Safety valve bonnet

[alanetm]

Has anyone made the safety valve bonnet from brass sheet, and if so how did they go about it? Alternately has anyone knowledge of a brass casting that is available and can be machined? The clack covers are not a problem as I can make them from copper as they will be painted.

[itsbluesteel]

Hi Alan,

Well I'm presuming you mean a GWR safety valve bonnet, I have an un machined casting for 15xx class (speedy) so I know that casting is available but not too sure if that's suitable for your build.

Steve

[Laurie_B]

Polly Model Engineering supply a lost wax casting for 'Penrose Grange' that I'm thinking about using-if I ever get that far!
Martin Evans in his The Model Steam Locomotive shows drawings for a safety valve bonnet made by spinning from sheet brass,though there is no write-up on the subject.
I think that the late Roy Amsbury made model safety valve bonnets in this way and may have written this up in Model Engineer some time ago.

[Laurie_B]

Roy Amsbury wrote about his methods in Model Engineer Vol 139 No 3458,2-15 February 1973.
An alternative method was published in Engineering in Miniature Vol 33 No 3,September 2011.

[jma1009]

my GWR KING has a spun safety valve cover, and the safety valve cover on my GWR ARMSTRONG GOODS loco was machined and filed out of a solid lump of brass. i would suggest that a casting is the most difficult. the GWR safety valve covers deserve careful scrutiny. many people think the one i made out of solid is spun! the top beading is quite easy to do out of solid. be careful what brass you use as the GWR used gilding metal of a particular type that has a very yellowish colour. in fullsize you can see the coppersmith's joints where the parts are joined.
cheers,
julian

[alanetm]

Thank you for the responses .....I'll look at the magazine articles before I do anything else!

Available castings for different loco's are all too small for the large Prairie.

Alan

[Laurie_B]

Hello Alan,
There is a write-up by Mr.A.Crossfield in Model Engineer (Vol 203 No.s 4358 & 4360 : August & September 2009) about making a bonnet from the solid.As he notes,the method is rather wasteful of material.
I've compared the bonnet drawing for Penrose Grange against the Shortland/Reeves drawings and there isn't that much difference in size.The radii to suit the boiler cladding will be different though.

[taff]

Hello Alan,
I've been away for a while so I've only now picked up on your safety valve bonnet enquiry so I may be a bit late with my information for you but it may benifit others who are building GW designs. Over the past thirty years I have made a number of SV bonnets by beating them up from brass tube. I used 1-1/2" dia O.D. x 16 gauge tube for 5" gauge models and found that provided I kept the tube well anneald I could form the complete shape out of the tube without resorting to seperate parts for top and bottom. The tube needed a round bar machined out of a spare steel bar to fit inside the tube to stop it collapsing while the base was formed and I machined up and filed a former to enable the base to be beaten down on to for final forming. The top of the former was provided with an attachment to enable the top to be formed and the completed shape was finished by filing and fine wet and dry paper. I used 1/16" dia half round beading for top and bottom of the covers.I word of authenticity here, the top beading on the full size was formed by peaning the edge over on to the top flat part and not shown as a beading from below.
I made a further former for making the Dean type saftey valve bonnets. None of the models I have yet completed required the top feed covers attached to the SV bonnet however I have three 5" gauge "Saints" under construction which will require these covers. I throw in the above for discussion because I've never seen any reference to SV bonnets being made from tube.

Taff.

[Rex Hanman]

Interesting method Taff, any pictures please?

[taff]

[taff]

Hello Rex and all,
I don't know what has happend here because all of my text about the above photo's has disappeared. This happend when I clicked on the photo's to enlarge them. It has happend twice today and due to the late hour I don't feel inclined to re write it now. Maybe tomorrow.

Taff

[Rex Hanman]

Thanks Taff, they look great, I'll certainly try that method when I get that far on my prairie, assuming brass is still available that far in the future!

[taff]

Hello Rex, Alan and all,
I've had a night's sleep now so I'll try some text againn. The photo's show a SV cover made by the method I described and is for a model of a GW "Badminton class No 3310 "Waterford" in pre 1906 condition with a Standard No. 4 D2 type Boiler. When making the SV Bonnet from tube I found it fairly easy but I must emphasise that "annealing" is the real answer to the method. I've built a number of GW models but as yet none of them have required the top feed covers, all being represntative of pre 1911 condition, however I have three "Saint" class models currently under construction which will need these covers when I get there. Being Chairman of the Rivet Counters Fellowship, and for the benifit of those who intend to enter competative competitions,I should mention a point of authenticity re these SV covers. Bearing in mind that generally our 5" gauge models are viewed from above. the inside of the cover is easily seen and therefore the it should be painted a dark grey colour up to the inside edge of the top beading. When I was a cleaner at Ebbw Junction sheds in the late 1950's we never cleaned inside the top of the cover because it rapidly tarnished to dark grey after the engine had been in steam for a short while.
I'll try to attach a photo of one of my models with a SV cover made from a tube but I don't hold much hope for it becoming attached.

Taff.

Attachments:

[taff]

Hello all,
Good lord,it worked. and I don't know what I did. Bear with me while I try another couple just to confirm my method is correct.


Taff.

Attachments:

[taff]

Hello all'

Eeeeeeek!. it worked. What i don't understand though, is why did they come out one above the other, whereas on my other post above they came out side by side.
At least we know we can enter multiples now instead of one per post.

Taff.

[Rex Hanman]

Thanks again Taff. Some people are never satisfied though, any chance of a pic of the formers etc. ?

[taff]

Hello Rex and all,

Very good chance of photo's of both formers providing I can find them in my workshop. Due to health problems I've not been in my workshop for the past five years so I'm out of touch with things at present but a fellow conspiritor has volunteered to fight his way in to find both formers. When he liberates them I'll post some photo's. I'll also put in a better description of how I formed the main shape of the tube. If I am able to make another SV bonnet I'll try to keep a photographic record of it, after all I have to make three for my "Saints" and one each for my "Duke" and 3521 class, five in all. We'll see how it goes.

Taff.

[taff]

See above.

[taff]

See above.

[Rex Hanman]

Thanks Taff. Hope your health is better now.