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The Angle of the Engine Dangle


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In other words, perpendicular to the ground or to the wing? In this link,  Sergei, the gent behind the Druz144 series of, very nice looking, engines explains his method of attaching pylons to wings.  A gent with the username of skyking takes issue with his method as the engines are perpendicular to the ground and he favours a perpendicular to the wing approach.  So who is correct?  

 

https://www.airlinercafe.com/forums.php?m=posts&q=11204

 

In the photos I’ve looked at, no matter the airplane, they all seem to hang straight down.  A test fit of the engines on my Revell 747 build positions them slightly splayed outward but not perpendicular to the wing, accounting for the dihedral. That could just be a matter of seating them correctly to the wing, however.

 

Your thoughts on the matter?

 

Dennis

 

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It could be either it depends on how the designer designed it. 

afair the F-6 Hellcat's engine had a thrust line at an angle to the fuselage, the front of the engine pointing down at an angle, not aligned with either the wing or ground, A couple of bombers were the same, afair the Merlin engine Whitley also had up angled engines so as it flew, the fuselage took on a nose down attitude.

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Interesting question. I too would like to know the answer. AFAIK engine position and subsequent angle of thrust is dependant on which aircraft it's fitted to. There is not just whether it is pointing up or down hill to consider, there is also whether the engines thrust is convergent, divergent or parallel to both the fuselage and other engines.

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I think most aircraft engines are not mounted parallel to the the line of flight or the aircrafts' centreline, Shackleton engines point downwards at the front and I think the 747s are pointed upwards.

 

However, I could be mistaken, but I think Dennis is possibly asking that when viewed from the exact front or rear is the engine pylon itself at 90 degrees to the wing dihedral, or true vertical as in 90 degrees from the ground?  So if the wing has a 4 degree dihedral the pylon will angle outwards by 4 degrees.

This possibly varies across aircraft types also, but on the 747 the pylons are about 90 degrees to the wing dihedral and angle outwards slightly towards their bottoms.

In reality the rake of the pylons and the fact they 'twist' towards their forward inboard edges makes it very hard to tell, so on a model I think you can get away with either angle.

 

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1 hour ago, 71chally said:

is the engine pylon itself at 90 degrees to the wing dihedral, or true vertical as in 90 degrees from the ground? 

Exactly that, James, is Sergey’s method correct, 90 to the ground, or is skyking’s, 90 degrees to the wing.

 

They appear to be 90 degrees to the ground in this photo.  Also, the pylons seem to be slightly offset. But that could be my vision. 

 

resized_6ddd4bb2-e3c3-42c8-b517-84ef3eb6

 

Dennis

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I don't think they are though Dennis, at first glance they might look it, but look more closely and they look more angled with the wing.  It's more pronounced on the inboard pylons as the wing dihedral washes out by mid wing.

I have taken some photos which I think show this, will try and post soon.

When the outer wings lift in flight it would make the effect even more pronounced.

 

You can see in that shot what I mentioned previously that the pylons 'twist' in on that upper rake, you can see there in the shadows

Edited by 71chally
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It’s very subtle though isn’t it, James.  At least in this photo.  In the plans I’ve been using (and I know about plans) they do seem to cant outward.  I’ll post a photo tomorrow.  

 

Dennis 

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14 hours ago, DMC said:

A gent with the username of skyking takes issue with his method as the engines are perpendicular to the ground and he favours a perpendicular to the wing approach.  

I know skyking quite well. You might say that he and I are very close. We agree that the engines of Boeing's 707 and 747 were/are perpendicular to the wing. So are those of the Douglas DC-8. All confirmed by engineering drawings and tech manuals. Airbus apparently takes a different approach to engine mount design.

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13 hours ago, DMC said:

It’s very subtle though isn’t it, James.  At least in this photo.

Dennis 

It is Dennis, which what I meant earlier that I'm not sure that I would notice this on a kit, but if one is fussy then I suppose it would be an issue.

