Electric Skid Plate/Air Dam thickness
 

I'm going to fabricate and install a movable skidplate that extends forward to make an air dam at highway speeds. This will have two hinges on the bottom of my bumper and hang straight down to within an inch or two of the ground. I will place electric actuators from Firgelli Automations to retract it to a workable skidplate. What thickness of steel is everyone using for their homemade skidplates. It has to be somewhat light but sturdy enough to stand up to the occasional rock or two. In the air-dam position it will hang down at a 90 degree angle from the truck. In the skidplate position it will be at about a 50-55 degree angle from the truck and rest against a bump-stop or something. I'm planning on using 6 inch actuators to move it from the cab. Any thoughts?

when you get this done please take some pictures. I want to see how it turns out

I would think 3/4" should be sufficient ;)
Seriously, I think a steel plate will be too heavy unless it is really thin, in which case it will not be good for a skidplate. I would use a composite, thin steel or aluminum and retract it just out of the way, not doubling as a skid plate.

I was thinking 12-14 gauge sheet steel with some 1 1/2x1 1/2" angle iron for the mounts. The angle iron would absorb any hits to the skid plate (not like I'm an avid rock crawler or anything) but keep the weight within reason. Plus I could bend it myself pretty easily. Would I be better off welding the angle to the sheet or using rivets?

Here's a picture of my topper with the electric actuators (making it into a retractable camper....)

I would say, use rivets. This way you will not show welds through the material and if you do shear the rivets, this will absorb the energy of impact. Then you simply rivet again. (I always prefer engineered assembly vs. welded).
Nice topper by the way!

A real, functional skid plate on a vehicle this heavy should at minimum 3/16", better 1/4" or 5/16". I'm making mine out of 1/4" stainless, including brackets, as we speak. Just think...if you hit a pointed rock with a piece of 14ga, with 6000lb+ of truck above it, will that 14ga hold up? Nope. I would go with at least 1/4". Neat idea, BTW.

You have a light truck! I took mine to the truck scales and it is nearly 7,500. Regardless, I agree with you that thicker is nicer but a 14 ga skid plate is better than nothing and is probably enough for the OP's non hardcore intended use.

My truck is about 7,500 pounds now with the topper on and a bunch of junk in the tool box. I'm thinking that 1000 square inches of 3/16" steel is going to weigh about 60 pounds (20inches times 50inches=6.9square feet). That same size of 14 gauge is about 21 pounds. Throw on some angle iron brackets and it'll be 65 pounds or 26 pounds flapping in the wind. I'll have to think about the weight issue.

I would use 1/4" aluminum. Guess my utility bed adds more weight than I thought, I weighed my truck the other day and it was 9,020lbs. and I that wasn't even that loaded up. Eric

I would like to see it when finished too. I am interested in what it will do for your MPGs. My 01 QC/LB scales @ 7120lbs empty.

Kinda hard to believe that putting 1000 square inches of flat plate in front of your truck will increase mileage, but we'll see. I think I'll put a hardish nylon strip on the bottom that is adjustable up and down to save the plate and experiment with the amount of clearance I need. These actuators are fairly fast and I would be able to adjust it on the fly. I'm guessing that 2 actuators with 200 pounds of force should be sufficient, but I don't know how much force is put on a plate that size at 70mph....

Are you actually using it as a skid plate or just an air dam because those are totally different needs? Most air dams are made out of plastic for the light weight and flexibility.If this is going to be an air dam I would rather have some give in the design than jam it in the ground on a rough bridge or RR crossing and jam it into the frame or under carriage. I am planning on building a new bumper with the idea of it extending it lower and further under the front of the truck to help deflect the wind but the lower three or four inches will be formed out of Rhino Linings for the flex in the product(shameless plug).

Wayne

Gotta see this when its done. One more vote for pictures.

As for material...aluminum is a joke if you plan to poke at it with rocks. No plastics will be sufficient either. I would go with .125" steel with your angle for support. It will take most of the abuse a big truck is going to see (like you said, its not a rockcrawler). One thing I would suggest...make it spring loaded. If you can incorporate a sping system into it, then if you do hit something with it down (in air dam form) it will fold up without being damaged. I also would suggest no going 90* to the ground, leave it angled back about 10* just to make sure if you hit it one something it folds the right direction.

1/8" sounds like it might be a good compromise but isn't readily available unless it is floor plate (diamond plate). Here are some options for me:
1/8" steel sheet = .125" thick
12 gauge = .1046" = 4.375 lbs/sq.ft. = 30 lbs
11 gauge = .1196" = 5.000 lbs/sq.ft. = 34.7 lbs
10 gauge = .1345" = 5.625 lbs/sq.ft. = 39 lbs

Any of these would work, I think. As for springs I can't think of an easy way to rig that up. The 2 actuators are good for 200 lbs of force each and cost $100 each so if I hit something it would only set me back a little over $200. I may just use some sort of shear bolt on the top part of the connection and see how that works out.

Unless you're an engineer.... 1/8=11 gauge. I know its not exact, but **** close. I have made all the skids for my jeep out of 11 gauge plate and reinforced where needed with angle or square tube. Never had a rock bite one yet....and I beat the heck out of that Jeep!

As for spring loading...Shear bolts would be a lot simpler, you cant just make it "breakable" and if the need should arise...replace a few bolts and get back on the road.