Model Engine Maker

Engines => From Plans => Topic started by: Tonyr on August 26, 2018, 04:57:16 PM

Title: Bruce Atmospheric gas engine
Post by: Tonyr on August 26, 2018, 04:57:16 PM
Hello

I have been given (loaned) a Bruce AGE.
The engine is almost complete, it was made a few years ago but never completed.
The guy who made it as asked if I could get it going after seeing some of my engines running.
I have looked at the earlier posts on these engines, I notice there are a couple of different designs.
The Bruce engine has what appears to be an inlet valve although the drawings call it an exhaust valve.
Some of the other engines I have seen on YouTube have another valve in the cylinder head.
Does the engine operate without an exhaust valve.
From what I have read they are difficult to get to run on Propne, does anybody have any experience with this.

Thanks

Tony
Title: Re: Bruce Atmospheric gas engine
Post by: Alyn Foundry on August 26, 2018, 06:20:46 PM
Hi Tony.

I've had a little,  ;) experience with these types of engines but more from the turn of the 19th century.

First are you able to post some pictures of the engine for us.

I have a Leek number 3 and that has two mechanical valves. One exhaust and one fuel. The third valve is open to atmosphere, as the engine pulls fuel, air mixes through this open valve. As the piston reaches and opens the ignition port an open flame ignites the mixture. The resultant expansion of burning fuel and air closes the valve and forces the piston to the bottom of the stroke. The whole of the return is the exhaust stroke. The cycle then repeats.

There's a few here that have more experience with your AGE and some have had success with Propane gas as the fuel. Stopping the ignition flame blowing out was my headache, never got it sorted.

Cheers Graham.
Title: Re: Bruce Atmospheric gas engine
Post by: Tonyr on August 26, 2018, 06:51:02 PM
Hi Graham

Thanks for the reply.
This engine has what looks to be an atmospheric inlet valve and a cam operated gas valve.
I presume it works like a flame gulper on the return stroke.
I have found a few videos of similar engines running.
I hope to use Propane due to its availability.

Tony
Title: Re: Bruce Atmospheric gas engine
Post by: Alyn Foundry on August 26, 2018, 07:26:13 PM
Hi Tony.

No it is very different to a flame gulper principle. Your engine runs by virtue of expansion over a quarter of a stroke.

Let's start at TDC. Piston moves backwards drawing in both fuel and air. This mixes in the cylinder as the piston continues towards the ignition port. As the port opens an external flame ignites the mixture causing massive expansion, ( power stroke ) the piston races to the bottom of the cylinder. From BDC the whole of the energy stored in the flywheels carries the piston to TDC and the cycle is repeated.

I can't see any form of mechanical exhaust in your picture do you think the builder forgot to fit it?

Cheers Graham.
Title: Re: Bruce Atmospheric gas engine
Post by: Jo on August 26, 2018, 07:33:39 PM
The Exhaust valve is that thing sticking up at the "head" end of the cylinder. The inlet valve is activated by the side shaft.

I suggest you try to get it running by replacing the ignition port with a glow plug. Once it runs like that you can then have fun trying to get the engine to run without blowing out the flame  :)

Jo
Title: Re: Bruce Atmospheric gas engine
Post by: Tonyr on August 26, 2018, 07:34:40 PM
Hi Graham,

There is no other valve on the drawing.
There are videos of engines without the exhaust valve running.
Thatís why I thought the return (exhaust) stroke was similar to the flame gulper.
I understand the power stroke operation but there is no exhaust valve.

Thanks

Tony
Title: Re: Bruce Atmospheric gas engine
Post by: Tonyr on August 26, 2018, 07:38:52 PM
Jo,

The valve on the side is the gas inlet valve.
The valve at the top is called the exhaust valve on the drawing.
It looks more like an inlet valve, I canít see how it would operate as an exhaust valve.
It opens by the suction of the piston.

Thanks

Tony
Title: Re: Bruce Atmospheric gas engine
Post by: Alyn Foundry on August 26, 2018, 07:40:48 PM
Well, you live and learn....

All I can say is " it's a wonder they run at all " !!

It must be a nightmare of a task to set up that top valve then? On my engine it " hangs " open and is blown shut on the power stroke.

Cheers Graham.
Title: Re: Bruce Atmospheric gas engine
Post by: Jo on August 26, 2018, 07:43:00 PM
The Exhaust valve also provides for air intake  ;), yes the one on the side lets the gas in.

Try timing it so that the gas valve opens about 1/16" after TDC.

Jo
Title: Re: Bruce Atmospheric gas engine
Post by: Zephyrin on August 26, 2018, 08:03:54 PM
Have a look at these old toys gas engines,
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the drawings in the patent would be helpful, I hope...

Title: Re: Bruce Atmospheric gas engine
Post by: Tonyr on August 26, 2018, 09:03:12 PM
Hi Zephyrin
Thank you for the videos and the patent info.
The engine I have is similar to the bottom video.
The engine in the patent has a cam operated valve.
The valve on my engine is not cam operated, so is slightly different.

