Thread: drilling holes in the chassis

G'day I would strongly recommend you DONT drill holes in chassis as this will alter the integrity of the chassis and may cause fatigue to chassis. Have seen this with a Trailer drawer bar which had a few holes drilled in it to hold a metal box

When modifying heavy truck chassis, holes are never drilled in the flanges (the top and bottom) only in the web (the sides).

How thick is the metal in LR chassis? You may have difficulty in drilling round holes in thin metal. Most non-fitters do. You end up with irregular shaped holes because the whole lengths of the drills cutting edges are not cutting at break-through.

My RRC chassis has drain holes underneath. But as the others said, don't go drilling the upper and lower surfaces of any chassis unless you know exactly what you are doing.

I was once working with a Qld Transport inspector and watched him ground an F series pickup for having a minor chassis modification. Major safety defect he said. Any changes that you make need an engineers cert and mod plate and most are only willing to sign off if it is stronger than it was when it left the factory. I wouldn't do it myself. Then again, you would have to get unlucky to get found out - ie vehicles involved in major crashes are scruitinized with a fine tooth comb.

As indicated above - do not drill holes in the top or bottom of the chassis rails unless it is certified by an engineer - which won't happen, at least anywhere between the front and rear spring mounts.

John

Originally Posted by Brian Hjelm

When modifying heavy truck chassis, holes are never drilled in the flanges (the top and bottom) only in the web (the sides)

Is this principle applicable to a box section such as the LR chassis? Heavy truck sections to my knowledge are all C-section.
Another difficulty with drilling the top or bottom of a LR chassis is that they have two layers with a horrible lap weld, as the chassis is constructed from 2 C-sections of different dimensions welded together.

Originally Posted by POD

Is this principle applicable to a box section such as the LR chassis? Heavy truck sections to my knowledge are all C-section.
Another difficulty with drilling the top or bottom of a LR chassis is that they have two layers with a horrible lap weld, as the chassis is constructed from 2 C-sections of different dimensions welded together.

Yes it still applies. The highest stress is found in the top and bottom flanges. This is why you need to know exactly what you are doing before cutting, welding or drilling the flanges.
It's best, where possible, to make all attachments to the vertical webs close to the centre.

hmm.... well it looks like ear plugs in, safety goggs on, and under I go. Mulgo sill tanks are very good, but cleaning inside the chassis is one down side to them.

thanks all for the comment