Locking up a solid shaft Syncro for crosswind stability?

[raoul mitgong]

The little triangle above the horizontal line is where the front wheels pull forward. "On" the graph's horizontal line is the threshold road curve where front is in balance with rear wheel spin and zero torque is transferred to the front tires. Below the horizontal line is where the steering wheel is turned enough to cause fronts to "brake".
Left or right of the vertical line represents steering wheel rotation and on the vertical line is straight ahead.
-d
_________________
84 Westy with a 2.1 (Groover)
86 Tintop Syncro (Crow)
86 Tintop Syncro to Westy project (Tom Servo)
91 Westy (Only the top 12 inches of this van (a burn victim))

[Sodo]

DJKeev this is why I started a NEW THREAD. Plus the OP doesn't want this in his topic (and Jon_S too) but we're in an armwrestle and he's reluctantly mumbling 'uncle'. Jon's unrepentant.

OK back to page 1. ......

[IdahoDoug]

Ah, not so fast on those slippage figures.

The only ones you've posted so far showed much less slippage than that, and THAT was achieved at an acceleration level that the Vanagon can probably not achieve. What we should rightly be looking at is steady state 70mph figures.

You just stacked the deck with the least grippiest type tires (Mud terrain), used slippage numbers for a more powerful car, and that car is accelerating very briskly. Right? The most slippage you can possibly get away with to start the conversation.

I assume we are talking about a Syncro with a locked solid shaft that is doing 70mph steady state and encounters side wind strong enough to cause it to shift around and the owner says "Hmm, I think I'll lock up the decoupler so that whenever I get pushed around and steer the front tires will brake ever so slightly and stabilize me with 4 contact patches under tension." So I think we need to start with numbers that are much closer to that scenario. Steady state.

Further, and I admit this is a side show, you put red lines through those graphs a few pages back, and interpreted them with those lines. The second acceleration's slip data is not that different from the first grouping at lower speeds but you intentionally just nicked the top of the data group up high at 3% and declared that group "3% slip". And its important to know - was this car's data a FWD or a RWD because the slip of a FWD is much higher. Statistically, since some 90% of cars these days are FWD, that's from a FWD car.

Might I suggest we look for slip data for a RWD car at steady state freeway speeds? Then we will arm wrestle over small variables like tire type, etc.
_________________
1987 2WD Wolfsburg Vanagon Weekender "Mango", two fully locked 80 Series LandCruisers. 2017 Subaru Outback boxer. 1990 Audi 90 Quattro 20V with rear locking differential, 1990 burgundy parts Vanagon. 1984 Porsche 944, 1988 Toyota Supra 5 speed targa, 2002 BMW 325iX, 1982 Toyota Sunrader

[Syncro Jael]

I too could never find any information about tire slipping on a Vanagon. I can't imagine it is anywhere near the examples shown for 2wd vehicles. It weighs to much and has much less horsepower than autos today. Just my thoughts.
_________________
1987 Syncro Westfalia Hightop - NAHT
Subaru EJ25 Forged Frankenmotor, Triple Knob.
Jael = (Mountain Goat)

[raoul mitgong]

Doug,
Sodo admitted he thought the number was high at 3% and that this was an easy number to divide for ease of understanding (which I think is a good idea considering it took 10 pages to get here).
No one claims 3% is accurate and we won't let it become a default just to win an argument. Using 1.863% slippage for example will not be fun to play with. Let's move on.
-d
_________________
84 Westy with a 2.1 (Groover)
86 Tintop Syncro (Crow)
86 Tintop Syncro to Westy project (Tom Servo)
91 Westy (Only the top 12 inches of this van (a burn victim))

[Sodo]

[Sodo]

BTW is this how the Mutha Decoupla thread went? This makes it difficult sort of.

