I am following Gumpy's hitch that he built for his father in law.
Here is the link:
http://www.busconversions.com/bbs/index.php?topic=8888.0 (http://www.busconversions.com/bbs/index.php?topic=8888.0)
A difference is that I am using 2x4 box stock for the main crossmember and I have an issue to overcome. The flat plates follow the curve of the body and my 2x4 is straight. I am getting a gap of about 1/4 inch between the plates and the crossmember at the outermost ends. My plates are 3/8 inch, and wouldn't easily bend. I have a notch cut in the bottom of the 2x4 to accept the reciever. I see a few options, and I'd like your opinions.
I could:
1. Use some scrap stock, fill in the gaps and weld up.
2. Cut the 2x4 at an angle where it meets the reciever and make the angle (I'm thinking this might be best)
3. Weld everything square and shim the plates where they meet the outside of the curve in the body. (probably the worst)
Thanks in advance!
Glenn
Glenn,
I have a MC-7with a Reciever I welded a angle iron on each end,drilled 4 holes and mounted it to the frame. On page 2 of all topics,oil leak repair, you can see it in on of the pictures but not real well. If you'd like I'll take some better ones tomorrow. It's not as strong a gumpys, but I'd pull anything with it. Just a nuther idea.
Richard
RD,
I don't see the picture and I don't see a link to your photobucket account. Could you help me out? Thanks!
Glenn
Glenn,
Here's a picture.(https://busconversionmagazine.com/forum/proxy.php?request=http%3A%2F%2Fi651.photobucket.com%2Falbums%2Fuu231%2Frdbriverrat101%2FOil%2520Leak%2520Repair%2Fth_oilleak002.jpg&hash=df25b899b0f22d93980e4dcaeea305eb8143389a) (http://s651.photobucket.com/albums/uu231/rdbriverrat101/Oil%20Leak%20Repair/?action=view¤t=oilleak002.jpg)
Great photos Richard! I assume you drilled and tapped your frame for the bolts? How much material is in the frame at that section?
Glenn
Quote from: Tenor on May 29, 2009, 07:24:37 PM
I am following Gumpy's hitch that he built for his father in law.
Here is the link:
http://www.busconversions.com/bbs/index.php?topic=8888.0 (http://www.busconversions.com/bbs/index.php?topic=8888.0)
A difference is that I am using 2x4 box stock for the main crossmember and I have an issue to overcome. The flat plates follow the curve of the body and my 2x4 is straight. I am getting a gap of about 1/4 inch between the plates and the crossmember at the outermost ends. My plates are 3/8 inch, and wouldn't easily bend. I have a notch cut in the bottom of the 2x4 to accept the reciever. I see a few options, and I'd like your opinions.
I could:
1. Use some scrap stock, fill in the gaps and weld up.
2. Cut the 2x4 at an angle where it meets the reciever and make the angle (I'm thinking this might be best)
3. Weld everything square and shim the plates where they meet the outside of the curve in the body. (probably the worst)
Thanks in advance!
Glenn
Glenn,
We had the same problem. That's why we cut the main beam at an angle, and inserted the receiver tube. The two sides come in from an angle from the side plates which
are at a slight angle due to the curvature. Look closely at the 4th photo on the old thread. You can see the angle in the support plates below the receiver.
craig
I thought so Craig. I'll do the same thing. Just ran out of wire while repairing the corner triangles and it just started raining. I'll get back on it soon. Thanks!
Glenn
Glenn,
Here's some better pics
(https://busconversionmagazine.com/forum/proxy.php?request=http%3A%2F%2Fi651.photobucket.com%2Falbums%2Fuu231%2Frdbriverrat101%2Fth_oilleakHitch005.jpg&hash=7bcfa91c8e39bdcfd55c9e92d01db6cdd133853f) (http://s651.photobucket.com/albums/uu231/rdbriverrat101/?action=view¤t=oilleakHitch005.jpg)
I'm sorry guys but I don't like it. This hitch displays the same fundamental design error that I have seen on too many bus hitches. If I understand the photos correctly the same piece of square tubing (3 x 3 it looks like) is expected to both carry the weight of the towed attachment as well as pull the load. I'm no engineer (no surprises there!) so I can't explain why that is bad in technical terms but the farmer explanation is this: you need something to carry the weight and something to pull the load. What I see in the photos is adequate to carry the weight but there needs to be some forward extension to help pull the load. IMHO.
