[Closed] Full Face Helmet - material question.

Anyone care to enlighten me?

I wouldn't worry about material.

Pick the comfiest one that is in your budget - weight will play a part in that.

Dave

Plastic helmets (ABS, Polycarbonate etc) generally work in a different way the Fibre (Glass, Carbon etc).
The shell on a Fibre helmet has very little flex in it and relies on the Styrofoam liner to do the majority of the shock absorption.
Plastic helmets have much more flex in the outer shell and it is a combination of the shell and Styrofoam that provides the shock absorption.
This often means that fibre helmets are less likely to be damaged if dropped than a plastic one and are normally tougher.
The above are generalisations as there are many different types of Plastic and Fibre constructions.
Fit is the most important thing, more important than construction. So try as many as you can to get an idea of the shape of your head, and which models suit, as well as the size measurement.

I Brief (Very Brief):

Manufacturing wise CF and Fibre glass from a manufacturing techniques perspective aren't really that different, the same cheaper moulds could be used for both and the same methods of layup and probably the same resins and curing/autoclaving?

An ABS shell requires injection moulding and that means more expensive tooling, however the trade off is much shorter cycle time and far fewer man hours in production. ABS is a very tough plastic and you can tweak its performance by using glass fibre or glass sphere fillers...

In service there are weight benefits to CF over Glass-fibre (GF), strength wise the construction is probably more critical than the actual fibre material, Alignment of fibres relative to the loads the helmet is likely to see in an impact and the type of Matrix (Resin) and fillers all have a baring, the primary reason anyone goes for a FF over any other lid is facial protection obviously, hence the construction should be such that in a frontal impact the Jaw section under impact actually transfers some of that force laterally into the rear of the shell, many of the post stack damage seen on CF/GF lids has been focused at the side (about level with the wearers ear lobe-ish) despite this being someway from the actual point of impact, often the construction of the jaw section is marginally more rigid than these side portions, I assume this is the designed in failure point as it's seen as the least critical position, you don't want to transfer too much load into the rear of the shell, as this may impinge on it's ability to deal with secondary impacts to the rear/sides?...

In an injection moulded shell it's not so easy to have the same sort of full fibre alignment (in theory) you could use a chopped strand filler (small glass fibres which would tend to follow the flow of materialin the shell as it's being moulded), but these would have other production implications, the other thing to avoid in a mounlding (Especially a piece of safety equipment) would be "Knit lines" where material injected from different points in the tool meets up, and having already cooled slightly form what is effectively a fault line in the structure, this could well cause a key weak point. Often locally heated tooling is used to keep material from cooling too quickly (More cost again) alternatively clever use of knit and may be exploited to create intentional, repeatable failure points in a structure...

But other wise you have to treat it as a homogenous lump of material, ABS is a very tough material, for consumer goods which require plastic housings it's one of the better materials but it's nothing like as cheap as polypropelyne or nylon and hence you'll tend to find it more on premium products, especially portable items more likely to see a drop or two, it has good impact strength, and is more UV stable than many other materials (meaning it is less suceptable to becoming brittle with exposure to sunlight) plus it can be used with fillers to impove its structural properties if you like, but you'll not make a light weight lid from it...

ABS is used for make Skate/dirt piss pots (I've had a couple) where it's robustness suits the generally more rough treatment it will recieve, for XC lids thin polyprop and polystyrene shells are sufficient as weight is the primary requirement.

For a FF lid 'd say the trade off of weight, Impact performance and cost is probably in favour of glass fibre laminates, the weight saving for CF is there but relative to the cost GF make pretty good sense...

TBH though it's a rather long winded topic and you could spend forever looking at +/-s associated with material selection.

Go on best fit and level of certification

Whatever you buy, make sure it fits well and if you crash (hard) in it and do damage; that you've paid little enough for it that you'll bin it without worry.

Seen far too many ancient scratched/damaged Arai's been used because the rider paid +£400 for.

When we went we just bought basic 661's, then £45.

I went for the basic (plastic) 661 Strike, I was going to get the more expensive 661 (evolution?) which is fiberglass but it didn't fit by a long shot, so even within brands they use different models heads so one XL isn't the same as another.

On the upside it was ~£40, and when I crashed I didn't die despite fairly extensive damage to the top, jaw and polystyrene liner. I replaced it with an identical one so that my goggles would still match 🙂 but odly the fit isn't quite as good so maybe it's worth trying on the exact helmet before you buy (I got my 2nd by mail order as obviously it's not this years stock).

Excellent, thanks for the feedback everyone