Why cant we just "go after it" and talk about Syncros, bring whatever you can that pushes forward to gain deeper understanding. Why does any deck need stacking? Why are we suppressing slippage? Why would you WANT the conclusion to be one way or the other? Don't we just want the truth, to make the best decisions?

The Mutha Decoupla thread might have some good info but I am afraid of opening it.
_________________


'90 Westy EJ25, 2Peloquins, 3knobs, pressure-oiled GT mainshaft, filtered, cooled gearbox
'87 Tintop w 47k 53k, '12 SmallCar EJ25, cooled filtered gearbox
....KTMs, GasGas, SPOT mtb

[IdahoDoug]

Sodo,

Good point and I agree completely. I think we all want "practical science" here versus splitting of hairs. My whacking you with a wet noodle on the 3% is because that's crazy slippage. I don't have the studies we built, and I statistically analyzed and wrote the reports on, but I recall slippage of steady state driving that was not even a single digit. Fractions.

Stop and think what even 1% means. That means for every 100 turns (600 feet) the driven tire slips one full revolution. That's 10 full slipping revolutions in a mile. In Tom's 600 mile trip for fun with the center locked, that is 6000 full revolutions!! There is no accounting for that wear as "at higher speeds the tire is able to better account for slip". No sir. That is massive wear. And remember, that means both rear tires are slipping like that. BOTH OF THEM.

So the 3% slippage you want to start with means in the length of a football field both rear tires slip a full revolution. 20 full slipping revolutions in each mile.

I don't want to be splitting hairs here, but if you won't allow my experience to guide things into a reasonable range to discuss then you are going to waste a lot of time. I know how these threads go and we've just witnessed it. I clearly showed that the entire motoring world says "Don't drive a vehicle with locked axles on pavement because the dragging front tires cause dangerous binding in the drive train because on a curve the fronts MUST rotate faster than the rears". Then you started the new thread on slippage by confidently stating that you drive with your front wheels pulling on dry pavement. Which means you "forgot" that your front wheels go faster than your rears on normal dry pavement already.

If I ignore the 3%, by page 5 on this thread, 3% will have become the defacto number. It's not. Nowhere near that number - I promise you.

Let's talk about slippage. Nobody has slippage numbers yet and I hope to have some time to look around the net tonight. But starting at 3% is well beyond the realm of reality for steady state driving. I don't even think a Vanagon doing a quarter mile race including dumping the clutch at redline on each shift can rotate the rear tires 5 full revolutions on a 1/4 mile drag strip. Do you? That's what 3% looks like.
_________________
1987 2WD Wolfsburg Vanagon Weekender "Mango", two fully locked 80 Series LandCruisers. 2017 Subaru Outback boxer. 1990 Audi 90 Quattro 20V with rear locking differential, 1990 burgundy parts Vanagon. 1984 Porsche 944, 1988 Toyota Supra 5 speed targa, 2002 BMW 325iX, 1982 Toyota Sunrader

[Syncro Jael]

I remember watching these previously and found them again. For those of us that are not "engineers" it will give some background as to what will be talked about.

https://www.youtube.com/playlist?list=PL6R7zR4ZbGkMVF_-Tdb4BFrpuoavxGT3I

https://www.youtube.com/playlist?list=PLbMVogVj5nJTW50jj9_gvJmdwFWHaqR5J

Grab a bag and enjoy the videos.


_________________
1987 Syncro Westfalia Hightop - NAHT
Subaru EJ25 Forged Frankenmotor, Triple Knob.
Jael = (Mountain Goat)

[Sodo]

[IdahoDoug]

So I say 1% slippage for driving at a steady 70mph would be still unreasonable on a RWD vehicle with extremely low power, and the weight of the engine atop the drive wheels and the air pressure of traveling with a flat tall front end at 70 transferring yet more weight onto the drive wheels (giving them better traction/less slip). The Vanagon could rightly be called the poster boy for low tire slip.

However, you like 3% which as I pointed out is 30 full tire revolutions per mile at steady state 70mph.

