Geoff
Hi-poster
Posts: 169 
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Post by Geoff on Sept 17, 2014 1:59:04 GMT
I have decided that I cylinder cocks will be a good thing to have in spite of LBSC omitting them from his Maid of Kent design.
Don Young suggested ball type cocks in ME 21 November 1969 and I have followed this pattern quit closely, but I've made them with a 5/32" ball instead of 1/8" ball. They are not very elegant and are pretty chunky but sit hidden between the cylinder block and the bogie bolster so I don't care.
My question is this: the shape of the outside of the cylinder casting pushes the cock inlet some way into the cylinder rather than being at the end of the cylinder. Does this matter, and will the cocks drain effectively?
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Post by Roger on Sept 17, 2014 6:51:58 GMT
The plans I have for SPEEDY show the drillways to the drain cocks at an angle so they come close to the end of the cylinder.
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Post by albert on Sept 17, 2014 7:43:29 GMT
Hello,
The drain cocks should be as low in cylinder bore and as near the cylinder cover as possible.
Albert
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Geoff
Hi-poster
Posts: 169
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Post by Geoff on Sept 17, 2014 11:47:32 GMT
Hmmmm. I nly have about half an inch between the bottom of the cylinder and the bolster and was hoping to gain a bit of room by moving away from the thickening right next to the cylinder cover. Drilling and threading at an angle will complicate the way that the valve fits to the cylinder.
What do you lose if the cock is further away from the cylinder cover?
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Post by cplmickey on Sept 17, 2014 12:14:23 GMT
The point of the drain cock is to ensure that you have no incompressible water between the piston and the cylinder cover so if the drain isn't at the end then there is a greater chance that some will be left in there. The position of the cock isn't really important but the drilling is - as Roger says it should be near to the end of the cylinder cover. You don't need to thread at an angle though - it's the water/steam passageway from the bottom of the cock thread to the cylinder bore that is angled.
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Post by Deleted on Sept 17, 2014 12:26:20 GMT
You could always drill a hole from the end of the cylinder to the drain cock and then machine a groove to connect the hole to the end of the cylinder. Have a look halfway down this page to see how Ben did it on his Sweet Pea cylinders: linkJohn |
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Post by Deleted on Sept 17, 2014 12:50:40 GMT
Just an aside, if they are being fitted purely for the sake of fitting them on a slide valve engine all you will gain is lack of getting wet from the chimney at initial moving off. Slide valves (non balanced ones) by their design will be pushed off their seats if enough water gets between the piston and cover and therefore under the valve, it's not ideal but you would have to be practically running on water to overcome this in 5 inch gauge, piston valves on the other hand definitely need them! If you don't need to complicate things then why do it? Cheers Devils Advocate  |
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Post by albert on Sept 17, 2014 18:12:49 GMT
Hello,
Just a thought, can a pipe be run from the cylinder to remote mounted drain cocks??
When I was a loco builder I made a single valve with a rotating valve plate with 4 pipes to it. ( similar to a oscilating cylinder)
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Post by andyhigham on Sept 17, 2014 20:09:23 GMT
My loco has 4 pipes running to 12-3-6-9 positions around a section of brass bar mounted on the stretcher. A hole runs through the middle with a stainless steel piston in it. Lift the piston and condensate can escape, lower it to block the ports
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jma1009
Elder Statesman
Posts: 5,901
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Post by jma1009 on Sept 18, 2014 21:40:05 GMT
john (baggo) and others are absolutely correct, and whilst the tapped hole need not be at the end of the cylinder, the hole to connect to same needs to be drilled at an angle to come inline with the end of the cylinder covers. there is no shame in making a bit of a recess in the bores if it doesnt come out quite up to the covers. the trusty dremel and dental bur will suffice.
i have never built a miniature loco without a full set of cylinder drain cocks! early experience of club locos without same and getting showered with water convinced me of same very early on! as Ben says on a piston valve loco they are essential in any event.
on a big 5"g loco such as Maid of Kent i would regard them as essential! don's 1969 ME drawings of the modifications to gordon chiverton's Maid of Kent are very good (though the valve gear modifications arent quite ok)
cheers,
julian
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Post by Deleted on Sept 18, 2014 23:12:08 GMT
One advantage of manual drain cocks, which I didn't realise until I read it on another forum, is that you can use them to reduce slipping when starting a heavy load. Opening the cocks reduces the pressure in the cylinders and makes for a more gentle get away.
John
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jma1009
Elder Statesman
Posts: 5,901
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Post by jma1009 on Sept 18, 2014 23:20:43 GMT
hi john,
the other way of doing this is to notch up the valve gear when starting - this was fullsize practice particularly on the SR.
cheers,
julian
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Post by Deleted on Sept 19, 2014 1:04:50 GMT
I remember doing that when we had a 2½" rally at the Bromsgrove track. The ally rail was like a skating rink and it was virtually impossible to get up the long climb back up to the station. I had Helen notched right up and was pressing down on the tanks to try and get more adhesion but the wheels still spun like crazy!
John
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Post by Roger on Sept 19, 2014 7:10:45 GMT
I remember doing that when we had a 2½" rally at the Bromsgrove track. The ally rail was like a skating rink and it was virtually impossible to get up the long climb back up to the station. I had Helen notched right up and was pressing down on the tanks to try and get more adhesion but the wheels still spun like crazy! John I'm wondering if I should me including a telescopic 'Punting pole' for such situations... |
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uuu
Elder Statesman
your message here...
Posts: 2,808
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Post by uuu on Sept 19, 2014 7:37:04 GMT
A steam operated punting pole?
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Post by Roger on Sept 19, 2014 7:42:38 GMT
I was thinking manual, but there's an idea...
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Post by ejparrott on Sept 19, 2014 7:50:30 GMT
You'd have to use an imperial one though, being 5" gauge and all....
I've always struggled with ali rail, I hate it. I've seen it turn heavy passenger haulers into excited-puppy-on-laminate-floor nightmares. When we took Lilla to IMLEC at Leeds in '92, she kept derailing on one rail joint, and she took offence and removed a section of rail top for them!
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Post by Roger on Sept 19, 2014 8:08:26 GMT
From the little I've seen, it appears to be pretty useless for grip. I don't suppose clubs realise this when they opt for it. It's a real shame.
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Post by Deleted on Sept 19, 2014 15:19:24 GMT
From the little I've seen, it appears to be pretty useless for grip. I don't suppose clubs realise this when they opt for it. It's a real shame. --------------------- When it comes to club expenditure and the looming AGM suddenly it makes a lot of "sense" to those who don't actually have to drive on the stuff ! -------Ideally I'd say steel all round , but as a compromise then steel in the station limits and on rising gradients, with Aloominum ( for our friends in the Americas) on horizontal and falling gradients............And while we're at it}----- ANTI-TIP on the whole length of the track .....EDIT}--- just to get myself back "On thread" (and into your good books again !!)..the ant-tip might just help protect those vulnerable drain cocks as well ?? |
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Post by Deleted on Sept 19, 2014 19:36:26 GMT
The one thing that I do like about ali rail is the fact that it's less likely to wear/damage the tyres...i have seen some horrific tyre damage on some loco's, ali is a lot more forgiving... however as stated it's a challenge to get grip on a wet rail while negotiating an up gradient, especially on our club track with it's tall trees all around.
Pete
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