Flywheel Size

[Traintresta]

Is there a recommended size of flywheel proportionate to the size of the motor it’s attached to?

 

I’m playing about with motors that are smaller than usually provided in our models. Attached is a photo of three motor/flywheel combinations that I want to try in some athearn switchers to see how they perform. I intend to add more weight and will only be switching a few freight cars at a time so I’m not pulling large loads, but the currently uninstalled set-up has flywheels larger than the motor dimensions and I’m wondering if this will be a problem?

[Il Grifone]

I would say the bottom ones are too large, but the other two should be OK. Too much weight will overload the motor bearings and require an excessive starting current. Make sure the universal-joints are well lubricated. I use Kadee Greas-em.

 

That X2f needs to go! 

Edited June 23, 2021 by Il Grifone

[Traintresta]

1 hour ago, Il Grifone said:

I would say the bottom ones are too large, but the other two should be OK. Too much weight will overload the motor bearings and require an excessive starting current. Make sure the universal-joints are well lubricated. I use Kadee Greas-em.

 

That X2f needs to go! 

X2f??

[Il Grifone]

Aka Horn-hook coupler. Most (myself included) prefer Kadees, especially for switching. Here's one who doesn't!

https://tracksidetreasure.blogspot.com/2014/03/the-x2f-files.html

 

They do work (but won't uncouple if you cut the pin off as recommended here). The secret is not to have a strong return spring, which tends to push things sideways and leads to derailments. Unfortunately most designs have a beefy chunk of plastic as a spring! I still have a few on cars kept in block trains but their days are numbered.

 

I've seen them compared to a Parasaurolophus. Something to do with horns and prehistory I assume.

[JeremyC]

3 hours ago, Il Grifone said:

I would say the bottom ones are too large, but the other two should be OK. Too much weight will overload the motor bearings and require an excessive starting current. Make sure the universal-joints are well lubricated. I use Kadee Greas-em.

 

That X2f needs to go! 

I would suggest the biggest problem with the bottom motor in the picture is that the flywheels are drilled for locking screws. Because of this the flywheel will most likely be out of balance, which is more likely to cause bearing problems than the weight of the flywheels.

I have always had two objections to flywheels on models: 1) They're often too small to have much effect and 2) Even without locking screws they need to be accurately made and well fitted to have any chance of being in balance.

[Traintresta]

19 minutes ago, Il Grifone said:

Aka Horn-hook coupler. Most (myself included) prefer Kadees, especially for switching. Here's one who doesn't!

https://tracksidetreasure.blogspot.com/2014/03/the-x2f-files.html

 

They do work (but won't uncouple if you cut the pin off as recommended here). The secret is not to have a strong return spring, which tends to push things sideways and leads to derailments. Unfortunately most designs have a beefy chunk of plastic as a spring! I still have a few on cars kept in block trains but their days are numbered.

 

I've seen them compared to a Parasaurolophus. Something to do with horns and prehistory I assume.

They just haven’t been removed from

when it arrived from eBay the other da. 

[Traintresta]

17 minutes ago, JeremyC said:

I would suggest the biggest problem with the bottom motor in the picture is that the flywheels are drilled for locking screws. Because of this the flywheel will most likely be out of balance, which is more likely to cause bearing problems than the weight of the flywheels.

I have always had two objections to flywheels on models: 1) They're often too small to have much effect and 2) Even without locking screws they need to be accurately made and well fitted to have any chance of being in balance.

Is there anything that can be done to fix this or an alternative?

[SamThomas]

16 minutes ago, Traintresta said:

Is there anything that can be done to fix this or an alternative?

All those manufactures who fit flywheels cannot be wrong can they ?

 

If the flywhee(s)/motor combination is out of ballance to will hear &/or feel it - no point in looking for a problem that may not exist.

[kevinlms]

2 hours ago, JeremyC said:

I would suggest the biggest problem with the bottom motor in the picture is that the flywheels are drilled for locking screws. Because of this the flywheel will most likely be out of balance, which is more likely to cause bearing problems than the weight of the flywheels.

I have always had two objections to flywheels on models: 1) They're often too small to have much effect and 2) Even without locking screws they need to be accurately made and well fitted to have any chance of being in balance.

