Plant ring hitch size

Woody.v8 · Dec 5, 2015

I'm wanting to make a heavy duty straight bar for towing/shunting ,Does Anyone know what size the "ring" hitch is in the UK ? As in the ring to fit in the ball and pin towbar.

colnerov · Dec 5, 2015

Hi, you can have it more or less whatever size you want, so long as the pulling load is on the pin and the pushing or braking load is on the jaw not the pin. They are available off the shelf to either weld or bolt on, although this site doesn't show bolt on I'm sure that could be remedied. -

http://www.malpasonline.co.uk/s/c/accessories/trailer-parts/towing-hitches-components

Colin

Woody.v8 · Dec 5, 2015

Really? But a 50mm hole and a 25mm pin is like a dick in a shirt sleeve

colnerov · Dec 5, 2015

Hi, yes, as I understand it's so the load is only on the pin one way. If it was both pulling and pushing it would promote metal fatigue much quicker and because the pin has a tolerance in the hole of the jaws it would also increase wear. I was surprised as you are at first when I was told it years ago.

Colin

Spark plug · Dec 5, 2015

I would use a ball hitch as the majority of people have a ball but not a pin hitch.

It is fine haveing a ring until you need a tow from someone without one. Also there isn't any strength advantage of useing a ring, only advantage may be if you like the banging.

rory1 · Dec 5, 2015

I can measure a few rings when I get to the yard around midday.

My 3500kg pin on my towing hitch is only around 3/4 iirc

pedrobedro · Dec 5, 2015

pdg said:
The other advantage is a very slight theft deterrent...

Because not everyone has a pin hitch, there's that tiny chance they won't be able to just hitch up your trailer

If they are in the business of stealing trailers they will have a drop box so they don't need a pin or ball hitch

colnerov · Dec 5, 2015

Hi, If they're stealing trailers or caravans, they will have stolen the towing vehicle as well. Because if it goes wrong or they get rumbled they can abandon the whole rig and it not be traced back to them.

Colin

rory1 · Dec 5, 2015

Anyways, back on topic , ring hitch is off a road tow compressor, and the ball/pin hitch is a 3.5 t rated one off the back of a defender

Mick Annick · Dec 5, 2015

We shift a lot of trailers for utility companies, all of which are either 30mm or 50mm, depending on the GVW of the trailer.

Woody.v8 · Dec 5, 2015

Cheers chaps, I will knock one up, In all the years that iv'e been around plant i never realised that the front of the ring touches the jaw under braking :ashamed:

The first job is a bit dodgy I need to straight-bar my forklift about a mile to my other workshop

AndyStobbs · Dec 5, 2015

Can someone explain why the braking load should come against the jaw and not be borne by the pin?

Woody.v8 · Dec 5, 2015

colnerov said:
Hi, yes, as I understand it's so the load is only on the pin one way. If it was both pulling and pushing it would promote metal fatigue much quicker and because the pin has a tolerance in the hole of the jaws it would also increase wear. I was surprised as you are at first when I was told it years ago.

Colin

AndyStobbs said:
Can someone explain why the braking load should come against the jaw and not be borne by the pin?

Bill Edwards · Dec 5, 2015

I think that most agricultural stuff has all the forces on the pin...

Justme · Dec 5, 2015

Bill Edwards said:
I think that most agricultural stuff has all the forces on the pin...

None that I have used ever has.

AndyStobbs · Dec 5, 2015

I missed that, can't see the issue myself. Millions of pins see two way loading all the time - hydraulic cylinder ends come to mind immediately.

Most tractors have the hook end of the draw bar in use. Don't have to leave the seat!

Woody.v8 · Dec 5, 2015

pdg said:
Aren't hydraulic cylinder ends usually rose jointed to avoid the hammer action experienced by a the sloppy fit found on towing rings?

Sometimes, Usually they use a phosphor bronze or oillite bush and pin but like you say they are a good fit so no lash, plus hydraulic rams are slow in comparison to a trailer ring thrashing fore and aft.

Bill Edwards · Dec 5, 2015

There isn't the harshness with most hydraulic applications either. Even on the most basic crawler loading shovels where the bucket is on the ground meeting varying levels of resistance as the work changes it still isn't as harsh as towing something. Even on systems without any method of dampening, the hydraulic hoses have a bit of give and smooth things out to a degree.
Towing a trailer with a pin is a very different matter. Every undulation in the terrain, speed increase or decrease results in a harsh bang, metal on metal with large clearances.

Bill Edwards · Dec 6, 2015

Justme said:
None that I have used ever has.

Here's two draw bars I saw today:

This one is wrong in that one jaw should be removed, but it would still have all the forces on the pin.

This one, you can clearly see that you would need a massive ring (NATO kind, nothing agricultural) before it could brake against the drawbar.

For trailers which have the 50mm ring for a pickup hitch to be used with a drawbar pin you are supposed to use a bush to remove the slop. These almost, if not always, move the ring too far from the drawbar by centring them. If you don't use the bush you have about an inch of movement available in each direction and in most cases still wouldn't have the braking against the drawbar even then.

In short, agricultural stuff puts all the force on the pin.

Justme · Dec 6, 2015

I think your right. I guess my memory of what it looked like is a bit iffy.

Only have an old 165 now that I use to power the log saw, splitter & occasionally the 15kW pto genny.

That first one looks well wrong.

Is that a bolt being used as a pin?

Looks far too small for the hole.

Plant ring hitch size

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