Component Fabrication: Aluminium front chassis brace & skidplate

Posted: April 16, 2015 in Component Fabrication
Tags: , , ,

This custom made Aluminium front chassis brace & skidplate is designed for the Team Associated RC18T and is intended to strengthen and protect the front hinge pin mounts and the front gearbox bulkhead. The process of construction can be applied to other projects requiring a similar component. 

The stock front plastic hinge/arm mount works fine until you have a few hard uneven landings or front collision. In my experience I have found that the front hinge hole will crack easily and dislocate the arm hinge pin from the mount. There are aftermarket aluminium front hinge pin/bumper mounts available which are definitely stronger however after testing one on a previous build I found that they are not the best component to use. Through frequent use the stock plastic hinge pin mounting holes create very little wear on the hinge pins themselves when compared to aluminium. Aftermarket aluminium front hinge pin mounts are integrated with the front bumper/skidplate. The downside of this design is that after a hard front collision this component will usually bend and distort the hinge pin geometry and as a result binding or more severely damaging the front suspension arms and or the front chassis.

I have found that by reinforcing  the stock plastic hinge pin mount/bumper and combining this with a custom chassis brace and skidplate to enclose the front bulkhead, the front suspension arm mounts are much stronger and do not crack, and the front chassis is more resilient to impacts as there is rebound flex in this chassis brace to absorb the forces.  In combination to the small amount of flex in the chassis brace, the whole front end assembly is also more rigid as a collective structure reducing the front to rear central flex forces which can affect the transmission.  These components create torsional rigidity down the center line of the chassis preventing front to rear flex which can affect the transmission by binding the solid driveshaft with the front and rear differentials but still allows a small amount of offset lateral chassis twist which I have found to be good for the off-road handling for this particular chassis.

PART 1: MODIFYING STOCK PLASTIC ARM MOUNT

Whenever I make a custom part I always prototype the part by making a template out of cardboard/posterboard. By prototyping you can verify dimensions, test fitment and test the process of making the part in 3D. I match the material thickness of the prototype with the material I intend on using for the custom part. This is very important especially with complex forms as material thickness will have an effect on dimensions drawn in 2D.

Part 1 involves reinforcing the stock plastic hinge pin mounts with a fabricated aluminium collar which is glued in place. Normal cyanoacrylate adhesive ie; superglue, tire glue sometimes does not work very well when joining different materials, especially with nylon based plastics and metals. Loctite 480 is used because of its ability to bond difficult materials. The composition of this adhesive contains rubber chemicals which bonds very well with nylon based plastics and metals. It is also not as brittle as normal ‘clear’ cyanoacrylate adhesives.

Parts & Materials Used:

x1 Team Asscociated 18T F&R Arm Mount – #ASC21005
0.032″ thick 6061 aluminium sheet
0.25 – 0.5mm posterboard
Painters masking tape
Loctite 480 – ‘Black’ toughened cyanoacrylate instant adhesive
Silicone Carbide abrasive paper (various grit)
Polishing compounds

PART 2: ALUMINIUM FRONT CHASSIS BRACE

This component is designed to function as a chassis brace to enclose and strengthen the modified front hinge pin mount/bumper with the front gearbox bulkhead.

This component creates torsional rigidity and strength with the chassis center line and transmission assemblies.

Parts & Materials Used:

0.032″ thick 6061 aluminium sheet
0.1mm posterboard
Painters masking tape
Silicone Carbide abrasive paper (various grit)
Polishing compounds

PART 3: ALUMINIUM FRONT SKIDPLATE

This component is designed to function as a front skidplate to protect and reinforce the chassis brace.

On previously fabricated versions of this aluminium chassis brace, the function of the skidplate was combined with the brace as one component. The problem with this was that most of the damage from road contact occurred on the bottom lip and bottom surface of the brace, as a result the chassis brace would wear out prematurely weakening the structure. As a result I would have to fabricate a new one which is quite time consuming. This separate skidplate is designed to reinforce the chassis brace and  be replaceable when overly damaged. It is much easier to fabricate this skidplate rather than a complete chassis brace.

Parts & Materials Used:

0.032″ thick 6061 aluminium sheet
0.1mm posterboard
Painters masking tape
Silicone Carbide abrasive paper (various grit)
Polishing compounds

PART 4: ALUMINIUM CLAMPING SUPPORT MOUNT/BRACE

This component is designed to function as a clamping support mount/brace to clamp the chassis brace and skidplate to the stock plastic chassis and to structurally support the front gearbox assembly.

This small component is integral to the structural strength of these combined components working with the chassis. In extreme impacts, this section of the chassis is prone to snapping and separation of the front bulkhead from the rest of the chassis. This custom aluminium clamping support is designed to strengthen this area and transfer and spread the impact force through the body of the chassis.

Parts & Materials Used:

0.032″ thick 6061 aluminium sheet
0.1mm posterboard
Painters masking tape
Silicone Carbide abrasive paper (various grit)
Polishing compounds

PART 5: ASSEMBLY

The assembly procedure shown here may differ slightly to the final assembly procedure of the whole car as other components need to be installed. In final assembly medium ‘blue ‘threadlock is used.

Parts & Materials Used:

Part 1: Modified stock plastic arm mount
Part 2: Aluminium front chassis brace
Part 3: Aluminium front skidplate
Part 4: Aluminium clamping support mount/brace
x2 3Racing titanium countersunk hex screws (M2 x 6mm)
x2 3Racing titanium countersunk hex screws (M2 x 8mm)
x2 3Racing titanium countersunk hex screws (M2 x 10mm)
x2 3Racing titanium buttonhead hex screws (M2 x 8mm)
x4 HD stainless steel hex screws (M2 x 15mm)
x4 Annsmann anodised aluminium nylock nuts (M2)
x2 GPM anodised aluminium countersunk washers (M2)
Polishing compounds

Thank you for checking out this article. I hope it helps readers with some ideas on their next build. If you have questions or need some advice on a particular stage feel free to write a comment below and I will answer them.

Cheers. RC-Christo.

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