Scalefour Forum

Hello, I'm looking for somewhere to buy Flywheels.

I have a couple that I brought from (I think) Mainly Trains a while back but they don't currently have any. They are 1.5mm diameter shaft holes but I need one with a 2mm hole. Preferably not too big.

Looking on the 'net I saw some from http://www.roxeymouldings.co.uk/category/46/flywheels/ and one of them might be ok, but the 12mm x 10mm might be a wee big. Looking for something smaller if possible.

Alternatively is it possible to make them? is it literally a brass chunk or is it partially hollowed out inside to provide some type of momentul throw? I don't know but I am thinking of bodging some out of some spare bolt heads if they would do the trick - maybe the idea is silly.

Yes you can make them, it's important that they are balanced and concentric.

As for hollowing out the middle, it has to do with the inertial forces. The more mass you can have further from the axis the better. So a large diameter, with a thick ring around the edge and just enough to hold it together in the middle is best. However, as this has to fit in a scale model, there's not a huge benefit to doing this. The inertia increases with the square of the radius.

Knuckles wrote:Hello, I'm looking for somewhere to buy Flywheels.

I have a couple that I brought from (I think) Mainly Trains a while back but they don't currently have any. They are 1.5mm diameter shaft holes but I need one with a 2mm hole. Preferably not too big.

Hi Knuckles,

You could try Branchlines. I'm not sure whether their current catalogue is online.

However the attached file is a copy from a couple of years ago. It lists a variety of flywheels on page 3, including some with 2mm bores.



HTH
Flymo

Flymo beat me to it.

At Aylesbury the Branchlines bloke was giving someone quite a bit of help working out a motor/g'box and flywheel combination for a custom made chassis. They don't publish a list on the website, but the bloke who runs it is such a helpful chap- if anyone can help you, it'll be him.

If not, high level kits might.

Hope that's of some use.

If you get a Branchlines flywheel, it'll likely be a slip fit on the motor shaft. You'll need some Loctite 603 or similar to fix it.

To make a flywheel, you need a lathe; as Gareth has said, balance and concentricity are all. It really isn't possible any other way. Once you have your flywheel, from whatever source, do make sure that the motor doesn't vibrate as it revolves. If it does, it means the flywheel is out of balance and in this state will eventually do all sorts of nasties to the motor bearings. In this situation it is possible (although thankfully I've never had to try it) to true the flywheel by hand in situ - Chris Pendlenton has described this process in MRJ.

I might also add that I think the flywheel only has a function in our small models as a means of keeping the motor turning when there is a fractional interruption in the current flow. Unless the flywheel is very heavy and very big (as with a Dyna Drive set up) there will be little momentum, particularly with the low revving motors we use.

Philip

Philip Hall wrote:To make a flywheel, you need a lathe;

Yes you do, and if using a three jaw chuck to hold the work, it may not be very true. (see Scalefour News No 155 page 17 for an explanation if needed) The best way is to hold the bar in the chuck and take a skim over the outside until it is running true, then make the hole and any recess needed.

If you have a flywheel with a 1.5mm did. hole then if it is held vertically in the vice of a drilling machine you might be able to open out the hole to 2mm since the drill bit should follow the existing hole. How accurate that would be is another matter. Probably easier just to but a new one with the correct size hole.

Terry Bendall

The effect of a flywheel is proportional to the square of the motors speed.Therefore a flywheel is much less much less effective at slow speed when most people want the perceived improvement it offers.

Clean wheels and track, efficient pickups and compensation/springing so that all wheels are in contact with the rails are the primary requirements.

However, if you still feel the need, try Markits;

http://www.markits.com/

Jol

Jol Wilkinson wrote:The effect of a flywheel is proportional to the square of the motors speed.Therefore a flywheel is much less effective at slow speed when most people want the perceived improvement it offers.

But since that is motor speed, not vehicle speed - and since you will naturally have chosen (won't you?) a gearbox arrangement which allows the motor to run at or around its optimum revs most of the time, despite your loco progressing at whatever snail's/slug's/hedgehog's pace you prefer, it is still perfectly possible to benefit from a flywheel's smoothing of starting, stopping and turnout negotiation, without having to hurtle around like a startled donkey*. The only real problem is finding room to fit a blooming girt brass blob somewhere in your drive gubbins (particularly if your loco stud is mainly open cab models).

*And that's surprisingly rapid - I know, we had one in the garden a few weeks ago!

