Author Topic: Cutting board skid plate tech (UHMW & HDPE)  (Read 9657 times)

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Offline Jeremiah

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Objectives (in order of priority):
* Protection of critical components
* Slide well
* Light as possible
* On a student budget (made with tools I have, or can cheaply acquire)

Steel is heavy, and aluminum is too expensive, and I don't the tools to cut, drill, or weld with. Enter: UHMW & HDPE (cutting board plastics). They're light, slide better than metal, absorb impact better, can be cut / drilled with wood-working tools, are quiet when scraping, and readily available. UHMW is stronger, but costs x2 more than HDPE. 1/2" x 24" x 48" sheet is about $100 UHMW, or $50 in HDPE.

I've read of people using both materials, but most favor UHMW for it's superior strength. That said, HDPE still gets favorable reviews from the few daring enough to try it first. Minimum recommendation is 3/8", most opt for 1/2", and the more hard-core go with 3/4" or 1". I think 1/2" is minimal if you counter-sync your screws / bolts (to protect them from rock rash, and shearing).

1983 SJ410, 1.3L SPOA on 31"
1996 4 door, 235/75/15 Dakota M/T, OME 1.5" Lift
1996 Geo Prizm
2008 Yamaha FZ6

Offline Jeremiah

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I took some rough measurements in my 4 door...

Let's say there's 2 pieces I need:
#1 I'll call "belly". This piece will run from the front cross member, and run back to the transfer-case mount. "Big belly pan's" width will go from frame rail to frame rail. It's in danger of getting melted from it's proximity to the exhaust & cat. Dimensions: 32" x 32". "Small" belly pan will be much narrower, leaving the exhaust exposed. Because it wouldn't be bolted to frame, it may be a weaker design & need provisions for extra support. Dimensions 32" x 16". Both protect front drive shaft, transmission, t-case, and rear of oil pan.
#2 I'll call "front skid". It runs from somewhere near the front bumper, and back to the cross member. It protects the carrier (aka front diff), and front of the oil pan. Dimensions: 21" x 21"

UHMW is only rated up to 280F, and constant temp operating temp of 180F (I'm sure HDPE is similar), so I don't think a big belly pan would work. http://www.jjorly.com/uhmw_technical_data_sheet.htm

A front skid looks much more tricky. I think taping into the cross-member would be easy enough, but I don't see a flat area to attach at the bumper end. Might be able to use the bolts where the lower A-arms are, but that will require some heating and bending: http://www.garlandmfg.com/plastics/heatformingparts.html. Ideally, I would think it best to have some kind of heating "rod" that the material could be bent over / around - where the heat is localized to the area desired to bend.

I think it's best to have the belly & skid as two separate sections, so it's easy to unbolt the front skid for oil changes. Trying to work through drilled-out access holes just sounds like a PITA (lost drain plug bolt & a big oily mess on the back-side of the skid).
1983 SJ410, 1.3L SPOA on 31"
1996 4 door, 235/75/15 Dakota M/T, OME 1.5" Lift
1996 Geo Prizm
2008 Yamaha FZ6

Offline Jeremiah

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1983 SJ410, 1.3L SPOA on 31"
1996 4 door, 235/75/15 Dakota M/T, OME 1.5" Lift
1996 Geo Prizm
2008 Yamaha FZ6

Offline Jeremiah

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Forgot to mention approximate costs of the skids...

Estimated costs for HDPE material. Double the cost for UHMW:
Big belly pan: $100
Small belly pan: $40
Front skid: $25

I like the allen-recessed / cone shaped screws I saw on those other threads, but not sure cost / availability / how to tap them into mounting points (are they self-taping?).
1983 SJ410, 1.3L SPOA on 31"
1996 4 door, 235/75/15 Dakota M/T, OME 1.5" Lift
1996 Geo Prizm
2008 Yamaha FZ6

Offline Jeremiah

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Front skid will go here. I'm thinking it can be bent up, so that it will share the bolt-hole with the lower A-arm? Maybe bolt where those three big holes are? Not really sure. You can see in the back how low the cat is - basically flush with the frame.





The back side of the front skid can attach here:



The front of the belly pan will have to share the cross member too



It's got to bolt to the rear somehow too. Maybe somewhere on the transmission mount? Looks like I've already damaged it a bit  :-\\\\

1983 SJ410, 1.3L SPOA on 31"
1996 4 door, 235/75/15 Dakota M/T, OME 1.5" Lift
1996 Geo Prizm
2008 Yamaha FZ6

Offline malodin

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mg]

It's got to bolt to the rear somehow too. Maybe somewhere on the transmission mount? Looks like I've already damaged it a bit  :-\\\\



yah, you can tell which rigs have been wheeling, the ones that are still strait havnt been offroad much:) i think mine is a little worse off than that lol.