So lets compromise at a crazy 20 revolutions per mile or 2% slip.

Also, you keep using 75mph and I keep using 70mph. Pick one and git er done.

Doug

PS - the burnout example of a quarter mile run was not intended to confuse. It was to explain my point that a Vanagon under its full acceleration probably cannot turn the tires 5 revolutions in a quarter mile, much less driving at 70 steady state. And yes I realize since you want 75mph it is closer to the Vanagon's max HP while its steady state cruising, but I'm in a charitable mood. Next you're going to nick me with a requirement that the Syncro be empty of fuel, be a nonWesty, and have no cargo aboard in the luggage area to reduce static friction..... Heh, heh, heh......
_________________
1987 2WD Wolfsburg Vanagon Weekender "Mango", two fully locked 80 Series LandCruisers. 2017 Subaru Outback boxer. 1990 Audi 90 Quattro 20V with rear locking differential, 1990 burgundy parts Vanagon. 1984 Porsche 944, 1988 Toyota Supra 5 speed targa, 2002 BMW 325iX, 1982 Toyota Sunrader

[IdahoDoug]

OK, I'm not getting it to compute and it looks like you guys are right.

At a circle 5 miles in diameter, the Vanagon would have to have the fronts describe a circle 264 feet larger in radius in order to make my contention work at 2% rear wheel slip true. Not happening.

At a circle 1 mile in diameter, the fronts would have to describe a circle 53 feet larger at 2% wheel slip. Also not happening.

At a circle 1000 feet in diameter, the fronts would have to describe a circle 10 feet larger at 2% slip. Still not happening.

At a circle clear down at 300 feet in diameter, the fronts would have to describe a circle 3 feet larger at 2% slip. Still not happening.

Its not until we get down to a circle 50 feet in diameter that the circle is tight enough that 2% slip would cause binding. Meaning the circumference of the circle the fronts describe is 2% longer and the radius is 1 foot larger than the circle the rears describe. That's doable on paper. How'd you guys do? I can't find my HP and doing this the normal way is killing me!
_________________
1987 2WD Wolfsburg Vanagon Weekender "Mango", two fully locked 80 Series LandCruisers. 2017 Subaru Outback boxer. 1990 Audi 90 Quattro 20V with rear locking differential, 1990 burgundy parts Vanagon. 1984 Porsche 944, 1988 Toyota Supra 5 speed targa, 2002 BMW 325iX, 1982 Toyota Sunrader

[WestyBob]

[Sodo]

I will be really surprised if tire/asphalt/atspeed interface has an efficiency of power transfer better than 98% (= 2% slippage), and more surprised if better than 99% at 70mph. But I have nothing to go on - just a hunch (for now). The equations show more speed = increased slippage.

Need someone to measure the curve radius of the "1/4 steering wheel turn". Not that it applies to the highway discussion, but it's in the original GoWesty paper. We're not doing tight turns though we're on the freeway. And nobody's turning 1/4 turn at 75MPH - certainly not twice in the same van.
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'90 Westy EJ25, 2Peloquins, 3knobs, pressure-oiled GT mainshaft, filtered, cooled gearbox
'87 Tintop w 47k 53k, '12 SmallCar EJ25, cooled filtered gearbox
....KTMs, GasGas, SPOT mtb

[jackbombay]

[Sodo]

[WestyBob]

[Sodo]

Doug doesn't love us anymore.
Or he's out shopping for his own Utilikilt.
Doug lets see a pic in your Utilikilt, with a squirtgun in your sock.
Wait...... scratch that!
_________________


'90 Westy EJ25, 2Peloquins, 3knobs, pressure-oiled GT mainshaft, filtered, cooled gearbox
'87 Tintop w 47k 53k, '12 SmallCar EJ25, cooled filtered gearbox
....KTMs, GasGas, SPOT mtb

[jackbombay]

[Sodo]