Rear Aluminum bumper Failure Bigfoot

[Bob Miller]

Originally Posted by David Tilston

Darral,

If I got a pickup, where would I put my five kids?

I think that Darral must have a lot of money and is offering to buy you one of those new FORD F-1650 6 door pick-ups. How nice.... LOL

[Darral T.]

No....Darral forgets what it's liking having to think about the kids since his is grown and gone.

Originally Posted by Bob Miller

I think that Darral must have a lot of money and is offering to buy you one of those new FORD F-1650 6 door pick-ups. How nice.... LOL

[David Tilston]

Originally Posted by Darral T.

Where do you put them in a TRILLIUM trailer???

The trailer sleeps four kids, the van sleeps my wife and I, and the littlest one. Actually the oldest may not come on the next trip, so my wife and I will have the van to ourselves.

Also, it should be noted that the van also cuts the wind for the trailer, making it more stable, and less buggy.

[sokhapkin]

Originally Posted by David Tilston

Also, it should be noted that the van also cuts the wind for the trailer, making it more stable, and less buggy.

Hmm... This could explain why my Scamp 16 tends to sway when towed with Mercury Grand Marquis, but never swayed when towed with a short bed F150.

[Darral T.]

Ohhh....so yer pulling an "apartment" So that means FIVE bicycles (7 if you and wifey rides) on the front of the van?????

Ahhh...I'm just messing with you now. Enjoy life with those 5 kids my friend. I found out with mine...life is VERY short...

Originally Posted by David Tilston

The trailer sleeps four kids, the van sleeps my wife and I, and the littlest one. Actually the oldest may not come on the next trip, so my wife and I will have the van to ourselves.

Also, it should be noted that the van also cuts the wind for the trailer, making it more stable, and less buggy.

[honda03842]

Originally Posted by sokhapkin

Hmm... This could explain why my Scamp 16 tends to sway when towed with Mercury Grand Marquis, but never swayed when towed with a short bed F150.

Our Odyssey is almost identical to the Scamp in size and very similar in shape. The Odyssey is only about an inch narrower than the Scamp and just about as long.

Our Scamp 16 has yet to show any tendency to sway. We do typically tow with an anti-sway bar but we have towed the Scamp 2000 miles with our CRV without an anti-sway bar and it tracked beautifully.

Could it be a spongy suspension on the Marquis?

[David Tilston]

The company I work for sells a vortex flow meter. It works by presenting a bluff body, (flat faced bar) to the flow. This causes vortices to shed on alternating sides of the bluff body. This is called a Kármán vortex street:
https://en.wikipedia.org/wiki/K%C3%A..._vortex_street
This is also what causes a flag to flap in the wind. The force involved is enough that a pizo crystal, inside the bar, can pick up the torque caused by these vortices, even when measuring the flow of a gas.

It is my belief that the same thing happens with a trailer. The large flat faced trailers get it worse then our rounded eggs, but it still happens. Since my van cuts the wind, the most stable place for the trailer is directly behind the van. When it sways out of line with van, the force of the wind will push it back into line. With a lower sedan, the face of the trailer is subjected to highway speed wind. The trailer is subjected to this torque and it may start sway. An SUV, or van covers a larger portion of the hight of the trailer, so it reduces this effect.

I am sure that there is much more to this then just vortex shedding, but I think that taking it out of the equation helps.

BTW, we carry three bikes on the back of the trailer, and the two smaller ones in the trailer. Nothing on the front of the van. I thought it was a good idea, but I don't do it.

[sokhapkin]

Originally Posted by honda03842

Could it be a spongy suspension on the Marquis?

Could be. But I suspect the problem is not in suspension, but in long overhang, about 65" from rear axle to the hitch ball.

[honda03842]

65" is long. On our CRV I was able to reduce that distance a couple of inches by pushing the ball mount further into its receiver. Small things that result improvement. Moving closer to the axle improves limited tongue weight ratings.

[Nedchiu]

I am having a 4x4 square steel 1/8" thick bumper installed. I will keep an eye on the extra weight added to the back by shifting weight to the tongue.

A friend of mine has the exact same trailer but two years newer. His trailer has a 4x4 steel bumper and not an aluminum one.

[Bob Miller]

If your BigFoot is big enough that might work out for you.


BUT... When I added a 38 lb set of levelers to the back of my Hunter, and offset it with a 42 lb battery on the tongue, it just plain didn't work out. I had lots more sway due to what's called the "Pendulum Effect" of adding weight well behind the axle. After pulling it 1200 miles I had to take it off and scrap the levelers.


Your 1/8" x 4" x 78" (?) sq steel tube will weigh a bit over 44 lbs. keep that in mind if it feels a little squirrely.

[floyd]

Originally Posted by Bob Miller

If your BigFoot is big enough that might work out for you.


BUT... When I added a 38 lb set of levelers to the back of my Hunter, and offset it with a 42 lb battery on the tongue, it just plain didn't work out. I had lots more sway due to what's called the "Pendulum Effect" of adding weight well behind the axle. After pulling it 1200 miles I had to take it off and scrap the levelers.


Your 4" x 78" (?) sq steel tube will weigh a bit over 44 lbs. keep that in mind if it feels a little squirrely.

The tubing used for Square tube RV bumpers is light gauge material thin enough to accept those rubber plug ends. As I said earlier mine weighed eleven pounds. It is only 4ft long though, as it was cut to fit the straight section of the Scamp bumper, leaving the angled section to protect the ends.

[Bob Miller]

The earlier post mentioned that they were using 1/8" wall x 4" square tubing. That comes out to a little over the mentioned 44 lbs. based on 5.1 lbs. sq.ft. for 1/8th plate. AKA: heavy, heavy & heavy....

[floyd]

Originally Posted by Bob Miller

The earlier post mentioned that they were using 1/8" wall x 4" square tubing. That comes out to a little over the mentioned 44 lbs. based on 5.1 lbs. sq.ft. for 1/8th plate. AKA: heavy, heavy & heavy....

Your calculation is close but that is not the normal thickness for RV bumpers and standard RV end plugs won't fit.

[Tim D.]

While I would not recommend the practice to others, I have been hauling two bikes on a spare-mounted rack on a Bigfoot 17' for 70k miles. This has not been without incident.

Note that my Bigfoot has the springs sitting atop the axle. This significantly raises the body, giving more ground clearance. I would not consider a spare-mount bike rack otherwise.

Before driving with the bikes I had the spare tire mount [not the rack] reinforced. On either side of the mount, at the top, tubing was welded at a 45 degree angle down to the steel bumper. Steel strap was placed from the top of the mount forward and down around the bumper, then welded in place. This can be seen in one of the attached photos. I thought this would be enough. It was not.

The spare tire mount has a 3" or 4" long steel crosspiece with a hole in it. The hole is to accept the bolt that attaches the wheel. That piece broke after several months on the road, including rough and unpaved roads. The bikes and spare seemed secure, just tilted down against the bumper. I had a new heavier piece welded in place. As part of my walk-around I monitor the distance between the bottom of the spare and the bumper.

The big scare came a couple of years later. During a walk around, my practice at every stop, I noticed the bikes and spare were tilted back, away from the body. The welds holding the bumper to the frame were fine. The bumber metal itself had torn on both sides. I had triangles of steel plate welded at the bumper-frame interfaces. That was about four years ago. I keep a close eye on that. No problem so far.

I use the spare-mounted rack to save weight. I admit that I would like to get a receiver hitch and tray mounts. This may need require a custom s-shaped mount tube in order to get the trays up high enough that they will not bottom on steep driveways and to extend far back enough to clear the spare.