Changing Gear Ratio On A T5

imp said:

Seems nowadays everything HAS to be aluminum. But you won't find any aluminum gears, just boxes to contain them. If only an iron T-5 box were available.

Yeah, engines are aluminum, too. With carefully placed gussets and strengthening shelves where lots of distortion is expected. But, NO aluminum crankshaft. Or other highly-stressed parts. Because aluminum stretches and bends easier than iron or steel. A hunk of steel, ANY steel, hard or soft, has a Modulus of Elasticity of 30 million psi; Aluminum is about 13 million. That means an aluminum part compared to a steel one will deflect 2-1/2 times as much as the steel one. For wearing purposes, only 1 or 2 types of aluminum alloy are suitable for bearing surfaces, Aluminum Bronze being one. I used it when making my live steam locomotive, for the pistons and valves. Here I go, off-thread, again....

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Noobz347 said:

Just saw this. Roots vs. Twin Screw

Both have rotors and most modern roots blowers have two rotors. So what's the difference?


Roots blowers compress the air charge against the walls of the case. The rotors actually "seal" against the case. These have rotors but you can't really call them screws. The air charge cushions the area between the rotors when it's at speed.






Twin Screw blowers are a little different. When they're in boost, they touch nothing but air. The air itself in compresses against the rotors and keeps them separated. The same air charge also keeps the rotors forcefully away from the blower case.


They have different efficiency ranges and provide boost better or worse than the other depending on how fast you spin them.

Roots blowers are generally better at lower RPM and lower boost ranges. Parasitic loss is relatively low.

Screw type blowers are better at higher boost pressures and volume. They have a bit more parasitic loss over their efficiency ranges than Roots blowers (generally, I don't want to argue semantics about blowers developed 20 years apart). They have to be moving pretty well and be pressurized to the point where the air barrier is keeping all of the internal parts separated (always loved the sound of "clinking" of my twin screw during wind-down).


I'm sure I've forgotten some differences but those are the big ones.

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