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Monosoupape dummy sort of....


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Hi, I have a quarter scale Sopwith pup that's getting some upgrades, it really needed a spruce up of the nose. I also needed to put a baffle around the engine for cooling.

I have a three-cylinder Saito radial engine in it, and to mimic the nine cylinders of the original, I had to put two cylinders between each cylinder.
The prototype that I'm modeling has a Monosoupape and my idea was to make a look-alike...

A quick effort in Fusion 360 paid off:



I designed it to fit over the Saito radial.

The print turned out really nice, it's high temperature ABS filament.



The test fit was good, but it left room for improvements.


I will get back when the printer is done printing out the revised version.

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Neat a 6/9th scale Monosoupape.😉


I appreciate there are scale issues but the Mono was not the usual engine in the Pup. I believe it was only used in the Home Defence version where despite its considerable cost its extra power allowed the Pup to more quickly reach the altitude of the Zeppelins and Gotha bombers.

Perhaps scale cylinders that match the three IC ones might actually look neater.


Just on an excruciating scale point the Mono Pup cowling was quite complex with four "hooded" vents in the cowl front which I believe matched the air inlet period of the single valve. Note also the four external reinforcements. MonoPupCowl.thumb.jpg.cdf77128cd8bb7fb2984727a78229d93.jpg  

There is a picture of a Pup Mono cowling with 6 reinforcements. Clearly flexing (and fatigue cracking?) of the aluminium "horseshoe" cowling was an issue that was not found in the "full" cowling used on the 80hp Le Rhone.


Of course with electric power the ultimate scale feature is possible with the rotary going round with the prop.

A much smaller scale Pup


The electric motor is the crank case. It even all stays together at full power.

Edited by Simon Chaddock
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Well, not all Monosoupape Pups had that cowling.







My dummy engine version 2.0 that I printed out is now mounted on the plywood baffle to be glued to the engine cover.


 I've only primed it yet, but with some aluminum paint and detailing it will look better.

 The cooling of the engine will be so much better as a result.

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The problem is that I've seen too many restored and/or replica Pups with the "wrong" engine....

I can at least show the judges this:


As proof of motive power so to speak.


Sure, a LeRhone dummy would have been better, but it wouldn't have worked with the Saito radial.

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Only the Clerget rotary engines had twin pushrods. Some 7 cylinder 80hp 7Z engines were fitted to Pups but I have not found any period pictures of such an installation.

The 9 cylinder 130hp 9Bf Clerget was standard for the Camel until replaced by the 150hp Bentley BR1.

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Yes, but I don't think that the clerget had ever been mounted in a pup?

The real engine has to be visible so the cooling stays adequate. And it has two pushrods..... That's a good enough level.

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