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Home✈️Aircraft🚁HelicopterHenseleit 3DNT - Rocket - 3DMP › Choosing an engine for my 3D-NT.
11-12-2005 09:26 PM  14 years ago
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Bonkers

rrApprentice

New York

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Choosing an engine for my 3D-NT.
I'm thinking of picking up an O.S. c-spec w/ pump:

http://www2.towerhobbies.com/cgi-bi...p?&I=LXEVC4&P=0

My questions:

1. Can I simply drop this engine into the heli? I.e., will it fit as is? Or, will modifications to the engine or heli be necessary?

2. What modifications need to be made, if any?

I'm guessing that, at very least, a hole will need to be made in the fiberglass shroud to accommodate the taller cooling head of this engine.

Thanks!
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11-13-2005 12:55 AM  14 years ago
Bonkers

rrApprentice

New York

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There's something I'm not getting....
The Graupner 1935 engine is just an O.S. C-SPEC without a pump (and a different cooling head).

Why can't I just purchase the non-pumped C-SPEC from Tower Hobbies?

(my heli is left-rotating, by the way).
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11-13-2005 03:51 AM  14 years ago
Bonkers

rrApprentice

New York

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Can you give me a little more info?
According to Henseleit, you can simply drop in an O.S. .91 SX-H in it. Other than some minor variations in the crankshaft

What is it about the regular O.S. .91 c-spec that doesn't allow you to simply install it into the 3D-NT?

What is it about this Graupner engine that does allow you to do so?

(I'm not very engine-savvy, so you'll have to be detained in your explanation!)
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11-13-2005 07:37 AM  14 years ago
Obiwan

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Sevilla, Spain

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Bonkers,

I run an OS 91 HGL C-Spec no pump. It is basically a C-Spec with a longer crackshaft and a larger heatsink.

FG
Best way to predict the future, is to Invent it.

FORMERLY KNOWN AS ForrestGump
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11-13-2005 09:18 AM  14 years ago
BigChopper

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Cambridge, UK

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Bonkers

It depends if you have a left hand or right hand rotating model (both variants are available).

If you have a right hander (same as most other helis) then you need a counter rotating engine because of the way the transmission is (gear reduction by belt drive).

If you have a left hander then you can install a 'normal' rotating engine, but you need the special heim crankshaft.

You cannot use a regular OS91 because of the need for a special crankshaft (be it either normal or counter rotating)

This is the disadvantage with the 3DNT, other than that its a great heli.

The OS91 FX HGL with the lotterle carb works very well and is as smooth as it gets, cheap to run on 0% fuel. But its under powered compared to C-Spec etc.

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11-13-2005 03:35 PM  14 years ago
Bonkers

rrApprentice

New York

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BigChop....
Thank you for the clarification.

My 3D-NT is a left-rotating version (i.e. main blades go counterclockwise).

I'd like to install a c-spec in it, i.e. the O.S. .91 SX-HGL c-spec, but don't know where I can find one here in the U.S.

Is there anyone in this country who sells it?
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