Author Topic: Bristol 142m-2  (Read 2383 times)

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Offline kitnut617

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Re: Bristol 142m-2
« Reply #30 on: July 06, 2018, 04:52:53 pm »
Having had a quick read of Armstrong-Siddley's long history of failure with in-line radials, with the same issues occurring over & over again, I'm at a loss to understand why they kept at it for so long. :unsure:

I've thought it over too, I've come to the conclusion that it's because it is an 'X' engine. 
Jon will probably come up with the answer but I've noticed that all ""successful"" radials have rows of odd amount of cylinders, even amounts of cylinders on a radial never were successful either and I view "X" engines as being a radial. Now two 'Vee's' using two cranks to make an 'X' is something different in my view ---
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Offline NARSES2

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Re: Bristol 142m-2
« Reply #31 on: July 07, 2018, 02:13:21 am »
Having had a quick read of Armstrong-Siddley's long history of failure with in-line radials, with the same issues occurring over & over again, I'm at a loss to understand why they kept at it for so long. :unsure:

If at first you don't succeed, then ................ You do sometimes wonder if some designers or companies just weren't prepared to let the "B's" beat us ? No other sensible explanation at times.

I can't really comment as I don't think I have a mechanical bone in my body
« Last Edit: July 07, 2018, 02:15:17 am by NARSES2 »
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Offline Old Wombat

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Re: Bristol 142m-2
« Reply #32 on: July 07, 2018, 03:35:18 am »
I've thought it over too, I've come to the conclusion that it's because it is an 'X' engine. 
Jon will probably come up with the answer but I've noticed that all ""successful"" radials have rows of odd amount of cylinders, even amounts of cylinders on a radial never were successful either and I view "X" engines as being a radial. Now two 'Vee's' using two cranks to make an 'X' is something different in my view ---

X-engines are liquid cooled, so basically 2 x V-engines stuck on the same crank shaft. In-line radials were exactly what they say, & air cooled but with no effective means of circulating air around the rear cylinders.

Now, the in-line radial saves a little weight (compared to a standard radial) using that arrangement but at the cost of constantly cooking your rear cylinders. I can think of a few means of cooling those rear cylinders more (or less) effectively but they all cancel out the weight saving & then some.
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Offline 63cpe

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Re: Bristol 142m-2
« Reply #33 on: July 15, 2018, 06:56:32 am »
update time: engine (Bristol Hercules) is in, changed the engine cowling to a leftover stirling part, fuselage was PSR-ed and assembled the wings to the fuselage. Now all puttied and waiting to dry before PSR commenses.

IMG_20180715_125712946 by Buddy Holly, on Flickr
IMG_20180715_125632265 by Buddy Holly, on Flickr

Enjoy your build!

David aka 63cpe

Offline PR19_Kit

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Re: Bristol 142m-2
« Reply #34 on: July 15, 2018, 07:30:02 am »
That's looking more and more stupendous!  :o

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...and I'm not a closeted 'Take That' fan, I'm a REAL fan! :)

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Offline Dizzyfugu

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Re: Bristol 142m-2
« Reply #35 on: July 15, 2018, 07:41:01 am »
Sexy!  :thumbsup:

Offline Tophe

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Re: Bristol 142m-2
« Reply #36 on: July 15, 2018, 08:14:54 am »
I like love it! :wub:
[the word "realistic" hurts my heart...]

Offline kitbasher

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Re: Bristol 142m-2
« Reply #37 on: July 15, 2018, 09:32:10 am »
IMG_20180704_224511197 by Buddy Holly, on Flickr

D'ya mind if I'm 'inspired' by the twin-boomer 'Compire'?
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Offline kitnut617

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Re: Bristol 142m-2
« Reply #38 on: July 15, 2018, 11:23:50 am »

X-engines are liquid cooled, so basically 2 x V-engines stuck on the same crank shaft. In-line radials were exactly what they say, & air cooled but with no effective means of circulating air around the rear cylinders.


So can radials be liquid cooled and the rows of cylinders in-line, see Lycoming XR-7755. But even so, a 12 cylinder X engine can be viewed as a 3-row with 4 cylinders per row a radial, more so if the rods are all connected to a single crank.  And like I said, radials with an even amount of cylinders per row, not one was ever successful
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Offline kitnut617

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Re: Bristol 142m-2
« Reply #39 on: July 15, 2018, 11:24:50 am »
update time: engine (Bristol Hercules) is in, changed the engine cowling to a leftover stirling part, fuselage was PSR-ed and assembled the wings to the fuselage. Now all puttied and waiting to dry before PSR commenses.

David aka 63cpe

Now this is looking very interesting indeed ---
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Offline Old Wombat

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Re: Bristol 142m-2
« Reply #40 on: July 15, 2018, 08:33:01 pm »

X-engines are liquid cooled, so basically 2 x V-engines stuck on the same crank shaft. In-line radials were exactly what they say, & air cooled but with no effective means of circulating air around the rear cylinders.


So can radials be liquid cooled and the rows of cylinders in-line, see Lycoming XR-7755. But even so, a 12 cylinder X engine can be viewed as a 3-row with 4 cylinders per row a radial, more so if the rods are all connected to a single crank.  And like I said, radials with an even amount of cylinders per row, not one was ever successful

Yep, I'd forgotten about the XR-7755 & the Wright R-2160 (& the Salmson B.9) but for some unknown reason Armstrong-Siddeley never even seemed to contemplate the idea of liquid cooling, which meant the rear cylinders were always going to cook themselves.


