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[papasmurf]

Adam the sealing ring where an exhaust pope fits into the cylinder head is solid copper, and many exhaust manifold gaskets and cylinder head gasket have copper in them.
So I suspect the toxic gas and illegality are a myth.

[nigelphoto]

papasmurf ' the sealing ring where an exhaust pope fits'. When I was serving in the Grey Funnel Line we are told never to talk about politics, religion or absent women . . . . . .

[Caboose]

Hi All,
In my young days in the early sixties, (yes, I ,was there!) it was believed by some, and actually suggested in the technical lines of the popular magazines, that wrapping copper wire around the exhaust pipe for a good few inches at the cylinder head would prevent blueing.
Not sure if that ever worked as I never actually tried it, but I saw a good few bikes, mainly Café Racer types which had!
REgards Dick.

[PeteF]

I remember that Dick. You could also buy a loose coiled "spring" to fit over the header to dissipate the heat.

[Adam]

Fair comment, Papasmurf. Adam

[Bullet Whisperer]

Any copper sealing rings between the exhaust ports and header pipes on bike engines are sealed out of the gas flow by their very nature and purpose and are a drop in the ocean compared with a full length exhaust system made from copper, with the gasses passing through the copper for several feet of length and reacting together.

[Bullet Whisperer]

Copper disulphide is the poison substance emitted, apparently ... http://www.nsra.org.uk/newforum/showthr ... r-exhausts

[jefrs]

Revband - I'm puzzled because I didn't go into any science at all but you are welcome to look up Universal Gas Laws, Charles' Laws and PVT (pressure-volume-temperature) correction, they are well established laws of physics and nothing like the pseudo-science of the Cheshire Ribbon Company. It's pretty simple O-level stuff. It's what makes your motorbike work, it's not an explosion that drives your piston down but the very rapid thermal expansion of the product gases. If you quadruple the (Kelvin) temperature of the gas in there, it suddenly wants to occupy four times the volume.



Yes, I have also seen pipes glowing red hot, this is hidden by wrapping but I can assure you they still get jolly hot. On the one hand they (I'll blame Cheshire Ribbon Co.) are saying the wrap makes the pipe cooler, next they are saying it increases gas temperature. However it is not keeping the exhaust hot that aids it escaping the pipe, the gas is cooling rapidly anyway; the exhaust gas ejects itself under excess pressure as soon as its valve opens and the piston pushes the last of it out.

Stoke is ~80mm, divide that by half the time it takes to perform one revolution and you have piston velocity (assume racing at max revs, about 3 meters per second), beer mat stuff not real science. This is why trials bikes get hot, they're racing them at full chat but not getting any real air cooling, although back when I was attending it was more about negotiating a natural obstacle course than trick-cycling jumping over cardboard boxes. There was usually a lot of water cooling. I remember one event where what had been a puddle became a good size village pond and they kept ditching in it, one chap lost his bike completely in there and we had to dredge it out before someone else hit it.

Having the exhaust port glowing cherry red is not an entirely good idea. One wants to keep the combustion chamber cool to maximise thermal expansion and thus increase power output. Besides, steel gets soft glowing red around 1000°C, not good.

[papasmurf]

Copper Disulphide is what is emitted when copper bearing ore is heated to extract the copper, not when copper pipe is heated.

[Revband]

Jeff you will be surprised to know that I pretty much agree with your last post, what I don't agree with is this

"The wrap gets hot to thermal equilibrium with the pipe, hot enough to burn, so it's not that. The pipes got bashed regularly so some wrapped them to lessen damage, or hide it from scrutineers". Now that is totally incorrect, most scrambles/trials riders who wrapped the exhaust including me only wrapped the exhaust where it was most likely to cause a burn and did not cover the entire pipe. If the wrap reached the same temperature as the pipe as you stated then any sort of insulation on anything would be a complete wast of time that includes wearing clothes in cold weather of course.

As for scrutineering, well I have never in my life life seen or heard of a bike failing due to a dent in the header pipe.

The science comment was probably a bit out or order so I apologise for that, the reason it was made is because whenever anyone politely tries to suggest you may have made a slight error you always come back fighting with a lot of (what I called it in my earlier post)