Model Uniflow engine - any plans/kits?

[ripslider]

Hello all.

I was wondering if anyone knows if there are any model sized, but functional, uniflow ( unaflow as another name ) engines available?

Has one every been discussed in either books or something like ME?

Thanks

Steve

[baggo]

Hi Steve,

If we are talking steam, Edgar Westbury described a single cylinder uniflow engine back in ME Vol 100 (1949). This had a bore and stroke of 3/4" and used a poppet valve for the inlet. There were castings available at the time but they may no longer be available. Others may know of more recent designs.

John

[steam4ian]

G'day Steve

Google Elmers engines, Elmer produced a unaflow (sic) design. There are also bash valve engines that are uniflow. Send us a PM and I can send you referrence to a couple of designs.

Regards,
Ian

[ripslider]

Thanks chaps.

The engine on the "Elmers Engine" page doesn't seem - to my novice eyes - to be a uniflow - but this is based on it's description.

Am I right in thinking that the Uni-flow is a very efficient engine? I understood it to be very good in high speed applications, but my reading of the description on the Emlers Engine .pdf seems to suggest differently?

Am I barking up the wrong tree?

Steve

[SteveW]

Guys,

I thought uniflow referred to having exhaust ports in the the cylinder that got uncovered just before BDC. The point being to vent the steam and reduce the effort expelling what's left.

These things were used in flash steam engines and were single acting and could have an awful lot of very aggressive steam going through them.

(But I might be wrong)

[baggo]

Quoting from Edgar's article:

"In full size practice, the Uniflow principle is adopted mainly with a view to economy, which it achieves by way of thermal efficiency. It is not usually a high speed engine, and one of the essentials in it's success is an efficient condensing system. But in model engines, these virtues are not easy to realise in practice, and the principal merit of the Uniflow principle is it's simplicity, as applied to a form of engine capable of producing a high output at high speed.

The true Uniflow has no exhaust valve, but only a steam admission valve, which is often of the poppet or 'drop' type in full size practice. Exhaust is effected by a ring of ports in the cylinder wall, uncovered by the piston at the end of the working stroke. On the return of the piston, the ports are closed early in the stroke, and any steam left in the cylinder must be compressed to a much greater extent than in any other type of engine. It will be clear how important it is that all the steam must be extracted from the cylinder while the ports are open, and a high condenser vacuum is a valuable aid in this respect. The steam admission period is usually short, the greater part of the effective stroke being used for expansive working, and with good design, it is possible to obtain, in a single cylinder, an economy equal to that of a triple expansion engine.


He goes on to say that these engines are best used with very dry and preferably superheated steam at a pressure of not less than 80psi.

John

[steam4ian]

G'day again Steve

I have a file with a design from Popular Science of January 1953.

I don't know how to attach files here so if you wantg to build 2 cylinder double acting launch engine with 1" dia cyllinders drop me a PM.

Regards
Ian

[drjohn]

Sounds to me like a sort of steam 2-stroke

DJ

[durhambuilder]

Is the free plan in this weeks ME a uniflow? (Only this weeks if you subscribe otherwise next week!)

[kneedeepinswarf]

One design is the "Viking" by W.J.Hughes. This was originally published in Model Maker (MM157) but I bought my drawing from ME plans service some time ago. I don't know if the present publishers of ME still list it. This design is actually a semi-uniflow, as it has both a uniflow and a piston valve exhaust.

Lionel

[durhambuilder]

Just checked my free plan and the engines is ET Westbury's corsair, not a true uniflow but a single acting piston valve engine, best check before posting next time!. I have this very hazy recollection of an article in an old model boat magazine where a 2 stroke glow engine had been converted. I may be imagining things here but if I remember correctly it had a spring loaded inlet valve screwed in to where the glow plug was, a small sticky up thing was added to the piston so as it came up to TDC it pushed the valve open to inlet the steam which was then exhausted at the bottom of the stroke through the original exhaust ports. Can't remeber what was done with the original transfer passages though, a new liner may have been made but I wouldn't have though so because the whole concept was being touted as a simple conversion.

[SteveW]

Mar 23, 2009 13:19:51 GMT kneedeepinswarf said:

One design is the "Viking" by W.J.Hughes. This was originally published in Model Maker (MM157) but I bought my drawing from ME plans service some time ago. I don't know if the present publishers of ME still list it. This design is actually a semi-uniflow, as it has both a uniflow and a piston valve exhaust.

Lionel

Blimey! I made a Viking at school and still have it.

[peterhill]

Don't know if this fits here, but i know of a 90HP Baker traction engine, that is uniflow. Should hear it at work, has a unique sound.

peter