Black 5 blast pipe

Hi looking for some info on blast pipe for my 5" black 5.

I did a couple laps on it but it seems to be lacking power.

At the moment it has an 1/2 hole in blast nozzle but I have threaded it to be able to change.

It has 1 5/8 Pistons I would like a starting point if poss as on the plans it just says 42 !!

Also from top of blast pipe to petticoat pipe what distance should it be.

Hope some one can help please

Ron

1/2 sounds big to me, but I'm no expert. Does the plan mean a number 42 drill which is 0.0935".

Neil

Hi Neil Julian says it means 420 th he also says its to big going to try a 5/16 then an 11/32 I have made several so I can keep changing just needed a starting point also found it should be 2" from top of taper to top blast nozzle.

Thank goodness for this site to point us in the right direction.

Best Regards

Ron

From my experience and based upon info on the John Baguley website, the blast nozzle orifice diameter should be one seventh 1/7 of the cylinder diameter, so 0.232" for 1 5/8 cylinders.

For nozzle height, research blast cone angles on the web, many people use a 1 in 3 cone and 1 in 6 cone geometry, the 1 in 3 cone should intersect the petticoat pipe and the 1 in 6 cone should intersect the stack or chimney.

Works for me.

Keith Wood

Montreal Live Steamers

The figure 42 seems to be 1 5/8 in millmieters.

The rule of thumb I was given is that the blastpipe nozzle should be 1/7 the diameter of a cylinder.

This rule totally transformed my machine; before it was gutless, difficult to steam and prone to enforced stops due to low pressure. Now it steams beautifully.

Peter

Could it be 4.2mm?

Whilst the 1/7 rule often works it is a little illogical. The nozzle diameter should be based on the steam flow (which is governed by bore, stroke, wheel size, rpm), and boiler resistance (which is governed by grate area and tube flow area)

If the loco is designed on the Ewins boiler factor (which realtes grate area to steam demand), then I suspect it all boils down to nozzle size being based on grate area, but I'm sticking my neck out there. No doubt someone will chop it off.

Duncan is quite correct, and the Greenly 1/7 rule gives far too small a blast nozzle if everything is designed ok.

To deal with Ron's 42, this is 0.420" on the drawings for the blast nozzle ID.

The Greenly 1:3 and 1:6 have largely been replaced now by the Jos Koopmans' formulae. One of the big problems with the Greenly ratios is that it does not set the 'choke' diameter, and there is a fixed relationship between choke diameter and blast nozzle diameter and the distance between the two for optimum results.

Cheers,

Julian

Thank you Julian now have some thing to work from fingers crossed be interesting to see the difference

Ron

Well due to heavy rain never got chance to try Loco so be at least 2 to 3 weeks before I can next try it.

At least it's in the trailer already loaded up ready to go.

Ron

Ron. Why don't you make a rolling road for your Black 5 then you can steam up at home and get a idea how your alterations are working, and make any necessary adjustments that may be needed.

Mike.

Time to make it what I need but going into Hospital for a pace maker next week so got to slow down for a bit.

Not sure sure I would tell on rolling road to driving it.

Anoyher one! perhaps we should have a build your own pacemaker series?

Seriously, I hope it all goes smoothly for you Ron.

Neil

The weather has been rather bad the last few days, at least in South Wales!

Best wishes Ron for the op. There are far more important things in life than what we do in our workshops.

Cheers,

Julian

Sppeaking from experience here...if you make it to the spec on JB's website AND get everything perfectly in line I am sure it will pull the coals right out of the box! However, if you dont get everything perfectly in line it simply doesnt work. Nearly isnt good enough. My 7 1/4 went from very poor to OMG

I made mine with several ends to screw into blast pipe.

I tried to steam it but my injectors stopped working so I had to stop before running.

I have a problem with my tender I bought pipe work wrong also leaking.

Can't wait to work on it but just has a pace maker fitted said no lifting for 6 weeks.

Soon be working I hope

Ron