Hornby Steam locomotives - with / without flywheel?

[atom3624]

Possibly a sensitive question for some?

I know virtually all of my diesel locomotives - and electric - have flywheels, and have noticed a phenomenon.

 

Despite being skew wound, well maintained, etc., it's difficult to maintain a smooth, continuous very slow crawl.

 

I've also noticed that many Hornby steam locomotives, until relatively recently, have long-had the skew-wound 5-pole motors, but without flywheels. When run-in / loosened up they are superb crawlers.

 

Cheaper-fit 3-pole motors are fitted to some Railroad locomotives, and with flywheels.

These are also fitted to some 'overlap' locomotives I think - like TTS A1 Tornado and P2.

These are relatively smooth in operation, but cannot start and maintain a smooth, slow crawl.

 

A recent trend has been to fit flywheels to many of the motors in steam locomotives.

My recently purchased B12 is a fantastic performer, but has 'that inertia thing' with the entire driveshaft of the motor possibly being twice as heavy or more than it would have been without the flywheels, thus a stall current (?) greater than ideal is required to get it moving, which creates a slight jerk, and similarly cannot crawl very slowly, perfectly.

 

A similarly purchased, loco-driven B17/6 has no flywheel, and has just crawled perfectly.

I can understand the 'permits smoother stops if the power is cut' considerations, but that is after the horse has bolted - better to sort out the power supply.

 

Thoughts?

I prefer without flywheel.

 

Al.

[No Decorum]

Interesting. I have tended to prefer flywheels whilst recognising that they don’t aid very slow running. When Hornby went all design clever, one of the worst features was the motor. They were three pole. Not that three-pole motors are necessarily bad but Hornby seemed to get a supply of very inconsistent ones and, instead of dumping the poor ones, added a flywheel to try to disguise the rotten performance. The return of five-pole, skew-wound motors is very welcome. Hornby’s shortcomings in relation to DCC have been well aired but, credit where it’s due, the present Hornby chassis design seems to be just that bit quieter and smoother than any other manufacturer’s.

[34theletterbetweenB&D]

Pull the flywheels off. I have done this on several models, typically to increase loco weight rather than for smooth starts, as DCC totally masks the difference with/without flywheel(s).

[NCB]

I'm not a fan of flywheels either. You get a torsion effect as though something is being wound up, then released. Can get the same sort of thing if a body is too heavy for the drive. No real movement then a rush.

 

Nigel

[atom3624]

Unusual for me, all generally in agreement!

 

Thanks for the thoughts and input.

 

Al.

[31A]

There's always one with an alternative point of view!  I've been a big fan of flywheels in model locos for many years, from when I used to build locos from kits, and discovered what a big improvement they brought to slow running.  Possibly the motors I used then weren't as good as motors that are available now, although they were usually Mashimas (1024 usually).

 

Case in point regarding Hornby locos is the D16/3, of which I have two.  As bought, they were not bad runners but 'jittery' at slow speed, and poor starters particularly when running light.  Following advice on here (a couple of people have posted the same advice) I replaced the motors with the type intended for the K1, which is a direct replacement but is fitted with a flywheel.  The running is transformed!  Both locos now run beautifully at all speeds, including smooth slow starts.  The motor has a different part number, but as far as one can tell from the outside is the same motor fitted with a flywheel.  The D16/3 mechanism block includes a recess for a flywheel, as if it was originally intended to provide one but for some reason it wasn't.  The K1 is also a very smooth runner.  Not all of us use DCC, nor want to.

[atom3624]

I'm on DC only, at the moment.

 

I just had a go of the new B17/6 and the B12 - without and with flywheel.

 

I have to admit, there was little difference between the 2 - perhaps as anticipated, the B17/6 was better at the very slow speed.

From an acceptably slow speed start, say 6" per revolution, there wasn't any difference.

 

I still stand by my original comments nevertheless.

 

Al.

[The Johnster]

I have for many years thought that flywheels were A Good Thing, enabling smoother running when pick up is interrupted, such as dead frogs (I like my wiring simple) and the poorer pickups on loco in the olden days.  But good tracklaying, effective modern pickups to all wheels, better motors and other improvements have reduced the need for this, and I have had a rethink.  The desired effect is smooth starts and stops and reliable, controllable, consistent slow running; I do a lot of shunting on my smallish BLT and there is no need on such a layout for anything more than about a scale 25mph.  

