Wheelbase and tailswing.

[guest]

I'm needing to get figured out exactly what wheelbase I need for my stretched truck (d unit with 24' box). It appears that I am going to have to have a lift axle to keep from excluding any of the carriers. Many seem to require 13,000 legal payload. I don't think there is anyway that I can do that without a lift axle. I don't mind the lift axle as most of the carriers will pay better when you are hauling the heavier loads.

My question is this:
Should I place the lift axle in front of the drive or behind it? I would like to put it behind the drive axle, that would take some weight off the steers when the lift axle is not in use. By my figures though, i would have app. 12' overhang and that seems like it would have a lot of tailswing to it. I went up to the high school today and measure the school buses. They have 11' overhang. I watched as they left out, turning at the light, it didn't look all that bad, but that would all change in a heavily crowded traffic jam...lol.

Does anyone have a lift axle behind the drive axle? If so, do you have any trouble with tailswing? How much overhang do you have?

I'm looking at setting the drive axle at app. 12 1/2' behind the cab. That would center it under the box. That would give me a wb of 288" to the drive. That would mean that the lift axle would be set at app. 336" wheelbase with 8' of overhang from the lift axle.

Any thoughts appreciated. I don't think it would be a problem to add more wb, but this would keep the centerline between the axles halfway close to the center of the box.

Thx, Arky

 

[Toes]

Hello again Arky,

When you ask a question, you choose a tough one for sure, don't you?

But as asked I'm not sure there is a correct answer. Not enough information given yet. I would think wheelbase is dicated by specfic needs.

As you know I just stretched the T-600, and I'll try to work from my own thoughts. The tag-axle may or may not benifit you. Again, depends on the needs.

Refresh my mind here...what is the unit you are stretching? Most important, what is the empty weight of the unit now? Axle weight?What is the PROJECTED EMPTY WEIGHT of the finished product?

Reguardless of the make of truck, I believe you're going to max. scale at 33,000 as a single axle. (You are a single axle?) (Don't ask me why, but 33,000 is the plate weight. 32,000 is allowable gross weight...12,000 and 20,000.)

So...given that, how far under 32,000 do you expect to land? The FL I just sold tared at 17,200 empty of fuel. I could scale a 14,800 pay load, on paper. (Tried to stay under 13,000) Heaviest load I carried was 13,800 and I couldn't get it legal on the axles.

I simply didn't have enough truck to carry 14, 15000 pound loads.
Not enough engine, not enough braking power.

By adding a tag, you jump right up to 34,000 on the rear. Will you have enough truck to carry the load? And in doing so, the tag in front will allow you to scale...but the bridge law will get you a heafty ticket. (You know of "Bridge Law"?)

Given that info, I favor the rear-tag approach. But then comes your question about the overhang...good thought Arky. Check the overall legenth of a school bus with long overhang. Major wheelbase. Compare against your design. Same or different?

Turning radius is your correct question. Rear tag will give up turning radius, or suffer some damage. You CAN drag it around. At the cost of a few tires and perhaps an airbag or two. (Front tag will track correctly, rear tags tend to "drag")

Any of this sound right to you? Now we'll jump in and out of your questions...


>I'm needing to get figured out exactly what wheelbase I need
>for my stretched truck (d unit with 24' box). It appears
>that I am going to have to have a lift axle to keep from
>excluding any of the carriers. Many seem to require 13,000
>legal payload. I don't think there is anyway that I can do
>that without a lift axle. I don't mind the lift axle as most
>of the carriers will pay better when you are hauling the
>heavier loads.
>
>My question is this:
>Should I place the lift axle in front of the drive or behind
>it? I would like to put it behind the drive axle, that would
>take some weight off the steers when the lift axle is not in
>use. By my figures though, i would have app. 12' overhang
>and that seems like it would have a lot of tailswing to it.
>I went up to the high school today and measure the school
>buses. They have 11' overhang. I watched as they left out,
>turning at the light, it didn't look all that bad, but that
>would all change in a heavily crowded traffic jam...lol.


