Author Topic: " Nattie " Revisited.  (Read 7471 times)

Offline tangler

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Re: " Nattie " Revisited.
« Reply #15 on: March 26, 2018, 08:15:28 PM »
Very smart.  I like that.

Rod

Offline Dave Otto

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Re: " Nattie " Revisited.
« Reply #16 on: March 26, 2018, 09:25:45 PM »
Nicely done Graham, I like it when they run nice and slow.

Dave

Offline Ian S C

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Re: " Nattie " Revisited.
« Reply #17 on: March 27, 2018, 02:07:58 AM »
Nice one Grayham, that runs much smoother than some that seem to be in a noisy hurry to do very little.
I like the valve gear , much smoother than most of the cam systems used,One thing I do like is the removal of the requirement of a spring, as this, unless you get it dead right takes up quite a bit of power.  For the shutter on my motors I use a 1/16" thick piece of cast iron on a cast iron cylinder head.
Ian S C

Offline Alyn Foundry

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Re: " Nattie " Revisited.
« Reply #18 on: March 27, 2018, 02:14:18 PM »
Thank you All.

There's no one more amazed than myself! I gave up with Nattie a long time ago. The left hand flywheel spokes are actually polished shiny through many hours of futile spinning!

I think the addition of the extra exhaust valve with a large opening was the " game changer " because if you can't adequately purge the cylinder this has a retarding effect on the piston.

By the way, it doesn't seem to matter how hot Nattie gets, you can fry an egg on it eventually, she just keeps on running!

Cheers Graham.

Offline RayW

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Re: " Nattie " Revisited.
« Reply #19 on: March 27, 2018, 04:05:45 PM »
What a beautiful little engine - quite hypnotic to watch and so smooth. Well done Graham.

Ray
Ray

Offline Zephyrin

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Re: " Nattie " Revisited.
« Reply #20 on: March 27, 2018, 06:11:28 PM »
Very nice engine, and clever shutter mechanism, an excellent runner too, congratulations !
may I have a clue on the rationale for the triangle shaped port of the cylinder head ?

Offline Alyn Foundry

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Re: " Nattie " Revisited.
« Reply #21 on: March 27, 2018, 06:31:13 PM »
Very nice engine, and clever shutter mechanism, an excellent runner too, congratulations !
may I have a clue on the rationale for the triangle shaped port of the cylinder head ?

Hello Zephyrin.

Hmmm, dare I tell you?   :)

The lie? Or the truth?

An accident.... My ancient but very versatile Knight jig borer has nearly 200 thousands of an inch backlash in the table nut. I looked at it a long time ago and a replacement seemed far too complicated a part to make and repair. I live with it! On this occasion I forgot to lock the table and produced a very neatly made diagonal slot! Hard to imagine that such a tiny cutter was able to move a 4 foot long by 10 inch wide table without breaking, but it did. I then proceeded to mill the one side vertically.

The lie would be that it allows a little more heat in on each stroke!   ;)

Cheers Graham.

Offline Zephyrin

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Re: " Nattie " Revisited.
« Reply #22 on: March 28, 2018, 08:34:55 AM »
Quote
it allows a little more heat in on each stroke
i would keep this one...

the point is that it is often reported that a vacuum engine requires a sharp and fast cut off point, obtained with complex shaped cam, but it is not so, an eccentric driven shutter works perfectly well too.

Offline Alyn Foundry

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Re: " Nattie " Revisited.
« Reply #23 on: March 28, 2018, 12:09:57 PM »
Hello Zephyrin.

Indeed, I seem to have put a few " myths " to bed with this engine. All I was trying to do was to make something a little different!

As I mentioned in the video I have always liked the look of the engines built by the National Gas Engine company and at that time, didn't own one. I now have a nice example in the form of a single flywheel, size
" H " the smallest in their range.

Partially inspired by Otto's carrier flame ignition fitted to another Manchester made engine, the Crossley, my shutter evolved.

I'm just very pleased that after such a long period of time my efforts were finally rewarded with a runner. Only one other was built by an old friend, since departed. I've no idea where it went.

Cheers Graham.

Offline Jasonb

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Re: " Nattie " Revisited.
« Reply #24 on: March 28, 2018, 01:29:38 PM »
Graham, did you ever get the Hornsby Akroyd finished, if not now may be a good time while you are on a roll :LittleDevil:

Offline Alyn Foundry

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Re: " Nattie " Revisited.
« Reply #25 on: March 28, 2018, 03:29:55 PM »
Graham, did you ever get the Hornsby Akroyd finished, if not now may be a good time while you are on a roll :LittleDevil:

Ah Jason, full of the Devil....

That was truly the " bane " of my life.

Yes I did almost finish it, never got around to making and fitting the fuel tank sub base with all its windows and writing.

The main problem with the Akroyd was its absolutely random running behaviour. On the very odd occasion it would start and run impeccably, but for the most part its performance was abysmal.

One other engine was built by Dave Allen, he too found the same erratic behaviour and modded the hot bulb and flywheel. These mods completely altered the engine, it would start and run beautifully for hours.
Dave then decided to strip and paint it but after the rebuild this engine hasn't run since, it just won't start!!

After almost 9 months of pattern making and further engineering I had an engine that looked beautiful but I felt that a kit presented to the model engineering movement that didn't work wasn't in our best interest.

Cheers Graham.

Offline NickG

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Re: " Nattie " Revisited.
« Reply #26 on: March 29, 2018, 08:35:52 PM »
Love this Alyn, the scotch yolke and shutter is great and as you say the exhaust in a different direction means not disturbing the flame as much. Guess that means the valve opening events aren’t too critical either? Any reason for the triangular exhaust port?


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Offline Alyn Foundry

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Re: " Nattie " Revisited.
« Reply #27 on: March 29, 2018, 08:42:23 PM »
Thank you Nick.

Just nip up the thread to post 23, an accident occurred!! :)

Cheers Graham.

Offline NickG

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Re: " Nattie " Revisited.
« Reply #28 on: March 29, 2018, 09:09:31 PM »
Ah, that explains it, thanks Graham


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Offline Alyn Foundry

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Re: " Nattie " Revisited.
« Reply #29 on: March 30, 2018, 11:57:28 AM »
As a " by the way " for those that think the Vacuum engine is just a toy?

Attached picture of a Lowne patent vacuum engine.

Cheers Graham.

 

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