Jump to content
Robin2

N20 motors - Railway Modeller April 2018

Recommended Posts

3 hours ago, ianLMS said:

Quick question (and probably a very silly one) but when using the bevel gears with this set up, I assume you put one on the motor drive axle shaft and the same size bevel gear on the wheel axle. As there is no grub screw, do you just superglue it to the axle?

 

I've done mine as a really tight friction fit, so far no problems but the models don't have to work hard.

Share this post


Link to post
Share on other sites
 

Andy

You must be very strong. My Triang units won't back drive with their original gearing.

 

Baz

Share this post


Link to post
Share on other sites
40 minutes ago, Barry O said:

Andy

You must be very strong. My Triang units won't back drive with their original gearing.

 

Baz

 

Hi Baz,

 

It works on mine because I replaced the original brass worm wheels on the axles with nylon gears. That reduces friction a lot. It probably helps that the motor's magnet is pretty feeble too.

 

IIRC I can also back-drive the motor on my Caley Single.

 

Cheers,

Andy

Share this post


Link to post
Share on other sites

  

15 hours ago, tomparryharry said:

Hello Folks. As usual, I'm late to the party...

 

I have some questions about these little N20 motors. They look exquisite, and the gearbox faceplate looks as though it's capable of mounting either a Romford/Markits gear arrangement, or High Level. If that is the case, what size of  screw thread are we looking for?  M1.4, etc?   I'm currently working with a standard 12v DC arrangement. 

 

All information will of course, be gratefully received.

 

 

11 hours ago, Michael Edge said:

I should add that putting a worm drive on the end of this superb little spur gearbox negates the whole point of using it - it works well because it doesn't have an inefficient worm drive.

 

11 hours ago, tomparryharry said:

 

Thanks Michael. I haven't gone down the route of bevel gears, I'm wondering how you'd mount the motor. I can certainly see some applications, however.

 

 

9 hours ago, tomparryharry said:

Thanks for all of your input, folks. My original question is this:- What size of screw do I require to fit an N20 motor to a fold-up type gearbox, ala an High Level-type gearbox?

 

 

OK - I hope you don't mind me butting in here.

 

As Michael has pointed out, the widely available N20 based drive assemblies have already got a rather tidy gearbox fitted, with a "D" shaped output shaft - so you're just talking suitable bevel or crown gears to allow them to drive a suitable wheelset.

 

As for fixing the brass faceplate to a model chassis, I believe the ones I'm (planning on) experimenting with have 2 holes, tapped to M1.6. I believe these tapped holes are 4.5mm either side of the centre of the shaft (which I seem to recall being dead centre of the faceplate). I also seem to recall the faceplate being 12mm * 10mm, with the threaded holes being on a centre line, 1.5mm in from the ends of the faceplate.  However, all this stuff this should be able to be checked using either a caliper (digital or Vernier) or one of the drawings which sometimes appear on the internet.

 

(If nothing else, you could try googling "N20 motor gearbox drawings" - or something similar - and probably find I've got it all completely wrong ... .)

 

Anyway, I hope at least some of this stuff is of some help to someone.

 

 

Regards,

 

Huw.

  • Thanks 1

Share this post


Link to post
Share on other sites

Screw holes in the motor itself are M 1.4, when using the spur gearbox I usually just solder it to the frames if it's driving a fixed axle. The chain drive in the 7mm 05 was used because none of the axles are fixed - that's why I plan to drive on the gearbox (jackshaft) axle next time. 

  • Thanks 1

Share this post


Link to post
Share on other sites

N20/Gearbox and plastic bevel gears ordered off Ebay as linked in the previous posts to experiment with on my next kit (Proscale Webb Coal Tank & Alan Gibson Jinty)

  • Like 1

Share this post


Link to post
Share on other sites

I was experimenting with a Comet chassis for the Bachmann Jinty as can be seen by these photos

 

 

IMG_20191214_151244.jpg

IMG_20191214_151152.jpg

 

I need to buy the AGW wheels to continue the experiment.

 

Cheers

Edited by PenrithBeacon
  • Like 1

Share this post


Link to post
Share on other sites

Apart from the aspect of gear efficiency being a can of worms not worth opening, (so many caveats involved), the problem with bevel gears is the side thrust generated. In the long distant past I have used Faulhabers with integral gearheads mated to Slaters 3-1 crossed helical boxes. This gave a total reduction of 1-177.......but quite nice performance. Once the wheels started moving at any speed nothing much stopped them.....

 

It occurred to me that mating these N20 motor/gearboxes to these 3-1 boxes might be good... until I found that while they are still available, at £24 a throw perhaps not an economic idea today.....

 

Izzy

Share this post


Link to post
Share on other sites
9 hours ago, Huw Griffiths said:

  

 

 

 

 

OK - I hope you don't mind me butting in here.

 

As Michael has pointed out, the widely available N20 based drive assemblies have already got a rather tidy gearbox fitted, with a "D" shaped output shaft - so you're just talking suitable bevel or crown gears to allow them to drive a suitable wheelset.

 

As for fixing the brass faceplate to a model chassis, I believe the ones I'm (planning on) experimenting with have 2 holes, tapped to M1.6. I believe these tapped holes are 4.5mm either side of the centre of the shaft (which I seem to recall being dead centre of the faceplate). I also seem to recall the faceplate being 12mm * 10mm, with the threaded holes being on a centre line, 1.5mm in from the ends of the faceplate.  However, all this stuff this should be able to be checked using either a caliper (digital or Vernier) or one of the drawings which sometimes appear on the internet.

 

(If nothing else, you could try googling "N20 motor gearbox drawings" - or something similar - and probably find I've got it all completely wrong ... .)

 

Anyway, I hope at least some of this stuff is of some help to someone.

