Author Topic: By Jupiter  (Read 75361 times)

Online Vixen

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Re: By Jupiter
« Reply #165 on: July 18, 2018, 08:43:39 PM »
When I learned to fly in a Cessna 150, there were two controls for cabin heat and carb heat, one sent the heat to the cabin and one sent the heat to the carb for deicing, and they both came from the same source, the exhaust manifold.
Cletus
Hi Cletus,

Do you still remember the bit about applying the carb heat early, while the engine is running sweetly. If you leave it too late and the engine starts misfiring, due to icing, there will not be enough exhaust heat to get you out of trouble.

Mike
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Online Vixen

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Re: By Jupiter
« Reply #166 on: September 24, 2018, 04:21:11 PM »
I got distracted from the Jupiter project by the refurbish / update program on my Austrian EMCO VMC 100 milling machine. Have a look at  the 'It's as simple as ABC or XYZ' thread for the details. When the VMC was working to my satisfaction I was able to sell on 'Old Faithful', my first CNC mill bought some 20 years ago and used on most days since. It built quite a number of engines. I was sorry to see 'Old Faithful' go, but it's VMC 100 replacement is tighter and more capable in all ways. The departure of the old machine made some much needed bench space (for a few days).

Back to the Jupiter build.

The MK VIIIF version of the Jupiter was launched in 1929, it produced 460 hp (340 kW), a powerful engine for it's day. It was the first Bristol engine to use the new forged cylinder heads and a reduction gearbox to drive larger, more efficient propellers. In 1929, aircraft were not yet flying high enough to need a supercharger to boost the power at altitude. Instead, Roy Fedden, Bristol's chief engineer, devised an over- elaborate Induction Spiral to evenly distribute the fuel mixture from the three barrel carburetor to the nine cylinders. The Induction Spiral was a fixed, light alloy casting which directed the flow in a continuously moving spiral from a carb barrel to three of the nine cylinders. It was an impressive feat of pattern making and precision casting and represents a major challenge to reproduce in model scale. It must have been equally daunting in full size.

I briefly considered more lost wax casting. But the overall cost of pattern making, wax mould making and foundry work was prohibitive. A close friend of mine came to the rescue, he produce a Solidworks 3D model of the spiral and made a test sample in extruded filament 3D print using PLA. You may have seen a photo of the first spiral in a previous posting. The first attempt was pretty close but needed some detail changes to the shape and a change in material to withstand contact with gasoline fuel.





This is a view of the 3D model showing the Induction Spiral together with the nine cylinder ports and the three carbutter ports. See how intricately the spiral edges twist between the ports.

We selected a nylon material for it's ability to withstand gasoline contamination while producing a tough, rigid but semi flexible material. The second Induction Spiral with the design changes was printed at Amsterdam University using Selected Laser Sintering (SLS) with PA11 nylon powder. The result was a high quality precision 3D print with fine surface texture and excellent mechanical and chemical compatibility properties.




This is the Laser Sintered nylon powder print. The print still requires some handwork with coarse wet  n dry abrasive paper to smooth the surface texture and to achieve a perfect fit into the crankcase.
I used a smear of olive oil instead of Engineers Blue to locate the points of contact between the Spiral and crankcase. I hate the mess of Engineers Blue.
The wall thickness the Spiral are between 1.0 and 1.5mm





The Induction Spiral fits so neatly inside the rear of the crankcase





This is how the Spiral feeds fuel mixture to one of the cylinders





Looking into the carburettor port





The rear cover, inlet manifold and the central accessories gearbox in place.
The numbers cast on the back of the Induction Manifold are there to tell the maintenance engineer which cylinders relate to which carburetter barrel.  285    396    417

Stay tuned

Mike

« Last Edit: September 24, 2018, 05:44:34 PM by Vixen »
It is the journey that matters, not the destination

Sometimes, it can be a long and winding road

Offline Admiral_dk

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Re: By Jupiter
« Reply #167 on: September 24, 2018, 09:46:42 PM »
The last picture is almost a piece of art Mike  :praise2:

Glad to see you back on this build  :popcorn:

Offline crueby

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Re: By Jupiter
« Reply #168 on: September 24, 2018, 11:15:12 PM »
Very impressive parts!
 :popcorn: :popcorn: :popcorn:

Offline steamer

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Re: By Jupiter
« Reply #169 on: September 24, 2018, 11:16:58 PM »
That is sooooooo awesome Mike....thanks for sharing that!

Dave
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Damned ijjit!

Offline crueby

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Re: By Jupiter
« Reply #170 on: September 24, 2018, 11:38:57 PM »
It must have been an interesting conversation between Roy Fedden and the guy who had to carve the master for making the mold for that spiral!

Offline steamer

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Re: By Jupiter
« Reply #171 on: September 24, 2018, 11:54:17 PM »
It must have been an interesting conversation between Roy Fedden and the guy who had to carve the master for making the mold for that spiral!

