Author Topic: Alyn Foundry Sphinx  (Read 17321 times)

Offline RayW

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Re: Alyn Foundry Sphinx
« Reply #105 on: October 28, 2019, 03:24:19 PM »
Thanks to Graham and Jason's help, I now have a healthy spark at the plug without the 4th July fireworks.

Having wired everything up as advised, I still couldn't get a spark to start with. When I removed the 4BA brass screw which holds the Tufnol disc onto the crankshaft, I found that there was a small plug of Tufnol between the end of the screw and the shaft. This was obviously interrupting the circuit between the fixed contact and the body of the engine, via the crankshaft, and probably contributed to the arcing as the current found an alternative path to complete the circuit. 

Once the insulating plug was removed, the circuit was complete and everything worked fine. Unfortunately, when I tried to re-tighten the screw, I found that the thread in the Tufnol had stripped, so I ended up making a completely new disc.
Ray

Offline Jasonb

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Re: Alyn Foundry Sphinx
« Reply #106 on: October 28, 2019, 03:56:58 PM »
I don't actually see why the disc needs to be Tufnol as the other contact is insulated. A metal disc with a protruding round head screw would work well

Offline RayW

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Re: Alyn Foundry Sphinx
« Reply #107 on: October 28, 2019, 04:37:41 PM »
That's certainly an alternative method of doing it and similar to the contact arrangement on my 1/2 HP Stuart where a stud in the face of a gearwheel touches a sprung brass strip.

Ray

Offline Alyn Foundry

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Re: Alyn Foundry Sphinx
« Reply #108 on: October 28, 2019, 04:41:27 PM »
That's great news Ray.

Tufnol was abundant during my time with the Supply industry, it got used!!

Pops and bangs to follow....  :)

Cheers Graham.

Offline Alyn Foundry

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Re: Alyn Foundry Sphinx
« Reply #109 on: November 03, 2019, 02:35:01 PM »
Hi Ray.

How's it going? Are we there yet?   :)

Cheers Graham.

Offline RayW

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Re: Alyn Foundry Sphinx
« Reply #110 on: November 03, 2019, 03:21:10 PM »
Hi Graham,

Nearly there. Just need to make up a temporary base for the test run.
 
Been in the workshop this morning, but mending a bird table and bird bath instead of playing with engines! In those violent winds yesterday, the bird table blew over, smashing its slate roof and breaking the top of our nice old bird bath in half as it fell onto it. Luckily I had some replacement slates so just a matter of cutting them to size and fitting. I am trying to glue the two halves of the concrete bird bath together with Gorilla Weld epoxy, which claims to be suitable for concrete, but I am not optimistic that it will be strong enough, but we shall see.

I will let you know as soon as there are any pops and bangs.
Ray

Offline Admiral_dk

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Re: Alyn Foundry Sphinx
« Reply #111 on: November 03, 2019, 09:06:09 PM »
Quote
I will let you know as soon as there are any pops and bangs.

OK - careful now Ray ...!!!... There are bangs and there are BANGS - and you really don't want the wrong ones  :old:

Hope to hear about the right kind of noises soon - best wishes

Per

Offline RayW

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Re: Alyn Foundry Sphinx
« Reply #112 on: November 04, 2019, 03:13:17 PM »
First signs of life today. Engine firing well when spun over with electric drill, but just not quite running on its own yet.
At one point, I seemed to lose compression, but then noticed that the eccentric push rod was opening the exhaust valve on every stroke. After making various adjustments with the length and height of the pecker arm, I spotted the actual problem.
As explained previously, there are deep and shallow teeth on the star wheel. When the pecker drops into a deeper tooth, it lines up with the exhaust valve, and when in a shallower tooth, it is lifted over the top of the exhaust valve stem.
What had happened was that, following the exhaust stroke, the pecker was dragging the starwheel backwards slightly, as a result of which the wheel was not rotating forward sufficiently for the pecker to move to the next, shallow, tooth.
This was simply remedied by tightening the starwheel retaining nut to increase tension on the spring washer behind the wheel.
I don't know the correct timing for the ignition, but I have set it at just before TDC. Does that sound about right Graham?
I have put a short video of the starting attempts on YouTube at the following link <a href="https://www.youtube.com/watch?v=chB4gkz_ysQ" target="_blank">http://www.youtube.com/watch?v=chB4gkz_ysQ</a>
Ray

Offline Jasonb

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Re: Alyn Foundry Sphinx
« Reply #113 on: November 04, 2019, 03:17:21 PM »
Try it without the demand regulator, the inlet valve should close off the gas between inlet strokes.

Offline Alyn Foundry

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Re: Alyn Foundry Sphinx
« Reply #114 on: November 04, 2019, 05:56:40 PM »
Hi Ray.

Yes, a few degrees before TDC is good.

As Jason has pointed out perhaps the demand valve isn't letting enough gas in, perhaps try and increase the input pressure a little?

Cheers Graham.

Offline Jasonb

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Re: Alyn Foundry Sphinx
« Reply #115 on: November 04, 2019, 06:13:32 PM »
I wonder if the demand valve is opening much at all when it is trying to run on it's own.

There is no form of venturi to create a low pressure area like you get with a carb so the diaphragm won't be getting sucked open much. With the arrangement of holes on the inlet the vacuum created by the piston going down will tend to suck in through the many air holes rather than the single small gas hole.

Without the demand regulator as the piston goes down it opens the inlet valve which will suck in air through the air holes and also uncover the gas hole which will allow gas to flow under the pressure in the bottle.

There should be no need for a demand reg on an engine like this as when the inlet valve is closed that should also shut off the flow of gas, you really only need one on an engine that was designed for liquid fuel where there is no shut off at the needle to stop gas flowing under it's own pressure rather than fuel being sucked in by vacuum.
« Last Edit: November 04, 2019, 06:17:23 PM by Jasonb »

Offline RayW

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Re: Alyn Foundry Sphinx
« Reply #116 on: November 04, 2019, 07:57:41 PM »
Thanks Jason and Graham for the suggestions. I see what you mean about the demand valve.  With the engine spinning quite fast with the electric drill there is probably enough suction but as soon as it slows down, the demand valve is not opening.
I did try various gas pressures, but if the demand valve is not opening, there would still not be enough gas getting through for it to run.
Watch this space for more updates!
Ray

Offline RayW

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Re: Alyn Foundry Sphinx
« Reply #117 on: November 05, 2019, 01:16:21 PM »
The Sphinx awakes!!
As suggested, I removed the demand valve from the gas line and also made a new lighter inlet valve spring. With those changes the engine was on the verge of starting just by spinning the flywheel, but with a little assistance from the drill, it burst into life.
Next job will to be break the engine down for painting and build a suitable trolley.
Thanks to Graham, Jason et al for their help and advice with this project.<a href="https://www.youtube.com/watch?v=2DMoEFhVKSU" target="_blank">http://www.youtube.com/watch?v=2DMoEFhVKSU</a>
Ray

Offline ShopShoe

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Re: Alyn Foundry Sphinx
« Reply #118 on: November 05, 2019, 01:21:50 PM »
Congratulations.

It's always nice to see a new one come to life.

--ShopShoe

Offline Jasonb

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Re: Alyn Foundry Sphinx
« Reply #119 on: November 05, 2019, 01:32:50 PM »
Good to know it was just something simple that was holding it back, should be able to hand start once it has all bedded in.

What we really need is a video of the "interesting" side of the engine ;)

 

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