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Ray Foster
Joined: 16 Oct 2005
Posts: 16
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 Posted: Fri Nov 04, 2005 10:59 am Post subject: |
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Mr. Slattery,
Arrow karts with 50mm axles are allowed in the WKA ICA, ICC and 80cc shifter classes..
How have the Arrow karts done against the Birels, Kosmic, and 1st Karts in those 50mm classes?
Didn't Joey King win the WKA Formula Y Sr. National Championship with a Margay? I think he won every race, didn't he?
I know that between Harraka's KRT's and Reeves and Nelson's Margays, they pretty much dominated the 40mm classes.
How many National races did the Arrow karts win, with either the 40mm or 50mm axles assemblies?
Just curious.
Thanks.
Ray |
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Larry Andrews
Joined: 13 May 2002
Posts: 2852
Location: United States, California, SC Mtns
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| Posted: Fri Nov 04, 2005 11:45 am Post subject: |
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| Just can't resist, can ya? |
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patrick slattery
Joined: 23 Apr 2004
Posts: 789
Location: United States, Ohio, cleves
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| Posted: Fri Nov 04, 2005 1:43 pm Post subject: |
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Paul if you will read the posts, not pushing 50mm axles just debating the weight, of said axle. Do you think Mr. King would be able to win with an Arrow?
Pat |
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Andrew Kidd
Joined: 02 Sep 2004
Posts: 3954
Location: United States, California, Mountain View
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| Posted: Fri Nov 04, 2005 4:12 pm Post subject: |
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Kevin, remember that the only piece that actually spins is half the bearings and the axle. The cassettes and most of the bearing doesn't spin around.
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Cameron Karting - 707.938.9986 - www.cameronkarting.com
My opinions are not shared by any of the businesses I may represent. |
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Mike Goebel
Joined: 28 Jul 2001
Posts: 5794
Location: United States, California, Winnetka
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| Posted: Fri Nov 04, 2005 5:33 pm Post subject: |
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G |
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Kevin Willmorth
Joined: 17 Oct 2004
Posts: 1160
Location: United States, Wisconsin,
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| Posted: Fri Nov 04, 2005 8:28 pm Post subject: |
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Using an ugly thing called Math:
Steel weights .238 pounds per cubic inch, 1 cubic mm = 0.00061 cubic inches, so:
50mm x 2.5mm tube = 79639.373 cubic mm of material which weighs 11.567 pounds
40mm x 3mm tube = 75473.622 cubic mm of material which weighs 10.962 pounds
Can’t fight the volume and mass thing, it’s just reality.
HOWEVER:
Since the 50mm axle has a larger beam section, it will be stiffer for any wall thickness - so the question becomes: What wall thickness is required for the 50mm axle to produce the same stiffness characteristic as the 40mm x 3mm tube?
Let's use section modulus to find the answer:
40 x 3mm tube = 1680.306 section modulus
50 x 2.5mm tube = 2272.298 section modulus
The two axles are not equal in stiffness, so the weight comparison is invalid.
To get the 50mm to equal the 40mm tube, the wall thickness would have to be reduced to 1.75mm, producing a section modulus of 1627.045 – slightly softer than the 40mm, by a hair.
The 50mm x 1.75mm axle = 56176.389 cubic mm of material which weighs 8.16 pounds
NOW we're talking about a weight difference! This supports the contention that for equal stiffness, the 50mm axle is lighter, by a fair amount actually (about 34%.) Makes sense, and is supportable.
More important to ME, I now understand why the 50mm axle was not working for us - it was much stiffer compared to the 40mm axle, too stiff in fact. By moving to the 40mm x 3mm axle, from that 50mm x 2.5mm axle, we dropped the section modulus by 35%, which is significant enough to gain the improvement we were seeking.
I can now sleep again.
So, Doug, so what's up with the Pro Axles you mentioned? Seems a 50mm x 1.5mm axle is in order?
This was fun - in a sick geeked-out sort of way.  |
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Tommy Griffith
Joined: 24 Sep 2005
Posts: 16
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| Posted: Fri Nov 04, 2005 8:32 pm Post subject: |
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| patrick slattery wrote: | 40MM is what most Domestic models race , and 50mm is what most European karts are designed for. In WKA most classes have to run 40MM due to pressure from the domestice mfg.
Pat Slattery |
Pat Slattery,
What do you mean: "Due to pressure for the Domestic mfg."?
Are you saying that Margay is stopping WKA form allowing 50mm axles in all classes?
I have been told by my WKA Trustee that WKA has simply chosen to follow their Rule Book and not cave in to pressure from the European chassis companies who chose to ignore the WKA rules that clearly stated the legal axle size.
Once the WKA Board failed to come up with even one way that 50mm axles made karting better, the decision to continue to ban them was clear and simple.
Why are 50mm axles needed? Can't the European chassis beat the American chassis on equal footing: i.e. with 40mm axles?
If I understand you correctly, you are saying that we should allow the Europeans to dictate what rules we race under, just because thay can't win under our existing rules. Why do you feel that way?
Should we change our water quality standards so that the Montezuma Water Company of Mexico can sell their water here?
Should we lower our U.S.D.A. beef quality standards so that the Europeans can sell their Mad Cow beef here?
How many 40mm axles have failed? Thereby necessitating the switch to 50mm axles? I mean, 40mm axles must be failing for there to be this dire need to allow 50mm axles. Right?