I think that's a printed part crueby.


"Mister M'Andrew, don't you think steam spoils romance at sea?"
Damned ijjit!

Offline crueby

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Re: By Jupiter
« Reply #172 on: September 24, 2018, 11:55:59 PM »
It must have been an interesting conversation between Roy Fedden and the guy who had to carve the master for making the mold for that spiral!

I think that's a printed part crueby.
I know - I was talking about when Fedden originally designed the part for the engine back in 1929, as Vixen described in his post earlier today. That one had to be a hand made master for casting.

Online Vixen

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Re: By Jupiter
« Reply #173 on: September 25, 2018, 12:02:07 AM »
Hay Crueby,

I think Feddon may have said to the patternmaker "I want it done to MIL TBD 41 standard this time".

For those who are not that familiar with this old fashioned engineering standard; the letters stood for:

Make It Like The Bloody Drawing For Once.

Mike
« Last Edit: September 25, 2018, 12:07:53 AM by Vixen »
It is the journey that matters, not the destination

Sometimes, it can be a long and winding road

Offline 90LX_Notch

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Re: By Jupiter
« Reply #174 on: September 25, 2018, 12:06:28 AM »
I continue to be blown away by this build. Wow.

-Bob
Proud Member of MEM

My Engine Videos on YouTube-
http://www.youtube.com/user/Notch90usa/videos

Offline Craig DeShong

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Re: By Jupiter
« Reply #175 on: September 25, 2018, 01:19:42 AM »
And this will be hidden inside the engine for no one to see.  What a shame !
Craig
The destination motivates us toward excellence, the journey entertains us, and along the way we meet so many interesting people.

Offline crueby

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Re: By Jupiter
« Reply #176 on: September 25, 2018, 01:28:14 AM »
Hay Crueby,

I think Feddon may have said to the patternmaker "I want it done to MIL TBD 41 standard this time".

For those who are not that familiar with this old fashioned engineering standard; the letters stood for:

Make It Like The Bloody Drawing For Once.

Mike


 :ROFL:    Great acronym!

Online Vixen

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Re: By Jupiter
« Reply #177 on: September 25, 2018, 11:44:10 AM »
It must have been an interesting conversation between Roy Fedden and the guy who had to carve the master for making the mold for that spiral!

Good morning Crueby

Your question deserves a better answer than MIL TBD 41

I have been a member of the Bristol Heritage Trust (now part of the Rolls Royce Heritage Trust) for over twenty years. I know the lead conservation engineer very well , we have scoured the drawing archives to discover that no  drawings of the Induction Spirol have survived, assuming they ever existed. We did discover some layout diagrams (not engineering drawings) which set out the key dimensions and the locations of the cylinder pipes and inlet manifold etc. I reproduced them in model scale. It soon became obvious that the fluid flowing organic three dimensional shape of the Spiral could not be meaningfully represented on a 2D drawing.




Not one of that generation of brilliant engineers who designed and crafted the Jupiter are alive today to tell us how they did it. we can only guess. Today we can create a 3D model using the latest edition of Solidworks. 3D modeling did not exist for another 80 years after the original design work. The lateral cross section through the Spiral (three thin plates which subdivide the space into three equal areas) can be extruded as a toroid (donut) of the correct diameter, while 9 compete twists were applied. 

Given the difficulty in representing the 3D shape of the Spiral in a 2D drawing. one suspects the pattern maker was only ever given the simple layout diagram and a full size crankcase casting covered with chalk marks to show what was required and told to get on with it; make something that fits!!!!. Actually, the Spiral's shape repeats itself nine times, once for each cylinder. So a full pattern may not have been needed. This could also give a clue to how the mould for the aluminium casting was created. My guess was they fitted together nine identical sectors (like the slices of a cake) to form the mould. I also suspect that the raw casting required a considerable amount of hand finishing before it could be fitted to the engine.

There must have been an easier way to connect the carburettors to the cylinders, but Roy Feddon always got things done his way.

Mike
« Last Edit: September 25, 2018, 11:58:34 AM by Vixen »
It is the journey that matters, not the destination

Sometimes, it can be a long and winding road

Offline Ye-Ole Steam Dude

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Re: By Jupiter
« Reply #178 on: September 25, 2018, 12:07:50 PM »
Hello Mike,

Thanks for this complete explanation for the original idea/drawing.

It is hard enough to understand today with the 3D drawings and a completed part, but it seems almost impossible how they were able to produce it "back then". I so admire the creators and builders of yesteryear.

Have a great day,
Thomas
Thomas

Offline steamer

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Re: By Jupiter
« Reply #179 on: September 25, 2018, 12:11:48 PM »
I spent a few minutes thinking about doing that drawing on the board....and got no where...... :lolb:

Yup!    "Just Make it!!!"

Dave
"Mister M'Andrew, don't you think steam spoils romance at sea?"
Damned ijjit!

 

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