Horsebox Aluminium

Introduction to aluminium in horsebox manufacture

I will start by saying that aluminium is an excellent product when used correctly for certain areas of horsebox manufacture.

This is not a post to dissuade customers from it; rather, it aims to dispel some of the myths and highlight what can and does go wrong with many horsebox builds. It also raises some questions you may want to ask before spending your hard-earned money.

Properties of aluminium

Aluminium is a versatile metal known for its unique combination of properties. It has a low density, approximately one-third that of steel, making it one of the lightest engineering metals available. This characteristic is particularly beneficial in applications requiring weight reduction.

Aluminium is undoubtedly an impressive material that has become increasingly favoured by mass-market vehicle manufacturers. Over the past 40 years, extensive research and development have led to a continuous rise in the use of automotive aluminium, making it the second most utilized material in vehicle manufacturing, after steel.

Major vehicle manufacturers are at the forefront of this technology, having invested significantly in its development and application. When referring to these manufacturers, I mean those producing millions of vehicles worldwide, equipped with substantial research budgets. They have developed processes and products that enhance aluminium’s use, alongside rigorous testing procedures for strength and lifespan.

Challenges in the equine community

Conversely, in the equine community, where concerns about overweight horseboxes prevail, aluminium has emerged as a compelling sales tool.

However, research into its application for horseboxes is comparatively minimal, with many manufacturers simply copying what others have done and repeating the same construction mistakes. Where used correctly, aluminium is a great product and is excellent for external bodywork, including doors and cappings, where it has been successfully utilized for many decades.

Unlike mass-market vehicle manufacturers who use the latest adhesive technologies to manufacture long-lasting aluminium parts, horsebox manufacturers tend to rely on mechanical fixings like bolts and rivets.

Consequently, where aluminium is used in structural areas such as subframes, plank floors, or ramps, flexing will inevitably cause damage. This damage is usually evident around welds, joints, rivets, or bolts.

Limitations of aluminium

What I am really saying is that aluminium is not a cure-all product for the manufacture of lightweight horseboxes. For all its positive attributes, it also has some significant weaknesses that customers should be aware of:

• Where aluminium is used in horseboxes, its failing tends to be that it does not ‘play well’ with other metals and can rot at a much-accelerated pace when used incorrectly.
• It requires extensive knowledge and processes to be used structurally.
• Although relatively cheap to buy, it adds considerable cost to manufacture with durability and longevity.
• Section sizes need to be considerably larger for the same strength as steel or stainless steel. All designs optimised for aluminium need to be manufactured using sections up to 40% larger than the steel equivalent.
• Sadly, it has become a sales hook to convince customers that it lasts indefinitely, with the hope being that any structural failure occurs outside the warranty period.

By understanding these points, you can make a more informed decision regarding aluminium’s role in horsebox manufacture.

Example

Over the years, I have undertaken numerous repairs on purportedly lightweight horseboxes. Invariably, the damage stems from either flexing or poor construction techniques, leading to accelerated galvanic corrosion and joint fractures.

Recently, I was tasked with repairing an ‘all aluminium horsebox ramp’ that was nearly two years old. In this case the horsebox had exceeded its warranty period by many months, leaving the customer responsible for repairs. This prompted me to pen this cautionary piece and provide some context regarding its proper usage.

Upon inspection, it became evident that the ramp was not, in fact, “all aluminium” as advertised. It incorporated various steel components, including the hinges. The ramp had succumbed to failure due to cracked corner joints from flexing, and more alarmingly, corrosion around the steel ramp hinges where they were fixed to the aluminium frame. As is often the case, the devil lies in the details, and the critical oversight in this horsebox ramp’s design was either a lack of engineering knowledge or cost-cutting measures. The joints were simply welded allowing for no flexing and absence of proper barriers between the aluminium and bare steel ramp components had allowed galvanic corrosion to proliferate unchecked, ultimately causing the ramp’s failure.

Galvanic corrosion

Being that galvanic corrosion was one of the root causes of this ramp failure; I will take a moment to talk about it. In simplified terms, galvanic corrosion is an electrochemical process in which one metal corrodes at an accelerated pace when two differing metals are directly touching. Over the years this issue accounts for much of the damage I have seen. In most cases it would have been avoided with extra time spent fitting a simple barrier between the two dissimilar metals (aluminium and steel).

Issues

The problem with the ramp in question was poor design. It was made from standard aluminium box sections. In essence, it was a steel ramp design made in aluminium! Every joint was welded rigid and all had signs of metal fatigue and cracking caused by flexing. The welding of these joints allowed for no flexing whatsoever and was a serious design flaw. Horsebox ramps are rarely on even ground and flexing is a big part of daily use.

• The barrier separating the two dissimilar metals (aluminium and steel) was not total and, in most areas, non-existent. There was in fact, only paint on the outer surfaces of some steel parts and most were bare steel directly bolted to the aluminium ramp frame. In essence, the advertised sales hook of ‘All Aluminium Ramp’ had many mild steel parts including hinges and spring mounts bolted to the aluminium frame. The lack of a barrier between the dissimilar metals had caused severe galvanic corrosion of the aluminium box section, causing a catastrophic failure of the two spring mounts. Alarming, when you consider one ramp spring can have up to 6 tonnes of compression when the ramp is open!

• Another issue was that the zinc plated nuts, bolts and washers fixing the steel and aluminium together (again dissimilar metals) also had no barrier between them and had contributed to further galvanic corrosion. This is common and something I also see on HGV subframes manufactured in aluminium.

Other issues

Other aluminium failures on this horsebox were the common mistakes I see all too often. It had been fully completed and then sent somewhere else for paint! Many of the aluminium parts, especially where they had been cut, had started the oxidation (rusting) process before being painted. It suffered from poor preparation, poor sealing, and road spray contamination before painting. This presented as bubbling with white oxidation powder on the corners of doors, frames and around all external rivets and bolts. Sheets of paint were peeling away from large areas of the aluminium skirts and ramp.

Sadly, corrosion was a theme running throughout this entire horsebox body and even the aluminium plank floor had corroded and cracked around the dissimilar zinc plated rivets holding it down. Unfortunately, this is the most common horse floor issue I have seen. To tick the “aluminium horse floor” box for sales, and at the same time build as cheaply as possible, aluminium planks are riveted with zinc rivets directly to steel or aluminium bearers!

Conclusion

This experience serves as a crucial lesson: investing time in thorough research and scrutiny when selecting a horsebox manufacturer can prevent costly repairs and ensure you choose a quality product. It highlights what can and does happen on a regular basis, serving as a stark reminder of the importance of looking beyond marketing claims and delving into the specifics of construction and materials used.

From conversations with customers, it is unfortunate that much of the information provided about aluminium in horsebox manufacture tends to be sales-driven with little basis in fact. While aluminium is undoubtedly a lightweight material beneficial in many specific areas, it is important to note that for horsebox manufacture:

• It does not always provide long-lasting durability
• Thicker, taller sections are often required to match the structural strength of steel or stainless steel
• Designs must be specific to aluminium and allow for a significant degree of flex
• Barriers must be used where aluminium touches other metals, including nuts, bolts, and washers

Ultimately, choosing the right horsebox is not just about weight and cost; it is about durability, safety, and quality. By prioritising these factors over marketing hype, you can make an informed decision that will serve you and your horses well for years to come.