A Question with four outcomes « Thread Started on Apr 18, 2012, 6:46pm »
This is the backhead of a B! boiler i bought sometime ago, The problem i have is this As it stands the top and bottom feeds for the sight glass are at an angle Do I 1) leave it alone, (i don't like the idea of that looks too traction engine!!) 2) make an extension piece so it lines up vertical ( bit messy but gets what i want) 3) as 2 but make a backhead cover to hide the pipework 4) get the bush shifted ( What problems would be lurking in doing this, I wont do it, get it done by a pro) All suggrstions welcome Thanks
Re: A Question with four outcomes « Reply #1 on Apr 18, 2012, 7:03pm »
I'd be tempted to leave well alone, my original AJAX drwgs had a slanting sight glass on the cab layout but a modified boss on the outside of the shell on the boiler drwg. This pic from Station Rd Steam shows the slanting version http://www.stationroadsteam.com/stock%20pages/2771 whereas this Achillies (same boiler) shows the altered 'external' boss for a vertical glass http://www.stationroadsteam.com/stock%20pages/5220
You wouldn't necessarily know what grade silver solder was used in the original construction, probably lower melting point than the cadmium free stuff the pro builders are obliged to use nowadays so the getting the whole lot hot enough to solder on another boss may be fraught with trouble.
Cheers
« Last Edit: Apr 18, 2012, 7:11pm by durhambuilder »
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Re: A Question with four outcomes « Reply #3 on Apr 18, 2012, 9:34pm »
G'day other Ron
Based on bad experiences I'd say the gauge glass is in the wrong position.
I doubt, but would like to be corrected, that the bottom nut will be above the firebox crown with sufficient water cover (10% of stean space in the AMSB Code.)
The effective glass length will be quite short. I've seem a very experienced driver friend come unstuck (thankfully the boiler didn't) because the glass was prototypical and not long enough to always see the meniscus. In the dark and in dappled sunlight full and empty glasses can look the same.
A bush in the wrapper to line the bottom fitting up with the bottom fitting would help.
Fitting such a bush you could use Comsol. This practice was proposed to me by none other than the secretary of the AMSB committee. Advantage you do not have to heat the boiler close to the melting point of the existing solder.
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Re: A Question with four outcomes « Reply #5 on Apr 18, 2012, 11:11pm »
G'Day Ron, I agree with Ian about the size of the glass and that when you hit the bottom nut the water level if still above the top of the firbox crown. At and angle shouldn't be a problem but the AMBSC specifies a maximum of 45 degrees, I think ans superseven is correct about being able to check the water passages. I am not familiar with Comsol but if the AMBSC allows it then it would be OK. Would TIG welding a new bush/bushes in place be an option? I don't know the answer. What do others think. Cheers, Arch
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Re: A Question with four outcomes « Reply #6 on Apr 19, 2012, 4:17am »
Hi Firstly is this for a class B1 Springbok boiler (maybe a typo but says B!) I have a complete set of the drawings for this boiler and 3/4 way through construction of the loco. I will do some comparisons tomorrow and post you again Bob
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Re: A Question with four outcomes « Reply #7 on Apr 19, 2012, 8:17am »
Looking at photo could be misleading because we don't know the distance between the bushes , generally for a round top boiler the top bush is on the top to give enough distance but there is no rule on that . the other thing is once you fit the water gauge bottom fitting , the bottom of the glas should be as mentioned above the crown by 10% of the distance between the crown and the top of the wrapper . If you reposition the bottom bush the water gauge will be shorter. To fit another bush you be required to do another hydrostatic test , In my opinion if after fitting the bottom water gauge fitting the bottom of the glass is OK ( if not you can screen a little of the glass to get that ) , the length of the glass is .75" or more , I would leave it alone .
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Re: A Question with four outcomes « Reply #8 on Apr 19, 2012, 8:28am »
Yes, I think some may be looking at the wrong two bushes. I assume you would propose to move the middle bush to make the sight glass vertical with the existing top bush. This looks to be OK from the water level point of view. I think it would be difficult to place it in a better vertical position. However, the new bottom sight glass bush would be getting close to the firehole opening.
This is an area well avoided for modification. It may well disturb the soldering of the firehole ring and that would be very difficult to put right. Many leaks around the firehole have proved impossible to fix and, at the very least, are for the "big boys."
My advice - come to terms with it if you can and live with it. There is only one real reason for moving it and that is to become prototypical - and just moving the bush will not achieve it, but I know how these things can get to people, you just do not like sloping gauges - fair enough.
G'day other Ron. Based on bad experiences I'd say the gauge glass is in the wrong position. I doubt, but would like to be corrected, that the bottom nut will be above the firebox crown with sufficient water cover (10% of stean space in the AMSB Code.) The effective glass length will be quite short. I've seem a very experienced driver friend come unstuck (thankfully the boiler didn't) because the glass was prototypical and not long enough to always see the meniscus. In the dark and in dappled sunlight full and empty glasses can look the same. A bush in the wrapper to line the bottom fitting up with the bottom fitting would help. Regards Ian
Morning Other Ron. A picture below of my 5" Springbok backhead with the floor out. As you can see, it is very similar except for the sight glass position.
Are we all talking about the same two bushes for the sight glass here?
My answer to the other question - leave well alone.
P.S. Eventually got the picture sorted but had to add a new post!
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Re: A Question with four outcomes « Reply #11 on Apr 20, 2012, 6:49am »
Tony , may I ask if the four in line stays above the fire door , are they longitudinal stays ? It seems the bottom of the glass tube is not higher than the crown , I may be wrong but just it looks like that to me . I am not criticising just wondering as we are discussing this issue on the other engine .
Tony , may I ask if the four in line stays above the fire door , are they longitudinal stays ? It seems the bottom of the glass tube is not higher than the crown , I may be wrong but just it looks like that to me . I am not criticising just wondering as we are discussing this issue on the other engine .
Yes, they are longitudinal stays. Shawki, you are correct, the bottom of the glass is about at the crown, a tad lower. It depends on what fitting is used I suppose - and a slightly higher "bottom of the glass" would mean it is OK if I can see water. It is probably better to have it higher, but at the moment at least, I am content as long as I know where it is.
The comment that in certain lights a full and empty glass can look the same is not true if you use red or blue line glass. John
John, very true and it works very well. The slanting stripes behind is also a good indicator. If desperate, opening and closing the blowdown will allow you to see the water descend and recover in the glass, if overfull. If not - desperation!
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Re: A Question with four outcomes « Reply #13 on Apr 20, 2012, 4:27pm »
Quote:
If desperate, opening and closing the blowdown will allow you to see the water descend and recover in the glass
Last year I did a footplate experience on an Ivatt Class 2. I was surprised how often the fireman blew done the gauge glass. Not without good reason, the name of the game seemed to be keeping the safety valves from blowing rather than keeping the water below the top of the gauge glass. After driving models, driving and firing the real thing was certainly an different experience.
Peter
« Last Edit: Apr 20, 2012, 4:29pm by peterseager »
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Re: A Question with four outcomes « Reply #14 on Apr 21, 2012, 6:38am »
Thanks Tony for the answer , I am sure you know this , when you have time ,you can make a new bottom nut with a sleeve to hide say 3/16" from the bottom of the glass and then anyone can drive the engine without worry .Just an idea . I have done that myself on one engine .
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