Rotating Lunette (1 Viewer)

[ntsqd]

As part of my experiment with a pintle and lunette I tried to buy a rotating lunette and couldn't find one. The M416 tongue castings are seemingly pretty rare, and the lunettes are in high demand. So I decided to build a rotating lunette.

I found the ring on Amazon and those are 1-1/2" threads, something that's not clear on the amazon page. The two washers closest to the plate are thrust washers from mcmaster.com. The 'washer' closest to the ring itself is actually a Belleville Spring Washer, also from mcmaster, which allows me to set the pre-load on the thrust washers to change how easily the lunette can be rotated. I would rather that the trailer be able to roll and not take the truck with it, but I also don't want it to flop over easily. The pre-loading makes a nice friction brake for the rotation.

I know that others have pondered this and I thought seeing how I did it might spark some ideas.

 

[Mark W]

While I have not bothered to look for them anywhere, there are also rotating pintles. I have one on the back of my Loadstar.

Either way, pintle or lunette, rotating is the way to go.


Mark...

 

[spotcruiser]

I have seen new M416 lunette/housing castings for sale. Military Hummers have rotating pintles and I have seen them for sale. I like the idea of the rotating pintle, but I wouldn't drill that large a hole in my rear crossmember without beefing the crossmember up considerably.

Here's a link to lunettes and housings:
http://www.midwestmilitary.net/trailerparts.html

 

[ntsqd]

For the time being I'm stuck with using a socket receiver, so the rotating pintles weren't an option. If my experiment works out I think that I'll be putting a pintle only on the FJ, in which case one that rotates will be the first considered.

At over $350 for the 416 parts and then I have to figure out how to integrate them into an existing tongue I figured that I'd have the same amount of time and be money ahead to build it. If I could have found someone selling a housing off their trailer for a reasonable price I might have gone down that road. This design allows me to pin it to any 2" square tongue.

I've not kept all of the receipts, but I'll guess that I'm about $125-$150 into this when the mcmaster parts are included (as they should be). Time-wise I have about 4.5 hours into building it. I have a little more work to do, and I see in the pic that I have a little more painting to do too. Plan is to drill the ends of the four 9/16 G8's and add a safety wire keeper so that even if the prevailing torque nuts do back off that they can't get away.

 

[Volcanic Iceberg]

I made one as well. Not quite as ellegant as yours but rotating non the less. I just squared off and welded the giant bolt iinside the reciever stock. I run it unscrewed 180 deg. so that I have full rotation either way. Be carefull, I found out the hard way that when they rotate, they can bind up with the pintle and damage your hitch if you are backing up a hill at an angle.

 

[sggoat]

I have an m101A2 with hyd surge brakes. I like the idea here of the rotating Lunette. Any advice on how to proceed to get mine into that configuration?>

 

[ntsqd]

I think that a rotating pintle might be easier to implement in your case.

 

[BionicCruiser]

I was luck enough to have built my trailer tongue from scratch. my lunette has the bolt attached to it and bolts through a plate on the trailer. kind of hard to see in this pic, but it's the best I have for now. and I have had no binding issues with a regular pintle(not a combo pintle/ball) hitch.

 

[sggoat]

where can I see these rotating pintles? Are they available at any trailer supply sites/stores?

 

[ntsqd]

This one is probably too big, but its illustrative of what you're looking for.

http://www.northerntool.com/shop/tools/product_200328809_200328809

 

[Mark W]

I have seen a couple of instances where a trailer roll would likely have been avoided if the pintle/lunette did *not* rotate. If the connection had been non-roating AND heavy duty enough, the trailer probably would have limited out in movement at the connection and bicycled with one tire high in the air and come back down as the rig up moved forward. A lighter duty setup would have just bent or been damaged however. in fact, a heavily loaded M416 dropping back down like that would not be a comfortable sight either.

And I have seen a couple of situations where the rotating lunette kept the trailer from going over when the rig towing it did.

All in all looking at the different situations we have gotten the trailers and rigs into, the rolls and not rolls i have seen, I prefer the rotating connections.


Mark...

 

[ntsqd]

It was scenarios exactly like those that drove my using the Belleville Washer to create a friction brake against rotation. I currently have it set such that it takes a ~3' long bar to easily rotate the lunette, and there is room to increase the pre-loading should experience show that it should be.

