Mathematics, Spread axles and bridge laws,

I am building a new truck/trailer combo for a specific application that will run to every state, including California. I believe I have my measurements all down, but I wanted to run it by others on here to play Devil's advocate.

We are looking at a truck, long wb with load on truck deck, and a stinger steered trailer (think auto hauler combo, but flat deck) I am never over 66,000 gross and load weight is pretty evenly spread out, this in itself would be a no-brainer, ie;

12,000 FA
34,000 RA 5 axle
34,000 TA

However, since we DO run all over, and are on quite a few toll roads it got me to thinking, what if I could run just 4 axles? for those that never have, the difference in tolls is quite a bit, not to mention 4 more tires, lighter, fuel savings etc.

So what I am hoping to do would be a single axle on the truck, and on the trailer (45') I would be looking at a 10'1" spread, it would look like this, ie;

14,000 FA
20,000 RA
20,000 FTA (front trailer axle) 4 axle
20,000 RTA (rear trailer axle)

As you can see I can easily get to my 66,000 max and still have room to spare, what I am trying to do is make use of two existing laws, the stinger-steer exemption of 75' legal EVERYWHERE (I need the added deck space), and also the 10' 1" spread axle exemption that would let me get 20,000 out of each single axle.

For you guys that deal with this all the time, do you see any bridge law issues with this spacing, Truck WB 24' center line of truck axle to rearmost trailer axle center line would be 39' front trailer axle would of course be 121" forward of RA.

I know a lot of people would just run a sliding axle flat, but because of the required deck height, I can not slide axles.

Thoughts, issues, comments, welcome.

Thanks Stan

 

Hey Bud, OVAL of T/T would be 75' same as SS autohauler, "truck" would be 30'6" long Bumper to pin, trailer would be 44'6" pin to tail, pin would be 60" from RA of truck so Cali. legal, WB would be close to the max for Cali. 282", RA of trailer would be 34' from pin.

So the layout looks like this,

Ft bumper of truck to FA,,,,,,,,,,,,,,,,,,,, 30"
FA of truck to RA,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 282"
RA of truck to pin,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 60"
PIN to first TA,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,287"
First trailer axle to second axle,,,,,,,,,,,,121"
Rear trailer Axle to End of trailer,,,,,,,,,,120"

Total,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 900" or 75' Plus, I should be allowed at least 4' ft overhang in every state without hassle, even Was.

That's how I am reading the rules, just wanted to make sure I was interpreting it correctly, I was/am just a bit skeptical about the single axle tractor and getting a "porpoise" effect over dips and bridges, but that is why I thought the spread axle setup would come in.

As you know European auto hauler have always run a SA tractor (cabover) with a set of single tire triple axles and it seems to balance?

However, they run a LOT less speed than we do (56 mph) and they don't have vehicles as heavy as I am wanting to haul, hence the dual tandem spread.

I have just never seen this setup used, and figured there must be a reason for it. Everything is a compromise, and my main concerns would be scrubbing the tires, (although there is not near the weight on the trailer that you would have on a step/flat) and overloading the rear axle on the truck, (hoping that the spread would limit the pin weight and with such a long wb some of that weight could/will be shifted to front axle.

Thanks for the reply.

 

To be honest if I was going to run a tag, I would just run the 5th axle and conventional placement on the trailer, and I may have to, just trying to push the envelope, besides, some of these #### states are charging tolls FOR the tag, even if it's up!

You have to remember, this deck, even on the truck is set at MINIMUM height, so no room to lift a tag.

I do understand your point, just trying to keep it simple.

 

Exactly, I have spent a lot of time on this whole setup, the drawing is just the base of the vehicle, it actually has 4 folding decks, so it will do 3 LARGE vehicles, up to 22' minibuses, BUT it will also do 6 cars, small vans or any combo in between.

Between the cost to build it, (close to a 10 car setup because everything has to be heavy duty), runways and ramps have to support vehicles up to 18,000 lbs. It's not something that anyone else, or very few, would utilize, but for my operation, it would be the tits.

As I said, I have looked long and hard, and have yet to find a state that this would not be legal in. I hope I'm right.

Time (and money) will tell!