About why odd vs even:

Quote from: wikipedia
Four-stroke radials have an odd number of cylinders per row, so that a consistent every-other-piston firing order can be maintained, providing smooth operation. For example, on a five-cylinder engine the firing order is 1, 3, 5, 2, 4 and back to cylinder 1. Moreover, this always leaves a one-piston gap between the piston on its combustion stroke and the piston on compression. The active stroke directly helps compress the next cylinder to fire, making the motion more uniform. If an even number of cylinders were used, an equally timed firing cycle would not be feasible.

Quote from: wikipedia
An X engine is a piston engine comprising twinned V-block engines horizontally opposed to each other. Thus, the cylinders are arranged in four banks, driving a common crankshaft. Viewed head-on, this would appear as an X. X engines were often coupled engines derived from existing powerplants.

Quote
Some Vee configurations are well-balanced and smooth, while others are less smoothly running than their equivalent straight counterparts. V8s with crossplane crankshaft can be easily balanced with the use of counterweights only. V12s, being in effect two straight-6 engines married together, are fully balanced; if the V-angle is 60 for 4-stroke or 30 for 2-stroke, they also have even firing.
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Offline rickshaw

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Re: Bristol 142m-2
« Reply #41 on: July 15, 2018, 11:42:05 pm »
Having had a quick read of Armstrong-Siddley's long history of failure with in-line radials, with the same issues occurring over & over again, I'm at a loss to understand why they kept at it for so long. :unsure:

I've thought it over too, I've come to the conclusion that it's because it is an 'X' engine. 
Jon will probably come up with the answer but I've noticed that all ""successful"" radials have rows of odd amount of cylinders, even amounts of cylinders on a radial never were successful either and I view "X" engines as being a radial. Now two 'Vee's' using two cranks to make an 'X' is something different in my view ---

I've been thinking about this comment of yours about the number of cylinders in a "successful" radial engine.  The Japanese had some very successful radials and they all seemed to have an even number of cylinders.  So did the British and Germans.  I suppose it all depends on how you define "successful".
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Offline kitnut617

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Re: Bristol 142m-2
« Reply #42 on: July 16, 2018, 02:34:41 am »
Having had a quick read of Armstrong-Siddley's long history of failure with in-line radials, with the same issues occurring over & over again, I'm at a loss to understand why they kept at it for so long. :unsure:

I've thought it over too, I've come to the conclusion that it's because it is an 'X' engine. 
Jon will probably come up with the answer but I've noticed that all ""successful"" radials have rows of odd amount of cylinders, even amounts of cylinders on a radial never were successful either and I view "X" engines as being a radial. Now two 'Vee's' using two cranks to make an 'X' is something different in my view ---

I've been thinking about this comment of yours about the number of cylinders in a "successful" radial engine.  The Japanese had some very successful radials and they all seemed to have an even number of cylinders.  So did the British and Germans.  I suppose it all depends on how you define "successful".

Sorry Brian, I should elaborate -- I meant odd numbers of cylinders per row, for single row they either had 5 or 7 or 9. Multiply rows would give you an even count of cylinders, 10, 14 or 18, which as you say were used a lot.  An X engine on a common crank is really a 4 cylinder per row radial. There have been some radials that have 4 or 6 cylinders (I've not seen or heard of an 8 cylinder single row radial though), none of these even numbered radials worked properly. JCF had explained it to me why some time ago but I can't remember where he posted it.  Something to do with the firing order.
« Last Edit: July 16, 2018, 02:40:16 am by kitnut617 »
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Offline Leading Observer

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Re: Bristol 142m-2
« Reply #43 on: July 16, 2018, 02:50:51 am »
Having had a quick read of Armstrong-Siddley's long history of failure with in-line radials, with the same issues occurring over & over again, I'm at a loss to understand why they kept at it for so long. :unsure:

I've thought it over too, I've come to the conclusion that it's because it is an 'X' engine. 
Jon will probably come up with the answer but I've noticed that all ""successful"" radials have rows of odd amount of cylinders, even amounts of cylinders on a radial never were successful either and I view "X" engines as being a radial. Now two 'Vee's' using two cranks to make an 'X' is something different in my view ---

I've been thinking about this comment of yours about the number of cylinders in a "successful" radial engine.  The Japanese had some very successful radials and they all seemed to have an even number of cylinders.  So did the British and Germans.  I suppose it all depends on how you define "successful".

Sorry Brian, I should elaborate -- I meant odd numbers of cylinders per row, for single row they either had 5 or 7 or 9. Multiply rows would give you an even count of cylinders, 10, 14 or 18, which as you say were used a lot.  An X engine on a common crank is really a 4 cylinder per row radial. There have been some radials that have 4 or 6 cylinders (I've not seen or heard of an 8 cylinder single row radial though), none of these even numbered radials worked properly. JCF had explained it to me why some time ago but I can't remember where he posted it.  Something to do with the firing order.


Firing order for radial 9 cylinder 1,3,5,7,9,2,4,6,8,1 etc so every other cylinder fires in sequence
LO

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Offline 63cpe

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Re: Bristol 142m-2
« Reply #44 on: July 21, 2018, 12:42:47 pm »
Quote
D'ya mind if I'm 'inspired' by the twin-boomer 'Compire'?

Ha Kitbasher, not not al all! If you need moor picca's I gladly help you out. Could you help me with a livery or maybe a hint for a purpose ( if needed at all  :wacko:)

David