gazza285
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| posted on 4/3/07 at 01:53 PM |
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quote:
Originally posted by nitram38
gazza285, in answer to your question about unsprung weight, it has nothing to do with how much the car weighs or pressure exerted by a shock, but
everything to do with how much the wheel, hub, brakes and wishbones weigh.
Unsprung weight is the weight of your suspension and sprung weight is the weight of the rest of the car, chassis etc.
It is much better to have lighter unsprung suspension and slightly heavier sprung weight on the car.
The lighter your suspension, the better it will react to road changes.
Just think of your wheel as a pendulum.
The lighter the mass, the easier it is to move and quicker. If it is heavier, then it is slower.
[Edited on 4/3/2007 by nitram38]
Non of that was disputed. Although I should point out that my shocks exert no pressure on the suspension as mine are designed to control spring
movement, but I'm just being pedantic .
I seem to recall that my question was how does moving the shocks inboard reduce unsprung weight? It was a rhetorical question anyway because it
doesn't, but it does add the weight of the pushrods and bell cranks or the top rocker to the unsprung weight.
Aerodynamic advantage, a little yes, but not enough of one to achieve anything meaningful on a Seven replica, it does allow for adjustments in wheel
movement to spring movement though.
DO NOT PUT ON KNOB OR BOLLOCKS!
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nitram38
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| posted on 4/3/07 at 02:25 PM |
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It only adds the weight of the push rod to the unsprung weight.
The cam and shock are supported by the chassis and are added to the sprung weight.
The push rod weighs a lot less than a shock and spring.
Read Page 25 of "Chassis engineering" by Herb Adams.
I think you are confusing the two terms.
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gazza285
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| posted on 4/3/07 at 02:39 PM |
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As I said, how does it reduce the unsprung weight? The cam is not part of the unsprung weight as it is supported by the chassis? Well so are the
wishbones! If the component moves with the wheel then it is unsprung and adds to the inertia of the suspension travel, hence the moving part of the
shock is added to the unsprung weight as it is unsprung, Half the spring weight is added too as are all links, pushrods and cranks/cams as these are
unsprung. Ask yourself, which side of the spring is it? If its on the chassis side then it is sprung, if not it is unsprung.
Should really be talking about mass not weight as well.
DO NOT PUT ON KNOB OR BOLLOCKS!
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nitram38
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| posted on 4/3/07 at 02:53 PM |
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Your original post asked how it reduced unsprung weight, suggesting that there was none to be gained.
Now you are saying that it is half of the springs etc, which is it?
None or some?
I never said that the amount of weight would be huge, only that it would be better than bothering to drill the brake discs.
The very original post was about reducing unsprung weight by drilling discs.
More weight would be saved on the unsprung weight by moving the shocks/springs inboard.
If there were no benefits to inboard suspension, why do most formula cars now do this? It can't be just aerodynamic gain, because this could be
overcome with aero profiles over the shock/spring.
[Edited on 4/3/2007 by nitram38]
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Deckman001
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| posted on 4/3/07 at 03:00 PM |
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I'd go for ally versions of the hubs you are going to use and also ally versions of the brake calipers, you'll save way more that way than
any drilling of disks 
Jason
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gazza285
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| posted on 4/3/07 at 03:13 PM |
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quote:
Originally posted by nitram38
If there were no benefits to inboard suspension, why do most formula cars now do this? [Edited on 4/3/2007 by nitram38]
It allows aerodynamic improvements and also allows the adjustment of wheel movement to spring movement to be adjusted.
Single seaters are much more aerodynamic than a Seven replica and will benefit from having the shocks out of the airstream, also single seaters have
much longer wishbones, so mounting the shocks to the wishbones becomes much more of a problem, its much easier to use pushrods. The abilily to quickly
change the spring rates without having to actually change the springs, and also the wheel travel to spring travel adjustments are also much easier.
One other thing to consider is that most Formula cars have wishbones that are designed to break away from the chassis in a crash, without damaging the
chassis, having inboard shocks also protects them from damage too.
quote:
Originally posted by nitram38
More weight would be saved on the unsprung weight by moving the shocks/springs inboard.
Explain this bit again. How do you save weight? You still have the shocks, which have one part sprung and one part unsprung, so no difference there,
and have had to add mass of a linkage to the unsprung side to get it to work. It does not reduce unsprung weight in any way.
DO NOT PUT ON KNOB OR BOLLOCKS!
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nitram38
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| posted on 4/3/07 at 03:17 PM |
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You are still confusing sprung and unsprung.
Words like "reduce" and "unsprung" were used in my original post.
