To notch or not to notch

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tom_tom_go
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Re: To notch or not to notch

Post by tom_tom_go » Sat Aug 18, 2018 9:08 am

You reminded me Dave of this video by Chris Bird:



I did try this when I had a Regner and a continuous run, it worked quite well (this method is definitely causing drag for the Roundhouse loco which a Slomo does not) :mrgreen:

Even if I had sold up I probably would not have enough money to buy a complete Gauge 1 train!

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Re: To notch or not to notch

Post by dewintondave » Sun Aug 19, 2018 5:40 am

Very nice Tom.

Here's mine. The beauty is that you can turn up the regulator, keeping the cylinders hotter, and improving the chuff - no chuffer fitted to this loco.



The initial intention of using the diesel was to help a steamie up the difficult bits. So if this was balanced there'd be no drag on the steamie either ;)
Best wishes,
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Re: To notch or not to notch

Post by steveh99 » Sun Aug 19, 2018 4:14 pm

TonyW wrote: Fri Aug 17, 2018 10:26 am
steveh99 wrote: Thu Aug 16, 2018 10:53 amOnly a slomo will give controlled acceleration and de-accerlaration and allow for a smooth slow running performance
Only? I don't think so. A properly set up loco fitted with radio control and with a boiler pressure commensurate with what it is being asked to do will also give smooth slow running performance. Performance is certainly good enough for garden railway operation, but I would agree that the Slomo is essential for the exhibition-style running that Steve does.

Last year I fitted a Slomo to a 20-year old Roundhouse Jack that the owner bought new. He is delighted with the performance but reports that he needs a higher boiler pressure and more regulator to "unstick" it, and that has reduced his length of run per gas fill from 45 minutes to 25 minutes.

The video is interesting. A shame we cannot see the pressure gauge, but enough evidence is there of what is happening.

One of the advantages of a stick-type controller over a knob-type is that it is possible to use the loco's regulator as a full-size one would be used, i.e. open a bit, back off, open a bit more, back off, etc. What we see in the video is the valve chests being filled with 40psi (safety valves lifts at 01:40) and the thing taking off at speed. That does not surprise me. If you did similar with a full-size loco it would just go in to a monster wheelslip.

We'll ignore the hotly-debated "does a chuffer pipe create back-pressure" issue, but there is something odd going on with the loco's chassis. In non-slomo mode every time it stops, in both forward and reverse, the eccentric on the back axle is pointing to the 8 o'clock position. Every time. This indicates to me that there is some kind of mechanical binding issue at that point in the rotation cycle, so the loco has to overcome that bind *before* it does anything else and needs steam pressure in excess of what is normally needed to do so.

Note that the regulator opens wide - very wide - so filling valve chests and superheater with full pressure steam on a mechanically unsound chassis, so the non-slomo performance was bound to fail. It could not do anything else. I think all the video demonstrates is how NOT to drive a non-slomo loco! Heavy-handed regulator control and excess steam pressure (turn the gas down, save money and increase run time) are never going to be good. Perhaps then another advantage of the slomo is that it copes with drivers who don't know how to drive...?

The other component missing is momentum. The rolling road is a different situation compared to using a loco on track.

OK, so I didn't choose the best loco and agree its a bit off, I didn't notice as I always run with a slomo. I have been to many exhibitions and garden railways and seen many different drivers and many different locos and without a slomo, none of them come close to the sort of performance a slomo provides.

I personally don't like stick controls as the movements required are tiny, but hey-ho, each to their own.

I can't usually run at less then 40psi on my Hambleden layout because the locos spend a lot of time stationary or running slowly not very far. The gas is a low as it will go without going out, quite difficult to achieve in a noisey exhibition hall. I accept it is different on a continous run in the garden. On my layout I still 35-40min run time from a gas tank fill.



If anyone can better this without a slomo, paste your video here. I don't have anything else to say on this subject

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Re: To notch or not to notch

Post by tom_tom_go » Sun Aug 19, 2018 5:04 pm

To add to Steve's post (brilliant timing) I wanted to show that I can push and pull my locos using my fingers:


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Re: To notch or not to notch

Post by TonyW » Sun Aug 19, 2018 7:09 pm

steveh99 wrote: Sun Aug 19, 2018 4:14 pmI have been to many exhibitions and garden railways and seen many different drivers and many different locos and without a slomo, none of them come close to the sort of performance a slomo provides.
While I could probably not match exactly the performance shown in the new video you too are welcome to visit here any time.
Tony Willmore
Rhos Helyg Locomotive Works: http://www.rhoshelyg.me.uk
Facebook: https://www.facebook.com/RhosHelygLocoWorks

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Re: To notch or not to notch

Post by steveh99 » Sun Aug 19, 2018 9:56 pm

Thanks Tony,
would love to
rgds

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Re: To notch or not to notch