See above threads. My 99 FL had a 11 foot overhang on a 24 foot box with no problem there. 300 inch wheelbase.

>Does anyone have a lift axle behind the drive axle? If so,
>do you have any trouble with tailswing? How much overhang do
>you have?
>
>I'm looking at setting the drive axle at app. 12 1/2' behind
>the cab. That would center it under the box. That would give
>me a wb of 288" to the drive. That would mean that the lift
>axle would be set at app. 336" wheelbase with 8' of overhang
>from the lift axle.

Again, more info needed. My personal thoughts...you're already stretching. What if you went longer on the drive axle wheelbase? Say, 318 (my Kenworth) and added the tag in front? With a 22 foot box, at this wheelbase, I have a 7 1/2 foot overhang. About 8 1/2 to the front.
>
>Any thoughts appreciated. I don't think it would be a
>problem to add more wb, but this would keep the centerline
>between the axles halfway close to the center of the box.
>
>Thx, Arky

BTW, I stretched for 2107.00 total cost, including box mounted. Go out next week to see if this thingy works.

Toes

 

[Weave]

About all I can tell you Arky without having a lift axle is this. It looks like you are building a truck of around the same length as mine with about the same chassis. The S60 engine is very heavy, and thus in your case you will be more or less forced to place the lift axle behind the drive as you thought to get weight off the steer. My steer axle with the trcuk unladen and half fuel capacity (150 gal) has 11,200 on it. If I were to put a drop axle on there ahead of the drive, the steer would be over 12,000 when lifted. Your cab with the condo sleeper is heavier than mine, so this situation would be worse. Most of your loads will not require the drop axle, thus having it behind the drive will be a benefit for the steer all the time, empty or under any sort of load. Even with my 320" WB, I still have enough "overhang" and frame to mount a lift axle behind my drive if I wanted to, but in the case of your build I would go with a shorter WB than that for the drive. Say maybe 280-300"? If it's something you plan into the build, you can always add it on later based on what you feel your needs will be after you get up and running on just the single drive. Probably a good 80-90% of the loads I have ran with All-State and C&M have been under 6k lbs, making the lift axle not justifiable. It would be something more oriented to a team "I live in you" truck, not so much beneficial to a solo operation, but that's up to you. Just wanted to let you know the lift axle ahead of the drive on your perticular setup would probably not work as the truck is too front heavy to start out with.
No, you will not be able to scale 13000 without the lift axle, but carriers will still be more than happy to lease on your truck. For example I believe FedEx classes trucks like mine D-C units: C unit weight capacity, D unit cargo volume.

-Weave-

 

[guest]

>>No, you will not be able to scale 13000 without the lift axle, but carriers will still be more than happy to lease on your truck. For example I believe FedEx classes trucks like mine D-C units: C unit weight capacity, D unit cargo volume.<<

This is my biggest concern. Most of the carriers show that you must be able to legaly scale 13,000. I have specificly ask 3 companys just this week if that rule was set in stone. So far, they've all said yes. Even if i find a carrier that would allow me to run as a single axle, I would hate to be excluded from running for someone else in the event I needed to change carriers for whatever reason.

As far as the D-C calssification, I've not heard of that and none of the recruiters have volunteered this information. It's a pretty tough decision to make simply because it would be a lot of trouble to start changing around later if I find that I have the wrong set-up. I feel that the safe way to go is to have the tag installed, but I would definitley avoid this extra start-up cost if I was sure it wouldn't sneak back up on me down the line somewhere.

Toes...thx for the input. The truck I'm stretching is a Freightliner Century Class with 430/470 h.p detroit, so I should have more than enough h.p for the extra weight. The tare listed on the truck is 15,000#. That means that the extra frame plus the box and the dolly legs would have to add less than 4,000# in order for me to stay legal with 13,000 load. My understanding of Tare would be the weight of the truck with no fuel at all in the tanks. I don't think I can manage to do this. I think a legal 12,000 # load might be possible, but I wouldn't bet on that even.