Wizard models also sell some

HTH

Jim

Many many thanks to all of you. Very helpful ye are and I'm highly greatful.

The motor I'm using is I think a 1220 Mashima. Quite small but high reving. The choice is purely on space restriction. I could use a bigger one but I'm trying to keep the Firebox and Boiler destruction to a minimum!

dal-t wrote:

Jol Wilkinson wrote:The effect of a flywheel is proportional to the square of the motors speed.Therefore a flywheel is much less effective at slow speed when most people want the perceived improvement it offers.

But since that is motor speed, not vehicle speed - and since you will naturally have chosen (won't you?) a gearbox arrangement which allows the motor to run at or around its optimum revs most of the time, despite your loco progressing at whatever snail's/slug's/hedgehog's pace you prefer, it is still perfectly possible to benefit from a flywheel's smoothing of starting, stopping and turnout negotiation,

Not sure I agree. As Jol was pointing out the effectiveness of the flywheel is very limited when the motor is turning slowly. if you build your loco's to run no faster than scale speed, it's more than likely you want them to start and stop smoothly as well and the motor will still be turning slowly a start and stop time.

Lets look at an example. Say you had a loco with 5ft wheels, that's 20 mm diameter and roughly 63mm circumference, fitted with a motor that does 14000 rpm and a 60:1 gearbox. It will have a top scale speed of about 43 mph, so not that startled a donkey. To appear to be stopping or starting like something made of many tons of metal, I have found its necessary to be able run the loco reliably at at speeds down to about an inch, or for the sake of simple sums lest say 30mm, a minute. So I'm looking for a chassis that must run reliably with the motor turning at at 1/2 a revolution a second. (30 mm is half a wheel revolution and as the motor is turning 60 times faster then the wheels that's 1/2 a rev a second) I think a flywheel would be largely irrelevant as b****r all squared is still b****r all. In lots of pick-ups, clean wheels and track, and electronic controllers that monitor how fast the motor is turning we trust.

if you build your loco's to run no faster than scale speed, it's more than likely you want them to start and stop smoothly as well and the motor will still be turning slowly a start and stop time.

If you have a high rever and a reducing gearbox, then the engine will be moving at ,say 10MPH but your motor at 30, with a flywheel on it'd be more effective than a low rever at slow speeds without a ratio reducing gearbox....wouldn't it?

This is a question as I'm not sure, I just expounded my logic. If I'm talking Ox Poo please tell me.

Not Ox Poo, Knuckles, you've grasped exactly the point I was making. I've never met Will's motor revolving at 1/2 a turn per second, and at first sight I thought he was simply floating another bumble-bees can't fly argument (because those of us that have used flywheels for years know just how much they do contribute to extra smoothness), but I've seen through his ruse now. His next post will be explaining how all these problems will go away if only you use his beloved CSBs, despite the complications of the dratted beasts - arriving at a platform near you very shortly!

The original finding was that bumble bees can't glide. Which they can't.

dal-t wrote:Not Ox Poo, Knuckles, you've grasped exactly the point I was making. I've never met Will's motor revolving at 1/2 a turn per second, and at first sight I thought he was simply floating another bumble-bees can't fly argument (because those of us that have used flywheels for years know just how much they do contribute to extra smoothness), but I've seen through his ruse now. His next post will be explaining how all these problems will go away if only you use his beloved CSBs, despite the complications of the dratted beasts - arriving at a platform near you very shortly!

Trucks for sidings I guess!
I do like flywheels, without a doubt every engine I have them in run better without question.

jim s-w wrote:The original finding was that bumble bees can't glide. Which they can't.

Maybe once they have travelled forward a bit they can fall at an angle...
Must be honest I have no idea what the Bumble Bee references are about but it provides interesting reading.

There is a school of thought that some subscribe to which says that a flywheel will help to smooth out a less than perfect mechanism or motor. I believe that a flywheel does help, but only in a near perfect job to start with. If the thing is vibrating all over the place, or isn't a smooth runner before you start, hanging a (concentric) large lump of brass on the motor shaft won't really help.

When the mechanism is good it does make a difference, but I put one in if there is room, and don't worry if there isn't. A very good example of what works is the new Hornby S15, which has two flywheels, of quite a decent size, either end of a five pole skew wound motor and coupled to a double reduction drivetrain. It runs exquisitely, possibly the best RTR mechanism I have ever come across, and easily equal to some of the best home brewed chassis. My challenge to myself is not to b....r any of this up when I start taking it apart.