 

I'm asking a lot of my locos, all steam outline mostly 6-coupled.  I am a poor pensioner and cannot afford DCC, so my DC locos are required to start smoothly under load and be controllable at normal shunting speeds or lower.  Shunting at places like Cwmdimbath took place at a little above walking pace as there's no point rushing about and then having to wait for the guard to walk to the points he has to throw or the length of the train to uncouple the van after he's thrown them or whatever. Any movement on roads where men may be unloading vehicles must be done with extreme caution, particularly into goods sheds where the driver cannot see what is going on inside the shed.

 

Put another way, that means that I need the best slow performances at the very time when voltage is low and mechanical resistance and inertia are at their highest.  A flywheel sounds like a good idea, but it makes the movement harder to start, though technique can be developed to crank up the voltage until the loco begins to move and back it off immediately to give just enough voltage to keep her on the move, then you can accelerate gently under control.  Picking up a raft of loose couple loaded coal wagons in this way requires a bit of actual skill and is very satisfying once it's mastered, especially if the loco might slip a little if you are overenthusiastic...

 

So, what I want my flywheel to do is smooth out running at low speeds, but what it is designed to do is smooth out running at medium and high speeds.  It's effect is minimal at the speeds I do most of my operating at.  Hence my view is that the presence of a flywheel does no harm, but does not improve things much either.  As it happens, I only have two Hornby locos, not because I have any complaint about them but because another firm happens to produce more of the small GW tank locos I need for a layout set in a South Wales mining valley in the 50s.  They are a 42xx, which performs very well indeed and sort of plods like a real 42xx, and a worked up 2721 pannier.  The 42xx is the current production, not the 'design clever' version, and has a flywheel and a can motor of indeterminate poleage but it runs very smoothly.  It took a fairly long time of running in to achieve this smoothness, particularly in starting and stopping, but is a very well behaved beast now,  

 

The 2721 was second hand and needed a lot of TLC to get it to perform acceptably.  It is the current Railroad chassis driven on the front wheel which Hornby use as the generic chassis for a number of models.  It runs, eventually, very freely and quietly, but requires sensitive handling to prevent the loco taking off like a stabbed rat and I am considering replacing the 3-pole open frame motor and gears with a 5-pole and integral gearbox I found in the bottom of the bits and pieces box.  I had completely forgotten it, and it has what I think was called 'dynadrive', a flexible drive to a gearbox fixed to the driving axle with a plastic casing.  It runs; I hooked it up yesterday evening and lubed it; nowt wrong with it!  I have no idea what make the motor is.  It doesn't have a flywheel and will not have one in future.

 

The 42xx is thus the only loco with a flywheel, and I can't honestly say that it makes any difference in running.  It is impressive when you take the body off the chassis, and gives an impression of a very well designed and engineered mechanism, which I think is an accurate one, but while the brass flywheel looks good, it is not a game changer or even much of a player!

 

Flywheels on model railway locos could be of use IMHO if they were not fitted to the motor shaft where their effect is at it's least.  Were the coupled to the shaft or an axle via reduction gearing (thing pushalong toy friction drive), they might be more use, but of course they will of most use in the very locos that don't have room for them inside, small tank locos and pugs.  What I think is needed is a DC version of a stayalive.

 

The rest of the stud work well enough without flywheels, including an ancient Airfix large prairie with a very 'traditional' RTR type of mechanism.  Smooth running is a combination of good design, a regular mechanism cleaning regime, careful tracklaying direct to level baseboards with no underlay, total elimination of plastic wheels, parsimonious lubrication applied with a hypodermic syringe and needle, careful track laying, a first class Gaugemaster power controllier which is 40 years old but better than any more modern DC controller I've come across (but then I've no experience of Morley) and (controversially but it works for me) graphite on the rails.  Flywheels look good, increase the ballast weight, but make no difference otherwise.  