I am awre of the bridge law, but I'm not familiar enough with it to know how much effect it will have on this set-up. My understanding of the bridge law is that the more weight you carry = more space you must have between the axles. I'm thinking that the long wheelbase of these trucks would be beneficial where the brdge law is concerned.

The school buses actually surprised me quite a bit. Although they had 11' of overhang, the wheelbase was 250". Quite a bit less than most of the 22-24' expedite trucks.

The drag that you mention is something that I have wandered about. Weave has a good point that if I add a tag axle at all, it will almost have to be behind the drive simply because I probably can't afford to have the extra wieght on the steer axle.

Since the buses are set with a 11' overhang and Toes' truck had 11' with no serious tailswing problems, I might go ahead add another 12" to my figures on the wheelbase. My figures are now showing 288" to the drive with tag behind that. If I added the extra 12", that would be put me at the 300" mentioned a couple of times here and also reduce my tailswing to 11'. Seems that might be the best compromise.

I know that Weave's truck is 320" wheelbase and very, very simliar design to mine, so the 300" wheelbase would do wanders for the steer axle weight even if I never added the tag. Hmmmm...maybe that's the answer I'm looking for right there? What do you think? I could build it to 300" wheelbase and leave it just like that for now...add the tag later if I have to have it.

Weave, I would definitly like to know what you know about getting these trucks leased on with a payload less than 13,000#. If that is possible, I know I won't be adding a tag until I see a profit justification for it. Do you think the 300" wheelbase without a tag would cause any problems?

Thx very much to Weave and Toes for the great input. I'm really stuck on this and wasn't getting any response...lol. I was kinda worried there. :+

Thx,

 

[Weave]

I have to apologize as the companies I have ran with for the past four years have two classes- truck and van, so I'm not real abreast of what the big companies are up to now. I am however looking at a compensation sheet from Tri-State, three days old, it says:
Dock High Straight Truck: $1.10/mi 12-16 ft box, $1.15/mi over 16'. Capacity over 10,000lbs or more. Simple enough.
The other places you talked to will lease your truck on, beleive me!
They will probably just classify it as a C unit without the lift axle, but you will be paid a D unit rate if hauling cargo that requires a larger than 16' box with your 24 footer. At least that was the old custom Thing to keep in mind though is most companies who classify between a C and D unit only pay the truck a C unit rate if hauling loads under 10k lbs. You can now see where many companies like All-State and Tri-State have done away with the C-D unit thing, as it got to be very confusing once drivers leased on, and there isn't a whole heck of a lot of difference in the revenue potential between a C and D unit on the single axle level. It's acutually embarassing for me to say my dad's little 16 footer grossed about $9k more than my truck did last year!
When I talked with a fleet owner at C&M who had a Century with a lift axle, I asked him how much use he got out of it. Answer was maybe 5 times a year.
I would definitely plan your wheelbase for the lift axle, but you should "test the waters" before buying and mounting one on the truck, you might not find it a necessity. The way my truck was built was to really be kept as a single axle, so I'd go with a shorter WB then the 320", give yourself a little more room for the lift axle if you find you want it later, it's no big deal at all to add on in the future. My truck chassis originally came ordered from Freightliner with a 300" WB, the drive axle was later moved back the 20". You might have your answer there, but I don't really see why my WB couldn't have been left at the 300", it would make the truck a bit easier to corner.

-Weave-

 

[guest]

I think the 300" WB might be my best bet for keeping my options open.
I can keep it as a single axle until proven that I need the tag.

I have some companies that have the lower wieghts such as tri-state. That would be the good thing about being able to add the tag axle if needed. I f I needed to change companies later, I could add the tag then if they just refused to take it as a single. I might call a few of them up and inquire about the C-D unit arrangement.

When I re-read Toes reply, he mentions that one of his trucks was 300" WB single axle with a 24' box with 11' overhang. That tells me that the 300" is probably a pretty good dimension.


Thx for the input...I really needed it!!