 

I offer these as a way of illustrating the angle, look at the engines/pylons on the stb'd wing of the nearest one

50230771602_6ebe68498a_b.jpg

Boeing 747 -436s G-BYGA & G-BYGE by James Thomas, on Flickr

 

24965065935_776325b771_b.jpg

Boeing 747 -436 G-BNLX British Airways by James Thomas, on Flickr

 

16183738585_3be5c38796_b.jpg

Boeing 747 -412 BDSF N400SA Southern Air by James Thomas, on Flickr

 

 

I think this picture shows the angle quite well, I have trued the picture up so that the aircraft is perfectly level, 

50315569857_0f7e31a1f2_b.jpg

Boeing 747 -41R G-VAST by James Thomas, on Flickr

 

These two pics were taken with the camera at true horizontal, in hindsight I wish I took these with more wing in the frame, so I might go back and do that, notice the engines are in exact alignment with the pylons

50314720153_5695278029_b.jpg

Boeing 747 General Electric CF6 Turbofan by James Thomas, on Flickr

 

50315388461_46d0d3f5f9_b.jpg

Boeing 747 General Electric CF6 Turbofan by James Thomas, on Flickr

 

 

It is hard to notice the angle, the wings are 7 deg dihedral, so in theory the pylons would be 7 degs off vertical which isn't that visually noticeable over their stubby depth, and the pylons themselves are quite complex in their shape and angles which doesn't help guage things. 

If I put a set square on these pics, using the wing as my datum for my 90s degrees then the pylons match the angle, I can't get any true verticals though.

 

 

 

Edited by 71chally
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12 hours ago, Space Ranger said:

All confirmed by engineering drawings and tech manuals.

Well there you go then.  Thanks, Space Ranger.

3 hours ago, 71chally said:

if one is fussy

😄 Fussy? Not me James.  The question of angles only came up because I happened across Sergey’s how to on Airlinercafe’s site.  Not sure I would have changed anything on the kit had it been wrong.  

 

Great photos!  And very helpful.  The issue of the angle dangle has now been pretty much settled.  

 

Here is a photo of the kit wing with an engine tacked on.  Flush and a good fit.  Looks 90 degrees to the wing to me.  Likewise in the plans.  Good enough for me.

 

 

resized_07dac7ae-570f-4a4c-a22f-5089a9fa

 

 

Have dismantled and paint stripped the engines.  I don’t think they should be NMF for Negus and I think I can improve on the fit and details.  Also planning a jig to help get the dihedral correct.

 

Cheers

 

Dennis

 

 

 

 

 

Dennis

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In the interest of full disclosure, and in case no one has figured it out, I point out that I, Space Ranger, am also the gent known as "skyking" (actually "skyking918") on the Airliner Cafe forum whom "DMC" referred to in his original post. Without going into details, the "skyking" moniker predates my joining the Corps of Space Rangers.

Edited by Space Ranger
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Hi @Space Ranger AKA skyking918,

 

I think most of us following this thread had sussed that you had an alias. And, thanks again for you input re the pylon/engine angle.

Most helpful.

 

Cheers

 

Dennis

 

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6 hours ago, DMC said:

Hi @Space Ranger AKA skyking918,

 

I think most of us following this thread had sussed that you had an alias. And, thanks again for you input re the pylon/engine angle.

Most helpful.

 

Cheers

 

Dennis

 

I have so many aliases (alii?) that I sometimes can't remember who I am. And you are most welcome for the engine pylon info.

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1 minute ago, Space Ranger said:

I sometimes can't remember who I am.

😄

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As an aside, I used to listen to and then watch when got our first TV set this program.  Never missed an episode and even, after all this time, I remember that the daughters name was Penny.  A different world back then.

 

resized_4b6aaa43-5587-4b37-95b0-9b2afc55

 

Dennis

 

 

 

 

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2 hours ago, DMC said:

As an aside, I used to listen to and then watch when got our first TV set this program.  Never missed an episode and even, after all this time, I remember that the daughters name was Penny.  A different world back then.

 

resized_4b6aaa43-5587-4b37-95b0-9b2afc55

 

Dennis

 

 

 

 

That aired on Saturday mornings in the US back in the late '50s/early '60s, and I watched every episode. I was working on a history of the show and its making while in graduate school some years back, but the project was abandoned, primarily because all of the principal actors and crew are now deceased.

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  • 1 month later...

Great thread, thanks for the info about the engine alignment angles.

 

I just need to consider the entire wing angle now, where it joins the fuselage. I hadn’t realised the Revell kit was so poor in this area...

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I found this comment on the thread linked in the OP mildly amusing:

 

I think the forces would be enormous to keep an engine of that size tilted like that. Hanging straight down makes more sense to me.

 

If the spars, pylons and attachments struggle to hold the engines a few degrees off plumb due to "enormous" forces then I don't much fancy the structure's chances of either hanging together with the engine at full power or holding together when the aircraft is stressed to its design code mandated ultimate stress limits.

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5 minutes ago, Jamie @ Sovereign Hobbies said:

a few degrees off plumb

Now there's an old school phrase. Took me back to when I actually did check things were plumb with a lead weight and string. I best lie down now, feeling rather ancient.

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