R151F: What a Mess

[pappy]

That is taller than Beno.

-Mike-

And in case some of you are not aware of the inside joke here ...

.

 

[pappy]

Mess is in.

Ordered new cross-member/skid plate from BudBuilt. The factory cross-member only supports one case, the BudBuilt will support both. Also, the factory cross-member is in the way of the front driveshaft.

Rear driveshaft is at U-Joints for shortening. Will be ready Thursday afternoon. Then I will have a driver.

I need to get a new header-to-exhaust gasket as the one that was in there was leaking.

There is oil in the gear boxes, and everything seems to be spinning. Now I need to figure out what to do for a center console.

 

[TroutRunner]

Super fun. I like it. What ratios does it give you?

 

[pappy]

101:1 final low range. First gear is 9% lower on the R151 than my old W56 ... 4.313 vs. 3.95. Should make it nicer to drive around town. Plus, the overdrive is just a tad taller too ... .838 vs. 85 which will lower rpm on the freeway a little bit.

Going to get some steel tomorrow and play with a shifter base to get the hole in the floor covered up.

 

[lurch]

101:1 final low range.

Nice! If I remember right Da40 is around 60:1
so 60:1 on 35's and 101:1 on 33's that will be night and day between the two

 

[pappy]

The torque difference between the 2FE and the 22RE is night and day, which is why the minis are usually geared much lower to compensate. Plus, we have the room underneath to get away with it.

 

[Devil Frog]

101:1 final low range.

That means torque at the wheel is on the order of 10,000 ft-lb! Do you have beefed up axles and shafts?

 

[pappy]

Worked in the center today. I went to the UPull and bought shifter boots off another 85. I then took the boneyard plate and my plate, and cut them to fill the hole in the middle. In the pic the silver plate under the transmission shifter was the boneyard, and the black plate under the crawler box was mine.

It's not finished yet since I ran out of rivet nuts. It's sealed from below for now. I had an issue with the transfer case shifter (bottom shifter in the pic). The tunnel narrows between the two transfer shifters and I need to bend over the plate to seal from below. I might get some 1/8" steel and make one solid piece.

Now I need to think about the center console to cover up this mess. I have some ideas, but mating to the box in the middle will be a challenge. I have some ideas there too.

I did realize that I won't be able to use my CB radio with the shifter moved forward 2". Maybe I'll use this as an excuse to abandon CB and go just HAM.

 

[Cruisergreg]

Don't worrry. Jon likes to break stuff.

That means torque at the wheel is on the order of 10,000 ft-lb! Do you have beefed up axles and shafts?

 

[pappy]

I keep looking at that and don't get the math. 170lb-ft is 170lb-ft. The only difference with the gearing is speed vs. rpm. I've heard of "torque multiplication" but just don't see the mathematical logic. I don't see how you can increase torque with gears, only placing where the torque/hp is relative to how fast one is going.

Any of our MEs want to chime in?

 

[Devil Frog]

I keep looking at that don't get the math. 170lb-ft is 170lb-ft. The only difference with the gearing is speed vs. rpm. I've heard of "torque multiplication" but just don't see the mathematical logic. I don't see how you can increase torque with gears, only placing where the torque/hp is relative to how fast one is going.

Any of our MEs want to chime in?

You can not multiply HP with gears, so typically HP at the wheels is within 10-15% of HP at the crank (less drive train inefficiencies).

Torque at the engine however is multiplied by your reduction ratio. Not free lunch though, because at the loss of RPMs.

I can put up the equations if my qualitative Explanation falls short. Maybe Marc could explain it better (I copied off him to get through grad school

 

[pappy]

Why wouldn't hp increase as well? Hp is a function of torque x rpm. If one goes up the other should too. Am I messing something?

 

[Devil Frog]

Why wouldn't hp increase as well? Hp is a function of torque x rpm. If one goes up the other should too. Am I messing something?

Power is the time derivative of energy. The 1st law of thermodynamics requires that energy must be conserved, so power at the crank is equal to power at the wheels plus power converted to heat in the drivetrain, and the universe is cool with it!

 

[Devil Frog]

Why wouldn't hp increase as well? Hp is a function of torque x rpm. If one goes up the other should too. Am I messing something?

Also
HP=( torque*RPM)/5250
But that only applies at either the crank or the wheels, because the torque and RPMs are generally not equal at both places

 

[marcfj60]

I'm going to use the excuse that I'm too lazy to work it out or try to explain it. But torque in its simplest terms is force X length of the lever arm. So if you apply 100 lbs-force to a 1' lever, you generate 100 ft-lbs about the axis of rotation. But if you put that same 100 lbs applied to a 2' lever you now have generated 200 ft-lbs of torque about the axis of rotation. Gear reduction is effectively applying forces to increasingly longer lever arms.

And the statements about HP being related to RPM help to explain how a D60 Detroit Diesel can run at 1,800 RPM, have 425 HP but 1,450 lbs-ft of torque.

For the record, I copied Isaac's work more often than he did mine. You forget a lot of stuff from undergrad if you wait 10 years to start grad school.

 

[Devil Frog]

And the statements about HP being related to RPM help to explain how a D60 Detroit Diesel can run at 1,800 RPM, have 425 HP but 1,450 lbs-ft of torque.

...and conversely, how a 2.4L Formula 1 engine can make 800 HP @ 19,000 RPM but a max torque of only 200 lb-ft @ 17,000

 

[pappy]

Also
HP=( torque*RPM)/5250

Ya, that I knew. I just simplified the equation and left out the 1/5250.

But torque in its simplest terms is force X length of the lever arm. Gear reduction is effectively applying forces to increasingly longer lever arms.

So the gear box, in effect, functions to increase the lever arm. That I understand, though I still don't understand the physics of how that happens, because there really isn't a lever.

I think I need to just shut up and accept it as fact since somebody way smarter than I figured it out long time ago.

 

[pappy]

...and conversely, how a 2.4L Formula 1 engine can make 800 HP @ 19,000 RPM but a max torque of only 200 lb-ft @ 17,000

Which is a function of the length of the crank arm (relative to piston diameter). In general, engines with shorter crank arms make less torque, but are able to spin faster. Engines with longer cranks make more torque, but don't spin as fast.

IE, the difference between a Honda engine and a 2F. We make the same HP, but I'll out pull them.

 

[1911]

So the gear box, in effect, functions to increase the lever arm. That I understand, though I still don't understand the physics of how that happens, because there really isn't a lever.

The leverage in a gear box comes from the different diameters of the gears; a small gear turning a large one has a lot of leverage, compared to gears of equal sizes.

 

[pappy]

The leverage in a gear box comes from the different diameters of the gears; a small gear turning a large one has a lot of leverage, compared to gears of equal sizes.

OK, that makes sense.