Run time

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CSL
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Run time

Post by CSL » Mon Jan 21, 2019 8:53 am

I gave my Bertie its first steaming of 2019 at the weekend, albeit on rollers (the permanent way gang has been slacking over the winter...).

It took 9-10 minutes to build up steam to the point where it was escaping from the safety valve - it was a cold day so this may have been longer than average. I follow the instructions in cracking open the gas for lighting, leaving a short while and then turning it up to the point where opening further makes no difference to the roar from the burner.

I then had 32-33 minutes with the wheels turning, although of course being on rollers the loco wasn't moving any weight or negotiating curves*. As I had both the gas and steam regulators turned up higher than strixtly necessary for a bit of time, this might have been extended a little.

The Clatterbach Valley Light Railway nominally has no gradients but has a ruling three-foor curve radius, which may well be rather uneven (!).

Is this kind of run time typical/mediocre/good? I generally get marginally more than the 25 minutes stated in the Roundhouse manual when hauling light-ish trains but I gave seen references to Berties having 40+ minute runs. The longest run I have achieved was 35 minutes on rollers, but the wheels periodically stopped rotating and then restarted themselves (I had both regulators turned down as far as I could).

More fundamentally, I have always assumed that the term "run time" starts when the loco moves its wheels/itself/its train for the first time and ends when it runs out of steam having exhausted the contents of its fuel tank, but are there other definitions in use?

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Re: Run time

Post by Keith S » Mon Jan 21, 2019 10:21 am

I have heard of "Millie" getting 40 minute runs, but that locomotive is externally fired and therefore carries more water than the other Roundhouse engines. "Bertie" of course is internally fired so carries less water. I think 25-30 minutes is pretty typical.

If you want to get the maximum amout of mikes from a fill, you can fill the boiler with pre-heated water, to reduce the time it takes to get up to working pressure. You can also wait till it's up to pressure, put out the fire, re-fill the gas tank and re-light it. Other than that though, I think 25 minutes on a fill is pretty good.

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Re: Run time

Post by CSL » Mon Jan 21, 2019 11:27 pm

Keith S wrote: Mon Jan 21, 2019 10:21 am If you want to get the maximum amout of mikes from a fill, you can fill the boiler with pre-heated water, to reduce the time it takes to get up to working pressure. You can also wait till it's up to pressure, put out the fire, re-fill the gas tank and re-light it. Other than that though, I think 25 minutes on a fill is pretty good.
I think I'd be a bit worried about running the risk of boiling dry as I understand the gas and water quantities complement each other but only if the water is heated from ambient temperature (although as I said it was cold at the weekend). I do preheat water when steaming my meths-fired Mamod SL3, but not with the Roundhouse loco.

Thanks for the reply - and the vote of confidence in my Bertie-handling skills!

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Re: Run time

Post by Keith S » Tue Jan 22, 2019 1:54 am

CSL wrote: Mon Jan 21, 2019 11:27 pm
Keith S wrote: Mon Jan 21, 2019 10:21 am If you want to get the maximum amout of mikes from a fill, you can fill the boiler with pre-heated water, to reduce the time it takes to get up to working pressure. You can also wait till it's up to pressure, put out the fire, re-fill the gas tank and re-light it. Other than that though, I think 25 minutes on a fill is pretty good.
I think I'd be a bit worried about running the risk of boiling dry as I understand the gas and water quantities complement each other but only if the water is heated from ambient temperature (although as I said it was cold at the weekend). I do preheat water when steaming my meths-fired Mamod SL3, but not with the Roundhouse loco.

Thanks for the reply - and the vote of confidence in my Bertie-handling skills!
Yeah, maybe a bit of experimentation is in order, especially the part about topping off the gas. I have however pre-heated the water in my "Billy" boiler, and it doesn't run dry.

Of course the amount of water you use will depend on how hard you make the engine work, and whether you are careful to keep steam from being wasted through the safety-valve. I turn the gas way down on the "Billy" and try to prevent it from blowing off. When the gas runs out, usually it can run 'round the oval (about 20m) without its train of course, on just residual heat and remaining water.

I don't bother topping off the gas. The extra couple of minutes of running aren't worth the bother.

P.S,, I don't get any "Mikes" from my engine. I meant to type "miles"!

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Re: Run time

Post by IrishPeter » Tue Jan 22, 2019 2:29 am

25-30 minutes is pretty typical of an internally fired locomotive, so I would say you are doing perfectly all right, Guv'nor. You can get a little more by keeping the burning turned well down once she is on the boil, and by going easy on the regulator which is good loco management, but there is no need to make a fetish out of it unless you want to.