This (http://www.busconversions.com/bbs/index.php?topic=8388.msg83161#msg83161) is an example of what I am talking about, although its not the best picture. The cross member at the extreme rear which carries the vertical load from the receiver tube is easily visible. If you look closely though you can see that the receiver tube also extends forward to a second crossmember which helps distribute the pulling load. The OP's hitch as built may very well function for a long time and may never give him a problem but doing it right the first time takes very little additional effort.
Here is picture of the hitch so far. The flat plates are 3/8, the crossmember is 2x4. I think I will take a page from Richard's and weld angle stock to the crossmember to bolt onto the frame for additional strength. Here is the link to photobucket for more pictures:
http://s613.photobucket.com/albums/tt216/tenor007/ (http://s613.photobucket.com/albums/tt216/tenor007/)
Glenn
(https://busconversionmagazine.com/forum/proxy.php?request=http%3A%2F%2Fi613.photobucket.com%2Falbums%2Ftt216%2Ftenor007%2FP1000812.jpg&hash=eef24d8cffd318ddcfdc117ff9bdd76a9e8dedf6)
You've got half a hitch as far as I am concerned. What you have built is adequate to hold the vertical load on the receiver. Figure out some way to attach the other end of the receiver tube further forward on the frame and you will have a complete hitch. IMO.
(on edit)
If you ever plan to do anything more than flat tow a very light towed then you need something heavier for the cross member. That looks like 125 wall tubing - even if it is 188 wall it isn't heavy enough. You are asking that tubing to both carry and pull the load. It can't do it.
bob,
The 2x4 is between 3/16 and 1/4 inch, the same as my factory hitch on my truck that carries a 1964 Ford Galaxie on a car hauler. The cross member weighs over 30 lbs. Any heavier and I'd need a trailer to carry my hitch! ;) Am I missing something?
Glenn
Quote from: bobofthenorth on May 31, 2009, 06:32:16 PM
You've got half a hitch as far as I am concerned. What you have built is adequate to hold the vertical load on the receiver. Figure out some way to attach the other end of the receiver tube further forward on the frame and you will have a complete hitch. IMO.
(on edit)
If you ever plan to do anything more than flat tow a very light towed then you need something heavier for the cross member. That looks like 125 wall tubing - even if it is 188 wall it isn't heavy enough. You are asking that tubing to both carry and pull the load. It can't do it.
I disagree. He's got a good start. He needs to grind the top weld and plate across the seam, and then plate across the receiver tube after it's welded in. He's already repaired the triangle frame members. The tube and side plates look fine for towing a toad or small trailer, which is all the bus is really designed to handle. I don't think he's planning on pulling a 15000 lb trailer.
You aren't missing anything other than that its a bad design and its not heavy enough. But its your hitch.
Quote from: bobofthenorth on May 31, 2009, 07:10:40 PM
You aren't missing anything other than that its a bad design and its not heavy enough. But its your hitch.
The hitch is fine. It's attached with ten 1/2" bolts and welded solid. If his engine cradle is in good condition (and I'm sure he's checked that, considering he's repaired the braces) that hitch will pull any toad 4-down, and will handle a trailer up to about 10000 lbs.
If the hitch is going to be seeing
any tongue weight there is not
enough torsional strength in that
design.
Dave Rasor
I have some repair to do to the engine frame, but I need some assistance in welding the stainless steel. I see one diagonal and 1 upright that it attached to are busted out. I also need to search for cracks. Gumpy, you are right that I plan to grind the top center weld at the reciever and plate over it and plate over the bottom of the receiver and use that plate for chain mounts.
I do plan to haul a 17 ft enclosed trailer with 2 harleys (about 4k total weight) or my flatbed car hauler with car (about 5-6K total weight).
Dave,
Where on the hitch do you see the problem? Or do you think the problem is in the mounting point? I'd like some more specifics please.
Guys, I really appreciate the help.
Glenn
This is crude so excuse the lack of drawing skills and remember that I'm no engineer. But I've built a lot of hitches and a lot of things a LOT bigger than this hitch.
