Gary L
Elder Statesman
Posts: 1,208
|
Post by Gary L on Dec 14, 2018 1:51:49 GMT
I just had a quick look, god knows why I didn't before..christ the details are on the same page...lol Hope they are of interest... Pete Hi Pete & many thanks They definitely would be if I was thinking of using it for a single vehicle of my own, in the way Pete is. But my thoughts are for a fleet of club vehicles, which means large quantities, and these days we can't rely on members volunteering a lot of workshop time. We tend to be cash-rich and time-poor these days, at least in relation to yesteryear. So if we could find a commercial article that would do the job, it would be fantastic. -Gary
|
|
|
Post by Rex Hanman on Dec 14, 2018 18:01:06 GMT
"Pete Sorry to hear you are ill. Hope you will make a swift recovery (sounds like you've had some practice!)" +1
|
|
|
Post by Deleted on Dec 14, 2018 18:10:11 GMT
"Pete Sorry to hear you are ill. Hope you will make a swift recovery (sounds like you've had some practice!)" +1 thank you, Rex.. much appreciated sir... Kind regards Pete
|
|
|
Post by steamer5 on Dec 15, 2018 7:26:42 GMT
Hi Gary, Check out PNP plastics they do a vacuum brake cylinder.......there’s also a animated schematic on how they work . www.pnp-railways.co.uk/products/category/vacuum-brake-equipment/Now has anybody got a non scale vacuum brake valve......similar to the one shown on the PNP site that they would be willing to share? Cheers Kerrin
|
|
|
Post by steamer5 on Dec 15, 2018 7:29:48 GMT
Hi Pete, The coach is coming along nicely, not sure if we can catch up next month, I’ve got work on the Sunday. A 6 hour round trip drive on top of a fun day in the sun might be a push!
Cheers Kerrin
|
|
Gary L
Elder Statesman
Posts: 1,208
|
Post by Gary L on Dec 16, 2018 14:01:29 GMT
Hi Gary, Check out PNP plastics they do a vacuum brake cylinder.......there’s also a animated schematic on how they work . www.pnp-railways.co.uk/products/category/vacuum-brake-equipment/Now has anybody got a non scale vacuum brake valve......similar to the one shown on the PNP site that they would be willing to share? Cheers Kerrin Hi Kerrin Um, yes, that's what we currently use. I'll say no more. WRT brake valves, they are usually just a disc valve with a hole on one surface and a narrow slot on the other, so pretty easy to design. A lap-type valve (best for locos) is only a little more difficult. Keep the holes quite small if you have any ambition for gradual application as opposed to on-off. In our sizes it takes only the smallest of 'leaks' to kill a vacuum, so the mating surfaces must be beyond reproach. However for 'emergency only' application, as in the case of a Guard's valve, this is all too much trouble, so we use the smallest size of over-the-counter ball valve which are cheap and reliable. Gary
|
|
|
Post by doubletop on Dec 22, 2018 10:19:12 GMT
Apologies I'd missed these last posts I really do need to investigate the 'autobraking' setup as some of the points made went a bit over my head e.g. "prodder stem type". Some diagrams would help and hopefully when Pete G recovers and we've all recovered from the upcoming festivities we'll get to see one? Kerrin I'm using a valve similar to the type you are interested in. Very simple, I'd made it for the steam drain cocks on my Simplex but it was hopeless under pressure as the faces wanted to open. Not a problem with a vacuum so I pressed it into service as a quick fix for getting my brakes to work a few years ago. It’s still as I originally installed it. Unfortunately I don’t appear to have a picture or drawings as it was a Saturday morning sketch and build job. An update on the Auocoach. Progress continues and I took it out for a run last weekend. I still don’t like the roof and today made some more formers for the solid roof. However, the bigger problem is the leaking cylinder on the Dart. I investigated today, hoping it was a drain cock issue. It isn’t, the rear right cylinder over gasket has blown. To fix it properly the cylinder assembly has to come out. That means, running boards, front buffer beam, boiler and smoke box removed to get at the cylinder assembly. Its not as big as it could be as the cab and tanks come off after every run and it can only take me about 1/2hour to get the boiler out. I just need to get my head in a good space to crack on with it, especially if I want to make “Locomotion” in January. Pete
|
|
|
Post by doubletop on Dec 22, 2018 10:59:11 GMT
I just had a quick look, god knows why I didn't before..christ the details are on the same page...lol Hope they are of interest... Pete I've re-read the posts and Pete's reference to "page 23" and realise he's not talking about Don Youngs pgae 23 but his thread modeleng.proboards.com/thread/5733/building-don-youngs-doncaster?page=23Looking at the cylinder drawing on Pete’s thread you may well be in luck. The right-hand image shows the vacuum inlet. You will see in the left-hand image a small hole, that is the other side of the diaphragm to allow air to inflow when the vacuum is applied. Could that be modified to be the second port on the Don Young cylinder in the drawing? modeleng.proboards.com/attachment/download/1245What I don't know is the gland arrangement around the actuator shaft. I doubt the OEM part has one but something could possibly be created and held in place by the two 6mm mounting studs? Maybe getting a bit to much of a bodge? Pete
|
|
stevep
Elder Statesman
Posts: 1,070
|
Post by stevep on Dec 22, 2018 18:14:57 GMT
Pete,
Look at page 23 of Pete's (greenglade) thread on building Doncaster, and part way down there is a drawing of the vacuum brake cylinder.
I don't have a picture of the whole set-up to hand at the moment, but I'll try and describe the action, referring to Pete's drawing.
The lower pipe on the left-hand side is attached to the 'train pipe'. This runs through the train, with joins between carriages, and is plugged on the final carriage.
