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Old 01-17-2015, 04:26 PM   #1
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Building a trailer hitch

I was thinking of building a trailer hitch for my bus. The trailer hitches that are out there either do not meet my weight requirements or cost waaaay to much.
I am looking for something that can tow between 7500 and 8000 lbs.
Here is my design,
(See picture for design)

The hitch will offer no drop, so a long drop ball mout will be needed.
I will need about 12 inches of drop for my utility trailer. It is rated for only 2000 lbs so I figure one of the $30 adjustable class 3 ones off amazon will work fine for that. For heavy dutyer loads curt offers a class 4 8 inch drop rated for 10000 lbs. witch will far exceed my requirments.


I know that people do not like using long drop hitches but if I'm not going to be even close to maxing one out I should be fine?

Thanks!
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Old 01-17-2015, 06:44 PM   #2
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Attaching a hitch reciever to the rear of a conventional school bus is a pretty straight forward and simple procedure.

Just make sure you have it bolted in with grade 8 bolts and nuts.

Also make sure there is no room for wiggle.

Your design has some problems.

First, you need to be bolting through the frame rail and not through the flange.

In other words you need to build a square frame that fits inside the frame rails to attach to the insides of the frame rails. Square tube with flat plate welded on the ends make for a very strong hitch frame.

Second, you need to make the receiver stick out at least flush with the bottom of the bumper. It is best if the stinger of the hitch isn't any longer than necessary. The longer the stinger the more leverage the trailer will have when and if it ever starts to try and "wag the dog".

Using a drop hitch isn't a bad thing as long as it is used within the limits certified by the manufacturer.
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Old 01-17-2015, 11:54 PM   #3
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Quote:
Originally Posted by cowlitzcoach View Post
Your design has some problems.

First, you need to be bolting through the frame rail and not through the flange.

In other words you need to build a square frame that fits inside the frame rails to attach to the insides of the frame rails. Square tube with flat plate welded on the ends make for a very strong hitch frame.

Second, you need to make the receiver stick out at least flush with the bottom of the bumper. It is best if the stinger of the hitch isn't any longer than necessary. The longer the stinger the more leverage the trailer will have when and if it ever starts to try and "wag the dog".
Ok,
Why can I not bolt to the bottom of the busses C channel frame? This is how the commercially produced ones attach. All of the hitches I have scene attach in this way and one of them was rated up to 16000 lbs.

The reason I want to stick to bolting to the bottom is to get the hitch as low as possible. Bolting up between the bus frame raises it al least 2.5 inches.
What is the "stringer"? Is that the bit of the receiver tube that extends past the rear most support, or is that the entire length of the receiver tube?

Thanks again, I think I understand where you are coming from but I want to hear your reasoning.
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Old 01-18-2015, 01:42 AM   #4
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The flange is integral to the strength of the steel beam, if you compromise it with a hole, you are greatly diminishing the integrity of the member. At least this is what I was told my an airplane mechanic who helped me install a fuel tank in one of my buses. I later noticed that there was indeed a stamped message on the steel that clearly said "DO NOT DRILL THROUGH FLANGE" on the frame!! This was an 87 Carpenter.

If you weld your C channel to a plate on each end, that plate could be used to not only give you a surface to bolt to the side of the frame, but also as a way to drop it down a bit, if it is sufficiently thick enough.
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Old 01-18-2015, 09:06 AM   #5
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pulling wt while towing is not an issue, tounge wt is, towing 4 down I can do with my setup, tounge wt not so much, I prefer enough tounge wt to control sway...you might be over thinking this

you towing with a trailer or 4 down?

What is frame width?

f550 up may work, have seen a few that do
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Old 01-18-2015, 09:28 AM   #6
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Hank, looks good. Using the flange avoids creating a shear effect which I like to avoid. I also use a WD hitch to reduce tongue weight.
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Old 01-18-2015, 09:57 AM   #7
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2" square receiver tube from Northern Tool In Asheville NC. Later David added bolts. Had to use threaded links to get the safety chains in the holes because it was too close to the bumper. Bus tows my 5500Lb Jeep Grand Cherokee. Have to use a dropped ball too (4" I think).







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Old 01-18-2015, 10:50 AM   #8
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Welding or drilling through the flange of a frame rail compromises the structural integrity of the frame rail.

You can add drop into the design of the hitch, it doesn't have to nestle up inside the frame rails. You just don't want so much drop that you drag going in and out of curb cuts.

The stinger is the square shank that goes into the receiver onto which the hitch ball is bolted.
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Old 01-18-2015, 12:39 PM   #9
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Thank you all for the great advice!
I will have about 700 lbs of tung weight for those who care.
I had no idea how much 8 half inch bolts could compromise the structural integrity of a massive piece of metal, I had just assumed bolting from the bottom was the best was as that's how store bought ones attach.
I will have do really think how I'm going to do this now. My welding skills are not up to the task, one of my friends who welds as part of his business was going to build this for me so I didn't want to make this too complicated.

Would the rear bumper by chance be up to the snuff to act as part of my hitch?

I am really grateful that I asked here first, it appears that I may have just saved my self some really big problems.

Who knows, maybe I'll sue Kurt over their design (pictured) of hitch for cab and chassis trucks. I'll be able to afford I nice hitch then! (TeHe no I won't sue them!)

Btw... That hitch is rated for 15000 lbs, it's also why I figured I could attach to the bottom of the frame.
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Old 01-18-2015, 01:56 PM   #10
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Hitch

The bottom channel of the frame supports the lions share of downward force, in between the two axles. The downward force applied to the ends of the frame, distal to the axles, is primarily supported by the top rail. It really is a mute point anyway, the end of the bus frame is overkill for what it has to do under a bus. You will not affect the function of the frame in any way bolting a hitch underneath it.

I don't think your design is up to 8K or 700 lbs tongue weight for a few reasons. I would try finding a hitch on craigslist, altering the width to fit your bus would be quicker than building one.
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