Cab Mount Chop - Food for thought?

sarcasm?

 

Not sure if someone has mentioned this, but I think it is going to depend a lot on what the wheel is made of, and how secure the mounts are welded to the frame.

1. The 1/8 inch steel of the cab mount (its close to that on the mount I believe), will be stronger than than an aluminum wheel. Cab mount vs aluminum wheel, the cab mount wins every time, even if chopped poorly.
2. Also, you will notice that the mount is welded to the frame too. This is the obvious weak point in the system. Considering steel wheels and aluminum wheels do not break the weld of a normal cab mount, we can probably assume that the welds will not break with a shorter chopped mount. Per the laws of physics, the welds should experience less stress from a shorter mount due to the shorted lever.
3. If people take the time to weld a plate back in, the strength of the cab mount (protection from collapsing, and resistance to being bent) should not be hindered.

To summarize, the chop is not the weak point, its the welds connecting the mount to the frame (which are not chopped traditionally), and technically speaking the reduction in length will result in less force on the welds due to a shortening of the lever. So, is it likely that someone could screw up their chop so badly that the steel fails before the welds... probably, though unlikely. My vote is no, I do not think a mediocre or well done chop job will impact safety in the event of a crash.

 

The wheel is alloy, the frame/cab mount is steel. I don't ever see the wheel passing through or even remarkably damaging the frame. The cab mount would simply crush the wheel before it ever "passes through" or even dents the cabin


EDIT: ^^ @broke_down Beat me to it, well said

 

Just randomly landed on this thread & want to offer a quick opinion. I really don't see a problem with CMC's, unless you are seriously worried about that very specific crash as shown on the video. That seems like the only type of crash that a cab mount would --- hypothetically --- be of help.

If you're driving over 50-60 mph & God forbid, you hit a metal post, you're going to need more than the cab mount to save you.

 

I also have been a mechanical engineer for almost 30 years and, you are wrong on many points of your post.
Let's get a few facts straight to start with:
The cab mounts are UHSS with around 1480 MPa strength. You should know that you cannot patch or splice or section anything safely over 440MPa. It just won't work.
In addition, the cab mounts are designed to deflect the front unsprung mass downward in the event of a very specific crash, and that is the small frontal offset crash. That is really the only type of crash that could cause the wheel or brake rotor to encroach into the cab space. Are you honestly going to tell me that scabbing a 3/16 piece of cold rolled steel is going to do the job that the original formed mount is doing?
Stating your opinion is one thing. As an engineer, stating your opinion as fact (like you did) is a sure fire way to lose all credibility.
If you are going so fast that you send the wheels and tires towards the cabin in a full frontal crash, I concur, you have other problems that make cab mounts inconsequential.
By the way, the 2016+ Tacoma has several parts to the frame and cab pillars, all different strengths that all require different methods of repair/replace. This information is freely available. Google it.

Bottom line, I will never ride a family member around in a vehicle that has had a safety feature modified by some jackleg with a torch in a driveway. Chances are good I will never be in an accident where this feature is needed, but we both had probability and statistics right?

 

You both need to fully understand F=ma because you both blatantly ignored this basic equation in your posts.
Which is stronger... a 3/4 piece of plywood or a ping pong ball? Yet, I have seen a ping pong ball get shot through a piece of 3/4 plywood.

While it is good to discuss these things and the safety aspects, please try to understand the basic physics of a crash before offering your opinion.

 

Being an engineer myself I know you are speaking the truth. I also know that you would have needed a lot if velocity to get the ping pong ball through the wood. May I ask what was it shot with?

 

I'm not a crash test engineer nor have I even studied car crashes, but I do have a degree in ME. It seems to me the equation more relevant here is Fd=1/2mv^2, or the kinetic energy in the system. In which case velocity is the driving factor here. Which is moving faster at the point of impact, the wheel, or the frame? It appears to me the wheel is almost completely stopped.

Again, I don't study car crashes for a living, but this is my .02

 

Ball broke sped of sound lol. Three hundred feet of tubing an a big ass high pressure air tank. I listed an absurd comparison just to show what you might think is not the truth.

 

One other thing that everyone is forgetting about is liability.

Imagine you sell a truck with a CMC and that truck is in an accident where the driver dies. What are the chances that a jury will side with you over the buyers grieving family when they sue you after learning that you altered a safety feature on the truck?

 

Impressive!

Another great example is a bullet and a steel plate. It's impressive how much steel a soft (lead and copper) bullet will travel through.

 

Me either and I think either is applicable. My point is, in this case, if I have enough m or enough a then it can go through anything. I trust the guys who designed it, not me.

 

https://m.youtube.com/watch?v=5hNHTWYRZkQ

 

Im sure they use far more complicated equations and on each component of the crash. Everyone here can speculate, but the bottom line is, what are the chances you're in a crash that compromises the cab mount. And on top of that, what are the chances that the CMC compromises the safety of that crash? If larger tires were my goal, I wouldn't have a problem going for it.

 

Again, it all comes down to a force balance, in both these cases, the projectile contains a greater amount of energy than the stationary object. In the crash, which has more energy, the wheel or the entire cab? Im going with the cab

 

I understand, and personally, if I were the only one in the truck I would have no problem. But if I put my daughter in the passenger seat and something would happen? No way would I do it no matter what the odds.

 

But it's not that simple. Imagine the ping pong ball was standing still and the plywood was moving supersonic the end result would be the same. Pimg Pong ball shaped hole in the plywood.

 

you realize when you buy a used vehicle it comes AS IS. It's up to the buyer to inspect it and make sure it fits their needs

 

If only that were true...

https://www.google.com/amp/s/jalopn...n-after-crash-because-shop-glu-1819359410/amp

 

I dont believe it would, I believe your result would be a flattened ping pong ball. The energy balance equation flips, and the energy would be transferred from the board to the ball. Much more energy contained in the board in that case