Run time

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Re: Run time

Post by Tom the blacksmith » Fri Feb 08, 2019 9:18 pm

Sorry Tom, I didn't explain it well, it's not that it's blowing off all the time as if boiler pressure is too high or that the valve pressure was set incorrectly it just wisps steam fairly constantly. It doesn't really bother me, and I never really thought about it until Mr Dodger mentioned it.

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Re: Run time

Post by tom_tom_go » Fri Feb 08, 2019 9:21 pm

Take it apart and clean it, might have dirt or scale in it so not seating properly.

Failing that, contact Roundhouse and they should send you a replacement.

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Re: Run time

Post by CSL » Fri Feb 08, 2019 11:28 pm

artfull dodger wrote: Fri Feb 08, 2019 8:04 pm Upgrading Bertie with the options like a pressure gauge, water top up and sight glass really make a basic engine better than some of the older classic range models from Roundhouse that cannot have a sight glass by design at this time. I took a Sammie and changed the valve gear from slip eccentric to Walschearts with the kit from Roundhouse. Mike
Bravo! Not sure I'll ever get to that level.

I assume that if you fit the WeeBee safety valve the Roundhouse dome won't fit over it?

It seem that artfull dodger and tom_tom_go have completely opposing views on the practical effect* of replacing the Roundhouse safety valve!

*As opposed to the prototypical aesthetics of the pop 'n' shut function, which I doubt there's much disagreement over.

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Re: Run time

Post by artfull dodger » Sun Feb 10, 2019 6:42 pm

I use the safety valve made by Wee Bee Locomotive works, which is sold thru "The Train Department" website and shipped world wide. Available in many different pressure settings. According to the builder of the valves, who is also the leader of our local steam group, is the design of the RH valve that is prone to leaking as it relys on a O ring design. And while it does what is needed and does it well. Any steam leakage be it from the packing on the throttle shaft to the safety is wasteful and can reduce the run time. At a steam up with all the background noise, I have trouble getting my gas turned right down to keep even a proper pop valve from popping off constantly. Thats due to me being autistic and the noise overload overwhelming trying to hear the burner noise. Now on my 2 Regner models with thier noisy burners, when turned down to proper level I can still hear them. The Roundhouse FX gas system is really nice and really quiet when turned right down after initial start up and pressure raising.
Silly NT's.....I have Asperger's Syndrome!

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Re: Run time

Post by CSL » Sun Mar 17, 2019 7:03 pm

I got 30 minutes or so from the Bertie on a light load this afternoon, which would seem to be all right.

One thing though: it does seem to take at least ten minutes (of the run time, after pressure has built up) before it settles down to smooth and steady unattended running.

Obviously part of that is down to the gas tank heating up so the steam regulator needs to be adjusted downwards, but is my experience typical or am I doing something wrong?

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Re: Run time

Post by Keith S » Mon Mar 18, 2019 3:30 pm

The best part of a run is the middle bit. What happens is the gas tank slowly heats up, and as it does, provides a higher gas pressure to the burner. If you want to maintain a steady steam pressure you need to continuously turn down the gas for the first part of the run.

Meanwhile, you've started with a relatively full boiler. Since Roundhouse engines don't have a steam dome, the only place for steam to accumulate is along the top of the boiler where you've left some space. The smaller this space, the less well-behaved your locomotive will be. Obviously there's "priming" in which the loco will get some liquid water into the steam pipe, especially if the boiler's too full. But also, as the loco uses steam, it causes the pressure to drop momentarily in the steam space at the top of the boiler. The water then boils a bit and makes up the pressure. In equilibrium, I suppose the steam being drawn off by the cylinders and the steam being produced by the water boiling would be the same, but in reality the amount of pressure being drawn off by the cylinders changes continuously as the engine rounds curves and rolls across bumps, slowing down and speeding up. As the run progresses, the larger steam space in the boiler makes this process smoother because there is more steam accumulated there and it reacts better to small changes in pressure. Like the accumulator in a hydraulic system, if you're familiar with that. Anyway, at the middle of the run the gas tank has reached a steady temperature and your boiler is half full of nice springy steam rather than angry boiling water. That's why it behaves better. On a more comp,ex model with an axle pump and coal fire, you could keep it like that indefinitely, but on our little gas-fired contraptions, you notice all the effects of a boiler that is too full, just right, and too empty in one run!

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Re: Run time

Post by IrishPeter » Mon Mar 18, 2019 3:49 pm

One reason I have a soft spot for pot boilers is that their 'sweet spot' in terms of running is much larger than that of the single flue, internally fired, types. The down side is that they are appreciably less efficient. My Millie will chug away happily for 30-35 minutes after the initial temper tantrums caused by priming have subsided. I tend to use the Millie on the S&CLR&T when I want a low stress trundle.

I am currently trying to work out what my next move will be in terms of motive power as I need a locomotive that will run on 32mm for the Far End Tramway. I am heading towards either a Bertie, though I am also giving some consideration to Accucraft's Edrig replacement, or kit building a Roundhouse 'George.' The Far End Tramway is going to be a bit of an exercise in mountaineering, so I am going to have to choose wisely.