Philip

Fair enough and good advice. Sounds the same as a DCC conversion, in that a DCC chip can help an ok runner become a good one and a good one a great one, but it won't make a naff one good. So I hear anyway.

My Heljan Hymek has 2 flywheels and is the best runner I've ever ever ever had, both before and after my Ultrascale conversion. There is a certain coolness about listening to it and 'feeling' it on the control that's really pleasurable. Hard to explain. It's strange, different engines 'feel' different when running them, even though you don't feel them at all.

I'm also interested in 'electronic flywheels' as they have become nick-named. The DCC Capacitors.

I imagine having a physical and electronic flywheel installed will make your engine almost bomb proof, something I definetly want to do when I finally go DCC.

I did look into using capacitors for normal DC but was never sure what to get. Opinions wer3 everywhere and nothing solid.

Ultrascale also have a few flywheels on their website, shouldn't think they are on the normal 6 month lead time like the wheels.

Thanks for the heads up. I just looked at their flywheels and they have the option of solid or recessed. What is the difference? This brings me to one of my earlier questions where I'm guessing it might have a different effect on the throw due to the weight majority being on the outside thus maybe being more effective...but then a solid one has more mass sooooo.......ugh.

What would ye say on this?

The reasons for hollowing out a flywheel are firstly to save weight and secondly if you want to fit something into the recess. Some motors have a bush that sticks out from one end, and you can save a a couple of millimetres in length by enclosing that bush in the recess. From your earlier post, this sounds like it might be important to you. The weight saving is irrelevant in 4mm scale.

As you guessed, most of the angular momentum in a flywheel is carried near the rim, so hollowing out the centre doesn't make it ineffective.

Areeyt cool.

Thankyou muchly.

I'll survey these sites soon and find something.

I think it's great how on our S4 forum a wee question ends up a mine of useful information and helpful conversation to anyone reading. This is truly a great thing we have going on here.

Looking back through this topic, there are a number of recommendations offered but I am struck by the fact that Knuckles didn't actually tell us is the application for which this flywheel is needed. What model, wheel size, motor, gear ratio and operating speeds?

The opening post says he has 1.5mm shaft flywheels but needs 2.0mm ones. Later on (did we all miss it?) he refers to using a Mashima 1220, which unless I am in a parallel universe, has 1.5mm diameter shafts.

I remain of the view that a well built, efficient "chassis" doesn't benefit noticeably from fitting a flywheel. However until someone conducts some proper scientific tests, it'll remain the subject of conjecture (where's CLAG when you need them?)

Knuckles post of 16 November refers to electronic flywheels. I believe these are usually referred to as "stay alive" devices for DCC and are fitted to the 12v supply side of the chip so maintaining a reservoir of 12v power in the event of a power cut through the pickups. The same thing isn't available as far as I know for DC as it would need to monitor the supply voltage and feed the motor at that voltage until power is restored. That is effectively what the rotational inertia of the motor armature and flywheel (if fitted) is doing. However the dynamic power contained within the rotating components is fairly small and unlikely to have much impact.

Knuckles refers to his Heljan Hymek, fitted with to flywheels as being his best runner. It probably also benefits from a relatively large motor and fairly low gearing with smaller frictional losses. Philip Hall post of the same date tends to confirm the benefits of large flywheels as fitted to the Hornby S15, but is that partly due to Hornby understanding the kind of operating conditions under which their models are designed, built and run and trying to fix them at source?

Jol

There are a few other interesting threads on the subject of flywheels and stay-alive capacitors, notably:

viewtopic.php?f=32&t=4448

viewtopic.php?f=19&t=2625

The consensus of the latter appears to be that using DCC, stay-alive capacitors are better than flywheels at overcoming short term pickup problems.

regards

Looking back through this topic, there are a number of recommendations offered but I am struck by the fact that Knuckles didn't actually tell us is the application for which this flywheel is needed. What model, wheel size, motor, gear ratio and operating speeds?

The opening post says he has 1.5mm shaft flywheels but needs 2.0mm ones. Later on (did we all miss it?) he refers to using a Mashima 1220, which unless I am in a parallel universe, has 1.5mm diameter shafts.

Whoopsie, that's correct on the shafts. I made a mistake and said the reverse of what I meant. My bad.

As for the component choice and needs it's mainly a case of what will fit without cutting too much of the boiler up.

As for the engine type......my lips are sealed until it's done, sorry.