To notch or not to notch

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Hydrostatic Dazza
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Re: To notch or not to notch

Post by Hydrostatic Dazza » Thu Aug 16, 2018 10:15 pm

Not much I can add to this as others have told all, but a Slomo in my mind is a must for enjoyable slow running and sweet shunting. Garden choo choos have buggar all mass and the mass of it all is the physics of this gig. A Slomo adds a wee bit more mass but by using the well known use of a fly wheel the mass (spun up) is amplified many times. It does not add any measurable friction! The bearings and gears are free running. The only way I can see that you can flog out your loco's motion when using a Slomo is if you try to accelerate the loco like a F1 off the starting grid and stopping like one, thus you are fighting to spin up and slow down the fly wheel. The flywheel sort of thing has been in HO model railways for 50 years in the USA. (that I can recall reading about it in Model Railroad Craftsman magazines) I discovered Slomo for my choo choo build after I had fitted my pump eccentric and wheels and cranks and all is pinned.
Sigh!
So the loco is now to be a tender loco with the Slomo fitted and the tender Slomo is chain driven. (which takes up more space)
As for notching up (cut off), as said by others. I am not proclaiming to be an expert, however I did spend considerable time in the evenings with books, CAD and the simulators to get a better understanding of it all. Simply it is about greater expansive working of the steam in the cylinder by cutting off the admission of the steam via the variable valve events. Referred to as "Notching up" A cab fitted pole reverser has a pawl to engage the notches in the sector plate to give the driver various selections. A screw reverser does not have notches (but for locking purposes) but the process is still called notching up. For starting one wants lots of torque with the slow piston speed and then as the loco moves one notches up, to increase the expansive working and due to other factors of what is going on in the cylinders and valves notching up will allow greater speed. There is a lot of other things going on in cylinders and steam and radial valve gears, such as Stephenson's (he ripped it off some one else) and Walschaert's which mean there has to be compromises and the knack is designing with all of these in mind. (not always done very well in Model Engineering designs and even the full size loco designers had problems understanding valve gears) There is lots going on such as compression, lead, wire drawing at speed etc etc. I can happily report my Llewellyn # 1 when running on air, notches up nicely and the speed of the unloaded motion speeds up (as it should) and when getting closer to mid gear the motion gets a wee bit jerky due to compression along with the truncated exhaust note. That all pleased me.
Cheers from Dazza, The Hydrostatic Lubricator 8)
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Re: To notch or not to notch

Post by Keith S » Fri Aug 17, 2018 8:02 am

I suspect some people refer to "friction" with respect to the "Slomo" because flywheel mechanisms in toys are sometimes called "friction motors".

https://en.m.wikipedia.org/wiki/Friction_motor

One proposed method of "taming" small steam locomotives DOES involve friction, and that is the centrifugal brake, which works quite well. The mechanism from an old rotary-dial telephone has been successfully deployed as a centrifugal brake in some live-steam models.

For those who are allergic to radio-controllled locomotives, the ideal combination, it would seem to me, would be a flywheel van (or SLOMO) to control accelleration, as well as a centrifugal brake wagon to limit top speed.

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Re: To notch or not to notch

Post by TonyW » 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.
Tony Willmore
Rhos Helyg Locomotive Works: http://www.rhoshelyg.me.uk
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Re: To notch or not to notch

Post by tom_tom_go » Fri Aug 17, 2018 11:57 am

I agree with Tony that with a well laid level track, long sweeping curves, appropriately weighted rolling stock and a correctly set up live steamer with R/C then you can achieve realistic running providing you have a continuous circuit.

However, I am unlikely to ever own a property that can accommodate such a railway so the Slomo allows me to run realistically on a small line with tight curves and run around light engine at a speed that's not trying to get me into orbit.

If the SSP Slomo had not been brought to market I would of probably sold up years ago.

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Re: To notch or not to notch

Post by TonyW » Fri Aug 17, 2018 12:17 pm

tom_tom_go wrote: Fri Aug 17, 2018 11:57 amIf the SSP Slomo had not been brought to market I would of probably sold up years ago.
I am a big believer in the phrase "horses for courses".
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Re: To notch or not to notch

Post by JMORG » Fri Aug 17, 2018 12:43 pm

We have a member with a slomo fitted Katie and summerlands chuffer and he says that he is slightly disappointed that the slomo makes an audible whine when in operation; fitted by one of the professional locomotive modifiers.

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Re: To notch or not to notch

Post by tom_tom_go » Fri Aug 17, 2018 12:46 pm

TonyW wrote: Fri Aug 17, 2018 12:17 pm
tom_tom_go wrote: Fri Aug 17, 2018 11:57 amIf the SSP Slomo had not been brought to market I would of probably sold up years ago.
I am a big believer in the phrase "horses for courses".
Indeed, the world would be boring if we all did the same thing.