Cheers,
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 » Tue Jan 22, 2019 7:31 am

Thanks for the replies. Makes me feel better!

Come to think of it I guess that the latent heat of vaporisation is probably more significant than start water temperature in the gas/water design calculation, so preheating the water may not be as risky as I thought (no water level sight glass on my Bertie though).

I think you're right about "bother" and "fetish" respectively: I know what's safe and your responses tell me I'm getting expected levels of performance and that's pretty much good enough for me!

I'll keep on trying to reduce wasteful gas and steam use - and carry on enjoying it.

Now to refettle that track...

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Re: Run time

Post by dewintondave » Sun Jan 27, 2019 6:21 am

It's interesting CSL. Your run stops when the gas runs out. I wonder how much water is remaining? Running the burner more efficiently will work, as will filling with warmer water. Trying various settings and measuring the remaining water will keep you safe from boiling dry
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Re: Run time

Post by IanC » Sun Jan 27, 2019 12:40 pm

In my experience run time will vary according to a number of factors. Ambient temperature, whether or not warm or hot water is used to raise steam. How high or low the gas is turned up (for gas fired locos - obviously) and the load. I only worry about running out of water before gas. I always try to avoid blowing off as this wastes water.
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Re: Run time

Post by GTB » Sun Jan 27, 2019 2:47 pm

dewintondave wrote: Sun Jan 27, 2019 6:21 am Your run stops when the gas runs out. I wonder how much water is remaining?
My rule of thumb with a Roundhouse boiler and burner is that 1ml of liquid butane (~0.6g) will turn 5ml of water at room temperature into 5g of steam at 40psi.

In the case of a Bertie, the gas tank holds 30.4ml of butane and the boiler fill volume is 225ml of water, so at the end of the run there will be around 70ml of water left. Usually the water level is just below the top of the flue after a run.

Refilling the gas tank when the boiler is up to pressure leaves less margin for error. A back of the envelope calculation suggests there would be only about 20ml of water left at the end of a run if the gas tank is refilled.

I time my testing from when I light the burner. At temps. in the 20 -25 degC range, my Bertie will be up to starting pressure in about 5 mins and will be out of gas at about 35 mins., so 30 mins. of actual running time by keeping the burner turned right down and the pressure around 30 psi.

It all depends on the size of the boiler and gas tank on a loco. As an example, the large boiler in a #24 has a water fill level of 320ml and takes longer to come up to pressure, but the gas tank is small (the same size as a Bertie). I routinely top off the gas tank on mine and the water is still above the top of the flue at the end of a 35 min run.

As always your mileage may vary............

Regards,
Graeme

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Re: Run time

Post by IrishPeter » Sun Jan 27, 2019 5:10 pm

Quoth Graeme: "As always your mileage may vary...."

Literally in this case! ;)

Sorry, couldn't resist.

Peter in Va
Last edited by IrishPeter on Mon Jan 28, 2019 12:29 am, edited 1 time in total.
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 » Sun Jan 27, 2019 7:43 pm

Also quoth Graeme:
GTB wrote: Sun Jan 27, 2019 2:47 pm I time my testing from when I light the burner.
Which might explain the 40-minute "run" times I've seen mentioned elsewhere!

Many thanks for the latest contributions. I'm still getting the impression that my engine management isn't deficient, which is good!

I may experiment with preheating the water, but personally I don't feel particularly comfortable with refilling the fuel tank. It's a hobby, not a game of chicken...

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Re: Run time

Post by GTB » Mon Jan 28, 2019 8:21 am

CSL wrote: Sun Jan 27, 2019 7:43 pm I may experiment with preheating the water, but personally I don't feel particularly comfortable with refilling the fuel tank. It's a hobby, not a game of chicken...
Filling with hot water reduces the time and amount of gas needed to come up to pressure, so might be worth it in very cold weather.

Refilling the gas tank is only a game of chicken if someone is unwise enough to do it with the burner lit.

You do need to be aware of water levels though and I really wouldn't recommend refilling a Bertie. While running out of water doesn't cause a boiler to explode unless the same unwise someone adds water while it is still very hot, but the results can be expensive.

Regards,
Graeme

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Re: Run time

Post by IrishPeter » Mon Jan 28, 2019 1:57 pm

Preheating the water does not gain you much. With a Bertie, I would say no more than 2 or 3 minutes. However, when it is freezing the bell off a bike it might be worth it to help keep the gas consumption somewhere close to normal.

