Metal front bumper/tow hook mount

[turbosax2]

That was the least of the priorities, but on the list. Mostly for room. I can see this bar being used in my future for mounting things, such as the intercooler, and having as much room as possible between the bumper and radiator support is preferable. Flat also limits airflow to the intercooler.

 

[Calan]

Damn it Eric, you have me obsessed with this now. And you're making me earn my pay.

Err...wait...have we discussed my rates yet?

How about this?

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Total weight should come in at approximately 11.5 lbs (aluminum), and you get to keep your IC airflow. Max VM stress in the lower beam is somewhere around 22k psi, and lateral stretch is now down to about .3" of deflection at the hook (probably a little less than that, since the hook is also being analyzed as aluminum instead of steel).

I'm now pretty sure that I was overly conservative on the load initially; I've been running the last few analysis with a static horizontal load of 3500 lbs/f, and a vertical load of 200 lbs/f.

Note that this using 1.5 x 1.5 x .188 wall tubing, 6063-T5. If this design will work, we'll have to find out exactly what material is available and run the numbers again. If everything looks good after that, I can build separate parts and then analyze everything as an actual assembly.

When you're ready to pull the trigger, I can provide you with all of the flat aluminum pieces (6061), so all you would need to buy is the tubing.

 

[turbosax2]

Cool design, but when that's flipped upside down it won't work. I'm not even sure there's room for that as-is, there's just not that much clearance between the FMIC and the bumper.

 

[Calan]

Cool design, but when that's flipped upside down it won't work.

Ehhh... why not?

I'm not even sure there's room for that as-is, there's just not that much clearance between the FMIC and the bumper.

The distance between the inside flat (outer IC face) and the inside of the bumper cover is the same as the dimensions you gave me in post #151 (4"). In other words, this sits in the exact same footprint as the very first curved bar design I came up with.

 

[turbosax2]

Most of the dimensions I've given you are guesses. I'm just not sure it would actually work.

For the tow hook to be 2" higher when it's flipped, the tow hook would then have to sit on the straight piece, right?

I'm digging the design, but I feel like we're getting a little too complicated. I have to look for some stronger grade aluminum that we might be able to just get away with the original design without the straight piece.

 

[Calan]

For the tow hook to be 2" higher when it's flipped, the tow hook would then have to sit on the straight piece, right?

Oh I see what you are saying.

That's an easy fix though, and it would actually simplify things. I could just replace the top two center gussets with a piece of 1.5 tubing that sits on top of the round beam and welds to the face of the straight beam. That would also probably add quite a bit to the strength of it.

It's really not as complicated as it looks. In some ways it's much simpler than the other designs. The curved beam is the only component that is a bit tricky.

 

[turbosax2]

I mean complicated as in there is a lot of welding there. I pay for every weld. And upside down, that flat piece will effectively cut off flow from the upper portion of the FMIC.

 

[Calan]

I pay for every weld.

But you can pass that cost on to customers when you start selling a bunch of these things.

I bet you could figure out a way to get a bunch of that cut and fab'd up for just the cost of material and shipping if you thought about it for a bit...seeing as how it's aluminum now.

 

[turbosax2]

IF I can even fit a straight piece there, how small can we go? If we go smaller maybe we can avoid it sitting right on the FMIC and blocking flow. We could use a tubular piece there too if necessary.

 

[Calan]

Could you not just move the whole thing outward just enough to clear the FMIC? You'd only need like .25" or so, or even less. As I have it modeled now, there is room to bring the curved beam back inwards to compensate for it.

We really need to know exactly how much room there is between the front of the FMIC and the inside of the bumper cover before we can get too serious about it.

 

[greengoblin]

Can you even bend 6063 t5? This vid did not look promising.

A6063 T5 - YouTube

 

[turbosax2]

With a 1.5" rounded tube, there should be no wiggle room. Like I've stated before, I only have 1.5" between the FMIC and the bumper cover.

I don't understand your question. I won't be able to measure anything for another couple weeks, unless Brian can between now and then.

 

[turbosax2]

Can you even bend 6063 t5? This vid did not look promising.

Dunno. Just focusing on design right now...

But the arc is so slight I'm hopeful we can make something work.

 

[Calan]

I only have 1.5" between the FMIC and the bumper cover.

But only in the corners, and then getting larger as you move toward the centerline of the car... right?

You can always knock 1/4" or so off the outside of the beams right at the corner to allow the whole thing to slide out for some clearance.

 

[turbosax2]

But only in the corners, and then getting larger as you move toward the centerline of the car... right?

Correct.

 

[Calan]

You could probably take the beams down to 1-1/4" or so thick at the point where the corners of the IC sit if you really needed to, and not lose a lot of strength. Notice in those plots that there is very little deformation at that point (roughly .04"); most of the bending stress is located at the centers of the beams.

 

[greengoblin]

Dunno. Just focusing on design right now...

But the arc is so slight I'm hopeful we can make something work.

I understand that but material is a large part of the design since it play a huge role in the strength. I think you guys are to a point where you need precise measurements so you know the true design parameters. IMO

 

[Calan]

I understand that but material is a large part of the design since it play a huge role in the strength. I think you guys are to a point where you need precise measurements so you know the true design parameters. IMO

Yep and Yep.

I've run enough different conceptual models now to know where the stresses and problem areas are going to be. Now it's a matter of figuring out exactly what we have to work with.

The last design I posted will provide the most strength for a given assembly weight and load on the hook, based on the constraints we currently have to work with. Now it's just a matter of Eric deciding what he can live with and what he can't.

I think what he is looking for is a design that:

1. is super lightweight
2. fits into a limited amount of space
3. can hold up to approximately 4000 lbs of force
4. is reversible
5. requires no modification to the front bumper cover
6. is easy to machine and weld
7. has very few welds
8. is inexpensive

I think it would be easier to just design a new car.

 

[turbosax2]

Hopefully either myself or Brian can get those measurements in a couple weeks. We have extremely limited time with the cars, which makes everything difficult.

That's a good list, Craig. Like I said before, I'm fully aware of how picky and stubborn I am. If it takes me months to figure out a design I can live with, then so be it. I've pondered over a year on some projects. I'm not willing to compromise what I want until I feel I've exhausted every option. I'll say this: of that list, I'm most willing to compromise on price. If I have to pay two times more to make this thing out of unobtainium rather than aluminum and it satisfies everything else on the list, then I'd surely consider that. If that means that I couldn't sell any of these to the general public because of the high price, no sweat.

The reason why I mentioned welding as a cost is because my welder takes great pride in his work and takes his sweet old time doing it. He's expensive, but his work is top notch.

That being said, I can't tell you all (especially you Craig!) how much I appreciate your support and assistance with this project

 

[Calan]

That being said, I can't tell you all (especially you Craig!) how much I appreciate your support and assistance with this project

NP. The weather sucks and I'm too broke to do anything anyway...it was either work on this or sleep until it's time to go back to work on Monday, assuming I'm not snowed in.

Besides, it's not like you guys haven't helped me out on several occasions.

 

[greengoblin]

unobtainium

New super strong alloy discovered

Fibrecore™ - As strong as Steel, as light as Aluminium…

New Titanium-glass Alloys Are Tough, Cheap And Light-weight

 

[Flash]

I would make the tow hook able to pull out when needed and spring back tucked away when not used.

 

[turbosax2]

For what reason? They exist, but I'm not convinced of their strength.
Retractable Tow Hook (14")-Rennline, Inc.

 

[Calan]

Holy crap. $125?

 

[knochgoon24]

I'd probably just make it so the inserts were threaded so you could just unbolt it when it's not needed.