I got a question about stuff

[Cyruscosmo]

Hey Mike

Ha Ha! “Clear cut” That is funny right there! If I do decide to wander up the inside straight I will be hauling oil as fuel, not wood, and that kind of trip will be made a long time from now. I need to get her in the water and iron out the bugs before I go playing Christopher Columbus!

Hello Fred! Yeah I was mostly day dreaming about things I still don’t quite have a handle on. And she will have a schooner stem and counter stern. I like the look better than the straight up stem.

I got an email response from Paul at Selway-Fisher. The hull speed for the Edwardian in the configuration I like is around 7.5 knots. Which obviously means cruising at more like 5 knots just as Mike said. I can live with that; I am building this Launch to wander and tinker, not commute.

Ok… so I got some questions for ya Mike. If it is still raining I don’t mind the extra info! Hehe…

You use wood in your boiler so I am thinking you have a pretty good idea of the amount you use on various trips. The boiler I am going to use is the same configuration as Rainer’s because I will be using mostly wood sometimes coal and experimenting with used engine oil.

The reason is I can get hold of all the used oil I can haul away as well as tons of pallets. Pallets are dry as a bone and cut already, so when taken apart they stack very tight. Taking that information into account can ya give me an idea of how much wood you usually carry? Say in a box that is 3’ x 3’ x 3’ and packed. Two boxes that size? Three, four? I am doodling my hull layout and want to get a better idea of the space I need to set aside for fuel.

As for the oil, I have already done burner experiments with used oil in my wood stove in the shop to have a good working knowledge of how to get a very hot burn with no drips or smoke. I will have to figure out how to hook the equipment to the steam engine but I am thinking that will be the easy part.

So Fred on to the eccentrics. I am thinking the reason for two eccentrics is so that either direction the engine turns will have the valves in optimum timing. If the eccentric were say straight up the engine could run both ways provided you have a method of reversing the timing event. But having only one eccentric would make either direction doable although neither would be timed properly. So if it has only one eccentric it is timed to run in one direction optimally although it can still go backwards but not very well. Am I close?

Cheers,
Scott

[fredrosse]

"I am thinking the reason for two eccentrics is so that either direction the engine turns will have the valves in optimum timing. If the eccentric were say straight up the engine could run both ways provided you have a method of reversing the timing event."

ANS: You are correct, for the Stephenson Valve Gear, so common on many reversing applications, the intent is to have one eccentric set for optimum conditions going forward, and another eccentric set properly for reverse rotation. The mechanism lets the operator select either of these settings, and any in-between, that is the general logic for the Stephenson linkage, which works well.

"But having only one eccentric would make either direction doable although neither would be timed properly. So if it has only one eccentric it is timed to run in one direction optimally although it can still go backwards but not very well. Am I close?"

ANS: On first thought you are correct, however many minds have spent many thousands of hours developing valve gear arrangements for steam engines, and many single eccentric valve gears work as well as, or even better than the Stephenson's double eccentric arrangement. My sidewheeler uses "Marshall-Bremme" valve gear, with a single eccentric, and no sliding surfaces in the mechanism (an advantage over the Stephenson's arrangement). Valve timing is very good for this design, as illustrated in the attached graph, which is just as good forward or reverse. Probably the very best harmonic valve gear is the "Joy Valve Gear", which uses no eccentrics, only a pin on the connecting rod for excellent motion, forward or reverse. Many British locomotives used Joy Valve Gear.

[Cyruscosmo]

Hey Fred!

Yes... I got hold of some program off a website that has all kinds of odd valve gear arrangements and it has had my head spinning for a few days now. I found a steam engine listed on a website from England that had the oddest valve gear I had seen. The engine was a Sissons and try as I may I could not find any other pictures of it to figure out how the arrangement worked. That is until I found the program that was written by a guy who has unfortunately passed away. He was a model locomotive builder and had some very very nice looking engines. Anyway the program has taken the mystery out of the valve arrangements and I see what you mean about many different designs.

I have it in mind to build a steam engine that ya just don't see a lot of anymore if any. The Wolf outside admission is the closest to the Sisson gear that I have seen so far. The Joy 1 inside admission caught my eye because it does not have an eccentric. Less friction in the engine leaves more to push the launch. Well maybe, but you get the idea. And it is something different that I have not seen on any launch engine on you tube.

By the way that is a very nice looking Paddle Steamer ya got there Fred, I found a video taken at Lees Mills 2011. I wonder if that is what rush hour traffic looked like at the turn of the century?

So do you know of any engines like the compounds ya see in most launches that use linkage instead of a cross slide, one more lil bit of friction to consider. I have seen a few walking beam examples but that would not fit in the space I have.

Umm really Fred... Rammstein? Dude you got some good taste in tunes!


Cheers, Scott

[Mjolnir]

The 7.5 knots or so sounds reasonable for a top speed for a thirty foot hull. But if you are in a hurry a steam launch is not really the way to go. The engine size you mention sounds reasonable too, eg 3 inch and five inch bores by 4 inch stroke. Note that the stroke does not make a lot of difference to the power, since an engine with a shorter stroke can turn proportionately faster for the same bearing loads. However the higher revving engine would need a smaller propellor which would be less efficient, and also we don't necessarily want an engine where all the moving parts are just a blur.

Rather than worry about horsepower indicated or otherwise, just compare the sizes of boats and engines in the SBA register to see what people are using.

regards
John

[Cyruscosmo]

Hello John

No, I am done being in a hurry, if I wanted something fast I would build a stitch and glue V hull, install an Arnson stern drive and drop in a 454, but I have gone the V8 marry go round for a lot of years and want something new, "something not ordinary".

I will be building this Launch to putt around the waterways in this area and enjoy some places I have never been to and I agree with you on engine RPM; I like to watch a well-built machine function.

I had already decided on low and slow for the engine and prop. I spent some time looking through all the launch information I could find and it left me a bit more confused than when I started. The problem was that I found big launches with single cylinder engines and small ones with big triple engines and I was comparing my experience in gas engines with what I saw. But I am learning more about the peculiarities of steam power and am getting a better feel for the why of the what.

Paul at Selway-Fisher said I could turn a 20-inch prop on that launch so I have been comparing what others have used for an engine and settled on the 3" + 5" x 4". As for the pitch, well I have read enough here to know that will be figured out in the water one mile at a time.

Cheers,
Scott