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tmuir

One for MM, Building a chicken feed burner

MM I just found this website that describes how a chicken feed burner works.
The benefit of a chicken feed burner is it lets you have your main meths tank above the wicks so would let you have a big meths tank in a tender.
http://www.roundhouse-eng.com/spirit.htm
SPOKESMAN

How top take a simply idea - that works and totally complicate it . . .
tmuir

You only use a chicken feed system if you cant fit the size fuel tank you want in the space you have.
MM wants his burner to last more than 8 to 10 mins so needs to be able to carry more fuel.
Only way to do this on a Mamod is above the wick hight so thats when a chicken feed system comes into play.
SPOKESMAN

One simple rule for engineering and design - keep it simple!
Mamodman123

Looks complicated but I'll think about it Need some time to look over this page me thinks
tmuir

Yes I found it at work whilest waiting for a delivery.
I read it through quickly and then decided I need to print it out and read it again later to completely understand it.
Titan

I would strongly advise against version A or B of their 'chicken feed' design which is unsafe as there is nothing to stop the sump overflowing if you get the setting wrong. In any case A and B are not true chicken feed types, as they do not automatically keep the level in the sump correct. I will see if I can produce a much better diagram of how a chicken feed system works.
Mamodman123

Titan wrote:
I would strongly advise against version A or B of their 'chicken feed' design which is unsafe as there is nothing to stop the sump overflowing if you get the setting wrong. In any case A and B are not true chicken feed types, as they do not automatically keep the level in the sump correct. I will see if I can produce a much better diagram of how a chicken feed system works.


That would be useful titan! thanks
tmuir

Here is a picture of a chicken feed system from 'Model Marine Steam' by Stan Bray.
It has a different wick setup to what we are used to but the principle of the fuel feed is what I'm trying to show.


You open the valve and fuel runs down the delivery pipe into the supply tank or 'sump' as it is sometimes called.
As fuel flows out air is sucked up the air pipe from the sump to replace the fuel that has left the main tank.
When the fuel level in the sump reaches the height of the air pipe it stops air being able to be sucked up it and so creates a vacume in the air pipe which stops more fuel from leaving the resevoir.
This drawing doesnt show it but I'm pretty sure there should be an air hole drilled near the top of the sump tank for the same usual reasons you have a breather hole in any other burner
Mamodman123

I see, very clever, so there is no chance of putting too much fuel into the burner tank?
tmuir

Mamodman123 wrote:
I see, very clever, so there is no chance of putting too much fuel into the burner tank?


Thats correct as long as you dont have any leaks or air holes in the air pipe or main tank. But if you did you would know pretty quick as all the meths would run straight out the wicks when you opened the valve.
Mamodman123

tmuir wrote:
Mamodman123 wrote:
I see, very clever, so there is no chance of putting too much fuel into the burner tank?


Thats correct as long as you dont have any leaks or air holes in the air pipe or main tank. But if you did you would know pretty quick as all the meths would run straight out the wicks when you opened the valve.


If that all poured out then it would be a fireball
tmuir

Well if you had not built it correctly one would hope you would of filled it and opened the valve and waited a bit to check it all worked before you lit it up.
Chris

tmuir wrote:
Here is a picture of a chicken feed system from 'Model Marine Steam' by Stan Bray.
It has a different wick setup to what we are used to but the principle of the fuel feed is what I'm trying to show.

You open the valve and fuel runs down the delivery pipe into the supply tank or 'sump' as it is sometimes called.
As fuel flows out air is sucked up the air pipe from the sump to replace the fuel that has left the main tank.
When the fuel level in the sump reaches the height of the air pipe it stops air being able to be sucked up it and so creates a vacume in the air pipe which stops more fuel from leaving the resevoir.
This drawing doesnt show it but I'm pretty sure there should be an air hole drilled near the top of the sump tank for the same usual reasons you have a breather hole in any other burner


I'm at work, so haven't given it much thought, but if there was an air hold in the top tank then it would no longer be a sealed system and the meths level in the two tanks could try and level out causing major spillage. I think. As I said not given it enough thought yet. Surely it needs a hole somewhere though.
yosa

A hole in the top of the lower tank, above the level of the bottom of the tube from the feeder tank will do it.
Mamodman123

yosa wrote:
A hole in the top of the lower tank, above the level of the bottom of the tube from the feeder tank will do it.


Sounds perfect for my burner!

Well I'd have to have the meths feeding into another hole....
tmuir

On the main tank there obviously has to be a means of filling it too which isnt shown on the drawing, but all this would need to be is a threaded bush and a nut to screw into it.
Titan

I can't see the drawing from the work computer, so I can't comment on it, but I have drawn up a simple diagram which I will upload tonight which I hope will explain everything!!
Mamodman123

Titan wrote:
I can't see the drawing from the work computer, so I can't comment on it, but I have drawn up a simple diagram which I will upload tonight which I hope will explain everything!!


