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Old 05-04-2003, 07:22 AM   #1
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math wiz's: how steep a slope can I back up?

I'd like to park my trailer in the back yard, but the only way in would require me to back it up a sloped "ramp" that goes from my driveway/parking area into the yard. (I'll see if I can post a pic later). The parking area is the same level as my basement...its a "walk-out" basement. the back yard is sort of in between the level of the basement and the first floor of the house. I can drive the truck up there easily, but I'm afraid I might bottom out the trailer if I tried to push it up there...either the bumper or tail-pipe, or perhaps the hitch. I'm wondering if there's some way to calculate this, based on the rise/run of the ramp vs. the distance from the rear axle of the trailer to the bumper....something like that I know, I could just "try it and see"...but I'd hate to find out the hard way that it won't work

I'll measure and take a pic later on. the ramp is aprox. 8 feet long, and rises 3 or 4 feet.
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Old 05-04-2003, 09:04 AM   #2
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Not really an answer but have read about people backing large trailers up hills and blowing transmissions. Probably not applicable to your setup but something to consider. I think I read it in TL some years ago, this retiree had a huge 5th wheel and he blew like five trannies before his dealer caught on. He had a VERY steep driveway!! The gearing on reverse is not meant for such large loads.

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Old 05-04-2003, 09:23 AM   #3
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That is one of the advantages of 4 wheel drive. You have a low range on the transfer case, that comes in handy for such uses.
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Old 05-04-2003, 10:10 AM   #4
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yep. I use 4-wheel to get it up my driveway. (there's pics in my album of the driveway situation). doesn't seem to have to work that hard.... the problem is traction (gravel driveway). If I don't hit just the right spot, I'll get stuck w/ a wheel spinning. If I make the turn just right, it goes up easy. with the trailer parked in this area, though, there isn't room to park both cars, which is why I'd like to go "all the way" into the yard with it. Its not like I'd ruin the lawn or anything, because we don't take that many trips.
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Old 05-04-2003, 10:51 AM   #5
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Doubtful

It is not the slope in itslf that would worry me. Reverse has a low enough ratio to handle a pretty steep climb. It is the sharp transition at the bottom that would almost surely make you drag.

My driveway is about the steepness you describe with a sharp transition at the bottom and the truck takes it right up in forward or reverse without using low ratio. It is the sharp transition at the bottom that tries to dig in the rear bumper.

Fortunately, by driving the quarter mile to the end of the cul-de-sac that I live on and making a WIDE turn into the ditch to hit the drive just right, I can get up without dragging. Coming down (forward), I have to make the same wide turn and drive to the cul-de-sac so that I don't drag..
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Old 05-04-2003, 11:14 AM   #6
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Chuck, yes, there are simple ways of using applied mathematics to decide this issue, but with such a huge rise of 3 foot in 8, I'm sure you have no chance of reversing up it, if the approach road is virtually horizontal. I suspect even 1 foot would be too much. I have a degree in mathematics, but I wouldn't bother to work it out. I'd get two helpers, one to watch the back of the Airstream, and one to watch the back of the tow vehicle, and slowly back up with stop signals pre-arranged when the clearance reduces to an inch. If you really want to try the math, we will assume your approach road is horizontal. (More complex if not). You need to establish the angle between the horizontal and the line between the back of the rear tire and that part of the trailer which will just foul the steepest slope it will handle. Let's call this angle A. One way to find this (approximately) would be to have someone place a 12 foot length of 4 by 2 timber (on the flat) against the back of one one rear tire from straight behind the tire, and then you crouch down and watch as the helper lifts the timber until you can see that the timber would foul some part of the trailer, any point across the width of the trailer. You would need to adjust your eye position so that you were viewing horizontally. (I said this wasn't worth doing!). Then measure 8 feet back along the ground from the point of contact with the tire, and then measure vertically upwards to the top of the timber. Let's call this distance H. If H is less than your 3 or 4 feet, then you won't make it. I suspect H will be more like 6 inches than 3 feet. If the math interests you, the angle A is Arctangent H/8. The angle of the drive ( let's call it angle D) is Arcsine R/L, where R is the vertical rise in the drive , and L is the distance up the drive over which the rise is measured. You would need a spirit level and a plumb bob to establish the rise in height, R. Arctangent H/8 simply means "the angle whose tangent is H/8", and Arcsine R/L means "the angle whose sine is R/L". They are found on some calculators as Inv Tan and Inv sin respectively. If angle D is greater than angle A, you won't get up the drive. I wouldn't recommend this approach, but I'm sitting here recovering from 3 hours in the water, teaching my grandaughters to eskimo roll a kayak, so I had 10 minutes to collapse gladly in front of the computer. Have fun! Nick.
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Old 05-04-2003, 01:06 PM   #7
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Thanks nick. That's interesting. I was thinking something like that...making a couple of triangles; 1 with the rise/run of the ramp, and one measuring from the bottom of the trailer's bumper to the back of the rear tires. then compare the 2.

