John's Herreshoff Style Engine

[Johnlanark]

Here's Corra Linn's engine part built. This is 2.5" x 5". I've realised that the hotwell platform on the right hand side of the A frame is too high - I laid this out from a drawing for a larger engine - so will need to modify the pattern and have a new frame cast. So it's two steps forward and one step back. Over the winter I'll try to finish the coreboxes for the cylinder pattern. But I think I said that last year!



John

[87gn@tahoe]

What a beautiful specimen.. shame you'll have to reverse your progress a bit.

[mcandrew1894]

I think she's beautiful just as she is! Great Job!

Dave

[Maltelec]

John, did you ever take that to the SBA rally at Windermere a few years ago?

[Johnlanark]

Hi Simon, yes that's right, I think it was just the base then. It has not been a rush project! But I am back on the case now.

The pattern for the frame was quite interesting to make. It is in two pieces - you can see the split going through the projecting boss and platform. Everything each side of this split either curves in just as part of the shape of the part, or is made slightly tapered so it can be withdrawn from the sand. Core prints (painted black) make impressions in the sand to support the cores in the mould that produce the inside shape.



There are two core boxes, for the top and bottom parts of the frame.


For the top one, two pieces of hardwood were first turned to the basic shape.....



(One of the halfs is not used). Next, the curved inside shape was formed on the milling machine.



This piece was used as a "male" mould to make a "female" fibreglass half core box. It produces sand cores the same shape as the piece of wood. At the foundry, the moulder makes two cores and pastes them together to give a full depth symmetrical core.

The triangular shaped core box for the bottom part of the patterm is more simple. It is just a plywood base with wood sides. This core box is full depth and two cores are again made, this time for the left and right hand side - that is, one is turned upside down.

I then went on to use the top core piece of wood as the basis for the frame pattern, gluing on thin timber strips like strip planking a boat, to give the metal thickness.

Hope this description may be of interest. John

[Edward]

I DO WISH people would stop putting postings like this onto this site . They make me thoroughly miserable when I realize my own complete inadequacy .
Nonetheless very interesting and my congratulations and admiration. I presume the platform for the hotwell was quite a bit too high for you to decide to re-start the frame from scratch ?

Edward.

[Johnlanark]

Edward - thanks for kind words. Yes the platform is too high, the hotwell would have been too small. I've now cut off the platform from the pattern halves and have the new bits nearly made ready to glue on. It took me about two years to accept that it had to be done, and about two hours to do it. Although once I have the new casting it will need machined again of course.

Is there interest in the forum in patternmaking? I could post some simpler "how to do it" stuff if so. How about how to make a pattern for a cylinder, with steam ports cast in?

John.

[Edward]

Dear John ,

I can well believe it took two years of worrying/realizing that the platform was wrong before deciding to bite the bullet or grasp the bull by its horns and change the pattern .
So often it is the psychological aspect that defeats : as Chairman Mao said " A march of 10,000miles starts with a single step, " it's making that step or deciding to make it that is difficult .
As to whether there is an interest in pattern making in this forum I can't give an authoritative answer but I would have thought the answer was a definite yes .
It might be sensible and interesting to wait and see if there any other responses and if there are (as I think there will be ) to take a specific problem/question and use it as an illustration for your " How to do it " guide .

Regards Edward .

[87gn@tahoe]

ANY and ALL info on patternmaking is welcomed (by me anyway )

With LOTS of photographs, please.

[mcandrew1894]

OK Lets see.

A considerably talented person making an incredible copy of a Herreshoff engine...one of the most beautiful launch engines ever built...would like to know if anyone on a steamboat forum would like to know about pattern making.....ENGINE pattern making mind you....


Hmmmm.......OK wait for it.......

YES!!!!!!!!