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Old 8th February 2010, 08:20   #1
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Default Skid Plate for my Jeep

Hi I recently changed my sandmaster tyres for 15 inch bfgoodrich A/t.The plan is to have a set for on road and seperate tyres for off.Till i have enough money to buy 31 inch tyres and the corresponding alloys, which would cost me around 50k.

At the recent pune offroad excusrion i sadly missed my 7.5x 16 sand master's, with the jeep grounding at quite a few break overs....Not a nice feeling to know your gbox cross member is getting a taste of sweet earth that often.

I have decided to fabricate a skid plate from just behind the oil sump and extending slightly past the crossmember with a smooth underside and space for the prop shaft to articulate.

If somebody has done this before or has any ideas please let me know.

Thanks
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Old 8th February 2010, 09:48   #2
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Originally Posted by motocamp View Post
Hi I recently changed my sandmaster tyres for 15 inch bfgoodrich A/t.The plan is to have a set for on road and seperate tyres for off.Till i have enough money to buy 31 inch tyres and the corresponding alloys, which would cost me around 50k.

At the recent pune offroad excusrion i sadly missed my 7.5x 16 sand master's, with the jeep grounding at quite a few break overs....Not a nice feeling to know your gbox cross member is getting a taste of sweet earth that often.

I have decided to fabricate a skid plate from just behind the oil sump and extending slightly past the crossmember with a smooth underside and space for the prop shaft to articulate.

If somebody has done this before or has any ideas please let me know.

Thanks
Doesn't the Jeep already have a factory-fitted skid plate under the transfer case cross member? My 4x4 MM-540 did.
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Old 8th February 2010, 14:28   #3
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Yes it does , but mine has been removed at some point and i thought i could try something a little different from the stock plate something like the picture underneath.
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Old 8th February 2010, 16:42   #4
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Default Real functional skid plates can be heavy!

There seems to be at least 6 sq.ft. of 7 mm sheet steel in the illustrative pic you have provided, by my guesstimates. I would guess it weighs at least 30 kg.

However, it seems to be quite the trend to use custom made aluminium-alloy skid plates.

Skid plates, should typically be made of 7 to 16 mm thick sheet.
Assuming you use a 2 sq. ft. of 7 mm plate,
it will weigh 10 kg if made of mild steel, 10.6 kg if made of stainless-steel and 2.875 kg if made of aluminium. You can do the arithmetic!

You might also like to read about how a Toyota 100-series Land Cruiser owner, went about building custom skid plates.
My skid plate build

Ram
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Old 8th February 2010, 19:49   #5
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Yes mine would be heavy,but functional i hope.

I am using a 3mm thick mild steel sheet for my skid plate.

It will be roughly 3.5 feet long and 4 feet wide and will contour to the cross member, with additional flats on the inside of the plate for ridgidity, but not too much stiffness, it should give a little if the impact is very hard.

I am guessing it would weigh 30 to 35kg.
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Old 9th February 2010, 10:25   #6
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There's a ton of useful information in Samurai's Skid Plates thread (Grand Vitara gets custom made skid plates). Must read.
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Old 9th February 2010, 11:49   #7
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Default Skid Plate

Hi Kunal,

The Original M&M 4x4 JEEPs were fitted with Skid Plates.

If the Skid Plate is missing, it is an indication, that the Gearbox or the Clutch Assembly was worked upon, because the mechanic, mostly never fitted it back.

The Purpose of the Skid Plate it to allow the JEEP to skid/slip/slide over obstacles where the Cross-member is likely to get caught.

The original Skid plates for M&M JEEPs were 4mm sheets with mounting and T-Case Drains Holes, weighing about 3-4Kgs (1' X 1.5').

i) CJ3B/CJ500D/MM540 same skid plate
ii) M&M CLASSIC has a slightly different Skid-Plate
iii) The MM550XD have a Larger Skid-Plate

All the above Skid-Plates are interchangeable.

Regards,

Arka
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Old 9th February 2010, 12:00   #8
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Quote:
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Skid plates, should typically be made of 7 to 16 mm thick sheet.
Assuming you use a 2 sq. ft. of 7 mm plate,
Isn't that too much? I used 6mm skid plates for my GV only because aluminium is softer than steel. If you are using steel plates, 3mm or 4mm is sufficient.

Motocamp, the skid plates should cover only those parts that need protection. When we make custom skid plates, we tend to overdo the protection and end up compromising on the GC. You may be better off getting a stock skid plate in the junk yard instead of trying to make one. We are all getting by fine with OE skid plates.
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Old 9th February 2010, 12:49   #9
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@Samurai i agree with you, 7 to 16 mm sheet is too thick for a skid plate, any idea how it is bent into shape?
OT- a 8 mm thick sheet can be used for winch mounting, gurus what do you say?

