Hacked jeep vs a tag axle hitch

[Tour1]

Recently some computer hackers showed that they could invade a jeep's computer and remotely operate things, in particular the brakes. The short wheelbase jeep has an anti sway control that operates the left or right side brakes unequally to make it go straighter if it starts to do bad things. The hacker made it do a bad thing and of course if there was a mechanical or electrical problem.
The builder rates my Liberty at 2000 lbs towing without the anti sway or 5000 lbs with it factory installed. There is no dealer or home installed version.

So I am wondering if any of you have ever seen, heard of, or even thought about bolting a tag axle on to a short wheelbase tow vehicle to stabilize it and/or increase the rated tow?
The turning radius would change, I think, maybe front wheel alignment wouldneed adjustment on installation. Also since braking ability depends on tire loading, the axle would need coordinated brakes on it.

The load budget would go up by 3000 lbs so if the thing weighed 1000 it would still add a ton of tow, and it seems like the amenities increase dramaticly as trailers go over the 2000 lb mark. It would be best to have an easily dettached setup like maybe 3 or 4 reciever hitches but it would have to be proven workable first.

[burningman]

You could have more of both, there are plenty of rigs that off-road better than that van that could tow even more.
A tag axle can work and in fact they sell them. Look up the Trailer Toad, and there are others too.
In your situation I wouldn't do it, I'd do what you did and get a stouter vehicle.

[Tour1]

I feel silly sometimes when I post a reply without reading the 2nd or 3rd page of a thread so I understand how you missed it when I said I bought something bigger, stronger, heavier, etc.
But to answer your question, when I went to trailer dealers I often heard stuff like "my liberty towed 3500 lbs easily" or "the tow package is just a brake controller and we can install that". The language in the 2012 Liberty owner's manual denies those possibilities, as did the MOPAR parts people. However, being an american infused with the history of innovation and ingenuity of my heritage, I asked if a particular modification was ever tried. I appreciate all the advice I've gotten and I'll be popping another question somewhere else soon.
I just have to say, though, after 2 trips to the undeveloped property, the Econoline is no Jeep. I feel no shame at all for wishing I could have a little bit of both.

[Grit_dog]

First what does the hack have to do with your question?
Second, say whaaaaaat? Just go buy something that will tow more if you need more towing capacity, unless you want to ruin a perfectly good jeep and have a Frankenstein 6 wheeler. I can fab a lot of stuff and can't even think how to start an endeavor like that or see any return on investment or even how it sounds like a good idea.

Anything from a slightly bigger jeep to a F350 dually and everything in between would be better than a home made tag axle IMO.

[dodge_guy]

You cant "hack" a car unless it has connection via wifi. and even then with a liberty you can only do certain things with the brakes, transmission or engine with the truck in Park.

[Tour1]

Epilog: Traded in the 2012 Jeep for a 2013 E350 passenger van. It's rated for 5000 pounds & up when properly equipped, aftermarket parts allowed, and it has pretty good ground clearance. The downsides are 15 mpg highway without a trailer, a large turning radius, and it will be tough to pull snow off the roof.

Bonus features are flex-fuel so I can try that E85 currently saving $0.60 a gallon) and more room inside. I'm not going to go "Class B" with it, it's a low roof model that fits in 7 foot parking garages, but I might try to swap some seats for a bunk or what-ever. Best wishes to the guy who gets my Jeep.

[Tour1]

Just to finish beating that dead horse I googled and figured a few things and this is what I got:
Tag axle alignment effects:
Standard perfect alignment is with all wheels rotating on circles centered on a single point. The tie rod and crank arm geometry cause the turned wheels' axle lines to intercept at a point on the line that goes through the rear axle. Note that a degree or two of toe-in would make the angle formed by the front wheels' axles narrower and move the apex further away and behind the axle. A degree or two of toe-out would open the angle formed by the front wheels' axles while moving the apex in closer and in front of the axle. A car I fiddled with was harder to turn when it had toe-in and hard to keep straight with toe-out.
There might be a picture at http://langexkft.eu/angol/services/a_wheelalignment.htm

On a lego website http://sariel.pl/2008/12/8-wheeler/ there is a diagram of a 4 axle truck:
The centerline between the two axles is shown as the line the apex would be on for perfect alignment. So, if a tow vehicle had some toe-in based on the original axle it would be like having less toe-in when the tag axle was added. I expect then that there would be a little less stability with the tag axle added and no wheel alignment changes.
An alternative source of instability for short wheelbase tow vehicles would be the high nose effect when power is applied. During high speed towing the nose may be constantly raised so that the tie rod ends are deflected downward and the net effect is like shortening the tie rod to create toe-out. It may be what causes the dramatic swaying and roll-overs of some tow-trailer combinations. A tag axle geometry could help keep the tow vehicle level, maintaining the best steering geometry.
Some of the numbers involved are these:
2012 Liberty wheelbase: 106.1 inches
2012 Liberty track: 61 inches

