The Steamboating Forum

Dear Steamboating Colleagues

Wearing my SBA Secretary "hat" I have received the following enquiry and suspect that there are some amongst you who will know the answer.

"Greetings,

I am rendering the engines of the Olympic Class ships which will be animated when complete. I have all the parts completed and I have used my copies of Thomas Andrews notebook, Engineering, and the Shipbuilder as guides. I have also referenced many books on marine engines to give me a fair knowledge of triple and quadruple expansion engines. I have a background in mechanical engineering and know just enough to get me into trouble.

My problem is with the LP cylinders which I am drawing utilizing double ported slide valves which were used in the Olympic and Titanic, but I have also drawn a set with the piston val;ves used in the Britannic. None of them seem to work. The problem is that the ports do not open and close when they should. I have switched eccentrics and made calculation after calculation but nothing seems to work. On the downstroke of the LP aft with the crankpin at 322 degrees the valve would be center at 270 degrees with both ports open to exhaust. I know valves were designed to allow steam to open earlier and close later on the lower end in order to compensate and aid in counterbalancing the great weight of these valves. I am puzzled by there not being any admission of steam at the beginning of the down stroke or upstroke. Steam doesn't begin until the piston is nearly 1/3 through its stroke.

I would appreciate anyone who could enlighten me on what I am missing here. I am at a dead end and would like to complete this engine as I have 17 months tied up in working on them.

Kind Regards,

Michael L. Dudley


I have suggested to Michael that he joins us, so he may register soon.

Best wishes

Pete

I have replied direct to Mr Dudley on this matter. Will post anything of interest which it throws up.

regards
Jack

Thanks Gentlemen!

Are keyseats generally in line with their respective eccentrics?

I am trying to determine lap and lead on the LP's of these engines.

Anyone?

I would take a first guess that the eccentrics are mirror sysmetric. The angel between the center of the eccentric and the key being equal to 90 + the angle of advance.

This would need to be confirmed...


Dave

mcandrew1894 wrote:I would take a first guess that the eccentrics are mirror sysmetric. The angel between the center of the eccentric and the key being equal to 90 + the angle of advance.

This would need to be confirmed...


Dave

Dave, I believe you are correct. I have done some reading and it seems that in some of the earlier marine engines, they keyseats were 90 degrees out of eccentric center. In the later engines, and especially the larger ones, they appear to be in line with the eccentric center.

John confirmed that the LP's were at 90 + an advance angle. It seems obvious now and I had myself in such a state of confusion due to taking a technical manual as the gospel, which proved false, that I just couldn't see what had to be fact. I had thought these would have an angle of advance early on, contrary to what the manual stated, but dismissed it.

I greatly appreciate the input.

Greetings All,

After many setbacks and delays, I have finally completed the engine animation I started nearly two years ago and have added it to our web site. It was suggested by a fellow member of this forum that I post the link here as it is said it will be of interest to others on this forum. I hope you enjoy it and I welcome any and all comments, whether good or bad.

The engine can be accessed in our "technical section" at http://www.wslmf.org/index2.html

I am planning on animating the turbine engine next and mating it to this.

Best Regards,

Michael

Very cool Website, and nice job on the animation!

bkueber wrote:Very cool Website, and nice job on the animation!

Bret,

My apologies for the late reply. We are very busy over the holidays with charitable work.

Thank you for your kind words. They are much appreciated.

Best Regards,

Michael