Receiver hitch

[gogmorgo]

5/16" is bigger than 1/4", no?

I was in the middle of writing a post this morning with a link to some stuff that may (or may not) be helpful, but got called in to work early. I'll finish it up when I get home.

[Jeep Driver]

By the time it takes you to jackass around with it.........just make up your own.

BTW, mine is made up with 3/8 plate and 3" 1/4 wall tube.

You find nothing on the market that strong.

 

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[1990 Comanche]

Oops, you are correct. I should have written 3/16"

[gogmorgo]

http://www.filedropper.com/sideplateforexpedition2ndrevision

 

Here's a Solidworks drawing file I put together a few years back. I'd intended to use it with a hitch I pulled off a Ford Expedition, but I never got around to finishing it. I didn't even get all that far into mockup, either. I think the bolt spacing is accurate for using all four of the bumper bracket bolts on the side of the frame, however I'm not positive on that. I went through a couple iterations with the bolt spacing, and I for some reason I have an inkling suspicion the final version somehow didn't make it to the drive where I saved them, so definitely check that before your order is carved in steel.

Another thing about that particular end plate is that the factory hitch's crossbar mounts behind the bumper, and the receiver drops below the bar and bumper, so only the receiver tube is visible. The Expedition's hitch, on the other hand, has the receiver tube mounted at the same height as the crossbar, so the crossbar also ends up sitting below the bumper. Some people may not want that, as it leaves something else hanging under the bumper, although I was thinking it would be good to have a little extra there in case the bumper gets slammed against the ground, and if I wanted to I could always add recovery shackles to it and still keep the factory bumper.

Unfortunately, I don't have the resources at hand to do much with that file. If you can't open a SolidWorks 2013 file, you may be out of luck.

 

 

For reference, (although you've likely already seen it) this is a pdf of the bracket from earlier in this thread, with three holes plus one for the shortbed shackle mount bolt. I did some quick FEA on the bracket, and IIRC I concluded that the shackle bolt provided better reinforcement to the bracket than adding a hole for the forward-most bumper bracket bolt. But any CAD or CNC guy worth their salt should be able to make something with the PDF drawing. We have a laser cutter at my university that actually "prints" PDF files, although you need to set them up carefully so that the line thicknesses are correct to the laser's beam width.

https://docs.google.com/file/d/0BzTWL2t-sbKdNkRCQ056QUJZMVk/edit?pli=1

 

The difference between the rear section of the frame where the bumper and hitch bolts up is that the short bed models have the rear spring shackle mount right under the bolts. The brackets have a bulge to accommodate the mount, and the same brackets were used in both long and short beds. (At least in later years). The hitch used the same end plates for both bed lengths as well, but with spacers on the bolts so that the flat plate didn't need to accommodate the bulge.

 

However, there's a chance the '86 model year brackets could be oddballs. There was no short bed for the Comanche's first year, and it can't be guaranteed that AMC initially designed the bumper brackets with the short beds in mind. In the event that they had to change the brackets, it's also possible that they changed the brackets but without changing the part number (or the part numbers got fudged a bit when ChryCo took over). I've never seen factory bumper brackets on an '86, though, so that's all conjecture. If my theory is correct, it also wouldn't surprise me if even after the redesign, some long beds got the early version of the brackets while they used up any remaining inventory, so there's a chance some '87 long beds may have oddball brackets as well.

 

 

Mostly that last paragraph is a possible explanation as to why your hitch doesn't fit properly. You could always notch the hitch's brackets to fit around the shackle mounts (I'm assuming that's the problem) or else put spacers between the bolts to clear everything properly. You'd also need spacers where the brackets bolt to your hitch's crossbar, and would either have to adjust the holes in the brackets for the bottom of the frame or just leave the bottom bolts out. I'll add that I really have no idea what your hitch brackets look like, only a foggy picture in my head based on your description, so don't immediately dismiss me as an idiot (although I won't deny that it may be the case). Also, the extra half-inch you're seeing in the short bed bracket is likely because of the presence of the spacers, which add a quarter-inch on both sides.

 

 

After taking this all in (or not... it's a lot of words), keep in mind that Jeep Driver is correct. The process for a hitch shop to build you a custom hitch is going to be something like:
1. Look for place to mount brackets to vehicle.
2. Position receiver in desired location
3. Attach the receiver to a cross bar that's wide enough to reach the mounting points.
4. Take a steel plate (which will be 3/16" or 1/4", depending on needs) and cut, drill, bend, weld, etc so it joins the crossbar to the mounting brackets.

Many shops may drill extra holes in the frame instead of using existing holes. There was one custom job a member on here posted up that only bolted to the bottom of the frame. There are 1000 ways to do it, and just about all of them will work. It's also true that in the amount of time I've put in thinking about this, I could have easily reproduced the factory hitch as it's represented in this thread. My craftsmanship is nowhere near the level of Jeep Driver's, which is in part why I never got around to finishing my hitch, as I'm not confident what I build won't fail in a catastrophic way, even though I know the design is sound. It also wouldn't surprise me if a dollar amount were put on the time I've spent thinking about the hitch, it would double or triple what a shop would charge for a custom job.