You could easily fix any balance problem by taking the flywheel off and drilling right through, then reassembling.

The key part is making it equal, i.e. opposing any imbalance, which drilling through will do.

 

The largest diameter practical is the best solution, because it comes down to R squared.

 

[Mark]

On 23/06/2021 at 15:47, kevinlms said:

You could easily fix any balance problem by taking the flywheel off and drilling right through, then reassembling.

The key part is making it equal, i.e. opposing any imbalance, which drilling through will do.

 

The largest diameter practical is the best solution, because it comes down to R squared.

 

The out of balance force is mw^2r. m is the out of balance mass, w is the rotational speed in radians per second and r is the radius. If you use gramms for the mass then r can be used in mm. Take rpm and multiply by pi/30 to get radians per second for w.

 

Mark

[Traintresta]

This is all getting very technical. 

[Barclay]

I'm a fan of flywheels myself - this large one on one of my loco's gives significant over-run and a very silky feel to the driving experience. 

 

 

 

And of course US diesels are and always have been just about the best running RTR loco's available, and they all have flywheels. If I were you I would experiment with the giant flywheel option, just to see what happens. Grub screw fitting is less than ideal as others have said, but try holding the motor and running it up to full speed - you will soon feel the vibration if there is any. It could possibly be cured in part by removing the grub screws, filling the holes with brass rod and using Loctite to secure them instead. However check if it's an issue first. Perhaps move one round slightly so the holes are opposite each other?

 

That motor in the back one - is that one of those Chinese 5 pole skew wound ones that you can get off ebay for next to nothing? I have recently bought a couple like that but haven't tried them yet.

Edited April 7, 2022 by Barclay

[Traintresta]

7 hours ago, Barclay said:

That motor in the back one - is that one of those Chinese 5 pole skew wound ones that you can get off ebay for next to nothing? I have recently bought a couple like that but haven't tried them yet.

It is indeed. It seems to run very smoothly and quietly on test under no load or with flywheels attached but haven’t yet had chance to test it in the full drive.

 

My original intention was to use it like the mashima 1015 sized motors but I want to do some comparisons before I make any decisions. That said, I’ve got ideas about building motor bogies with them if they are any good. 

[Traintresta]

On the back of some of the comments here, I’ve re-read some of the conversations I’ve had in other threads and I’m left wondering if i even need a flywheel now. 

[kevinlms]

2 hours ago, Traintresta said:

On the back of some of the comments here, I’ve re-read some of the conversations I’ve had in other threads and I’m left wondering if i even need a flywheel now. 

I wouldn't dismiss it out of hand. Barclay has given a working example, you could try the same and if you don't like it, remove it.

[Traintresta]

13 hours ago, kevinlms said:

I wouldn't dismiss it out of hand. Barclay has given a working example, you could try the same and if you don't like it, remove it.

Quite; I'm stuck between large flywheels and no flywheels...

[Traintresta]

On 25/06/2021 at 15:44, Barclay said:That motor in the back one - is that one of those Chinese 5 pole skew wound ones that you can get off ebay for next to nothing? I have recently bought a couple like that but haven't tried them yet.

Initial test wasn’t very promising: seemed to start and stop relatively smoothly on the first few runs up and down a test track. It accelerated a bit quickly and went better in one direction but that could be for many reasons. 
 

But then it stalled…

Got my crocodile clips tangled for about 10 seconds causing a short and after that it ran very poorly by all measures and I touched it immediately after the short and recoiled in horror as I burned my fingers. At least the extreme heat might account for the strange smell??

 

I gave up for the night after that. More tomorrow. 

[melmerby]

On 23/06/2021 at 13:30, JeremyC said:

I would suggest the biggest problem with the bottom motor in the picture is that the flywheels are drilled for locking screws.

Might have two screws opposite each other, which would aid the balance.

[Traintresta]

The Chinese motor is unsuitable. It heats up to extremely high temperatures very quickly. The Bachmann motor doesn’t have enough power to move the athearn drivetrain at more than a snails pace. 
 

However, with a bit of grinding away at the chassis, the set-up in the image works very well. This is one of those 24v motors from China that resembles what Hornby and Kato use. With it sufficiently low enough in the chassis, there’s now enough room for weight, a speaker and decoder plus the improved running characteristics.