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Traffic Pattern? What pattern? Spuds out; grain in, but cattle, sheep and passengers are a lot less predictable.

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Re: Run time

Post by Chris Cairns » Mon Mar 18, 2019 5:35 pm

CSL wrote: Sun Mar 17, 2019 7:03 pm I got 30 minutes or so from the Bertie on a light load this afternoon, which would seem to be all right.

One thing though: it does seem to take at least ten minutes (of the run time, after pressure has built up) before it settles down to smooth and steady unattended running.

Obviously part of that is down to the gas tank heating up so the steam regulator needs to be adjusted downwards, but is my experience typical or am I doing something wrong?
Sounds normal to me. I find that the gas tank heats up more on my Bertie than other similarly mounted Roundhouse locos, so have to keep turning the gas down several times during a run. One thing I was not aware of until a discussion over on Facebook last year is that the Bertie has a high centre of gravity with more weight on the rear axle thus can be prone to centrifugal force rollovers on tight curves - mine has done it twice now.

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Re: Run time

Post by Chris Cairns » Mon Mar 18, 2019 5:43 pm

IrishPeter wrote: Mon Mar 18, 2019 3:49 pm One reason I have a soft spot for pot boilers is that their 'sweet spot' in terms of running is much larger than that of the single flue, internally fired, types. The down side is that they are appreciably less efficient. My Millie will chug away happily for 30-35 minutes after the initial temper tantrums caused by priming have subsided.

Peter in Va
In my experience, given the right conditions, I find the FX burner in combination with the fully enclosed combustion chamber, can be more efficient than the FG burner. Last year at a cold indoor venue my pre-owned 2002 Millie put in an impressive 63 mins run on one fill of mixed gas pulling 1 short coach on an out & back layout, running round at each end. Later in the year it ran for 53 & 55 mins on one fill of mixed gas on a Faller eTrain layout at an indoor model railway show.

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Re: Run time

Post by cncmodeller » Sat Mar 23, 2019 12:45 pm

I think 25 minutes is OK, I'm not a great fan of Gas fired locos I have three, to my mind they seem too fierce and too hot however much you try and turn them down,
and it always seems to me that you are trying to run a loco sedately while the boiler is bursting at the seems eager to charge around at full pelt and consequently you lose a lot of water so you are 'pressured' [excuse the pun] in pumping more water in at the earliest opportunity, so I wouldn't worry about the time per boiler fill.

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Re: Run time

Post by CSL » Wed Mar 27, 2019 10:18 pm

Chris Cairns wrote: Mon Mar 18, 2019 5:35 pm One thing I was not aware of until a discussion over on Facebook last year is that the Bertie has a high centre of gravity with more weight on the rear axle thus can be prone to centrifugal force rollovers on tight curves - mine has done it twice now.
I've had a couple of derailments but thankfully no rollovers!
Keith S wrote: Mon Mar 18, 2019 3:30 pm Since Roundhouse engines don't have a steam dome, the only place for steam to accumulate is along the top of the boiler where you've left some space.
So does that make my Mamod SL3 more sophisticated than the Bertie in that respect?
cncmodeller wrote: Sat Mar 23, 2019 12:45 pm I'm not a great fan of Gas fired locos
I've definitely got a soft spot for my ancient meths-fired Mamod SL3. No "roar" and that smell...

EDIT: corrected the type of Mamod to what I actually have...
Last edited by CSL on Thu Mar 28, 2019 12:17 pm, edited 1 time in total.

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Re: Run time

Post by IrishPeter » Thu Mar 28, 2019 3:20 am

CSL wrote: Wed Mar 27, 2019 10:18 pm
Chris Cairns wrote: Mon Mar 18, 2019 5:35 pm One thing I was not aware of until a discussion over on Facebook last year is that the Bertie has a high centre of gravity with more weight on the rear axle thus can be prone to centrifugal force rollovers on tight curves - mine has done it twice now.
I've had a couple of derailments but thankfully no rollovers!
The weight distribution issue (i.e. too much weight on the rear axle) is why the DHR B class locos have their little saddle tanks - or to put it more poetically - "why the Dachshund has its rucksack!" Apparently, even with the forward wing tank they were a bit bottom end heavy and would occasionally waddle off the track... and there are plenty of places on the Darj where you don't want to do that!
cncmodeller wrote: Sat Mar 23, 2019 12:45 pm I'm not a great fan of Gas fired locos

I've definitely got a soft spot for my ancient meths-fired Mamod SL1. No "roar" and that smell...
I do not mind gas firing, but I do prefer pot boilers to internally fired locos. The behaviour of the burner seems a little more stable to me, and they usually have a longer run time if the fuel supply is adequate.

Just my 2 rupees worth!

Peter in Va
Traffic Pattern? What pattern? Spuds out; grain in, but cattle, sheep and passengers are a lot less predictable.

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Re: Run time

Post by CSL » Thu Mar 28, 2019 12:16 pm

IrishPeter wrote: Thu Mar 28, 2019 3:20 am The weight distribution issue (i.e. too much weight on the rear axle) is why the DHR B class locos have their little saddle tanks - or to put it more poetically - "why the Dachshund has its rucksack!"
Does that mean that the saddle tanks must always be full?

