 |
|
| View previous topic :: View next topic |
| Author |
Message |
Andrew (AJ) Weber
Joined: 18 Mar 2003
Posts: 599
|
 Posted: Sun Nov 06, 2005 11:06 am Post subject: Re: axles |
 |
|
| Kevin Willmorth wrote: |
I know what your saying, and struggle with it as well. However, after a great deal of conversation and discussion with people who do mechanical and materials engineering for a living - some in auto racing, none in karting, I have found not one single bit of evidence to show that what is being claimed with all the "hardness" numbers means anything at all. I can't even find anyone who can explain what the "hardness" numbers even mean in real terms. CRG ranges from 60 to 250, which is incredible. Are they actually saying that the range from hard to soft is 400%? Birel ranges from 335 to 769 - obviously on some scale of their own, indicating what?
|
That would be great if they could quantize whatever it is they are really selling. Like
I said many pages back; I TRIED to prove to myself on the track that all that mattered
was geometry (length, radius, thickness), but at a 1:07 track I can repeat laptimes
within a tenth at I DID have significant behavioral change with axles of the same
geometry but different 'advertised hardness' (S20 vs. M20 and S25 vs. T1).
So this 'hardness' metric is not just some marketing trick to sell more axles. I really
thought it was at that time, following these same elasticity lines of thought, and
the irrelevence of hardness in elastic behavior, but it isn't. Axles with different
'advertised hardness' and the same geometry do differ.
Someone else said something way back that I think is close to the real truth. These
kart manufacturers are not really that big in modern industrial terms, and they
probably just have axles made up from all kinds of steels and just test them. Ones
that work, they name, manufacter, and sell. At that point maybe they noticed
that among all the characteristics these steels differ on, hardness is the easiest for
them to test (hardness testing is pretty easy). So hardness may not be the property
that makes a difference in kart performance, but it may be a property that is different
among the axles steels and maybe has some correlation with whatever does make the
difference (like the suggested damping). |
|
| Back to top |
|
 |
Mike Goebel
Joined: 28 Jul 2001
Posts: 5765
Location: United States, California, Winnetka
|
| Posted: Sun Nov 06, 2005 11:30 am Post subject: Re: axles |
|
|
| Andrew (AJ) Weber wrote: |
That would be great if they could quantize whatever it is they are really selling. Like
|
I think to a certain extent they do. They make an axle of a certain steel, hardness, whatever, go out and test and if the axle makes the kart freeer in a sticky situation they say they axle is softer since that is what they expect form a” softer" axle. Then do another test where the axle added grip and say the axle is harder. But we all know from engineering that the axle can't be all that different in stiffness do to differences in material. But the axles do actually behave differently and can be used for tuning. Unfortunately for me I haven't figured out the tuning part. Yet.
Mike G. |
|
| Back to top |
|
|
joseph hollinger
Joined: 12 Sep 2002
Posts: 9483
Location: United States, California, san francisco
|
| Posted: Sun Nov 06, 2005 12:14 pm Post subject: |
|
|
| Ray Foster wrote: |
WHAT?!?!?!?!
Joseph, the diameter of the tire has nothing to do with the moment arm of the axle. It's the ENGINE that is trying to accelerate the axle, NOT the tire. The ENGINE is trying to accelerate the tire, wheel, axle, clutch, sprocket, brake rotor, etc. and anything else that is attached to it. The size of the tire doesn't effect the moment arm of the axle. The weight and moment arm of the tire/wheel combination will effect the inertia of the tire/wheel combination and will effect how the kart accelerates and decelerates. |
I knew I should have been more rigorous. I'm not trying to say that
the radius of the tire effects the moment arm of the axle. What I am
trying to say is that you can use that radius to normalize other radii.
Look at it this way: every rotating component has two
forms of inertia: linear and rotational. For masses at the center of the
axle's rotation, the rotational part is very small. For masses at the
radius of the tire, the rotational and linear inertias (or momentums)
are equal. So if you divide the moment arm of any component by
the radius of the tire you can express the rotational inertia of that
component in terms of it's linear inertia.
Make sense? |
|
| Back to top |
|
|
Larry Andrews
Joined: 13 May 2002
Posts: 2848
Location: United States, California, SC Mtns
|
| Posted: Sun Nov 06, 2005 9:28 pm Post subject: |
|
|
Joe, I think what you're trying to say is that compared to the combined moment arm of the tire, rims and brake rotor; the difference in the moment arm of the two axles is trivial. That's an easy calculation.
Of course, you too now must have a very sore forehead from trying to have a logical discussion with Paul. |
|
| Back to top |
|
|
|
|
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
|
Go Top
|
FAQ
Search
Memberlist
Usergroups
Register
Profile
Login to check your private messages
Login
