[modeleng] Re: Finding dead centres on a loco

Stealing Jesse Livingston's thunder a bit here, he told me to pull the head 
and put a nut on top of it (vertical engine).  Nut should be thicker than 
the clearance between the head and piston at TDC.  Then crank clockwise 
until things stop, make an identifying mark, crank the other way until 
things stop, make a second mark.  Pull the head and remove the nut.  Halfway 
between the two marks is TDC.  Charles
>
> I've got to determine the lengths of the rods which run from the return
> crank to the expansion link on my Sweet Pea fitted with ouside admission
> Walschaerts' valve gear. To do this I have to set the engine on front and
> rear dead centre. I've seen the method where you mark a point on the wheel
> and a point on the slide bar when approaching dead centre, rotate past 
> dead
> centre to the point where the mark on the slide bar is in the same place
> relative to the crosshead, mark the wheel again and divide the distance
> between the marks on the wheel to find dead centre.
>
> First question "Is this the best way?"
> Secondly, "how do you divide a curve into two equal parts?". I can do a
> straight line with a rule and dividers, but as I see it half of the
> construction space is in thin air outside the wheel!
>
> Any thoughts gents?
>
> TIA
>
> JohnP

MODEL ENGINEERING DISCUSSION LIST.

To UNSUBSCRIBE from this list, send a blank email to, 
modeleng-request@xxxxxxxxxxxxx with the word "unsubscribe" in the subject line.

Other related posts: