Uniflow Engines

[Leslie Williams 1Participant @lesliewilliams1]

Yes Crash and Bang Valves,

And firstly to Quote Andrew,

"I would have thought they were pretty good? Presumably one wants a valve to open quickly, stay open for a time and then close quickly so that maximum steam can be passed in the minimum time. I'm also puzzled as to why the engine linked to worked without a condenser? "

Yes and of course, and I am agreeing with you, that is their strong point. It's just the clunk and bang that they make that I find disturbing.

Richard Trevithick's Loco worked just like this, using a long tappet rod, as did most if not all of the early engines of that day. Including all those so called vacuum engines from Watt's day. They just sound noisy. So I prefer to use a cam with a spring return.

And why the condenser? … Well with simple blow holes for the exhaust, the steam that was left there would have to be compressed, robbing the crankshaft on the return stroke.

Uniflow were the favourite engine for the Flash Steam people, but few had any type of relieve valve like the one the was shown in your link.

All the best, Leslie.

[Leslie Williams 1Participant @lesliewilliams1]

Crash and Bang Values.

[JasonBModerator @jasonb]

Hopefully our member "Windy" will see this. I don't think his engines have condensers and they are good enough to set speed records.

[Leslie Williams 1Participant @lesliewilliams1]

This is a small uniflow designed for model boats, got it from an Ebay seller.

It's not in the best of condition.

Leslie

[Leslie Williams 1Participant @lesliewilliams1]

This thread originally came about because I had mentioned that I had invented a small relieve value which operated on the return stroke, but remained closed on the power stroke, for single acting engines.

Of course I will have to make a model to prove it.

Andrew had sent a link to another unflow engine, also with a spring operated value.

Leslie

[Anonymous]

Let's start by saying that a condenser is not needed in order for an Uniflow engine to work properly. Of course if the exhaust is exiting into a partial vacuum due to a condenser then, as described by Leslie, the exhaust steam should be more completely scavenged. However, compression of any remaining exhaust stream is not always a bad thing. With conventional valve gear some exhaust steam is often left in the cylinder to be compressed on the return stroke. Although the compression uses energy it has two advantages. One, the compressed steam acts as a cushion to reduce the forces in the connecting rod needed to stop the piston. Second, the compressed steam increases in temperature due to the work done on it, which has two benefits. First, it reduces cooling of the inlet end of the cylinder and second it reduces cooling, and possible condensation, of the incoming steam.

It's not obvious what the trade offs are regarding condensers versus compression of exhaust steam prior to admission. It'll be interesting to see how any future models perform.

Andrew

[Old SchoolParticipant @oldschool]

Both my class B (8lb max weight dry) flash steam hydroplanes exhausted into a silencer to meet the noise reduction requirements. If you heard one running you would think it was an internal combustion engine. My engine ran at somewhere around 10,000 rpm to achieve just under 80mph.

Pauls (windy) hydroplane is a class A 16lb max weight.

[WindyParticipant @windy30762]

Posted by JasonB on 28/06/2021 14:47:39:

Hopefully our member "Windy" will see this. I don't think his engines have condensers and they are good enough to set speed records.

I am not good on the theory and had a play with various valve gears to me the poppet valve wins every time in my applications.

There was no condenser.

Found in my early days with K9 I had a massive increase in speed when CR was increased before did 74mph then 96mph.

A friend with a full size flash steamer has an automatic compression pressure release before steam is entered.

Looking at an old Edgar Westbury book on flash steam the Sparton engine is so similar to my record buster and Bob Kirtley's..

There were so many complicated engines in model flash steamers early days relief valves have been used.

A good read if you can find a copy is Doble Steam Cars by J. N. Walton there is a bit about uniflow but was found unsuited for use in a motor vehicle.

A couple of pictures of my latest steamer.

[Leslie Williams 1Participant @lesliewilliams1]

Thanks for Posting a couple of your Photos Windy. I can get a ruff idea of whats going on, but not fully. And I'm also guessing that this is out of a boat for Flash Steam? A lot of these engines favoured Poppet Valves, and don't get me wrong they're also my preferred valve as well, that is for engines operating from boilers, but for Flash Steam where I have heard of astronomical pressures (greater than 1000 psi) the strain on the valve system would be enormous. And anybody who can make a double beat Poppet valve that small, should get a Trophy. But that's all about Flash Steam and those things are powered by very large Petrol Blowlamps.

But to get back to my storey I was simply in the throws of designing a Uniflow Engine which would work from a Boiler, maximum pressure of about 60psi or even less. And with these engines the exhaust is nothing more than a set of blow holes at the end of the stroke. So far all is well. And so far all normal. Now without a condenser, the trapped steam with no where to go, could be compressed on the exhaust stroke, to up 60psi or more, robbing the crankshaft of some energy.

So what I designed was a small valve in the piston which would only open on the up stroke, but now I will need to make a model to prove it. Andrew in the mean time had sent me a link to another guy who had also designed a spring lowed valve, designed to open on the exhaust stroke with access to the outside air, and of course it used a crash valve for the admission.

