M35 axel heat?

[73m819]

open differential, rotational torque,
means the right side drives most of the time.

Rolling bearing friction does not care if powered or not, load(weight), speed, getting rid of the heat, alignment and a few others do affect the temp, powered or not DOES NOT

 

[stumps]

I'll stand by assessment of why the right side hubs are warmer than the left side.

Ok.

I would like to know a bit more about this assessment of yours, if you are willing to indulge me.

1) Are you talking about a measurable difference in temperature, or a theoretical difference?
2) To what do you attribute the one side of the differential doing all of the driving?
3) Why are the bearings hotter? When both side's wheels have the same weight on them, and both side's wheels are turning at exactly the same rate.

-Chuck

 

[Bob H]

I am well aware of my mechanical & engineering background/experience.
Maybe you could explain to me why every time I check the hub temps on deuces it typically shows a temp of at least 10° higher reading on the right rears.
Not just one truck, not just my trucks.

Then explain why an open differential on flat even ground will spin the right rear & not the left rear. Then flip things around and wonder why the left front does it when the front axle is engaged.
The answers to question 2 & 3 were stated in my earlier post.

but according to you guys, apparently my laser thermometer just like playing games.

because there could be no way that a hub under a load from pushing could get warmer than one that is coasting, eh? ( <----sarcasim )

 

[73m819]

IF pushing the bearing under load causes heat, then pulling the bearing with a load rolling resistance would also cause heat because the SAME weight is on both bearings.

 

[Bob H]

IF pushing the bearing under load causes heat, then pulling the bearing with a load rolling resistance would also cause heat because the SAME weight is on both bearings.

While the actual weight (down force) is close, it is not identical due to rotational torque and other variables.
The load from driven side to coast side is not.
One is pushing a truck & the other is pulling a tire or two.

 

[Tow4]

I am well aware of my mechanical & engineering background/experience.
Maybe you could explain to me why every time I check the hub temps on deuces it typically shows a temp of at least 10° higher reading on the right rears.
Not just one truck, not just my trucks.

Then explain why an open differential on flat even ground will spin the right rear & not the left rear. Then flip things around and wonder why the left front does it when the front axle is engaged.
( <----sarcasim )

The reason the right rear tire spins is the rotational load of the drive shaft puts more of a load on the left rear (drivers side) tire there by un-loading the right rear. That's why drag racers have a airbag on the right rear they can put air in to load the right rear tire. You can do the same with traction bars. The idea is to compensate for the asymmetrical loading.

The same applies to the front but is reversed because the rotation is reversed.

 

[Madfarmersson]

Wow--- over my head,
Thanks for the info, it is great stuff keep it coming.

 

[73m819]

While the actual weight (down force) is close, it is not identical due to rotational torque and other variables.
The load from driven side to coast side is not.
One is pushing a truck & the other is pulling a tire or two.

You got to be kidding, if the truck is loaded right, both sides will be very close
Just pulling a tire or two that has the same load as the other side, making those tires hard to rotate due to the weight that causes ROLLING resistance, both sides ARE pushing on the bearings, does not matter what force is doing the push, THERE is NO COAST side in the BEARINGS, both sides are under the same load

 

[m16ty]

The reason the right rear tire spins is the rotational load of the drive shaft puts more of a load on the left rear (drivers side) tire there by un-loading the right rear. That's why drag racers have a airbag on the right rear they can put air in to load the right rear tire. You can do the same with traction bars. The idea is to compensate for the asymmetrical loading.

The same applies to the front but is reversed because the rotation is reversed.

While a lot of this is news to me, this post makes the most sense to me. Although I wonder if you'd ever notice it in something like a deuce. I've seen the drag cars frame twist when they take off but the power to weight ratio is a hole lot different than a deuce.

My line of thinking also tells me that there is no difference in bearing heat if it's driven or not. I could be wrong. The discussion is interesting though.

 

[Bob H]

You are confusing downforce with the force required to move the truck, this force is lateral.
The lateral force to move 13,000# on a set of tires is greater than the lateral force of pulling a set of tires if they had the exact same gravitational (down) force.

Remember, we are talking minor differences that are the reason the right rear hubs tend to run "a little bit warmer".

 

[stumps]

I am well aware of my mechanical & engineering background/experience.

Is this a statement saying you are an engineer, or a statement saying that you are no engineer?

Maybe you could explain to me why every time I check the hub temps on deuces it typically shows a temp of at least 10° higher reading on the right rears.
Not just one truck, not just my trucks.

I suspect that you are a busy guy, like most of us, and your actual sample set is very limited. I explain the difference you have measured as being anecdotal. By pure chance, you have measured one or two trucks that have the right side axle bearings/seals/grease/brakes setup so they are higher friction than the left side... hence the higher temperature.

Then explain why an open differential on flat even ground will spin the right rear & not the left rear. Then flip things around and wonder why the left front does it when the front axle is engaged.
The answers to question 2 & 3 were stated in my earlier post.

That one is simple to explain. The drive shaft is delivering torque from the engine/transmission to the rear axles. If we assume the engine turns clockwise, that torque will cause a torque lift on the right rear wheels, and will provide a similar amount of extra pressure on the left rear wheels. In a slippery situation, that will cause the right wheel to spin.

Compare/contrast that to carrying a load on a truck like a deuce. The torque lift might put a few hundred extra pounds on the left tire vs the right. My experience with trucks has shown that there is no extra heating in the axles with the truck empty vs fully loaded. The bearings just don't care about the weight in the back of the truck.

but according to you guys, apparently my laser thermometer just like playing games.

No, I think your laser thermometer is a disinterested party, and is just reporting the facts. I think you are doing the typical human thing of extrapolating one experience onto the entire population of trucks.

because there could be no way that a hub under a load from pushing could get warmer than one that is coasting, eh? ( <----sarcasim )

That is correct, not measurably so.

-Chuck

 

[Bob H]

I'll stand by my enginneering, machine design & repair, racing & mechanical experience along with temps taken on a dozen or so trucks over the last few years.
While I haven't run SPC charts on these findings, I have checked enough to see a pattern.
That pattern is that the right rear hubs typically run a few degrees warmer than the rest and it is nothing to worry about.
There are literally hundreds of variables that will affect measured hub temps to a greater degree of differences.


You can lead a horse to water, but you can't make it drink, even if you beat it

 

[steelandcanvas]

Here was the original question: Hey just a quick question, how hot should the rear axel on my M35 run? Now why do we have to endure a complete physics disertation just to answer one simple question? I know the OP personally, he just turned 18 years old, and all he wanted was a simple answer to his question. Why do people have to act like they know so much more than everyone else? And then argue the fact to boot? I think it's about time to take my annual 2 weeks cooling off period away from SS. Some of you Guys are just way too smart for me.