Bumper-mounted trailer hitch bracket for Jeep Wrangler TJ

On Wed, 25 Jan 2006 23:56:17 GMT, with neither quill nor qualm, "Grumman-581" quickly quoth:

That's what happened to the Toyota station wagon that hit my F-150 dock bumper. It shortened the Toy by ONE FOOT and it gave my right rear fender a 1/2" deep 2.5" diameter ding as well as scratching the dock bumper paint. Luckily, I had the rear slider open and it kept my head from going through the back glass. Both pieces of glass bowed and acted as a spring to limit my whiplash vs. killing me. I'm just glad I was still doing 35mph when she hit me at 65. How she missed seeing 30 cars with their brake lights on (+ my full-sized pickup) I'll never know.

MASS, not crumple zone, is the winner in a vehicular accident. Trucks usually win over cars and smaller trees. Y'all can keep your Geo Metros and other crumple-zone tin cans.

--- Annoy a politician: Be trustworthy, faithful, and honest! ---

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Richard, in your article you make a point of saying "I used Grade 5 bolts since ungraded hardware is not suitable for load-bearing applications. " You do realize that the bumper you are attaching to is only 3/32" thick and is not rated for load bearing applications....... This is somewhat of a contradiction don't you think?

Tom

I'll bet he also didn't think about what happens if he front ends someone while pulling the trailer. He will have a thousand pound plus spear running right through that sheet metal bumper, right through the door, seat and anything/body else in it's way...

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: N>

Stephen, I have to agree. I made a front brushguard for my Jeep and a week after getting it on I got rear-ended and launched 4 feet forward and up under the back of a flat bed truck. Only thing that it did to the Jeep was scratch off some powder-coating on brushguard. The guy that hit me had to have a new grill and hood. Had it not been for my guard I would have had to have all that too. Here is a pic of guard.

Tom

The bumper is suitable for load-bearing, for a suitable load.

One problem I understand with ungraded bolts sized about 1/2 inch or smaller is that hand-tightening torque can stress the shaft close to the working limit, leaving not enough strength for the applied load. This is not an issue for the bumper itself.

Between the coupler and the vehicle interior is 40 square inches of 3/8 steel, and a beefy frame cross-member in front of that.

In such a collision, I would expect the rubber boat is going to be ripped off its hold-down straps, launch forward, hit the back of the car, bounce off and pitch-pole over the car.

Of course, if you want to start postulating arbitrarily forceful collisions, then some scenario is going to have a trailer axle or something through my eye socket.

Please, I'm just trying to get my toy boat and waverunner trailer 6 miles down to the beach.

The last time I hauled a rubber boat it was atop my WJ.... How dangerous was that?

Can I throw in my 10 cents worth here?. I am NOT an engineer - I saw the drawing, thought, MM, thats looks pretty cool. Subsequent discussion here tells me it is not. How would I know otherwise ? - I dont have the depth of engineering knowledge to see what looks like a reasonable trailer hitch and know that I should be careful? - could I humbly suggest that a sticker saying "max towing weight 1,000lbs" be put on the thing? - yes, Richard, you designed and built it for a specific application, you know what NOT to do - but what about the next owner? - they wont know.....

This is one of the resons that there are standards - not only to (try to) protect the stupid, but also the rest of us who dont have a high degree of knowledge and skill in fields other than their own. And, in this case, I readily admit to being one of those ignorant people. My field is electronics, not mechanical or automotive engineering.

But it was a nice posting - know a bit more about the subject now, so thanks folks - glad groups like this are around....

Andrew VK3BFA.

---snippy---

I like this one.

Earle

Good one Earle.

Tom

Richard, If the bumper were suitable for load-bearing then why does Jeep not sell this simple little option. I have to say that I am impressed with your web page, you have lots of nice stuff on there and seem to be a guy that is somewhat intelligent, but this is not one of your better ideas. There is a reason you can not buy a Jeep with a bumper hitch option on it. I would think that the Jeep engineers know what they are doing, and if you want towing on a Jeep it comes with a separate (mopar) draw hitch attached directly to the frame rails and not the cross member. These components were not designed for this application plain and simple....... I am no engineer but I do work with metal every day, (build poultry processing equipment) and I have seen what can happen to 3/32" steel when a load is applied, trust me it does not take much to rip this stuff in half. I wish you luck with it and I hope that no one ever gets hurt from what I think is a bad idea. If you would like I would be glad to sell you my 1 1/4" receiver hitch (mopar

1000lbs on 4 cylinder, 2000lbs on 6 with a max tongue of 200lbs) after I have finished my bumper that I am currently in the process of making....... I would let you have it for a very reasonable price if it means that you would take that thing off and never let it see the light of day again.......

Tom

If it ever came down to a situation where someone would read it, and heed it, then I might do something like that. For my personal use, why bother. (On the other hand, I've never had much use for that steel punch stamping kit, maybe I'll stamp it on there for that Canadian trip someday, heh heh.)

This whole culture of Jeep hitches has me baffled. People insist on putting class III hitches on a short-wheelbase soft-top vehicle that dubiously purports even a minimal 2000 lb capacity. The guys who also have the jacked-up suspensions, cheating death with their unstable aftermarket mods, are the extreme version of this.

THere is a kind of "impedance matching" optimization to this type of design, and I believe I've approximated it for the intended application.

Not probative. I recall they didn't sell any kind of hitch option for a long time; it was all unendorsed aftermarket stuff.

Last I checked, U-Haul won't even rent you a trailer for a Jeep, no matter what hitch you have.

Trailering on a Jeep is a problematic compromise (when it is not a religious absolute in some minds).

Richard, "Not probative." oh please. I really hope your arrogance does not get someone hurt.

Tom

Bull crap.

You are attaching a trailer to sheet metal that 'I' am capable of bending back into shape by hand.

Overbuilding an attachment point is a safety thing. Off road stresses can be amazingly high. Putting an attachment point on sheet metal is almost criminal. Well, it 'is' criminal up here in Canada to have an under rated trailer hitch.

The rental places won't rent to soft top vehicles. This is because of a serious CO safety issue when the exhaust vortexes between the back of the Jeep and the trailer.

I know there is no talking sense to you. I just hope you don't go out and kill someone.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: Non members can still view! Jan/06 (More Off Road album links at bottom of the view page)

One thing that I noticed that I would at least re-engineer a bit was the fact that it appears that his hitch plate does not have a backing plate behind the thin metal of the Jeep bumper... I would think that he should at least have a backing plate as large as the hitch plate inside the bumper to distribute the load across a greater area... An even better idea might be to have this backing plate large enough to traverse the full with of the bumper... Once you're at that point, maybe you should even consider having this 'backing plate' tie in to the frame of the vehicle... Of course, by this point, it would have probably been easier to just build a real bumper from scratch...

Not a good analogy... These are the same engineers who designed the problematic manifold that cracks and the motor mount bolts that haved sheered off on my XJ multiple times?

Who has the video of a rear bumper being ripped off while attempting to pull another vehicle out of the snow alongside the road?

I saw a link to it sometime in the last 6 months or so...

Billy, I think you are referring to this video.

Tom