(https://busconversionmagazine.com/forum/proxy.php?request=http%3A%2F%2Fwww.rjevans.org%2FRJEvans%2FHitchEndView.JPG&hash=2775eb67b5a430f1b0381b627b27688fa0f0630d)
The black arrow shows what happens to your hitch when you put weight on the receiver. The effect of the load is to try to torque the two pieces of 2 x 4 tubing which meet at the receiver. You need to resist that loading. The easiest way to do that is to apply some reinforcement where the red arrow is. If you put some form of bracing running forward so that the torque on the receiver is resisted it will greatly increase the strength of your hitch. Alternately you need to deal with the torsional stress in the tube and I don't have any real world experience with that but I do know that 188 wall tubing isn't strong enough torsionally for what you are doing with it. The issue is absolutely NOT about how well it is attached to the cradle. A properly designed hitch can easily be held on with 6 x Grade 5 x 5/8" bolts.
What Bob is suggesting will make a better hitch & will likely reduce the stress on the attachment points to the frame.
Bob,
I see the issue with that design as you have illustrated. I don't know how to do those drawings, but I can tell you some differences between your drawing and what I have built. The support plate comes all the way down to the bottom of the 2x4 which should add strength opposite to the leverage of the hitch and tongue. Also, the receiver will be inserted into the 2x4 to the point where the bottom of it will be flush with the bottom of the 2x4 which also reduces the leverage applied by the trailer. The point of greatest twist should be directly against the 3/8 steel plates at the bottom and the greatest point of pull should be the weld at the top of the 2x4 where it meets the plates.
I did find the brackets on the frame that Craig used to help out with this rotational problem on his father-in-law's hitch and I could duplicate that as well. If I should do that, I'd plan to recess those bars into the 2x4 as well.
I didn't see anyone's take on the idea of attaching angle stock to the 2x4 and attaching it to the frame like in Richard's picture and I think that might do the job to reduce the torsional stress.
Please don't think that I don't want to hear criticisms, I just want them to be well spelled out so that we ALL understand and learn. That's what this place is for! :) I'm looking forward to responses!
Glenn
.
I understand what Bob is saying regarding the rotational forces on the receiver. Those forces will be there when pulling a trailer, and the longer the hitch bar, the more rotational force there
will be, but for the loads that he's planning to carry and the way it's attached to the bus, what he has is fine. With the plates extending to the bottom of the cross tube, and welded both top and bottom, and with the overlapping framing under the triangle mounting members, there's little chance these forces will be high enough to cause bending or twisting of the plates or cross tube. That tube is only about 4 feet long and 40% of it is attached to the mounting plates.
On the hitch we built for my friend in AK, we added tubing from the receiver angled forward to the small frame brackets, which will aid in prevention of the rotational forces. Glenn should probably consider doing something similar on his.
I like the large brackets on the forward end of the hitch in the photo Cody posted. They would provide better support than the little brackets we used on my friend's bus. I don't know what those bolt to, though. You'd probably have to add some brackets to the engine. I don't like the rearward brackets, though. Bolting upward doesn't work well on these buses.
On a side note concerning hitch loads, many think that flat towing a car poses little to no vertical load to the hitch. That may true for a properly installed tow bar setup with properly working toad brakes. . . . . BUT, after reading the RV discussion boards & from what I've seen on the road, there are way too many towing with out the proper setup.
The problem with a tow bar comes from it not being parallel to the ground. When the back of the RV lifts during hard braking, the bar is angled upwards & this geometry applies a vertical load to the hitch. If the toad doesn't have proper braking assistance, the vertical load becomes larger since the toad is pushing. Due to momentum & geometry, this vertical load can exceed the weight of the car.
The way the loads are carried by the hitch & frame can be quite involved with a poorly designed hitch. The better hitch design will simplify these loads, but everything is a compromise.
That is why I endorse spreading the mount points towards the front of the bus. They minimize the torque applied to the hitch attachment points.
I don't have much 3/8" plate in the frame of my bus, so now the hitch itself may be strong enough but what about what it's bolted to? The frame was designed to carry the motor (engine) with a certain amount of safety factor, How much of this will be used in the hitch?
This is why one needs to understand how the bus frame is already loaded & make the hitch in such a way that takes all of the loads into account.
This will be simple for some, but impossible for others. Just as some can do excellent in electrical wiring, others in upholstery, others still in engine repair. . . .
Not saying it can't be done. But I am saying one needs to be aware of the 'complications' involved in order to improve their chances of success.
(first edit)
Just a FWIW.........
I was always taught on but welds the metal should be V grooved before welding.
My own personal preference would have been to go with a larger rod.