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Re: To notch or not to notch

Post by tom_tom_go » Fri Aug 17, 2018 12:50 pm

JMORG wrote: Fri Aug 17, 2018 12:43 pm We have a member with a slomo fitted Katie and summerlands chuffer and he says that he is slightly disappointed that the slomo makes an audible whine when in operation; fitted by one of the professional locomotive modifiers.
The Slomo for Katie, Billy, etc is chain driven so that is likely the noise. The version for Lady Anne does not use a chain drive which makes it quieter (watch one of my many YouTube videos of both my Silver Lady and Riverdale Amy to hear).

The sound from the chain drive version doesn't bother me and will be amplified in any videos you watch of it in action. Besides, steam engines make all sorts of noise after all...

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Re: To notch or not to notch

Post by Keith S » Fri Aug 17, 2018 5:21 pm

TonyW wrote: Fri Aug 17, 2018 10:26 am
The video is interesting. A shame we cannot see the pressure gauge, but enough evidence is there of what is happening.


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.
.
The loco in the video wants its timing adjusted, that's why its running is "lumpy" without the slomo. You can hear the exhaust beats are not evenly spaced throughout a full rotation of the axles. It always stops at the same spot because the valve events are not evenly distributed. If you could see the opposite side, the cylinder would be at TDC or BDC. The cylinders are working against each other in that spot. The flywheel smooths over these events, as a flywheel should. Slomo or no slomo, it drives me nuts watching a video in which the locomotive has poorly adjusted timing. Such engines are usually incapable of slow running without a flywheel, and when they start up they need more steam, and so on manual engines that's one reason they build up so much pressure before taking off like a rabbit. On the other hand the flywheel makes the exhaust beat louder, and makes a poorly adjusted engine less annoying to drive but much more annoying to listen to.

Dazza, I believe you'll not suffer from having the "Slomo" in your tender rather than on the main axles. With a solid drawbar between the two vehicles, the slomo should have exactly the same effect, other than you may possibly be prone to a bit of wheel-slip if you aren't careful, which is realistic anyway isn't it. Personally, I am a proponent of having the flywheel in a seperate vehicle altogether, because (1) I am too mean to buy more than one; (2) I believe it's the train, and not simply the loco that needs momentum added, and (3) my locomotive is manual and I prefer to watch it trundle around rather than doing any shunting.

Of course, living as I do in a horrible arctic wasteland, I do not have access to any railway friends, nor any railways to run my stuff on, other than the feeble circle of track I have presently lifted and stored away. My hobby consists mostly of building and running back and forth on my bench. Perhaps therefore my opinion isn't as valid as that of others.
Last edited by Keith S on Fri Aug 17, 2018 5:23 pm, edited 1 time in total.

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Re: To notch or not to notch

Post by tom_tom_go » Fri Aug 17, 2018 5:22 pm

TonyW wrote: Fri Aug 17, 2018 10:26 am
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.
I have to say that I have not experienced this with either my gas or coal fired locos so I can only assume the loco is not set up correctly. If anything, I use less gas, coal and water as the locos are running slower.

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Re: To notch or not to notch

Post by TonyW » Fri Aug 17, 2018 7:44 pm

tom_tom_go wrote: Fri Aug 17, 2018 5:22 pm
TonyW wrote: Fri Aug 17, 2018 10:26 amLast year I fitted a Slomo...
... I can only assume the loco is not set up correctly.
Errr... thanks Tom. I love you too.

It was set up correctly when it left here. I could tell it was as it sounded like a Blackpool tram. (A joke, but it did sound like a Blackpool tram).

I can only report what the owner says.
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Re: To notch or not to notch

Post by tom_tom_go » Fri Aug 17, 2018 8:06 pm

Hi Tony,

I am not suggesting you have done anything wrong, you were asked to fit a Slomo to a 20 year old loco.

As an owner of your work I can say that a Slomo in a chassis set up by you runs perfectly :thumbup:

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Re: To notch or not to notch

Post by TonyW » Fri Aug 17, 2018 11:51 pm

tom_tom_go wrote: Fri Aug 17, 2018 8:06 pm Hi Tony,

I am not suggesting you have done anything wrong, you were asked to fit a Slomo to a 20 year old loco.

As an owner of your work I can say that a Slomo in a chassis set up by you runs perfectly :thumbup:
:thumbup: :P

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Re: To notch or not to notch

Post by dewintondave » Sat Aug 18, 2018 7:35 am

Keith S wrote: Fri Aug 17, 2018 8:02 am For those who are allergic to radio-controllled locomotives, the ideal combination, it would seem to me, would be a flywheel van (or SLOMO) to control accelleration, as well as a centrifugal brake wagon to limit top speed.
I like to use an electric shunter at the back of the train to hold the loco back, and to clear the initial condensate and start the train. It frees up a hand so that I can catch the gunk coming out of the funnel
Best wishes,
Dave

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Re: To notch or not to notch

Post by dewintondave » Sat Aug 18, 2018 7:38 am

tom_tom_go wrote: Fri Aug 17, 2018 11:57 am If the SSP Slomo had not been brought to market I would of probably sold up years ago.
Gauge 1 guys like to drive fast, you could've joined the dark side? :D
Best wishes,
Dave

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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.
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