Transmission tunnel heat

Ahhh... OK. I didn't understand his phrasing then, I guess.

Count me in the "six of one, half a dozen of the other" camp. A tranny's gonna get as hot as a tranny's gonna get, the way I see things.

I still think the OP's heat problem has more to do with the muffler/cat(s)/exhaust system than the tranny itself, though.

Reply to
Don Bruder
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One always has to try to help the unsophisticated:

] It ] confirms the usual assumption that gear box power losses are ] almost nil in 4th, but considerable in 1st.

Let me know if you do not know the first law of thermo.

] It is the gearing *reduction* that ] causes the real power loss, though why that is you will have to ] ask a *real* mechanical engineer, not an aerospace one.

Let me know what you do not understand about this paragraph above. I *assume* the reason might be the oil friction where gear teeth meet. Though AFAIK, it could as well be the torques well exceeding engine torque in lower gear, or simply be the fact the gear box losses are optimized for 4th. Reread my sentence quoted above. Again. Again. Keep reading. Eventually something might click.

Tire resistance is quite low when driving in a straight line at constant speed. Air resistance is also quite low at legal speeds. The main difference is however that the energy at highway speeds is transmitted in 4th, hence does not cause significant heat generation.

You still have not presented a shred of evidence for your on its face ludicrous claim that "churning the oil" produces the gear box losses. Do you agree the bigger the gap between moving parts, the *less* the heat generated?

I do not see that claim anywhere. As far as I know, it is impossible to make gears that have *exactly* zero slip in the contact area. (For one thing because the intervening oil makes the contact area quite big.)

Of course, I did not read it all. My interest in gear design is nil. Since you *claim* to have seen it, please list the place you saw the claim of exactly zero relative motion so that I can confirm it.

Anyway, even if it were possible (and I know it is not), it is completely irrelevant. You obviously do not understand that

*regardless of dry slip,* there will be tremendous shear in the *oil* in between the gear teeth.

Actually, heat produced by "churning oil" *is* frictional losses. The heat generated at the gear teeth that I think may be the major problem is generated by *exactly the same mechanism." You seem to think that I was talking about dry friction, (if you know the difference.) If you reread what I wrote, you might see I never did.

See my above remark about asking a real mechanical engineer.

This is a ludicrous claim. I would think it is probably the way they handle the clutch function, not gearing losses, but NEVER MIND.

I suggest you provide an explanation how moving parts that may be inches apart cause significant heat generation in the thick layer of oil in between if you want me to take your further discussion serious.

Leon

Reply to
Leon van Dommelen

Let *me* know how you think the law that states that the energy of a closed system remains constant and that heat and work are equivalent applies.

And I'm curious, why 4th gear? Why not 5th? And if not top gear, then why not 3rd?

What makes 4th gear special? I think I know *why* you might *think* its special, but I'd like to hear it from you.

But why would that oil friction be less in 4th gear?

Any change in *force* between the teeth must be matched by an exactly inversely proportionate change in *speed*.

And once again, how is a gear box "optimized" for 4th?

Air resistance increases as the *square* of speed and power requirements to overcome it, climb as the *cube* of speed.

So resistance at 60mph is 4 times the resistance at 30, and power required (and thus power losses) is 8 times as great.

No.

Start here:

At "The involute tooth".

If a tooth is generated by the curve created by unwinding a taut cord from a base cylinder, then the curve is perpendicular to that cord at every point along it.

Since that cord line represents the line of action of the two meshed gears the motion of the line is instantaneously perpendicular to the surface of the two mating teeth (which as the article shows, make contact at the intersection of that line and their surfaces).

Since the motion is entirely perpendicular to the tangent at which the two teeth make contact, there is no component of motion along that tangent.

i.e. No slipping.

Fine. Be pedantic.

They handle the clutch function by pumping *oil*. Churning it (for lack of a better word) in the torque convertor.

Stir a fluid, and you heat it.

