Fire eater rescue help

[lazylathe]

Hi All,

Well i took in another limping engine! ;D

It appears to be quite well made. Has a graphite piston and ball bearings.
This one is missing a few bits here and there so i made them quickly on the Myford!

It needed a new crank bush and bolt, they were easy to make.

Here is a shot of the actuating mechanism!
Looks like a delrin plunger with a stainless steel pin with a spring underneath it which actuates the gears up front.

Quite neat!


I am looking for some help in making the bit on the front that is controlled by the small gear mechanism.

I will make it from shim stock.
Connecting it is confounding me for the moment!

Anyone ever seen one like this?
If you have i could get the details from the plans on how to make it.

Also need to make a burner for it!
For now i will use the one from my other flame eater.

Thanks for any help!

Andrew

 

[mklotz]

Interesting. I've never seen one with a gear actuated valve before.

If I understand it correctly the blue spring part that's there is a spring to hold down the actual valve plate, now missing. Make a very thin steel plate with diameter slightly larger than the hole in the cylinder. In the center of this plate turn a raised circular tenon that is a close fit to the hole in the spring. Make the new part as light as possible.

 

[lazylathe]

Hi Marv,

Thanks for the reply!
I thought the gears were a pretty neat feature.

That is kind of the way i was going at the moment.
I have taken a very small bolt and ground the head away till paper thin then attached
the shim stock to the spring with a bolt.

Any ideas on which way it should turn?
If i turn clockwise it seems to suck the flame in, while counter clockwise blows the flame away.

Andrew

 

[mklotz]

The valve doesn't really need to be bolted to the spring. All that's needed is a projection on the valve that fits closely into the hole in the spring and prevents the valve from flying away.

The rotation must be such that the valve is just opening when the piston is at TDC or slightly into its descent from that position. It's this sucking action of the piston that draws the flame into the cylinder.

For best operation you may want to polish those scratches out of the cylinder and polish the face of the valve that slides over the cylinder hole.

 

[winklmj]

Cool...post a vid when you get it running.

 

[lazylathe]

Thanks Marv for all the tips!!! :bow:

Just finished with all the mods and it turns over very smoothly without the valve installed.
Had to skin the crank as it was slightly too thick and was binding on the con-rod.

With the valve installed it is a lot tighter and makes a popping noise.

Just need to fire it up and play around with the timing now.

Hopefully will have it running and post a video!
Will keep updating on progress or lack thereof!

Andrew

 

[lazylathe]

Okay, i have hit a stumbling block... ???

I have set the cam to open the valve at TDC or lightly into it's descent.
The valve seats very well against the face and i have lubed it with a tiny bit of fine graphite powder.

As it turns down to complete a revolution the vacuum inside just before it reaches TDC again is too great
and it seems that it cannot gain enough momentum to overcome this.

When spinning it fast by hand it makes a high pitched squeaking sound.

Any ideas on what i should try next?

Andrew

 

[fcheslop]

Hi Andrew,it may be that the valve is not allowing the engine to exhaust easily. As an idea just make a simple blade type valve like Poppins about 2 to 4 thou thick.
Best of luck Frazer

 

[lensman57]

Okay, i have hit a stumbling block... ???

I have set the cam to open the valve at TDC or lightly into it's descent.
The valve seats very well against the face and i have lubed it with a tiny bit of fine graphite powder.

As it turns down to complete a revolution the vacuum inside just before it reaches TDC again is too great
and it seems that it cannot gain enough momentum to overcome this.

When spinning it fast by hand it makes a high pitched squeaking sound.

Any ideas on what i should try next?

Andrew

Hi Andrew,
Do you mean compression rather than "vacuum" in the cylinder before the piston reaches the TDC? If so try reducing the Valve spring pressure if possible and as suggested use a leaf type valve and see what happens. These engines do not have a lot of power despite being loud the less work the piston has to do in exhausting the gases the better.

Regards,

A.G

 

[lazylathe]

Sorry for the lack of technicality with my answers...
The best way I can describe it is this way:

When I turn it over it spins freely.
As soon as I add a bit of force to the spin it stops just before TDC.
What is happening is that as the piston is starting move further
away from the front of the cylinder, just before the valve starts
to open it is trying to draw air into the cylinder and the valve
is getting sucked flat to the hole.

