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Member postings for John Baguley

Here is a list of all the postings John Baguley has made in our forums. Click on a thread name to jump to the thread.

Thread: Purley Grange
20/05/2015 22:18:28

Hi Ray,

The valve gear as drawn by LBSC is very poor and I would recommend using the updated design by Don Ashton which was described in Engineering in Miniature January 2008. I can let you have a copy if you don't have access to it. I also redesigned the valve gear independantly of Don as I didn't realise he had already done it! Both new designs give much improved valve events.

You will need to update the boiler design by fitting bushes for all the fittings. On the drawings the blower valve and water gauge screw directly into the backhead and the top feeds screw directly into the boiler barrel which is not allowed now.

I started drawing PG in 3D CAD and found a few errors so far. The hornstays are shown as 3/8" wide but should be 5/16" to match the horns. Also if the front bogie stretcher is fabricated using brass angle, the angle obscures the bottom cylinder mounting holes in the frames.

John

Thread: very low temp solder
14/04/2015 21:55:32

Hi Fizzy,

Have a look at the Carrs range of solders as used for building etched brass kits. Some of those are low melting point and I've used them in the past for various jobs including soldering tanks and tenders. I got my stock from C&L Finescale.

**LINK**

John

Thread: Mr G F Wills scale model motorcycle combination
10/04/2015 20:08:38

It sounds like the one described in an article in ME Volume 103 Issue 2586 (December 12th 1950). I've got that issue if you can't get hold of it.

John

Thread: Regulator
27/03/2015 00:31:12

Here's one I made for my 2½" gauge Helen Long:

346.jpg

347.jpg

If I remember correctly, the thread on that is 3/8" Whit. The seat is bearing grade PEEK which contains PTFE and Graphite. The spring was supposed to take up any backlash in the thread but proved to be unnecessary,

I made a couple of smaller ones for two Tich's that used 5/16" Whit threads.

As Fizzy says though, ball (gas) valves are very good if you have the room to fit one. Just make sure it is rated for the pressure and the temperature.

John

Edited By John Baguley on 27/03/2015 00:36:50

27/03/2015 00:15:22

Hi David,

I use the largest diameter Whitworth thread that I can fit in. I find that 1/8 to 1/4 of a turn gives ample opening for normal running. It's surprising how little an opening of the regulator you actually need.

John

26/03/2015 10:00:06

My favourite is the screw (needle valve) type, preferably with a PTFE type material for the seat. Seals 100% and a nice smooth and gradual opening. Made quite a few and never had any problems with them.

I personally hate any rotating disc type regulator as it's virtually impossible to get them to seal against a hydraulic test and not easy to get them to seal against ordinary steam pressure.

John

Thread: Piston rings
20/02/2015 10:23:56

Hi Andrew,

I started using PTFE rings years ago and never looked back but have only used them on gunmetal cylinders so far. One of the locos has very high superheat. I don't see any problem with using them in cast iron as you have.

John

Edited By John Baguley on 20/02/2015 10:24:59

Thread: "New" Old Stock Kasenit; Does it expire?
17/02/2015 18:20:10

I bought my Kasenit in 1973 and it still works ok smiley

John

Thread: Ern Marshall
16/02/2015 13:19:10

I would have said cylinder drain cocks but looking at the photos in the album it doesn't seem to have them fitted. On Pansy it's usual to have just one drain cock at the back of the valve chest cover. There does seem to be a blanking plug in the position I would have expected the drain cock to be so maybe it's been removed?

It also looks as though the loco has dummy sanding gear fitted so the lever could be a dummy lever for that?

John

Thread: 5" Gauge Duchess
16/02/2015 13:14:01

Yes, try MECH. There is at least one person on there that has built the Duchess. I've seen it and he's made a superb job of it.

I should also add that Michael's drawings are very good. He keeps in touch with all the builders of his designs and if anyone finds an error Michael corrects it immediately and sends out a new drawing straight away.

