Orange County Choppers!!

[Chris P.]

Pauly = a numbskull with access to alot of neat tools!!

Jesse James = a real fabricator-craftsman-bike builder!!

IMO

[Scott S]

I find the show very entertaining,especially when they are welding w/o helmets and burning themselves because they don't wear gloves...safety at it's finest

[dekker]

But the guys in Oklahoma building the frame from bored out hex bar stock for the tool bike were impressive.

[vipermanz]

watching the show tonight got me to thinking, when paul sr found them all beating on that truck , and said: Get in here numb nuts, we've got bikes to build. I summed it all up, them assembling bikes is about like people with import race wannabe cars, they more crap you can stick in a square foot, the cooler looking it is. I wonder what there sucess rate is with finished products...

[mozark6]

i have 2 buddies that have high pro customs,ultra jackhammer--titan nice!!sleds but a pain in the a$$,alaways something to mess with.ever notice what paul sr rides (H.D.)

[TonyC]

No doubt that Jessie James is the man with the skills, hands down. Still, American Chopper is entertaining to me for other reasons. I enjoy watching it. They do seem to be the sloppiest weldors there are. On the Tool bike show there were three separate incidents where they burned their hands by welding without gloves. Then Paulie managed to stick the Tig torch to the item he was welding. I think the award goes to Paulie for drilling a hole in a brand new tire while trying to drill the fender. If I ever did anything that stupid I wouldn't let them air it!

[Guest]

I caught that show last Saturday nite, they had a bike called the Comanchee....what got my attention was the frame....square tubing turned so that the corners were north, south, east and west. I guess the entire frame was welded that way...I have never seen that design before and wonder if it is superior stress-wise and structurally . Any ideas on that from you engineer types and bike builders?? inquiring minds want to know.

[Ken M.]

In general you can think of the stiffness of a beam (resistence to deflection) equal to the product of the moment of inertia (I) and the modulus of elasticity of the material (E).

That is
stiffness = E x I

If memory serves, for square tubing the moment of inertia is

I = d^4/12 through the centroid with the tubing alligned flat side down.

and

I = d^4/12 on the diagonal

the modulus of elasticity of steel is about 30 x 10^6 psi.

so the stiffness would be the same either way you look at it.

I suppose which is better would depend on the fit up and welds and how the stress is distributed throughout the joints.

regards,
Ken

EDIT
After thinking about it a few minutes, it crossed my mind that even though the stiffness is the same no matter how you orient the tubing, the stress due to bending at the extreme elements (top and bottom corners) of tubing loaded on the diagonal would be higher than tubing turned with the flats up and down (e.g. at the extreme ends top and bottom there would be more meat to take the stress with the tubing oriented normally). So it might not be a good ideal depending on how the bike is stressed. Although I suppose for normal riding conditions it would be okay if the wall thicknesses are large enough.

This is all off the top of my head without really sitting down and crunching some numbers.

regards,
Ken

[pontiac]

Finally the real fabricators get some air time..
The frame guys from Oklahoma did some nice work..

Whats with Paul Jr wasting acetylene??

First he was going to set a live torch on the bench..
no that didn't work.. ok lets just have mike hold it while he farts around for 5 minutes.. honestly would it kill him to light the torch again??

If I were building that bike I would have gone with a soft tail frame and used those big 2" open box wrenches as trailing arms..

oh well.. same bike new stuff tacked on.

[tigman]

I'm into motorcycles,Japanese sportbikes not choppers but I will venture to guess it was done more for looks than strength.I think placing the tubes like they did will add more strength though but probably not the reason why they did it.Looks are a big thing in the motorcycle game,nobody wants an ugly bike.Three things that apply alot of stress on a frame are,cornering,these choppers do not do that too well.Braking,90% of your stopping comes from the front brakes and some of these bikes don't even have front brakes.Those with brakes have so much rake that when braking you are not getting any weight transfer to the front wheel, so you will have very little grip on the front tire=very little braking power.Acceleration applies alot of stress,these bikes do accelerate 100+hp and 80+flbs of torque.The frame would have plenty of strength if the tubes were sitting with the flats across the top(hope that made sense)Scott.

[Dextreme]

I just wanted to show the pics of the Comanche bike that is being discussed (incase others have no idea of what we're talking about).

[realhfd]

if nobody wants an ugly bike, why are they building that thing.

[Guest]

Originally posted by Ken M.
In general you can think of the stiffness of a beam (resistence to deflection) equal to the product of the moment of inertia (I) and the modulus of elasticity of the material (E).

That is
stiffness = E x I

If memory serves, for square tubing the moment of inertia is

I = d^4/12 through the centroid with the tubing alligned flat side down.

and

I = d^4/12 on the diagonal

the modulus of elasticity of steel is about 30 x 10^6 psi.

so the stiffness would be the same either way you look at it.

I suppose which is better would depend on the fit up and welds and how the stress is distributed throughout the joints.

regards,
Ken

EDIT
After thinking about it a few minutes, it crossed my mind that even though the stiffness is the same no matter how you orient the tubing, the stress due to bending at the extreme elements (top and bottom corners) of tubing loaded on the diagonal would be higher than tubing turned with the flats up and down (e.g. at the extreme ends top and bottom there would be more meat to take the stress with the tubing oriented normally). So it might not be a good ideal depending on how the bike is stressed. Although I suppose for normal riding conditions it would be okay if the wall thicknesses are large enough.

This is all off the top of my head without really sitting down and crunching some numbers.

regards,
Ken

Thanks Ken, that's the kind of answer I was lookiing for. Now let's take that a little further....why do we bend tubing in the square mode, rather than the diamond mode? I did see a bend like that in the frame of that bike, tho. I don't think it bends very good in that mode. I'm thinking that too much of a bend would collapse the tube easily. Any thoughts?

[Ken M.]

I have never bent tubing along the diagonal but it is interesting to think about what would happen. Thinking about it, if we put a piece of square tubing in pure bending by add two opposite couples to the end of the tube so that it would bend on the diagonal, the axial stress due to bending would be greatest at the vertices (corners) of the tubing. We would have compression on the inside of the bend and tension on the outside of the bend.

With the force greatest at these vertices, this is where the tubing would go beyond it’s elastic limits first while the material just inside is still elastic. On the tension side the steel would stretch as we know. On the compression side it seems the failure would result in buckling since the material can only compress so much. This would give the compression edge a wrinkled, wavy look. This would be something I would most likely would proudly throw into the scrap pile.

I suppose using a good set of matching dies, the buckling can be controlled a good bit to give a nice bend in the tube along the diagonal.

I guess the best reason most tubing is not bent on the diagonal is the need to attach other stuff to it on the vertical or horizontal axis. And we all know this is easier to do on the flat sides.

Interesting discussion. Tigman is right, after looking at the posted images of the bike, they did it for a different look then the standard round tubing and it is pretty neat looking. I don't care for the gas tank too much but do like the rear fender a fair bit.

regards,
Ken

[Scott V]

I Know when Buell designed his frames for his bikes, he was real happy to find that for his frames round tube was stronger.He said he did not really like the look of the lawn furniture frame style.I agree totally. It does look nice by the pool though!