Author Topic: Bristol Mercury revisited  (Read 1557 times)

Offline Vixen

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Re: Bristol Mercury revisited
« Reply #15 on: September 06, 2019, 11:33:18 PM »
Hello Per,

You make a very good point about production v simplicity = minimum errors, least time and lowest cost etc.

I believe Henry Ford's design philosophy was "simplify and add lightness". The Ford Motor Company didn't do too badly.

Sir Roy Feddon, Bristol's chief engineer, had an entirely different view, he loved complexity and elaboration in his engines. He could not leave a design alone, he always wanted to change and 'improve' it. He nearly bankrupted the Bristol Aircraft Company, before they eventually sacked him. I have always been fascinated by the man and his over complex engines. That's why I build so many of them.

For a successful business, "time is money", however, when you are retired "time is for pleasure"

Mike
« Last Edit: September 06, 2019, 11:42:29 PM by Vixen »
It is the journey that matters, not the destination

Online Jo

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Re: Bristol Mercury revisited
« Reply #16 on: September 07, 2019, 06:21:03 AM »
For a successful business, "time is money", however, when you are retired "time is for pleasure"

I prefer to think that in retirement that "both Time and Money are finite" the trick is to make sure one doesn't run out before the other and to make the most of both of them  ;)

Jo
Usus est optimum magister

Offline Vixen

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Re: Bristol Mercury revisited
« Reply #17 on: September 08, 2019, 05:47:10 PM »
So back to the plot. It's time to put away the history books and look at progress with the new Bristol Mercury VIII display stand.

The new central display panel will mount all nine cylinders and the crankshaft assembly. Here you can see the crankshaft assembly. The difference in robustness of the master rod compared to the eight slave rods is quite noticeable. The single throw crankshaft is made of two pieces, which are bolted together at the rear by the large maneoton pinch bolt. The mass of the pistons and conrods is counterbalanced by adding weights to the  crankshaft. The weight on the rear half is slightly larger than the front to counteract the added weight of the maneoton bolt. At the front, is the splined coupling which drives the 2:1 reduction gearbox.







I have decided to bolt the lower four cylinders in place on the rear crankcase half and position the other five cylinders outboard, so that the interior details remain visible.







It was Bristol's practice to position the master rod in one of the lower cylinders, number 6. The lower cylinders are always more oily than the others, due to gravity. The master rod does it's own share of the work plus a small contribution of work from each the other eight cylinders and so benefits from the additional lubrication.







This is the new central panel with all nine cylinders attached. The pistons for the five upper cylinders are guided by clear perspex shoes running in radial slots. The whole assembly will rotate to demonstrate the fluid motion of the nine pistons but at the moment it is very stiff. I am trying to avoid the use of any oil, because it dries out over time and is bound to leak, just like any other radial engine.







I am pleased with how this new symmetrical display has turned out. There is still work to be done with the cam gear and reduction gearbox sections but they should not take too much effort. Then everything needs to be taken apart, cleaned dusted and polished before the final assembly.

Mike

« Last Edit: September 09, 2019, 11:46:29 PM by Vixen »
It is the journey that matters, not the destination

Offline Vixen

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Re: Bristol Mercury revisited
« Reply #18 on: September 09, 2019, 08:19:33 AM »
A new topic titled "The other Bristol Mercury engines" has been specially created  for discussions relating to the Mercury emgine's background and history.

Mike
It is the journey that matters, not the destination

Online sco

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Re: Bristol Mercury revisited
« Reply #19 on: September 09, 2019, 12:20:01 PM »
Terrific pictures of the new display layout Mike - would love to see it in the flesh too!

Simon.
Ars longa, vita brevis.

Offline Vixen

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Re: Bristol Mercury revisited
« Reply #20 on: September 09, 2019, 12:37:17 PM »
Hello Simon,

We need to arrange a visit to you up in Brackley.

Mike
« Last Edit: September 09, 2019, 09:02:58 PM by Vixen »
It is the journey that matters, not the destination

Online Craig DeShong

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Re: Bristol Mercury revisited
« Reply #21 on: September 09, 2019, 11:21:36 PM »
Mike

I open ALL your new posts and read and look through them but I usually close them without making a comment.  I do this, not because I have no comment to make, but because they always leave me speechless. 

I have no words to describe the caliber of work I see in your posts, but I do enjoy reviewing them.  Thanks for bringing them here for me (and us) to enjoy.
Craig

Offline Vixen

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Re: Bristol Mercury revisited
« Reply #22 on: September 10, 2019, 08:19:46 AM »
Hello Craig,

Thanks.  :ThumbsUp: :ThumbsUp: :ThumbsUp:

Model engineering is very important to me. It gives me immense pleasure and satisfaction and somewhere to go when life gets tough. I feel lucky to be able to share what I do, with you guys and gals on the MEM forum. It's the membership of the MEM forum who make it such a very special place to hang out.