John

Edited By John Baguley on 16/02/2015 13:26:12

Thread: Josie
13/02/2015 00:28:32

Hi Ricky,

The original pilot beams were often made from lengths of boiler tube with the ends flattened and bolted/rivetted to a frame so the 'casting' does sort of represent the full size versions.

John

Edited By John Baguley on 13/02/2015 00:29:14

Thread: Silver Flo 40
11/02/2015 09:54:29

Fizzy - expand the tubes in as Jason suggests. That's the normal practice. My brothers 5" loco has a steel boiler with copper tubes silver soldered/brazed in and they are starting to leak on the front tubeplate. We think the soldered joints are cracking and it's something very difficult to repair.

John

Thread: Hep with steam chest
07/02/2015 16:02:55

Neil,

Reading the above implies to me that you have not allowed for any lap on the valve i.e. you have made the face on the valve the same width as the port so it just covers the port? That will work (very old designs had this) but it means the cut off will be 100% i.e. the port will be open for the full stroke of the piston. Probably ok for running on air but very wasteful if running on steam as the steam won't be used expansively.

John

07/02/2015 14:17:36

Hi Eric,

You are really designing it a**se about face as you would normally determine the port width and the lap of the valve and then determine the required valve travel. But:

Total valve travel = 2 x (port width +Lap of the valve) assuming the ports fully open.

(Lap of the valve is the amount the valve land is wider than the port)

So if your valve travel is 20mm then your port width + valve lap will be 10mm assuming the port will fully open.

Things are complicated by the fact that the ratio of the lap to the port width determines the maximum cut off of the steam to the cylinder.

If you make the port width 5mm and the lap of the valve 5mm then the maximum cut off is 75%

If you make the port width 7mm and the lap 3mm then the maximum cut off will be 91%

Will you be using a fixed valve gear e.g. a fixed eccentric or a variable cut off valve gear such as Stephensons link? If you are using a fixed eccentric then you probably want the cut off to be 50 - 60% to avoid wasting steam.

The distance between the ports doesn't affect the valve timing and is more a case of picking a suitable figure so that the valve will fit in the valve chest without hitting the ends. You will also need to fit the exhaust port inbetween the steam ports.

If you're not too familiar with valve gears then this might help to explain the terms used etc.:

http://www.modeng.johnbaguley.info/Valve%20Gears/Basics.htm

Fizzy - your dimensions are half what they should be. Using your figures the total valve travel would only be 10mm.

John

Edited By John Baguley on 07/02/2015 14:24:48

Thread: Pansy 060 steam engine
06/02/2015 10:56:55

Hi Stewart,

What you are describing as a 3 way valve is the actual injector itself that puts the water into the boiler. It will no doubt be a commercially bought one (although some of us do make our own - not easy!)

John

Thread: Cutting curves in 1mm thick copper sheet
06/02/2015 00:08:13

For copper that thin just use decent hand shears. Cut a square and then trim to shape.

John

Thread: 7.25" GWR Toad
03/02/2015 17:59:33

Keith Wilson describes a 7.25" Toad for use as a driving trolley in ME Vol. 186 Issues 4146, 4148 and Vol.187 Issues 4150, 4152, and 4154. I'm not sure how close to scale it is though but might be useful?

John

Thread: Josie
01/02/2015 13:28:08

One of the chaps in the 2½" gauge Association made a 2½" gauge Josie by doubling up the dimensions. It makes a nice loco.

2.5 inch josie.jpg

John

Thread: Safety valves
29/01/2015 14:51:52

Are you using a decent accurate pressure gauge or the miniature one that you intend to fit to the boiler for use when running? The miniature ones can be very innaccurate and you should never set the safety valves using one of those.

As Fizzy asks, are the safeties starting to lift at 100psi and then rising to 120? You are allowed a 10% increase in the accumulation part of the steam test which means a maximum pressure of 110psi. If the pressure is increasing by 20% then the safeties are not adequate.

John

Thread: Cutting timing pulleys
28/01/2015 15:12:23

The second part is in issue 4456.

John

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