Author Topic: " Nattie " Revisited. (Read 7689 times)

Alyn Foundry · « **on:** March 13, 2018, 06:55:48 PM »

Hello All.

There seems to be a lot of interest in Flame licker/gulper engines of late, I'd like to introduce " Nattie " my
National Gas Engine " lookalike "

At the turn of the century I had a " thing " for these engines designing the CHUK range and then followed Nattie, based loosely around the National deep bed type " N ".

The flywheel has its own history, an old friend had managed to acquire an atmospheric gas engine that had been featured in Model Engineer from the nineteen ought period with broken flywheels. He managed to repair them enough to have some replacements cast, that's my role. We liked them so much I had a few extra knocked out.

Many wasted hours later this engine was put to one side as non runner, I'm hoping over the next couple of weeks to change this situation.

It operates just like any other Gulper the front " had " a cover, once ! A slot milled through was covered by a sliding piece of Gauge plate driven by a peg and ' Scotch yoke " gave a too and fro movement. The exhaust was provided by a ball bearing covering a hole into the cylinder.

You'll notice the bore is huge, this is because you get more area for the working pressure to act upon.
Thanks Bob!

My attention will be focused upon making a new cylinder head but more importantly, an improved exhaust, the key to good running.

Cheers Graham.

Jasonb · « **Reply #1 on:** March 13, 2018, 07:18:23 PM »

You are getting as bad as Jo, starting one engine before completing the previous one

Looking forward to following this one along.

Alyn Foundry · « **Reply #2 on:** March 14, 2018, 11:53:57 AM »

Hi Jason.

Well, not actually starting more like finishing!

The crank is of a composite construction using a pair of cast Iron webs borrowed from CHUK. I chose to go Metric with the shafts as ball race bearings are a lot more common in metric sizes. The shafts and crankpin are made from 6 mm diameter Silver Steel/drill rod. I used two ball races in each main bearing housing to improve rigidity.

You can see from the photos that I had messed about with the stroke length.

The connecting rod is simply a length of Silver Steel soldered into a square of Brass with a single ball race press fitted into it. The cast Iron webs were " paired " and drilled to ensure correct alignment. All the parts are fixed using M 3 Allen grubscrews.

The sideshaft is driven by a pair of 1:1 ratio scew gears that I got from HPC Gears LTD.

Cheers Graham.

Perry · « **Reply #3 on:** March 14, 2018, 12:10:43 PM »

Hello Graham, nice one. Connecting rod pin located at the heavier side of the crank webs got my attention. Will you add further counterweight on opposite side?
Regards Perry

Jasonb · « **Reply #4 on:** March 14, 2018, 01:26:52 PM »

Quote from: Alyn Foundry on March 14, 2018, 11:53:57 AM

Well, not actually starting more like finishing!

In that case there is no chance of you getting like Jo

What sort of size is it Graham, does not look that large and I see you have lost a flywheel along the way too.

Jo · « **Reply #5 on:** March 14, 2018, 01:45:37 PM »

Quote from: Jasonb on March 14, 2018, 01:26:52 PM

In that case there is no chance of you getting like Jo

Rectiliner, Hoglet..? ? ? and for someone who does kitchens for a living I would have thought a bit of A7 plumbing would be right up your street

Jo

Alyn Foundry · « **Reply #6 on:** March 17, 2018, 12:00:19 PM »

Good morning All.

Perry.

The main reason for the crankpin being in the counterbalance is that I couldn't move it forward enough,
" half hole " situation. My solution would be to remake a pair of webs once the " right " stroke was found.

Jason.

No, Nattie isn't very big, the flywheel diameter is 4.8 inches. And yes somewhere in the workshop lies the other one. Although Mathew did, with a little help, build a Sterling cycle engine that also had one of those pretty wheels too!

I managed to find a little time yesterday to start on the replacement cylinder head. Amongst my " stash " are many lumps of cast Iron that came from " exothermic " mould feeders. These tubes were placed to act as risers and the nature of the material ensures the Iron remains molten long enough to feed a heavy casting. They measure 50 mm in diameter and by using the end that fed the mould ensures good quality material.

It was at this point I discovered I didn't have a parting off blade. Drat.... Improvisation time....
Luckily I have many pieces of square section HSS, I found a nice length of 3mm and sat it upon a home made mild Steel parallel, squared up, and set to. I was astounded, it actually worked! In fact there was far less chatter. Made a lovely dome!

but that's easily fixed.

