Steam locomotive stuck in experiment

[Ante]

Hello people
I was started project before one month to make steam locomotive, it is not made for rails just to run around house
I have not previous experience with burners, boilers steam engines but in theory i know enough.
Problem whit this loco is that it has no power to run. So I hope that some experienced people will gave me some advices to improve it.

At beginning I worked just for joy, but now when looks so nice I would like that it has power to run.

Some spec :
burner- copper pipe OD 22mm with 3 holes for wick
boiler- steel pipe turned to approx 1.2mm thickness OD55 brazed 3 copper pipes below boiler for increasing heat conductivity mounted homemade safety valve, steam dome with plug and valve, pressure test 6 bars
steam engine- single acting; with piston valves perpendicular; two cylinders 180 deg;copper cylinder; brass piston; stroke 24mm; piston diameter 16 mm

few pictures:

I assume few problems
not enough oxygen on burner
small heating surface of boiler
lots of leakage on pistons
too big cylinders for this boiler

Please comment, all advices i respect
And sorry for bad English

Salute!
Ante

 

[OrangeAlpine]

I am no expert, but I can see the need for more information.

Does the engine run with no load?
Does it have enough power to move itself?
How much pressure are you using?

Bill

 

[kvom]

What are you using for a throttle? If the boiler just vents directly to the cylinders, then as the water heats, any low pressure steam will just condense in the cylinders.

 

[cncjunior]

What fuel are you running with? Methyl hydrate might be the fuel to use if you aren't already. A pressurized fuel system with ceramic burner might give you more btu. It is too bad that the main boiler part is steel instead of copper. Lagging the copper tubes to the cylinders would help a little. Having a smaller piston would reduce the steam consumption though with a trade off of power. If you could get more heat into the boiler then the pressure would get higher and would compensate for having a smaller piston. If replacing the boiler with copper isn't an option then drilling and welding rivets into it that protrude beyond the outside boiler shell will increase it's surface area.

Daniel

 

[Tin Falcon]

Do you know if the engines even run I am having a hard time seeing or understanding your valving system.

Ok looked again see the valves but are the times and working?
Tin

 

[Ante]

Does the engine run with no load?
Runs like crazy

Does it have enough power to move itself?
On little push it make few cycles an then stops
Or on small descent it start to accelerate

How much pressure are you using?
I dont know exactly (I dont have small pressure gauge) safety valve is calibrated on 1 bar and it opens rarely, I think that burner has no power to build up steam to 1 bar

What are you using for a throttle? If the boiler just vents directly to the cylinders, then as the water heats, any low pressure steam will just condense in the cylinders.
I added throttle valve on steam chest it is not on this pictures

What fuel are you running with? Methyl hydrate might be the fuel to use if you aren't already. A pressurized fuel system with ceramic burner might give you more btu. It is too bad that the main boiler part is steel instead of copper. Lagging the copper tubes to the cylinders would help a little. Having a smaller piston would reduce the steam consumption though with a trade off of power. If you could get more heat into the boiler then the pressure would get higher and would compensate for having a smaller piston. If replacing the boiler with copper isn't an option then drilling and welding rivets into it that protrude beyond the outside boiler shell will increase it's surface area.

I am using 95% Ethanol, I did not have big copper pipe and I have problems with hard brazing (using propane-butan torch)
I was thinking that by reducing cylinder diameter maybe boiler would keep higher pressure

Ok looked again see the valves but are the times and working?
Timing is set to cutoff about 80% of stroke, I don't know is it that too much for model engine.

Are there some drawings for simple propane burner with tank and valve? I think that is first step to get working engine

Il put movie of working engine without load as soon as possible

Thank you for commitment people
Salute!
Ante

 

[kvom]

1 bar (14 psi) is pretty low; I suspect that may be part of the problem.

 

[Mike1]

You say "Lots of leakage on Cylinders" cure that problem and try the engine again, if the cylinders are leaking badly then they are acting as a safety valve which is no good at all.

 

[Neil K]

I'm trying to understand the piston arrangement...

Since there are no crossheads and the cylinder is fixed (not like an oscillator), I'm assuming that there is a wrist pin at the piston end (like in a car) that allows the main rod and the piston to articulate. If so, is the piston long enough to act as a good bearing surface within the cylinder and then is the clearances appropriate (minimum).

