Hi all,
I need some clarification on the orientation of the eccentrics on a 20 HP Stanley crankshaft. The only information I have to go by is the Bruce Green drawings sold by SACA, sheet #4, which is a little confusing. According to this, the two eccentrics closest to the gearwheel that are integral with the gear, should be in the same position as each other when viewed from each end of the shaft. As these each have a 10 degree offset from the keyway, this would place them at an angle of 20 degrees difference from each other. but if I look at my gearwhwwl, both eccentrics are in the same location on the gearwheel. Am I misinterpreting here??. And the outer eccentrics are supposed to be 120 degrees different to the inner ones - is this correct. Could someone draw a sketch showing the relative position of all four eccentrics to each other when just looking from one end of the crankshaft - this should help avoid confusion.

I pressed all eccentrics and cranks together in what I thought was the correct position but I am sure I have it wrong, especially with the two eccentrics on the gear being the same. I'm guessing that all 20HP engines had the eccentrics in exactly the same orientation no matter what date but this may be wrong - these are for an R.

Any help gratefully received!!

Jeff

Hey Jeff,

From what I understand the later 20 hp engines had different eccentric settings then the earlier engines, especially the later 740 engine. The only engine drawing I have at hand is of the 30 hp Rocket engine and it doesn't have the degrees marked, just the eccentrics drawn.

Is the engine an original Model R type engine, what is its bore and stroke, is it the earlier 3.63 by 5" or the later 4" by 5" or something even different? For those who have more engine specific knowledge then I this may be very usefull information.

I have read of different eccentric settings being used in different time periods of the Stanleys manufacture.

The eccentrics should be set for their pistons crank and since the cranks are at 90 degrees to eachother the eccentric sets should be 90 degrees off from eachother.

I don't understand why they could only be set at 20 degrees from eachother and am curious to here from others about this.

Can you take a picture and attach it to a post here, that would be very helpfull.

Caleb Ramsby

Jeff
Stanley eccentric depending on the engine can be between 135 degrees to 137-1/2 degrees from TDC. On all outside admission valves steam engines, typically the eccentrics can be found to be between 115 to 145 degrees in the direction of rotation. (shaded area) of drawing. The reverse eccentric is in the opposite direction of rotation normally in the same degree of rotation, but not on some marine engines.

For a two cylinder engine with cranks at 90 degrees to each other the second cylinder will have the set of eccentric rotated 90 degrees as well (see eccentric set in red rotated 90 degrees from the set in blue.) the forward eccentric of one cylinder is nearly in the same position as the other depending on the angle of the eccentric setting. Make sure you assemble the eccentric strap to the correct end of the link bar.
I hope this helps
Rolly



Edited 1 time(s). Last edit at 04/23/2011 12:26AM by Rolly.

Thanks Rolly, that makes a lot of sense. So my eccentric locations on the gearwheel can be the same. I just have to reverse the outer ones. I think what really confused me is the drawing on the SACA drawings showing the eccentrics on the shaft but they are showing the outer ones in exactly the same position relative to each other. Now I just have to figure out how to get the eccentric off on one side so I can turn it around! It went on OK but there isn't a lot of support you can give it to press the shaft out.

Jeff.

The drawing shows TDS. Is that a typo, or some bit of esoterica of which I wot not? Top Dead Steam, perhaps?

Ian Cameron

My error Ian. Should be TDC, I corrected the drawing thanks.

Rolly



Edited 1 time(s). Last edit at 04/23/2011 12:27AM by Rolly.

Jeff Brown Wrote:
-------------------------------------------------------
> Now I just have to figure out how to get the
> eccentric off on one side so I can turn it around!
> It went on OK but there isn't a lot of support
> you can give it to press the shaft out.
>
> Jeff.



Jeff,

Done that when removing main crankshaft inner tracks from my crank. I made a gadget with a grooved track for the balls, just the same as the original outer track but split for assembly then bolted together with a couple of bolts fixed tangentially and with a lip to get a three legged puller on. Worked fine.

Mike

Thanks Mike, I did a similar thing and I have now got it in pieces ready for reassembly. They are a lot easier to put together than take apart - I used a 20 ton press and didn't think it was going to move the crank but then there was a loud bang and it moved about a 1/4 inch - I moved a lot more!!!

Jeff