A-Frame Specifications and use on AS Roads

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Brad
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A-Frame Specifications and use on AS Roads

Postby Brad » Thu Jun 09, 2011 10:37 pm

Introduction
This section of the Queensland Transport website explains how to undertake "A" frame towing of a
motor vehicle with a Gross Vehicle Mass (GVM) of up to 4.5t in Queensland in a manner that satisfies
the Queensland Road Rules.
"A" frame towing is the term used to refer to towing a motor vehicle which has its front wheels on the
road and is connected to the towbar of the towing vehicle by a triangular shaped frame, commonly
known as an "A" frame.
The Queensland Road Rules state:
294 (1) The driver of a motor vehicle must not tow another motor vehicle unless:
(a) either:
(i) the driver can control the movement of the towed vehicle; or
(ii) the brakes and steering of the towed vehicle are in working order and a person
who is licensed to drive the towed vehicle is sitting in the driver’s seat of the towed
vehicle, and is in control of it’s brakes and steering; and
(b) it is safe to tow the vehicle.
In addition to the section about safe towing, this section provides a guide for both unbraked and
braked "A" frame towing of a light motor vehicle with a GVM of up to 4.5t. Persons wishing to
undertake "A" frame towing may need to seek advice from a Registered Professional Engineer to
ensure that the "A" frame device that is intended for use meets the following technical requirements.
A list of recognised Registered Professional Engineer is available from Queensland Transport
customer service centres.
August 2005 Page 8 of 12
Queensland Transport recommends that a copy of this information, together with any reports,
approvals or other documentation, is carried in the vehicle at all times.
Persons wishing to undertake "A" frame towing of a vehicle in excess of 4.5t GVM need to apply to
Queensland Transport providing a complete submission addressing all relevant aspects of the
proposal for evaluation.
Persons living in other states will need to check with the Road Transport Authority in which their
vehicle is registered to determine individual state requirements for the towing of vehicles with "A"
frames.
Coupling design
The "A" frame coupling must:
• be designed and constructed with sufficient strength to hold the vehicles together in tow and
must comply with the requirements of Australian Design Rule 62/… (Mechanical connections
between vehicles) relevant to the GVM of the towed vehicle;
• permit an adequate amount of angular movement between the towing and towed vehicles, to
cater for road undulations;
• be secured to a substantial body member of the towed vehicle, such as a sub-frame or
chassis member. Connection to the towed vehicle’s bumper, suspension or steering
components is not permitted, unless approved by the manufacturer of the towed vehicle;
• be marked with the manufacturer’s name or trademark and the rated capacity. The
"manufacturer" may include the owner in the case of a privately constructed device; and
• maintain a space between the combination not exceeding 2m.
Safety chains for towed vehicles with a GVM of up to 3500 kg
Towed vehicles with a GVM of up to 3500 kg must be equipped with safety chains/cables complying
with AS 4177.4-1994 of the appropriate size for the towed vehicle GVM as detailed in Table 1 below:
August 2005 Page 9 of 12
Table 1
Towed Vehicle
GVM in kg
Nominal material
size in mm
Chain markings
0 to 1000 6.3 4177-10
Up to 1600 8.0 4177-16
Up to 2500 10.0 4177-25
Up to 3500 13.0 4177-35
The number of chains required depends on the towed vehicle’s GVM as follows:
• Towed vehicles with a GVM up to 2500 kg must be equipped with at least one safety chain.
• Towed vehicles with a GVM over 2500 kg must be equipped with two safety chains. For
towed vehicles with a GVM up to 3500 kg safety chains may be replaced by safety cables with
a certified load capacity not less than that of chains complying with Australian Standard
4177.4 – 1994 “Safety Chains up to 3500 kg”.
Safety chains for towed vehicles with a GVM over 3500 kg
Towed vehicles with a GVM over 3500 kg must have two chains made from steel of a minimum 800
MPa breaking stress and conforming to the mechanical properties of Grade T chain as specified in AS
