Pintle - Lunette: my findings

[ntsqd]

After years of dissing pintles I finally realized what was being done wrong. The cross-sectional OD of the lunettes are typically too small. Like this one:

See how much gap there is between the lunette loop and hook of the pintle? It should better fill the opening in the pintle. There has to be some gap for it to work right, but that gap is excessive and likely makes a lot of noise.

Compare the above pic to this:

Still has plenty of operational clearance, but way less opportunity to make noise. It wasn't until I bought the ring above that I realized that there are differences in the cross-sectional OD of lunettes. I though there was some std. out there that made them all the same. Not true. I now have a lunette like the one in the first pic destined to be recycled.

On the Bronc-up I will only have a pintle hook. I'll be able to tow anything that I need to tow with it and can drop a snatch strap on the hook, then close and latch it faster than I can deploy anything with a shackle.

 

[greentruck]

I suspect this is the case. I recall coming across sizing guidance on pintle/lunnette combos somewhere years ago. I would think it would be more commonly available info, but needs more digging it seems.

We use a Reese 8-ton combination pintle. It would seem to be noisy, but isn't really.q

Our M101 CDN came with this lunette, with a round cross section of ~1.75"

In more of a side view, you can see how its beefiness works in favor of less noise when fitted correctly. There's a little over 2" of room inside the pintle, but if you look closely at the design, there's actually less than that due to the way the ball part of things intrudes into the space.

There's very little clank and clunk with this set-up. There's noise from time to time, but I wouldn't call it noisy.

 

[ntsqd]

By "cross-section OD" I mean the diameter of the ring, not the torus. Looks like your sample is about 1.50"

I was given one of those combo ball/pintle set-ups. Initially I thought it a good idea, but after looking into just how these couplers are supposed to work I think it less than ideal. No way in hell would a put a snatch strap on it, and it lacks the graceful curve that would allow a smooth break-over transition thru the coupler. I'm sure it will work, but the lunette ID to 'hook' clearance will be varying depending on the break-over angle.

 

[greentruck]

By "cross-section OD" I mean the diameter of the ring, not the torus. Looks like your sample is about 1.50"

SNIP

Not sure I'm following completely without getting the dictionary out and studying a while - and the wife is pressing to go to the store. A quick remeasure shows what I measured roughly the first time as a 1.75" diameter is as you say closer to 1.5". Outside lunette diameter is 6.25" and ID is 3", so the difference comes out to roughly equal the 1.5" ring diameter. Of course, it is Canadian/NATO stuff, so it's really all metric anyway.

I'll get a picture of it all hitched together when I get a chance. It leaves little room for slack between the two mates. I'll certainly agree that you don't want to smack it much on stair steps, but I'm more likely to encounter a standard coupler trailer needing hauling than some of them uglies these days. Can always swap it out by loosening 4 bolts if a full-pintle hitch is a better idea in my travels in the future.

I have an old tree saver that would keep a strap hitched up in a pinch, but I wouldn't put a big load on it. I tend to not like hitches as snagging points anyway if things get super down and dirty. I also tend to not get myself stuck that badly in my old age anyway, knock on wood.

 

[scrapdaddy]

I use pintles on all my farm and float trailers, because they just work with no worries of them popping off. I learned that long ago to size them right and you won't be banging around. I have several military vehicles up to a deuce and all of their pintles are tight. Even on my 55 I use a 15 ton pintle, sorry but that combo hitch would worry me if hauling a big load. I'm assuming you use it just for a small camping trailer.

 

[greentruck]

Ron,
It's what I use with our 1/4 ton M101 CDN. It's rated at 8 tons. I'm assuming that a roughly 1:8 actual weight to ultimate capacity margin should mostly keep me out of trouble...

 

[e9999]

what's the big deal with a little bit of clanking? That way you easily know the trailer's still back there...

 

[scrapdaddy]

You're right about that, sometimes you can't tell they're back there. I had that feeling a while back, caught myself day dreaming and had to pull over just to check...

 

[greentruck]

what's the big deal with a little bit of clanking? That way you easily know the trailer's still back there...

e9999,
I think you're spending a lot of time towing with your 100 series. Seems like I put the first bag of dirt in the 1/4 ton behind the 80, I can feel it starting to slow down. Good thing we have little in the way of, what do you call them? -- hills? -- around here,

 

[e9999]

nope, I do all my pintle towing with the 80, turns out. And yes, it's not the best tower in the world.
But come to think of it, you have less clanking with hills than flat land, likely.
Should also add that on one of my lunettes I have a spring shock absorbing system, that helps a bit maybe.

 

[greentruck]

Yeah, flatlands and stoplights will drive you nuts if you don't have the clank minimized by proper sizing, etc.

The sprung mounts come in several different flavors. They probably do help, but they won't eliminate clank.

Just to clarify, you're talking about shock absorption, not rotation of the pintle, which was what first floated to the top of my crusty old brain.

Still, since this is a thread about pintles and specs that got me thinking about a document I've seen before, but it's been a few years. NATO standardized on an agreement that required the pintle to rotate, but to be lockable, and provided that the lunette NOT rotate. Is that what doomed the M101 CDN from further service, leading to all those desireable trailers hitting the surplus market? I doubt it, buti t didn't help that it was non-standard. I don't know if conversion of non-standard equipment was required or not. Shock absorption for the hitch assembly is an option, but if used should be mounted in the drawbar part of the system, not the pintle. More here: https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=11&ved=0ahUKEwjg1_naia_aAhVI7oMKHXpQDqg4ChAWCCgwAA&url=https://www.tenderned.nl/tenderned-web/aankondiging/detail/documenten/document/8d14aaba24d76497ce0e64400a0d5d34/pageId/D909C/huidigemenu/aankondigingen/map/a07276e21d21f0aa1f17d8c8878733d0/akid/6933b39ea971a6391080302f83313fd6/da/false/actie/aa274b487977199c90ed89bf7fb5b3adf319e66f5d0d86ee89d634f7ec8ea825b560366cc6cb9e9ed68ee310df42c04f1cc1862341c2128997415317b39e2617b100d520d07b4e25519806451311da19/cid/400829;jsessionid=29237F8A37183539857EBA1FE707310C.node4&usg=AOvVaw18yw3GDIixhK4XZCTieEHo

 

[scrapdaddy]

Interesting information, Looking at the different dates on the doc. first edition 1967, 1996 and this second edition in 2000. My 1951 M37 and 1971 Deuce both have rotating pintles, I wonder if Nato just followed along with the USA.

 

[NMC_EXP]

I've owned M101A1 and M101A2 3/4T and M416 1/4T trailers with original GI lunettes. Always towed them with GI pintles both mounted on civilian vehicles and on an M37B1 and an M1009 CUCV The fit is snug. What slack there is is not bothersome to me.

It is a stout hitch system.

 

[ntsqd]

Interesting that the document lays out the dims for the lunette, but doesn't specify any dims for the pintle. Clearly the hook of the pintle has to fit thru that 76.2mm hole in the lunette, but beyond that it is wide open.