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Building LBSC 31/2" Mabel

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Stewart Hart08/07/2009 18:44:09
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Hi is there anyone else out there building this loco

[IMG]http://i431.photobucket.com/albums/qq32/sbwhart/JUMBO1.jpg[/IMG] 
Stewart Hart24/09/2009 16:28:32
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674 forum posts
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Well it looks like I'm the only one in the world building this loco.
 
Managed to get the chase running on air not without some difficulties ended up having to go back to basics with the the slide valves and redesign them with this done it started no problem see vid, can't believe that Curley got it so wrong or it it something I've done, as anyone else had similar problem.
 
Hoping for a reply
 
Stew  
Mark Piper24/09/2009 18:43:34
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Hello Stewart,
 
I have recently purchased a set of castings for Mabel but won't be making a start until I have finised my current loco Tich.
 
How did you find building the chassis? Are there ant howlers in the plans or pit falls to look out for?
 
Regards
 
Mark
Stewart Hart24/09/2009 19:58:24
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674 forum posts
357 photos
Hi Mark

I used a laser cut chassis I'll look up where I got it from it went together  great my only error was to drill both sides for the reverser had to put a couple of counter sunk rivets in to cover the mistake up. The biggest problem I've had so far is setting the slide valve timing spent over 6 weeks trying to get it sorted ended up working out the sizes for myself, once I did that it ran no problems. I never thought at the time to ask for help on her but things seemed a bit slow, but I suppose they have just started.

You can follow my build so far on this forum http://madmodder.net/index.php?topic=547.0

I've put it to one side for a couple of months to do other thing (workshop related), I was getting a bit frustraited with the timing so decided that a change would be as good as a rest.


I'll be picking it up again I don't give up on things I always see them through.

Thanks for contributing

Stew
John Baguley24/09/2009 22:12:57
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517 forum posts
57 photos
Hi Stewart,
 
I'm not building Mabel myself but have had a look at your build notes on the other forum and the problems you are having.
 
It looks to me as though the problem could well stem from incorrect valve timing i.e. the setting of the eccentrics. The valve dimensions given by LBSC are fine, indeed the port and valve dimensions are pretty standard for a 3½" loco. The face of the valve that moves over the port is 3/32" wider than the port. This is the 'lap' of the valve and it's this lap that allows the steam to be used expansively and hence economically. The total valve travel in full gear should be twice the lap plus twice the width of the port which gives 7/16" (which I believe you have).
 
It sounds like the valve may be opening at the wrong point in the stroke due to incorrect setting of the eccentrics and you've corrected this by  shortening the valve by a considerable amount in order to get it to run.
 
Setting the eccentrics on these types of valve gear (Allan, Stephenson, etc.) can be very confusing and frustrating until you have done a few! It's very easy to get the forward and reverse eccentrics crossed over or the eccentrics leading the crank rather than following (or vice versa ! )
 
John
Stewart Hart25/09/2009 07:15:03
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674 forum posts
357 photos
Hi John
 
Thanks for your advice: you've confirmed my fears that modifying the slide would effect efficiency I just couldn't believe that Curly got it wrong. In the six weeks I was trying to get it set I must have made every mistake in the book plus a few new ones. I've got a tooling project well underway so I'll get that completed, pick up some material from the midland exhibition in Oct and have another go.
 
When I joined up the coupled wheel it ran ok but not as freely, and then one of the coupled wheels became lose on the axle (only glued at this point) so I think I may have the quartering slightly out that and a wobbly driven wheel I have one or two other things to sort out.
 
As you may have guised this is my first build, I'm dreading starting the boiler, but hay that's all part of the fun and adventure.
 
Once again thanks for your advice much appreciated
 
Stew 
 

Stewart Hart18/11/2009 18:58:23
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674 forum posts
357 photos
Just a quick update, I'll be remaking the slide valve picked up some material at the Midland expo.
 
Just completed the lubricator I didn't follow Curley's design I'm not to keen on the spring and ball none return valve, instead I followed Nevile Evans's design for his STOW build (Pt 31 Vol 202 issue 4352) and it worked a treat here's a video of it running under drill power just to give you the idea.
 
 

Cheers
 
Stew 

Edited By Stewart Hart on 18/11/2009 18:59:54

Edited By Stewart Hart on 18/11/2009 19:05:12

Stewart Hart21/11/2009 12:32:50
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674 forum posts
357 photos
HELP
 
I've just made the boiler feed pump and there is no way I can get it to fit between the frames as shown in the drawing, as any one got a completed Mabel out there who can post a picture of how it fits.
 
Thanks
 
Stew 

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