Oct 9, 2001
    Posts: 21,682

    Bruce Lancaster
    Member Emeritus

    On RPM--the flathead lower end is capable of revving far beyond the breathing limits of the engine, which expire close to 4000 on a stocker and maybe 5 on a hot one.
    Supposedly the genesis of the Ardun was here--Duntov discovered on long downhill high speed runs that his '37 Ford smuggling car would reliably rev beyond the limits of his DOHC racecar (an Amilcar or something). He began to think about adding some breathing to take advantage of the top end potential...
     
  11. disastron13
    Joined: Sep 22, 2002
    Posts: 332

    disastron13
    Member

    Starting in the early thirties smoothness was a big advertising point for car makers, Buick eights, motors like that, were designed to be smooth and silent.
    Crank counterweight design and massive block castings did the job- on a Buick or Packard eight, you can hardly tell if the engine is running by looking at it. Set your beer on the rocker cover of the Buick and it won't walk off.
    No one would want a silent car anymore-the very idea is insane now- and CAD designed rubber motor mounts and dampers do the job of preventing the driver from feeling engine vibration.
    If everything else (breathing) was equal the flatty could rev higher than on OHV motor because of less reciprocating valve train weight, right?
    I think it is really cool when you see at one a them classic car meets a big black Caddy or Packard sedan move silently along, no sound at all except the tires on the pavement.
     
  12. 3blapcam
    Joined: Jul 15, 2004
    Posts: 526

    3blapcam
    Member
    from Austin, TX

    Bruce and disastron... I was unaware of those facts. I like hearing that kind of stuff, keep it coming.

    You guys are going to get tired of my questions, but... this may sound odd, weird or stupid to you, but has anyone tried making roller cams and lifters for a flatty? I would think there would be easy horsepower and torque to be had there. I think the offset of R&D cost would prohibit its production.

    The stuff I dream about while at work...

    Alec.
     
  13. Digger_Dave
    Joined: Apr 10, 2001
    Posts: 2,517

    Digger_Dave
    Member

    I borrowed this article (stole!) from a tech site.

    Although it refers to modern day engines, it's applicable to flathead engines as well. Particularly those that have had serious modifications made to the bottom end.

    Understanding the Harmonic Damper
    & The Danger of Power Pulleys





    BY STEVE DINAN OF DINAN BMW

    I have been threatening for a long time to write a series of technical articles to educate consumers and to dispel misconceptions that exist about automotive after-market technology. Motivated by problems with customer's cars resulting from the installation of power pulleys, I wish to explain the potential dangers of these products and address the damage they cause to engines.The theory behind the power pulley is that a reduction in the speed of the accessory drive will minimize the parasitic losses that rob power from the engine.

    Parasitic power losses are a result of the energy that the engine uses to turn accessory components such as the alternator and water pump, instead of producing power for acceleration. In an attempt to minimize this energy loss, many companies claim to produce additional power by removing the harmonic damper and replacing it with a lightweight assembly. While a small power gain can be realized, there are a significant number of potential problems associated with this modification, some that are small and one which is particularly large and damaging!

    The popular method for making power pulleys on E36 engines is by removing the harmonic damper and replacing it with a lightweight alloy assembly. This is a very dangerous product because this damper is essential to the longevity of an engine. The substitution of this part often results in severe engine damage.It is also important to understand that while the engine in a BMW is designed by a team of qualified engineers, these power pulleys are created and installed by people who do not understand some very important principles of physics. I would first like to give a brief explanation of these principles which are critical to the proper operation of an engine.

    1) Elastic Deformation
    Though it is common belief that large steel parts such as crankshafts are rigid and inflexible, this is not true. When a force acts on a crank it bends, flexes and twists just as a rubber band would. While this movement is often very small, it can have a significant impact on how an engine functions.

    2) Natural Frequency
    All objects have a natural frequency that they resonate (vibrate) at when struck with a hammer. An everyday example of this is a tuning fork. The sound that a particular fork makes is directly related to the frequency that it is vibrating at. This is its "natural frequency," that is dictated by the size, shape and material of the instrument.

    Just like a tuning fork, a crankshaft has a natural frequency that it vibrates at when struck. An important aspect of this principle is that when an object is exposed to a heavily amplified order of its own natural frequency, it will begin to resonate with increasing vigor until it vibrates itself to pieces (fatigue failure).

