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· Senior Charter Member
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Discussion Starter · #1 · (Edited)
Ok, who knows their metals?

I am planning to install a removable front tow hook on my coupe and I need some advice on the thickness of the metal for the hook. The purpose is to be able to tow onto trailer from above the car rather than below.

I plan to weld a 5/16 steel plate to the front X frame (2 inch square tube). The plate is welded from front to back and wraps around 3 sides of the square tube. I then want to bolt a flat piece to be used as the tow hook. It will need to be 18 inches long from hook eye to the bolt on plate. My plan was a 2 inch eye with a 3/4 inch frame around the eye. The neck would be 2.5 inches and would go through the aluminum ducting. When not in use, a plate would cover the hole.

My question is what should I use...steel or aluminum and what thickness do I need? The tow hook would be on a 45 degree angle relative to the wheel base and angled toward the front.

Any thoughts?
 

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i wouldn't weld anything on there.
these cars are so light that you could almost push it on the trailer with a few buddies.
if your looking for a tow hook, you could always use a clevis "rated correctly"
drill into the plate for the size pin on the clevis (these are used for lifting loads)
 

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Discussion Starter · #3 · (Edited)
This what I'm suggesting.

What should I use to make the red piece?

It needs to be about 18 inches in order to have the eye clear the front hood for a front tow. I was going to put mine closer to the center and that's why I need more length.

Marc

 

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Discussion Starter · #5 ·
Thanks,

My base plate is thicker and bigger than the picture and I'll have 4 bolts.

Marc
 

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3/8 does sound like overkill, however if you ever put any side load on it you may need the extra strength to keep it found bending over to the side. If you're sure you will only be pulling straight forward then you could probably get away with 1/4" stock.
 

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Discussion Starter · #7 ·
Is an 18 inch long piece of 1/2 inch aluminum (with a 2.5 inch body) about the same as 1/4 inch steel?...3/8 steel? of the same dimensions.

Much lighter and easier to work with but how does it compare in strength.

Marc
 

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Marc, It kind of depends on your ultimate goal for the piece and the design of the part. As others have said if the only purpose is to pull it into a trailer and the pull angle will always be pretty much be from straight ahead the piece can be fairly thin. If it will see angles other than straight on a thicker piece will serve the purpose better.

For your general consumption: Common 1018 cold rolled steel has a yeild strength of 53700 psi, 6061 t6 aluminum has a yeild of 40000 psi, 2024 t6 aluminum yeild is 50000 psi and 7075 t6 aluminum yeilds at 67000 psi.

Steel is not very sexy but its very utilitarian. 6061 is commonly used for many parts but does not have the same mechanical properties as steel. 2024 and 7075 are not as common but available and have similar and even better yeild properties as steel.

All aluminums will be lighter than steel. Steel density runs around .28 lbs/cu.in. Aluminum density runs around .10 lbs/cu.in.

In the event of material failure a steel part will fail relatively slowly and predictably. Depending on the aluminum a material failure will be more spectacular and somewhat less predictable.
 

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FFR tow hook

Fluge:

I would try to get a little closer to the idea of the FFR tow hook they use on the Challenge car. It is 1/4 inch steel with 3/16 side gussets. The pretty one in your picture is prone to bending at the lightening holes if it has any side load on it. Track tow truck drivers sometimes have to pull the car from the side at an angle to get the car behind the truck, Trust me, those guys aren't always that careful if the race director is behind schedule. Even 1/2 aluminum would bend if there is a side load with just 2 bolts and a welded on bracket on the "X" frame. I would use FFR's approach and weld or bolt a "U" shaped mount to the "X" Frame and use gussets on each side of the tow hook to prevent bending. It might need some welding, but it won't bend and rip the poop out of your aluminum radiator ducting. If you only want to put the car on the trailer and you can get a straight run at it, the pretty one would work I guess, but I would use 1/2 inch aluminum and keep the lightening holes to a minimum.

Challenge Series Tow Hook - Factory Five Parts Catalog

Ron
 

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Discussion Starter · #10 ·
Thanks for all the advice. I will post an update when I complete the work.

Marc
 
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