The head is a light press fit into the cylinder, next operation will be the flame port slot and shutter guides.

Cheers Graham.

Jasonb · « **Reply #7 on:** March 18, 2018, 05:23:28 PM »

Thank's Graham, that is quite a bit smaller than your usual size but makes it easily to handle. Looks like I could even have the beginnings of one, even got the right size flywheels

Alyn Foundry · « **Reply #8 on:** March 18, 2018, 05:46:06 PM »

Hi Jason.

It would appear so....

But there's a spoke missing in each of them.

I'm contemplating with workshop or sofa at this moment, temperatures hovering around 0 degrees Celsius, unheated workshop....

We'll see.

Alyn Foundry · « **Reply #9 on:** March 18, 2018, 06:51:13 PM »

Well....

Nattie won.... But now suitably ensconced by the fire, cat on lap, that's it for this evening.

Photo shows new cylinder head with the start of the new flame port shutter.

Cheers Graham.

Jasonb · « **Reply #10 on:** March 18, 2018, 07:08:18 PM »

Looks like that is going to slide sideways to open the port like you see on quite a few flame ignition engines

Alyn Foundry · « **Reply #11 on:** March 23, 2018, 01:26:25 PM »

A little further progress....

I managed to find some time to Silver solder a tab onto the end of the port shutter and mill the vertical slot that creates a " Scotch yoke " type of drive.

A triangular shaped port was then milled through the cylinder head and a suitable Brass disc with a central hole made to fit and gently hold the slide in place.

In my opinion the most important part is the exhaust valve. This allows the cylinder to empty the unused air in a different direction to that of the flame port. Most builders will understand and have recognised that the flame position is, not just critical but hyper critical!!
Picture 2 shows a small piece of 2 Thou Shim Steel clamped over the exhaust port.

Just a few more parts and tweaks, I feel a run coming on....

Cheers Graham.

Alyn Foundry · « **Reply #12 on:** March 26, 2018, 07:14:55 PM »

Hello All.

Meet the new and improved " Nattie "

<a href="https://www.youtube.com/watch?v=2eorVwM7n64" target="_blank">http://www.youtube.com/watch?v=2eorVwM7n64</a>

Cheers Graham.

Jo · « **Reply #13 on:** March 26, 2018, 07:34:14 PM »

Well done Graham that runs very nice.

Jo

Jasonb · « **Reply #14 on:** March 26, 2018, 08:11:34 PM »

Very nice indeed.

Runs well considering there is no cooling for the cylinder

tangler · « **Reply #15 on:** March 26, 2018, 08:15:28 PM »

Very smart. I like that.

Rod

Dave Otto · « **Reply #16 on:** March 26, 2018, 09:25:45 PM »

Nicely done Graham, I like it when they run nice and slow.

Dave

Ian S C · « **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

Alyn Foundry · « **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.

RayW · « **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

Zephyrin · « **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 ?

Alyn Foundry · « **Reply #21 on:** March 27, 2018, 06:31:13 PM »

Quote from: Zephyrin 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 ?

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.

Zephyrin · « **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.

Alyn Foundry · « **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.

Jasonb · « **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

Alyn Foundry · « **Reply #25 on:** March 28, 2018, 03:29:55 PM »

Quote from: Jasonb 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

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.

NickG · « **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?

Sent from my iPhone using Tapatalk

Alyn Foundry · « **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.

NickG · « **Reply #28 on:** March 29, 2018, 09:09:31 PM »

Ah, that explains it, thanks Graham

Sent from my iPhone using Tapatalk

Alyn Foundry · « **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.

Alyn Foundry · « **Reply #30 on:** April 07, 2018, 08:15:19 PM »

Hello All.

Whilst at the Anson I picked up ALF, my first ever scratch built flame gulper.

Made from various patterns on hand and some new ones I built this engine 2 decades ago! Not knowing much about them I foolishly made plain bearings for both the crankshaft and big end.

Over the last couple of days I've refitted the engine with ball races....

<a href="https://www.youtube.com/watch?v=hIQ1t_g-dDg" target="_blank">http://www.youtube.com/watch?v=hIQ1t_g-dDg</a>

More to come once the desmodronic cam and follower are fitted.

Cheers Graham.

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Author Topic: " Nattie " Revisited. (Read 7689 times)