Now THAT'S a Spinner!

[BusyLittleShop]

Spinning the engine helps, but you still need to have cool air coming in. If the engine is spinning inside a box of hot air, the air will be circulating but it won't do much cooling.

True Dana... if the engine were confined inside a box a rotary would
be spinning in its own heat of combustion and exhaust but that is not
what we see on the Morane Saulnier... the designers engineered a gap
between the spinner and cowl to allow a path for cooling air to enter
and at bottom there is no cowl what so ever which is another design
feature to allow the cylinder to exhaust in the exposed air stream...
technically speaking I don't see a possible problem of over heating
rather I see a number of novel measures taken by the engineers to
sufficiently manage precious cooling air...

[BusyLittleShop]

My thought is that the spinner was eliminated due to maintenance issues. It'd be crazy hassle to remove the thing to get at the front of the engine, especially when there's a huge bulkhead on the front of the prop to support the spinner.

Ron Wanttaja

In the time of war leave it up maintenance to find a short cut to a crazy hassle... like install quick fasteners to cowling to get at the engine...

(Its worth noting the chief reason rotarys sported cowls was to divert the Castrol oil spray away from the pilot and onto the bottom of the aircraft)

[Mayhemxpc]

My thought is that the spinner was eliminated due to maintenance issues. It'd be crazy hassle to remove the thing to get at the front of the engine, especially when there's a huge bulkhead on the front of the prop to support the spinner.

Ron Wanttaja

Ron, I think you are probably on target there. When people ask why my plane (O-2A) doesn't have spinners while the civilian 337 (and O-2B) do, I say that when operating in remote locations, on Laterite or PSP runways, spinners just lead to cracked spinner bulkheads and more maintenance. (I am not 100% sure this is true, but former USAF maintenance personnel who worked on the planes agreed with me.)

-- Chris

[Airmutt]

I doubt that the spinner and those deflectors bolted on the back were channeling much cooling air thru that narrow opening. The Morane appears to have been pretty tightly cowled. Don’t think the video of a uncowled rotary engine turning a modern design prop validates any claim about rotary engine cooling.
When Lockheed changed the engine/prop combination for the C-130J it suffered many cooling and ventilation issues. Took a redesign of the oil cooler pan and augmentation system, a change of the beta schedule and interior nacelle ventilation changes to name a few.
There are other examples over where airflow or lack of has adversely effected the performance of turbo chargers, oil coolers etc. and forced design changes.
But I agree with Ron, the maintainers were probably glad when the spinner was officially removed.

[BusyLittleShop]

Here is custom spinner to behold with a tight air gap... 3350 powered RareBear... no cooling problems noted...

[Airmutt]

Oh wow, 3 bladed prop and the white & gold paint scheme - that’s a throw back pic. Didn’t mean to imply that it can’t be done. My comment was to the most likely poor efficiency of the Morane’s prop with the deflectors attached.
Rare Bear is any interesting combination parts and a lot of engineering. Quite the plane for what was essentially started from pile of parts.

[BusyLittleShop]

In 2002 Rare Bear sported a three blade propeller off Lockheed P3 Orion attached to Lockheed Constellation hub but
after back-to-back testing in 2004, a switch was made back to the Aeroproducts four-bladed propeller...

Historically speaking those defectors were history after Garro's Morane was captured and Fokker designed the synchronized firing mechanizum...

[Airmutt]

The blades maybe have been from a P-3 but Lockheed never used a 3 blade setup on the Orion. Early C-130s had a 3 blade configuration which was a Curtiss Electric setup. The Ham Std blades were essentially the same except for the tip shape. The square Herc prop was referred to as the power blade while the rounded Orion tip was referred to as the speed blade.

[Dana]

The blades maybe have been from a P-3 but Lockheed never used a 3 blade setup on the Orion...

Maybe that's why they used Constellation hubs...

[Ron Blum]

Fascinating thread!!!

My guess is that Airmutt (Dave) is correct. BIG spinners are good (streamlines the rest of the airplane). I would guess that the propeller was stopping most of the cooling flow. When the spinner was removed, more frontal area was exposed to get a little more cooling area. Even though it's a huge spinner, it is not very long. The flow (streamlines) probably didn't change a lot with or without the spinner.

Bottom line: Tradeoff between cooling flow and strength of the root section. Solution: Bigger spinner to allow a longer/larger root section and a better blade/blade angle out a little further.

Way cool thread!!!