I get a major discount on uhmw and have been thinking about some of this, maybe even to mount it easily run some strips of metal(relatively cheap) to bolt the uhmw to, i.e. use the metal to go to mounting bolt holes and what not, then bolt the uhmw to that.

Offline olija

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For the front of the front skidplate I used the holes that are close to the edges of the frame. I think they're 3/8" holes or else 5/16"...pre threaded. I have used my skidplates well and they are holding up great.

For the back of the tranny skid and the front of the t-case skid, I used the tab that is on the back of the transfer case crossmember. You can see it in your last pic. Just use some long bolts and some nuts. It's a bit of a PITA to install the first time but you get pretty good at it pretty quickly.
97 4 door kick
1.5" lift, 2" body lift, no swaybar, skids, 2" catback, sliders
01 Vitara 2.0L
2.5" lift, 2" body lift, 5.13 diffs, 4.24:1 t-case, Detroit Locker rear

Offline bcrewcaptain

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I'll chime on on the bad side I guess..the stuff makes an awesome slider....too well at times, A lot of it depends on the rig....
I had contemplated putting it on my rig, 2 things kept me from doing it...
1-cost
2-it tends to slide TOO well...with metal it slides, but in a more controlled manner...with the cutting board stuff...its like a ski....and may put you were you don't want to be......
my 2 cents
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Offline POWERSTROKEN

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   I have the 1/2" UHMW in black and I love it.  I have a piece on my front skid plate that runs right to my cat and it has been right up against it for a 1000 miles and it hasn't melted a bit.   I am about ready to make a full belly skid out of it.   My brother in law got me the stuff for free from his work and it is heavier than I would have thought.

Offline flea

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well  good to see this thread. im doing a flat bottom with a piece of 40" x 33" piece of 3/8 with aluminum backing. i have a thread at PB and ill transfer the data here when i do it./

another thing bad is it tends to gouge so replacement is mandatory.



interesting point about the too slick comment.  hadnt thought of that but im still gonna do it 

btw  the material i priced is almost 300.00

where are you pricing that jeremiah?
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Offline Uncivilized

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So what did you decide?

Offline olija

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$300??? You could easily get someone to make you some steel ones for at least $100 less than that. Or just go Calmini.
97 4 door kick
1.5" lift, 2" body lift, no swaybar, skids, 2" catback, sliders
01 Vitara 2.0L
2.5" lift, 2" body lift, 5.13 diffs, 4.24:1 t-case, Detroit Locker rear

Offline Jeremiah

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$300??? You could easily get someone to make you some steel ones for at least $100 less than that. Or just go Calmini.

Glad everyone read my carefully prepared posts [worried] The first post clearly covered why I'm considering these materials over steel. The first and third posts cover the prices of the two materials, and they range from $25 - $200 depending on coverage size, thickness and type of material. Sources below.


btw  the material i priced is almost 300.00

where are you pricing that jeremiah?

Wich material, where, what dimensions?

http://www.tapplastics.com/shop/product.php?pid=346&
HDPE: 1/2" x 24' x 48" sheet of 1/2" = $70

http://www.mcmaster.com/
HDPE: 1/2" x 24" x 48" = $65 (part# 8619K475)
UHMW: 1/2" x 24" x 48" = $96 (part# 8752K615)

McMaster isn't the cheapest, but they've got a good web site, and stock a lot of stuff.

I found cheaper examples locally, but can't find them off hand. Thought I bookmarked more sources, but guess not  :-\\\\
1983 SJ410, 1.3L SPOA on 31"
1996 4 door, 235/75/15 Dakota M/T, OME 1.5" Lift
1996 Geo Prizm
2008 Yamaha FZ6

Offline Uncivilized

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Are those places local to you, or are you planning to have them shipped to you?

I don't want to sound negative about the idea, but I still think steel is a better option, and not only because it's cheaper. The weight factor is very minimal, and as for tools,... a 4.5" angle grinder is only $20  ;)
Just make sure you have it all figured out before you make your purchase  8)

Offline flea

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well i checked it out and prices are the same as most.  the aluminum is about 1/3 or maybe a little more of the cost.

ive heard of folks in the restraint equipment industry that talk about prices like you stated but i cant seem to get it for that.


im quite confident im doing well by my supplier. :)



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Offline Jeremiah

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There's certainly something to be said for aluminum or steel, but that's not what this thread is about. That said - if I went metal, I'd just get one from one of our vendors and call it done.
1983 SJ410, 1.3L SPOA on 31"
1996 4 door, 235/75/15 Dakota M/T, OME 1.5" Lift
1996 Geo Prizm
2008 Yamaha FZ6

Offline POWERSTROKEN

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   I lined my skid plates with this stuff to protect them, and it works.  I have used my skids as ramps before and trashed them pretty good.  Not any more.  As far as being slippery I cant see it being any worse than running a bogger with no side slidding traction at all.