    3) Fatigue Failure
    Fatigue failure is when a material, metal in this case, breaks from repeated twisting or bending. A paper clip makes a great example. Take a paper clip and flex it back and forth 90° or so. After about 10 oscillations the paper clip will break of fatigue failure.The explanation of the destructive nature of power pulleys begins with the two basic balance and vibration modes in an internal combustion engine. It is of great importance that these modes are understood as being separate and distinct.
    1) The vibration of the engine and its rigid components caused by the imbalance of the rotating and reciprocating parts. This is why we have counterweights on the crankshaft to offset the mass of the piston and rod as well as the reason for balancing the components in the engine.
    2) The vibration of the engine components due to their individual elastic deformations. These deformations are a result of the periodic combustion impulses that create torsional forces on the crankshaft and camshaft. These torques excite the shafts into sequential orders of vibration, and lateral oscillation. Engine vibration of this sort is counteracted by the harmonic damper and is the primary subject of this paper.

    4. Torsional Vibration (Natural Frequency)

    Every time a cylinder fires, the force twists the crankshaft. When the cylinder stops firing the force ceases to act and the crankshaft starts to return to the untwisted position. However, the crankshaft will overshoot and begin to twist in the opposite direction, and then back again. Though this back-and-forth twisting motion decays over a number of repetitions due to internal friction, the frequency of vibration remains unique to the particular crankshaft.This motion is complicated in the case of a crankshaft because the amplitude of the vibration varies along the shaft. The crankshaft will experience torsional vibrations of the greatest amplitude at the point furthest from the flywheel or load.

    5. Harmonic (sine wave) Torque Curves

    Each time a cylinder fires, force is translated through the piston and the connecting rod to the crankshaft pin. This force is then applied tangentially to, and causes the rotation of the crankshaft.The sequence of forces that the crankshaft is subjected to is commonly organized into variable tangential torque curves that in turn can be resolved into either a constant mean torque curve or an infinite number of sine wave torque curves. These curves, known as harmonics, follow orders that depend on the number of complete vibrations (cylinder pulses) per revolution.

    Accordingly, the tangential crankshaft torque is comprised of many harmonics of varying amplitudes and frequencies. This is where the name "harmonic damper" originates.

    6. Critical RPM's

    When the crankshaft is revolving at an RPM such that the torque frequency, or one of the harmonic sine wave frequencies coincides with the natural frequency of the shaft, resonance occurs. Thus, the crankshaft RPM at which this resonance occurs is known a critical speed. A modern automobile engine will commonly pass through multiple critical speeds over the range of its possible RPM's.

    These speeds are categorized into either major or minor critical RPM's.

    7. Major and Minor Critical RPM’s

    Major and minor critical RPM's are different due to the fact that some harmonics assist one another in producing large vibrations, whereas other harmonics cancel each other out. Hence, the important critical RPM’s have harmonics that build on one another to amplify the torsional motion of the crankshaft. These critical RPM’s are know as the "major criticals". Conversely, the "minor criticals" exist at RPM's that tend to cancel and damp the oscillations of the crankshaft.

    If the RPM remains at or near one of the major criticals for any length of time, fatigue failure of the crankshaft is probable.

    Major critical RPM’s are dangerous, and either must be avoided or properly damped. Additionally, smaller but still serious problems can result from an undamped crankshaft. The oscillation of the crankshaft at a major critical speed will commonly sheer the front crank pulley and the flywheel from the crankshaft.

    I have witnessed front pulley hub keys being sheered, flywheels coming loose, and clutch covers coming apart. These failures have often required crankshaft and/or gearbox replacement.

    HARMONIC DAMPERS

    Crankshaft failure can be prevented by mounting some form of vibration damper at the front end of the crankshaft that is capable of absorbing and dissipating the majority of the vibratory energy. Once absorbed by the damper the energy is released in the form of heat, making adequate cooling a necessity.

    This heat dissipation was visibly essential in Tom Milner's PTG racing M3 which channeled air from the brake ducts to the harmonic damper, in order to keep the damper at optimal operating temperatures.

    While there are various types of torsional vibration dampers, BMW engines are primarily designed with "tuned rubber" dampers. It is also important to note that while the large springs of a dual mass flywheel absorb some of the torsional impulses conveyed to the crankshaft, they are not harmonic dampers, and are only responsible for a small reduction in vibration.

