[DeTomaso] Ford flywheel size and weight????
Corey Price
coreyjprice at gmail.com
Wed Jun 11 13:41:09 EDT 2014
Dan,
Your explanation of engine crank balancing was great. Thanks!
Corey
On Jun 11, 2014, at 10:51 AM, Daniel C Jones <daniel.c.jones2 at gmail.com> wrote:
>> Why are not each component balanced to zero. Then when assembled it
> could be balanced to a small amount to refine it.
> A V-8 has an unbalanced couple that rotates the same direction and
> frequency as the crankshaft.A If you hang the engine from a chain and
> run it with no balance weights on the crank, it will wobble.A A point
> on the front of the engine will travel in a circle, as will a point on
> the rear of the engine, but the middle won't move.A Like holding a
> broom handle in the middle and moving one end in a circle.A The other
> end moves the same but is opposite.
> To balance this, offset weights are needed at the front and rear of the
> crankshaft.A The farther away from the center of the engine and from
> the center of the crankshaft these weights are, the smaller they need
> to be.A If this weight is inside the block, it is considered to be
> internally balanced, if these weights are on the flywheel and front
> pulley, it is externally
> balanced.
> External weights apply their force through the first and last main
> bearing. Moving the weights inside more, means more force is needed,
> but it distributed over more main bearings.A In addition to these
> weights, other weights are placed on the crank to minimize main bearing
> loads.
> Sometimes you will see it claimed that internal balancing is best but
> that's not strictly true.A Splitting the "bob weight" portion of the
> counter-weights between internal and external, both front and rear will
> generally give the lowest crank bending stress.A The "bob" weight is
> best centered about the #1 and #5 bearings. Note that all of this
> applies only to V-8's with 90ADEG cranks.
> A 90ADEG crank V-8 needs a bob weight at each end to balance out the
> motion of the reciprocating masses (pistons, pins, rings, and small end
> weight of the rods).
> The internal/external thing is little more than a question of WHERE
> these two bob weight masses are located.A A Internal takes more weight
> than external and puts out-of-balance couples across the front and rear
> main.A This is most noticed on the front, since the flywheel or
> convertor tend to damp the rear.
> Some external is good but too much is bad.A Ford saved a few lbs of
> mass when they went from 28.2 oz-in to 50 oz-in but it came at a
> price.A With 50 oz-in, the couple across the #1 main on the 5.0L is
> larger than at 28.2 oz-in; in SCCA A Sedan racing, it was common for
> 5.0L cranks to fail at the cheek of the rod throw. While many jump
> straight to internally balanced, 28.2 oz-in seems to be fine for most
> applications, though it is likely dependent upon the RPM being turned.
> Sometimes there isn't enough room to make the throws large enough in a
> casting or forging to internally balance without adding slugs of a
> heavy metal like tungsten.A An example of this is the Ford 428 SCJ
> that required an external hatchet balance weight to offset the heavier
> rods.A
> Dan Jones
>
> On Wed, Jun 11, 2014 at 11:13 AM, Larry - Ohio Time
> <[1]Larry at ohiotimecorp.com> wrote:
>
> Please file this in the stupid questions folder.
> Why are not each component balanced to zero. Then when assembled it
> could be
> balanced to a small amount to refine it.
> Do not understand the principle behind this way of doing balancing.
> Thanks,
> Larry - Cleveland
>
> -----Original Message-----
> From: DeTomaso [mailto:[2]detomaso-bounces at poca.com] On Behalf Of
> Daniel C
> Jones
> Sent: Wednesday, June 11, 2014 11:14 AM
> Cc: De Tomaso List
> Subject: Re: [DeTomaso] Ford flywheel size and weight????
>> He ordered a 347 stroker kit for the 302 and they wanted to know how
> many
> teeth on the flywheel.
> Presumably, they are making an assumption on the imbalance. A All
> 289/302/351W/351C 164 teeth flywheels were 28.2 oz-in, though the same
> flywheel on a 300 I6 was neutral balance. A Later 5.0L's used a 157
> teeth
> flywheel with a 50 oz-in balance factor. A Be aware that some people
> use
> flexplate and flywheel interchangeably. A Though the 5.0L HO used a 157
> teeth flywheel with a T-5 5 speed manual transmission, the same engine
> used
> a 164 teeth flexplate when mated to an AOD automatic overdrive
> transmission.
>> The crank/rods/pistons are the same, regardless of the flywheel.
> Some manufacturers make different kits for different balance factors
> (and
> assumed rod length). The raw forgings are the same but the cranks are
> finish machined to be easily balanced to a particular imbalance and
> bob-weight. A Some of the Scat kits, for instance, are designed to need
> only
> drilling (no Mallory metal) to balance. A Trying to internally balance
> a kit
> designed for 50 oz-in can cost more in Mallory metal and machining than
> the
> crank cost so it pays to know what you are getting. A The manufacturer
> should be able to tell him you imbalance (and even bob-weight) the kit
> was
> designed for. A You want to avoid 50 oz-in unless you plan on keeping
> the
> revs down and need to re-use an existing balancer. A Depending upon the
> kit,
> internal balancing may require a fair bit of mallory metal. 28.2 oz-in
> is
> fine for most uses.
> Be aware that most balancers for 28.2 oz-in require a spacer to work
> with
> the OEM 5.0L HO serpentine belt accessory drive.
> Dan Jones
> On Mon, Jun 9, 2014 at 8:57 PM, Jerry Knotts <[3]knottsj at galstar.com>
> wrote:
>> There are many questions that I can't answer but this one is vexing.
>>
>> A Chrysler motor builder friend of mine is working on a Ford 302 and
> asked
>> me a question about flywheel tooth counts. A He ordered a 347 stroker
> kit
>> for the 302 and they wanted to know how many teeth on the flywheel.
> A He
>> asked me why they needed that information?
>> I fumbled through all my extraneous explanations. A There are 2 major
> tooth
>> configurations 157 and 164 lesser used 148 teeth. A There and 2 major
>> imbalance configurations 28oz and 50oz lesser used 0oz. A Both
> balances
> take
>> a particular harmonic balance that is compatible with the imbalance
> of the
>> flywheel. A Backing plate sizes and starter ends vary by diameter and
> depth
>> for standard and auto trans and flywheel teeth.
>> I finally figured out I have no idea.
>>
>> Is there a concise explanation. A If so what is it.
>>
>> Thanks in advance,
>> jerry knotts
>>
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> References
>
> 1. mailto:Larry at ohiotimecorp.com
> 2. mailto:detomaso-bounces at poca.com
> 3. mailto:knottsj at galstar.com
> 4. mailto:DeTomaso at poca.com
> 5. http://poca.com/mailman/listinfo/detomaso_poca.com
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