Darjeeling Flats on axle for Water Pump

[SteambuffParticipant @steambuff]

Just a quick question .. sorry if the answer is obvious.

 

I am about to machine the axles for the Darjeeling ‘B’ Class. One of the axles has the two flats milled on it for the eccentric which drives the water pump.

 

On the drawings both of these are in line with one another, I would have thought it would have been best to have them 180 degrees apart, (They both have there own bypass valves and boiler clacks), so I can’t see this being a problem, it would then in my view even the load out a bit and give a more continious flow to the boiler.

 

Am I making a stupid assumption?

 

Dave

 

[SteambuffParticipant @steambuff]

[DustyParticipant @dusty]

Steambuff

I had decided that I would move the eccentrics to 180 degrees, as you rightly say this should even out the load. I have not started out on my construction yet as I am finishing my current project, but I do have a big box with lots of materials and goodies in for when I start. Before you start your axles read what I have said about the back to back dimension shown on the drawings. It is in one of the forum items. I will try to find it and post here the reference. The thread is ‘Darjeeling locomotive’ dated 3/7/2010

Edited By Dusty on 03/10/2011 10:37:07

[SteambuffParticipant @steambuff]

Dusty,

Thanks for that, I have been building up my collection of bits for the ‘B’ Class. I have your comments on ‘Back to Back’ and flange thicknesses saved in a spreadsheet. (As I have all useful comments and corrections)

 

The next issue I will be facing will be ‘Do I make corrections/adjustments caused by the fact that my Frames are made of 3mm steel and not 1/8″ (Water-Cut frames from Blackgates), and what do I adjust?” Do I increase the size of the streacher/draw-bars etc or do I put shims under the cylinders etc, or something else?

 

Dave

 

[David Clark 13Participant @davidclark13]

Hi There

I can’t see 7 thou per side making any difference.

regards David

 

[SteambuffParticipant @steambuff]

David,

 

Dusty seemed to think it would affect the valve gear. (in his post of 25/7/11).

 

I might just bring the Cranks in by 7 thou by tweaking the dimensions of the axle box and the axle’s 2 outer sections … to allow to build as drawn (with a shim) or to bring the cranks in 7 thou.

 

 

Anyway David, what is your view on putting the 2 axle pump eccentrics 180 degrees apart?

 

 

Dave

 

[David Clark 13Participant @davidclark13]

Ray said that it should not affect the engine if you turn an eccentric 180 degrees.

He also does not think 7 thou would matter.

regards David

 

[SteambuffParticipant @steambuff]

Thanks David

[DustyParticipant @dusty]

My preference is to adjust the stretchers and horns to compensate for the 14 thou difference remember that you are doubling the error as there are two frames. The other option would be to increase the cylinder bore to bolting face by 7 thou. I must say that I do not like building in errors I would much prefer to compensate for the difference in frame thickness, this is only personal, at the end of the day you have to decide what you want to do. The only thing I would remind you is that if you do not adjust the frames to correct o/side dimension anything bolted to the frames may need to be adjusted.

[SteambuffParticipant @steambuff]

Dusty,

 

Yes it’s 7 thou each side.

 

I think there are several options –

 

1/ Build as drawing and hope machining error, slop etc compensates.

 

2/ Build as drawing but modify hornblock/axle-box/axle to bring in 7 thou each side.

 

3/ Make everything that bolts to the outside of the frames 7 thou further away. (Shims?)

 

4/ Increase spacing between frames … and modify everything that bolts to the inside of the frames. (i.e Well tank supports, pump spacer, Draw Bars etc)

 

I think I would rather go with option 1 or 2 seems to be less work, if it don’t work I can always put shims under.

 

Must accuractly measure my frames … Blackgates say they are 3mm … a spray of primer would reduce the error

 

Dave

.

[Author]

Posts