Thanks for a professional explanation!
Soni, my comment above was not intended to be an attack or you or to be negative about your rig. I usually keep my opinions about people's modifications on this site to myself, unless safety is involved. My job involves moving superloads 250,000 lbs+ all over the US, so bear with me. For example, when you were transporting the locomotive, the trailer and load weighed 103,000 lbs, about 40% of which rests on the 30,000 lb truck. When the load is placed behind the centerline of the bogie, the effect is the bogie acts as a fulcrum and unloads the front axle. The objective of moving heavy loads to to have each axle carry as much of the gross weight as possible, and to maintain ample weight on the steer axle to maintain control. My rough calculations show considerably under 10,000lbs on the steer axle of the loaded combination. Any State DOT will shut this down in a second. In your pics, you can see how the front of the truck is raised. Again, I am not trying to be negative, just to advise others that this is suboptimal truck design if you intend to move heavy trailers.
Well no worries.....I did not feel attacked by your comments....Lol
I just think that somtime we all are a little fast in critisizing when there are actually (contrary to popular believe) still a few safety minded guys out there that do think before they do things that could endanger others.
I to have many years in the heavy hauling and oversize load buisness and while I totally agree with you on the theorie of your explanation I would like to point out that my fifth wheel is movable, there is ample clearance to move it forward and it was actually moved to that spot on purpose.
My M920 tractor truck after my modifications has a empty steer axle weight of 17,130lbs with both tanks full.
The rating on this axle is 18,000lbs and as you know, thats all i can get a DOT permit for.
Now since im not the kind of guy that trust mechanical things to run at the limmit and we are talking steer axle here I made the decision to move the fifth wheel just slightly behind the CL of the boggie pivot.
With the load in question (the Locomotive in the pic) the truck still had 15,078lbs on the steer axle! I just looked at the scale ticket again.
Even with the Loco moved as far forward on the M747 trailer we could only get 35,419lbs on the boggie tires unless we overloaded the rear two axles on the lowboy. ( they have adjustable air ride suspension)
Also I do have to admit that in the pic you used as an example, the truck's rear boggie does look overloaded and the steer axle does look to light.
This is an optical illusion thought, due to the fact that the rear fenders slope to the rear for added clearance and the front fender is mounted with alot more clearance over the tires then the rear ones.
So if you still feel that I need to change the setup or that I'm overlooking a potential danger, I certainly value your professional opinion. It's never to late to learn somthing new! LOL
Thanks Soni
PS: The M920A1's curb weight is now 35,110lbs and in the case of the Loco load; only about 30% of the loaded trailer was sitting on the truck.
lol