1895 Otto Vertical Gas Engine

[Alyn Foundry]

Thanks Jason.

By “ Rim fire “ I assume the centre electrode sparks radially rather than to a specific point?

Cheers Graham.

[Jasonb]

No, "Rimfire" is the make of small spark plugs from the US, the 1/4" one uses a 1/4-32UNEF thread as does a RC glow plug

http://sparkplugs.morrisonandmarvin.com/

usual shape not radial discharge.

As you say trying the engine with a sparkplug may be worth a try, should be easy enough to rig up a couple of contacts on the crankshaft somewhere and use lost spark

[Dave Otto]

My thoughts exactly guys, you have to wonder if the low compression and the glow plug don't play well together. Like Graham I don't have any experience with glow plugs except for model airplanes as a kid.
Rigging up a spark plug could help rule out or point a finger at the glow plug.

Dave

[RayW]

Thanks all for the suggestions. I have been looking at lots of videos on Youtube and there seem to be quite a few Otto models running with spark ignition, but I can't see on any of them where the contact breakers or Hall sensors are located. If any of you Otto owners can help, it would be much appreciated.

[yogi]

Ray, as a test set up, I would suggest an inexpensive electronic ignition like this:

https://hobbyking.com/en_us/replacement-complete-ignition-set-for-single-cylinder-gas-engines.html

The magnet for the hall sensor can be placed on the flywheel, and it can be moved easily to adjust the timing.


Yogi

[johanvanzanten]

In this album.  http://www.model-engineer.co.uk/albums/member_photo.asp?a=6778&p=298744   you find my version of the Deutz D2 engine. It has a coil and battery ignition. Notice the breaker point behind the flywheel. The sparkplug ( NGK Cm 6 ) is stuck under the air filter. I have this engine for many years and it's a very good runner.

Best regards,  Johan van Zanten.

[Alyn Foundry]

Hi Ray.

As your Otto is low on the compression front you could easily make a 1/4-40 spark plug by creating a threaded tube and centralising a thin Steel rod with some Epoxy resin.

I’m “ Old school “ when it comes to ignition, many of my engines were fitted with small point sets and a small cam fitted to the crankshaft. The cam being little more than a diameter of Steel with a flat milled on it. I used to drill and tap to 4 BA right in the centre of the flat and that allowed by virtue of a grubscrew rotational adjustment of ignition timing. The condenser ( capacitor ) can be fitted at the remote end of the circuit. For the coil I used older points ignition magneto coils, newer ones are mainly of CDI origin, not suited for this application.

On the upside.... we are meeting at the Anson a week on Sunday, why not bring her over and let’s have a tinker?

Cheers Graham.

[RayW]

Thanks Yogi, Johan and Graham.

Finally managed to get the engine to fire and run for short bursts today. Still needs some tweaking as it only runs quite slowly before eventually stopping. It did pick up to what I would consider full speed briefly a couple of times, so I think it just needs a bit of fine tuning now, possibly to the valve timing.

The underlying cause of my recent problems seems to have been that the glowplug was just not getting hot enough to ignite the mixture. I gave the battery a boost charge today, and with the battery showing 13.2volts the glow plug was really bright. I am using a 12volt motorcycle battery as a power source and it seems that if the voltage drops below about 11.8 volts, that is insufficient to power the plug adequately.

As things are looking more promising now Graham, I don't think that I will bother to bring the engine to the Anson, but thanks for the offer of help. Looking forward to seeing you there.

[Roger B]

What glowplug are you using? Is there a converter between the motorcycle battery and the glow plug? I thought glow plugs were typically 2V to run from a single lead acid cell or 1.5V to run from a NiCad type battery.

[Stuart]

Roger

It could be a glow plug from a Diesel engine pre heat those are 12vdc but by elk they sup some juice

[Jasonb]

It's one from a RC engine and Ray has a glow plug driver to bring the voltage down

[Stuart]

Thanks Jason for the info

[RayW]

With the battery well charged up and the glowplug really hot, the engine is now starting much easier and running at full speed. I still need to play around with the governor to get it hitting and missing correctly.
One big job I have decided to do is to replace the flywheel, which I have never been entirely happy with. In trying to correct a rim wobble when I first machined it, I ended up inadvertently making the rim about 3.5mm too narrow. After re-bushing and re-boring the wheel to get a better fit on the crankshaft, there was still a bit of a wobble, which I decided to try and cure by re-cutting the rim. Unfortunately,due to the fact that the rim was already too narrow, there was insufficient meat left on it to turn any more off, so I have reluctantly admitted defeat and will be picking up a new casting from the Engineers Emporium next week on my way home from the Anson Museum.
Having machined two flywheels on my Wyvern engine with no problem, I don't know what went wrong with this one as everything was machined concentrically with the casting clamped to the faceplate of the lathe.

[RayW]

It seems like the new flywheel job may also need a new crankshaft. Gave the engine a run today, only for the crankshaft joint that had failed previously and been re-soldered, to fail again. The problem is that the joint is pretty tight and there isn't much of a gap for solder to penetrate. In addition, the joint is now contaminated with oil, which may prevent silver solder from adhering. It has already been pinned through the end of the web.
I will have to dismantle everything, then see whether it is repairable or whether I will have all the hassle of making a completely new crank. All very frustrating, just when I had got the engine running at last.

[Jo]

  I know the feeling.

Jo