MySwag.org The Off-road Camper Trailer Forum

General => General Discussion => Topic started by: Throbbinhood on February 19, 2020, 01:18:59 PM

Title: Leverage
Post by: Throbbinhood on February 19, 2020, 01:18:59 PM

Is there a formula or calculator to work out how much a different length hitch will affect my down ball weight/leverage?

I have a gq patrol with jayco Swan ob. Wanted a slightly longer hitch so I could setup the camper without u hitching for quick overnight stops, but the front bed hits the spare wheel.

Title: Re: Leverage
Post by: KeithB on February 19, 2020, 02:54:02 PM

Are you talking a longer drawbar on the trailer or a longer gooseneck on the towbar?
Keith

Title: Re: Leverage
Post by: Throbbinhood on February 19, 2020, 04:15:33 PM

A longer gooseneck on the towbar

Title: Re: Leverage
Post by: KeithB on February 19, 2020, 04:37:14 PM

There are a couple of issues that maybe you need to look at.
Putting on a longer gooseneck may place excessive strain on the tow bar. It will also reduce the stability of the rig if the distance from the rear axle to the towball (overhang) is more than about half the length of the wheelbase of the tow. A lot of people like Landrovers for towing because the overhang is only about one third of the wheelbase.
If the trailer is very light and the tongue weight quite low, you might be okay. But I don't think it's a great idea.
Good luck with finding a solution.
Keith

Title: Re: Leverage
Post by: tryagain on February 19, 2020, 06:51:50 PM

Basically divide the drawbar weight by the current distace between the centre of the tow ball and the centre of the axle and then multiply that by what the new distace between the centre of the tow ball and the centre of the axle.

Title: Re: Leverage
Post by: CTL on February 20, 2020, 11:00:34 AM

Current distance between axle and tow ball divided by the new distance, multiplied by the standard ball weight rating.

Example for a 350kg rated tow bar with the ball pushed away from the axle an extra 200mm - 1377/1577 x 350 = 305.6kg.  So now the max weight your tow ball can legally carry is 305.6kg.

Title: Re: Leverage
Post by: Throbbinhood on February 20, 2020, 01:14:18 PM

Perfect guys, just what I was after.

So. Assuming I'm still within that limit, should be ok?

Im only wanting an extra 20mm I think will be enough.

Title: Re: Leverage
Post by: Pete79 on February 20, 2020, 02:50:39 PM

You’ll find there’s way more then 20mm variation in off the shelf hitches these days.

For example my factory hitch is 185mm from center of pin to center of ball.
But my Repco height adjustable hitch is 305mm from center of pin to center of ball.

Title: Re: Leverage
Post by: Throbbinhood on February 20, 2020, 03:15:56 PM

Wow significant difference! I'll get my measurements and might do some shopping around! I suppose changing hitch could also affect things so will probably sort that first.

Using a regular treg and it's a pain.

Title: Re: Leverage
Post by: Pete79 on February 20, 2020, 07:03:57 PM

To Clarify, just in case;
When I wrote 'hitch' I was talking about the towbar hitch, not the trailer coupling (sometimes called a hitch).

My height adjustable hitch is a Repco branded one of these, and will probably solve your issues by the sound of it.
https://www.campsmart.net.au/adjustable-towbar-hitch-3500kgs (https://www.campsmart.net.au/adjustable-towbar-hitch-3500kgs)

(https://www.campsmart.net.au/assets/alt_2/LM40503.jpg?1503901688)