Li'l Blue: the amazing independent-suspension Jeep Wrangler experiment
"Li'l Blue" was a "cost no object" demonstration of how an independent suspension can exceed the mobility of a live-axle or Hotchkiss suspension. It was one of three prototypes competing to become the 1997 Jeep TJ:
All of these prototypes would increase the TJ's mobility, and each one was rooted in Jeep engineering:
Bob Sheaves wrote,
Why would they even bother to make a Jeep with an independent suspension? Generally, because:
There were good reasons for using a Hotchkiss suspension on the CJ and Wrangler, as well:
The team working on Li'l Blue started by researching the 1963 Jeep Wagoneer design; its independent front suspension was the first of its kind, but it did have shortcomings, which Evan Boberg, Bob Sheaves, and Gerry Hentschel addressed. They started out with a deDion independent suspension, but, to increase wheel travel and ground clearance, connected the differential to the suspension so that it travelled with the wheel. This is illustrated by the following patent drawings; Evan Boberg and Gerald Hentschel were registered as inventors for Chrysler Corporation in the 1993 application.
One of the clever aspects of the system is that in cases where one wheel was particularly loaded, e.g. if one side of the vehicle was going over a rock or into a ditch, the differential would be pulled up by that wheel, providing better ground clearance regardless of which side was higher. This helps to counter the independent suspension's issues with jounce and rebound.
Evan Boberg wrote, in his book Common Sense Not Required, that for an independent front suspension to have the same off-road capability as a Hotchkiss design, wheel travel had to be increased to about 12 inches.
Even the light CJ-5 had well over 300 pounds of unsprung weight. with the same width, the new "Long Travel" independent suspension slashed unsprung weight down to roughly a third -116 pounds.
There were downsides - among other things, conventional lift kits would not work, and getting even better ground clearance would have been very expensive, if it could be done at all. The major limit of the suspension is the ability of the powered joints to hold together; the joints can only bend so far while under power.
Li'l Blue vs the KL Cherokee and other IFS designs
Former Jeep/Truck engineer "JTE" wrote:
There was no question about the performance, according to Mr. Sheaves:
PPED was the advanced engineering group, which did the "what if" studies for Jeep and truck, such as the Jeep Dakar and Dodge T-Rex. Fully 90% of the stuff we looked at never even became mule builds. The group was there to answer "what if" questions, and come up with 80% feasible vehicles to hand off to production groups when approved.
Dodge Durango came from an idea of taking the Dakota and making a smaller version of the already-nixed Mexican "Adventurer," or Ramcharger replacement. It took Tom Gale to tie it all together by using minivan taillights and other off-the-shelf parts, to get under the budget and actually start a program.
Bob Sheaves wrote that the estimated production cost for the components alone was about $210 per vehicle more than the YJ Hotchkiss suspension, based on a production build quantity of 50,000 vehicles per year for five years. The retail cost for the 1997 Wrangler would have been around $1,000 over and above the normal retail price - which started at $12,000. At the time, that cost penalty was hard to overcome; today, it would likely be lower.
Mr. Sheaves wrote, "In those days, a four-inch lift kit would cost around $350 (installed) to fit the same size tires. The suspension we designed was modular and could have been sold by Mopar Performance at the time. Evan and I even talked to Shep and Jerry, and did a cost projection for them - $5,000 [in 1996 dollars] for the kit. It was deemed too expensive for Mopar Performance; they believed it would not sell."
That leads to the question of whether it would be practical today - and the answer, surprisingly, is that it might be. The Wrangler's popularity has grown despite price hikes; the off-road-focused Rubicon model has been much more popular than product planners thought it would be. The factory could assemble both versions on the assembly line, so that the independent suspension could be offered as an option, either on Rubicon or a special model. Advances since 1993 could cut costs somewhat; and, if all Wranglers were built that way, the factory might be able to boost its speed, since suspension modules could be built elsewhere and shipped in.
Mr. Sheaves added:
The big question, other than convincing Jeep and Chrysler leaders to give a green light, is whether the system could work with the current powertrain. From a straight-six engine with plenty of room on the sides, Wrangler has gone to a V6; packaging everything in would be quite a challenge, though Mr. Sheaves wrote, "You can use a V-type engine as long as you watch out for the packaging. If it has a long stroke, you either jack the engine higher on the frame or body, or you modify the ring gear and carrier housing."
