Author Topic: Bruce Atmospheric gas engine  (Read 861 times)

Offline Tonyr

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Bruce Atmospheric gas engine
« 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

Offline Alyn Foundry

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Re: Bruce Atmospheric gas engine
« Reply #1 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.

Offline Tonyr

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Re: Bruce Atmospheric gas engine
« Reply #2 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

Offline Alyn Foundry

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Re: Bruce Atmospheric gas engine
« Reply #3 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.

Online Jo

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Re: Bruce Atmospheric gas engine
« Reply #4 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
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Offline Tonyr

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Re: Bruce Atmospheric gas engine
« Reply #5 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

Offline Tonyr

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Re: Bruce Atmospheric gas engine
« Reply #6 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

Offline Alyn Foundry

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Re: Bruce Atmospheric gas engine
« Reply #7 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.

Online Jo

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Re: Bruce Atmospheric gas engine
« Reply #8 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
Usus est optimum magister

Offline Zephyrin

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Re: Bruce Atmospheric gas engine
« Reply #9 on: August 26, 2018, 08:03:54 PM »
Have a look at these old toys gas engines,


the drawings in the patent would be helpful, I hope...

« Last Edit: August 26, 2018, 08:09:42 PM by Zephyrin »

Offline Tonyr

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Re: Bruce Atmospheric gas engine
« Reply #10 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

Offline Jasonb

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Re: Bruce Atmospheric gas engine
« Reply #11 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.

Online Jo

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Re: Bruce Atmospheric gas engine
« Reply #12 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
Usus est optimum magister

Offline Tonyr

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Re: Bruce Atmospheric gas engine
« Reply #13 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

Offline Alyn Foundry

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Re: Bruce Atmospheric gas engine
« Reply #14 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
« Last Edit: August 27, 2018, 01:27:43 PM by Alyn Foundry »