Finally weighed the whole rig

[Heavymetal]

I finally pulled onto the scales at a truck stop with everything loaded and here are the totals. Front axle 9,900 lbs, drive axles 18,370 lbs, and the RV was 15,720 lbs for a grand total of 43,990 lbs. I did not have time to UN hook to get a pin weight so maybe next time. 

 

[CrazyCooter]

Another with a light front axle. Your tractor is pretty heavy too......Car on the deck?

[Heavymetal]

16 minutes ago, CrazyCooter said:

Another with a light front axle. Your tractor is pretty heavy too......Car on the deck?

You think that's a light front axle? That's 81% of the 12,200 max axle rating and yes that's with car on deck. I run tandem so I am at 45% of drive axle max and 75% on the RV axles (2 10k Dexters with duals). After see others with 7-8k on their front axles I thought I was pretty good at 9,900lbs. 

[CrazyCooter]

I'm 8k on the front with the 5th and sxs on the deck, but had not seen many tractors under 10k. I was thinking my truck was weird or something. I guess tandem accounts for the extra weight I was seeing in the combo. 

[Heavymetal]

9 minutes ago, CrazyCooter said:

I'm 8k on the front with the 5th and sxs on the deck, but had not seen many tractors under 10k. I was thinking my truck was weird or something. I guess tandem accounts for the extra weight I was seeing in the combo. 

I think once I filled my fuel tanks I added another 1,100-1,200 lbs to the front axle. I was down to 1/3 of a tank and 183 gallons when I found a good price (2.09 per gallon) they wanted 2.73 a gallon at the polit where I weighed, I refuse to pay that price. The $2.09 was two miles off I10 in Gulfport, MS. The $117 savings on fuel pays for 6 nights at a military RV park. 

[HERO Maker]

Nice.  That's the value of large tanks.

[Shallow Draft]

Quote

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Mine is that range also.  8,860  steer,  12,920 drive [single] 14,200 living quarter horse trailer. 

Goldwing was on the deck and the trailer was loaded with 3 horses, extra water and horse feed.

This was at the DOT scale in Idaho.

 

 

[Jack Mayer]

On 5/3/2017 at 10:54 PM, Heavymetal said:

You think that's a light front axle? That's 81% of the 12,200 max axle rating and yes that's with car on deck. I run tandem so I am at 45% of drive axle max and 75% on the RV axles (2 10k Dexters with duals). After see others with 7-8k on their front axles I thought I was pretty good at 9,900lbs. 

More importantly...or equally important....is the balance. Your published numbers are 35% front and 65% rear. Which is within the balance parameters that most manufacturers recommend. With more fuel you improve these numbers.

The general recommendation of most OEM manufacturers to their conversion builders is to aim for a 35-40% front axle weight. That varies some. My recommendation for an HDT RV Hauler conversion is to stick to 35% or more on the fronts, for the worst case scenario. Anything less than that requires careful consideration.

For others, note these are fully loaded "worst case" numbers. Remove the pin weight and the front obviously gains significant weight. 

[VegasFlyer]

If you need to put more weight on the front axle, just move your wallet from your rear pocket to the dashboard....

[NoDirectionHome]

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The general recommendation of most OEM manufacturers to their conversion builders is to aim for a 35-40% front axle weight. That varies some.

I'd argue that that varies enormously depending on the load on the drives.  Think about a 12K front axle with 40K drives = 23% steer weight if running at gross.

[rickeieio]

With standard width front tires, the most you can legally put on the front is 12k, and the most you can legally put on the drives is 34k (in most states).  Comes to 35%.  The 40k rating has nothing to do with weight regs.

[NoDirectionHome]

12K is 26% of 46K gross.  Maybe we're both trying to express the same thing in different ways? But i don't think so based on the original post.

[Heavymetal]

11 hours ago, VegasFlyer said:

If you need to put more weight on the front axle, just move your wallet from your rear pocket to the dashboard....

That is with my wallet in the over head, but trust me there not any money left in that thing. 

[VegasFlyer]

7 hours ago, NoDirectionHome said:

12K is 26% of 46K gross.  Maybe we're both trying to express the same thing in different ways? But i don't think so based on the original post.

When you are looking for distribution of weight on the truck axles, you don't use overall gross weight, which would include trailer axle weight..  You use the total weight of the truck and then compute front axle against the combined axle weights.  9900 /  28270 = .350.

 

Now a quick and dirty way would be to divide the 28200 by 3 and as long as the front axle is greater than  9423, you are good.

These calculations are all based on a tandem axle truck.

[Dollytrolley]

The heavy front fetish seems odd to me......but hey I am odd so....