To bring this diversion back on topic, that would surely reduce the B class's run time compared to what you might think!

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Re: Run time

Post by IrishPeter » Thu Mar 28, 2019 1:16 pm

The saddle tank in front of the dome is the first to empty, but it still helps even out the weight distribution on the full sized the loco given that the tank itself weighs something. It also has to be kept in mind the coal bunker is being emptied at the same time, so weigh is disappearing both sides of the dome. However, the really big help with adhesion on the Darj is the swinging link coupling, as opposed to a conventional chain or hook, which eliminates a good deal of coupling snatch, and also allows the loco to swing in to the bends more easily. Even without the two guys on the front, the B class are unusually sure footed, which with gradients as steep as 1 in 18.6, and sustained banks of 1 in 23 they need to be!

I don't know how the weight distribution is on the model, but one usually has the option of finding somewhere to stuff some extra weight if needed.

Peter in VA
Traffic Pattern? What pattern? Spuds out; grain in, but cattle, sheep and passengers are a lot less predictable.

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Re: Run time

Post by Keith S » Fri Mar 29, 2019 4:28 am

CSL wrote: Wed Mar 27, 2019 10:18 pm
Keith S wrote: Mon Mar 18, 2019 3:30 pm Since Roundhouse engines don't have a steam dome, the only place for steam to accumulate is along the top of the boiler where you've left some space.
So does that make my Mamod SL3 more sophisticated than the Bertie in that respect?
Yes, it does, if by "sophisticated" you mean "like the big engines". The Mamod design, having a steam pipe protruding into a discrete space for the accumulation of steam is quite elegant and I've always admired it. However, it leaves little provision for a proper regulator without a great deal of added sophistication, which is why other engine designers in this size range do away with it.

"Sophistication" is in the eye of the beholder. A fully "sophisticated" model steam engine would include an internally fired boiler with a draught provided by blower and exhaust, steam accumulation in a proper dome with a regulator valve incorporated into the dome, either externally or through the backhead, and superheater pipes in the smokebox. Many models incorporate one or two of these features, but most of them are either unnecessary or expensive to fit, or they are fiddly and irritating.

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Re: Run time

Post by TonyW » Fri Mar 29, 2019 9:04 am

Keith S wrote: Mon Mar 18, 2019 3:30 pmSince Roundhouse engines don't have a steam dome, the only place for steam to accumulate is along the top of the boiler where you've left some space.
Without exception, I believe, all Roundhouse locos have a turret on to which the regulator is mounted. The turret performs the same task as a dome, i.e. keeping the steam take-off above the boiler water level.

Some smaller locos (Wrightscale Wren, ELR Quarry Hunslet, for example) have the regulator plugged straight in to the boiler backhead, which can create some lively performance characteristics if the boiler is over-full.
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Re: Run time

Post by Keith S » Tue Apr 02, 2019 9:45 pm

TonyW wrote: Fri Mar 29, 2019 9:04 am
Keith S wrote: Mon Mar 18, 2019 3:30 pmSince Roundhouse engines don't have a steam dome, the only place for steam to accumulate is along the top of the boiler where you've left some space.
Without exception, I believe, all Roundhouse locos have a turret on to which the regulator is mounted. The turret performs the same task as a dome, i.e. keeping the steam take-off above the boiler water level.

Some smaller locos (Wrightscale Wren, ELR Quarry Hunslet, for example) have the regulator plugged straight in to the boiler backhead, which can create some lively performance characteristics if the boiler is over-full.
You're right, I guess the turret is a steam dome isn't it? Well, it's not a very big one anyway.

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Re: Run time

Post by CSL » Mon May 20, 2019 9:11 pm

A couple of runs with the Bertie over the weekend and it's nothing if not consistent! The stopwatch showed 9 minutes 45 seconds when it cleared that difficult curve for the first time neither too fast nor too slow, and carried on smoothly and without stopping for 17 minutes before the gas ran out and - with encouragement - made a further short run before coming to a halt.

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Re: Run time

Post by CSL » Sun Jun 16, 2019 9:26 pm

An interesting inconsistency (with the previous consistency) today.
The Bertie ran smoothly round and round my little circuit without stopping - if at varying speed - virtually from the first turn of its wheels, instead of the usual first ten minutes of start-stop before steady running is established.
Run time a few minutes (at least) shorter than usual: 23 minutes. Which is entirely consistent with the excessive (to my eyes) blowing off from the safety valve for about the first half of the run. And when I adjusted the gas regulator down, the stop-start set in intermittently on the principal bends.
So it seems to be a trade-off between steady running and long running, with the point on the scale determined by the size of the plume from the safety valve.

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Re: Run time

Post by big-ted » Mon Jun 24, 2019 9:17 pm

I was able to complete the full tour of our large club layout, 7 loops, with a few extra & a couple derailments on the less used loop, & back to the steaming bay in 24 minutes with my Lady Anne yesterday. The gas ran out at 27 minutes. There was a bit of blowing off at times so likely still room to extend the run a bit.

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