Li'l Blue was a mind-stretching exercise in 1993, which ended up ready for actual production. It's been biding its time, but it remains a practical alternative to the more traditional designs used in Wrangler today.
Postscript
In October 2013, Bob Sheaves added:
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"Li'l Blue" was a "cost no object" demonstration of how an independent suspension can exceed the mobility of a live-axle or Hotchkiss suspension. It was one of three prototypes competing to become the 1997 Jeep TJ:
- Li'l Blue, built mainly by Bob Sheaves and Evan Boberg of the Pre-Program Group, with the Parkway plant's Quality Control staff;
- Red Devil, a medium-cost link-coil mule made under Craig Love's leadership in Vehicle Development; and
- Screaming Yellow Chicken, a low-cost, long-leaf design built by the Production group at Jeep-Truck Engineering (JTE).
All of these prototypes would increase the TJ's mobility, and each one was rooted in Jeep engineering:
- The Screaming Yellow Chicken was essentially an adaptation of the current Wrangler;
- The Red Devil was based on the Cherokee and Grand Cherokee; and
- Li'l Blue had its roots in the 1963 Jeep Wagoneer, the world's first independent-suspension 4x4.
Bob Sheaves wrote,
How Li'l Blue worked
Why would they even bother to make a Jeep with an independent suspension? Generally, because:
- The Hotchkiss suspension used by CJ and Wrangler had a large amount of unsprung weight; in general, the higher the unsprung weight, the worse the on-road handling.
- The wheels can react independently, so that one wheel hitting an obstacle does not affect both sides (one cause of wheel shimmy, or "the death wobble").
- Having the wheels react independently to obstacles also means that all four of the wheels are always on the ground, in normal on-road and most off-road driving (within the limits of suspension travel). This helps to maintain stability and steering control.
- Independent suspensions can generally be built as a unit and shipped to the factory, speeding installation and sometimes cutting costs.
- Lower cost
- Vertical wheel travel (articulation) is harder to increase in an independent suspension, due to the limits of powered joints - the angles of the joints are firmly limited.
- When the wheels travel independently, ground clearance is reduced when the car rebounds from a bump.
- With the Hotchkiss design, simple methods can be engineered to increase to increase ground clearance
The team working on Li'l Blue started by researching the 1963 Jeep Wagoneer design; its independent front suspension was the first of its kind, but it did have shortcomings, which Evan Boberg, Bob Sheaves, and Gerry Hentschel addressed. They started out with a deDion independent suspension, but, to increase wheel travel and ground clearance, connected the differential to the suspension so that it travelled with the wheel. This is illustrated by the following patent drawings; Evan Boberg and Gerald Hentschel were registered as inventors for Chrysler Corporation in the 1993 application.
One of the clever aspects of the system is that in cases where one wheel was particularly loaded, e.g. if one side of the vehicle was going over a rock or into a ditch, the differential would be pulled up by that wheel, providing better ground clearance regardless of which side was higher. This helps to counter the independent suspension's issues with jounce and rebound.
Evan Boberg wrote, in his book Common Sense Not Required, that for an independent front suspension to have the same off-road capability as a Hotchkiss design, wheel travel had to be increased to about 12 inches.
Bob Sheaves wrote,
One of the advantages was the ability to take bumps in stride, which would have thrown the CJ off kilter. Crossing a parking-lot curb at 30 mph, at a 45° angle, would flip a CJ; Li'l Blue was tested at 60 mph "and we didn't even feel it." The calculated speed to roll when hitting the curb at 45° was 84 mph. The suspension would have boosted the off-road capability beyond the CJ series, eliminated the instability problems, and dramatically improved on-road handling.
Even the light CJ-5 had well over 300 pounds of unsprung weight. with the same width, the new "Long Travel" independent suspension slashed unsprung weight down to roughly a third -116 pounds.
There were downsides - among other things, conventional lift kits would not work, and getting even better ground clearance would have been very expensive, if it could be done at all. The major limit of the suspension is the ability of the powered joints to hold together; the joints can only bend so far while under power.