    In addition to the crankshaft issue, other problems can result from slowing down the accessories below their designed speeds, particularly at idle. Slowing the alternator down can result in reduced charging of the battery, dimming of the lights, and computer malfunctions.

    Slowing of the water pump and fan can result in warm running,

    (I highlighted this for the flathead lovers!) while slowing of the power steering can cause stiff steering at idle and groaning noises.

    It is possible to implement design corrections and avoid these scenarios, but this would require additional components and/or software.Our motto at Dinan is "Performance without sacrifice" We feel our customers expect ultra high performance along with the legendary comfort and reliability of a standard BMW.While it is common that a Dinan BMW is the fastest BMW you can buy, performance is not our only goal. Dinan isn't just trying to make the fastest car. Instead a host of considerations go into the development of our products. Dinan puts much more effort into these other areas than does our competition.These considerations are Performance, Reliability (Warranty), Driveability, Emissions, Value, Fit and Finish. We feel that the power pulley is a bad way to get extra power from and engine and the potential for serious engine damage is too great.This is a simplified explanation meant to be comprehensible by those who are not automotive engineers. In trying to simplify an extremely complex topic some precision was sacrificed although we believe this explanation to be as accurate as possible. We encourage our customers to educate themselves and understand the automotive after-market because we believe that our products are the best researched, engineered, and fabricated products available.For those interested in a more in depth and technical explanation of this topic, the reference book is Advanced Engine Technology, written by Heinz Heisler MSc,BSc,FIMI,MIRTE,MCIT. Heinz Heisler is the Head of Transportation Studies at The College of North West London. His book is distributed in this country by the SAE (Society of Automotive Engineers).
     
  14. Digger_Dave
    Joined: Apr 10, 2001
    Posts: 2,517

    Digger_Dave
    Member

    [ QUOTE ]
    ... this may sound odd, weird or stupid to you, but has anyone tried making roller cams and lifters for a flatty? I would think there would be easy horsepower and torque to be had there. I think the offset of R&D cost would prohibit its production.

    Alec.

    [/ QUOTE ]

    Alec, there were/are several cam grinders that offer(ed) ROLLER CAMS and LIFTERS for flathead engines.

    They required a KEYWAY to be machined in the lifter bores to match a keyway on the lifters to keep them aligned.

    They wore out quickly and were usually only used for racing.
     
  15. av8
    Joined: Mar 3, 2001
    Posts: 1,716

    av8
    Member

    HRH -- You've got it, almost. It's a harmonic DAMPER, also called a torsional damper. Here's Fluidampr's simple, easy-to-understand explanation of its function . . .

    Crankshaft Deflection - The Invisible Enemy
    Each time the air/fuel mixture inside a cylinder is ignited, the combustion that results creates a torque spike - an extremely rapid rise in cylinder pressure. This pressure, applied to the top of the piston, becomes the force that is applied to the crankshaft through the connecting rod. Each torque spike is like a hammer blow. In fact, it hits with sufficient intensity that it not only causes the crankshaft to turn, it actually deflects or twists it. This twisting action and the resulting rebound (as the crank arm snaps back in the opposite direction) is known as torsional harmonic vibration. If not adequately controlled, torsional vibration causes rapid main bearing and main journal wear and possible crankshaft breakage.

    Keeping Vibration in Check
    Fortunately, harmonic vibration can be controlled by a vibration damper - which is also called a harmonic damper or erroneously a "harmonic balancer". The main purpose of a "harmonic damper" is to control harmonic vibration, not necessarily to balance the engine's rotating assembly.
     
  16. 3blapcam
    Joined: Jul 15, 2004
    Posts: 526

    3blapcam
    Member
    from Austin, TX

    Section 2 is what I was talking about. Very good article. I guess no one has had these problems with flatty's? I think I might run a damper when it comes to rebuild - it just seems like the best thing to do.

    I guess this:
    Sect. 3-1) The vibration of the engine and its rigid components caused by the imbalance of the rotating and reciprocating parts. This is why we have counterweights on the crankshaft to offset the mass of the piston and rod as well as the reason for balancing the components in the engine.

    is what helps the flatty from coming apart. Large counterweights? Does anybody build the cranks with lightweight counterweights and other tricks to keep mass down? I know I am probably beating a dead horse here - I'm sure other people have thought about all this stuff over the past 50-60-70 years... I'm just curious.

