Sopwith Camel Exhaust

[Yeoman1942]

I am building a WnW USAS Camel with the 160 HP engine and am getting to the end of painting.

I thought this would be a simple question to answer, but I can't figure out where the exhaust (and the associated staining) for  a rotary engine should go. I know the whole engine rotates, so I assume the exhaust just blows straight into the engine bay, but where does it go? 

 

Looking at the cowl there are two square ports that could be vents other wise there is the large hole at the bottom. 

 

This is a first WW1 build for me, so any advice from the Britmodeller community would be great.

 

Many Thanks

 

Yeoman

 

 

[Dave Swindell]

Yes, the cylinders exhaust into the engine bay, and from there out through the V shapes cutout in the underfuselage between the undercarriage legs.

[Kuro Nezumi]

From what I can tell by watching rotary engines work and by cleaning the planes afterward, the exhaust comes out of the engine valves directly into the air rather than through an exhaust pipe, so staining from the exhaust doesn't occur that often. The used castor oil, on the other hand, will often cake the underside of the fuselage and the undercarriage, (many a clean rag have ended black with oil once I've finished cleaning one plane). My advice would be paint on oil stains, streaks and splatters underneath the fuselage concentrating heavily behind the cowling.

 

Hope this helps.

[wombat]

I seem to recall reading somewhere that camel pilots could be identified by the castor oil stains on one or other shoulder of their flying gear, which suggests an outlet somewhere higher up.

 

Kuro... sounds like you have an interesting job?

[Graham Boak]

Given the prop rotation, any oil coming out would-be flung upwards on one side of the aircraft and downwards on the other, hence any single-sided staining.  However the pilot still got a faceful of the stuff.

Edited January 3, 2020 by Graham Boak
Automatic text correction correction.

[John R]

I have had a quick look at my pictures of the Camel at Old Warden and there was not much evidence of staining possibly because it has only a small number of running hours and it is well looked after.

The only trace I could find was some darkish areas on the underside of the lower wing.

I'll see if I can get some pictures posted - a bit busy at the moment.

[Work In Progress]

3 hours ago, John R said:

I have had a quick look at my pictures of the Camel at Old Warden and there was not much evidence of staining possibly because it has only a small number of running hours and it is well looked after.

The only trace I could find was some darkish areas on the underside of the lower wing.

I'll see if I can get some pictures posted - a bit busy at the moment.

Yes, you don't really get exhaust stains in the sense that you get them on stationary engines with fixed exhausts. What you do get is a substantial amount of castor oil mist almost everywhere in the slipstream. By "a substantial amount", think in terms of around a gallon and a half per hour, and all of it, every drop, gets blown back by the slipstream. 

 

The Old Warden aircraft are only run for very short flights compared to service aircraft, perhaps 12 or 15 minutes at a time (so just a couple of pints, then) rather than a couple of hours, and are wiped down carefully and thoroughly after every flight so you don't see much of it except immediately after landing. Of course because the oil is a total-loss system the oil itself does not have time circulating around the engine to get very black and dirty with running time, in the way that oil blackens in a more conventional aero engine or a car engine. Most of the emissions-based staining on a rotary is therefore the cumulative effects of fairly copious amounts of fairly golden-browny coloured oil. On a dark painted surface this is hard to see by colour and really only visible as a sticky glossiness. On a Camel the most visible accumulations are usually around the leading edge of the lower wings, near the roots and around the centre section, and adjacent lower fuselage surfaces, against the light coloured fabric. The later part of this film shows it pretty well as a Camel flies overhead to land. This is the TVAL one in New Zealand.

 

 

Edited January 3, 2020 by Work In Progress

[melvyn hiscock]

There is often a single hole towards the bottom of the cowl that serves two purposes. Since there is no exhaust pipe, and the exhaust valve just opens to the air, this allows air least some of the exhaust to exit through the hole (although the turbulence inside the cowling and forward speed would complicate that). However, with the exhaust port open at this point it allows the ground crew to prime the engine with neat fuel into the cylinder through the open exhaust.

 

On the Nieuport 28 that flew at OW a couple of times, the engine was controlled by choosing 1,3,5,7 or all 9 cylinders. This is a LOUD engine and at La Ferte Alais it was running on idle, with just one pot firing, with the exhaust going off next to the hole in the cowling. Standing that side of the aeroplane was interesting as it was like someone setting off crow scarers and you could feel the bang across your chest.

 

The 160 Gnome is a monster engine. It gives out way more than 160hp and pilots have been known to have double vision from the vibration. My good mate Stu Goldspink flew the N28, initially from RAF Henley and it could be heard from Old Warden. It was, back then, the only aeroplane the Shuttleworth had had noise complaints about. Stu did a photo session where the camera plane was a 450hp Stearman and the N28 easily out climbed it in 5 cylinders. Stu’s Impression is the engine is grossly underrated and is nearer 500hp!

Edited January 3, 2020 by melvyn hiscock

[Work In Progress]

To be fair a 450 Stearman is more than twice the weight of a Camel, but it's indeed very possible that there's more than 160 HP, it's 970 cubic inches after all, the capacity of three 160 horsepower Lycomings put together!  I doubt one has ever been on a reliable shaft dynamometer, and really given the potential cooling issues I am not sure there's any way of doing that.