How much money will the average karter save by switching to 50mm axles? |
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joseph hollinger
Joined: 12 Sep 2002
Posts: 9532
Location: United States, California, san francisco
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| Posted: Fri Nov 04, 2005 10:03 pm Post subject: |
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| Kevin Willmorth wrote: | Using an ugly thing called Math:
Steel weights .238 pounds per cubic inch, 1 cubic mm = 0.00061 cubic inches, so:
50mm x 2.5mm tube = 79639.373 cubic mm of material which weighs 11.567 pounds
40mm x 3mm tube = 75473.622 cubic mm of material which weighs 10.962 pounds
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Wow, that seems really heavy. Did you use D when you meant R? |
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Mike Goebel
Joined: 28 Jul 2001
Posts: 5794
Location: United States, California, Winnetka
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| Posted: Fri Nov 04, 2005 11:46 pm Post subject: |
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| Kevin Willmorth wrote: | Using an ugly thing called Math:
D |
Damn math that's a good idea. Who did it for you 
Mike G. |
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Rick Blood
Joined: 24 Jul 2001
Posts: 2976
Location: United States, that guy in Anaheim, California
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| Posted: Sat Nov 05, 2005 12:22 am Post subject: |
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To maybe support what Kevin is saying about stiffness....
The first time I saw a 50 was at the supernats and it seemed that all the top teams were using them for the first day of practice. On the second day they were all switching to the now infamous (and short lived) 45mm axle. Could it be that the 50s were too stiff and it took a while to figure it out?
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Rick Blood
www.flowdata.net |
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Chad Stapleton
Joined: 19 Jul 2001
Posts: 4403
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| Posted: Sat Nov 05, 2005 4:52 am Post subject: |
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| Mike Goebel wrote: | | Kevin Willmorth wrote: | Using an ugly thing called Math:
D |
Damn math that's a good idea. Who did it for you
Mike G. |
.....whoever it was..got it wrong.
No way does either of those axles weigh 10lbs... unless of course they are 6'long !! 
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Chad
"Those of you who think you know everything are annoying to those of us who do !!" |
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Kevin Willmorth
Joined: 17 Oct 2004
Posts: 1160
Location: United States, Wisconsin,
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| Posted: Sat Nov 05, 2005 6:47 am Post subject: |
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[quote="joseph hollinger"] | Kevin Willmorth wrote: | | Using an ugly thing called Math:...Wow, that seems really heavy. Did you use D when you meant R? |
Yep - sorry about that, was just jamming along, thinking about OD, and all that and forgot to divide by two... Sheeesh! Also buggered up a conversion. My dad (College Math Professor, Researcher, and Engineer) would kick my butt, if he were still with us... I obviously didn't listen to him then, so now I make stupid mistakes.... Thanks for bringing all that back for me Joseph...
Anyway, the modulus numbers are based on diamter, so they remain unchanged.
Heres the weight numbers again, using the proper formula and dimensional data (with steel @7.8grams per cc):
40mm x 3mm- 6.47 lbs
50mm x 2.5mm- 6.83 lbs (5.5% heavier)
50mm x 1.75mm- 4.84 lbs (34% lighter)
Sorry for the side trip through screw-up land... The conclusion remains unchanged, as the relationships are relative to the volume irregardless of the magnitude of screwedituptness.
FWIW, here are some moment of inertia numbers (resistance to rotational force) which indicate the differences of the two sizes in another way:
40mm x 3mm - 33606
50mm x 2.5 - 56807 (70% greater than the 40mm)
50mm x 1.75 - 40676 (21% greater)
I do not beleive that the moment of inertia at the axle is a significant factor in performance of a kart, it's mostly a trivial point. However, being karters we seem to enjoy this sort of stuff.
Just for reference - Forget four strokes and two strokes. I am currently attempting to create a triva drive system, with a conjectural supercharger. This would tap into the internet directly through wireless access points - converting the energy expended on bench racing directly into motive power. I am having problems with the system tests right now, so contribute topics to discussion forums like this in an attempt to push the energy levels up to feed my project and gain the support of unsespecting investors, so I can get my IPO off the ground. 
I'm still back on the market for a 50mm axle that's a bit softer than the 40mm x 3mm. Looks like a 50 x 1.75, and a 50 x 1.5 - plus the 80mm OD bearing set to run in my 40mm cassettes, are in order for next season's test and tune sessions.  |
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Larry Hayashigawa
Joined: 21 Oct 2001
Posts: 401
Location: United States, California,
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| Posted: Sat Nov 05, 2005 8:28 am Post subject: Flogginig a dead horse into pulp |
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Assuming that Kevin doesn't need to lose the weight, why would he go to a 50 mm if all that is needed is more flex in the axle ? Why not go with the 40 mm, which would provide more range in flex and the axle wall would not have to be so thin. I have a 1.75 mm 40 mm axle and the wall thickness looks scary thin and its slightly oval shaped on the end due to shipment damage. I can only imagine what a 50 mm 1.5 mm axle looks like. Not even sure if a 50 mm x 1.5 would survive the beating.
Has anyone on this forum, except maybe Doug Welch, carefully tested 50 vs 40 axles of equal stiffness several times (40 vs 50 then back to 40 on multiple test days) to see if there is a difference?
Larry H |
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Mike Goebel
Joined: 28 Jul 2001
Posts: 5794
Location: United States, California, Winnetka
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| Posted: Sat Nov 05, 2005 8:46 am Post subject: |
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I think the 50 was designed so that the stiffness of the axle is now much greater than the chassis tubing stiffness therefore reducing the axles impact on the overall stifness of the chassis/axle system. It sort of eliminates the axle form the handeling equation, guess that's why Birel has 10 different stiffness of axles 
Mike G. |
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patrick slattery
Joined: 23 Apr 2004
Posts: 789
Location: United States, Ohio, cleves
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| Posted: Sat Nov 05, 2005 9:41 am Post subject: |
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Tommy, as long as we dont lower our standards to allow PH to this forum I am happy.
Pat |
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