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Im doing a short presentation for my Turbines class on the Rolls Royce 250 turboshaft jet engine.

I can easily come up with something to get me by and get the extra point, but in the class we have one of these and I sit right next to it. For the life of me I cant think of why this engine (and ones like it) havent been put in vehicles.

This model (according to the data card in class) puts from 420-760shp and weighs 250-300 pounds. Its so damn small too, way smaller than any of our engines in our trucks.

So lets hear it, besides the obvious cost issue (which would be negated if they were mass produced for vehicles) why wouldnt this be a good idea? I've also considered spool up time, but I think the benefits outweigh the 2 second spool up time this has.

-Will
 

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crank trigger
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are they very controllable, as in getting little short bursts of power exactly when necessary on an obstacle?
what sort of heat do they generate?
when can you build me a jet truck? cause i want one bad...
 

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as far as I know all turbine engines have a nasty lag. leno has a motorcycle with a turbine in it out of an old military helicopter. he can hit the gas, but it takes a few seconds for the engine to react. and then when he lets off the gas is takes another few seconds to idle down.
 

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Yep..biggest problem is the inherent lag in spooling up or down the N1, or gas-generator- side of the turbine, which in turn, has to then spool up the power, or N2 stage..which slows down equally slowly. Top that off with the fact that all GTs are horrible on fuel whenever they are operated off their deisng point, whihc is a very narow output band that is near their full rated output.

The Allison T250 (or now called the Rolls Royce....:banghead ) is a nice unit that I've done a lot of work with when Allison still owned the company. We used a pair of Allison 571KF turbines in a missile boat prototype we designed for the Norwegian Navy. The production versions of that 70 MPH speed demon are using Pratt-Whitney turbines though. We are, at this very moment, buildng another demonstrator boat that will have a pair of 600+ SHP PT6 Pratt turbines. 40' boat too.:thumbup

The common 'thread' in my reply above? - turbines work decent in boats and other applications where throttle responsiveness is not an issue..like also M1 Abrams tanks.
 

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Back in the day, my stepdad was on a design team for GE to develop a tiny little turbine that could put out about 900shp, and only weighed about 140lbs. I have a pic of him somewhere holding the thing in his arms.

The main problem with a turbine that efficient is the startup/shutdown procedures, it involved a LOT of preheating and cooling to get the right parts of the case to expand with the blades. He had an audiotape of it starting, and for the first 2-3 minutes, all you could hear was metal on metal scraping and bending. When it got past its initial heatup stage, it would spool from idle to max operating speed in less then 3 seconds. The engine was more designed for running oil pumps out in Texas. Now he runs a turbine rebuild/service company, so I'll have to ask him about the potential of a turbine in the truck. He's got a masters in engineering, so he'll figure something out.
 

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Check out what these guys did:

Nye Thermodynamics

IIRC, the Allison T63 that they used is similar to the 250, and they used it to replace a 454
 

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Search Google for Chrysler Turbine Car. Chrysler put turbine engines in cars for about 15 years and had them working very well. I don't remember the details of why they never made production, but there's a ton of information on the web about them.
 

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Try it now!!
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I think the newer turbines have worked out most of the problems associated with older models. The complicated/hot starts, reliability, noise, efficiency have all dramatically increased. I think with just a little more effort and if they gate it down a bit, an engine like that would work.
 

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Rest in Peace Friend...
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kf4amu said:
So lets hear it, besides the obvious cost issue (which would be negated if they were mass produced for vehicles) why wouldnt this be a good idea? I've also considered spool up time, but I think the benefits outweigh the 2 second spool up time this has.

-Will
How about fuel consumption. How much fuel would it take to move a vehicle with a turbine 300 miles at basically sea level as compared to a normally aspired engine. If I remember right turbines at low altitudes aren't very efficient. I suspect that you would need to tow a fuel tank on a trailor. I have a feeling it is issues like these that keeps them off the road.
 

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Discussion Starter #10
Seabronc said:
How about fuel consumption. How much fuel would it take to move a vehicle with a turbine 300 miles at basically sea level as compared to a normally aspired engine. If I remember right turbines at low altitudes aren't very efficient. I suspect that you would need to tow a fuel tank on a trailor. I have a feeling it is issues like these that keeps them off the road.
They can be designed to be efficient at any altitude, and it makes sense for them to be efficient at 30+ thousand feet since thats where the planes are flying.

Its just once outside of the altitude they are designed for, they are horribly inefficient. I think the fact that most cars operate in a small altitude range, 0-5000 feet or so, it would make it a moot point.

-Will
 

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I think the newer turbines have worked out most of the problems associated with older models. The complicated/hot starts, reliability, noise, efficiency have all dramatically increased. I think with just a little more effort and if they gate it down a bit, an engine like that would work.
The reason the turbine I'm talking about is so fuel efficient, is because of its complicated start up process. The closer the blades are to the shell, the more efficient it is because more power is being transferred from the combustion chamber to the turbines. The clearance between the blades and the shell in my step dads turbine was less then a 1/10th of a milimeter, when the engine was cool, the blades push into the case.

I don't know a whole lot about turbines, but why would lower air density make it inefficient... if anything, it should be more efficient right?

The turbine my step dad worked on was designed to run at sea level... obviously they'd want it to be as fuel efficient as possible, or why wouldn't they just use a big diesel?

The turbines in the HH-65a's (CG helos) only run at most probably a few hundred or less feet above sea level... If they thought a rotary gas would be that much more efficient, why wouldn't they use em?

The only reason they're efficient at high altitudes is because they're essentially a big turbocharger. The combustion chamber exhaust gas turns the turbines, and the front blades, which are compressing air inside of the engine case. That air is then driven into the engine, and the rest of it is driven out the rear of the case.
 
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