OT: What purpose big smokestak funnels on old train engines?

I gather the big funnel stacks were required on wood burning train engines, but I cannot understand the physics of smoke flow that required all that tinwork. Thanks to anyone who can explain that. That and the dished wood wheels on civil war era cannons. Why not mostly planar style like the wagons? Leonard

the funnel or widening in the smokestack housed a spark arrester. It had to be a large diameter so as not to restrict flow.

The funnels were part and parcel of a screen system to limit the emission of sparks (which were hard on passengers, and fields/forests and plains) there were several elaborate designs to service the screens, and prevent plugging. The taller they were (limited by tunnels) the happier the engineer.
The dished wheels were stronger because they were a cone not a plane. they could also be tipped for a bit of positive camber that made more room at the top, and still had the spokes vertical between the axle and ground. JimN

I heard they were for Locomotoves that burned wood and served as a spark arrestor as wood burners threw more sparks then coal???

John T

Could be kind of tough on the wooden train cars too!

Hi Leo,

It's called a deaccelerator double cone. As combustion products is drawn into the stack, they expand thus dropping pressure thus slowing down the exhaust products where heavy ash and embers drop out of the exhaust flow. We still use this theory today to clean all types of smokes stacks.

The top of the cone re-accelerates the exhaust to create more draw on the combustion chamber. That's why they use a double cone so they didn't loose FPM(feet per minute or how fast the air moves) or CFM(cubic feet per minute or the volume of air that is moved).

A muffler on a diesel engine performs a similar function.

T_Bone

It was for sparks so they didn't start forest and town fires etc etc .

The EPA was around then as well. just a kiddin

A old duffer once told me that in the early days the old horse farmers were totaly against trains with all the smoke and fire. He stated that they were blamed for barn fires ten miles away. Those folks did not approve of change as we often do now with many new concepts being forced on us.

In NE Iowa trains did indeed start many fires in dry years, and fire departments did not have a chance to even get to the timber fires for a few hrs. Cell phones, and fire trucks have improved this over the years.

On that same note, did you ever wonder why all farm buildings were kinda space apart? They could loose one building perhaps, and still survive. They often had four legged lawn mowers to keep the grass short, less dry grass to burn and spread the flames. The farm animals would pasture directly around the house.

A good ol boy said his dad always insisted that it was stupid to not have your barn on the opposite side of the creek from the house. His refferance was that a house had a fire potetial with a chimney fire. The old sod houses used to prop a pole up under a chimney (made from sod also) so if there was a chimney fire they could kick the pole out from under the chimney and fight the chimney fire on the ground, and save the house.

Thanks, it makes sense. Leonard

Think about how the axle pushes on a wheel when it's in the side of a hill or going around a corner. Dished out makes the weight push straight down to the rim rather that forcing the spokes out and blowing the wheel apart.

My FIL (94) tells when he was a water boy on his pony at threshing time seeing a tossed cigarette by a man who was going to the dinner table at noon, the cigarette being taken by a bird up to a nearby cow shed. Later the shed burned down and spoiled the day for the whole crew. I don't know if this is a rural fable, but his other stories are pretty much based on facts. Leonard

If you look closer you will see that wagon wheels are dished too.

I know for a fact of a house fire in a nearby town that started by a bird taking a discarded cigarette to its nest in the house attic.

I do know that they spew out alot of sparks. I have a home that is near Durango, CO. They have a very cool historic train that runs to Silverton there. When the train runs a small rail vehicle follows with fire equipment to make sure nothing is burning up.