Maximum Inclination

[CaptBMF]

What are the maximum and preferred angles a 40' 2004 Country Coach Allure pulling a Landgrebe TD40 Tow Dolly can traverse? I'm building a pull-though garage that has been raised from 11' to 16' to get above the 100-year flood plane. Thanks. Cap'n Blaine

[Gary RVRoamer]

Tough question. It can climb a very steep angle, but an abrupt transition is a problem. When the front wheels come over a lip onto the level, the long wheelbase lets the center drag. When transitioning from level to the upward angle, the rear end can drag. The dolly tongue also rises quickly and the back of the dolly is likely to drag. I would keep the transitions to a max of 3 degrees, but the mid-portion of the climb can be most anything. The length of the transition area is harder to guess and will depend on the ride height of the coach suspension and whether there are any dangling components under the frame rails. You will just have to look under your particular coach and make some judgement calls.

If the coach has a tag axle, you need to be concerned about the tag lifting the drive wheels away from the pavement on a transition as well. Most 40 footers don't have a tag, but a few do so thought I should mention it.

[hohenwald48]

It can be worked out with a tape measure and geometry but I can't for the life of me figure out how to tell you to do it. Drive it to Nashville and I'll help you.

I'll give it some more thought and see if I can come up with a drawing to help.

[cruzbill]

Gary's got it, its the transition, not the elevation gained. Pull thru, you say, no backing out? If so, the transition just has to clear the front of the cap (bumper), so its the distance from the front axle centerline to the front bumper, and the height of the front bumper. If you have to back that dolly out of there, then no guesses.

[hohenwald48]

OK, see if this makes sense.

Measure the distance from the center of the front axle to the center of the rear axle. Call that "X"

Measure half "X" or midway from the front axle to the rear axle. Call that "A".

Now measure from that mid point up to the body or frame at that point to the ground while sitting on a level surface. Call that "B"

Now you have a triangle where "A" and "B" define two sides. The unknown side is "C".

Now solve for "C" using the old "A" squared plus "B" squared equals "C" squared. The "A" "B" angle of the triangle is 90 degrees. You can use trig functions to calculate the other angles of the triangle.

As someone has already pointed out, you will need to figure the same angles based on front axle to front of motorhome and rear axle to rear of motorhome distances too. The dolly really complicates the calculations but they can still be done using basic geometry and trigonometry formulas.

Of course this is all theoretical and based on a perfect world.

[Scarab0088]

It is not the grade or incline of the driveway that is important to engineer...it's the angle at the street (approach and departure angles) and "break-over angle" (crest angle) at the top...solve for the angles in this diagram:



The typical DP will bottom-out the tail (trailer hitch) entering or exiting a steep drive (departure angle)...then hang between the axles at the top.


Best luck

[CaptBMF]

Gentlemen; Good techical advice and formulas to work from. Thanks. Cap'n Blaine

[sbleiweiss]

One quick addition. We had a similar problem and just slowly tried it while an RVing friend watched from the outside. Of course our issue was already built so you may not be able to do this. But my point is the steps were the thing that came closest to hitting pavement. Take that height into account. We cleared by the way. Good luck.