Bias-Ply tire failure in non-automotive industrial application 5

[MrReliability]

I have a "High Spin" rolling system that spins pipe to compact cement lining. We are using tandem 7-14.5LT D/8 bias-ply tires on each end of the axles with the pipe riding in the saddle between two sets of tires. The tires are running approx. 70 MPH for just over a min. The maximum weight of the pipe is 3500 lb. and it is held down with two sets of metal rollers that straddle the pipe with approx. 800 lb of downward force on each set.
My problem is that we keep separating the tread from the tire. The pipe thrust one way or another without issue so I am not sure that bias is the proper tire for this application. Any help would be appreciated.

 

[MikeHalloran]

Since the radius of the pipe is much smaller than the radius of a road, I'm >>guessing<< that radial ply tires would sustain the abuse of repeated extreme flexing better than do bias-ply tires.



Mike Halloran
Pembroke Pines, FL, USA

 

[patprimmer]

Tyre pressure might also be a very significant factor, like they might need somewhat more than automotive application pressures to cope with the extra distortion at the same load.

Regards

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[GregLocock]

You are also running at a speed rather close to wheelhop, I suspect, so you may be exacerbating heat buildup in the tread.

Small rollers at high speed are a good way to wreck tires as Mike said.





Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[CapriRacer]

Mr. Reliablity,

Did I understand this right, that the combined load on the tires is 4100 pounds?

Also, you didn't tell us the diameter of the pipe. Maybe I can find a diameter vs deflection graph, so we can estimate what the flat plate equivalent load would be.

And lastly - I tend to think that radials would be worse rather than better. But just to be on the same page: The casing is intact, right? Only the tread is chunking off?

 

[FoMoCoMoFo]

5100 lbs / 4 No ?

 

[MrReliability]

Thanks everyone for your input. I've had some local "experts" come and look and what they have said is that with higher air pressures there is no 'give' in the sidewalls and so the tread is taking all of the flex, they also said that the tire is slightly narrower than what the rim is made for. With the small diameter of the tire and the fact that the tandems are tight together I believe that the options are very limited.

CapriRacer,
Yes the combined weight on 8 tires, 4 sets of tandems, is as high as 4100 lbs.
The diameter of the pipe range from 6" to 30" with weights of 30" pipe being around 4100 lbs and 6" pipe being around 500 lbs.
The casing is intact it is just the tread chunking off, on inspection of blown tires you can feel that the tread has seperated completly around the crown of the tire.

 

[MrReliability]

Sorry I screwed up. The max weight for 30" pipe and the hold downs is 5100 lbs not 4100 lbs as earlier stated.

 

[NormPeterson]

How many of the tandem assemblies are drive wheels?

How is the rotating pipe braked to a stop?

Is there any particular set of tires within which you're experiencing a greater failure rate? Any one tire position in particular?

Does the end of a tire's life tend to occur at a particular point in a 'spin cycle' or is it random?

The summation of forces applied to any given tire isn't quite as simple as 5100 ÷ 4 (and likely not quite equally divided in each pair).

I wonder if you're starting to generate standing waves in the treads.


Norm

 

[patprimmer]

Higher air pressure will be distributed evenly and will reduce flex in both the tread and sidewall. Large trucks use 100 psi on their tyres which are heavily loaded. This does not cause their treads to chunk off.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[MrReliability]

Norm
There are 4 axles with the two inside axles being drivers and the outside two are idlers. I agree that the load will not be the same for all of the tires. The pipe has a bell on it that is considerably larger, thicker and heavier. There seems to be no pattern to the chunking. I am thinking that the small footprint of the pipe and the cengrifugal(tangential) force from the pipe spinning might be a factor. On one side of the tire there is a footprint and on the other side (30-45 degrees apart) there is another footprint, except for the outside tires. I thought that the idlers would either go more or less frequently because of this but that is not the case.
As far as standing waves, I don't even know how I could conferm this or not, but the pipe spin according to speeds that were found to better compact the cement and remove the water. Standing waves could be a contributing factor in this compaction.

Would anyone know how this might be confermed?

I would like to find out about having a 'tire engineer' come out as a consultant. Does anyone have any information on how to go about getting someone?

Again thanks for everyones comments and help!

 

[NormPeterson]

"Would anyone know how this might be confermed?"

