Rolly Polly Physics... WAS Re: battery relocation question

[haygood@aemail4u.com (Haygood)]

So I didn't read most of this thread, but ...

>> Insight from knowelegable folks is most welcome.

If you run into any, let me know!

>> > I'm inclined to mount the battery at the front of the spare tire well
>> > (compromise between lowering cm and lowering rotational inertia) is this
>> > correct? However if I wish to lower the rotational inertia more would it be
>> > better to place the battery between the rear shock towers, (closer to the yaw axis).  Or does this stuff matter at all because we are only messing with a small percentage of the total mass?

Sounds good. Yes. Yes. and I have no idea!
For some reason, when I think of driving on ice, I'm inclined to say that rotational inertia is more important to reduce.  Maybe I just have this idea that driving on ice involves a lot more rotation.  If you have studded tires and if you might use power oversteer much of the time, then I think CG wouldn't be as big a deal and avoiding rotational inertia would be.  

I'm happy with mounting the battery in the way-back, because it isn't any higher than it was up front, is only slightly further from front-to-rear CG (and no further from center of the car), and gives the most help to our awful weight distribution.  The nice thing is that weight distribution is helped more because it is a ratio we are tweaking.  I mean, the ideal C.G. height is zero, the ideal I. is zero, and moving the battery isn't going to get you much closer to zero on either account.  The ideal weight distribution is 50/50, and moving further back lowers the first number while raising the last number.  More bang for the buck and a more noticeable improvement.  Still a long way from proving weight distribution is most important, but I'm still of that opinion.

BH

Truth is, any of these places is better than stock.







>> ----- Original Message -----
>> From: "Jason Adams" <roclist@accessconsulting.ca>
>> To: <haygood@aemail4u.com>; "Drew Teague" <roccnroll@hotmail.com>;
>> <rocco_crossing@hotmail.com>; <scirocco-l@scirocco.org>
>> Sent: Wednesday, February 26, 2003 11:58 AM
>> Subject: Rolly Polly Physics... WAS Re: battery relocation question
>>
>>
>> > I meant, "no matter how" as lower the c.g. if you can by whatever means,
>> > i.e. remove sunroof, remove headliner, swap glass to plexi, sit yer fat
>> ass
>> > lower in the car, and if you can mount the battery lower than the stock
>> > position.  All of these actions will lower the c.g. of the car, whether
>> it's
>> > practical, noticable, I won't say. I'm just talking hypothetically here.
>> I
>> > haven't said anything about altering the first moment of inertia here,
>> which
>> > would also occur with any of the afore mentioned actions.  Is it good
>for
>> > this? I don't know. What would be better? Placing the battery as far
>back
>> to
>> > help weight distribution, or closest to c.g. / c.m. to minimize
>rotational
>> > inertia.  This is an important question for me, not saying I know the
>> > answer, as my ice racer experiences large moments as I swing it through
>> the

>> > I'm inclined to mount the battery at the front of the spare tire well
>> > (compromise between lowering cm and lowering rotational inertia) is this
>> > correct? However if I wish to lower the rotational inertia more would it
>> be
>> > better to place the battery between the rear shock towers, (closer to
>the
>> > yaw axis).  Or does this stuff matter at all because we are only messing
>> > with a small percentage of the total mass. BTW, in attempts to lighten /
>> > decrease rotational inertia (yaw axis) i have removed the bumpers.
>> >
>> > Ain't Newtonian mechanics fun....
>> >
>> > Jason Adams
>> > Fahrvergnugen Forever! ;)
>> > 84 rocco 16v
>> > 93 320i
>> > 98 Z71
>> >
>>
>>
>
>
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