Binding much? Clenching much? (1 Viewer)

[BMThiker]

Is it just me or does the thickness of the lunette look larger than normal? Think fat donut versus skinny donut. Maybe just an optical illusion because of the drop/shouldered shape, dunno.

m416 lunette

OP's lunette

 

[ntsqd]

The common lunettes sold by more than a few trailer parts vendors & HF type operations are typically undersized in the OD of the toroid. I'm convinced that those parts specifically are the cause of the majority of the banging and clanging complaints. Not all, just the majority. See the attached specs. Curious if either of yours meet the lunette spec. I attached the 18k pintle spec because it shows that this lunette dim applies up to at least that high of a weight rating.

 

[audioviking]

I'll measure later.

 

[e9999]

you'd expect the lunette size to be a function of the load capacity of the trailer, no? It does not get much lighter than a 416. This is a heavier trailer.

I put a 105 lunette on my custom trailer. That thing is super beefy.

 

[ntsqd]

That seems intuitive, but it is not what I have seen with regard to the toroid dims. The rest of the lunette may change with the weight rating, but those two dimensions do not. The document that might provide illumination on this is STANAG 4101, which I just found for free (if you set the version to pdf) but the agreement forbids the sharing of it. It gives just one std. set of lunette dimensions, Toroid body OD: 41.2 ±0.8mm, Toroid center hole ID: 76.2 ±0.8mm, which in 'Murican is 1.622" ±0.032" and 3.00" ±0.032

From a military perspective making them all the same makes a lot of sense.

 

[e9999]

it's certainly true that having all the lunettes be the same would be better from an interchangeability and use point of view. (Although I would think that as long as they physically fit in the pintle the thickness of the torus itself need only to match the load.) So I guess in practice what you say simply means that the 416 torus is essentially oversized then, but that's no safety problem of course.
Your dimensions do indeed about match the lunette I have, which is an authentic NOS military 105 AFAIK. and looking at the pic above, mine has a similar looking torus aspect ratio but a much bigger shaft.
Good info, thanks!

 

[ntsqd]

My theory is that with the lunette's all the same toroid OD that the opening in all of the pintles can be the same. That means that the operational clearance gap is reasonably consistent. As a designer I'd be wanting to fine tune what the gap is before releasing the standard. Make it a big as necessary for function and as small as possible for noise reduction. A smaller toroid OD just means more noise due to the increase in the clearance gap, even if the application doesn't warrant that heavy of a part.

 

[e9999]

yup. Some clearance is needed for articulation when offroad, of course.

But looking again at the 2 pics above in post 21, it seems to me that the lunette rings themselves are indeed likely the same. There may be a visual illusion effect due to the very thick mount in the OP pic and the thin shaft for the 416. It is also unlikely that it would not be OEM given the hydraulic system. And it should be easy to check the NSN number stamped on it. But I can't imagine that the ring mount would have contacted the pintle short of an extreme jackknifing.

I'm curious about the thicknesses of the plates on the 2 hitch mounts in question.

 

[BMThiker]

Smaller toroid OD less likely to bind up as rust/patina build on surface is where I was going. Larger OD might have bound up in his original setup causing major deflection of receiver mount.

 

[e9999]

well, it's true that we are talking about military lunettes with commercial pintles so there is no a priori guarantee that they are suitably matching. Having said that, though, I never had a problem myself with those and it looks like there is plenty of clearance on mine. (added: I went to measure the ID of the pintle opening and it is 2". So about 1/2" clearance. Less than I thought, actually. )
As to the OP, there must have been something wrong going on, and likely the steel was just plain c..p.

 

[ntsqd]

Not saying that it hasn't happened the other way around, but every non mil-spec lunette that I've ever seen has had a smaller than spec toroid OD. I have a sample that I bought before I knew better that has a toroidial OD of about 7/8" I should just recycle it.
It was the observed variance in this particular dim that caused me to look up what it is supposed to be.

 

[e9999]

0.4" clearance in my case is not much. I would like more. I don't care about the banging. But I do care about binding. With so little, I would be concerned if I didn't have a rotating lunette. And why I make a point of always having one of the two sides rotating if I'm taking the trailer offroad.

I'm wondering if the milspec pintles are way bigger than mine. Mine is a smallish 8 tons Buyers.

I did go check another lunette assembly I have that I think came from a commercial or farm trailer. The dimensions are close to the milspec one, with the torus cross-section a tad thicker and a similar or slightly smaller ID.

 

[PAToyota]

As in you see a 1 cubic yard pile of sand on the ground, you think no big deal. Easy to move around with a shovel, right? So, can't be very heavy.

Yeah... Come back after you've moved that whole yard of sand with that shovel...

When I started building my workshop, I got 5-ton of crushed stone delivered and moved it with a shovel and wheelbarrow. The next weekend I went out shopping for a used skidloader.