Frame clearance

[48Rob]

Are there State dictated minimum frame clearance numbers?

I've searched for Illinois, but am unable to find one.

If there are not, what is a generally accepted number?
I realize there are probably a few people who have pushed the limit and gotten away with some super low number, but I'm looking for something safe and practical.

10" frame to ground clearance seems reasonable, 8" might work, but it does start getting close...
On an 8' long teardrop, 6-8" might be fine for most road conditions, but what about a longer trailer.
At what point does the low clearance become an issue if you are going over railroad tracks, or have a steep drive?
On my current trailer, I have several things that hang down and leave only 8-9" clearance, the axle being the biggest.
We have put several thousand miles on the trailer, with some of those miles being on rough roads and even off road, with no problems except for one very low driveway into street transition where the rear scraped a little.

Again, with our current trailer, 8-9" works, but that is only a few things, what about if the entire bottom of the trailer (frame and floor) was only 8" off the ground?

I can overcome low clearance on the rear of the trailer by adding steel rollers...but they themselves add a couple inches reducing the clearance to only 6".

Any and all thoughts welcome, the goal; to get a standy that will fit under a (standard 7') garage door with 83" clearance.
(Easy if you're only 5' tall, but I need 72" interior height)
I'm using 2.5" for roof, roof framing, and ceiling, 72" interior height, 1" flooring, and 10" frame to ground clearance which ads up to 85.5 inches.
This leaves me 2.5 inches too high.
I can make my garage door trim removable, giving me 1/2"
At 2" too tall, my options (that I'm aware of) are to lower the frame two inches, or let air out of the tires...

Rob

[PaulC]

Hey Rob, not wishing to hijack this but you could always fit 10" rims when you want to put it away
Seriously though, our trailer regs(Andrew says they are the toughest in the world) do not stipulate a minimum height clearance. They do stress safe and roadworthy though and that leads to pretty broad interpretations.
Cheers
Paul

[doug hodder]

All the same stuff I went through Rob....I ended up with a drop floor on mine so I've got just under 8" clearance. ..but for in and out on the garage...I swap some smaller wheels onto it. That's what was done on the old Aristrocrat Lo-Liners. With a floor jack and an air wrench....can change them out in less than 15min. I just didn't see any way that I was going to get 6' of headroom a minimal ground clearance and riding on 14" tires all to fit out an 83" door. Doug

[wagondude]

The smaller wheel approach would be the most cost effective and simple. Otherwise, you could mount your axle with trailing arms and a panhard bar and air-bag it.

Bill

[PaulC]

WOW!! I didn't think my small wheel suggestion was actually a viable proposition

Cheers
Paul

[droid_ca]

I was talking to the mechanic when I got my winter tires put on about this and his answer was that it should be high enough that if you have a tire failure that the rim will still have it off of the ground so the trailer can be moved....hope that helps

[CarlLaFong]

Minimum clearance is, usually, the scrub line. Basically, no part of the vehicle can extend below the lowest part of the rim

[48Rob]

Paul and Doug,

Thank you.
I've seen the different sized wheels for the Aristocrats, and it is an option, but one I'd rather avoid.
I'm afraid that as soon as I make it a pain to use, it won't be...
I have a big compressor in my garage, and can deflate/inflate tires much faster than changing wheels.

What overall height did you end up with Doug?

Carl and Droid,

Thank you.
That makes perfect sense.
My rims on current trailer are 4.5" much too low I think, but a good starting point to go up from.

Bill,

Thank you.

I'll have to research your suggestion to get a better understanding of how it works, though it sounds similar to a thought I had about placing the spring hangers on the outside of the frame instead of under it.
By having the front spring eye in a channel so it could be moved from low to high, either by mechanical means, or hydraulic or air power, maybe with a pin that could be moved from top hole to bottom, allowing the axle to bottom out on the frame, giving me 3+ inches of extra clearance.

I've noted that early trailers with low ground clearance usually had a body that was upswept in the rear, presumably to offer extra clearance on dips in the road.
I believe I can do something similar as my dropped floor is set to end about 3' from the end.
The dropped floor will however be 6' wide, and nearly 12' long.
In that same line of thinking, perhaps the front should also be upswept, to avoid contact with the road...

Does anyone know of a dropped floor trailer bigger than the standard Scotty type arrangement?
I saw the caravan Andrew and a couple other people posted, but they are raised during travel.