 

[Mark W]

All of the times that we have rolled trailers attached to rigs or rigs attached to trailers the terrain was what was forcing the lift or an obstruction the trailer has been drug over. The forces involved there will over come any preload.

The M416s and the M100 that we use all have heavy preload on the Lunette, but it really does not seem to make any difference. And the weight of 1 of them loaded with 100 to 150 gallons of fuel and gear in addition will overpower any preload as it comes back down too.

The preload to stiffen up the rotation of the lunette as opposed to letting it rotate freely is definitely a good thing. I'm just not sure how much different it actually makes in many situations.

 

[ntsqd]

When there's something besides inertia forcing the roll I expect the trailer to roll. It's those times that the trailer catches a bad bounce and would only flop if unrestrained that I'm hoping to prevent. Your experience is reinforcing what I had guessed, so thanks for that.
At this point in life I'd be surprised if I ever flop a trailer, but I don't want to be caught off-guard if it does happen.

 

[Mark W]

I have had trailers dancing and catching air behind me a few times when we're rallying down braided gravel river bottoms at higher speed. I generally take that is a cue I should probably slow down some however.

Situations like that are where I see the preload coming into play more than slow speed situations where the terrain simply says you're going over.

For me the most frustrating trailer rolls are the ones were the brush your driving through is stout enough to stand back up under the trailer after the cruiser goes over it and then lift the trailer and roll it even though it's heavily loaded.

Mark...

 

[e9999]

Besides the 2 other types I already have, I'm going to build myself a rotating lunette with a ring like yours when I have a chance. Already got the ring, very similar to yours if not identical. But I would rather use a solid plate welded to the receiver insert that I would bolt the lunette to over the 4 bolts system you have used, those don't look that sturdy to me, just from the photo at least.

 

[misterpepper]

I second the warning of Volcanic Iceberg about backing up a trailer with a rotating lunette. In his case the lunette rotated approx 150 degrees and bound up the pintle, nearly ripping it off of the tongue. Check out his trailer build thread for pics. Nasty stuff. The theory of allowing it to rotate is sound, but I'd limit the total rotation to no more than +/- 45 degrees, with a stout hard stop to the rotation. That should be more than enough to get the benefits while avoiding the nasty side effects.

 

[ntsqd]

Those bolts do look spindly in the picture, however they are 9/16-18 Grade 8's stuck thru some 1" x .120" wall tube. They are arranged on a 3.5" square pattern. It is the shear mass of the stuff around them that makes them look puny. The threads on the ring are 1.5" OD, I had to use a 24" Crescent on the nut as none of my mixed jumble of 3/4" drive sockets went big enough. The nut will not fit inside of a 2" tube, nor will it fit inside of the 2" ID socket receiver tube that makes up part of the rest of the assembly.

With the friction brake function built into the rotational part I don't expect any trouble in backing up a ~1500 lbs. trailer, but I won't take it for granted either.

 

[misterpepper]

Here's the problem with the rotating lunette when backing a trailer: as soon as you get the trailer on an angle you'll be pushing it with the lunette shaft through 2 joints (the lunette/pintle connection, as well as your newly added rotation point for the lunette) separated by the distance between the centerline of the lunette and the ring. In pulling this works fine because the tension always wants to keep things straight, but in pushing these two will want to fold over on themselves, especially the further towards 90 degrees between the trailer and tow vehicle you get. In a turn the lunette will start out pushing from the front of the lunette like you would expect it to, but without warning the lunette can rotate either over or under so that it is pushing the trailer from the back of the lunette. The 2 joints will want to find a way to be in tension, but you are expecting them to stay in compression the whole time. I don't think your added friction will be enough to stop it, either. Anyway, the real problem isn't even the lunette fliping when you back up, it's that when you pull forward it doesn't flip back, creating a real mess of angles and forces that will twist even the stoutest of tongues and hitches into an intertwined pretzel.

 

[ntsqd]

Did the failure that you're basing this on use a true pintle or one of the combo ball/pintles?

The 'pure' pintle that I have limits the lunette's rotation to a surprisingly small angle. I'd guess less than 45° included. It's really no better than a std ball coupler in that regard. I'm trying to picture the failure mode and I'm not seeing it. Later today I'll hook the pintle to the lunette and play it.

I don't discount that there could be a problem, but I think that you might be under estimating the anti-rotational force that this system is capable of generating. Compressed flat the Belleville that I used generates a little over 10,000 lbsf clamp load. I don't have it set that high, but I can if need be.