 

Things have improved over the last 40 years, but I am still of the opinion that RTR models could be geared better for slow running.  I was and still am in a theoretical sense a fan of split chassis mechanisms and dead central stub axles.  A mech of this sort can theoretically deliver very smooth running, the only mechanical friction being in the gear train, no pickups to act as drag on the wheels or get dirty.  Sadly, Mainline got it hopelessly wrong with a pancake motor that had to run at very high revs to develop any power that then needed reduction gearing to be controlled, and extreme slow running was difficult though smooth starts and stops could be achieved.  On top of that are the well known stub axle and quartering issues.  There are still RTR 'split' chassis about, but they often have conventional pickups.  Modern phosphor bronze pickup strips do not act as brakes in the same way that older brass or copper wire pickups did, and RTR performance is acceptable, but I think there is still room for improvement.  

 

I believe the ultimate RTR mechanisms, not in my lifetime perhaps, will be low geared axle hung motors driving direct to each axle powered by rechargeable power supply aboard the loco, controlled by NFC from smartphones, along with a form of 3-point compensation in a split chassis frame with split axles.  Very little mechanical friction, good haulage from wheels compensated to the track.  Dream on, Johnster!

[chris251]

Ever since I discovered flywheels, I've always thought they made a wonderful difference to running.

I'm not able to afford some of these brand new RTR items for sale now, so I've always been looking for ways to improve my existing locos.

However, I'm inclined to agree about the importance of a good motor and suitable gearing:

 

All my attempts to the Hornby railroad 0-6-0 chassis never worked very well.  I tried simply modifying the motor to double-ended shaft and adding a flywheel, this improved things, but wouldn't start smoothly or run very slow.  I tried replacing the motor with a 5 pole Tenshodo 19mm motor, but again, not very good without a flywheel, and a bit jerky with flywheel, but crawls better.

 

Older-tooled Bachmann class 158s run very well at a decent speed, but cannot crawl very slow - they are fitted with a centrally mounted large 5 pole strait wound motor with 2 flywheels, gearing is single-stage 1:7 gearing, gears are coarse, the pickups are quite high friction and the trailing coach has plain bearings not pinpoints.  The motor is good at slow speed, but I think the gearing should be at least 1:14, and the split axles could have brass bearings instead of wiper pickups.  Their new 158 seems to use pinpoint bearings, and split axle pickup.

 

I motorised a Dapol railbus kit, and with 1:50 gearing, and a motor with flywheel, it is quite loud, but crawls beautifully, and rolls about 12 inch or more when the power is cut from a scale speed of about 50mph.

 

I've also been modelling 009 and found that a flywheel is often hard to fit in, but again the important thing is free but not rattly gearing, good pickups, and a good motor (often the only motors that fit are tiny 3 pole motors, some of these are very good and run very slow).

 

Generally, flywheels work much better at higher speeds.  If you're building the mechanism, by doubling the gearing, the motor has to run twice as fast to achieve the same same speed, so the flywheel will have 4 times the stored energy (stored energy is proportional to the square of the speed, 2 x speed = 4 x energy, 3 x speed = 9 times energy).

 

A tiny flywheel which just smooths the engine across dodgy pointwork seems to crawl much better than an enormous flywheel which keeps the engine rolling when the power is cut.

 

Also, don't assume a 5-pole skew wound motor will be the best - some cheap ones are worse than 3 poles and won't run slow at all.

 

As for an analogue keep-alive, I've tried without much success - it needs so many electronic components to make it work well (including a tiny computer chip) and the capacitors need to be about 0.5 Farad at 10V to have an effect on a newer motor, they'll do almost nothing for an X04.

My opinion is to fit in a small flywheel if possible but also make sure everything else runs smooth and free.

[No Decorum]

I suppose 3-pole and 5-pole motors are like Stephenson’s and Walschaerts’ valve gears on the real things. The type is not as important as how each is executed. Hornby’s use of flywheels on Railroad motors didn’t work because the motors were so inconsistent. Some people were lucky with their P2s, others unlucky. A lot of models run very well without flywheels although I do like them. If they do have a drawback, it’s their inertia. Heavy handedness on a controller will cause them to jerk into action but, with care, I agree that they are an aid to good running.