I know I can get more exact numbers by using a couple of stakes and a line-level, but I'm not that motivated today. I did take a couple of rough measurements, though. the run of this ramp area is closer to 10 feet. 3 feet is about right for the rise. check the pics I just posted to my gallery. note the "yard" stick behind the whiskey-barrel. it is 4 ft high. the top of that stone wall is pretty much level with the top of the ramp. once you hit the turf, though, it continues to slope upward, though more gently. and the driveway at the bottom of the ramp ain't flat, either. just less steep.

What I want to do is park the trailer over to the left of the shed. its a nice, flat terrace on top of the stone wall, and I was planning on running electricity out there, anyway. If you look at the pic taken at the bottom of the driveway, you can see the spot where I parked it last summer. it is on the other side of my pickup. (one false move, and its over the cliff of boulders that shore-up the driveway.). Its close enough to the house to run electricity, and near my tools, etc....but not enough room for both cars to park. its really "in the way" there. I have it parked 500 feet away at the end of the road that is my driveway right now...no way to get electricity there, and I'll never do any of the endless little projects on it that need to be done if it stays there.
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Old 05-04-2003, 01:36 PM   #8
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Chuck,
If the rear of the trailer is close to making it you might get a little extra height by lowering the trailer ball. A small change here will make quite a difference at the trailer end but the down side is the hitch might drag. If you have a equalizer hitch you might be able to go part way and then put on the bars to raise the back of the truck.
Or, as in my case, no way can I get my AS close to my house so I bought a generator to provide power.

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Old 05-04-2003, 03:52 PM   #9
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I vote for giving it a try with a spotter's help...go slow!

Would it make a difference if you went truck first? It looks like you may have enough room to maneuver at the top...but then again, pictures can be deceiving.

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Old 05-04-2003, 05:37 PM   #10
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Lightbulb Similar Driveway

chuck

Your driveway is so much like mine~! Except, yours is a more gradual slope. lol
A possible solution for you to consider would be to use a “front mounted” receiver hitch.
You could eliminate your blind spot caused by backing up, using the traditional method.
Just a thought.

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Old 05-04-2003, 07:06 PM   #11
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um.....

nobody said there was gonna be math
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Old 05-04-2003, 07:30 PM   #12
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Quote:
nobody said there was gonna be math
LOL!!

Well, that's just what I need: a front receiver, so I can watch myself run my trailer aground! LOL!

actually, I don't think it would help, because the windsheild is so close to the front bumper...all I'd see is the front window of the trailer. going backwards, and the mirrors being far away from the trailer lets you see around it more. Pretty cool idea, though. friend of mine did that on his truck, but he's only playing w/ little utility trailers that he can see over.

yep, I think the only way to find out is to try it. I measured the distance from the rear tire to the bumper, and its almost 6 feet. and the bumper is only about 16 inches or so above the ground (although, it isn't perfectly flat and level where I measured it). OTOH....the truck being so long and all, it would still be pretty far away from the ramp (and further down hill) when the back end of the trailer approaches the "ramp", it would probably angle upwards some. so who knows?.......
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Old 05-05-2003, 02:18 AM   #13
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Chuck, I've looked at your photos, and I have a similar problem that stops me getting my Airstream into my son's back yard. I plan to rent a backhoe and grade out the rise over a longer distance. It might cost $300 dollars, but, as you know, it's really frustrating to be stopped by a rise like that. Good luck. Nick.
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