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Old 05-07-10, 11:26 AM   #1
v12trikes
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Default 6 Wheel Drawbar Trailer

Hi, i am thinking of building a 4 wheel drawbar trailer , what concerns me is the type of braking to use ie cable or hydralics, any advice welcome
regards Don v12 trikes.
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Old 05-07-10, 11:28 AM   #2
martinpaff
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Don

My commercial 4-wheel trailer, based on an ALKO chassis, uses cable operated brakes, which work just fine. I suspect cable brakes are much easier to set up.

Martin.
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Old 05-07-10, 11:43 AM   #3
v12trikes
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Hi, just to clarify is your trailer a 4 wheel with turntable and drawbar, if it is
any info on the cable layout through the turntable very welcombe
regards Don v12 trikes.
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Old 05-07-10, 11:56 AM   #4
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Ah, now I understand...

No, mine is a simple 4-wheeled trailer.

As a matter of interest, why would you want to build an articulated (not sure of the correct term - articulated? close-coupled? drawbar? etc?) trailer? It sounds like a lot of complication, and I'm not sure what you gain.

We use a great many different pieces of equipment based on these types of trolleys, and the few that are braked use cable brakes. We tend to have them because the equipment is: very large, very heavy, and they are easy to uncouple from the tug. I call them trolleys because they tend to have small wheels (like Peter's Ruston trolley) which are unsuitable for road speeds.

One piece of equipment that I am quite familiar with, uses a standard over-run brake on the tow-bar, but the ballance bar (which converts the movement to cables) is mounted on the draw-bar. Cables then run beneath the (Ackermann) steering, to the rear wheels only.

Martin.
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Old 05-07-10, 12:23 PM   #5
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I've been sitting and pondering some of the advantages and disadvantages of the various layouts...

Everybody whose built a trolley for an engine will be familiar with the problems of a turntable:

1. As the steering turns the trolley becomes unstable at the front, because the effective track narrows.

2. The wheels have to be able to pass below the chassis to get any usefull amount of lock.

Ackermann gets round both of these problems, but unless the front and rear wheels are fairly close, the steering lock can be limited. We frequently see equipment with a bent or broken draw-bar because the lock has been exceeded.

Ackermann geometry could be fun to design, but everything you need to know is on the net. Any slack at all in the system makes the trailer "fish-tail".

Reversing a close-coupled trailer can be an interesting challenge...

Because the drawbar needs to be quite long and quite wide, there is plenty of room on the underside to mount the cable balance bars. I see absolutely no reason why all four wheels shouldn't be braked. I would think the cables could simply pass underneath the pivot point, in a relatively loose loop, and they would work fine. The balance bars would always make appropriate compensation for the cables flexing.

Just random thoughts...

Martin.
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Old 05-07-10, 04:08 PM   #6
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Hi, stability would depend opon the dia of your fifth wheel ie the turntable, the main advantage of this type of trailer is that balance front to rear would not be so critical, reversing is easy you just fit a hitch on the front of your motor. regards Don v12 trikes.
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Old 05-07-10, 04:15 PM   #7
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Hi, another thought just come to mind, you need hieght for the front axle to swing under the chassis, the front of the trailer could be a swan neck, giving you a step frame trailer, handy maybe bits and bob's on the front engine's on the lower main body, regards Don v12 trikes.
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Old 05-07-10, 04:53 PM   #8
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Quote:
Originally Posted by v12trikes View Post
Hi, stability would depend opon the dia of your fifth wheel ie the turntable, the main advantage of this type of trailer is that balance front to rear would not be so critical, reversing is easy you just fit a hitch on the front of your motor. regards Don v12 trikes.
No, the turntable only has any real influence when the steering is straight. As the steering turns the wheels progressively get closer laterally, and the front of the trailer becomes increasing unstable. If you turn the steering to 90 degrees the front wheels provide no stability and only the rear wheels are keeping the whole plot upright. This is the reason that virtually all of ours Ackermann.

Martin.
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Old 05-07-10, 05:14 PM   #9
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Quite common in Europe on small vans, we saw a 6-wheeler while travelling to Nuenen, being pulled by an SUV.

I'd like to have a go too, we would maybe like to make up a combined sleeper room and engine trailer for the Ruston, so the question of camping accomodation doesn't become a hassle.

we can have 3.5 tonnes behind us in the Disco, the Renaults are too small at 2 tonnes max trailer and load weight.

I reckon we could get something in about 18ft body length, but you have to watch for the overall train length which is 18M, not too difficult to keep inside that!

The biggest question is always, as Martin and others have pointed out, the steering and braking.

Firstly, turntable is the simplest, and for most folks probably the easiest if you're going to build your own.

Braking and suspension then rear their ugly head, and you cannot use Indespension units that easily with a turntable or Ackerman steering as they are trailing arm. You CAN use them, it's just more difficult.

A long drawbar gets round the sensitivity issue.

We would need effectively a 2-berth caravan and trailer rolled into one, a shower would be a MUST!

Peter
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