Tubular -vs- Solid Axels

[sweav]

What is evryone using for the rear axle, 1" or 1 1/4"?

[royster]

i am using a 1" and i think most are using the same.

[monkey-1]

I only use 1.25" axles.

[bm1]

I too only use 1 1/4" tubular axles. Tubular is stronger than solid.

When using the bearing flanges that sandwich the bearing in between, put a thin AN flat washer between the flange halfs. This won't "crush" the bearing and it will roll a lot freer.

[RUBICON]

Technical response....tubular is not inherently stronger....the forces of deflection are greatest on the outer diameter of the bar.....they diminish as you reach the center....as a compromise....the deflection moments are mimimum near the center...therefore in the benefit of weight reduction...and minimizing inertial loads the center of the bar does little....weight savings are more of an advantage...you are dealing with tortional loads and deflection ...kart axles are about weight savings and torque......solid is stronger for sure...but you really don't need it...tubular aluminum is great and cool looking.....mine is tubular chrome moly but that is because I have a diff and needed to insert and weld stub splines it it for the diff....

[bm1]

I have a barrel full of solid axles that are all bent from the indoor kart racing circuit. I went to the tubular axles and haven't bent one yet.

[sniffles]

you would think solid would be stronger...strange

[stool-sample]

Ive been told the tubular will flex out then back where it was, the solid will flex out and stay. Why? I havent a clue, but the tubular is what we put on all our racing chassis unless, the buyer wants solid.I know you need flex for your weight transfer. If youre not transfering the weight your not racing.It will push like a truck.Not the same on stools but Were set up to make them.

[bm1]

Take a piece of 3/4" solid rod and bend it over your knee. Now, take a piece of 3/4" tubing and try to bend it over your knee.

[RUBICON]

You hit it!....look back at the terms used in the discussion of this subject...some have said "tubular is stronger"....that is not true....tubular is #1 lighter..and #2 does allow for flex and return to its previous shape...provided it was not moved beyond its elastic limits....liik at the cross section of any structural shape...the moment forces that compress one side and elongate ( stretch ) the other...are the greatest the fartherest from the center and diminish at the center....thats why large diameter thin walled tubes resist deflection better than smaller diameter thick walled tubing...this principle is demonstrated in a driveshaft...granted it does not have to bend...but the twisting forces are greatest at the radius and therfore large diameter tubes are great.....as for the bending a solid 3/4" bar over my knee and then a 3/4" tube....let anyone do this with the same type of steel...and they will see.....another way of visualizing this is ....you have 2 identical tubes...3/4" dia...thin wall..or whatever.....they both bend and return within the same limits....now...slide a 2nd tube inside of one...a tube that just fits....now flex them both....the single tube will deflect to point and return...the one that is double will not flex at the same load...it is more stiff...it will move less and return...if you apply more force it will not return straight...why...you have taken the inside tube beyond its elastic limit and it resists returning straight....now imagine this example with so many hollow tubes inside of each other that it is essentially solid....see the point?.....solid is stronger for a given diameter....not lighter...not more flexible...think about it

[RUBICON]

Sniffles....I assume you may still be in school....if so ....ask a teacher...maybe Physics....about deflection ( bending moments ) on tubular vs. solid structural shapes...and strength. ( resistance to deforming and not returning to the original shape and dimension....

[sniffles]

alright i understand now. its just kinda weird at first. somethin hollow is stronger than somethin solid. yah ill ask a physics teacher. shes really weird.

[elvergon]

I agree with Rubicon. Some friends have material and their properties classes. There´s a formula for getting this up. I don´t remember it pretty well. It was something like ....bh*h*h (dunno how to express h to the third power)....If your axle is solid you leave the calculation as it is. If the axle is hollow you calculate it using this formula, and you substract the inner "hole" that is left.

Lets take for example a 1" solid axle. It has a strenght (torsional I guess that´s it) of 1 (1x1x1x1)

I think there are some common axles that are, 1.25" in diameter, with a .250" wall. We have the outer calculation (1.25"x1.25"x1.25"x1.25")= 2.44 and then you substract the inner part. Which if you have .250" wall it would be 1.25"-.5"( 2x .250")....... .75",...so you use the formula again for the inner part... (.75"x.75"x.75"x.75")= .316 THEN the total strenght of the .250 wall axle 1.25" in diameter is.... 2.44 - .316.... 2.12....So here you could see the great impact of the a little bigger in diameter has compared to a normal one.

Solid steel axle strenght would be 1...
1.25" .250" wall would have a 2.12.... SO it is 2.12 times harder...

If the axle would be 1.25" solid...the total strenght would be (1.25x1.25x1.25x1.25) 2.44 so comparing it to a hollow axle, SOLID is STRONGER than hollow if it is made from the same steel, and the same diameter!

Hope that helps