Chassis design is a complex process that requires a good bit of trial and error. The purpose of the chassis is to support all the parts of the robot and allow you to deliver your weapon to the opponent whilst being able to survive the resultant forces that will go back through your robot. The requirements of a flipper differ to a crusher or spinner.
This is still a viable technique to build robots however there are a number of downsides. The weakest point of your armour are the bolts holding it on. You could weld the panels on but then this means that you are wasting weight with the box section chassis. It can also take a great deal longer to create a box chassis and then cut all the panels for it.
Formula one cars used to use the same manufacturing technique however they moved to a monocoque design. So have modern robots. A monocoque means that your armour and chassis are one and the same.
The majority of modern robots use a monocoque or bulkhead system of some variety with every robot that made it to the final 6 of Robot Wars 2016 using the techniques. We would therefore recommend incorporating it into your own designs.
It's very useful for making internal brackets for the robot. We wouldn't advise using it for armour though as there are far better materials available for not much more in price.
If you do a quick google search chances are you will find a number of suppliers relatively close to you and the majority will deliver. We'd always advise getting a few quotations as prices can vary between suppliers. We would also recommend giving any exposed mild steel a quick spray with some WD40 and a wipe down with a rag as even if it is stored inside in the garage or shed as it will gradually form surface rust.
Hardox is the standard go to of these materials. It is actually a trade name of the Swedish company SSAB and so other companies have equivalent products such as RAEX. Weldox is a material from SSAB which as it's name suggests is better for welding. In actual fact it is merely better at retaining it's properties during heavy welding processes. Essentially all the wear plate materials begin to lose the material properties when subjected to high amounts of heat. It is also not available in the same thin sheets thicknesses that hardox is available in. Typical armour on a heavyweight is anywhere from 3mm to 10mm depending on the location on the robot.
Armox is the military grade equivalent that is used in armour for military vehicles. Due to this it is far more expensive and more difficult to get a hold of than hardox and weldox. It rarely makes sense to use it.
When ordering hardox you will see a number appear in the description. This will be 400, 450, 500 or 600. This refers to the brinell hardness of the material. We'd recommend having a read up on this property via google to properly understand it but essentially the higher the number, the harder the material. All grades of hardox will stand up to the majority of robot applications. The higher grades are far more difficult to machine and are typically not available in the thinner thicknesses that we require.
When it comes to machining hardox, it can be welded with stick arc, TIG and MIG using standard filler material as you would with mild steel. Cutting and shaping can be carried out with an angle grinder with a disc suitable for ferrous material. Drilling can get a little more difficult. We would recommend using either cobalt drill bits or bosch all purpose drill bits. Best to use a pillar drill with as slow a speed as possible. All of the wear plate materials can be laser cut, water cut and plasma cut. We used a mixture of laser and plasma cutting in PP3D. We will discuss manufacturing in more detail in a future post.
There are a number of grades of titanium. The most useful to us is grade 5 titanium. This is the grade that the majority of titanium is manufactured in worldwide. It has great strength characteristics and is well suited to armour applications.
It can and has been used for armour in the past but sourcing it without breaking the bank can be a real issue!
Machining it is an interesting affair. You can use an angle grinder to cut and shape but just be aware that the sparks are hotter and will set materials on fire more readily. We have in the past had titanium fires from excess material when turning it on a lathe. The only thing you can really do is to walk away as a titanium fire creates it's own oxygen and will keep burning intensely. When drilling use sharp HSS bits and flood the area with coolant. Titanium tends to gum up when drilling if your drill bits aren't sharp. If you want to tap a thread into it, use a high quality spiral tap. Otherwise you will likely snap the tap. We will discuss this further in a future post and how it nearly ruined our chances of getting on Robot Wars!
Aluminium can be found in a large number of grades. Some are easier to machine, others are easier to weld and some are stronger than others. We would recommend researching the various grades before purchasing.
In PP3D we used aluminium in the custom bearing block housings that we machined up to support the disc shaft.
It can be machined with a wide range of hand tools and is very easy to drill, turn and mill. It can be welded but you will need special equipment to do so. Aluminium can be tapped and will hold a thread which makes it easy to use bolts in the internal construction of a robot.
Nylon has been used successfully in featherweight robots for years however it has still to be fully proven in a heavyweight robot. We wouldn't recommend it for armour.
This was the material that Gabriel was made from in the recent series of Robot Wars.
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