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Regulator improvements

Sweet pea regulator takes in water on inclines!

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P84R16/07/2019 10:55:14
6 forum posts

Hi all! I have a sweet pea loco and could do with picking some brains about an issue I'm having.......

When I open the regulator up it admits water to the cylinders and up the chimney, this is more noticeable on an incline where the water is obviously towards the backhead. It's fine with a little regulator, but when climbing it could do with a bit more without swallowing the water.

I don't run with the boiler full so it's not that, I can't run with the water much lower or when I get to the downhill the crown will be dry. The regulator is to the drawings and tucked up to the top of the boiler.

Short of making another boiler with a dome I'm running out of ideas to alleviate this problem.

Any advice greatly recieved!

Howard Lewis16/07/2019 16:03:07
2895 forum posts
2 photos

Any chance of siting a baffle under the regulator, so that steam can enter from the sides and ends, but the water is prevented for slopping up into it?


P84R16/07/2019 16:51:37
6 forum posts

I had thought of that before but I'm limited to the size of baffle due to the hole for the regulator body. But it may be worth trying out.

The feed tube for the regulator has 5 holes drilled in the top so should only allow steam to enter from the top anyway in theory

Werner Schleidt16/07/2019 17:44:20
83 forum posts
144 photos

What kind of water do you use ? is it very soft?

I use filtered rain water with good sucsess. I was some time a go at a club track and they had super soft water. During driving the water came out of the chimney and I thought there is a damage.

With rain water at our club track after 5 Liter of use the loco ran normal again.


duncan webster16/07/2019 17:47:38
2424 forum posts
39 photos

If it's made to the official drawings, the regulator is fed from a bent pipe which is cantilevered from the backhead, with as said above, a row of holes in the top side. It is always possible that this pipe has drooped, either whilst silver soldering the backhead in place, or some other reason. Trouble is you can't see it unless it happens to be right under the safety valve holes. I made mine deliberately offset by a tad. If I were still in gainful employment I could have borrowed a boroscope to poke down one of these holes, with a light down the other, but I'm not so that isn't much help. You might get somewhere exploring by feel with a bit of bent wire, but I wouldn't bet the farm on it.

Pre-judging the situation, if this is the case all is not lost, you could mount both safety valves on a tee off one hole, and feed the regulator with a looped pipe from the other. Before I stopped the regulator leaking, I considered doing this with mine so I could use a ball valve .

Paul Kemp16/07/2019 22:07:45
389 forum posts
18 photos

Is the boiler clean? As previously mentioned what is the water quality? Carry over is not unheard of as steam demand increases. If you imagine the rate you are taking steam off the water if the demand is high then you get vigorous bubbles at the water / steam interface and the more steam you need the more likely it will pick up water with it. If you search spirax sarco on utube you will find some very good videos taken inside an industrial boiler of what happens. Keeping the boiler clean and the TDS down may be all you need.


P84R16/07/2019 22:23:03
6 forum posts

Werner. The water around us isn't too bad but certainly something to keep in mind.

Duncan. Yes the pipe is just under the safety valve bushings so I know that is still there. The idea of a ball valve could be a good one..... even though the regulator tube is only around 1/2" below the top of the boiler it sucks water quite easily however the safety valves have never primed in the same situation!

Paul. The boiler is relatively clean, descaled once a year in addition to being blown down most times and given a rinse through from time to time. I can understand it picking up water if it was being thrashed but it doesn't have to be thrashed for this to occur. Worth a watch.

Werner Schleidt17/07/2019 15:30:55
83 forum posts
144 photos

Is the tube with the holes in the boiler removeable?.

A friend with an vertical boiler on sentinel elephant had the problem with much water in the steam.

The steam engine had not a good performance. He took the steam in the boiler with a tube with many holes around.

My theorie was that the water bubbles can good go through the holes. I told him to make a tube with small saw cuts with the same surface as the tube had with the holes. My idea was that the water bubbles were craked as they want to move through the small saw cuts.

My Friend changed this pipe and he was very happy with the performance then. And you can hear it that the steam engine runs much more with dry steam.


P84R17/07/2019 19:40:28
6 forum posts

I'm not entirely sure as I haven't removed the regulator block yet. But I'm sure it can be made removable!

Interesting..... worth trying out. Thanks

julian atkins17/07/2019 20:10:41
1227 forum posts
353 photos

Hello P84R,

The first thing I would do is to take off the water gauge fittings and check that their passageways and the areas around inside the boiler are free of obstructions that might give a false water gauge reading.(Check also that the bottom fitting and bush does not protrude too far into the water space).

You might also be getting priming when the loco is being worked hard, as others have suggested. Also you do not state whether the safety valves are lifting as you go up your incline. You can get a localised pressure drop in a boiler that can promote priming, as opposed to priming being caused by dirty water or water with some oil in it.

Water carry over to the cylinders is quite a serious problem and can cause damage to the cylinders and motion, if not increased wear, and ought to be properly investigated.

If there is a water carry over, you need to shut the regulator and open the cylinder drain cocks.

Do a search online for LNER pacific 'Blue Peter' and the disaster at Durham.



P84R17/07/2019 20:23:31
6 forum posts

Upon quick inspection there has been nothing blocking the passages or anything wrong with the water gauges but I will remove everything over the weekend hopefully to thoroughly check.

Sometimes the valves lift and sometimes they don't, this doesn't seem to change the effect on the regulator though and the valves have never primed on any incline or otherwise. It does make me wonder what's going on with the valves not priming although they are only sitting around 1/4" above the tube in question.

Yes I have witnessed hydraulic lock and it's not a pretty sight! I'm getting close to stripping the whole loco down for an overhaul anyway which is why I'm trying to come up with ideas to try and solve this while I have it in pieces.

duncan webster17/07/2019 23:12:14
2424 forum posts
39 photos

here's a photo of one I saw on a club stand at Doncaster 2109. Unfortunately I didn't note which club, it might be worth contacting the Sweet Pea owners group. I used to be a member but then it went over to facebook and I refuse to have anything to do with social media (possibly because my missus says I'm anti-social) . It appears to be fed off the turret. If it's made to the original you can't get the bent pipe out, You could drill it out but that would leave the bent bit loose in the boiler. If you manage let us know how

sweat pea ball valve (small).jpg

P84R18/07/2019 00:17:27
6 forum posts

Very interesting! I like that one. Very simple but effective.

I have various sized and shaped grips and forceps from years of fiddling with motorcycle engines so I'm hoping to be able to grip it through the safety valve bush and try to thread it out somehow..... if I manage I'll post it here, although that might not be for a few weeks yet as I would do that in the workshop while I have it apart.

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