I want a set!! I believe we talked about this awhile back, pm me with price and specifics.

Painting. Its counterintuitive, but you need a semi smooth finish for paint. Sand them down with: 100 grit, then 220 grit, then 320 grit, then 600 grit.

For good quality paint job;

apply primer, sand with 400 grit.

Prime again, sand with 600 grit.

Seal with a primer sealer.

Apply base coat.

Apply clear coat.

Or you could powder coat them. :wiggles:

 

I want a set!! I believe we talked about this awhile back, pm me with price and specifics.

Painting. Its counterintuitive,
Or you could powder coat them. :wiggles:

I'll def. get back at you. I am getting a test set cut tonight and i'll go home and see if everything bolts up right. I'll give you the specifics when I know more. I might have to change the angle of the one on the rear. And I might want to extend and bend the front one, so It could be bolted were it wouldn't require any modification to the bumper.

What do you mean by painting is counter-intuitive? I think that it would give it that "look at me, I'm a rally car" look people go for. I don't know though, I guess I could just sell t..., I mean, do mine as is and let others worry about what color they want. Plain unpolished stainless is ugly IMO.

MMMmmmn. Powder coated Tow Hooks!

 

make me a set too!

 

The test mules are off the line. Boy are they ugly:rotfl: I made them out of carbon steel and :barf:. But the real ones should be ten times better:thumbup:

 

So it has become quiet apparent that the current design of the hook will need to be drastically changed. The rear one the most. I couldn't help but think about use less the hook I made would be compared to the one that came on the car. It was anchored heavily to the frame with two bolts and then connected what looked like part of the bumper. The part of the bumper I designed the hook for is flimsy and would probably just rip right off under load.
I took the design from these

Which would have never worked on a Subaru unless it was welded straight to the frame.

I am going to get creative with this one. I am going to make it so it bolts straight to the frame and then bends down. Because after all, this fancy piece of metal better work just as good if not better than the factory tow hook if I am to continue.

 

This pic clearly shows the delema with the rear tow hook. The three holes I circled are the factory mounting loctations. Jeremy, could you confim or deny weither or not the 06-07 use the same mounting style?

 

Bump to see if Jeremy is out there:baaa:

I'm out here but cant see the pic at work. You can email it to me if you need an answer today during the day. romancommander@gmail.com

Otherwise I'll check it out tonight.

On the design. I noticed that racing teams seem to install those aftermarket hooks you mentioned onto the reinforcement bar right next to where it bolts to the unibody. The front hook seems to be located similarly.

 

Bump to see if Jeremy is out there:baaa:

 

For example this tow hook is passenger side front bumper next to the red arrow:

As you can see here this is my problem.

http://www.clubwrx.net/forums/showthread.php?t=134283687&highlight=apr

The rear diffuser covers factory tow hook point. So I wanted to add a tow hook in between the area where the license plate is so I don't have to cut my buper, but I haven't taken it off and looked at it yet.

 

That cobb one is sweet. There is no rush. I just need to know for the future. I'm just going to make mine and if yours is the same even better

 

Direct bolt on goodness for the rear one. Here is the progress.

 

i'm down for buying a set from you if it works out. I would try to make some to, but unfortunately I don't have shop access anymore. :sadwave:

pics when done please

 

Ha ha, cool Hopefuly the night shift at my work bent the piece for me so I can test her out tomorrow

 

So turns out there is not enough matierial to be bent, so in order to get the angle I want there going to have to be welded. I think I finally got the size and extenstion of the rear hook to my liking. I am in serious need of a digital camera though. Mine isn't working any longer:sadwave:

I'll try to take some cell phone pics so people can see how far the rear hook will extend. I am quiet pleased with my progress, but it is taking alot of time and effort to get these just right.

 

well good luck! keep at it. Can't wait to see it!

is it so difficult that you wouldn't want to make another set for me to buy? lol

 

for painting I would think a good powder coating would be best, plus it will be a lot more durable. You can get it done at shops or buy the kit at Sears to do it at home if you have an old oven( or a friends oven)

 

Hey guys, I want your imput. Do you think I should lengthen the hook so more of it is showing. It is going super well. I have got the rear one about done with design. I don't know how I'm going to finish her up yet but it's def. paying off.

 

If it were me Erik I'd add a little more meat around the hole. I dunno how thick it is, but a simple tear out calc will yield your hook strength. Figure you at least want to be able too match 2x the weight of the car.

 

If it were me Erik I'd add a little more meat around the hole. I dunno how thick it is, but a simple tear out calc will yield your hook strength. Figure you at least want to be able too match 2x the weight of the car.

Ha ha, were getting tech now. I'll do that though.

Does the size look alright to you? I would like to know if you think it will work with your rear diffuser.

I thought you were selling your car?

Not before I make better stronger cup holders for it

+1 the cupholder didnt meet your emo liking

Nope

looks good, but maybe be better to make it stronger/thicker around the hole.