My quote that you just used about weight, you should reread.
It said the weight on the unsprung would be reduced. I never said it would reduce sprung weight.
At least you have admitted that there are more gains to be had by moving them! 
Tell me, have you built a car with inboard suspension or are you working from theory?
[Edited on 4/3/2007 by nitram38]
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JoelP
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| posted on 4/3/07 at 03:20 PM |
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Nitram, gazza is correct. It increases unsprung mass. Its been hammered to death many times in the past.
Unspring mass is NOT how much weight your contact patch applies to a pair of bathroom scales. Imagine a hot air balloon - it would at times weight
nothing, but it still has a lot of mass (ie you push and it doesnt move fast).
Unsprung mass is also not the total weight of all moving components. It is about half the wishbones (as only one end moves), exactly half the spring,
the part of the shocker that moves etc.
To accurately represent and compare unsprung mass, you would need to apply a force vertically to the wheel and measure how fast it accelerates upwads,
then work backwards to find a mass. The mass you caluculate would not be the same as the sum of the parts, nor is it the pivot factor.
Imagine a see-saw. If this was actually a heavy top wishbone, and your wheel/tyre/hub had no mass, then you could conclude you have NO unsprung mass
at all, as no weight is being pressed onto your contact patch. However, try moving the rocker and you realise that it would not react at all fast to
bumps.
And if all that doesnt convince you, im not sure what more i can add.
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gazza285
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| posted on 4/3/07 at 03:24 PM |
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quote:
Originally posted by nitram38
You are still confusing sprung and unsprung.
[Edited on 4/3/2007 by nitram38]
Somebody is.
Thank you Joel.
In reply to your other question, my car does have inboard suspension, purely for the sake of it looking cool from the outside.
DO NOT PUT ON KNOB OR BOLLOCKS!
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nitram38
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| posted on 4/3/07 at 03:30 PM |
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Where did the word "mass" suddenly enter the discussion.
I think there is a difference between weight and mass.
At least there was when I went to school!
You are now saying something completely different.
[Edited on 4/3/2007 by nitram38]
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nitram38
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| posted on 4/3/07 at 03:31 PM |
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quote:
Originally posted by scootz
Unsprung Weight... Drilling Brake Disks
Is this a good idea, or am I heading for trouble?
If it's accceptable, then what diameter holes should I be aiming for?
Ta
Here is the original question, don't think mass was mentioned, but unsprung weight was?
[Edited on 4/3/2007 by nitram38]
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gazza285
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| posted on 4/3/07 at 03:39 PM |
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About five posts ago. You do not reduce unsprung weight or unsprung mass, you are adding to both weight and mass, you are still increasing inertia.
Thick of it as a pendulum somebody once told me. The more weight and/or mass you have to move the worse it is, you've got to move the wheel and
stub axle, the wishbones, the pushrods, the crank/cams, the moving portion of the shock and effectively half the spring. Not all count 100% but all
are counted as they all sit on the unsprung end of the suspension.
DO NOT PUT ON KNOB OR BOLLOCKS!
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nitram38
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| posted on 4/3/07 at 03:47 PM |
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quote:
Originally posted by gazza285
About five posts ago.
You started pulling my answer apart long before then. When the question was about unsprung weight.
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JoelP
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| posted on 4/3/07 at 03:48 PM |
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nitram, you're wiggling! Weight is irrelevant. The original poster is simply mistaken by using the term 'unsprung weight', its
totally irrelevant. Mass is all that counts.
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nitram38
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| posted on 4/3/07 at 03:54 PM |
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quote:
Originally posted by JoelP
nitram, you're wiggling! Weight is irrelevant. The original poster is simply mistaken by using the term 'unsprung weight', its
totally irrelevant. Mass is all that counts.
I am wriggling????
Was the question about mass?
I answered based on the question............is there another option I missed?
While we are at it, why don't we check his spark plug gaps, just incase we haven't covered what a misfire might do to inertia
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gazza285
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| posted on 4/3/07 at 04:01 PM |
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quote:
Originally posted by nitram38
quote:
Originally posted by gazza285
About five posts ago.
You started pulling my answer apart long before then. When the question was about unsprung weight.
Only because you were wrong.
DO NOT PUT ON KNOB OR BOLLOCKS!
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JoelP
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| posted on 4/3/07 at 04:11 PM |
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unsprung weight is an oddity. When people refer to unsprung mass or weight, they are on about how well a wheel will react to a bump. To go over a
bump, the wheel needs to be free to move quickly up and down.
