Thread: drilling holes in the chassis

Originally Posted by TimNZ

The programe is Autodesk Inventor, unfortunatly not free, but I have access to the software at work.

Cheers,

Tim

nice one. With the example you gave, where/how was the force applied?

could you run a 75mm(w)x200mm(h)x2mm(t) box section with a 65mm hole through the middle of both webs, with a tube of same dia joining them.

can you apply torsional force?

What real advantage would you get from drilling some holes? How much flushing out of the chassis do you really think you need? I've seen fifty year old chassis that have plenty of dirt in them that are still solid.

Originally Posted by uninformed

John, does that testing that LR did/do include the regular cracking in the rear of 130 chassis...

Possibly - but it is likely that they limited loads to what was in the manual, and did not use typical corrugated roads.

But, seriously, they would have calculated the effect of any holes or similar stress risers before incorporating them in production. This is easy. Calculating, and even testing, the actual loads imposed on the chassis in real life is much more difficult, if not impossible. There are too many variables, that the manufacturer has no control over. Consider the bending load imposed by the tray load on the rear section of the chassis. Obviously, this depends on the load in the tray. And almost as obviously, it depends on the rate at which the wheel is deflected by a bump. But less obviously, it depends on the distribution of load in the tray, the tyre pressure, the type of tyre, the damping effect of the shock absorber (which will change with temperature), whether the shock absorber reaches the maximum extension, whether the load is restrained to stop it lifting off the tray and then impacting the tray (which in turn depends on how solid the load is - for example, sand versus, say a solid metal load such as an engine). The manufacturer will not attempt to analyse all these, but will simply apply a safety factor to the expected load - and then perhaps modify the design in a few years time if there are enough failures!

John

Okay, been following this thread just waiting, but the issue hasn't been raised.
Many people recommend the extra hole in the top and bottom of the chassis rails for fitting the ARB steel bar to a D2, however I always thought that chassis drilling, particularly top and bottom was a big no-no.
So can someone say conclusively that it shouldn't be done?
It's listed as SOP in the ARB fitting instructions.
Cheers
Muppet

Originally Posted by uninformed

can an engineer here tell me why a 12mm dia hole in the middle of the 75mm wide chassis bottom flange would be an issue? Isnt there already some there.

I'm certainly no engineer but
Yes there is one 12mm hole in the middle of the vehicle, say around B pillar. There is also a 8mm hole just before it sweeps up into the engine bay. That is all for the button of the chassis however. My problem is the fuel tanks block the holes in the side of the chassis on the outer side that I once used to put water through.

I was thinking of making the 8mm into a 12mm. And towards the rear, on the underside of the upward sweep place another 12mm. But this doesn't sound to be a good idea.

Oddley enough when I mounted the fuel pump I drilled two 4.5mm holes in the middle of the side wall of the outer chassis and didn't even stop to think. I'd imagine Dan from Mulgo would do the same buy cant say for sure.

I'd say the frame is mild steel, my car stands dinted the under side easily when I din't use wood as a spacer, and I have a few good dints from rocks as well.

Originally Posted by Disco Muppet

Okay, been following this thread just waiting, but the issue hasn't been raised.
Many people recommend the extra hole in the top and bottom of the chassis rails for fitting the ARB steel bar to a D2, however I always thought that chassis drilling, particularly top and bottom was a big no-no.
So can someone say conclusively that it shouldn't be done?
It's listed as SOP in the ARB fitting instructions.
Cheers
Muppet

Fitting a bar is done at either end of the chassis. There are no significant bending loads there to stress the top/bottom flanges. Drill away, but do fit crush tubes.

Originally Posted by stealth

What real advantage would you get from drilling some holes? How much flushing out of the chassis do you really think you need? I've seen fifty year old chassis that have plenty of dirt in them that are still solid.

Depends on how much you use the vehicle and where. Chassis with a good layer of mud through it will rot away reasonably quickly if it keeps getting wet or damp. Sand is no big deal as long as the salt is gone.
I also would like to put some fish oil or similar through the middle of it. A bit of prevention now could be well worth the effort if I could get better access.

Uninformed, is this what you are after? In both examples the left hand face is "fixed" and the right hand face has a downwards force, (indicated by the arrows), applied.

400mm Section



1000mm Section



Cheers,

Tim