Post by Keith S » Mon Aug 20, 2018 4:39 pm

Of course a Slomo or any other flywheel contraption "adds drag" or makes the locomotive works harder. To think otherwise is to ignore what you know about mechanics. When you turn off the steam, the engine coasts farther than it would have without the flywheel. Where do you think that extra work came from? It was put there by the engine, by work it did at the beginning. Luckily steam engines have a very broad "torque band" and you can load it up with a flywheel and still pull your train. But the engine is still doing more work, and the mechanism including the bearing surfaces in the rods is being subjected to more wear. It cannot be otherwise. You might of course consider this to be a worthwhile trade-off to the reduced wear you may experience in other areas such as the pistons and axle bushings as a result of the engine not thrashing about at ludicrous speed the way it might without the flywheel, but yes your engine is doing more work imparting momentum to that flywheel as it chuffs about. If you watch all the videos from the "Slomo" guy's channel, you will see he has bushed his driving rods.

I'm not casting shade on the flywheel idea, I have one in a van myself and do not run without it- there is no doubt it increases the enjoyment of running realistically. But I believe it will reduce the lifespan of the driving rods and crank pins. Luckily they are relatively cheap. And you'd have to run your engine A LOT to wear out a set anyway.

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Re: To notch or not to notch

Post by Hydrostatic Dazza » Mon Aug 20, 2018 11:28 pm

For the readers of this thread, I hope to explain this with the clarity intended.
Flywheels are not friction or drag devices. When a Slomo mech (Loco) is at a constant speed there is no more measurable friction, or resistance, or drag than a loco not equipped with a Slomo. The only friction in a Slomo mech is the bearings and gears and this is very minimal due to sealed ball races etc. ( I think we can count out aerodynamic drag of the Slomo mechs components for all intents and purposes) The only imparted or released energy is when you are changing the speed of the flywheel.


Newtons First law: In an inertial frame of reference, an object either remains at rest or continues to move at a constant velocity, unless acted upon by a force.

"A flywheel is a mechanical device specifically designed to efficiently store rotational energy. Flywheels resist changes in rotational speed by their moment of inertia. The amount of energy stored in a flywheel is proportional to the square of its rotational speed. The way to change a flywheel's stored energy is by increasing or decreasing its rotational speed by applying a torque aligned with its axis of symmetry,

Common uses of a flywheel include:

Smoothing the power output of an energy source. For example, flywheels are used in reciprocating engines because the active torque from the individual pistons is intermittent.
Energy storage systems
Delivering energy at rates beyond the ability of an energy source. This is achieved by collecting energy in a flywheel over time and then releasing it quickly, at rates that exceed the abilities of the energy source.
Flywheels are often used to provide continuous power output in systems where the energy source is not continuous. For example, a flywheel is used to smooth fast angular velocity fluctuations of the crankshaft in a reciprocating engine. In this case, a crankshaft flywheel stores energy when torque is exerted on it by a firing piston, and returns it to the piston to compress a fresh charge of air and fuel.
"


Which is what occurs with a Slomo mech in a little choo choo due to the little Choo Choos lack of mass to carry momentum over dead strokes, binds etc. The fly wheels stores and releases energy when diving forces fluctuate. Flywheels do not make energy or eat it.
If you accelerate or de-accelerate your Slomo loco hard you will of course have resistance as the fly wheel wants to stay in its stationary state or, if it is in motion it wants to stay in its constant motion.
Newtons first law. If it is mounted to the drive axle, (the best way if all things are considered) then you can load up the motion from piston to big end on the driver. This amount is pending how you drive your loco, ie: F1 start and stop or do it gently. There is no more load on the valve gear ever. No more loads on the axle boxes or coupling rods if the Slomo mech is on the driving axle. The easier your drive your loco the lower the peak forces will be when accelerating or de-accelerating. Just like driving your car, accelerate gently and brake gently. So open the throttle gently and when stopping, do not slam the throttle closed, ease it back slowly and judge your stops. Real driving with care eh! Double the rates of change and you cube the loads. Often the problem of wear is due to price considerations of manufacturing with the use of brass bearings and or steel on steel as in rods on crank pins etc. Now for me, I made my loco with Phosphor bronze bushes, silicon bronze and case hardened some pins. Not brass, no steel on steel, but for valve motion parts due to size restraints. Now if the Slomo is on the tender then the rods to the other driving wheels will get some more load but again, very small amounts if you drive gently.
You can increase the train load, more on the hook, more mass, more bearing/wheel friction and work the engine harder against this and you may have a more realistic motion, (as reported) but then you will certainly load up the motion constantly and thus have increased wear rates. Having said all this, steam engines wear out, they flog themselves along the track. If you do not want incurred wear, leave them on the mantle .
I am also weary of anecdotal reports of what occurs because there are so many unmeasured or unrecorded variables, the locos set up and condition, driving technique etc etc. The plural of anecdote does not = fact.
Cheers from Dazza, The Hydrostatic Lubricator 8)
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Re: To notch or not to notch

Post by Keith S » Tue Aug 21, 2018 2:36 am

I wasn't aware we were talking about a locomotive travelling at a constant speed. Sure there's no additional work being done with a flywheel at a constant speed. Is that why you have a slomo?