2012 Grand Cherokee wheelbase: 114.8 inches
2012 Grand Cherokee track: 64 inches

Liberty existing wheel approx. 30” OD
Liberty clearance under tail approx. 17” (say 16” OD)
With 4” tread-tread, ctr-ctr = 15+4+8 = 27”
Half would be 13.5”
Added to the Liberty wheelbase it would become 119.6”

Wheelbase ratios: GC/Lib=1.082, LibTA/GC=1.042, LibTA/Lib=1.127
Small tire capacity: ST175/80D13 is about 24” OD and should hold 1,360 lbs each

I'm not the guy who can build a tag axle for a jeep especially if I'm getting my info from lego builders, but I wish I could buy one. A normal person would just buy a bigger tow vehicle, and it's likely I will do that, but I'll have to drive that bigger vehicle for the 350 days a year that I'm not towing anything. The big well equipped trucks also come with a lot of stuff that I don't think I'll need ever really.

That's it I guess, thanks for the efforts, guys, as always.

[Turtle_n_Peeps]

Tour1 wrote:
Is anybody out there familiar with the automotive engineering of multiple axle vehicles? When there are 2 non-steering axles at least one of them will be slipping in a turn, maybe both in opposite directions. Is it only a low speed tight corner thing or does it come into play on the interstate? What is the effective wheelbase of the vehicle? I'd guess the average of both axles if they were equally loaded. The whole trailer sway issue would be moot if they always went straight.

Here's one you can read about.

And only a half a mill! Oops, too bad they are out of production.

To answer your question. Yes a tandem axel vehicle will scrub the tires at low speed, high speed or any speed. It will just depend on how much you are turning as to how much scrub you will get. The pivot point will be between the two axels.

[Tour1]

Is anybody out there familiar with the automotive engineering of multiple axle vehicles? When there are 2 non-steering axles at least one of them will be slipping in a turn, maybe both in opposite directions. Is it only a low speed tight corner thing or does it come into play on the interstate? What is the effective wheelbase of the vehicle? I'd guess the average of both axles if they were equally loaded. The whole trailer sway issue would be moot if they always went straight.

[mkirsch]

pconroy328 wrote:
Found it:


That’s true: Miller and Valasek had worked on their Jeep hacking exploit for over a year. “The software manipulation addressed by this recall required unique and extensive technical knowledge, prolonged physical access to a subject vehicle and extended periods of time to write code,” reads Chrysler’s statement.

That's how hacking works. You get an example of what you want to hack, then you pound away at it until you find a vulnerability.

Once the software is written they can use it to access any vehicle that's vulnerable to the exploit. They don't need physical access to EVERY vehicle.

[crcr]

Those Chrysler vehicles that are vulnerable to hacking have been recalled:

Story here.

[Tour1]

Sch911, I think they'll let me have any necessary cooling upgrades.
I forgot some of the details since this idea has been stewing for a long time.
I imagine the tag axle would have 60 psi trailer tires smaller than the vehicle's regular tires and each would have its own fender. An air bag suspension would support the tongue weight and push the vehicle nose down. The tag axle would have the receiver hitch for the trailer on it and be attached to the tow vehicle by at least 2 receiver hitches, not normal ones but one under each frame rail.
As for the hack, I think time and corrosion will accomplish the same thing eventually. I had wacky electric issues with a Montana minivan including a speedometer that gradually re-adjusted itself while I drove in the rain.

[n7bsn]

AndyW wrote:
They needed prolonged physical access to CREATE their exploit. As in, a vehicle they could reverse engineer to figure out how everything worked. Once created, they could hijack ANY similar model vehicle without physical access.

That is why this particular demonstration was novel - past vehicle hacks have all required physical access to the ACTUAL vehicle being hijacked.

Correct, if you read the entire Wired article you will note them IDing (via the vehicle's connection to Sprint's 4G network) additional vehicles that they could exploit via the same exploit.
These vehicles were physically remote and had never been accessed

[AndyW]

They needed prolonged physical access to CREATE their exploit. As in, a vehicle they could reverse engineer to figure out how everything worked. Once created, they could hijack ANY similar model vehicle without physical access.

That is why this particular demonstration was novel - past vehicle hacks have all required physical access to the ACTUAL vehicle being hijacked.

[pconroy328]

Found it:


That’s true: Miller and Valasek had worked on their Jeep hacking exploit for over a year. “The software manipulation addressed by this recall required unique and extensive technical knowledge, prolonged physical access to a subject vehicle and extended periods of time to write code,” reads Chrysler’s statement.