 

Mind you, people are always startled by the performance of things with genuinely big props - either old low revving engines that can swing them direct, or geared ones - when their everyday comparison is something with a more modern direct drive engine with, by comparison, a toothpick prop.  It was the same with the Fokker D.VII replicas running 200 hp Gipsy Queens, versus the reliably reported performance of the original D.VII with its nominally less powerful original engine.

 

I remember, back when the Yak-52 first became widely available in the West, various Pitts exponents scribbling out on the back on envelopes and declaring that the standard M-14P had to be putting out 450 hp to make that big heavy draggy machine go up at 2,000 feet per minute at 90 knots. But they were comparing direct-drive small-prop horses with geared big-prop horses, and the two just don't compare like for like. Same sort of effect if you have an engine with enough sheer cubic capacity to deliver its HP at a low enough speed to turn a prop a third of the wingspan of a WW1 fighter.

Edited January 3, 2020 by Work In Progress

[72modeler]

6 hours ago, wombat said:

camel pilots could be identified by the castor oil stains on one or other shoulder of their flying gear,

They were also very regular, as the castor oil ingested precluded the need for any laxatives! 😜

Mike

[Bear Paw]

 

I am building the WNW Sopwith Snipe at the moment and above is a photo from the construction booklet that has been used to show the oil staining on an aircraft on active service. The bottom of the wings are CDL and so the castor oil made very dark and an interesting pattern as it bleeds through the fabric.  

[Work In Progress]

That's a great shot. That's what happens when you fly them for a couple of hours at a time.

[Yeoman1942]

Thanks for all the really helpful replies. 

 

Bags of castor oil staining is definitely the order of the day. I love the simplicity of the engine design. No exhaust, no complicated cooling system ,  just get the whole engine and prop to to rotate around and axis and dump the oil and gasses out into the air. Noisy and inelegant, but it worked .

 

Thanks again to all the Britmodellers for the fabulous posts and photos.

 

Yeoman

[wmcgill]

9 hours ago, Yeoman1942 said:

I am building a WnW USAS Camel with the 160 HP engine and am getting to the end of painting.

I thought this would be a simple question to answer, but I can't figure out where the exhaust (and the associated staining) for  a rotary engine should go. I know the whole engine rotates, so I assume the exhaust just blows straight into the engine bay, but where does it go? 

 

Looking at the cowl there are two square ports that could be vents other wise there is the large hole at the bottom. 

 

This is a first WW1 build for me, so any advice from the Britmodeller community would be great.

 

Many Thanks

 

Yeoman

 

 

Camel (replica) with genuine 160hp Gnome (as used in your USAS model) exhaust/oil staining/weathering can be seen in these photos by Jamo on www.theaerodrome.com

[wmcgill]

Weathering image from the Wingnuts website hints and tips page.http://www.wingnutwings.com/ww/hintsandtips

Edited January 3, 2020 by wmcgill

[wmcgill]

Also from the Wingnuts website

[Yeoman1942]

Thanks Wmcgill. Should have looked not the website. 😀

 

The last image is really helpful They did get properly manky after a decent length of flight

[wmcgill]

Many more excellent WW1 aircraft weathering photos by jamo are also on https://forum.ww1aircraftmodels.com/index.php?topic=2015.0

[Work In Progress]

1 hour ago, wmcgill said:

Also from the Wingnuts website

Urrrrgh. Imagine what that heap must have smelt like

[wmcgill]

6 minutes ago, Work In Progress said:

Urrrrgh. Imagine what that heap must have smelt like

They smell like old model aeroplane engines.

[Work In Progress]

The Old Warden ones smell like old model aeroplane engines ' cause they get cleaned. That one's got to have things living in it.

[wmcgill]

18 minutes ago, Work In Progress said:

The Old Warden ones smell like old model aeroplane engines ' cause they get cleaned. That one's got to have things living in it.

The crashed one might also have a hint of "night soil" odor  

[Kuro Nezumi]

On 1/3/2020 at 10:31 AM, wombat said:

Kuro... sounds like you have an interesting job?

 

I'm a volunteer at the Shuttleworth Collection, cleaning the planes. It can get very messy.

[melvyn hiscock]

On 1/3/2020 at 5:08 PM, Work In Progress said:

.  It was the same with the Fokker D.VII replicas running 200 hp Gipsy Queens, versus the reliably reported performance of the original D.VII with its nominally less powerful original engine.

 

 

The Memorial Flight DVII, an accurately built airframe with the BMW engine is interesting. 185hp from 19.2 litres at 1400 rpm. 

 

As as you say about big props, it it not the same as other ‘replicas’. To begin with you cannot take off at full revs as you run out of rudder. The first time I saw it take off was an eye opener, it sounded like a routemaster bus standing at a bus stop, there was no way it sounded like it was giving enough power to takeoff, as it sounded like it was at idle.

 

We should get our Morane AI flying again soon and that, at least as light as a camel and probably lighter, is going to be interesting with the 160 Gnime that is going in.

 

[Work In Progress]

That will be a case of hold on tight for sure. Can't wait to see it!

Edited January 5, 2020 by Work In Progress