Skid thickness???

[Samco Fab]

I notice that most heavier Trophy Truck's run .188 thick aluminum skid plates, and most lighter buggies run .063 skids.

I am about to cut out the main skids for my 7200 truck, I am in between weights compared to a full size TT, and a 1600 or 10 car (I am about 4000 to 4500 lbs) I was thinking about using .125, but I am a bit fearful of denting a tube on the chassis, but then I am also fearful of heavy things so what experience do you all have??

Also, do most guys run 5052, or 6061?

Thanks for any imput!!

[DBMETALWORX]

On our 10 car we run .250 skidplate under the motor and trans, and .125 floor pan full length.. And both are 6061 t6, the hard stuff.. The .063 floor is basically a throw away imo.. And .188 doesn't last that long either, under the rear of a buggy.. At least for us this is the case.

[partybarge_pilot]

.250 on the front and under the motor. The floors can be .188........ 6061-T6

[mpower]

.250" under all vital components including you! if you have a low ground clearence vehicle 3/8 will help out with gouging making the metal thinner, the stock mini ridgeline has 1/2" thick skids i believe. no less than 3/16" anywhere else that may see contact with the ground

i use 5052 as it tends to bend a lot further before it fractures or tears like 6061 can do with a good impact from a rock.

[Samco Fab]

I do agree, thick skids are very good. We made 1/2" 6061 skids on our production H2, and we still bent those on occasion.

Production cars need the skids to help make the chassis more rigid, my chassis does not really need it as much for structure as the stock trucks.

I also notice the front bulkhead section of most of the current Trophy Trucks and class 1's do not use any skid, which suprises me, many look very venerable.

For conversation sake, has anybody done the math on using other materials such as thinner 4130, composites, titanium, cutting board plastic like the rockcrawlers, etc.. to use for a better skid material? I notice VW uses a composite skid of some sort on the Dakar Tourag.

Thanks for the feedback, I will lean twards the thicker side of things, not the best place to go wimpy!!

[Wild bill]

.250 6000 series Aluminum under motor and trans. .125" on everything else.

[racer56]

I notice VW uses a composite skid of some sort on the Dakar Tourag.

Jabroc- http://www.jabroc.com/

http://www.pegasusautoracing.com/productselection.asp?Product=6180

[partybarge_pilot]

Jabroc- http://www.jabroc.com/ (http://www.jabroc.com/)


Looks like good speaker cabnet material.........

[Scott_F]

For conversation sake, has anybody done the math on using other materials such as thinner 4130, composites, titanium, cutting board plastic like the rockcrawlers, etc.. to use for a better skid material?

I am considering using a composite of .125 6061 on the top layer, and .250 HDPE on the bottom layer.

[FABRICATOR]

Jabroc- http://www.jabroc.com/

http://www.pegasusautoracing.com/productselection.asp?Product=6180

"Jabroc Skid Plate Material, 6mm thk, 50 x 100cm (19.5 x 39") ...............$119.99"

If you don't mind that a rock can take it out, it soaks up flammables, it is flammable, and it cost as much as scrap titanium, it might be okay.:)

*********
It depends somewhat on what you are trying to protect. General chassis protection should be a minimum of .125 6061T6. Other places and things should be designed as needed. Size, weight, and whether it must be removable should be considered.

[HardCharger81]

I was thinking of using UHMWPE, Ultra high molecular weight polyethylene. I have a 5 x 10 sheet of it that's 3/8" thick left over from a
horse hospital corral I built. It's cool stuff. I've used it in cow and horse working facilities that I've built.
It's super hard, it can stand up to a horse kicking the s**t out of it. I thought it'd work great as a skid.
I'm sure others have tried it? It's also very slick on the suface, and chemical resistant.

[Samco Fab]

Looking at stiffness vs weight and tensile strenth vs. weight in this fancy boatbuilding book that my Dad has, titanium looks pretty good for a skid material. It also would be thinner and harder than aluminum. You might be able to get a plastic material to work good, but you would loose a tiny bit of ground clearance. If your race car burnt to the ground, the Ti skids would be as good as new, very heat resistant!!!

Anybody have a sheet of 1/8" titanium laying around that they sell for cheap?

What different Ti alloys are there commonly and what one would work for skids? Whatdrawbacks are there other than the obvious $$$ ?

[Samco Fab]

I was thinking of using UHMWPE, Ultra high molecular weight polyethylene. I have a 5 x 10 sheet of it that's 3/8" thick left over from a
horse hospital corral I built. It's cool stuff. I've used it in cow and horse working facilities that I've built.
It's super hard, it can stand up to a horse kicking the s**t out of it. I thought it'd work great as a skid.
I'm sure others have tried it? It's also very slick on the suface, and chemical resistant.

How stiff is this material? I think that rockcrawler guys use this quite commonly for skids, it slides better over rocks and does not hang up the foreward progress. That might help a little bit in high speed stuff, but probably not as good of a selling point.

Does the UHMWPE burn very easily?

[BajaFand]

How about a .125" full skid for under the car with .250" delrin on it? For the front and under the motor/trans area go with thicker 5052 AL with delrin on that as well. It seems like delrin would slide over rocks easier and not gouge as much.