Jo, when I was discussing the engine with the guy who owns it we thought the valve might
double as inlet and exhaust.
If this is the case how does it open for the exhaust.
It has a spring closing it.
I have read the limited instruction which came with the drawings but they make no mention of the valve.
Any info will be greatly appreciated.

Thanks

Tony
Title: Re: Bruce Atmospheric gas engine
Post by: Jasonb on August 27, 2018, 07:18:41 AM
I think the weak spring is meant to go on the valve cap and bear against the bracket holding it open. This way the valve is held OPEN so air can be drawn in, it then fires and the expanding gas closes the valve for the power part of the stroke, the pressure then drops off and the valve is pushed open by the weak spring allowing the spent gasses to exhaust.

happy to be proven wrong.
Title: Re: Bruce Atmospheric gas engine
Post by: Jo on August 27, 2018, 08:09:18 AM
The Exhaust valve retainer (Part 22) is missing from that engine, which would give the spring something to push against. The brass wire spring (part 20) on the air/exhaust valve is only 0.015" thick so it would not offer much force.

Jo
Title: Re: Bruce Atmospheric gas engine
Post by: Tonyr on August 27, 2018, 09:22:53 AM
Jo / Jason

That makes sense.
Thanks for the help.
I will let you know if (when) it is running.

Tony
Title: Re: Bruce Atmospheric gas engine
Post by: Alyn Foundry on August 27, 2018, 12:16:02 PM
So, to recap.

The vertical valve at the front top of the cylinder doubles as inlet and exhaust?

I wonder if springs are a good choice. A housing that supported the valve stem with an adjustable weight would keep the valve head in the open position until blown shut. The little weight would then reopen the valve for the exhaust stoke.

The spring fitted on my engine is merely the bottom position stop this could easily be replaced by something fixed.

Jo mentioned in a previous post about the use of a " glow plug " to fire the engine initially. I " reengineered " a 10 mm spark plug to fit the 1/8" BSP port for mine. A small cam on the sideshaft operated a buzz box.
It made for a very reliable exhibit on the rally field.

Cheers Graham.


As a footnote I remembered I opened a thread about my Leek engine here.

http://www.modelenginemaker.com/index.php/topic,7414.msg158513.html#msg158513
Title: Re: Bruce Atmospheric gas engine
Post by: Tonyr on August 27, 2018, 04:59:35 PM
Hi Graham.

Thanks for the info.
I will try it with the flame ignition to start with.
If that gets too stressful I will look at the alternatives.

Tony
Title: Re: Bruce Atmospheric gas engine
Post by: Alyn Foundry on August 27, 2018, 05:52:07 PM
You're welcome Tony.

It proved to me that I don't know everything about the " new " additions that have come from the same stable!

If you find a foolproof method of flame ignition please let us know, I'd be one of the first to implement it.

Cheers Graham.
Title: Re: Bruce Atmospheric gas engine
Post by: Tonyr on September 20, 2018, 07:13:30 PM
Hello,

I have a question.
Has anybody ever seen this model of engine running on Propane, Butane
I have completed the build and tried to get it running.
I am using gas from a blow lamp canister, a Propane Butane mix.
I can get it to fire but not run.
I have moved the valve from the top of the cylinder, to the cylinder head as in the other engines on this thread.
This is an improvement, but not enough.
As Graham experienced the flame blows out.
I used a blow lamp directed at the ignition hole, this doesnít blow out.
If I turn the flywheel with my finger it fires every stroke.
There is not enough power to keep the engine going under its own power.
The engine is as free as it can be but is quite heavy.
Do these engines run on Propane Butane or am I wasting my time.
Thanks

Tony


Title: Re: Bruce Atmospheric gas engine
Post by: Jo on September 20, 2018, 08:00:09 PM
Have your tried it with a glow plug?

These engines should be run on coal gas which has a wide ignition range. Propane/Butane are more fussy, a glow plug will let it ignite when it wants to.

I was going to fit two flywheels on my engine  ;)

Jo
Title: Re: Bruce Atmospheric gas engine
Post by: Alyn Foundry on September 20, 2018, 08:09:08 PM
Hello Tony.

I only ever used plain Propane to run mine with. We discovered that Butane wouldn't ignite on our hot tube models that we produced, but that's a different story.

I'm not sure about the mix of the two fuel gasses but heat is heat and with the correct fuel to air ratio you should have a rapid expansion occur.

I wonder if by moving your valve from the vertical to horizontal you might be impeding the exhaust part of the stroke? Having been told by Jo that this valve hangs and acts as both inlet and exhaust, is it being pushed shut after the expansion?

The only other factor that I can comment on is the fuel/air ratio. Both these gases have a high calorific value but are rather slow burners compared to the likes of Hydrogen etc. Are you able to finely adjust the flow? I'd suggest fixing your blowtorch and rotating the engine whilst slowly increasing the volume of gas to the inlet valve. You should arrive at a point where the engine starts really popping, that would be the optimum mixture.