There are many ways you could measure unsprung weight, and a low figure would not consistantly get you over a bump well. Equally, a high figure isnt
always bad. Imagine if you attached a lead weight to your wishbone at the outer end, and then slid it in to the inner end. Clearly you would be better
having it at the inner end, where the wheel would have more leverage over it. In this case, unsprung weight (measured as the sum of total moving
parts), would not change, whereas UW measured as the literal weight on the contact patch WOULD change. (im beginning to feel like calvinx with all
these capital letters! )
Also, top rocker suspensions would have an unfair advantage on the contact patch method as the rocker is balanced, but it does still have to move.
Using unsprung mass, measured as i described above, removes all the variations. And though it may sound like a technicality, its an important
difference.
Inboard suspension with pull/push rods does have a significant advantage in F1, as drag at 200mph is crucial. Also, using carbon parts, the weight
isnt much affected. And total weight is irrelevant, since they all have to carry lead ballast to reach minimum weights (iirc, ferrari had 100kgs of
ballast one year).
Sorry if you have taken this as a personal attack, its not, i just feel the need to get involved in good discussions 
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nitram38
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| posted on 4/3/07 at 04:17 PM |
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Nothing taken personally, through discussion, we might all learn something. But it would appear we are talking about two different things. Mass and
weight.
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Tripnut
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| posted on 5/3/16 at 02:30 PM |
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Hmmm.
I have been fiddling with racing motorcycles for years and years so think I can cut through some of the bulls*^$" on the subject of brakes and
unsprung weight:
Unsprung weight should be seen as a percentage of unsprung to sprung weight. On a car drilling the discs will make no noticeable difference, on a
lightweight racing motorcycle the better ratio can make the difference between winning and losing.
Now to the reasons for drilling discs:
I have never noticed any increase or decrease in braking performance in the dry between drilled or solid discs, the reasons are simple:
If the clamping force is the same in both instances and the system uses the same pads etc the pads will be clamped at a lower force per square cm with
undrilled discs but the surface area is larger, again this ratio is constant. Take away surface area and keep the clamping force the same you get an
increase in pressure per square cm. This means you have a constant ratio so all things being equal and as long as you don't take this to
it's logical conclusion (be sensible) it should make no difference.
Cooling:
Yes you do increase total surface area by drilling the discs but the increase is in an area with lower useful surface because it's out of the
direct airflow so drilling the discs should make little difference. lowering the volume of the disc will also remove some of it's ability to act
as a heat sink so during braking it could overheat on the surface and between corners it could actually cool down to below its ideal temperature to
bite reliably on initial application.
The only time disc drilling seems to be worthwhile is on a motorcycle in wet weather, car discs are fairly well protected in comparison and generally
made from micro porus cast iron which is too heavy (and rusty) for motorcycles which usually have thinner stainless steel rotors on display. The move
from cast iron to stainless steel on motorcycles in the 70's is when disc drilling started and it was due to the lack of wet weather performance
with the stainless steel discs not cooling or weight. Please read any motorcycle magazine with road tests in the early 70's.
On a motorcycle with stainless discs the pads can literally aquaplane over the surface of the disc, drilling is like having treaded as opposed to
slick tyres. The water needs somewhere to go!!
I have two Kawasaki H2 750 motorcycles from the early 70's, one with drilled discs which gets used if the weather looks dodgey and a nearly
concours version which has solid original SS discs and never sees rain. The rain bike was lethal in the wet until I got the discs drilled Quod Erat
Demonstrandum.
The above is what is true in my little quantum universe. Please feel free to ignore the truth and continue arguing.
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UncleFista
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| posted on 5/3/16 at 04:17 PM |
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quote:
Originally posted by Tripnut
Please feel free to ignore the truth and continue arguing.
I think the argument will probably be over with, seeing as the post you're replying to is just about 9 years old
Tony Bond / UncleFista
Love is like a snowmobile, speeding across the frozen tundra.
Which suddenly flips, pinning you underneath.
At night the ice-weasels come...
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jeffw
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| posted on 5/3/16 at 04:53 PM |
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hahahahahahahahah
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redturner
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| posted on 6/3/16 at 09:03 AM |
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FWIW, I cross drilled all the discs on my single seater racing which is only now used for hill climbs and sprints and the brakes are now far better
than when undrilled. I marked the discs with a template that I had made and drilled the 1/4" holes using a pillar drill. The car weighs 520Kgs
with me on board. They have not been balance but I dont have a inbalance problem. The pads were removed at the end of the season and yes, they were
worn more than usuall, but given that I was more than happy with the improved braking I was more than happy to put a new set of pads in.....
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