+1 on the powdercoating

I think powder coating would defeat the purpose of my goals with this project. I am tying to keep these as cost effective as possible. I wish I knew just how much it would cost to get them done. I have heard wheels can cost up to 60$ a piece, so I don't know how much it would cost to coat a set of these.

 

I thought you were selling your car?

 

+1 the cupholder didnt meet your emo liking

 

looks good, but maybe be better to make it stronger/thicker around the hole.

+1 on the powdercoating

 

My engineering advice would be to round all the edges to remove stress concentrations from the pointed edges. I would also thicken the ring part to make the cross sectional area larger so that it can hold more load before failure. I would also make it able to handle a lot more than 2x the weight of your car. It can easily see much more of a force (and i mean lots more) than the weight of your car as someone is trying to pull your stuck car. It is much better to go lots stronger than you want, especially since you won't be tensile testing the part.

If you want to shoot some of the specs my way, I could attempt to crunch some rough numbers for you. I'd need the material used, yield strength, cross sectional area of the ring part.

Just some thoughts. And yes, I'm a big nerd.

 

My engineering advice would be to round all the edges to remove stress concentrations from the pointed edges. I would also thicken the ring part to make the cross sectional area larger so that it can hold more load before failure. I would also make it able to handle a lot more than 2x the weight of your car. It can easily see much more of a force (and i mean lots more) than the weight of your car as someone is trying to pull your stuck car. It is much better to go lots stronger than you want, especially since you won't be tensile testing the part.

If you want to shoot some of the specs my way, I could attempt to crunch some rough numbers for you. I'd need the material used, yield strength, cross sectional area of the ring part.

Just some thoughts. And yes, I'm a big nerd.

I am a fellow enginerd so don't feel bad

-The mateial is .375" 304 stainless steel.
-ID=2.5"
-OD=3.5"
To tell you the truth, I think if anything it going to fail, it will be the bolts holding it to the frame. They are about .4375" Diameter. That means the C.S area is .1503 inches squared

The C.S area of one of the loop holes it .1641 inches squared (this is factoring it the tapper created from the Plasma Torch.)

S.S. Is also the King of the metals.

 

From my manufacturing book

The Tensile Strenght of 304 SS is 75,000 lb/in^2

I get as an answer, The tensile strength of that CS area of one of the hook loops is 12,300 Lbs.

last time I checked the wrx is ~ 3,000 Lbs, This is exactly why I choose SS, because of it's extremely high strength.

 

I will try to see what those numbers get me when I get home. All of my books are there (cept my thermo one), and my work internet is slow so I can't look up the stuff online. I agree that the bolts will most likely be the origin of failure. Maybe annealing the steel and then rapidly quenching it would be a wise idea to jack up the tensile strength. Again, I don't have any of my material science books here, so please excuse me if what I'm saying is wrong.

You also need to take into consideration the force applied to the hook from the towing vehicle as it accelerates as well as overcoming the forces to get the car unstuck from whatever it is stuck in.

Yeah, SS is a awesome material. Me likes. :thumbup: I think you have a great idea, and I don't want to sound like I'm trying to crush your idea. I'm merely trying to provide feedback.

 

No problem. I think the hook is good to go though. I trust my numbers and the more I think about it, I think the failure point would most def. be at the bolt. The moment a pulling force would put on the bolt would make it almost 7 times greater than the force on the hook it self. The shear forces on the bolts should be equal to the forces acting on the hook.

I don't know what type of man. process was done on the bolts but I am pretty sure they wouldn't exceed the tensile strength of the SS i'm using. If somebody were to break one I would gladly reimburse them with a stronger one.

 

Awesome man. Yeah, I agree with what you're saying. Were you planning on making the cross section of the ring larger? And were you going to round the edges of the ring and the edges leading up to it?

That being said, what are my chances I might be able to get one of these?

 

These tow hooks are looking pretty good. I would definetely be interested in buying some if you decide to make them for the masses.
One question though, where does the front tow hook connect?

 

These tow hooks are looking pretty good. I would definetely be interested in buying some if you decide to make them for the masses.
One question though, where does the front tow hook connect?

Still figuring that out my self. All the ones I have seen require the haking of the bumper. I am trying to make some were there is as litle hacking as posible. They will be able to drill into place.

Oh and on my choise of stainless. That is what is laying around at my work. I am certain it is extremely stronger than my other choise of A36 carbon steel. I'm sure I could find some harder stronger stuff but that would come with me having to buy it or get sneeky.

 

Uh Eric on your steel choice....err umm errr....Stainless isn't all that strong comparatively, in fact carbon steel has a higher tensile. 1028 has a tensile of 87,000 psi, cromo steel ranges from 80,000 psi to 128,000 psi.

Bolts:

Grade 8.8 metric bolts have a UTS of 115,000 psi

Grade 9.8 have a UTS of 130,000 psi

Grade 10.9 have a UTS of 150,000 psi

I believe the hook bolts are Grade 10.9.