We spend a LOT of time driving narrow twisty steep two lane or one lane "outback" roads so I take considerable efforts to "balance" the freightshaker to stay light on the steers. 

IF you stay on the freeways and main highways you have a lot of choices to pull over to the side of the road most of the time, however pulling off onto a shoulder in the outback can be a challenge and a heavy steer tire will often tend to compromise the fairly fragile shoulder structure ........these rigs are not pickups.

Now we have a advantage being tandem so we are able to compose a "balance-solution" to favor loading considerable loading to the drivers and still keep the tire patch loading reasonable.

 

Since our trucks were designed for commercial service the numbers for the drive axles are mostly derived to allow for the max allowable loading because much of the time the higher the load the better the profit potential so loading all axles equals better pay.

 

Jeff has mentioned in the past he has driven some miserable loads in commercial service, but in RV service, it seems that for the most part, we should be able to find a better "balance-solution" however once a truck becomes singled  margins of balance adjustment may involve more consideration.

Having calculated a few hundred HDT RV Weight & Balance solutions on the spreadsheets I have seen some fairly high steer axle loads and Very FEW light steer axle loads........

For the most part the more "Critical-Balance" potential is often found in the trailer and Trey will often remark that more than 50% of RV's are out of Weight limits on one or more tire patches.....

For the most part HDT's have considerable weight and balance margins for most RV service but we still become compromised if we don't pay attention to our loads.

 

Drive on........(stay clear of soft.....shoulders)

[rickeieio]

14 hours ago, NoDirectionHome said:

12K is 26% of 46K gross.  Maybe we're both trying to express the same thing in different ways? But i don't think so based on the original post.

Duh.  I divided 12/34=35% rather than 12/46=26%.  My bad.  It's been a looooonnngggg time since I got out of school.

[Heavymetal]

7 hours ago, VegasFlyer said:

When you are looking for distribution of weight on the truck axles, you don't use overall gross weight, which would include trailer axle weight..  You use the total weight of the truck and then compute front axle against the combined axle weights.  9900 /  28270 = .350.

 

Now a quick and dirty way would be to divide the 28200 by 3 and as long as the front axle is greater than  9423, you are good.

These calculations are all based on a tandem axle truck.

I was not looking at weight distribution I was looking just commenting on percentage of gross per axle, and as per your remark about being good! I'd rather be luck.......

[NoDirectionHome]

Weight distribution F/R alone is a really poor way of determining things, the way most of the haulers on the forum have their rigs set up.  Consideration should be given to the usually large distance from the hitch position to the rear axle AND that ratio to the wheelbase.  This is what determines your stability.  No not just going down the road where I'd expect almost everyone has large margins of safety.  It's in that emergency situation or limited traction scenario that you will discover the limits of your design.  Statics are a far cry from dynamics, and moments of inertia are the true determinant of your handling.  Weight distribution is a tool to "predict" but without multiplying by those moments, both vertical and lateral, you don't have a good picture.

Here is where I will commit heresy and state, "You can have good trailer stability with virtually  0 pin weight."  Not a practical trailer design, but it is theoretically possible.

Then there's the subject of "frequency" and how it effects your stability... but lets save that for another time -Steve

[Jack Mayer]

All of these comments have merit, especially NoDirectionHome's.  There is no one single measure that makes it "good" or "bad". and as pointed out above, the distance between the axle centerline and the kingpin location on the hitch is a significant factor. We snug the hitch as close as possible to the axle, which places it around 5' back from the centerline. Pins WAY back can provide for squirrely trailers, as can trailers with very light pins relative to their overall weight - no matter where the pin position is. So you have to look at the ENTIRE picture. Not just one element. 

That said, for most RVs with 18-25% pinweight you are not going to have handling issues induced by TRAILER balance. Certainly not with the pin placed where most HDT RV Haulers place it - pretty much as close behind the axle as you can. 

Move the hitch way back (cantilever it far) and then put a heavy pin weight on it - thus unloading the steers a LOT, and you will induce some issues into the equation.  But as Dolly said - none of this matters on most setups. They are well within bounds of "reasonable". 

The point of all this is to not ignore weight/balance issues if you have unusual configurations that you are considering. But for a hitch placed close to the axle,  even with the heaviest trailers, you should not have any issues at all. You will be within the load rating of your axles, AND you will have  a rational balance between them. AND you will not induce excess forces into the equation from a long cantilever if braking hard in a curve (for example).

We use the 35%  front number as a guideline. But you have to take into account the front axle rating and not exceed it under all loading conditions, AND you have to also consider the position of the hitch. LONG cantilevers are bad ju-ju. Even if you have good front weights. I'm not saying long cantilevers are impossible - just that you have to understand what you are doing, and the tradeoffs you are making. 