[terrawombat]

@gogMorgo - A note on Solidworks files: If a Solidworks drawing file references a Solidworks part you will need BOTH files in order to view it.  I downloaded your Solidworks drawing file and opened it, but without the part file all you see is the drawing template and a view of where the part should be, but it's essentially a blank drawing.

 

@1990 Comanche - I will follow up with you via PM regarding the message you sent to me last week.

[yellaheep]

I will now humbly fall on my sword and admit that I was wrong. Today I did some measuring and comparing the short and long bed bumper brackets, and the two hitches I have.

 

Gogomorgo is correct in that the '86 brackets are indeed different than the '87+ short bed brackets. The '86 brackets are flat where the later ones have a bulge to accommodate the short bed shackle mount. My '88 long bed has the same '86 flat brackets on it, but are dimensionally the same as the short bed brackets on my '87 & '91.

 

So with that said, short bed brackets simply have a bulge but are otherwise the same as long bed brackets.

 

Now, as for the two hitches I have, one came off a short bed, the other a long bed. The side plates are longer on the long bed one, but today I realized this is because the cross bar sits below the stock rear bumper, where the short bed hitch sits behind the bumper, with the receiver below the bumper step.

 

It's just the difference in aftermarket hitch designs.

[krustyballer16]

I will now humbly fall on my sword and admit that I was wrong. Today I did some measuring and comparing the short and long bed bumper brackets, and the two hitches I have.

 

Gogomorgo is correct in that the '86 brackets are indeed different than the '87+ short bed brackets. The '86 brackets are flat where the later ones have a bulge to accommodate the short bed shackle mount. My '88 long bed has the same '86 flat brackets on it, but are dimensionally the same as the short bed brackets on my '87 & '91.

 

So with that said, short bed brackets simply have a bulge but are otherwise the same as long bed brackets.

 

Now, as for the two hitches I have, one came off a short bed, the other a long bed. The side plates are longer on the long bed one, but today I realized this is because the cross bar sits below the stock rear bumper, where the short bed hitch sits behind the bumper, with the receiver below the bumper step.

 

It's just the difference in aftermarket hitch designs.

 

do you have pictures to better explain the difference in hitches. 

 

i gave the drawings from earlier in the thread to a process engineer at work to draw up and next week when my 1/4" sheet comes in, ill have some of the side plates/ brackets cut out. i did make a modified version that drops the cross support down 1/2" to clear my bumper i built because my factory hitch i have was almost touching the bumper.

 

ill also have front bumper brackets and stock mj spring perches cut out. 

[gogmorgo]

My '91 long bed's bumper brackets have the buldge for the shackle hangers. My hitch brackets had to accomodate that, but I was just going to use 1/4" spacers.

 

@gogMorgo - A note on Solidworks files: If a Solidworks drawing file references a Solidworks part you will need BOTH files in order to view it.

Shoot. I knew that...  :doh: Haven't done any CAD since August.

The reason I didn't include the part file was because... weeeeelllll... I'm not sure I have it.

This was over a year ago, so I'm a little foggy on the details, but I was doing stuff on the computer in my FSAE team's shop, and hurriedly jumbled things onto a flash drive, which I've since misplaced. Somehow, though, I wound up with a "hitch" folder on my cabinet on the university's server. The folder has five files. The first two are a log and crw from a study, so I'm guessing it was the FEA stuff I was doing. The next file is the drawing file, called revision 2, and the other two are parts files... one's called revision 1 and the other's named as if it were the original. But here they are:

"Original" (part)
"1st revision" (part)

"2nd revision" (drawing, same as above but included to keep things together)

 

Hopefully one of the two part files is linked to the drawing...

It just occurred to me that these could have been from someone else saving everything I left open when I left the shop, in which case I have no idea what they actually might be. My student license for SolidWorks 2013 expired in December, so I'd have to go back to the unviersity to open the files to find out what they are, and that would likely involve, er, "creatively entering" the shop because the computer labs only have SW2007 ilast I checked.

[Eagle]

I will now humbly fall on my sword and admit that I was wrong.

Sword falling is not necessary. Self-immolation would suffice. ;)

[yellaheep]

Sword falling is not necessary. Self-immolation would suffice. ;)

 

 

 

...... I couldn't sit still for that long.

[krustyballer16]

left work with these last night (2 sets)

 

i used this picture, gave it to an engineer at work to draw from. fits perfectly. 

https://docs.google....ZMVk/edit?pli=1

only thing i messed up on was i didnt look at this drawing very closely. stock hitch uses 2.5" tubing and i bought 2" tubing.... so ill have to just buy more tubing....

[Megadan]

I've been interested in a solution to mount the Reese 37042 Hitch as it is currently up on Amazon for $79.95 (Plus 35 shipping), which is a bargain. 

[terrawombat]

left work with these last night (2 sets)

 

i used this picture, gave it to an engineer at work to draw from. fits perfectly. 

https://docs.google....ZMVk/edit?pli=1

only thing i messed up on was i didnt look at this drawing very closely. stock hitch uses 2.5" tubing and i bought 2" tubing.... so ill have to just buy more tubing....