[HardCharger81]

Samco, I know it doesn't have a very high melting point. I ruined a piece of it welding/cutting to close to it.
I wouldn't say it burns, but it does melt.
I'm not a material engineer, but I was told that its harder than stainless steel by quite a bit.
The way I found out about it was I did some contract work for a friend of mine thats a millwright.
We replaced the conveyors in a food processing plant. All the conveyors were stainless, not sure what grade.
But the guides they rode on were UHMWPE. The conveyors had actually visibly worn from running against the UHMWPE.
The plastic look almost new. I had never seen the stuff before then, and I did alot of work for my dad in the dairy
industry at the time. So we bought some and started using it in some of the things we made for dairies, horse ranches, etc...
The 3/8" ish (I'm not sure exactly how thick it is, never bothered to look, its a factory second.) sheet I have seems considerably stiffer than Aluminum. Way more impact resistant.

[Ol' Curmudgeon]

sheet I have seems considerably stiffer than Aluminum. Way more impact resistant.

But does it bend or shatter when impact load exceeds specs?

[Samco Fab]

http://http://en.wikipedia.org/wiki/Ultra_high_molecular_weight_polyethylene

[Wendell #527]

This is interesting. I have a 3/16" thick 6061 T6 skid plate and it definitely needs to be thicker. A large rock punched in a dent that actually went through the skid plate and dented the chassis. I was going to go to 1/4" on the whole thing. Maybe Aluminum isn't the bomb to use...

[Samco Fab]

They use the UHMWPE in bullet proof vests in fabric form. It obviously absorbs energy, and mabye this is a good thing in a skid.

I would worry it would not be rigid enough, and transfer load into the chassis and dent it. I may go to the plastic store and get a test sample and beat the hell out of it.

[westtexasbaja]

This place sells plastic sheets.... Has some material specs as well.

http://www.onlinemetals.com/merchant.cfm?id=181&step=2&top_cat=181

[djblakely]

McMaster Carr
Plastics
This product matches all of your selections.

http://www.mcmaster.com/param/images/plastics/bigrecsheet.gif

Part Number: 8769K72 (http://www.mcmaster.com/itm/find.ASP?tab=find&context=psrchDtlLink&fasttrack=False&searchstring=8769K72) $81.98 Each
Material
Polyethylene
Polyethylene Material
UV-Resistant Very High Molecular Weight Polyethylene (VHMW)
Backing
Plain Back
Finish
Smooth
Shape
Sheets, Bars, Strips, and Cubes
Sheets, Bars, Strips, and Cubes Type
Rectangular Sheet
Thickness
1/2"
Thickness Tolerance
±.025"
Length
48"
Length Tolerance
±.063"
Width
24"
Width Tolerance
±.063"
Opaque
White
Operating Temperature Range
-40° to +140° F
Performance Characteristic
High Impact Strength, Weather Resistant, Wash-Down Applications
Tensile Strength
3800 psi
Impact Strength
Unbreakable by notched Izod test.
Tolerance
Standard
Hardness
Shore D: 68
Specifications Met
Food and Drug Administration (FDA) Compliant

[Wild bill]

On paper the poly material looks good but I concerned about anything plastic near the motor or trans. If there is a fire then what? weeny roast anyone?

[djblakely]

McMaster Carr
Aluminum
This product matches all of your selections.

http://www.mcmaster.com/param/images/aluminum/unpolishedmillsquaresheet.gif

Part Number: 89155K26 (http://www.mcmaster.com/itm/find.ASP?tab=find&context=psrchDtlLink&fasttrack=False&searchstring=89155K26) $134.07 Each
Material
Multipurpose Aluminum (Alloy 6061)
Shape
Sheets, Bars, Strips, and Cubes
Sheets, Bars, Strips, and Cubes Type
Plain
Finish/Coating
Unpolished (Mill)
Edge Type
Square
Tolerance
Oversize
Thickness
1/4"
Thickness Tolerance
+.016"
Length
24"
Length Tolerance
±1/4"
Width
24"
Width Tolerance
±1/4"
Material Certification
Without Material Certification
Temper
T651
Hardness
95 Brinell
Yield Strength
40,000 psi
Flatness Tolerance
Not Rated
Temperature Range
-320° to +300° F
Specifications Met
American Society for Testing and Materials (ASTM)
ASTM Specification
ASTM B209
WARNING
Hardness and yield strength are not guaranteed and are intended only as a basis for comparison.

[djblakely]

Personally I have always used 3/8" 6061 T6 Aluminum for all my critical areas, but these data sheets make you wonder if UHMW might be an option. Notice the UHMV sheet is 1/2" and T6 is 1/4".

[Samco Fab]

I got 2 small pieces of UHMW and HDPE. They both did a good job at taking good hits from a ball peen hammer, the HDPE is lighter and 3 times cheaper than the UHMW, the UHMW is more rigid, harder to hammer a punch through harder to slice. Either could work.

2 things I dont like about it, it is not as rigid as the aluminum so it could peel back if you hooked the front edge. Not all impacts are straight on, some hook an edge, and that stuff is rigid ,but not as much as aluminum. You could run it a lot thicker, but that may defeat the purpose of being lighter.

It also has a max working temp of about 200F, that is pushing it around exhaust. It also burns, not just melts. I burned a couple of small pieces and they burned, not just melted. I might be ok with melting but another combustable may not be the best idea.

Back to Titanium!!

I bet I end up with 6061 on the bottom of my truck:(:p

[slcpunk74]

We are replacing our .25 skid because it's bent... Yeah I am with those that say .250 for the front.
http://i35.photobucket.com/albums/d158/troopdiggin87/0143.jpg