Challenger Smokebox Design

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RET
Posts: 960
Joined: Wed Jun 07, 2006 8:36 am
Location: Toronto, Canada

Re: Challenger Smokebox Design

Post by RET »

Hi Paul,

These pictures show what Gerhardt did in our Big Boy. We were lucky enough to acquire the model when Gerhardt was unable to finish it and I have been slowly working on it ever since.
General view from the top
General view from the top
As the caption says, this is a general view from the top of the smokebox showing both stacks and as far back as the dummy whistle. Gerhardt didn't make the collapsible smoke control louvers so they don't show in the picture. In this scale, they would be hard to make work effectively.
Closeup view of the rear stack
Closeup view of the rear stack
This view shows a closer view of the two stacks. You can see the four blast nozzles at the center of each of the cloverleaf "petals" and the petals are part of the double smoke control petticoat. If you look at the third picture, you will see what this assembly looks like from the side, especially when you view them together. The five smaller nozzles you see are the blower nozzles. There are four located in between the blast nozzles (some are hard to see) and the fifth one is in the center.
Stack from front.jpg
This view shows both the multistage petticoat and the blast nozzles. If you study the pictures you can see how it all fits together. Gerhardt did all this and if you look at the Union Pacific drawings on the CD, you will see that our model (Gerhardt's work) is identical to the real thing.

Multiple blast and blower nozzles are necessary because there simply isn't enough height to make anything else work. Gerhardt planned on running the model on propane and we will be doing the same. Apparently propane needs a steady draft, but doesn't require as much as you need when firing with coal.

From my experience with the Boston and Albany, I have found out that getting the drafting right is worth every bit of the time and effort you spend on it. It pays big dividends.

As you probably know, Tom Miller's Big Boy was made in England by Severn Lamb and ran on 7 1/2" gauge track. When it was sold and moved to Australia, it was regauged to 7 1/4" because that is the standard everywhere else in the world except for the western United States and Canada.

The picture you posted is very impressive. I for one would like to see more pictures of what you are doing with your model.

Hope some of this helps.

Richard Trounce.
RET
Posts: 960
Joined: Wed Jun 07, 2006 8:36 am
Location: Toronto, Canada

Re: Challenger Smokebox Design

Post by RET »

Hi Paul,

The Locomotive in your picture is not Tom Miller's big Boy because on his locomotive, the driver sat on top of the tender, not inside it. There may be others in Australia, But Tom's is the only one I know of that was shipped there.

I would still like to see some pictures of what you are doing.

Richard Trounce.
KenG
Posts: 53
Joined: Mon Aug 31, 2015 12:48 pm
Location: Aurora, Colorado

Re: Challenger Smokebox Design

Post by KenG »

Tom Millar's big boy went to New Zealand. The overscaled big boy form the Dobwalls Railway in Cornwall went to Australia.
RET
Posts: 960
Joined: Wed Jun 07, 2006 8:36 am
Location: Toronto, Canada

Re: Challenger Smokebox Design

Post by RET »

Hi Ken,

I made a mistake. Yes, as you say, Tom Miller's Big Boy went to New Zealand, not Australia and after the regauging, it has been run in Memorial Park in Tauranga. According to Google Earth, Memorial park is on the seafront in Tauranga.

There is at least one U-Tube video showing it running there. It is certainly one impressive locomotive.

Richard Trounce.
k36no4862002
Posts: 151
Joined: Sun Feb 08, 2009 4:27 pm
Location: Surrey, UK

Re: Challenger Smokebox Design

Post by k36no4862002 »

Gents
Thanks for your help on this. I think given all the information I have I will be best to go for a 4 nozzle per chimney design and to copy the original works drawings.
I will make this my project over the next few months along with my dome casting project and will post some pics as things develop.
Obviously I'll be using pics you guys have provided as my inspiration for job to do it.
Many thanks
Paul
Paul Edmonds,
Surrey, United Kingdom.
2.5" Scale D&RGW K36, 1/6" Scale Challenger 4-6-6-4 (nearly done!!)
RET
Posts: 960
Joined: Wed Jun 07, 2006 8:36 am
Location: Toronto, Canada

Re: Challenger Smokebox Design

Post by RET »

Hi Paul,

I'm sure we all wish you the best of luck and please keep us posted on your progress.

Richard Trounce.
Glenn Brooks
Posts: 2930
Joined: Mon Nov 10, 2014 1:39 pm
Location: Woodinville, Washington

Re: Challenger Smokebox Design

Post by Glenn Brooks »

Paul, Iam sorry, I didn’t notice in previous post, will you be burning coal or propane? The multi port blast nozzle systems are designed for coal only. If propane, you may need a different front end design.

If coal, the multi part blast nozzle, one for each exhaust stack, I am sure will give you excellent results. There are a couple of formulas that relate total multi nozzle surface area to cylinder area and stack diameter. I’ll send you Nigel Day’s email via PM. Likely he would be interested in advising you regarding diameters and rule of thumb. He is in Wales I think, so maybe fairly near by.

Glenn
Moderator - Grand Scale Forum

Motive power : 1902 A.S.Campbell 4-4-0 American - 12 5/8" gauge, 1955 Ottaway 4-4-0 American 12" gauge

Ahaha, Retirement: the good life - drifting endlessly on a Sea of projects....
k36no4862002
Posts: 151
Joined: Sun Feb 08, 2009 4:27 pm
Location: Surrey, UK

Re: Challenger Smokebox Design

Post by k36no4862002 »

Thanks Glenn,
Im based in the UK and most model steam locomotives over here burn coal, this will be a coal burner.

Thanks
Paul
Paul Edmonds,
Surrey, United Kingdom.
2.5" Scale D&RGW K36, 1/6" Scale Challenger 4-6-6-4 (nearly done!!)
JJG Koopmans
Posts: 342
Joined: Thu Oct 01, 2009 10:01 am
Location: Netherlands

Re: Challenger Smokebox Design

Post by JJG Koopmans »

Glenn Brooks wrote: Tue Oct 20, 2020 11:59 am ...... There are many differences between the multi port blast nozzle ejector system and the single port- chiefly the multi-port exhaust surface area is over twice as large as single port versions......
Regards,
Glenn
Rereading the thread this quote surprised me. Did you ever mathematically check this?
It is not the surface area that works, in fact I severely diminished the surface area in the multiple exhaust of the GWR King class 6023. It is the relative length of the chimney that takes care of the improved behaviour, a fourfold orifice has a relative doubled chimney length and the graphs of diffuser tests show how much improvement this delivers.
Kind regards
Glenn Brooks
Posts: 2930
Joined: Mon Nov 10, 2014 1:39 pm
Location: Woodinville, Washington

Re: Challenger Smokebox Design

Post by Glenn Brooks »

Dr. Koopmans, Yes, exactly. Thanks for clarifying importance of chimney length. I suspect this is something we often overlook.

Regards,
Glenn
Moderator - Grand Scale Forum

Motive power : 1902 A.S.Campbell 4-4-0 American - 12 5/8" gauge, 1955 Ottaway 4-4-0 American 12" gauge

Ahaha, Retirement: the good life - drifting endlessly on a Sea of projects....
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