Spike
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Old 9th February 2010, 15:03   #10
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Default Winch Plate

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Originally Posted by SPIKE ARRESTOR View Post
@Samurai i agree with you, 7 to 16 mm sheet is too thick for a skid plate, any idea how it is bent into shape?
OT- a 8 mm thick sheet can be used for winch mounting, gurus what do you say?

Spike
Hi Spike,

I have made Winch Plates of 2 thickness.

i) 8MM on my MM540XD
ii) 6MM.

I think the 8MM plate will put too much stress on the chassis which is 4MM C-Section (Boxed In), and as a result made a few slits on the bottom of the plate to allow it to flex with the chassis.

Advantages of the Winch Plate.
i) Stiffens the Chassis and improves handling i.e Anti-Roll Bar
ii) In case of a MRCBT/Hydraulically Assisted PS prevents the chassis from flexing, under, steering action.

Regards,

Arka
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Old 9th February 2010, 21:05   #11
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Quote:
Originally Posted by Samurai View Post
Isn't that too much? I used 6mm skid plates for my GV only because aluminium is softer than steel. If you are using steel plates, 3mm or 4mm is sufficient.
Read this:
Skid plate thickness - Dakota Durango Message Board

Quarter inch steel skid plate is 6.35 mm thick.

Assuming the density of steel is a realistic 7.9 g/cc, the weight of skid-plate material would be 4.66 kg per square foot.

Closed box-section and Tube-section chasses can offer
reduced price and weight and structural rigidity even with thinner material than skid plate material.

A skid plate on the other hand must offers surface shear strength, so plate thickness is relevant. It can't afford to tear away on first contact with rock.
Wow, I must go back to my engineering mechanics class which I attended in engg. college, thirty-four years ago in 1976.
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Old 9th February 2010, 21:25   #12
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I think what you guys are saying about the stock skid plate makes sense, but i thought since i dont have one , would try my hand at making one to my own design.

The idea is to have a skid plate which also works like a bash plate , where under a heavy impact the plate has some room to bend a little so my cross member does not take the impact directly.I plan to sandwitch half inch rubber bushes between the plate and the gbox c member so it has room to give a little.

The total lengh of my skid plate afer revising the dimensions will be 2.5 feet long x 4 feet wide and will contour to the chassis.

Like anything made to order it will have pros and cons as compared to stock.

Let's see if the pros out weigh the cons

Thanks for the inputs guys , let's see how it turns out.
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Old 9th February 2010, 21:27   #13
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Ram, the Dodge Durango weighs as much as two MM540s. No wonder it needs a 6.35mm steel skid plates. But for CJs and MMs at half the weight, 4mm is very much enough. I am yet to see any dent/bend in my Jeep skid plate after so much offroad abuse.
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Old 9th February 2010, 21:40   #14
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Quote:
Originally Posted by ex670c View Post
Hi Spike,

I have made Winch Plates of 2 thickness.

i) 8MM on my MM540XD
ii) 6MM.

I think the 8MM plate will put too much stress on the chassis which is 4MM C-Section (Boxed In), and as a result made a few slits on the bottom of the plate to allow it to flex with the chassis.

Advantages of the Winch Plate.
i) Stiffens the Chassis and improves handling i.e Anti-Roll Bar
ii) In case of a MRCBT/Hydraulically Assisted PS prevents the chassis from flexing, under, steering action.

Regards,

Arka
Hi Arka,

Nice info there, your idea of providing slots in the bottom is perfect, it will provide stress relaxation in critical areas, also the winch mounting plate helps in stiffening the chassis but i don't think it will act as a anti-roll bar simply because anti-roll bars have certain degree of "compliance" built into them which is not achieveable through a plate acting as a fixed joint. Did you experience any improvement in handling characteristics of your vehicle after this mod? Please correct me if i am wrong.

Spike
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Old 10th February 2010, 10:13   #15
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Default Anti-Roll

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Originally Posted by SPIKE ARRESTOR View Post
in stiffening the chassis but i don't think it will act as a anti-roll bar simply because anti-roll bars have certain degree of "compliance" built into them which is not achieveable through a plate acting as a fixed joint. Did you experience any improvement in handling characteristics of your vehicle after this mod? Please correct me if i am wrong.
Hi Spike,

The winch plate cannot definitely replace the Anti-Roll Bar, but it has similar effects on handling, minor but noticeable.

Regards,

Arka
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