The Steamboating Forum

The SBA is in the process of reviving the Taylor engine designs and will be presenting details of the available castings etc. at their AGM on 21st March.
Regards
Jack

Jack,

That is good news- I am only assuming from the fact that it is yourself that has notified us, but will the new casting sets incorporate any of your modifications in the drawings?

Greg

Greg,
Yes I have so far done a set of drawings for the most popular 2.5 twin.
Regards
Jack

Brilliant, such a lovely little engine- let's hope we see some more being made soon. Thanks for your hard work too!

Greg

Jack,
Its good news that the Taylor Engines will be a available.

Do you have any idea which engines the SBA plan to sell castings for.?

I have had a good look on the net & can't find castings available for a 4" x 4" single, & looking at the SBA Register by Engine Design, the Taylor Engines didnt go that large, (although their was a 2 3/4" + 4 1/2" x 4 1/2").

Do you know of any 4 x 4 's .?

Martin

Martin,

The only 4" x 4" twin in production is to Roger Mallinson's design, built by Kevin at Manor Farm Engineering.

A twin of that size will power a very large boat, have you got a project in mind?

Greg

A square cylinder dimensioning is a bit unusual. It seems most steam cylinders, the bore is about 75% of the stroke. I think it has to do with getting more work out of the steam by volume.

-Ron

Folks,
Its very disappointing that the SBA made no reference to this project at their AGM.

Taylor had castings for a 3.5 + 3.5 x 4.0 twin and a compound version, I fitted one to the new boat Bluebell, and it is a very good engine (with my mods).

Regards
Jack

Hi Jack,
Yes, with not a great deal to choose from in the way of available castings, it would be good for all steam boaters to have another option to power their boats. Might even see more boats around if their were more engine options

I have been slow replying as I have passed the plans (below the waterline) onto a propeller manufacturer asking for him to determine the power (and prop size, etc) required to attain hull speed. Then I will look for a suitable engine, and match a boiler to the engine.

I can't see it making any difference with the following question, but the boiler pressure is 150 psi.

If possible, Can you give me some idea how IHP and BHP are related in a ratio.? i.e. x number IHP = 1 BHP.
(I understand how both horsepower's are calculated). I am thinking that it may depend on a few factors, but an approximation would be great.

Ron, yes you are right, thanks for the heads up on the Bore and Stroke difference.

Thanks Martin

Jack is more qualified to answer this but more than one explanation can sometimes help.

A horse power is a horse power. There are no variations in the definition. 550 ft. lbs. per second. Period. Or 746 watts.

Where you measure it is the confusion point. There are losses and some of the ways of measuring it can be confusing.

When measured with a brake, traditionally with a sort of predecessor of an automotive emergency brake and often using wood blocks, the numbers are as accurate as the instruments involved and there are few qualifications. In automotive practice there are all sorts of cute cheatings such as disconnecting auxiliaries like electrical accessories and cooling fans to inflate the numbers. This started with american car people but the rot soon spread to Great Britain and the continent. An S.A.E. number will be as high as they can push it.

So we have a number taken at the output of the engine. B.H.P. This is a reasonably hard data point and is fairly trustworthy. So why the other types of horse power?

There was/is no easy way to test large steam engines on a brake (Prony Brake after the one of the inventors) but there is a need to find out how much power is lost between the steam or gasses pushing on the piston and the power at the crankshaft. It was discovered early on that one could measure the pressure in the cylinder and graph the chnage in pressure as the piton travelled. The area within this graph is an accurate measure of the power at the piston. The device used to graph this is called and indicator. Thus this number is called the Indicated Horsepower (I.H.P.). You you measure the area within the graph with another wonderful toy called a planimeter and there you are.

This is much more often used to adjust the valve gear than to measure the power.

When compared the the power at the crankshaft (B.H.P.) you have a measure of the losses, thermal, within the engine. Some of the losses are from friction but it all ends up as heat.

There are other numbers you will see such as Mean Effective Pressure and Peak Pressure. And there is another number that is calculated backwards from the B.H.P. to get what is named Brake Mean Effective Pressure (B.M.E.P.) This the I.M.P. that would produce the B.M.P. if there were no losses. This is more common in automotive practice and some of the numbers for supercharged internal combustion engines are startling.

If there were no friction losses in the ports or mechanical losses in our little engines, the power would be simply a matter of piston pressure and r.p.m. Turn it faster and get more power. There are devotees of this notion but it is seldom pleasing to ride in their boats. (personal judgement!)

So unless you find yourself a nice friction or hydraulic brake and test your power plant, you are at the mercy of a lot of speculation. My limited experience has been that a combination of surveying the experiences of others and examining the claims of manufactures with squinted eyes will keep you out of serious trouble. Its far, far from an exact science at our level.

Too long of a post. Sorry.

Jack? What did I miss or get backwards?