Good luck
Skip
Hello: my first hitch on my 72 7 was like that and it failed after 200 miles pulling a saturn. THe area just above the welds will bend and the box will cantilever down. I ended up putting a piece of 3/8 angle about 8 inches long on the interior of both sides and welding it to the side rails to get home. I have redesigned that hitch and their are some pix somewhere here showing that one. You also need a bar back about 10 or 12 inches back from the front and a piece of channel running foward under the receiver. THat piece will keep the load from pulling the hitch down. Suprising the up and down forces on a hitch while pulling a car.
Sorry about the bad news but ...
Regards and happy busssin mike
.
That's a heck of a hitch! I can only say "it's not for an unmodified MCI 7". There are no downward facing mounting points at the bumper end of the bus. I think I've seen some bolts going that way on hitches for MCI 9's.
Glenn
Here are a couple photos of the hitch I made for our bus. Jack
I contend there is no difference between Jack's hitch and Glenn's hitch, regarding rotational forces, and actually, Glenn's design will handle more load than Jack's, simply because of the locations where they are attached. I also know that Jack typically only tows 4 down.
I agree with you Craig. Jack's hitch is depending on the torsional strength of the rear member as is Glenn's. However, on Jack's hitch, if there was some physical connection between the end of the receiver tube and the bar on the other end of the hitch then it would be what I consider a "good" design.
And Glenn, its your bus, your hitch. IMO you have a bad design that could be alleviated but never corrected by using heavier metal. It may never cause a problem but my advice would be to paint it with a high gloss enamel so that the cracks will be easier to spot when they (inevitably) appear.
Hello.....
Unless I misunderstand how that hitch in the pix will be mounted: The 3/8 plate will fail guaranteed. been there done that bought 2 tee shirts. I only used 1/4 inch plate for that section. That will fail but take a while longer than mine . Mine lasted 200 miles from mexico ny to winchester VA.
And I beg to differ but: it is not stronger than Jacks because there are no structural member on the longitudinal axis ( the same as the rails).
when I get time I will post my old pix but they should be in the archives somewhere..
Regards and happy bussin
Mike
Found it Mike........and thanks again.
http://www.busconversions.com/bbs/index.php?topic=5292.15 (http://www.busconversions.com/bbs/index.php?topic=5292.15)
This is page 2 page 3 has a picture just of the hitch.
Skip
How far is the hitch ball from the vertical plates that bolt to the bus?
If 12 inches or more, there is a lot of bending stress on the plates where the tube is welded to it. A 3000 lb tongue load will be very close to the yield strength of the plate. (assuming a 1/2" plate 12" long on each end)
You may not have that much on it in the parking lot, but what about rough roads?
Adding the forward mount all but eliminates the bending of the plate.
It will also reduce the localized hitch load as it is transfered to the bus frame.
Capping the ends of the tube will increase the strength of the tube by preventing it from distorting under heavy load, but I don't think the tube is the weak link in this chain. . . .
It all has to work together.
OK,
Here are new pictures. The plates are 10 inches long and the 2x4 is welded on 4 sides. Here is a shot of the end where you can see the contact of the hitch with the chassis.
(https://busconversionmagazine.com/forum/proxy.php?request=http%3A%2F%2Fi613.photobucket.com%2Falbums%2Ftt216%2Ftenor007%2FP1000821.jpg&hash=f1a6a2276c25123b4af727cc0913939c903649ed)
Here is a shot of the tongue inserted in the reciever. It is 10 inches from the centerline of the hitch to the center of the ball.
(https://busconversionmagazine.com/forum/proxy.php?request=http%3A%2F%2Fi613.photobucket.com%2Falbums%2Ftt216%2Ftenor007%2FP1000820.jpg&hash=b3bf70e5e35a8bb42fd4de5eb552e415cdc7d7b9)
Glenn
Here is a picture of the plate mounted to the chassis from the rear.
(https://busconversionmagazine.com/forum/proxy.php?request=http%3A%2F%2Fi613.photobucket.com%2Falbums%2Ftt216%2Ftenor007%2FP1000822.jpg&hash=7ab51cc66a5acfce31a6b454c4cc9df3f1c4b9ec)
And here is a photo showing the thickness and contact area of the plate.
(https://busconversionmagazine.com/forum/proxy.php?request=http%3A%2F%2Fi613.photobucket.com%2Falbums%2Ftt216%2Ftenor007%2FP1000823.jpg&hash=917a76f2a15206c9245d1a501429af1433544c0c)
Glenn
Good job Glenn,
I think it will do what you want it to do. They said my design was bad also, but it's been there since 1988 lots of miles pulling toad and trailers. So far no cracks.
