JamesDL

Hi all-

I'm trying to install the engine in my PT-40, and the it seems like way the instructions tell you to mount the needle valve gets in the way of the steering arm. I have a notch cut out of the left side of the cheek for the needle valve to stick out sideways. I'm thinking of mounting the needle valve so it points down, out the bottom of the plane. Is this a good way to do it? Am I doing something wrong here?

I'll post a picture of what I'm talking about in a few minute.

James

JamesDL

Here is an image of the problem. If the steering arm were a little higher, it would go over the needle valve. However, then the control rod would hit it anyway. Is this really where the needle valve is supposed to go?


EDIT - I just noticed on the plans that they have the needle valve attached directly to the carbeurator. However, the engine in the plans is a 4-stroke. The engine I have is an O.S. .46AX

oldvet70

My Feedback: (10)

Take another look at the plans and you should see that the steering arm goes below the engine mount. It probably needs a wheel collar at the top of the front axle to keep it from dropping out of the engine mount but the arm goes below.

JamesDL

That is a great idea... but the plans show the steering arm on top...

I'm going to re-route the guide tube and mount the arm below, that should definitely work.

Thanks

oldvet70

My Feedback: (10)

Well the plans show a front mounted needle valve like most used to be. It will need to be relocated to work with your rear needle valve.

JamesDL

Yeah I agree... it will be pretty simple to re-route the steering pushrod down below the engine.

Jeep Jockey

I just finished a PT-40 with an OS 46 AX max......I mounted the needle valve vertically behind the engine (so I didn't have to cut out the cheek like you did), I left the nose wheel control as on the plan and things work without any problems at all...........good luck with yours.

JamesDL

Hey Jeep Jockey-

Could I see a pic of your arrangement?

I already redid the steering tube on mine and I think it will work, although there is more bend in the rod than I would like now. I had my needle valve pointing up, and it still didn't fit. Maybe I should have tried putting the needle valve on the other side where the throttle tube is. Actually maybe I can still do that, and patch the cutout I made in the side of the plane...

James

Pilot Sofer

Hey James. If i were you, i would check the Great Planes website, and see if there is a technical notice on the page of the PT 40. usually sometimes they write the instrtustions wrong. everytime i build an airplane, i always check the web site if there is an "importan product bulletin", or "tech notice".

prgonzalez

James,

I built the PT-40 using an OS .46-FX and I did not have any problems with the engine mounted per instructions. What I think it is happening with the .46-AX is the engine is larger that the FX series. In that case, when you mount the engine based on the gap between the spinner backplate and the fuse side, the remote valve goes too close to the steering arm.

If you have not drilled the engine mount, I would suggest you relocate the engine a bit forward. The whole plane will come nose heavy anyways and a few millimeters will not make a huge difference for the overall setup. You will have to add weight to the tail anyways. Although, the PT-40 will fly well even without any weight at the tail. It will be nose heavy but flyable at decent slow speed.

The other way is to re-route the steering arm to the bottom of the engine mount where you are supposed to install a collar.

My 2 cents,

Pedro