Rob

[doug hodder]

Rob....I rechecked...my garage door is only 81. Right now, the trailer measures in at 81. I haven't tried since it was first built, but it may have settled a bit on the torsion axle now and will fit with just letting pressure out. It's got a couple of thousand miles on it now.

I did that on it's first "outing" of the garage, but the tires were down to like 5# to do it, so have been swapping the tires. I'll have to see if I can do it more easily now. I do know that it can't be hooked to the truck to do it.

I can always adjust the flexiride also, but don't really get any lower than I am now. Doug

[angib]

I think there are two quite different clearance heights - one in the middle of the trailer and another near the front or back.

In the middle, near the axle, 6" is plenty unless you want to go offroad. But at the front and back ends you need a lot more if you are going to be able to traverse dips and humps.

So I suggest you consider a design that is some inches lower in the centre than it is at the ends. Like a dropped floor, but probably more like a dropped chassis.

[48Rob]

Andrew,

Thank you for your thoughts.

My current trailer has a box (body) length of 12', plus tongue, and the level chassis rides 12" off the ground.

My planned build is a 16' box, which will ride 10" off the ground measured from the bottom of the frame to the pavement.

The floor of the trailer will be even with the bottom of the frame for most of the length of the trailer (3' behind the axle and 2-3' from the front of the trailer back will be laid on top of the frame).

The frame rails are roughly 6' wide, so the "dropped floor area will be about 6' wide x 10' long.
All of the area on the outside of the frame rails (about 1' on each side) will be on top of the frame.

By putting the main center area of the floor at the bottom of the frame rails, I gain a lot of head room without placing the floor below the main frame rails.

At 10" frame to ground clearance + 1" floor thickness + 72" interior headroom +2.5" for roof structure, I get a total of 85.5" overall.
Not a bad start as it leaves me only 2.5" too tall to clear my standard 7' garage door opening.

Anyone see any errors in my math or figuring?

I could obviously reduce my interior clearance by 2.5" and get it to clear the garage door, but as I am 6'1" tall that is the goal I'm after.

Getting the frame to 10" is accomplished by using a 4" drop axle, and the RV tires/wheels I have on hand.
I could go with lower profile tires, but I don't want a modern "hot rod" look.
I could go with a 6" drop axle, but am concerned that would be getting too close with clearances.
I have to use at least 1", and preferably 1.5" supports under the main frame rails to support the floor.
At 10" ground clearance, it seems reasonable, but at 8" clearance, adding bracing that will bring it to 6.5" seems too close to dead skunks and oppossums in the road.

I'm still drawing and re drawing the interior layout to get the most efficient use of space, and to reduce the drop floor area as much as possible.

One option would be to use a two tiered drop floor having the needed 2.5" in just a small area below the main frame rails, but thus far, it isn't a practical solution as my wife and grandchildren will be navigating the different floor levels.

I looked into trailing arm suspension with air bags, and while neat and certainly an easy way to raise/lower a frame, it seems more suited to raising a suspension for use, than lowering one for parking as the trailing arms are below the main frame rail, giving no more clearance than a standard tube axle that was allowed to touch the frame rails.

Rob

[S. Heisley]

Now, don't hold me to this but I believe that air shocks/hydraulics are used on low-riders so that they can have 'em low when they want it and legal, when they need it. If you can find a low-rider website, I'm betting they would know how close to the ground you can go and exactly what you can do. It's worth a try, anyway.

These websites might give some information or trigger an idea to help:

Low-rider Hydraulics information:
http://www.ehow.com/list_7268051_hydrau ... hicle.html

Law searches by state:
http://public.findlaw.com/traffic-ticke ... -laws.html

[legojenn]

I don't know if it helps, but my factory-manufactured motomate trailer has a clearance of about 4 inches. It's legit and legal, but I have bottomed out with my hitch and rear end of the camper.

[48Rob]

Thank you Sharon!

Good information.
I'll be busy reading for awhile...

I've found several air suspension trailers that lower for loading.
As soon as I can find a good picture or diagram of the layout I might have something useable!

Rob

[48Rob]

Thank you Jenn,

In the info Sharon gave me it stated that for Louisiana the minimum was 4", so that may be a common minimum number.

Is your entire frame only 4" off the ground, or just parts of the trailer?

Rob