Axle Hardness...how can I tell???

[Larry Hayashigawa]

What I don't get is the reason for 50 mm axles.

A 50 mm x 3 mm WT axle is 27% stiffer than a 50 mm 3 mm WT axle.

If stiffness is needed then why not increase a 40 mm axle wall thickness to 4 mm, which has the equivalent stifness of a 50 mm x 3 mm axle.

If less flex (softer) is the objective then why not go with a 40 mm x 2.5, which has the same stiffness as a 50 mm x 2 mm axle.

AH HA, I know! It is a conspiracy by bearing mfg to sell more expensive bearings?

Actually, there maybe differences in performance in all of these axle variations (even mild and hard steel due to differences in the damping coefficient) but what bugs me the most is that every explaination (BS) of why, never has engineering theory to back it up. I believe that most kart manufacturer don't have a good engineering understanding of how a kart works. They just know what works and use trial and error to improve the kart.


This will probably kill the thread.

[Tim Lewis]

[Doug Welch]

[quote="Mike Goebel
.... The most influence comes from the wall thickness. Hardness has no effect either, STOP the bull**** there is no black magic in axles, Ahaaaaaaa, help me.

Mike G.[/quote]

Mike,
You are right on about wall thickness. It controls the stiffness more than any other factor. I have found that if you make them from higher carbon steels, you do get a higher yield strength which makes for a sturdier axle. That is, it will hold up better to impacts and is less likely to bend. Most of the imported axles I have tested are made from low carbon steels, like a 1010 or 1012. They have a very low yield strength and are very prone to bending. An axle made from a medium carbon steel have as much as a 50% higher yield strength and will absorb a much higher impact before bending. So guys, if you go out banging wheels or jumping curbs, you may want an axle made from better steel.
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Doug

[Gary Osterholt]

Doug,

Does the axle materials influenced by what's called shape factor?

Which takes into account the diameter and wall thickness?

Gary Osterholt
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Website Designs - http://www.godesigns.us

[Dan Nasser]

Basically the rear shafts should be considered a cantilever load (support on one end and hanging without support on the outside of the tire)
See End load cantilever beams formulae on this easy to read WIKI link:

http://en.wikipedia.org/wiki/Deflection_(engineering)#End_load_cantilever_beams
and:

http://en.wikipedia.org/wiki/Area_moment_of_inertia
see section on hollow cylinder.

The conclusions I get are:

1) deflection of shaft is proportional to downward force on the tire or loading.
2) 50mm shafts are roughly 2.5 times stiffer than 40mm shafts of same thix.
3) To get equally stiff axles, a 40mm needs to be 5mm thick to compare to a 2mm thick 50mm shaft. The 40mm shaft will be much heavier of course!
4) Increasing distance from bearing to hub mounting point by 15%, yields 50% less stiffness. This is why rear wheels have different offsets to their mounting point.
5) materials vary very little in their elastic modulus; which is proportional to deflection, so it seems weird there are soft/medium/hard shafts of the same dimensions? I believe this to be a marketing gimmick.
6) 50mm bearings are much stronger and more rigid too.

[Britt Robinson]

Lazarus!
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I am a precisional instrument of speed and aeromatics. - Mater

[TJ Koyen]

10 years, is that a record?
_________________
T.J. Koyen
OKTANE VISUAL - Custom Helmet Paint & Graphic Design
www.oktanevisual.com
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--------------------------
DB Motorsports
Exprit/Leopard

[Jim McMahon]

Yeah quite a revival alright. I think there's been a few threads since as well. Never ending topic and part of makes karting so interesting.

[Sam Zavaglia]

[Sam Zavaglia]

The original post was how to tell what we have, answer is either by outside marking like CRG do or by paint color on one inside of axle.

Anyway, more info for debate.

Prodezine Axles
In our experience your axle and seat are the best major tuning tools available to you.
Exclusively sourced from Europe, Prodezine axles offer the widest selection of hardness & lengths to let you fine-tune your kart no matter what the track or application.
Prodezine axle selection criteria:

Choice of length;

1040mm - longer axle adds lateral stability or

1020mm – shorter axle lets the kart roll a little making it quicker through left & right combinations and chicanes.

Pick the one to best suit the features of your track.

Choice of Hardness

Prodezine offers 5 options in 40mm, and 7 options in 50mm diameter from super soft through soft, medium, medium hard & hard up to super hard

A softer axle will loosen up the kart; reduce bogging out of turns; and help overcome increase in track grip.

A harder axle will help grip the chassis up more.



Different steels, tensile strength and yield points in here.

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www.samzavaglia.com

[Sam Zavaglia]

[Dan Nasser]

Rear wheel hubs come in different lengths. This should make a big difference in ride stiffness. Is this the sole purpose for the different lengths?

[Jim McMahon]