"James Prescott Joule did a famous experiment which demonstrated the conservation of energy and showed that heat and work were both of the same nature: energy. His system of interest was water in a thermally insulated container. In this container was also a paddle which was connected to the outside world (surroundings) and connected to weights on a string. Joule measured the work done by the paddle wheel and he also measured the heat created by the wheel turning in the water. Significantly, Joule found that the amount of energy done as work was converted exactly to heat. "

Reply to
Alan Baker

The heat generated inside the gear box equals the frictional losses inside the gear box. Authorative sources tell me this loss is negligible in fourth, but quite considerable in low gears.

Add. 1. 1. 2.

And you have given me zero reason to doubt these sources.

Find out and tell, me, OK. I am not the source of this info, I just repeat it. As I have now stated *many* times.

It is the only one among 1, 2, 3, 4, 5 and reverse that is equal to

  1. Makes it unique in my book. How do *you* define unique?

Because all the friction has already been spend in gears 1 through 3?

Unfortunately, there is a slight issue between force and work that you seem to be unaware of. Think dots.

It has a build in clock that stops churning the oil on July 4?

Applause. Quite good.

Unfortunately,

0 x 8 = 0 1 x 8 = 8 2 x 8 = 16 ...

Yes, really, really, true. Now think about that. Deep. Keep trying.

That is the end of this discussion, then.

How many gear teeth have you met in your life that meet at a mathematical point? Next time you meet one, take them for a beer, OK?

Isn't mathematics wonderful? If they could only make those gears.

Fine. Be an idiot.

That sound like it confirms my guess. But no matter.

Applause. Too bad you already admitted you do not know the effect of length scale above. Otherwise it might have given you some ideas. Maybe.

This discussion is over. Leon

Reply to
Leon van Dommelen

It'll be really amusing when the quotes move entirely off the screen.

Reply to
Lanny Chambers

Now, Lanny, be nice :)

Reply to
Don Bruder

Sources that were nowhere to be found in the original post to which I responded and which you still fail to cite or even quote.

Perhaps you should find out before you just take it on faith.

Is there any reason for you to be behaving like an asshole?

Is there any reason for you to behave like an asshole?

Spell it out, or stop with the cryptics.

Is there any reason for you to behave like an asshole?

Now you're claiming that friction in 4th gear is zero? Or how else would this be relevant?

Is there any reason for you to behave like an asshole?

Is there any reason for you to behave like an asshole?

Is there any reason for you to behave like an asshole?

Is there any reason for you to behave like an asshole?

Is there any reason for you to behave like an asshole?

Asshole: the gearbox is *full* of oil. The gears are churning it all the time.

Sure. Apparently actually citing sources is too much for you.

Reply to
Alan Baker

I think you all have it all wrong! If it were just the tranny the temperature would be fairly uniform on both sides of the tunnel. The exhaust radiates more heat than the tranny. At high speed, the additional air flow seems to help distribute the heat over a wider area. In town, the exhaust temperature at the manifold is usually quite low. On the highway, 1200 Deg F. is not too unusual under a load.

Reply to
chuckk

I thought it was, but I cannot swear to it.

That is for sure.

With would make the highway temperature hotter. We are trying to explain why it is so much cooler.

I did a Yahoo search on the internet yesterday morning, and I am starting to doubt that the difference between gears is as big as I understood from my references. For example, see

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the thing is unlabeled. Also, testing conditionsare not given. Are they at the same power or the same outputtorque :( Anyway, assuming the top tick is no losses, the power loss (heating) seems to be roughly proportional to the gearing ratio Z. That agrees with the formulae given by
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tooth friction (presumably the major loss, at least the oneyou are to account for in first design) if you apply Taylor seriesexpansion for large number of teeth. For some reason first gear has a truly excessive heat generation at low speed that I have no clue about. Also, car flexing is obviously not included but apparently important. Still the differences between gears, while apparently quite large, do not seem enough to explain the tremendous difference in temperature at the console I noticed.

Maybe it is just that the tears in the rubber booths closed better on the highway.

Leon :)

Reply to
Leon van Dommelen

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