Bridge Law Chart.. Rand Mcnalley

Topic 14115 | Page 1

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Frito's Comment
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So I visited one of our company cookouts today and attended the safety meeting offered. I approached the safety guru after the meeting to gain some clarity on the bridge law versus the states kingpin spacing requirements. While asserting that they were two different concepts and seeking advice on just how to affirm that post scale I am " bridge law legal" he got short with me stating that the kingpin distance and bridge laws were the same thing and that if I wanted to give the concept so much thought perhaps I shouldn't have gotten into trucking. I'm seeking advice on how to apply the chart on page A15 of the atlas to my standard semi-trailer set up. I'm finding it a bit confusing. When I pop off the cat scale I want to be able to quickly reference this chart and my 41' mark and be able to say with confidence... Yep I'm legal. Thanks for any insight/advice.

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In fact, CAT Scale offers an unconditional Guarantee:

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Michael S.'s Comment
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Bridge law: W=500(L*N/(N-1) + 12*N + 36) where W = weight permitted in pounds, L = distance between outer axles of a set of axles, N = number of axles. W is rounded to the nearest 500 lbs

If you have two drives axles on a tractor and trailer with a moveable tandem your axle weights allow 68,000#, so solving for

68000<500(L*4/(3) + 48 + 36)

we get L > 39.

Any distance between tractor and trailer tandems that's greater than 39 feet is legal. Is 41' from kingpin to rear axle greater than 39'?

Tandems:

Tandem Axles

A set of axles spaced close together, legally defined as more than 40 and less than 96 inches apart by the USDOT. Drivers tend to refer to the tandem axles on their trailer as just "tandems". You might hear a driver say, "I'm 400 pounds overweight on my tandems", referring to his trailer tandems, not his tractor tandems. Tractor tandems are generally just referred to as "drives" which is short for "drive axles".

Tandem:

Tandem Axles

A set of axles spaced close together, legally defined as more than 40 and less than 96 inches apart by the USDOT. Drivers tend to refer to the tandem axles on their trailer as just "tandems". You might hear a driver say, "I'm 400 pounds overweight on my tandems", referring to his trailer tandems, not his tractor tandems. Tractor tandems are generally just referred to as "drives" which is short for "drive axles".

Michael S.'s Comment
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Ha, I didn't put in the calculations for the whole truck:

80000<500(L*5/(4) + 60 + 36)

what's the shortest distance allowed between steers and the rear axle of the trailer?

Daniel B.'s Comment
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The one and likely only time I'll ever need/want Errol around... and I can't find him!

smile.gif

Rick S.'s Comment
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7th grade dropout here.

Could you make that just a LITTLE SIMPLER?

Like - "common core simple"?

Wouldn't it be safe to assume, with your axles legal at the particular states "kingpin to tandem distance", that you would also be "bridge law legal" - as the gross weights for bridges (for a particular jurisdiction) are based on max-gross (80K) at legal kingpin distances?

Rick

Tandem:

Tandem Axles

A set of axles spaced close together, legally defined as more than 40 and less than 96 inches apart by the USDOT. Drivers tend to refer to the tandem axles on their trailer as just "tandems". You might hear a driver say, "I'm 400 pounds overweight on my tandems", referring to his trailer tandems, not his tractor tandems. Tractor tandems are generally just referred to as "drives" which is short for "drive axles".

OldRookie's Comment
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óti eínai Éllines gia ména :-)

Kurt G.'s Comment
member avatar

So it looks to me (reading that page linked above) that if tandem hole 1 leaves at least 36 feet between the front drive tire and the rear axle, then you would always be "bridge law legal".

Tandem:

Tandem Axles

A set of axles spaced close together, legally defined as more than 40 and less than 96 inches apart by the USDOT. Drivers tend to refer to the tandem axles on their trailer as just "tandems". You might hear a driver say, "I'm 400 pounds overweight on my tandems", referring to his trailer tandems, not his tractor tandems. Tractor tandems are generally just referred to as "drives" which is short for "drive axles".

Kurt G.'s Comment
member avatar

...and I don't know if it does or not, I guess I was thinking that maybe they make the trailer so the tandems can't go so far forward that you would be illegal.

Tandems:

Tandem Axles

A set of axles spaced close together, legally defined as more than 40 and less than 96 inches apart by the USDOT. Drivers tend to refer to the tandem axles on their trailer as just "tandems". You might hear a driver say, "I'm 400 pounds overweight on my tandems", referring to his trailer tandems, not his tractor tandems. Tractor tandems are generally just referred to as "drives" which is short for "drive axles".

Tandem:

Tandem Axles

A set of axles spaced close together, legally defined as more than 40 and less than 96 inches apart by the USDOT. Drivers tend to refer to the tandem axles on their trailer as just "tandems". You might hear a driver say, "I'm 400 pounds overweight on my tandems", referring to his trailer tandems, not his tractor tandems. Tractor tandems are generally just referred to as "drives" which is short for "drive axles".

Errol V.'s Comment
member avatar

The one and likely only time I'll ever need/want Errol around... and I can't find him!

smile.gif

What!? I saw this at lunch time and figured Michael had it worked out. I didn't want to butt in on his show.

And I never figured out what the bridge law thing was all about.

@Michael, with this crowd, don't say "solve for L". Just say " Re-write the inequality to get L":

L > {(N-1)/N} {W/500 - 12N - 36}

Again, just as clear as pea soup! Might as well say "я не должен научить вас плохих русских слов."

murderspolywog's Comment
member avatar

Frito, so for you to bridge out the truck you need to now the distens from stear axel to the last drive axel. Distense between both drive axels. Drive axels to trailer axels and distense between trailer axels, then the total length, all three have to bridge out, not just one set. Clear as mud? Kingpin settling are not the same as bridging a truck out. King pins are state manded settings and bridge formula is Federal. So if you can't get the bridge and kingpin to work witch one do you fallow?

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