" Nattie " Revisited.

[Alyn Foundry]

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]

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

Looking forward to following this one along.

[Alyn Foundry]

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]

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]

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]

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]

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]

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]

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]

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]

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

[Alyn Foundry]

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]

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]

  Well done Graham that runs very nice.

Jo

[Jasonb]

Very nice indeed.

Runs well considering there is no cooling for the cylinder