Looks like someone did an excellent job on the design (hint, hint, wink wink)

[krustyballer16]

 

left work with these last night (2 sets)

 

i used this picture, gave it to an engineer at work to draw from. fits perfectly. 

https://docs.google....ZMVk/edit?pli=1

only thing i messed up on was i didnt look at this drawing very closely. stock hitch uses 2.5" tubing and i bought 2" tubing.... so ill have to just buy more tubing....

 

Looks like someone did an excellent job on the design (hint, hint, wink wink)

Yes thank you.

[ParadiseMJ]

Any interest in MARKETING these??  I would love a pair of these.  I don't have a cutter or an engineer, dammit!!

[terrawombat]

Not a problem. I was and still am a little disappointed with the fit. Its a little sloppy which is not something you really want with a hitch but when I tightened up the hole sizing I was no longer able to get it to fit on all three of my Comanches. Too big of a tolerance on the frame mounting locations between years I guess.

[krustyballer16]

Any interest in MARKETING these?? I would love a pair of these. I don't have a cutter or an engineer, dammit!!

 

I could. But I run into the hassle of not having money to buy steel and then the lasers finding time to cut them for me and all that. I'd like to do it and help everybody out and even build the whole hitch for a few extra bucks but it might be a while. I am going to go price a sheet of 1/4" and 2.5" square tubing. And I could see what the lasers could do for me. I just don't wanna cut 20 sets of them and sit on them for years....

 

 

 

 

Not a problem. I was and still am a little disappointed with the fit. Its a little sloppy which is not something you really want with a hitch but when I tightened up the hole sizing I was no longer able to get it to fit on all three of my Comanches. Too big of a tolerance on the frame mounting locations between years I guess.

I didn't actually bolt them up but they look like they're perfect. I've still gotta put the 1/4" spacer behind them to space out for the bumper bracket. I could make that hole smaller and weld it on for a perfect fit.

[87MJTIM]

 

Any interest in MARKETING these?? I would love a pair of these. I don't have a cutter or an engineer, dammit!!

 

I could. But I run into the hassle of not having money to buy steel and then the lasers finding time to cut them for me and all that. I'd like to do it and help everybody out and even build the whole hitch for a few extra bucks but it might be a while. I am going to go price a sheet of 1/4" and 2.5" square tubing. And I could see what the lasers could do for me. I just don't wanna cut 20 sets of them and sit on them for years....

 

 

 

 

Not a problem. I was and still am a little disappointed with the fit. Its a little sloppy which is not something you really want with a hitch but when I tightened up the hole sizing I was no longer able to get it to fit on all three of my Comanches. Too big of a tolerance on the frame mounting locations between years I guess.

I didn't actually bolt them up but they look like they're perfect. I've still gotta put the 1/4" spacer behind them to space out for the bumper bracket. I could make that hole smaller and weld it on for a perfect fit.

 

If you do make a few, put me down for one.

[ParadiseMJ]

 

Any interest in MARKETING these?? I would love a pair of these. I don't have a cutter or an engineer, dammit!!

 

I could. But I run into the hassle of not having money to buy steel and then the lasers finding time to cut them for me and all that. I'd like to do it and help everybody out and even build the whole hitch for a few extra bucks but it might be a while. I am going to go price a sheet of 1/4" and 2.5" square tubing. And I could see what the lasers could do for me. I just don't wanna cut 20 sets of them and sit on them for years.....

 

 

 

I completely understand that.  Which is why the commercial hitch makers don't make hitches anymore for the MJ.  The only hitches I've found have been for LWB's or integrated into home brew bumpers.  I've even found one made out of plate and re-bar, scary.  I find myself leery to tow anything more than a small trailer to the dump with my bumper mounted hitch ball. 

 

Like said, and thought, in all these 13 pages...I'm in the market for one of these sets.  I can weld up the rest of it myself with tubing and a receiver etc.  Thanks for doing the legwork by you and terrawombat for the design.

[krustyballer16]

What's the best way,if I do this, to go about making a page or a list or having people contact Me so I can figure out how many would be interested? If possible I'd like to make it a pay half before and half upon receiving them. That way I'm covered a little

[Incommando]

What's the best way,if I do this, to go about making a page or a list or having people contact Me so I can figure out how many would be interested? If possible I'd like to make it a pay half before and half upon receiving them. That way I'm covered a little

I think requiring such a deposit up front is the only way to protect yourself.

[ParadiseMJ]

I'd gladly put up a 50% deposit.  Pretty sure others would too. Nobody wants to have you getting stuck with the cost...or unwanted inventory

[ggcnash]

Count me in on a set too

[shelbyluvv]

Are these for a long or short bed? Or doesn't it matter?

[krustyballer16]

Are these for a long or short bed? Or doesn't it matter?

Doesn't matter. And I can, and probably will, make them without the 4th hole that the spring bolt runs through.

 

And I'll probably have the 3- 1/4" spacers per side lasered out too and weld em on.