2321-1979 ‘Short-link chain for lifting purposes (non-calibrated)’. (Refer Table 2).
The size of chain must be as follows:
• Towed vehicles with a GVM over 3500 and up to 4300 kg shall have chains of at least 7.1mm
in size.
• Towed vehicles with a GVM over 4300 and up to 7500 kg shall have chains of at least 9.5mm
in size.
Safety cables (fitted in lieu of safety chains) must comply with and be certified to AS 3569-1989 ‘Steel
wire ropes’. The cable fitted with attachments (i.e. snap hooks and quick link) must be equal to or
larger than that specified in Table 2.
Table 2
Towed Vehicle
GVM in kg
Nominal material
size in mm
Applicable Australian
Standard
0 to 4300 7.1 AS 2321-1979
Over 4300 and up to 7500 9.5 AS 2321-1979
Towing capacity of towing vehicle
Where the vehicle used for towing has a GVM not exceeding 4500 kg, the towing limits specified by
the vehicle manufacturer must not be exceeded. Please note that most manufacturers specify towing
limits for their vehicles in the vehicle handbook.
Where the vehicle used for towing has a GVM over 4500 kg, the manufacturer's Gross Combination
Mass (GCM) must not be exceeded.
The loaded mass of the towed vehicle must not exceed the towing capacity of any component in the
combination, including the "A" frame, towbar and tow ball.
Towed mass ratio
The tare mass of the towing vehicle divided by the laden mass of the towed vehicle (including the "A"
frame) determines the combination’s towed mass ratio (TMR).
TMR = Tare mass of towing vehicle : 1
Laden mass of towed vehicle
August 2005 Page 10 of 12
Braking requirements
Where the towed mass ratio of the combination is not more than 3.5 : 1 (the tare mass of the towing
vehicle is not more than 3.5 times the laden mass of the towed vehicle), the brakes on at least one
axle of the towed vehicle must operate when the driver of the towing vehicle applies the brakes of the
towing vehicle. Please note that it is not acceptable to utilise the park brake of the towed vehicle to
achieve this.
Where the towed mass ratio of the combination exceeds 3.5 : 1 (the tare mass of the towing vehicle is
more than 3.5 times the laden mass of the towed vehicle), there is no requirement for the brakes of
the towed vehicle to be operable. The requirement for a towed mass ratio in excess of 3.5 : 1 is
designed to give a combination adequate braking without the need for the brakes of the towed vehicle
to be operated by the driver of the towing vehicle.
Irrespective of the towed mass ratio, the combination must have a braking performance of at least that
detailed in Table 3.
Table 3
Stopping distance
when brakes applied
at 35 km/h
Average deceleration
rate from any legal
speed
Peak deceleration
rate from any legal
speed
Vehicle combination
gross mass
under 2.5 tonnes
12.5m 3.8m/s2 5.8m/s2
Vehicle combination
gross mass
2.5 tonnes or over
16.5m 2.8m/s2 4.4m/s2
The parking brake of the towing vehicle must be able to hold the combination stationary on a 12%
gradient.
Lighting
The following lamps must be fitted to the rear of the towed vehicle and must be operational whilst
under tow:
• two turn signal lamps showing yellow light to the rear.
• two stop lamps showing red light to the rear.
• two reverse lamps showing white light to the rear.
• one registration plate lamp at the rear of the towed vehicle to illuminate the registration plate.
• two tail lamps showing red light to the rear.
These lamps may be arranged on a portable lamp bar providing it is securely fastened to the rear of
the towed vehicle.
Steering
The "A" frame towing system must provide safe and adequate steering control for both vehicles whilst
being towed in combination. The stability of the combination, the steer-ability of the towed vehicle and
the tracking of the combination must be satisfactorily addressed.
Please note that the steering wheel locking mechanism of the towed vehicle must be placed in the
unlock position when the vehicle is being towed by an "A" frame.
Additionally:
• The combination must be capable of turning within a 25m diameter circle, measured at the
outer wheel track.
• When travelling in a straight line on a level, smooth surface the towed vehicle must track
(follow) in the path of the towing vehicle without deviating off-line by more than 100mm.
• Reversing an “A" frame coupled combination is not recommended due to lack of directional
