> >>
>>>> >>>>
>>>>>>I have 2 Honda Accords, a 2001 V6 and a 2002 4 cyl. If the timing
>>>>>>belt breaks, will it cause extensive engine damage?
>>>>>>
>>>>>> The manual on the V6 is unclear when to change the belt it says to
>>>>>> change it at 60,000 miles if you drive in very hot or cold
>>>>>> conditions.
>>>>>> I do not have a manual for the 4 cyl, it was a used car. It has >>>>>> 94,000
>>>>>> on it now and runs perfectly.
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>> I believe the recommended change period is 105K miles or 7 years
>>>>> under normal conditions. My own interpretation of very hot has
>>>>> always been desert type conditions (Death Valley, Sahara), very cold
>>>>> would be similar to the northern Midwest areas and Canada/Alaska for
>>>>> the 60k change.
>>>>>
>>>>> The key is not just the belt itself, but the internal cords/fibers >>>>> that
>>>>> do not allow the belt to stretch, which are usually made from
>>>>> Kevlar/Twaron (both are aramid type high tensile fibers). I'm not >>>>> sure
>>>>> if the base OEM Honda belts are rubber, HSN or carbon fiber type (I
>>>>> would suspect that they may be the one of the latter two, as at some
>>>>> point in the 90's they increased the recommended belt change >>>>> interval by
>>>>> a fairly large amount).
>>>>>
>>>>> Here are a couple of articles you may want to read....especially the
>>>>> thermal properties of the Kevlar and interference engines.
>>>>>
>>>>>
formatting link
>>>
>>>> irc, kevlar is subject to accelerated fatigue when subject to >>>> humidity, so
>>>> i believe the cords in high quality timing belts are usually glass >>>> fiber.
>>>> the above link does allude to glass fiber use, although not in >>>> detail.
>>>
>>> "Glass fiber" is a misnomer, as it still uses a polymer carrier (ie,
>>> flass filled kevlar) as far as I last was aware of.
>>>
>>> Polymer with 30%-33% glass fiber by weight is usually what you will
>>> find in most industries. The higher percentages the more prone it
>>> will be to fracture at a specific radius due to extremely high flex >>> modulus.
>>
>> i fully admit to being rusty on this stuff, by why would you have a
>> glass- filled aramid fiber??? there is no benefit that i can see
>> unless you want to reduce elasticity of pure aramid, but the fatigue
>> properties would suck. glass is plenty stiff and virtually fatigue
>> proof if the surface is sufficiently protected. in which case, maybe
>> you mean aramid /coated/ glass fiber?
>
> There are many applications for glass filled polymers. Depending on the
> glass partical size and aspect ratios, it can greatly increase the
> Young's/Flex modulus (stiffer) without greatly losing the material
> properties (though there will be some loss). This will reduce part
> elongation and increase tensile strength, as long as one doesn't go too
> far and displace too much of the resin.
>
> Glass filled polyamides and polycarbonates are used in a wide variety
> of applications (mostly industrial).
>
> As an example (fictitious in so much as I don't have the actual numbers
> in front of me. I'd have to do some research to get real numbers as it's
> been quite a few years since I've looked into this for an application),
> one can use 10% glass fill in aramid fiber and reduce the elongation by
> a factor of 15%-25% and increase the tensile value by an almost equal
> amount, but add in 25% glass fiber, and these can values can be greatly
> reduced. Fatigue properties would be dependent on each application as
> well, depending on the expected bend radii needed, velocity, service
> temperature, glass particle size/aspect ratio and other factors. >
> Carbon fibers and nano-clays are also used, though I believe glass is
> the least costly.
absolutely, understand all that. but small particle reinforcing, to my incomplete understanding, doesn't serve well in a fatigue environment. that is the kind of mechanism by which plastic radiators crack - great low cycle mechanical properties, but when the load cycle gets up there, fatigue romps away. i would therefore expect timing belt fiber, given that it's subject to considerable repetitive strain many times that of traditional small particle reinforced plastics, to have the most coherent microstructure possible - no fillers. but i'm guessing.
>
>
>
>
>
>>
>>
>>
>>
>>>
>>>
>>>>
>>>>
>>>>>
formatting link
>>>>
>>>>> The potential damage from a broken belt is quite extensive,
>>>>
>>>> with an interference engine
>>>>
>>>>
>>>>
>>>>> and you may
>>>>> or may not see any symptoms.
>>>>
>>>> ...prior to breakage.
>>>>
>>>>