Pedantic Newtonian paraphrasing or no, you would have us believe that it's just as easy to turn a crank driving a grindstone via speed multiplier gears as it would be to turn a crank with nothing attached to it.

I shall hire you to grind grist at my mill, until the wheel is up to speed, that is, then I will be more than happy to take over.

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Re: To notch or not to notch

Post by Hydrostatic Dazza » Tue Aug 21, 2018 5:15 am

Keith S wrote: Tue Aug 21, 2018 2:36 am I wasn't aware we were talking about a locomotive travelling at a constant speed. Sure there's no additional work being done with a flywheel at a constant speed. Is that why you have a slomo?

Pedantic Newtonian paraphrasing or no, you would have us believe that it's just as easy to turn a crank driving a grindstone via speed multiplier gears as it would be to turn a crank with nothing attached to it.

I shall hire you to grind grist at my mill, until the wheel is up to speed, that is, then I will be more than happy to take over.

Hence you crank hard to accelerate it all up to a stable (desired) speed and when this desired speed is reached and then the force is reduced to an amount to keep it at the stable speed, and that is the balance of resistances (friction) and your cranking force. Much less than required to accelerate the mass.
The speed of this acceleration is dependent on how much force you apply to accelerate the stationary grind stone ( its mass) There is math for this but I have long forgotten this from my school days
The only drag is bearing friction, stones rubbing and the air on the moving parts etc. Mass does not have friction.
Cheers from Dazza, The Hydrostatic Lubricator 8)
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Re: To notch or not to notch

Post by Keith S » Tue Aug 21, 2018 9:24 am

It turns out I've been confusing what the word "drag" means. You're right, it's not "drag". The whole point to any device that attempts to make a toy engine act realistically isn't to resist motion, it's to resist acceleration. A friction device resists acceleration by resisting motion, and it applies a greater force parallel and opposite to the force applied by the locomotive in the direction of movement as speed increases. It will limit top speed. A flywheel device resists accelleration by absorbing a percentage of the force applied in the direction of motion by the locomotive and storing it in the form of angular momentum. It will not limit top speed. Therefore you are correct to say the Slomo does not add "drag" to the locomotive. However, during acceleration, there is more work being done to produce a given rate of increase in speed than there would be if the locomotive was not equipped with a flywheel and was simply being driven very carefully. There is greater force being applied to the crank, and therefore more wear is occurring. It may be your contention that it is not possible to control an engine carefully enough to create the same realistic accelleration as the Slomo does. I agree with you there. I believe slightly increased wear is the price you pay for the advantages of the Slomo, or the flywheel van that I use. Also, my engine is manually controlled, so I do put the regulator where I think it ought to be for the speed I want, and can't "drive" it.

God, I'm a bore. I think I've been arguing with myself because I imagined someone saying the flywheel device doesn't increase wear over time, and I have been arguing with that imaginary person. Enjoy your trains. Thanks for the discussion.

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Re: To notch or not to notch

Post by Hydrostatic Dazza » Tue Aug 21, 2018 10:15 am

Keith S wrote: Tue Aug 21, 2018 9:24 am It turns out I've been confusing what the word "drag" means. You're right, it's not "drag". The whole point to any device that attempts to make a toy engine act realistically isn't to resist motion, it's to resist acceleration. A friction device resists acceleration by resisting motion, and it applies a greater force parallel and opposite to the force applied by the locomotive in the direction of movement as speed increases. It will limit top speed. A flywheel device resists accelleration by absorbing a percentage of the force applied in the direction of motion by the locomotive and storing it in the form of angular momentum. It will not limit top speed. Therefore you are correct to say the Slomo does not add "drag" to the locomotive. However, during acceleration, there is more work being done to produce a given rate of increase in speed than there would be if the locomotive was not equipped with a flywheel and was simply being driven very carefully. There is greater force being applied to the crank, and therefore more wear is occurring. It may be your contention that it is not possible to control an engine carefully enough to create the same realistic accelleration as the Slomo does. I agree with you there. I believe slightly increased wear is the price you pay for the advantages of the Slomo, or the flywheel van that I use. Also, my engine is manually controlled, so I do put the regulator where I think it ought to be for the speed I want, and can't "drive" it.