The valve, which screws into the bottom of the lower half of the cylinder, is a ball valve, the ball being held upwards against its seat by a spring. Above the ball is a 'prodder'. When the vacuum is applied to the train pipe (and the lower half of the cylinder) the piston is drawn down, and will touch the 'prodder', lifting the valve off its seat.
The other side of the valve is piped up to the top pipe on the left hand side - probably through a 'T' piece, which is also connected to a large empty vessel. (Like my head, according to some!).
The connection then evacuates the top half of the cylinder (and the empty vessel - often called a vacuum reservoir).
When the train pipe is opened to atmosphere - either by the use of the brake valve, or if two carriages become disconnected, the piston is drawn upwards by the vacuum in the top half of the cylinder, applying the brakes.
The vacuum reservoir ensures that the reduction in volume by the piston moving upwards is minimised. The bigger the reservoir the better.
Re-applying the vacuum to the train pipe draws the piston back down, releasing the brakes.
Hope that helps.
|
|
stevep
Elder Statesman
Posts: 1,070
|
Post by stevep on Dec 22, 2018 18:19:53 GMT
P.S. One thing I didn't mention, is that you MUST have some method of getting rid of the vacuum in the top of the cylinder/reservoir, otherwise you will never be able to move your loco or carriages, as the brakes will be locked on.
A simple ball valve somewhere in the circuit is all you need. On my Stanier, I built it into the end of the reservoir.
|
|
|
Post by doubletop on Dec 23, 2018 21:17:30 GMT
Steve
Thanks for the explanation, I do follow it now. The implementation of brakes in our models that I have come across in NZ have been of the ‘simple’ type although some clubs do operate the ‘automatic’ brakes. The operation of automatic brakes has similarities to some electronic principles where the circuit is biased off and go ‘on’ when the bias is removed. A capacitor acting as the reservoir. I had understood it in full size but as I had no practical application it had slipped away.
I think the problem with using a commercial cylinders is that they tend to have an internal spring that holds the actuating rod on the extended state. The effect would be that the spring would be opposing the action of the reservoir trying to pull the brakes on so reducing the effectiveness. However, I expect that somebody has probably already come up with a scheme that works.
As I write this I have ideas running through my head that dispenses with the ‘hold off’ vacuum being applied to the cylinder and uses the train pipe vacuum to operate a valve that maintains a vacuum in the reservoir and once the train pipe vacuum is lost the reservoir is connected to the ‘on’ side of the cylinder.
Unless you have leakage in the system a brake release valve is an essential with 'simple' brakes otherwise, as you say, you won't be able to move the train after application, nor be able to 'feather' the brakes.
Pete
|
|
|
Post by doubletop on Jan 1, 2019 20:42:53 GMT
I had said I wasn't happy with the roof and decided to replace it. I've managed some time over the holiday to get it started. So new year and new roof. I'm not too fussed if the PAX think its not as comfortable as a padded seat but that's not the point. Pete
|
|
stevep
Elder Statesman
Posts: 1,070
|
Post by stevep on Jan 2, 2019 9:32:59 GMT
Excellent model aircraft wing construction there Pete!
|
|
JonL
Elder Statesman
WWSME (Wiltshire)
Posts: 2,909
|
Post by JonL on Jan 2, 2019 11:16:13 GMT
Thats very elegant indeed. Kudos.
|
|
barlowworks
Statesman
Now finished my other projects, Britannia here I come
Posts: 874
Member is Online
|
Post by barlowworks on Jan 2, 2019 11:22:06 GMT
Love the roof construction. I must be doing something right, that's the way I do it in O gauge.
Mike
|
|
|
Post by doubletop on Jan 2, 2019 19:01:27 GMT
Excellent model aircraft wing construction there Pete! Steve Not that aerodnnamic, V1 would be in the high hundreds and our track speed limit is 10km/hr Love the roof construction. I must be doing something right, that's the way I do it in O gauge. Mike Mike And I hope you don't have people wanting to sit on your O guage wagons? There is a bit of a reason for the over engineered construction. I made the Toad you can see on the bottom rack intending it to be a driving trolley along the lines of the Keith Wilson write up. The guys were watching when I first tried to sit on it and I could see from their faces something was up. Then there was a comment "I wouldn't do that if I was you", I'm 100Kg. Being factual rather than impolite, we do have some large people in NZ, just think All Blacks and you'll get the picture. If this wagon is going to take PAX then it needed to be a up to the job 300-400kg at least. Going back to the photo of welding the frame, it is 2"x1"x1/8" tubing Thats very elegant indeed. Kudos. Thanks Pete
|
|
barlowworks
Statesman
Now finished my other projects, Britannia here I come
Posts: 874
Member is Online
|
Post by barlowworks on Jan 3, 2019 0:28:37 GMT
We have a saying here in Yorkshire, wearing belt and braces. You'll do for me son.
Mike
|
|
|
Post by doubletop on Jan 4, 2019 7:25:26 GMT
Painted the roof sections. Some finishing touches are still to be done, inluding hinges for the two main sections. Next will be fitting out the cab, other external embelishments like steps and handrails and the internals such as tanks, and electrics. However that's on hold for the moment because the loco needs one of the cylinder gaskets replacing and that's not a small job Pete
|
|
mbrown
Elder Statesman
Posts: 1,720
|
Post by mbrown on Jan 4, 2019 10:14:50 GMT
It looks a bit bare without rooftop ventilators....
They would dig into the fleshy parts of your passengers and help them to avoid slipping off the coach.....!
Malcolm
|
|
JonL
Elder Statesman
WWSME (Wiltshire)
Posts: 2,909
|
Post by JonL on Jan 4, 2019 10:37:22 GMT
That looks fantastic, superb work.
|
|