Thread: Meet my 90, and share the adventure.

Originally Posted by Pickles2

Thanks.
I've seen the steel solution, I don't know whether it's fitted yet, but mudflaps should "give",...if that one fouled anything, or even if there was no "give" in the wind/slipstream, something/mounts would be under pressure/ could break?
All food for thought!!..Pickles.

I know some people with some very big breaks who could bend some very thick steel! Between that and a CNC plasma, the rear crossmember would rip off before the bracket would bend.
Problem would be the poxy nutserts which hold it all together!

For the scientific method, I wonder how much force is put on a mudflap at say 100km/h?
And how this would relate to the torque on the 3xM6 bolts which hold the mudflap bracket on?
Might be a question to research. I do like to get nerdy...

Originally Posted by Toxic_Avenger

I do like to get nerdy...

You do?

That's correct.
Believe it or not!

Originally Posted by Toxic_Avenger

For the scientific method, I wonder how much force is put on a mudflap at say 100km/h?
And how this would relate to the torque on the 3xM6 bolts which hold the mudflap bracket on?
Might be a question to research. I do like to get nerdy...

So... down the rabbit hole I went.
Cocktail napkin calculations, and some fudge factor for good measure (engineers, cover your ears!):

The mud flap
1) Wind speed @ 100km/h = 27.778m/s
2) Wind load on a surface at this speed is approx 0.67kN/m^2 [source].
3) Approx area of the whole mud flap (assuming it is rigid, and cannot flex at all - imagine a full length bracket as pictured a few posts above) is 1295cm^2. Let's call it 1300cm^2 or 0.13m^2
4) 0.67kN*0.13m^2 = 0.0871kN
5) Rule of thumb to approximately convert kilo Newtons ton Kilograms of force is to multiply the kilonewton value by a factor of 100 [source]
6) Therefore a rigid mudflap, in rough terms, is exposed to approx 8.1kg force at 100km/h (assuming full wind force is seen!).

So I hope the math is correct!

I didn't get too much info on the bracket, and what its limitations might be, but probably safe to assume that it's up to standard. The bracket, being a piece of thin bent sheet steel, with no other bracing, would experience some interesting loads as it acts like a first class lever on the bent edge against the crossmember, and puts the M6 bolts under tension as the mud flap is bent towards the rear of the vehicle. The steel bracket would surely have to bend before the M6 bolts were stripped or fail due to being under tension, but this is just a thought.

TL;DR, I think a flat plate style mud flap brace is not going to cause too much issues at highway speeds. This might be a different story under other forces like water, but even so, I think the limiting factors might be the bracket (or the material of the flat stiffening piece) rather than the attachments to the crossmember.

Why not just swap the bracket for a hinge?

Does this help?
https://encrypted-tbn0.gstatic.com/i...-pD93pEVB2k8xr

Nice!
The 90 needs moar LSX and twin race pipes for the ladies.

Originally Posted by Toxic_Avenger

So... down the rabbit hole I went.
Cocktail napkin calculations, and some fudge factor for good measure (engineers, cover your ears!):

The mud flap
1) Wind speed @ 100km/h = 27.778m/s
2) Wind load on a surface at this speed is approx 0.67kN/m^2 [source].
3) Approx area of the whole mud flap (assuming it is rigid, and cannot flex at all - imagine a full length bracket as pictured a few posts above) is 1295cm^2. Let's call it 1300cm^2 or 0.13m^2
4) 0.67kN*0.13m^2 = 0.0871kN
5) Rule of thumb to approximately convert kilo Newtons ton Kilograms of force is to multiply the kilonewton value by a factor of 100 [source]
6) Therefore a rigid mudflap, in rough terms, is exposed to approx 8.1kg force at 100km/h (assuming full wind force is seen!).

So I hope the math is correct!

I didn't get too much info on the bracket, and what its limitations might be, but probably safe to assume that it's up to standard. The bracket, being a piece of thin bent sheet steel, with no other bracing, would experience some interesting loads as it acts like a first class lever on the bent edge against the crossmember, and puts the M6 bolts under tension as the mud flap is bent towards the rear of the vehicle. The steel bracket would surely have to bend before the M6 bolts were stripped or fail due to being under tension, but this is just a thought.

TL;DR, I think a flat plate style mud flap brace is not going to cause too much issues at highway speeds. This might be a different story under other forces like water, but even so, I think the limiting factors might be the bracket (or the material of the flat stiffening piece) rather than the attachments to the crossmember.

Awesome,....I think we agree with each other.
Pickles.