    Alec.
     
  17. 3blapcam
    Joined: Jul 15, 2004
    Posts: 526

    3blapcam
    Member
    from Austin, TX

    That's awesome - I want one! No, two. A blower grind and a NA grind. Who made them do you know?

    Alec.
     
  18. Oilcan Harry
    Joined: Mar 3, 2001
    Posts: 906

    Oilcan Harry
    Member
    from INDY

    There is no reason to rev a street Flatty past 5000 and really 4500 makes more sense. They won't make anymore power just expensive noises. Remember there are only 3 main bearings in there and the center one takes all the abuse of 4 cylinders! Its quite common to find cracked center mains on engines reved hard, so treat it with some kindness.
     
  19. Digger_Dave
    Joined: Apr 10, 2001
    Posts: 2,517

    Digger_Dave
    Member

    [ QUOTE ]
    HRH -- You've got it, almost. It's a harmonic DAMPER, also called a torsional damper. Here's Fluidampr's simple, easy-to-understand explanation of its function . . .

    [/ QUOTE ]

    Gee Mike, you found the simplified explanation!

    [ QUOTE ]
    Crankshaft Deflection - The Invisible Enemy
    Each time the air/fuel mixture inside a cylinder is ignited, the combustion that results creates a torque spike - an extremely rapid rise in cylinder pressure. This pressure, applied to the top of the piston, becomes the force that is applied to the crankshaft through the connecting rod. Each torque spike is like a hammer blow. In fact, it hits with sufficient intensity that it not only causes the crankshaft to turn, it actually deflects or twists it. This twisting action and the resulting rebound (as the crank arm snaps back in the opposite direction) is known as torsional harmonic vibration. If not adequately controlled, torsional vibration causes rapid main bearing and main journal wear and possible crankshaft breakage.

    [/ QUOTE ]

    This is where the flathead runs into trouble. It only has THREE main bearings! Not FIVE like most modern V8's

    [ QUOTE ]
    Keeping Vibration in Check;

    Fortunately, harmonic vibration can be controlled by a vibration damper - which is also called a harmonic damper or erroneously a "harmonic balancer". The main purpose of a "harmonic damper" is to control harmonic vibration, not necessarily to balance the engine's rotating assembly.

    [/ QUOTE ]

    Flatheads have massive counter weights to offset reciprocating loads. Add the fact they are long stroke and then you start to realize why they aren't high reving engines.

    BUT they are capable of LOADS of low RPM tourqe.

    Mike, didn't Crower make a roller cam for flatheads?

    The idea of a roller cam was to be able to achieve full lift of the valve as quickly as possible.

    A flat lifter needs more of a slope on the cam lobe. The taper of the cam lobe would slow down the lift. (opening speed of the valve)
     
  20. fullhouse296
    Joined: Jan 30, 2009
    Posts: 396

    fullhouse296
    Member
    from Australia

    Crower make a inverse radius roller lifter set and the specail cam to go with it .Even a reverse flow design if reqd ! Say goodbye to 3 grand, just there ! Timewarp racing in Australia uses one of these and pulls 8.5 secs all day .he also uses a 5 main bearing crank .
     
  21. Bruce Lancaster
    Joined: Oct 9, 2001
    Posts: 21,682

    Bruce Lancaster
    Member Emeritus

    Counterweights: Lay a flathead crank (post 1933) next to a forged Chevy SBC...the Chevy is missing 2 counterweights to simplify forging process...racers in the '50's and '60's spent a lot of $$ welding them where they were needed. This is one of the reasons here...
    Yes, racers did lighten reciprocating parts and cut away counterweights to match or even beyond that. You can see a pictorial of lightening a flathead crank at Ansen in one of the Fawcett books.
     
  22. The RPM part is basically untru, I regularly spin my small block to 7K. I guess they spin the same RPM as any other flatty.

    The real answer to the question is that harmonics were not a major concern to Henry. Building and selling cars to the masses were a major concern to Henry.
     
  23. Flat Ernie
    Joined: Jun 5, 2002
    Posts: 8,406

    Flat Ernie
    Tech Editor

    There are several kits to adapt SBC dampers to the flatty...so someone is concerned about it. ;)
     

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