If the piston is fast to the main rod, then it will be rocking within the cylinder and must be appropriately radiused. Sealing that arrangement will be quite problematic.

Maybe you could reveal a little more about the pistons?

Neil

 

[Ante]

1 bar (14 psi) is pretty low; I suspect that may be part of the problem.

I measured force needed for pull locomotive and calculation shows me that 1 bar is enough.

You say "Lots of leakage on Cylinders" cure that problem and try the engine again, if the cylinders are leaking badly then they are acting as a safety valve which is no good at all.

In last two days I tried 3 types of piston sealing: O ring ; PA piston ring ; and PTFE tape for sealing pipes. O ring was too tight, I have no experience with making piston rings but piston ring of PA6 is also to hard to move even made loosely, maybe PTFE piston ring will work good but because now is weekend I could not buy it. So temporary solution is PTFE tape twisted in rope and then piston groove is filled with it. That solution works well but it is temporary.

Pictures of piston and throttle valve

except sealing piston i made new engine valves they are tighter so steam loses are smaller.
For test instead of ethanol for fuel I used kerosine for lamps. In first run it has power for slow steaming sometimes it get nice speed. In second attempt when I wanted to do movie I realized that wick is burned out so i need new wick.
Any solution for fast burning wick except poker burner?

Neil as you can see in picture piston is like in IC engine.piston pin 3mm is threaded on M3 on one side and screwed in piston. Two M4 nuts makes distance for connecting rod

At end I think that engine need copper boiler and poker burner

Salute Ante!

 

[cncjunior]

Hi Ante,

The calculations that you have done that says 1 bar is enough maybe right in an ideal world with no heat loss, pressure loss, friction loss or steam leaks. If you could build up higher pressure the loco would be more forgiving of the losses.

As others have said, the piston and connecting rod that you have creates a challenge for friction and steam loss. One way to correct the piston and con rod would be to incorporate a cross head guide and cross head. More parts to make thought. The piston rings that you might put on there will add friction no mater what material you use, The only one that might have better luck would be graphite string. PTFE does expand with steam contact.

The burner wick that I have seen in other locos is more cohesive than the frayed one that is in your burner. That might account for burning out your wicks.

Daniel

 

[OrangeAlpine]

Wondering....

About a longer piston with labyrinth seal. The longer piston would be more stable in the bore (which may be causing your steam loss) and a labyrinth seal should work well with low pressure wet steam. It is also the ultimate low friction seal.

Bill

 

[Neil K]

Thanks for the photos of the piston and connecting rod.

I believe you might have greater luck with a longer piston skirt. The connecting rod will place an angular load on the piston that will tend to bind it in the cylinder. Others have mentioned a crosshead arrangement...that will place the load centrally on the piston but at the cost of additional components. A longer skirt (distance from the conn rod pin to the edge of the piston) will help spread the side load of the piston over a greater area of the cylinder wall. That additional length will be determined by the angle of the conn rod to the piston at the 90° position of the crankpin.

Might be something to look at...

Neil

 

[Orrin]

If your wicks are burning up, I suggest using either coils of fine stainless steel screen or Fiberglas rope of the type that is use for wood stove door gaskets.

Orirn

 

[Ante]

Hello People
Sorry for long time without response, in meanwhile i made some additional parts on loco. It is not yet finished but I made short movie so why not to share it.

http://youtu.be/dQUCqWwFNIA

Salute
Ante

P.S.
and thank you very much to all for advices

 

[MachineTom]

Having fooled with small stationary engines, 1 bar will spin them, with no load. add a jack shaft and some spinning stuff and it barely does the job.

You have the cylinders at 180° that means zero power twice per rev. as one is at TDC and the other at BDC. Because you have single acting arrangement, you have each piston producing no power for about 200°+ of rotation, since there is no flywheel inertia effect, you are stuck with a bad design. You can move the crank pins to a 90° this makes one dead spot of about 100° +.

If you search around you will find only a couple loco's ever built with single acting pistons, and those had gear drives and flywheels.

Redo you calculations and use an effective power factor of 40% at best.

 

[Jyman]

Nice loco, but I would add a fly wheel. It looks like you would have enough room to add one to the rear shaft unseen from the out side of the train.

Or you could add counter weights drilled and pressed into the large drive wheels. But again very nice loco


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