The only loco I ever top off the gas on is my Millie, which seems to have adequate water capacity for topping off being a pot boiler; otherwise it is a bit of a crap shoot as to whether you will boil the boiler dry, and I don't like the idea of doing that. One problem you will run into in cold weather is that straight butane becomes sluggish at around 50F/10C, so in cold weather I use mixed gasses (usually 70/30) as the addition of propane to the mix makes the liquification point quite a bit colder. I assume you know not to use mixed gases if the loco gas tank is marked butane only - the pressure the butane-propane mix is stored at is quite a bit higher than that of straight butane.

Cheers,
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 artfull dodger » Tue Feb 05, 2019 6:08 pm

I used to get a touch over 30 min from my run in Bertie. But she had a upgraded safety valve that popped off properly instead of weeping and wasting steam. Something the RH safety is good for. I also kept the gas turned right down after boiler pressure was reached. This had to be adjusted 2 or 3 times thru the run as the gas tank got hotter from boiler heat and the gas pressure rose from that heat. I kept the gas right at a whisper, almost silent. Now my Regner Stainz can run nearly an hour on a gas fill, but several stops for water(has a sight glass)is required as the model has a small boiler as its built to scale. A gentleman in our steam group has a Millie and on an indoor layout with no wind, he can get 45 min runs from Millie. He also runs the better safety, sourced from Wee Bee Locomotive Works and keeps his gas turned right down once boiler pressure is reached. When we steam outdoors in the late fall at a steam up. We keep a tea pot with water on a hot plate to fill tenders and boilers with as ice cold water will wipe out steam pressure and it tends to be quite chilly at that steam up normally. Mike
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Re: Run time

Post by cooltrain » Wed Feb 06, 2019 5:09 am

With my Roundhouse Billy I have achieved a run of 55 minutes, counting from after the loco reached working pressure. This was with the gas turned right down on a level track with wide radius curves and the pressure sitting between about 5 and 20psi. Would happily creep around with a light train with only 5psi on the clock without strain.

My usual practise is to run my locos on 20psi, which gives me a run of about 30-40 minutes. By running at 20psi it means you can avoid having the safety valve lifting constantly.
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Re: Run time

Post by artfull dodger » Wed Feb 06, 2019 4:30 pm

Excellent run times of your Billy! Keeping the safety from wasting steam from lifting or weeping is key to long run times, just as keeping the gas turned right down.So many have no clue about this and steam around the track with the burner roaring and the safety lifted. Learning each engines quirks and mannerisms is part of the fun and the lure of live steam. These little beasts are alive, just as the old timers drivers described full size locomotives back in the glory days of steam. Then you take the next step and add a goodall or boiler refeed valve. Then you can remain in steam all day if you so desire, topping up water, steam oil and gas as needed. Spending your time at station stops tending your engine just as the driver and fireman do in 1:1 scale. Life is great!
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Re: Run time

Post by CSL » Fri Feb 08, 2019 4:41 pm

Interesting thought about the pop safety valve - I hadn't thought of that and it does rather appeal.

On the other hand, with a ground-level/slightly raised railway and young children about, maybe not quite yet!

My Bertie is basic spec - no pressure gauge, so a bit tricky to keep to a particular low boiler pressure.

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Re: Run time

Post by artfull dodger » Fri Feb 08, 2019 8:04 pm

The upgrade "pop" style safety valve just prevents the steam wasting from a valve that by design doesn't seal well so it wisps steam constantly instead of releasing at a specific pressure then resetting till pressure rises again. Ground level or raised doesn't matter much. 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
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Re: Run time

Post by Tom the blacksmith » Fri Feb 08, 2019 8:14 pm

CSL wrote: Fri Feb 08, 2019 4:41 pm Interesting thought about the pop safety valve - I hadn't thought of that and it does rather appeal.
I thought exactly the same, I've noticed a fairly constant weeping from the RH safety valve. Are there any equivalent replacements available this side of the pond?

Lovely conversion on your Sammie Mike :thumbup: :thumbup:

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Re: Run time

Post by tom_tom_go » Fri Feb 08, 2019 8:54 pm

Tom the blacksmith wrote: Fri Feb 08, 2019 8:14 pm I thought exactly the same, I've noticed a fairly constant weeping from the RH safety valve.
When you say it constantly weeps at what pressure (and is your pressure gauge working accurately?).

On a gas loco you should be able to easily control the pressure without the safety valve going off once the loco is settled into the run.

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