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HelicopterTurbine Helicopters › PHT3 RPM
10-20-2009 06:38 PM  8 years agoPost 1
GC1

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Manchester, UK

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I'm helping a friend with his PHT3 powered hotcat which is going into an Airwolf body when it gets sorted.

The turnine runs at a max RPM of about 93,000 through a set of pulleys and gears that provide approx 76:1 step down. Today we picked up some new 820mm blades and have been told that they should run at a headspeed of around 950rpm. Doing this using the engine rpm limiter, it would be set at an rpm of around 72,200. Whilst this is easy to achieve with the electronics I don't know if the turnine will actually operate effectiveley at this speed, or if it will be in danger of a flameout if the blades stall it. I'm not sure if the correct answer if a different gearing setup.

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10-20-2009 08:46 PM  8 years agoPost 2
Peter Wales

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Orlando Fl

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I run my 800 mm blades on a 4 blade setup at 1250 rpm. If you try and run the turbine at 72000 rpm you will have problems

Peter Wales
http://scalehelicopters.org

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10-20-2009 11:12 PM  8 years agoPost 3
GC1

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Manchester, UK

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Peter,

Thanks for the reply. Are you saying you wouldn't bother running at the lower speed for that size of blade anyway. If I wanted to run a lower speed should it be done by gearing down? What is the lowest sensible turbine rpm for the PHT3?

Sorry for al the questions.

Geoff

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10-21-2009 03:02 AM  8 years agoPost 4
Peter Wales

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Orlando Fl

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I wouldn't run 800mm blades at 950 rpm. I run 1100mm blades at 950rpm, so whoever told you to run them that slow either didn't know what he was talking about or was selling you some crap blades

If you run the engine slowly, you dont make much power and the recommended rpm range is 94,000 - 103,000 which gives you a power range of 3.5 - 5kw. If you drop that much in 10,000 rpm, imagine how much you will drop with another 20,000 rpm gone. So, if you insist on a headspeed of 950, you will have to get the turbine geared to give that rpm and the lowest Jetcat offer is 962rpm.

Have a look here for the full specs on the pht3

http://www.jetcat.de/jetcatturbinen...terturbinen.htm

Peter Wales
http://scalehelicopters.org

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10-21-2009 08:29 AM  8 years agoPost 5
PETER ROB

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Devon UK

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PHT3 gearing

I have to agree with Peter W,The turbine does it's job best at the top end of its RPM range, then change the gearing on the heli to achieve your required head speed
Correction on what Peter said about the lowest head speed JetCat offer,
My PHT3/3 mechanics are geared for 915 headspeed
Peter R

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10-21-2009 10:17 AM  8 years agoPost 6
WIRLYBIRD

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CAPE TOWN / SOUTH AFRICA.

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Hi Peter , did you manage to get what you wanted from Ludwig Benda?
Dave.

WHAT GOES UP MUST SURELY COME DOWN.

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10-21-2009 12:26 PM  8 years agoPost 7
Peter Wales

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Orlando Fl

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I dont think you can get the PHT3-3 into a Hotcat can you Peter?

Peter Wales
http://scalehelicopters.org

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10-21-2009 01:23 PM  8 years agoPost 8
PETER ROB

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Devon UK

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I dont think you can get the PHT3-3 into a Hotcat can you Peter?
Peter, I do not think so, but it would be an interesting project
The point I was trying to make was that JetCat have new gearing for the PHT3/3, that will bring the headspeed down to 915 RPM,the same gearing would fit into the PHT3,
Peter R

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10-21-2009 01:35 PM  8 years agoPost 9
Peter Wales

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Orlando Fl

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That makes sense now. However, I still dont think Geoff should be running 900 rpm on 800mm blades.

My Cuatro runs 1800rpm on 800mm blades!

Peter Wales
http://scalehelicopters.org

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10-21-2009 11:45 PM  8 years agoPost 10
GC1

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Manchester, UK

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Thanks for all the info, I think we will stick with the higher head speed.

Just to confirm, the PHT3 does go into the Jetcat Hotcat without modification. This model has flown previously with that configuration.

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10-22-2009 01:40 AM  8 years agoPost 11
Peter Wales

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Orlando Fl

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Yes, but the 3-3 Peter R was talking about has the turbine at the top and the tail drive at the bottom, the other way round from the PHT3

Peter Wales
http://scalehelicopters.org

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