Channeled versus Looped rims

When the inner surface of the rim is badly damaged and weakened by rust it is dangerous to use just any patch to try to get a little more running out of the wheel rim. The rim can explode when the air is applied to it in inflating the bad rim. You would be amazed at the power stored in the pressure against the rims of wheels. They can let go and cut you head right off from the body.

I attended a seminar on wheels when I was the master mechanic in a Georgia Pacific plywood mill here in Talladega and they showed us the results of what can happen when one of those big wheels lets go under extreme stress. The wheels in particular that we were learning about were on the big loaders that take a whole 90,000 pounds of logs off a truck etc and move it around the yard. They said that there could be as much as two million pounds of pressure per square inch pushing aginst the edges of the wheel rims when carrying this load and turning etc.

Also about half that much pressure when just being inflated to the correct pressure.
They were so kind as to show the picture of some body pieces laying around the area after one of these big wheels had exploded.

I have actually seen a couple of truck wheels explode after being repaired and being re-inflated. I would say that a 1000X20 truck tire is about the same as a couple of sticks of dynamite when they explode. Just don't be in front of one. They hurt too.

Needles to say ever since I have left the area when a big tractor wheel is being inflated.

I would be in the next county when that rusted and poorly repaired wheel is inflated!

Zane

I made a CRUDE calculation - with emphasis on crude! - and get the side load from 12psi on the rim wall is around 13,000 pounds.

Assumptions made since I cannot go out and measure; maximum diameter of tire side wall pushing on side of rim = 44" (assumeing that tread of tire holds the side wall in beyond that diameter - there will actually be a transition as you move out from the rim not a sudden change - but then I said it was a CRUDE approximation), minimum diameter of tire wall = 24" (where it sits in rim - or edge of tire bead) so the area is 1071 square inches. That times the tire pressure in psi gives the push on the side of the rim.

Seems like a lot, but if you calculate the strength of the rim you get that only 0.017" thick steel of a nominal 10,000 psi strength will hold the side of the rim. Calculated as follows; 13,000 divided by 10,000 = 1.3 as the area that will hold the load. Add that to the area of the inner (empty area taken away from the larger area above to get the side wall area) diameter 3.14159 x 12 x 12 =452.38896 make that 452.3 (that will make the needed rim be thicker than it needs to be) and add the 1.3 = 453.6. This is the area of a circle so divide by 3.14159 = 144.38548633 and now we need the square root of this number for the radius. 12.016 x 12.016 = 144.384256 and 12.017 x 12.017 = 144.408289, so the rim needs to be a shade over 1/64" thick - actually pretty thin!

I know that there are some working ME's out there. I will leave it to them to correct me as necessary. I have retired and I promptly forgot ALL that I learned in college. :-)

Regards,
Larry

See.. that's what I love about civil eng'ring... We don't mess with many numbers under a tenth of an inch..
( Too bad we had to go thru the same stuff anyway to get there! )

Soundguy

All in all though I love eng. as a whole...especially electronics. ( Not to sure about that chemical / biological stuff... :-)

Thanks,

Soundguy

I do too! Must have, I wound up with TWO batchlers degrees. Started in ME - that was what my father was - but graduated (first time) in EE. Dad was working at Collins Radio and that was just when solid state was taking off. He was also an Amature Radio operator - W0PCQ. He pointed out that all the "new" principles of ME had been discovered the previous century, the real changes were in the materials available to the engineer. But that in EE new things were coming out all the time - little did he know how true that was! SO I switched, but at the end of my sophmore year. Had to do soph. EE classes before I could do any Jr. so went on and took ME courses that I had prerequsites for and things I was intrested in - machinery! Ended up with ONLY 27 Quarter (not semester) hours - just a little more than a quarters worth of work. So I stayed on and finished out my ME courses and graduated a second time.

Regards,
Larry

I started in EE, and did the core classes, and pre-req's.. started in on the junior stuff, then took a break. At the time I was working in the office of a construction company doing the book's, etc. They offered to pay the rest of the way if I changed to CE... I jumped at it. All my credits transfered. Worked out ok... I took extra sciences and maths instead of electives.. that really helped on the transfer.. Still wish I had finished and graduated with the EE... I was that close ( holding fingers together ). Ironically, the experience I picked up in EE is paying me more than my CE degree... I'm still at that construction firm, but also work part time some nights at a large entertainment oriented corporation. I'm doing sound engineering, ( a/v support live and recorded sound ).Real fun... no stress less hours and more money... at the day job I'm slaried.. so they practically own me.. tied to the desk..etc...

SouNdguy

Hi Rich,

In a previous life I had to deal with wire spoke rims. They had to have an extra band of rubber over the exposed spoke ends or they would rub through the tube.

I'd say you are right to figure the tube movement is a concern and that smooth is the way to go.

If you have the skill, weld it up. I doubt it will ever cause problems again. I think I would use some thing other than calcium for weight after this.

Wish I had the Howard gear reduction unit like you have! I wonder if something similar could be made - even if it didn't shift it would work for me as I rarely get out of second as it is.

N - joy.

Mountainman...CA

What I would be more interested in hearing...has anyone EVER heard of a small tractor rim coming apart? I haven't. I know truck rims are dangerous, but they are run at much higher pressures, and are a much different rim. I have no fear at all of a decent repair on a tractor drop center rim. I've welded pieces in quite a few.

I made a fire ring out of an original N rim and replaced it with a looped rim, but now wish I had simply replaced the rusted band. The band doesn't really need to add much strength, but merely closes the cavity and gives a smooth surface for the tube.

For anyone wondering if their rim is rusted internally, just jack the wheel up and listen for the rust flakes as you turn it.

George Willer

Bill