If I loosen the leaf spring anymore the alive does not seat correctly.

Any ideas??
I will mess around some more and try and post a video clip of what
is going on.

Andrew

 

[lazylathe]

Okay i thought a short video might explain a bit better.
Also give you a chance to see if i have it set up in reverse! ???

In the first few seconds you can see the valve opening just after the conrod reaches the top of the crankdisc.
In this position the piston is the furtherest away from the flame.
As it turns more the valve closes and it goes into the compression stroke.

Up to this point it works quite well.
Once it starts to reach TDC again it pops and does not turn over.

If i turn it very slowly it will function but as soon as i spin it a bit faster it stalls.

Any help??

Here is a short clip:

[ame]http://youtu.be/XktMwr2lbmY[/ame]

Andrew

 

[portlandron]

From the angle the engine is at it's hard to see the relationship between the valve movement and the piston location.

On the flame eaters I have built the valve should close just as the piston reaches the bottom (as far away from the valve as it can get) of it's stroke.

The valve should stay closed until the piston is just past the top (as close to the valve as it can get) at which time it should open again.

 

[90LX_Notch]

Andrew,

It looks like the timing is way off. Is that a set screw on the cam in the third picture? If so, move the cam in relationship to the crank. Based on how you are turning it over in video: Start with piston at top dead center (piston by port opening), move it 135 degrees (3/4 of the stroke) and hold it there; set the cam so that the valve is closed. This should get you close.

Bob

 

[fcheslop]

Hi Andrew,as already mentioned the timing looks way out
Good luck
best wishes frazer

 

[lazylathe]

Okay thanks guys!

I will try that tomorrow!!!

And yes i can adjust the timing on the cam via a set screw.

Will keep you updated!

Andrew

 

[portlandron]

Ones you get the valve timing adjusted you need to preheating the cylinder to get this type of engine running.

If that is not done just the little be of moisture that forms on the sliding valve can create enough friction to stop the engine from running.

Also if you are using Alcohol for fuel use only Denatured Alcohol as it gives off less moisture when it burns. It's hard to find in Drug Stores anymore I have found it at paint stores.

 

[Gedeon Spilett]

hi,
your are running the engine in the wrong direction in the video !

if you run the engine in the direction you do it in the video, then the valve should open say 30° before tdc, and stays open to suck flame during most of the "downward" travel of the piston, and the port should be already fully sealed as the piston reaches BDC. Then as air cools, the atmospheric pressure pulls the piston back to TDC but this motive phase rapidly vanishes, as the air is cooled and the pressure equilibrated on the both side of the piston, hence the opening of the valve before TDC to release compression that would occurs otherwise.
btw this geared valve seems unnecessary complex and on the video the port does not open fully.


Zephyrin

 

[lazylathe]

I am using DNA as a fuel source.

And i have some more noob questions!
I do not fully understand TDC and BDC.

If i am correct this is what i think it means:
TDC is when the piston is closest to the head of the cylinder
BDC is when the piston is the furtherest away from the head of the cylinder.

I was fiddling a bit last night without much success running it in either direction.
I cut the valve back a bit more and the port is now about 90% open and it just seals shut.

I am thinking that i have the valve opening too late.
It should open just before the piston reaches the cylinder head to release the pressure and then close sometime after.
It is the sometime after part that i am not sure of.

Please excuse my lack of understanding!
These engines fascinate me and i do not fully grasp how they actually function. I am not an engineer by any means!

Oh and the gear system is what makes the engine cool and different!
If you read through the post you would know that i bought it to try and fix it up and get it running, not my design.

Thanks for everyones help and patience!
I will get it running!! ;D

Andrew

 

[dalem9]

Andrew You are close too being right TDC and BDC Refures to the possition of the crank. When the piston is at the top and the crank is also at the top center of its travel. And the same for the bottem . Hope this helps . Dale

 

[Catminer]

Hi Andrew

Top dead centre
Bottem dead centre

Peter