control over the towed vehicle.
August 2005 Page 11 of 12
Vehicle and towing componentry manufacturer’s requirements
The vehicle manufacturer’s recommendations must be complied with whilst carrying out "A" frame
towing. This applies equally to both the towing and towed vehicle.
Vehicle owners are advised to check with the manufacturer/dealer to determine whether their towed
vehicle is suitable for "A" frame towing. Advice given in the "Owner’s Manual" for the towing of the
vehicle should always be followed.
Queensland Transport recommends obtaining the assistance of a Registered Professional Engineer to
confirm that an "A" frame towing combination and "A" frame coupling apparatus meet the technical
requirements.
Loads in towed vehicle
Carrying a load in the towed vehicle is not forbidden. However, when carrying such a load it is
important to consider the following points:
• The loaded mass of the towed vehicle must not exceed the capacity of any component in the
combination.
• The loaded mass of the vehicle must not conflict with the Towed Mass Ratio (TMR) calculation
as originally determined when assessing braking requirements of the combination.
• Any load carried in the towed vehicle should be placed as low and as centrally as possible.
Large, heavy items (for example, outboard motors) carried high up and behind the rear axle of
the towed vehicle will adversely affect the handling of the combination and may render towing
unsafe.
Other requirements
• The overall length of the combination must not exceed 19.0m.
• The "A" frame, and any attachment which could constitute a dangerous projection, must be
removed from the towed vehicle before it is driven on public roads.
• Both the towing and the towed vehicle must be legally registered.
• Both vehicles in the combination must meet registration requirements and be roadworthy.
• The coupling and towbar must not obscure the number plate or lights on the rear of the towing
vehicle when the towed vehicle is not attached.
• Regulations prohibit towing more than one vehicle or trailer at once.
• Nobody is allowed to ride in the towed vehicle.
• The maximum speed at which towing is permitted is the posted speed limit.
• Following distances outside built-up areas - On roads outside a built up area that do not have
more than one lane in the direction you are driving, there are specific minimum following
distances for long vehicles. If your vehicle or combination is 7.5m long or longer (including
any load), you may not follow closer than 200m to another vehicle or combination 7.5m long or
longer in front of you. The exception is when you are overtaking.
• Stopping on carriageways - If your vehicle or combination is longer than 7.5m or has a total
mass of more than 4.5t you may not:
o stop on a carriageway in a built up area for longer than one hour unless engaged in picking
up or setting down goods; or
o stop on a carriageway outside a built up area except on a hard shoulder or in a truck bay or
other area set aside for parking of goods vehicles.

http://www.tmr.qld.gov.au/~/media/a2570893-dd8b-4446-8ca1-a43bcd5caf57/safe_towing_information_v2.pdf
Brad
Meyers Manx Australia
www.meyersmanx.com.au
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dbryar
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Re: A-Frame Specifications and use on AS Roads

Postby dbryar » Fri Jun 10, 2011 8:14 pm

Good info.

From what I can tell, an A-frame on a buggy can be made by the onwer, attached to the subframe off/beyond the hammerhead, be no more than 2m in length, and requires a safety chain with 10mm wire size. That seems to be the main points unless I skipped over something.
User avatar
Brad
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Re: A-Frame Specifications and use on AS Roads

Postby Brad » Fri Jun 10, 2011 10:35 pm

dbryar wrote:Good info.

From what I can tell, an A-frame on a buggy can be made by the onwer, attached to the subframe off/beyond the hammerhead, be no more than 2m in length, and requires a safety chain with 10mm wire size. That seems to be the main points unless I skipped over something.


Correct and in most cases you won't need to hook up the brakes unless you have a small tow car or you buggy weighs as much as Ben's Iguana :roll:
Brad

Meyers Manx Australia

www.meyersmanx.com.au

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