Mike
It is the journey that matters, not the destination

Offline Johnmcc69

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Re: Bristol Mercury revisited
« Reply #23 on: September 10, 2019, 02:52:34 PM »
 :ThumbsUp:
 Outstanding work Mike! Really going to be a spectacular display!

 John

Offline Vixen

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Re: Bristol Mercury revisited
« Reply #24 on: September 11, 2019, 02:41:22 PM »
Thanks John,

The final part of the Bristol Mercury jigsaw is the propellor speed reduction gearbox, which is mounted at the very front of the engine. The 2:1 reduction is achieved in a compact bevel, epicyclic gear set. The large bevel gear at the front, is rigidly bolted to the bell shaped outer cover and does not rotate. The large bevel gear at the rear is rotated by the engine's crankshaft via the splined coupling. The three smaller bevel pinions rotate the splined propeller shaft at half the speed of the crankshaft. The 2:1 speed reduction allowed a much larger diameter and therefore more efficient propeller to be used. The large diameter thrust bearing at the very front, transmits the whole of the propellers thrust into the bell shaped cover. The engines crankshaft does not see any of the propeller's thrust force.

The normal cruising speed for the Mercury Mk VIII was 2400 RPM, while the maximum speed (at takeoff boost) was 2650 RPM. The actual propellor speed being half of that.






For the 'exploded' display, I did not want to hide the reduction gears within the bell shaped cover, in there, it would have been completely out of sight. I decided to manufacture a completely new perspex front upright, so that the reduction gearbox could be displayed immediately below the bell shaped outer cover.




This is how the front of the new display turned out. A few weeks work has completely transformed the 'exploded' display.
That's my other big radial engine, the 1/3 scale Bristol Jupiter in the background




There are still one or two bits to sort out, but the majority of the changes to the 'exploded' Bristol Mercury Mk VIII display have now been completed. My wife and I are about to depart for a late summer holiday to belatedly celebrate our 50th wedding anniversary. I will quickly finish the Mercury display when we return, then it's back to work on the Jupiter engine.

Mike




« Last Edit: September 11, 2019, 02:45:42 PM by Vixen »
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Offline AVTUR

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Re: Bristol Mercury revisited
« Reply #25 on: September 11, 2019, 03:40:41 PM »
Mike

Have a good holiday. I think you need it after such a tour de force.

AVTUR
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Offline cnr6400

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Re: Bristol Mercury revisited
« Reply #26 on: September 11, 2019, 06:57:36 PM »
Outstanding work Mike, well done!  :ThumbsUp: :ThumbsUp: :ThumbsUp:

Offline Admiral_dk

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Re: Bristol Mercury revisited
« Reply #27 on: September 11, 2019, 10:07:38 PM »
Enjoy the holiday with the missus Mike  :cheers:

I really think you dramatically improved the display of you fantastic build here - before it was almost two not related engines, and now it really appears as a single unit - just slightly "exploded" to allow an inside peak  :whoohoo:

Per

Offline Steamer5

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Re: Bristol Mercury revisited
« Reply #28 on: September 12, 2019, 05:46:39 AM »
Hi Mike

That’s just jaw dropping......

Cheers Kerrin
Get excited and make something!

Offline steamer

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Re: Bristol Mercury revisited
« Reply #29 on: September 12, 2019, 02:08:54 PM »
Thanks John,

The final part of the Bristol Mercury jigsaw is the propellor speed reduction gearbox, which is mounted at the very front of the engine. The 2:1 reduction is achieved in a compact bevel, epicyclic gear set. The large bevel gear at the front, is rigidly bolted to the bell shaped outer cover and does not rotate. The large bevel gear at the rear is rotated by the engine's crankshaft via the splined coupling. The three smaller bevel pinions rotate the splined propeller shaft at half the speed of the crankshaft. The 2:1 speed reduction allowed a much larger diameter and therefore more efficient propeller to be used. The large diameter thrust bearing at the very front, transmits the whole of the propellers thrust into the bell shaped cover. The engines crankshaft does not see any of the propeller's thrust force.

The normal cruising speed for the Mercury Mk VIII was 2400 RPM, while the maximum speed (at takeoff boost) was 2650 RPM. The actual propellor speed being half of that.






For the 'exploded' display, I did not want to hide the reduction gears within the bell shaped cover, in there, it would have been completely out of sight. I decided to manufacture a completely new perspex front upright, so that the reduction gearbox could be displayed immediately below the bell shaped outer cover.




This is how the front of the new display turned out. A few weeks work has completely transformed the 'exploded' display.
That's my other big radial engine, the 1/3 scale Bristol Jupiter in the background




There are still one or two bits to sort out, but the majority of the changes to the 'exploded' Bristol Mercury Mk VIII display have now been completed. My wife and I are about to depart for a late summer holiday to belatedly celebrate our 50th wedding anniversary. I will quickly finish the Mercury display when we return, then it's back to work on the Jupiter engine.

Mike

Epicyclic tooth form!.....wow!    That's unusual for power transmission...at least to me over the last 35 years....  Why that form do you know?

Dave
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Damned ijjit!