Richard
Glenn,
What grade bolts did you use? They look like Grade 8 in the photo.
You don't want to use grade 8. You should use Grade 5.
(Or course I could be wrong again ;))
craig
Grade 8 bolts are stronger in every way than Grade 5 bolts, so there is no reason not to use them. Grade 5 is 120,000 PSI, Grade 8 is 150,000 PSI ultimate tensile strength. Use 2/3 of that as a rule of thumb for shear applications (SAE bolts are designed for tension applications and are not rated in shear). In this application, the bolts are in tension. At first glance, you might think that they would have a shear load vertically, but they do not - the friction created by the clamping load between the bus frame ends and the plates will far exceed the vertical load so the bolts do not come under vertical load - if the bolts are done up to correct torque.
If you want greater strength than SAE Grade 8, then industrial socket head cap screws ("allen" bolts) and L9 (a manufacturers trade name) are both rated at 180,000 PSI MTS. Above that, specialty fasteners go up to over 300,000 PSI, but you don't want to know how much they cost... It's an old wives tale that Grade 8 bolts are "brittle", they aren't, unless they are counterfeit. If you buy from a reputable supplier, they are a good choice.
I may be new to buses, but as a race car builder/restorer/driver I've been studying fasteners for 20 years... ;D
Cheers, Brian
There is compromise in every design.
A safety factor of 1 will work, but it doesn't allow any room for error or overload.
I prefer to minimize stress on all the parts & have as large a 'safety' factor as possible. Hence this discussion. I didn't say Glenn's hitch would fail. But, Glenn asked for input & input is what he got. ;D How he chooses to proceed is, hopefully, his business only. Like most everything else, if he chooses well, he will have success. If he chooses poorly, he will gain experience. :o
My '94 Explorer had the towing package & a receiver hitch bolted to the frame . After an unintentional overload was applied, the hitch was fine, but the frame was bent (over the rear axle a couple of feet past where the hitch was bolted). So while the hitch survived, the system failed.
The frame wasn't able to handle the load the hitch was able to transfer. If the hitch had transferred the load differently, the frame wouldn't have seen as much stress, but the hitch would have cost more, hence the compromise. . . .
Quality hardware is a must. So is routine maintenance of checking the bolts - especially at first to establish a base.
Craig, what is the reason for not using gr8 hardware? I'd rather not miss something. . . . but I thought it related to cost. In my designs, I try to design around gr2 hardware to prevent failure caused someone using weaker replacement hardware . . . . You may be surprised at how many don't know the difference.
Hello;
10 years ago during my hitch tribulations I consulted with my son in law a mechanical engineer we discussed stresses moments and stuff that went over my head. The bottom line was he suggested the following:
On the bottom picture on the right side just inside of the frame rail I added a piece of 3X4 OR 4X4 by 1/2 " thick angle about 8 inches long facing down with the cut ege looking up. we inserted it so the angle fit in the intersection of the plate and the frame rail running down away from you. In other words the angle was installed to provide a counteraction to the up and down of the hitch. For the road fix I stopped at a steel place and bought the pieces and had them welded in place.. one piece on each side will be enough to keep the hitch from dropping down Later I replaced the back leg of the angle
with a plate and put 5 bolts through the side rail. I used half inch grade 8s. THat back part of the frame rail near the end is pretty meaty. Actually the later design used a 10 by 10 plate that fit inside the frame rail with the hole cut out for the water pipe and I believe 7 bolts each side. Never had any trouble with that pulling a 24 foot car hauler loaded when we moved to florida.
During my first escapade I stopped on a flying J to fuel up and when I looked at the saturn the hitch receiver was pointing down. WE unhitched and the following morning I jacked it back up but it only lasted 30 miles so we left the car in winchester Va and headed south. Christmas 0f 99. We were headed to Savannah Ga to meet the kids for christmas. Arrived a day late..
Regards and happy bussin:
I sure hope your design works better than my initial try....
Mike
Looking at the photos above I don't think the bolts are the problem, you need to have someone look at the welds. I have one on my MC-7, don't make it yourself if you have to ask questions like this, think about your fellow bus buddies that may be behind you. Sorry if I have offended you and if you want pictures of how I did it let me know.
Larry
Hi Airhog, Welcome to the board ;D Your first post and you're already contributing-Way to go ;D ;D
Will & Wife