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Trailer Draw bar length

General Tech Talk

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Trailer Draw bar length

Post by jlmac »

Hi Guys

I want to increase the draw bar length on my trailer.
1.8 meters seems to be what quite a few people are using.
My question is, where is the length measured from. 1) The spring hanger to the coupling or 2) the front of the tray to the coupling?

Cheers
Justin
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Post by droopypete »

The dimension is irrelevant, it is a question of balance,
single, double or triple axle?, where the weight is positioned?, there are heaps of factors that need to be considered or it will be a pig.
Peter.
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Post by jlmac »

More information.

Trailer is a 6x4 unit with a fold out canvas tent on top(the same as most camping trailers). Single axle.
Only new additions will be a 65L water tank which will go underneath at the back, a large style tool box on the draw bar and the spare tyre also on the draw bar.
The trailer has no kitchen or anything fancy at all, weight positioning will be determined by how well I pack the trailer :)

Cheers
Justin
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Post by Spimon_NH »

*edit*
Whoops. I completely missed your question. No, I have no idea. Maybe go
check out a trailer shop with ur tape measure :?
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Post by dieseldude »

The 7 x 4 box camper trailer which I'm currently making has a drawbar length of 1900mm from the front edge of the box.

As said before - it depends on how it is going to be balanced. With my set up (where the axle is positioned under the trailer), I have a drawbar weight which I can lift myself - but it's still heavy enough to stop the rear of the vehicle bouncing.....

I reckon a length of around 1800mm on a 6 x 4 camper would be fine though...

Anthony
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Post by Toy80Diesel »

You need to have at least 10% ball-weight for the trailer to tow properly. If you increase the drawbar length, this decreases ball-weight. Then what you add onto the drawbar will obviously increase it again. If the ball-weight is too light (under 10%) it will cause the rear of the vehicle to bounce everytime the trailer wheels hit a bump in the road.
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Post by David_S »

And don't forget that the longer the drawbar the easier it is to reverse.

And I would measure its length from the ball to the axle, the axle being the fulcrum about which the unit pivots when you lift the ball.
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Post by droopypete »

David_S wrote:And don't forget that the longer the drawbar the easier it is to reverse.

And I would measure its length from the ball to the axle, the axle being the fulcrum about which the unit pivots when you lift the ball.
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Cable bracing is the way of the future!

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Post by droopypete »

jlmac wrote:More information.

Trailer is a 6x4 unit with a fold out canvas tent on top(the same as most camping trailers). Single axle.
Only new additions will be a 65L water tank which will go underneath at the back, a large style tool box on the draw bar and the spare tyre also on the draw bar.
The trailer has no kitchen or anything fancy at all, weight positioning will be determined by how well I pack the trailer :)

Cheers
I don't completely understand the purpose of your thread, if you have a trailer you are happy with, leave it alone. if you want it longer, lengthen it, where you measure it from makes no difference.

I have 3 6'x4' trailers with draw bars ranging from about 2m to 3.5m and loaded properly they all tow great (the long one is my fav)

My only advice is to make it as long as possible, you can back mine at speed with confidence and carry loads up to 5m long.
Good luck.
Peter.
Cable bracing is the way of the future!

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Post by jlmac »

Peter, The reason for lenghting the draw bar is to make it tow/reverse better. I have heard quite a few people use 1.8m draw bars and I was not quite sure where the measurement was taken from, hence my first question.
Now than I have a better understanding off how it all works I will make the draw bars 2.45m long as measured from the spring hangers. This will make it 1.8m long from the front of the tray.

Cheers
Justin
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Post by Struth »

A good rule of thumb is to ensure that between 10% to 20% of the trailers loaded mass is placed on the tow bar, 15% being the ideal.

This can be acheived best by positioning the axles but is pretty hard to do on a completed trailer.

The longer the drawbar the less the trailer will react to steering when being reversed, the opposite applies for a shorter draw bar.

Cheers
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