[Alie&Jim's Carrilite]

We have a 12k front axle.  Unhitched we have 10200 on the front axle, Hitched it drops to 9825.  This is with 3/4 tanks of fuel.  Our hitch head is directly over the rear axle on our truck.  It's an old build singled short.

[Dollytrolley]

18 hours ago, NoDirectionHome said:

Weight distribution F/R alone is a really poor way of determining things, the way most of the haulers on the forum have their rigs set up.  Consideration should be given to the usually large distance from the hitch position to the rear axle AND that ratio to the wheelbase.  This is what determines your stability.  No not just going down the road where I'd expect almost everyone has large margins of safety.  It's in that emergency situation or limited traction scenario that you will discover the limits of your design.  Statics are a far cry from dynamics, and moments of inertia are the true determinant of your handling.  Weight distribution is a tool to "predict" but without multiplying by those moments, both vertical and lateral, you don't have a good picture.

Here is where I will commit heresy and state, "You can have good trailer stability with virtually  0 pin weight."  Not a practical trailer design, but it is theoretically possible.

Then there's the subject of "frequency" and how it effects your stability... but lets save that for another time -Steve

 

N0Home makes a interesting point and I wonder how may folks can catch  the drift of what he is hinting at with his Zero-pin-weight example......

 

So......you arrive way too early in the morning and a herd of fork lifts are loading 30 crankshafts for D13 Volvo engines at 500 lbs ea.   in the back cargo door of the Buzzard-Cargo-Air-1959 B-707.......And you have kicked the tires and ready to light the fires and as you walk forward up the cargo bay you notice stenciled on each side of the cargo bay every 10 feet are the words   "STA "XXX.X" , LOAD LIMIT 4,500 LBS" ........so....... with 15 stations along the cargo bay where might you secure the crankshafts for the flight?

No Vegas Flyer.......you are not allowed to chime in here.........

Why would the Buzzard have so many loading instructions painted in big bold letters???

Hint.......the answer is not very much related to the cargo mass (weight)........

 

Fly on.........(so little cargo.....so much cargo space)

 

[rickeieio]

Cuz too much weight in one place might kink the fuselage?

Going back to the axle weight percentages, i would guess that with a tandem drive, you tolerances would be much wider for acceptable handling.  And I can tell you, too little weight on a steer axle ain't no fun in the rain.  That's why they put sliding fifth wheels on commercial trucks. 

[noteven]

Back in the day Saskatchewan's highway regulator geniussz (geni i?)  used to mandate spring thaw "road ban" axle loadings that were approx 75% of normal including on steer axles.  We used to ride part loads of slopping diesel fuel with the 5th wheel slid behind the center of the drive axles to get the steer axle weight from 12,000lbs to 9,000lbs... it made for some interesting handling on early morning frost.. 

Dollytrolley - all's I can say about your quiz before coffee is: the more to the center of mass you keep the payload on a motorsickle, the less the handling/braking changes... could it be the same with flying machines?

[Dollytrolley]

15 hours ago, noteven said:

Back in the day Saskatchewan's highway regulator geniussz (geni i?)  used to mandate spring thaw "road ban" axle loadings that were approx 75% of normal including on steer axles.  We used to ride part loads of slopping diesel fuel with the 5th wheel slid behind the center of the drive axles to get the steer axle weight from 12,000lbs to 9,000lbs... it made for some interesting handling on early morning frost.. 

Dollytrolley - all's I can say about your quiz before coffee is: the more to the center of mass you keep the payload on a motorsickle, the less the handling/braking changes... could it be the same with flying machines?

Not, pretty close....

 

Actually a lot of factors are considered in aircraft loading's but especially on large freighters considerable effort is expended to consider......."LOAD DISTRIBUTION"....... 

 

With long body aircraft if care is not exercised the loading may become concentrated in a manner that is adverse to the operation of the aircraft.

RV trailers often have poor load distribution with large percentages of mass extended on fairly long arms from the center of gravity as well as the center of ground contact (Average Axle Center) .......large mass's at long arms tend to become unstable when excited at critical frequencies and then you have the start of..........bad juju.......

 

Now large aircraft sometimes shift fuel around in flight to adjust loading's but our trailers have limited loads to shift for adjustments, the liquid tanks have some mass potential and perhaps moving a few cases of Dr. Pepper might help but for the most part RV's are somewhat limited in weight distribution.

 

Drive on........(How many cases of DR Pepper do you have on your .......back bumper)

[noteven]

Couple of versions of what Dollytrolley speaks:

British : https://www.youtube.com/watch?v=PFzrWHTG5e8

Australian: https://www.youtube.com/watch?v=_ix7ZgsWTMg