God, I'm a bore. I think I've been arguing with myself because I imagined someone saying the flywheel device doesn't increase wear over time, and I have been arguing with that imaginary person. Enjoy your trains. Thanks for the discussion.
YES, we are on the same page.
discussing is always a good thing.
Cheers from Dazza, The Hydrostatic Lubricator 8)
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Re: To notch or not to notch

Post by tom_tom_go » Tue Aug 21, 2018 8:02 pm

I keep reading that a SSP Slomo causes more wear to a loco than one without. Does it cause more wear than say adding an extra wagon or two to a train or driving your loco on demanding track with gradients?

Until a SSP Slomo has been fitted to a brand new loco then the same loco purchased without a Slomo and then they are run in identical conditions over a period of time (talking years) to compare 'wear' then the statement of a Slomo causes more wear is false.

Please read the following:

http://smallsteamperformance.com.au/wear-issues/

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Re: To notch or not to notch

Post by Hydrostatic Dazza » Tue Aug 21, 2018 11:01 pm

tom_tom_go wrote: Tue Aug 21, 2018 8:02 pm I keep reading that a SSP Slomo causes more wear to a loco than one without. Does it cause more wear than say adding an extra wagon or two to a train or driving your loco on demanding track with gradients?

Until a SSP Slomo has been fitted to a brand new loco then the same loco purchased without a Slomo and then they are run in identical conditions over a period of time (talking years) to compare 'wear' then the statement of a Slomo causes more wear is false.

Please read the following:

http://smallsteamperformance.com.au/wear-issues/

Yes, I am not yet convinced a Slomo mech causes more noticeable or measurable wear if one drives the loco gently and not forcing the flywheel up to speed quickly and also when slowing so the peak forces are kept low. Just as if you were driving or controlling anything with care.
As you say, I want to see data. Measurements taken of two new locos, one with fitted Slomo and one with out. Then control as far as possible all the conditions and variables. Record all. Then after time has passed, take measurements of the parts.

"I am also weary of anecdotal reports of what occurs because there are so many unmeasured or unrecorded variables, the locos set up and condition, driving technique etc etc. The plural of anecdote does not = fact."
Cheers from Dazza, The Hydrostatic Lubricator 8)
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Re: To notch or not to notch

Post by dewintondave » Wed Aug 22, 2018 8:02 am

It will cause extra wear, because it's an extra load for the loco. Anyway, if one can afford a ssp slomo, one can afford repairs :D
Best wishes,
Dave

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Re: To notch or not to notch

Post by tom_tom_go » Wed Aug 22, 2018 8:10 am

dewintondave wrote: Wed Aug 22, 2018 8:02 am It will cause extra wear, because it's an extra load for the loco. Anyway, if one can afford a ssp slomo, one can afford repairs :D
Running a loco with a heavy train causes extra wear as well :mrgreen:

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Re: To notch or not to notch

Post by TonyW » Wed Aug 22, 2018 1:47 pm

tom_tom_go wrote: Wed Aug 22, 2018 8:10 amRunning a loco with a heavy train causes extra wear as well :mrgreen:
Which is, of course, another solution!

Want to tame your loco? Put a bigger train behind it.

Want your loco to chuff louder? Put a bigger train behind it.

:D

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Re: To notch or not to notch

Post by Keith S » Wed Aug 22, 2018 5:11 pm

The best way to avoid wear, as well as to make the most efficient use of a given quantity of butane or coal, is to leave the loco on a shelf and dust it off once in a while. This is what I do, and this style of running induces practically no wear to the running gear, uses very little butane, and the locomotive goes very slowly indeed. It's been on the shelf about a year now and the engine hasn't even moved far enough to run the slack out of the coupling chains. I have to admit, the chuff is extremely quiet however.

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Re: To notch or not to notch

Post by IanC » Wed Aug 22, 2018 8:32 pm

Keith S wrote: Wed Aug 22, 2018 5:11 pm The best way to avoid wear, as well as to make the most efficient use of a given quantity of butane or coal, is to leave the loco on a shelf and dust it off once in a while. This is what I do, and this style of running induces practically no wear to the running gear, uses very little butane, and the locomotive goes very slowly indeed. It's been on the shelf about a year now and the engine hasn't even moved far enough to run the slack out of the coupling chains. I have to admit, the chuff is extremely quiet however.
:thumbright: :lol: :lol: :lol: That's so very true. I don't run my locos enough to wear them out in my lifetime. With or without a slomo or running big trains.
Ian

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Re: To notch or not to notch

Post by dewintondave » Wed Aug 22, 2018 9:28 pm

tom_tom_go wrote: Wed Aug 22, 2018 8:10 am Running a loco with a heavy train causes extra wear as well :mrgreen:
Running a heavy train with a slomo equipped loco would be like cruelty to engines 💪
Best wishes,
Dave

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