 

 

Regards,

 

Huw.

 

No problem Huw, butt away!

 

Ian.

Share this post


Link to post
Share on other sites
2 hours ago, Michael Edge said:

Screw holes in the motor itself are M 1.4, when using the spur gearbox I usually just solder it to the frames if it's driving a fixed axle. The chain drive in the 7mm 05 was used because none of the axles are fixed - that's why I plan to drive on the gearbox (jackshaft) axle next time. 

Thanks Michael.

Share this post


Link to post
Share on other sites

Hello Folks,

 

Thanks for all of your input, the information was just what I needed. These little N20 motors might do just right for something like a replacement Portescap motor & box, so we shall see. Like Ruston of this parish, I also have a Taff Vale 'S' class kit, so a small motor is a must.

 

Best wishes,

Ian.

 

 

  • Like 1

Share this post


Link to post
Share on other sites
18 hours ago, Izzy said:

Apart from the aspect of gear efficiency being a can of worms not worth opening, (so many caveats involved), the problem with bevel gears is the side thrust generated.

 

I saw what you did there ;)

 

But its not so difficult. All large ratio gearboxes whether they use worms, spur gears or anything else produce a lot of friction so they are all intrinsically inefficient. But if your motor has power to spare that's not really a problem. My only objection is when people condemn worm gears on the grounds that they are inefficient when they can be just as efficient as any other gear arrangement with the same reduction ratio.

Share this post


Link to post
Share on other sites

Andy rightly makes a good and important point. He says that worm gears 'can' be just as efficient as other gear arrangements.... They can be surprisingly efficient - some manufacturers quote just over 90% which is remarkable - however those are very good bits of kit, and worm efficiency varies dramatically. The ones I get to shove in my models certainly aren't anything like that good, sadly. Having said that, I'm in no way anti worm, having fitted and used countless of them on countless models.

In theatre, we use a variety of hoists for lifting and flying. The simpler ones are motor/worm/gear arrangements, and one of the very important safety features is that they do NOT feed back (some early manual hand winches did, and it would on occasion end up very nasty!) . The worm and gears are of course specifically specified and designed not to feed back for this application.

 

In the interests of collective experience, the reason I made comment about the poor efficiency of worms was one particularly 'dramatic' empirical example I had when building one chassis- which may be of interest as it concerns the N20s.

 

I build a chassis for a 7mm narrow gauge Bagnall (for radio control) with a white metal body- so relatively a heavy beast..... because I had used many N20s on vehicles and been do impressed with them, I thought I would use one on this as well - but because I needed to off-set it to hide it in the Firebox, I decided to use a 5:1 ratio N20 in conjunction with a 20:1 worm. This proved to be very weak and easy to stall, giving poor slow speed control and overall disappointing performance. I removed that installation, and replaced it with the very much smaller K20, driving through a modified 0.3M brass bevel gear.  This was superb, giving the same track speed but much 'stronger' at the wheels, and thereby giving much better, smoother control. 

 

Both installations delivered the same nominal RPM at the axle, both were properly meshed. Control etc. remained the same and un-altered.

 

The N20 was a 6v motor (12 x 10 x 20) and the K20 a 5v motor (8 x 6 x 16) with a planetary box..

 

My experience would suggest that N20s are most effectively utilised with a 1:1 final drive if possible, and avoid a high ratio final drive (like wot I tried..)

 

5:1 N20 with 20:1 worm and gear

35588079606_b700b0938c_b.jpg

03B65D83-16E9-46C2-88CB-7D1F63F78992_zpsgmmk0e2a by giles favell, on Flickr

 

K20 with bevel gears

40064717003_66232a6c9e_b.jpg

2019-02-08_07-14-46 by giles favell, on Flickr

Edited by Giles
  • Informative/Useful 3

Share this post


Link to post
Share on other sites
On 16/01/2020 at 06:06, Giles said:

 and avoid a high ratio final drive (like wot I tried..)

 

Hi Giles,

 

If I have it right the reduction between the N20 and the axle was 100:1. What's the reduction between the K20 and the axle?

 

Thanks,

Andy

Share this post


Link to post
Share on other sites
15 minutes ago, PenrithBeacon said:

The rpm of the motor is also important, not just the reduction ratio.

Cheers

 

The quoted RPM is usually the maximum RPM at maximum voltage under no load which is pretty much useless for our purposes. What we would like to know is the maximum torque produced versus applied voltage. In the last century Sagami (buy 'em if you can find 'em) provided graphs with their motors that described this relationship. Unfortunately no one else seems sufficiently troubled to do that now.

Share this post


Link to post
Share on other sites

The K20s were 151.1 1  according to their data, extrapolating the motor speed of 18,132rpm at 5v.

  • Thanks 2

Share this post


Link to post
Share on other sites
16 hours ago, Giles said:

The K20s were 151.1 1  according to their data, extrapolating the motor speed of 18,132rpm at 5v.

 

 

Thanks Giles.

 

This one from Hong Kong looks like the version you are using.

https://www.ebay.com/itm/Rare-earth-magnetic-K20-Motor-DC5V-Precision-8MM-Silent-Planetary-gear-motor-/323269524420

 

I have a theory about the problem you had with the N20 and worm set. Worms exert a lot of lateral force on their bearings and I suspect the rather short bearing supporting the worm's shaft is tending to bind under load. I'd like to see a bearing supporting the other end of the worm but it would not be very easy to do that.

 

Andy

 

 

 

 

Share this post


Link to post
Share on other sites

That is indeed the gear motor.... they were available at around £3.80, but sadly the supply appears to have dried up! If you do me across any actually stock, I suggest you buy them!

 

It's very possible it was behaving as you suggest - it was certainly very far from ideal, and I won't be repeating it!

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.