Anyone with O Level Physics?

[Big Jim]

Great fun was had yesterday, trying to fuel and run gas powered locos in the cold.

I had some success after stuffing my cans into my clothing to warm them up. (I looked more dodgy than normal with a can stuffed down a trouser leg and one up an arm pit)

So can anyone tell me why 70/30 mix is more effective at lower temps than butane. Does the propane alter the evaporation temp of the liquid gas thus making it easier to transfer or is it more complicated than that?

Also why don't we run on mix all the year?

[Tony Bird]

Hi Jim,

Propane freezes at a lower temperature than Butane so will vaporise at a lower temperature and it also has a higher calorific value so produces a hotter flame. There is no reason not to use mix all the year round though a lot of manufacturers say that their gas tanks are tested for butane only if memory serves about 185 psi, the butane 70/30 mix 313 psi, pure propane which we don't use 559 psi.

Regards Tony.

P.S. you forgot your brick. See you Wednesday?

[TonyW]

On my locos that will take it I use mix all year round because it is cheaper and easier to obtain (from a local German supermarket) where I live.

I use butane all year round on the locos that won't accept mix. These are older models with square-cornered gas tanks and made in the days when mix was rare in the domestic market.

Our friends in warmer climes have a completely different set of problems, of course. On a recent visit to California in 90degF/32degC heat I was intrigued to see garden railroaders all using a temperature sensing gun to check the temperatures of their gas canisters and their locos before fuelling. Apparently a 3 degree difference in temperature is needed for the gas to flow.

They also have to deal with termites, raccoons, heat expansion, ....!

[Big Jim]

Thanks both Tony and Tony.

Tony B, sorry about that, I will see you Wednesday.

Tony W, next doors cat and the odd rogue hedgehog don't really come into the same league do they?

[IrishPeter]

In AZ heat expansion was my bugbear, but it was an intermittent problem generally confine to June and July when ground temperature was anything up to 130F. Then a curve would pop out of the ballast quite suddenly creating an instant derailment blackspot. The temperature range on my line in a typical year was 10F to 100F, with a daily range of up to 40F. I tended confine operating sessions to times when it was between 40F and 85F for personal comfort more than anything else.

Cheers,
Peter in AZ

[dizzysteamer]

In AZ heat expansion was my bugbear, but it was an intermittent problem generally confine to June and July when ground temperature was anything up to 130F.  Then a curve would pop out of the ballast quite suddenly creating an instant derailment blackspot.  The temperature range on my line in a typical year was 10F to 100F, with a daily range of up to 40F.  I tended confine operating sessions to times when it was between 40F and 85F for personal comfort more than anything else.

Cheers,
Peter in AZ

O my goodness I will never complain about temp differences again

dizzysteamer