Post by Rain Dancer on Apr 4, 2018 16:57:42 GMT -8
So I am thinking I want to have a receiver welded onto the bumper of my 1966 Compact Shasta. I have a bike rack that works with a receiver. My friends have voiced concern over the bumper's ability to take this on. I find it hard to believe because it's pretty solid. I am also hearing that it may cause some sway with the added weight on the back. I am thinking the rack weighs about 30# plus bike 30# and receiver maybe 5#?? My concern is the added weight for towing. My capacity is 2000# and the last weigh in of my trailer was 1500#
Like nccamper said, your best bet is a rack on the front of the tow vehicle. It's not just the weight, it's the leverage- hanging that weight that far behind the wheels is likely to significantly upset your tongue weight, which is a nice way to end up upside down. I'd avoid it unless you're in need of some serious excitement.
OK, not expert but I have towed a lot of flat bed trailers which isn't much different and I can not image 100 bs (you should be well under that) making a hill of beans of difference unless you are just on the ragged edge of tongue weight which is doubtful. Uness someone moved the axle or you are carrying a lot of stuff behind the axle it shouldn't make any difference. A spare tire mounted on the back would be close to that and I have seen a few added on. I am betting you will never notice any difference.
As for strength I can't comment without seeing what you have. But if you can stand on your bumper, jump up and down and it doesn't flex I would think it would fine. People tend to be overly cautious but again, cant say without seeing it.
100lbs isn't much weight, but that's not the point.
You need to maintain a minimum of 10% tongue weight. Odds are excellent that the distance from your proposed bike rack to the axle of your trailer is at least as long (and possibly longer) than the distance between that axle and your hitch. That means that, best case scenario, you've dropped your tongue weight by 100lbs, and possibly even more, almost certainly dropping you below the safe margin. That's what will put you upside down in the ditch.
Your axle is the fulcrum, and the distance from the additional weight to the fulcrum determines how much leverage is being applied to multiply that force. That 100lbs placed in the middle of the trailer would have no effect on your tongue weight, a foot or two away some slight effect, and twice as far as the distance to your hitch would reduce your tongue weight by 200lbs and kill you.
.....twice as far as the distance to your hitch would reduce your tongue weight by 200lbs and kill you.
100% agree with your math.
But have you ever seen a trailer with the axle forward of the centerline of the trailer frame? For 100 lbs to reduce the tongue weight by 200 lbs the axle is going to have to be forward of the centerline of the frame, actually forward of the center of balance if you want to be precise. So while possible it is totally unrealistic in a properly design camper. Axles are always behind the center line so leverage is working to your favor.
PS Rain Dancer, it would be really easy to put a scale under the tongue and measure the tongue weight. Then have someone stand on the bumper and see how much difference it weighs then. Then you know for sure but I still say it isn't going to be enough to even know they are there.
200lbs is hyperbole to demonstrate the impact of leverage.
Here's a real example- my '57 Cardinal is 16' (really 15 1/2), about 186" from ball to tail. It weighs 2000lbs with 200lb tongue weight, right where it needs to be. Ball to axle is 95", figure the bike rack would sit about a foot behind the tail, that puts it at 105" from the axle, giving it almost exactly a 10% mechanical advantage.
That 100lbs of bike and rack installed on my trailer would reduce my tongue weight to 90lbs, and I'd be upside down in a ditch in very short order. Probably on fire. You can get away with rear racks on very heavy trailers, but it's mucho bad news for light vintage stuff.
An example of the effect of weight being shifted to the rear: I once forgot to put the jacks under the rear. As soon as I shifted to the back the entire camper tilted and the hitch (not hooked up to the truck) lifted off the ground. It was like a see-saw. "...I'd be upside down in a ditch in very short order. Probably on fire. "
I disagree about the driver being upside down. The camper would be upside down and you'd be in handcuffs in the back of the police car.
Last Edit: Apr 5, 2018 11:46:45 GMT -8 by nccamper
Rain Dancer, I was looking for and found a good diagram of how you could measure tongue weight. You could add weight to the rear bumper and see how much difference it makes and know for sure what you are dealing with rather than just guessing.
The thing that a few of you are missing is you are not talking about at utility trailer you are talking about a camper. They were designed to put the least weight on the hitch as possible and still tow safely. If you wish to devote the time to reading old post on this site you will discover that many people have gotten into trouble by adding things behind the trailer. This can be done BUT you should weigh the trailer completely loaded including bikes, then weigh the tongue to make certain you have 10% of your total weight on the hitch if you want to tow safely.