Bus Hitch

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Ok so this guy has an old school bus he uses for his outfitting buisiness, and he wants to put a 5000lb capacity hidden hitch on it.  The frame it needs to mount to is 30" wide, and the mounting holes are 34" wide.  I am a welder by trade and I am completely comfortable making sound welds.  However I have little experience with this type of work (I do alot of pipe and tank fabrication)  I understand the importance of doing everything excactly right when working on frames, especially because this will be used on public roads often.  So thats why I'm asking for advice on how you more experienced frame guys would go about this project.  I was thinking of simply making a couple "L" shaped brackets and (welding or bolting??) them to the outside of the frame so that the hitch can bolt on.  And possibly slightly reinforcing the frame on the inside with "fishplates".  I don't know if I did a good job explaining this but I included pictures to help.  Please letme know what you think and if my initial plan is way off.  Thanks in advance.  Oh and I will be stick or Fluxcore welding this (NOT 110V)
Reply:We routinely drill and bolt pre-made hitches in place under the bottom flange of frames like that. The longer the hitch extends toward the front, the better. The side plates are normally 1/4" or more thick, and they are usually made with one bend lengthwise. That is a typical bolt on hitch over the counter.http://www.google.com/search?tbm=isc...87l0.3.4.2l9l0City of L.A. Structural; Manual & Semi-Automatic;"Surely there is a mine for silver, and a place where gold is refined. Iron is taken from the earth, and copper is smelted from ore."Job 28:1,2Lincoln, Miller, Victor & ISV BibleDanny
Reply:Best I can do is to give you an idea of how I used to put tow aprons on gravel trucks and log trucks and let you adapt the idea from there to suit your application.3/4" x 10" Steel formed into a "U" shape.  Vertical legs are the height of your frame rails, plus any additional drop you like.  The angle of the vertical sections are not critical - 45° if you like, but can be flatter to narrow up the horizontal section in a short drop of height.Horizontal section - To suit customer or application.  On a 34" frame rail, I haven't made them less than 24" wide in the center but up to you.Tow apron plate, again 3/4"Preheat and weld out with Hobart Fabco 110 <-- Just what I used, you don't have to.Use your existing holes in the frame, and an additional 2 or 4 holes at the leading edge of the flatbar to distribute the torsional force.Punch a hole and weld your reciver tube into the plate near the bottom, and gusset as needed on the "front side" towards the front of the truck.If you want to save some weight, you can taper the 3/4" formed piece a bit.  I would leave the vertical section alone, but the angled section can be tapered from 10" to a minimum of about 8" so you still have some meat to tow with.Others mileage may vary, but this sort of arrangement has worked for me in the past, and hasn't failed.Hope it helps. Attached ImagesLater,Jason
Reply:Well i have to apoligize I made this post and then got crazy busy and have not had a chance to reply. Thankyou for the advice.  Thankyou for the adivice Black Wolf.  That plan looks like it would work really well.  I was hoping to get away with something alot simpler and using less steel.  The reason for this is that if I use too much steel it would be more cost effective to just buy an adjustable hitch that fits with no modification. (which is what I would do anyway but hey it's not my bus or my money).  The customer insists on using the "hidden hitch" they already have. Anyway here is a very simple drawing of what I was thinking.. any thoughts would be great thanks. Red part is the modification, bottom black part is the existing htich, top black part is the bus frame.
Reply:IVe been in the outfitting buis for 20 years. Bus hitches are no joke cause of the distance from the rear axle. I used to argue with the local hitch guy about why the hitch frame rails are so short. He used to put on prefab units. Finally I got under there and cut them off and welded on new longer ones to keep them from breaking off. Now i have them all custom made. Nothing worse then watching your hitch assembly, trailer and canoes going the wrong way. Even worse is getting to the launch site and getting out to discover it's gone and you have no idea where it went! The trailers are so light that you cannot even feel them back there lol. In 20 years of outfitting I've seen it all.------------------------------------------Millermatic 185Miller Dynasty 200dxHypertherm powermax 30
Reply:jayj8 your plan looks fine to me, I'd try to bolt to the original frame using grade 8 bolts, avoid welding on the bus frame but if you do, keep the welds longitudinal to the frame, don't make a continuous vertical weld which could cause the frame to crack (stress riser).  You probably already know this.Black Wolf - thanks for your detailed post,your plan looks solid to me.  I am looking for a new (to me) dump truck and if it doesn't already have one, I will need to build a mounting plate for a pintle  hitch to pull a tag float trailer."The reason we are here is that we are not all there"SA 200Idealarc TM 300 300MM 200MM 25130a SpoolgunPrecision Tig 375Invertec V350 ProSC-32 CS 12 Wire FeederOxweld/Purox O/AArcAirHypertherm Powermax 85LN25