stephensons rocket help needed

[neal graingerParticipant @nealgrainger76459]

boiler thickness

[neal graingerParticipant @nealgrainger76459]

Hi all

Im new to live steam so could do with a bit of help please.

Im in the process of cad modelling the rocket in 71/4 gauge.Just to make sure everything fits before i start.But before i go to far what copper thickness should i use for the boiler and firebox.Also can i build the boiler myself and get it tested for a pressure test certificate or does it have to be built professional boiler maker.

Regards

Neal

[JasonBModerator @jasonb]

There are a number of calculations that will need to be done to work out the copper thicknesses, it would be impossible for anyone to give a thickness off the top of their head without knowing things like size, working pressure, etc.

Best thing to do is get a copy of Martin Evans book on locomotive & marine boilers as that will have the formulas that your boiler inspector will want to see and be using as his guidelines.

It may well be that you will have to make some allowance for practicallity over scale appearance or at least have some dummy parts, just looking at your very impressively modeled engine the large flat areas of the firebox backhead and end of the boiler barrel will not be acceptable without some form of stays to support them.

Yes you can make your own boiler but before you start to cut metal join a club and get their boiler inspector to look over the drawings and he will also say at wat stages he wants to inspect the work.

J

Edited By JasonB on 02/12/2014 08:05:50

[Stewart HartParticipant @stewarthart90345]

hi Neil

That's good advice J has given, if this is your first time to live steam I suggest you spend some time looking at drawings and reading some build books on a range of other models just to get your self familiar with the issues involved and a understanding of the critical design features. As J said martin Evans book on boiler design is a good book to get your hands on I picked mine up from ebay, I believe it is no longer in print, also joining a club will be a good move you will meet lots of experienced people who will be only to willing to help.

Good luck with your quest.

Stew

[julian atkinsParticipant @julianatkins58923]

hi neal,

as a first build a 7.25"g Rocket is far from ideal.

if you are attempting a scale version there are a great many unusual factors to be considered.

the boiler is a structural component as the loco does not have frames. everything is bolted to the boiler. this complicates things and is an additional factor that needs input into the design and calculations (though i suppose is what the traction engine lads have to do anyway).

the firebox is very unusual being in effect a separate component with an outer water jacket connected by pipes to the boiler. the throatplate and backhead are 'dry' and may originally have been just firebrick.

the way the loco valve gear is operated is by a complicated system of foot pedals and requires manipulation of the valves by hand initially. to my mind not incorporating the correct valve gear makes the loco nothing like the original. however the way of operating the gear makes it extremely difficult in miniature, if not impossible.

the driving wheels are wooden and will require a considerable degree of wood working skill to make them properly and accurately.

the cylinders have a very short valve chest with very long passages. this would be (as was the case in fullsize) a pattern maker's and foundry man's nightmare. even if built up and fabricated they would still be a very complex job.

cheers,

julian

[Jeff DaymanParticipant @jeffdayman43397]

Many models of Rocket have been successfully made despite the apparent challenges. I remember years ago seeing an ad for (I think) Cheddar Models (boilermakers) with a Rocket boiler, so commercial boiler designs at least in some gauges do exist.

It would be wise to read posts about the recent builds of several Rainhill locomotives in the past several years. The Rainhill design is very similar to Rocket (it is based on a later variant of the Rocket design) and some builders have reported driving problems with adhesion and side to side wobble of the front end.

Before tackling any complex build it would be a good idea to practice a bit with some simple small stationary engines and boilers and a simple locomotive or traction engine to hone your skills. It will just enable your Rocket to be even better.

JD

[JasonBModerator @jasonb]

And just so you don't get put off here is a nice one, notice the photo of it working with two people behind

Couple more shots on page 5 of this album and also some other early style locos on this page

 

Edited By JasonB on 02/12/2014 11:20:15

[BazyleParticipant @bazyle]

It might help you to find someone with the commercial (Hornby) 3 1/2 version and have a look at that .
I would think about making the firebox as a dry insulated unit.

[neal graingerParticipant @nealgrainger76459]

Thanks for replies.
on the look out for the book suggested. Alot of parts will be beefed up a little as wont be strong enough when scaled down.Going to join a local club in Wolverhampton. Get some knowledge of live steam.Neal

[Harry WilkesParticipant @harrywilkes58467]

Neal if your referring to the Wolverhampton MES you'll find some great guy's there and loads of help/advice.

H

[neal graingerParticipant @nealgrainger76459]

Hi H if the club you refer to use Baggeridge Country Park then yes thats the one i will be joining.

Julian thanks for the advice.I understand that it will be a challenge thats why im going for the rocket.As a pattern maker/tool maker by trade hopefully i have the skills to build the model.To get it to work properly might be a different matter.Most of the casting i will be using lost wax method so shouldnt be to difficult to get good castings.But with help from this sites experienced modelers and wolvo mes i think its achievable.

Regards Neal

[doubletopParticipant @doubletop]

Go over to here **LINK**. I know its finished as I recall seeing a video of him running it. Sign up and PM him, he's experienced and helpful

Found it……

Pete

Edited By Doubletop on 03/12/2014 08:56:52

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