Li'l Blue vs the KL Cherokee and other IFS designs
Former Jeep/Truck engineer "JTE" wrote:
The Jeep 4.0 liter engine was offset to the right side of the frame rail, to provide clearance for the steering gear and left-hand frame inner web and lower frame. The limit of jounce travel was set by the sweep of the engine crankshaft (the 4.0 was raised by 1.25 inches from stock). Mr. Sheaves wrote, "We took a 'Ford fixer' (big hammer) to the oil pan to clear the mounting ears; these changes let us set the bottom of the frame rails to not interfere with engine roll or various supension parts under full torque or other extreme conditions."
There was no question about the performance, according to Mr. Sheaves:
Why it was not produced - and whether it still could be
PPED was the advanced engineering group, which did the "what if" studies for Jeep and truck, such as the Jeep Dakar and Dodge T-Rex. Fully 90% of the stuff we looked at never even became mule builds. The group was there to answer "what if" questions, and come up with 80% feasible vehicles to hand off to production groups when approved.
Dodge Durango came from an idea of taking the Dakota and making a smaller version of the already-nixed Mexican "Adventurer," or Ramcharger replacement. It took Tom Gale to tie it all together by using minivan taillights and other off-the-shelf parts, to get under the budget and actually start a program.
Bob Sheaves wrote that the estimated production cost for the components alone was about $210 per vehicle more than the YJ Hotchkiss suspension, based on a production build quantity of 50,000 vehicles per year for five years. The retail cost for the 1997 Wrangler would have been around $1,000 over and above the normal retail price - which started at $12,000. At the time, that cost penalty was hard to overcome; today, it would likely be lower.
Mr. Sheaves wrote, "In those days, a four-inch lift kit would cost around $350 (installed) to fit the same size tires. The suspension we designed was modular and could have been sold by Mopar Performance at the time. Evan and I even talked to Shep and Jerry, and did a cost projection for them - $5,000 [in 1996 dollars] for the kit. It was deemed too expensive for Mopar Performance; they believed it would not sell."
That leads to the question of whether it would be practical today - and the answer, surprisingly, is that it might be. The Wrangler's popularity has grown despite price hikes; the off-road-focused Rubicon model has been much more popular than product planners thought it would be. The factory could assemble both versions on the assembly line, so that the independent suspension could be offered as an option, either on Rubicon or a special model. Advances since 1993 could cut costs somewhat; and, if all Wranglers were built that way, the factory might be able to boost its speed, since suspension modules could be built elsewhere and shipped in.
Mr. Sheaves added:
One method which allows longer half shafts with an east-west powertrain is to use a 3 gear (to keep the wheels turning in the same direction) drop box at each shaft flange on the transaxle. By lowering the attachment of the halfshaft, and canting the boxes (to allow the halfshafts to pass by each other to drive the opposite side), you can increase the length of the shafts by around 12 inches, lessening the angularity of the inner tripod joint, and thereby allowing grester travel. There are downsides to this, however, not the least of which is much higher cost.
The big question, other than convincing Jeep and Chrysler leaders to give a green light, is whether the system could work with the current powertrain. From a straight-six engine with plenty of room on the sides, Wrangler has gone to a V6; packaging everything in would be quite a challenge, though Mr. Sheaves wrote, "You can use a V-type engine as long as you watch out for the packaging. If it has a long stroke, you either jack the engine higher on the frame or body, or you modify the ring gear and carrier housing."
Li'l Blue was a mind-stretching exercise in 1993, which ended up ready for actual production. It's been biding its time, but it remains a practical alternative to the more traditional designs used in Wrangler today.
Postscript
In October 2013, Bob Sheaves added:
Comments? Want to learn more? Visit our Li'l Blue forum thread.
Related Jeep Wrangler pages Inside the Wrangler
Years Background Variants and related... |
The 2018 Jeep Wrangler JL: suspension • aluminum vs steel • open or fixed roof • pickup
body engineering • weight, strength, and safety • transmissions • engines
Trucks/SUVs
Jeep
Ram
Military
Engines
2015-2017
Forums
Home •
Engines •
Reviews •
Chrysler 1904-2018 •
Upcoming •
Trucks •
Cars
Spread the word via <!--Tweet or--> Facebook!
We make no guarantees regarding validity or accuracy of information, predictions, or advice - .
Copyright © VerticalScope Inc. All rights reserved. Dodge, Jeep, Chrysler, Ram, and Mopar are trademarks of Fiat Chrysler Automobiles.