I might have some diagrams or Photos to add a little later.

Leslie

[WindyParticipant @windy30762]

Leslie,

Those pictures are for a proposed full size wheeled speed attempt vehicle engine is similar but bigger than the model hydroplane one.

I had a go at making a balanced poppet valve but was no good at high rpm.

As far as stress at high pressure on the poppet valve the opening pressure was high and cam followers took a beating but eventually sorted that problem with stellite and solid lubricants.

On the rapid closing of the valve only good quality car exhaust valves were used with a solid head otherwise welded valve heads dropped off.

The amount of preparation with the hydro before going to run it on water was astronomical and a complete strip down after every meeting.

A welcome break this weekend at Melbourne raceway will be watching two jet engine dragsters having a go one my friend helped rebuild Firestorm after crashing at 200mph..

[Old SchoolParticipant @oldschool]

Leslie

Have a look at Frank Jutton,s flash steam engine for TNT that has a piston valve and from memory it has a pressure relief as part of the piston valve. It’s detailed in Experimental Flash Steam book. I have built his engine but struggled with the piston valve seizing. I now have his boat TNT and power plant.

To solve the seizing problem I built a poppet valve engine, my steam was hot it turned the top of the engine blue.

[Leslie Williams 1Participant @lesliewilliams1]

Old School eh!

That sounds alright.

Now I haven't seen this book by Frank Jutton, but I do have Experimental Flash Steam from years ago, and that doesn't have any relieve valves, that I can remember.

I see if I can get a copy of Franks book, or go to the State Library, and have a look there.

And yes I would agree making such a small valve would be a challenge, but I'll have a go at it, after all watch makers had to do more challenging things, and succeeded.

You made a poppet valve for Flash Steam, as I said I just can't imagine the pressures that this kind of valve would place on the valve gear? Some of those engines operated at more than 1000 psi.

[WindyParticipant @windy30762]

Posted by Leslie Williams 1 on 06/07/2021 11:57:15:

You made a poppet valve for Flash Steam, as I said I just can't imagine the pressures that this kind of valve would place on the valve gear? Some of those engines operated at more than 1000 psi.

Here are pictures of my valve and cam follower.

At running temperatures the valve expands 0.012" if clearance not set at 0.013" to 0.014" this is what happens.

I made hairpin valve springs as coil ones annealed when at high speeds.

[Leslie Williams 1Participant @lesliewilliams1]

That's very very nice Windy. I was looking at all the bolts that you have to lock down the cylinder head.

Also looking at your scored camshaft. Tell what kind of temperatures do you think we are looking at here? And do you know, or can you guess what the steam pressure is? I like the little valve too. It's really nicely made.

I been trying to upload a Photo, but I can't find out how to do it. I have a picture of a Petrol Blowlamp which is probably similar to the ones used with the Flash Steam plants.

[WindyParticipant @windy30762]

Posted by Leslie Williams 1 on 07/07/2021 13:37:55:

That's very very nice Windy. I was looking at all the bolts that you have to lock down the cylinder head.

Also looking at your scored camshaft. Tell what kind of temperatures do you think we are looking at here? And do you know, or can you guess what the steam pressure is? I like the little valve too. It's really nicely made.

I been trying to upload a Photo, but I can't find out how to do it. I have a picture of a Petrol Blowlamp which is probably similar to the ones used with the Flash Steam plants.

Have you put your photos in your albums that works for me then transfer them to your posts.

The cylinder head is ground with valve grinding paste to barrels like some full size single cylinder engines are done.

Cam follower has a stellite facing the bluing on the cam was caused by valve clearance being lost normally just bright steel when clearance ok.

It all runs in Rocal Moly paste with no problems.

The valve is a turned down Rover K series exhaust valve with an 8mmØ head.

 

Edited By Windy on 07/07/2021 14:01:19

Edited By Windy on 07/07/2021 14:05:01

[Old SchoolParticipant @oldschool]

Leslie

If you have a look at the Expermental Flash Steam book, on page 171 you will see a drawing of F Jutton,s engine as part of the piston valve it includes to allow the engine to exhaust on the up stroke. It’s quite an interesting engine with the quick return motion to the piston valve.

[Leslie Williams 1Participant @lesliewilliams1]

Ah! … I've just found out how to make an album.

So this is the Blowlamp that I mentioned.

I only fired it up once, it's made by Bassett & Lowke and came off a Marine Engine that I have. By memory it spate out quite a large flame.

Leslie

[Leslie Williams 1Participant @lesliewilliams1]

Right, … now Mr. Old School.

Now page 171 …. yes I can see what you mean. now I see how it works, he has a slotted return crank, I hadn't noticed that before, now that's a good idea, he's also using a cylindrical valve as well, so he's not having any of the problems that came from using a Poppet valve. I've seen a few different designs, but this one is very good. It looks like he's hollowed that valve out, but it doesn't show how he gets the steam into it. The holes at the top are not the answer?

Very good.

Leslie

[Author]

Posts