Position of pintle.

I don't understand why the position of the pintle, step down or step up, makes so much difference to the towing capacity, to me the centre of pull doesn't change.
The reason I ask is in the pintle turned down position (maximum towing capacity) my van is sits in a nose down attitude, BTW, I have a 2" lift and air bags.
Wondering.
Rob.
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Reply By: Olsen's 4WD Tours and Training - Friday, May 28, 2010 at 06:59

Friday, May 28, 2010 at 06:59
Are you saying that the manufacturer has set different capacities based on the position of the pintle?
AnswerID: 418490

Follow Up By: Olsen's 4WD Tours and Training - Friday, May 28, 2010 at 07:01

Friday, May 28, 2010 at 07:01
The manufacturer of the vehicle or the pintle?
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Reply By: Member - Serendipity(WA) - Friday, May 28, 2010 at 08:09

Friday, May 28, 2010 at 08:09
Printed on my tow hitch which is a toyota OEM part there is a diagram showing the pintle being position down or up and the 300kg point load is written as the same in either position.

David

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AnswerID: 418500

Reply By: brownie - Friday, May 28, 2010 at 10:21

Friday, May 28, 2010 at 10:21
racinrob
Have you got a pintle hitch on your vehicle or are you asking about another kind of tow hitch ?
A pintle hitch takes a round ring trailer coupling , iby its design it would only pull in one position - in the centre at the back.

Cheers, brownie
AnswerID: 418515

Reply By: racinrob - Friday, May 28, 2010 at 10:56

Friday, May 28, 2010 at 10:56
To clarify my original post, I have a genuine Toyota towbar which is also called a hitch receiver into which goes what I call the pintle. On my pintle is a small plate which shows the two positions, in the down position it says "Towing capacity 2270kgs" and in the up position the towing capacity drops to 1600kgs.
I can't see why it differs as the direction of pull is basically the same. I also have a Hayman Reese pintle which has no plate so I presume it doesn't matter which position it is in ?

Confused Rob.
AnswerID: 418523

Follow Up By: Member - Graham H (QLD) - Friday, May 28, 2010 at 11:40

Friday, May 28, 2010 at 11:40
The difference can be, if the bar that holds the towball is welded to the box section on a 45deg angle.
The forces put on the bar then differ.
I have seen it explained that the forces are different due to the angle of the weld.
EG if bar is on top more force applied to weld across the top and therefore not spread as evenly through the whole box section weld when in the lower position.

Nissan have a tongue like that and recommend it not be turned over.

The Hayman Reese bars are usually a 90deg butt weld so wouldnt make any difference


Am just repeating what I have read so dont shoot the messenger
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Reply By: Nargun51 - Friday, May 28, 2010 at 11:59

Friday, May 28, 2010 at 11:59
Makes a bit of sense (I suppose).

Look at the vectors of force in the different positions (its been over 30 years since I’ve studied any physics so forgive me any errors)

If the pintle is attached directly to the receiver in a straight line the towing force will be directly along that line of the receiver and the only other forces would be downwards ‘ball weight’. The connections to the chassis only have to cope with the linear towing force and the downwards ‘ball weight’.

Think as it a right angle triangle. If the pintle is level the towing force is a straight line plus downward weight. When you raise or lower the pintle the forces will go along the hypotenuse of the resultant triangle and the downward ball weight will include either a positive or negative element of the towing force.

This will change the effective ‘ball weight’ and depending on the design of the towbar may move the centre of force of the tow bar away from the designed strong points of the connection to the chassis.

Far too complex calculations for my aging memory and brain to prove
AnswerID: 418533

Reply By: Allan B, Sunshine Coast, - Friday, May 28, 2010 at 16:33

Friday, May 28, 2010 at 16:33
Rob,

The towing capacity is determined by assessment of the total forces and strengths of the towbar and its attachments.

The position of the coupling point (ball) determines the rotational force on the assembly due to towing thrust thus it is likely to be different between the upward or downward positions. This force will then influence the towing rating.

Cheers
Allan

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AnswerID: 418560

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