Sounds good Titan! Will look forward to seeing it
Titan

lets see if this diagram helps any better!



Simple principle of operation: when the level in the sump drops below the angled end of the fat vertical pipe at the right, it allows air to travel up the pipe - signified by the bubbles - and fuel flows out of the bottom of the main tank via the valve. When the bottom of the fat pipe is covered again, no air can get in to the main tank, so no fuel can get out. In this way a constant level is maintained in the sump no matter how much fuel there is in the main tank, or how fast the burner is using it. You do need an air vent in the sump, to provide the air which eventually disappears up the fat pipe - I do not know how the previous version would work properly with its air tight lid

For the most efficient operation, the pipe carring the air should be a lot larger in diameter than the pipe supplying the meths, as shown.

The purpose of the stop valve is just so you can fill up without flooding the sump, it should not play any part in regulating flow - it is effectively an on/off switch.

TBH I am not sure that the previous design shown would work particularly well!!!
SPOKESMAN

Too complicated - enough to make you use solid fuel!

(only joking!) Surely gas would be simpler . . .
Mamodman123

Ah now that is a lot simpler Titan! I can see exactly how it works now! I agree about the other one not working as there is no air to travel up the pipe
Chris

Yep, don't see why that shouldn't work, and simple too.
Mamodman123

Chris wrote:
Yep, don't see why that shouldn't work, and simple too.


Yes it does look quite simple when you look at it!
Titan

It would be pretty straightforward to modify an existing loco meths burner - just use the existing tank as the 'sump' and mount the larger tank in the cab feeding in to it.
Mamodman123

Titan wrote:
It would be pretty straightforward to modify an existing loco meths burner - just use the existing tank as the 'sump' and mount the larger tank in the cab feeding in to it.


Well its either this option or one below a tender which would you do?
Titan

I think it is entirely down to personal preference - if I fitted this system to Titan then I would use the tender as the servos for the RC take up the space in the cab. However, I would not get a tender for the sole purpose of housing a meths tank if I did not already have or want one, especially as modifying the existing burner would probably be easier.

Whatever you do, it makes life easier if the sump and tank are on the same vehicle!!!
Steve_S

Very interesting thread... I've often wondered about the details of such a system. It seems simple enough once its explained though, I think it wouldn't be too hard to make one.
Mamodman123

Titan wrote:
I think it is entirely down to personal preference - if I fitted this system to Titan then I would use the tender as the servos for the RC take up the space in the cab. However, I would not get a tender for the sole purpose of housing a meths tank if I did not already have or want one, especially as modifying the existing burner would probably be easier.

Whatever you do, it makes life easier if the sump and tank are on the same vehicle!!!


Modifying the original burner looks do-able as there is space either side of the original burner to hold 2 smaller tanks either side!

Hmmm food for thought
Chris

Think I would go for keeping it all in the cab, seems more simple that way. I don't think the size of the second meths tank need be very large anyway, as you still have a limited supply of water.

Maybe I should shut up though...my meths burner isn't here yet! I'm still on 2 minute solid fuel runs!
Titan

The thing is you do not really want a burner that can outlast the boiler capacity, unless you fit a water top up valve.

I was wondering if it would be possible to fit this arrangement in to the scuttle of a roller/traction engine/steam wagon, and put a water top up valve on the boiler - i am sure you could get some fantatically long runs then!
Mamodman123

Titan wrote:
The thing is you do not really want a burner that can outlast the boiler capacity, unless you fit a water top up valve.

I was wondering if it would be possible to fit this arrangement in to the scuttle of a roller/traction engine/steam wagon, and put a water top up valve on the boiler - i am sure you could get some fantatically long runs then!


I already have a top up valve in Rosa so I shouldn't think it would be a problem.

The same sort of thing should work for the TE1a/SR1a as you said Titan, would get very long runs if you kept filling both up
Titan

Mamodman123 wrote:


Modifying the original burner looks do-able as there is space either side of the original burner to hold 2 smaller tanks either side!

Hmmm food for thought


If you were putting extra tanks either side it would not be a chicken feed system, just a conventional one with extra tanks. Having said that it does sound like a viable alternative - should at least be able to double capacity, if not more!
Mamodman123

Titan wrote:
Mamodman123 wrote:


Modifying the original burner looks do-able as there is space either side of the original burner to hold 2 smaller tanks either side!

Hmmm food for thought


If you were putting extra tanks either side it would not be a chicken feed system, just a conventional one with extra tanks. Having said that it does sound like a viable alternative - should at least be able to double capacity, if not more!


It is a lot simpiler too! may do that, although I like the idea of a tender for it. Which i could still have I suppose
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