Weight Transfer - What is it, how does it work and, most importantly, when should and shouldn’t we use it?
Many operators of ride-on turfcare products are likely to be familiar with the term, weight transfer. But, have we all managed to make enough time to understand it in depth?
Weight transfer applies to many devices, but for the purposes of this article we are considering, predominantly, turf and agricultural machinery. It is simply the ability to take advantage of the weight in one part of a machine and move it to another more advantageous part of the machine to aid performance, usually in the form of increased traction and stability.
In the industrialised world, farm tractors offer some of the best examples of machines which have an adjustable, operator or automatically controlled, weight transfer system combined with a three-point hitch to improve traction. Sometimes referred to as draft control, but also originally known as “The Ferguson System” with several associated patents filed by Harry Ferguson in the 1930s. It utilised what’s known as a flow on demand hydraulic circuit that “tries” to lift the mounted implement to transfer weight from the mounted implement to the rear wheels of the tractor, dependent on the draught being pulled. This aids traction. A spring-operated weight transfer system was also patented by Ferguson as early as 1921 before the common use of hydraulics (credit The Friends of Ferguson Heritage Ltd).
Commercial mowers
These principles have since been integrated into many types of products, including commercial Outdoor Power Equipment (OPE). Most golf and commercial ride-on mowers have some kind of adjustable weight transfer system. There is either a heavy-duty spring or springs which can be manually adjusted to pull on the lift system, trying to lift the mower off the ground. This simple but effective idea transfers weight from the lift arms to the traction unit and is adjustable, either on the go or by pre-determined manual settings. In a hydraulic system, valves can be used to create some backpressure in the lift cylinders, enough to try and lift the mower(s) off the ground but not so much that the mowers are lifted. This transfers weight from the mower(s) to the front wheels (usually) of the traction unit via the lift arm mechanism. There are variations and combinations on this theme, but the principle is the same.
Moving weight increases downforce
The most useful question to address is when should you use weight transfer? With a mowing attachment, the most obvious time is on slopes. Moving weight from the mower(s) to the traction unit increases down force on the wheels closest to the lift point of the implement where it meets the traction unit. This is most effective with a front mounted mower on a front wheel drive traction unit. In this case, the front wheels are now forcibly planted on the ground and obtain more grip which improves traction. It’s advisable to select weight transfer before climbing a slope or any other condition where additional traction might be required as it offers a more progressive influence on the tyres’ grip. By applying downforce on the traction wheels, the centre of gravity of the machine is also being lowered. This has the effect or making it less likely to tip, however, the manufacturer’s declared safe working angle of the machine should never be exceeded. The latter will be stated in the operator’s manual and via decals on the machine. A manufacturer approved Roll Over Protection Structure (ROPS) should also be deployed and not folded if a folding feature is provided. You must also be wearing a seatbelt to ensure you stay within the operator safety zone should the worst happen and the machine rolls. Specific training is available from many suppliers, some providing checklists to remind operators of additional safe practice when operating on slopes.
Dual wheels
The effect of weight transfer can further be enhanced by fitting dual wheels. They can offer even more traction and stability on slopes and, whilst benefitting from the weight transfer, spread the load enough to prevent turf damage.
How much additional down force?
Depending on the system design and implement mass, the percentage of weight that is added to the front wheels of the traction unit can be up to 49%, more than without weight transfer engaged. That’s a significant amount of extra grip available. The geometry of the machine needs to be such that the rear of the machine does not become too light as weight is also being transferred from the rear to the front of the machine. This can usually be mitigated with counterbalance weights and the inherent characteristics of the machine’s design.
In summary, using weight transfer with a front mounted mower(s) and front or all-wheel drive will increase traction on the front tyres of the traction unit. This is most useful whilst operating on slopes because it decreases the potential to slide and lose control of the machine.
Are there conditions when you shouldn’t you use weight transfer?
The short answer is yes. If you are on flat ground or less challenging undulations, it is often best to reduce or eliminate weight transfer. Why? The are several reasons depending on what type of weight transfer system your machine has. When using mowers that have rear rollers, and you want to leave a striped effect after mowing, it’s desirable to increase the weight of the mower being supported by the roller so it has the best chance of leaving a definite stripe. If you are traversing undulations, too much weight transfer can cause the mower to “hang” in the air as it crests an undulation. It will eventually lower, but depending on your forward speed the mower will miss some of the grass to be cut on the lea side of the undulation leaving an uneven height of cut.
Adjusting your weight transfer according to conditions is very desirable, especially if it can be done ‘on the fly’. Some machines have rotary valves, some, more recent, machines have electronically controlled settings, and some have very effective adjustable spring settings. Most, if not all of them can be adjusted ‘on the go’ very quickly, enabling the operator to maintain productivity. It sometimes takes a little practice, but it’s well worth mastering.
About the author
Richard Comely is the PR and Marketing Consultant for Price Turfcare, the UK and Ireland distributor of the Ventrac all-terrain compact tractor. In his early career, he studied agricultural engineering and was employed by Lely and Ariens before he spent 22 years working for Ransomes Jacobsen in various technical roles including Director of Global Product Management, responsible for a team of product development specialists in the USA and UK. In 2020, he joined ETA Green Power Ltd, a leading design and technology development company specialising in high density electric drive systems, initially as Product and Marketing Manager, before retiring in March 2024 as Product Manager for OPE sectors.