Axle 40 mm vs. 50mm

[Pete Muller]

Wow... this subject being flogged again!

Rob Daniel and I had a long conversation about this over the period of a few months, and this document is the most significant information I've seen that pertains to an axle in a kart.

Go here and and scroll down to the document on Loss Coefficient Modulus

Of particular interest is section 2.3 on material damping, and figure 6 on page 11 covering "loss coefficient".

Thanks to Rob for finding this and forwarding it to me (quite some time ago).
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[Andrew Kidd]

Damn.




























I came here from the front page, and I expected a picture of Muller with half his hair in his clenched fists with a torn shirt and bloodshot eyes.
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Cameron Karting - 707.938.9986 - www.cameronkarting.com
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[Andy Seesemann]

[Todd Bellew]

On the work hardening.

When I've seen factory kart teams set up their axles they will replace a straight axle of the same type almost every day. I think it's because use does change the properties.

Steel also "technically" isn't suppose to change properties to a large degree as mentioend. But,we all know a one year old kart isn't the same as a new one. Something has worn out.

These same forces at work wearing out your chassis are the same ones "wearing" out the axle.

Remember this comes from the factories that are the ones who gave us different axles to begin with. Obvioulsy, they didn't let conventional wisdom affect them when producing better pieces.
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Thank You,
Todd Bellew

[Andrew (AJ) Weber]

[Todd Bellew]

I've tried to explain that different alloys have different damping properties for about 5 years now. lol

To iterate the thickness and dimension dictate the spring rate not the damping rates.

Look at my old posts.
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Thank You,
Todd Bellew

[Andrew (AJ) Weber]

[Tommy Griffith]

[joseph hollinger]

[Kevin Willmorth]

From what I have found, the difference in stiffness is not attributable to the wall thickness, as has been suggested. Virtually all 50mm axles are 2.5mm thick, while most every 40mm axle is 3mm. The one exception I found is the 40mm super-soft axle, which may be (bit not necessarily) 2.5mm. Further, from what else I have found, each axle made by the various providers - Freeline, CRG, Margay, R&R - are the same basic alloy, all are a chromolly alloy, although each, manufacturer may use a unique version of the alloy, as is common in frame building. This means that the difference between soft and hard axles, and everything in between, is in how each of these axles is heat treated.

I suspect from this that the soft axles are annealed, while the hardest axles must be through hardened. In each case, the 50mm axle assembly will be a little stiffer for the same heat treatment state, and a bit heavier. The 40mm axle will provide the softest possible setup, while the 50mm will potentially produce the greatest stiffness, should that be desired.

On a side note, I would postulate that the affect of hub length is greater on the softest axle, and less on the hardest axle.

Add this to the affect of rim width, bearing to bearing distance, weight and center of gravity... it's amazing how tunable a kart with supposedly zero suspension really is.

[Doug Welch]

[Kevin Willmorth]

I give up... Uncle.

[quote="Doug Welch]Sorry Kevin, I don't mean to sound nasty but I've done a lot of heavy lifting and testing on axles and this is what I've found. We made and sold over 2,000 axles this year and many people would be surprised to know who all is using them.[/quote]

Sorry Doug, but what you are saying conflicts with the data provided by other providers.

Freeline = 40mm x 3mm, 50mm x 2mm various hardness
http://www.freeline.it/uk_assali.asp

R&R =40mm x 3mm, 50mm x 2.5mm various hardness
http://www.cometkartsales.com/store/axles/axles.htm

CRG and Top Kart axles = 40mm x 3mm, 50mm x 2mm
https://www.pittsperformance.com/index.php?cPath=26_92_130&osCsid=c870eacb28f85d281deaad4db0da1b9e

I did find some minor differences in the Veloce and Brava axles shown on:
http://www.tsracing.com/store/showprod.cfm?&DID=7&User_ID=904767&st=7176&st2=65633527&st3=-44486913&CATID=28&ObjectGroup_ID=113

and http://www.tsracing.com/store/showprod.cfm?&DID=7&CATID=28&ObjectGroup_ID=218

So, while I completely appreciate your approach, experience and research into the subject - I do not understand why it is being presented as a singularity, as though no other approach has been taken - and why you have not assisted in our understanding why others take the appraoch they do - rather than just acting as though they don't exist.

I said it before, and will say it again: I am not an expert on this subject, nor have I sold 2,000 axles. However, I am not prone to making stuff up either. I have attempted to explore the subject to understand it better, and to make some sense out of what is being offered by the producers of the axles themselves. In my own small collected of parts, all of the 40mm axles, in three hardness ratings are 3mm thick, I only have one 50mm axle at this moment, which is the freeline, 2mm thick, which I thought was 2.5 - my bad.

I, as I am sure others have, give up trying to figure this one out, as it has long since stopped being fun.

FWIW, if you'd simply provided a summary of your offering and rationale, along with your findings, rather than wait for an opportunity to jump in and making a point of proving me wrong, you would have succeeded in two ways: 1.) contributed valuable information, and 2.) Gained a customer. I guess one out of two ain't bad.

[Mike Goebel]

[Doug Welch]

Kevin

Let me give you an example, I've tested SKM's A, B, C axles. All were 40mm diametyer, 3mm wall and 1040 length. The materials used were 1010 for the A, 1020 for the B and 4130 for the C, None were heat treated in any way. Now they can put together any sales brouchure they want with any kind of module numbers they want but I know exactly how they are made. I've done similar testing on Freeline, CRG and Tony. I've found exactly nothing different in them.

If you look at their so called module numbers, one of the biggest factors is the length of the axle. Personally, I think these numbers do little but confuse the customer into thinking there is some sort of vodoo-whodoo behind axles. There isn't. From my testing, its all about wall thickness.

The best thing you can do is test, test and test some more. Almost every weekend we are out to the track testing axles and other componets. Different materials do affect what I call the springyness of an axle. Two axles of the same wall thickness will have different dampening properties when you change the material. For example, in general, the 4130 axles will be more bouncy than an axle from 1010. That is why I don't use it in thin wall axles. The car will literaly hop off the ground. Its a very brutal ride.

Almost every day we get requests to build thinner and thinner axles. Many of the top racers have found that as the axle gets thinner, it really frees up the kart. For example, I'm working on a 2.1 30mm axle right now. Our 2.5 30mm axle has proven to be very popular, we've sold well over 300 of them this year alone. Many "factory" teams are using them. They use them because they work.

You want to free up the back of that Biland, get one of my 50mm softs. or better yet, ask for the Pro axle. You would be amazed how much faster you go. A thin wall axle can really increase corner exit speed. Often 3 or 4 mph.
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Doug

[Kevin Willmorth]