22 replies to this topic

[jack mac]

As per the title , are they any good , will it stand up to the bumps and scrape`s of a metal one ? it defiantly looks better.

http://www.ebay.co.u...1c#ht_500wt_969

Cheers

Edited by jack mac, 18 May 2012 - 05:27 PM.

[minimarco]

wow that does look good. And thick too.

[mike.]

If its made properly it'll be stronger than steel anyway. It'll only be as strong as its fixings though I guess.

[TopCatCustom]

It says "road use", I'd guess that whilst kevlar is strong as hell, it won't withstand the constant pounding that aluminium will as it does not flex- every time it is smashed against a rock it will delaminate and start to break down, where metals will just deflect and bend but will not actually fragment.

If it is built up properly I think it could be as strong, especially weight for weight, but I don't think you will ever have the durability of a metal one.

[Old Bob]

They make bullet proof jackets with Kevlar so it is certainly strong enough. I think Mike is right though that a sump - guard will only be as strong as the fastenings. I have a lightweight alloy guard and plan to try laminating a couple of layers of Kevlar to it (Kevlar is commonly use for racing yacht sails so is easy to buy).

Bob

[jack mac]

Cheers fellas , any ideas on mounting then ?

[minimarco]

but I don't think you will ever have the durability of a metal one.

that's a good point, metal bend on impact and carbon shatter.

but i doubt you really need a sump guard anyway if you are careful, so I'm not sure if durability is really an issue...

[Brams96]

You could make these the same way as aircraft fuselage skins with thinner aluminium sheets laminated with fiberglass or Kevlar in layers. Strong as hell & light weight.

[Tupers]

A guy local to me who made a kevlar sump guard for his trials bike that took a hell of a beating and was only about 3MM thick.

If I was going to use the one above I would make some 3MM thick steel spreader plates to run all around the guard with an M8 bolt going into a captive nut every 100MM.

[Cooperman]

Years ago I was involved in designing and testing a combined Carbon-Kevlar sump guard. It didn't last long as the stones and flints reduced it to scrap very quickly. There was too little resistant to impact-shear loads and once a small crack develops it's done-in very quickly. It was simply too rigid to work.
The aluminium alloy ones have proved themselves over the years except for really rough events when the steel 'Scottish' guard is the thing to have.

[Brams96]

Cooperman - wouldn't using a kevlar/aluminium laminate with 1mm aluminium as the outside layer get around the cracking & impact issue as the ali would absorb the impact of stones while the kevlar laminate would add the light weight strength?

[Tupers]

I'd be interested to know how well these ones hold up to sustained abuse. They look beefy as all hell but I don't know how well the cast aluminium would hold up to heavy blows.

[Cooperman]

In principle that might work, but 1 mm is no-where thick enough. I have grooves in my aluminium one deeper than 1 mm and a dent in one side which is about 1/2" deep. I reckon the alumimium would need to be about 4 mm thick and the kevlar would do very little. Kevlar is good for certain applications, but sump guards are highy point loaded and they are scraped at high speed over granit rocks as well. Only aluminium or steel seems to work. if composite really worked the works rally teams would all use it now.
In the early 70's Datsun tried a GRP/Kevlar guard too and that lasted only a few miles.

[Brams96]

Tupers - Man, how thick is that?! I bet it weighs a bit.

.

Edited by Brams96, 18 May 2012 - 07:17 PM.

[Cooperman]

Cast alloy guards are OK on tarmac, but can shatter on rocky surfaces as found in the forests.
My guard it a prototype one which was done for Mini Spares as an all aluminium welded structure, but it would have been too expensive as a production item. I got it from the friend who made it for the material cost. I can pick it up with one finger, but it is just so strong, although a bit battered now. I once landed on it from a 3 ft high jump at about 90 mph on tarmac! It just took it fine.