Video? (guessing that you'd want it at a higher speed than consumer camcorders are good to, though)


Norm

 

[Compositepro]

A strobe light might work and would be simpler and cheaper than high speed video.

 

[patprimmer]

I agree with Compoitepro.

An adjustable strobe light is the way to go. You adjust them to get a slow rotation effect similar to the stage coach wheels in old movies.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[CapriRacer]

Mr. Reliability,

First, sorry for the math error - I caught it after I posted - and apparently so did everyone else. That's what I get for doing this in my head!!!

OK, so 8 tires carrying a total load of 5100 = 638# per tire.

The tire is rated for dualed tires is 1650# at 70 psi. BTW, what pressure are you running?

I still haven't found a flat plate to curved surface chart, but I do know that a 67" diameter road surface needs to be run at 88% of the load to get the same deflection - and there are some who think that even getting the same deflection generates stresses in excess of the flat plate.

I also don't know if the worst case is the 3500# 30" diameter or the 500# 6" diameter.

Plus I think we need to factor in that the loading on the tire isn't strictly radial. The net force on the tire is producing a tangential load above and beyond the torque needed to spin the pipe.

If I had to hazard a guess, I think the radial load needs to be half of the rated load. That would be 825# tire rating vs 638# pipe load. Still sounds OK, but is the load the same on all 8 tires? (I think you said the load is unlikely to be the same)

"Too much pressure?" - I totally disagree. These are bias tires and the fact that you are getting tread separations says there is a shear force that is exceeding the bonding strength between the cords and the rubber. Lowering the pressure is either going to cause the separation to occur sooner or the separation will occur in the sidewall.

Oh, and how old are these tires? Is it possible that what you are seeing is just tire age? Maybe a bit of history would help. Which tires failed? Have there been repeats?

BTW, I would hope you are at least replacing tires in pairs.

How about a photo? It is hard to visualize what the set up is and those of us who know tires and what is important to them are going to look for certain things - and those things will be different that what a machinery guy would be interested in.

One last thought. I'll bet the shop has an infared pyrometer. You could measure the tread surface of the tire. That will tell you lots about the actual loading.

 

[CapriRacer]

Post Script:

Where is my head this morning???? I forgot the simplest test of all - pressure build up!!!!

Measure the inflation pressure cold - the machine has to be idle for at least and hour and a half - longer would be better.

Then measure the pressure after an hour of operation - and every hour until the pressure stabilizes.

This is a little out of my league (I'm a passenger tire guy), but I think you shouldn't see more than a 5 psi build up. If more than you need to add pressure.

 

[MrReliability]

CapriRacer,
To answer a couple of your questions:
We were running unloaded pressure of 70psi we have since changed it to 45psi.
All of the tires are within 6 wks old when they blow, and we are changing at least both tires in a tandem, most of the time we are changing all 4 tires on an axle as we have to pull the axle to change a tire due to clearance issues.
There seems to be no rhyme nor reason to the blow-outs. They are spread out.
I have attached a picture of the high spin rolls in action. This is an 8" pipe.

 

[crysta1c1ear]

If the radii of the tyres on a car differ slightly it causes the car to turn (then corrected by steering) or for the play to be taken up by a differential.

If your tyres had different sizes due to different starting pressures, different heating, a recently shreaded worn tyre being replaced by a larger intact new one, or whatever, is there anything like turning or a differential that absorbs the speed difference [same shaft angular velocity times different radius gives a different desired speed], or does it result in a torque between the contact patch and the wheel that almost literally has nowhere else to go apart from slip and eventual damage?

I hope I'm making sense. I understand what I'm trying to say, but I haven't written it very eloquently!

 

[crysta1c1ear]

Is that three pipes loaded into the gaps in four tyres, so tht the inner wheels support two pipes and the outer wheels support just one.

If so, can the outer shafts and wheels that support one bar spin at a different rate to the inner ones that support two?
Or are all the shafts driven from the same source 'with no play in the system'.

I'm coming back to my previous posting. I should have looked at the picture first, but I have a slow modem where am I now.

 

[CapriRacer]

Mr. Reliability,

I think I now see why the lower pressure was recommended.

It looks like there would be an incredible amount of shear stress in the tread area - and there are opposing shear forces - something a tire would not ordinarily experience.

I am curious. Is this an old machine? If so, what changed? (unless you were having trouble before and this is just a continuation.)