Cheers Graham.
Title: Re: Bruce Atmospheric gas engine
Post by: Tonyr on September 20, 2018, 09:02:52 PM
Jo
I havenít yet tried a glow plug.
The engine will fire reliably with the blow lamp at the ignition hole.
It doesnít have the power to spin the engine.
The engine has two flywheels, I tried it with one removed also.

Graham

I have considered that the exhaust isnít working properly.
At present there is no spring fitted to keep it open, that is the next test.
I think it is impeding the exhaust to an extent.
I have also varied the distance the valve opens.
It does open and close better in the horizontal than vertical.
I have set the gas flow exactly as you say and it does fire on every stroke reliably.
If I increase the pressure I need to spin it faster, I presume this is due to the time the gas valve is open.

I will fit the spring and maybe try Propane without the Butane.
I will let you know if it improves the runningí.

Thanks for the ideas

Tony
Title: Re: Bruce Atmospheric gas engine
Post by: Roger B on September 21, 2018, 07:52:46 PM
Coal gas (town gas) had quite a high hydrogen content that was easy to ignite with a hot tube, propane and butane are harder to fire.
Title: Re: Bruce Atmospheric gas engine
Post by: Tonyr on September 26, 2018, 08:29:44 PM
Hello.
I have some success.
The engine now runs.
I have to hold a small blow lamp near the ignition hole but it runs fine like this.
The pilot light blows out when it fires with the original design.
I am going to look at the design of the ignition hole and make an extra pilot light to relight the original one when it blows out.
How do I attatch a video to the post.
Thanks for the help.
Tony
Title: Re: Bruce Atmospheric gas engine
Post by: NickG on October 21, 2018, 07:52:57 PM
Interesting stuff, Iíve  never seen one of these running, noticed on the Bruce site that it says acetylene is the best fuel to use, tricky with propane.

Think you need to upload the video to YouTube then paste in the link.


Sent from my iPhone using Tapatalk
Title: Re: Bruce Atmospheric gas engine
Post by: Zephyrin on October 21, 2018, 10:17:55 PM
Hi,
as the opening of the ignition port occurs during the downward stroke, one would have expected that the pilot flame is at first aspirated before being blown by the explosion... maybe the ignition port closes too late, the spring being too hard ?
Title: Re: Bruce Atmospheric gas engine
Post by: Tonyr on October 23, 2018, 05:38:57 PM
Thanks for the replies
I will look at putting it on YouTube when I get a bit of time.
I am busy decorating at present.
With regards to the flame going out.
You are correct it goes out twice, once when the gas is sucked into the engine and once when it fires.
I am going to change the arrangement of the gas pipe.
I will fit another flame to re light the main one when it goes out.
The second flame or maybe both flames will be will be supplied from a separate supply pipe than the fuel gas which gets sucked into the engine.
Hopefully it will be ok with both gas supplies fed from the same gas canister.
It will be a week or two before I can get back onto it.
Busy in the house and trying to keep up progress on my Austin Seven engine which came to a halt over the summer.
Tony
Title: Re: Bruce Atmospheric gas engine
Post by: Tonyr on November 30, 2018, 09:00:21 PM
Hello.
I have found time to get back to the engine.
I have made a couple of changes to the original design.
The engine will now run.
As you can see from the video it still needs a bit of modification.
As I mentioned earlier the flame goes out when the gas valve opens and then is blown out when the engine fires.
I tried fitting another flame fed from the same gas pipe but it went out just the same.
As you can see I have used a small blow lamp to relight the flame.
It could be done with a second gas jet but it would probably need to be supplied from a second gas source.

Tony

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Title: Re: Bruce Atmospheric gas engine
Post by: Tonyr on December 01, 2018, 07:03:43 PM
Hello,

Here is another slightly better video of the Bruce Atmospheric gas engine running

Tony
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Title: Re: Bruce Atmospheric gas engine
Post by: NickG on December 01, 2018, 07:38:46 PM
Well done Tony, by the sounds of it that is one of the most difficult engines to get to run! Itís certainly different and Iíve never seen another running.

Regarding the flame, would it run just with the blow torch flame at that angle? Could it be a flame placement issue?

Nick


Sent from my iPhone using Tapatalk
Title: Re: Bruce Atmospheric gas engine
Post by: Tonyr on December 01, 2018, 08:40:16 PM
Hi Nick,

I think it would run with just the blow torch.
The flame needs to come from a different supply than the gas for the cylinder.
When using the same gas the flame goes out when the gas valve opens, I think it drops the pressure in the pipe.
It would probably work a bit better with a gas regulator as well.
I just had it pipes from the nozzle of a blow torch off a gas canister.
The engine doesnít belong to me, I just wanted to prove it would run.
If it was mine I would probably spend a bit more time on it.

Thanks

Tony