Jump to content

N20 motors - Railway Modeller April 2018


Robin2
 Share

Recommended Posts

I'm rather confused. The final drive shaft is of different diameters each side of the gear box. Am I correct in thinking that you have already removed this final drive shaft and replaced it, or that as you allude to in your last posting, this is your intention and that you are concerned about attempting to remove the D shaft? 

Link to post
Share on other sites

  • RMweb Gold
Posted (edited)

Hello, the output  'D' shaft has a diameter of 3mm. the Markits-Romford axle is 3.18mm, or, 1/8". One of the 'box walls was slightly undersize, and the other was oversize. To overcome this disparity, I used a Romford axle bush onto the axle, which was an interference fit between the  axle, bush, and final gear. On the other wall, the oversize axle hole was remedied by soldering in the Romford axle bush. Both walls had another visit from the reamer, to keep them pretty much aligned.  Remember though, that the length of the bush is longer than the thickness of the 'box wall, by about 2mm. I filed off the excess to keep the overall width to 10mm. Judicious use of 1/8" washers will be needed to pack out the sideways thrust, or the final gear will lose mesh. 

  

 

Thank you for your post. I've had another look at the extracted 'D' shaft, and it should allow the shaft to be driven out from the smaller diameter, with the 'D' portion leading. 

 

Cheers,

Ian.

 

PS. Yes! Sorry! The photo shows the N20 gearbox, with a Markits-Romford  1/8" axle installed. 

Edited by tomparryharry
Link to post
Share on other sites

  • RMweb Gold
10 minutes ago, Michael Edge said:

Why not use Markits 3mm axles?

 Well, I used what I had, and it's a happy coincidence that 3mm and 1/8" allowed a little bit of an interference fit.  I've been using 1/8" axles & bushes since I can't remember when, so it's a bit of a 'go to' situation. 3mm in a 1/8" hole is a sloppy fit, whereas right now, it's pretty good.  (at least for me ).

Link to post
Share on other sites

  • 1 month later...
  • RMweb Gold

The N20 motors are now being sold as a 'dual shaft' version. These retain the same 10mm width  across the gearbox wall sides. From a 00 perspective, they will still need to be taken apart to fit a suitable axle, but it's pretty good so far.

 

Michael Edge of this parish has suggested the Markits 3mm axle might be a suitable improvement. I haven't gone down that road yet, but I've ordered some of those motors today.  

 

Let's see!

 

Ian.

  • Like 3
  • Informative/Useful 2
Link to post
Share on other sites

  • 2 months later...

To add a little more to this thread, here is one of the type that tomparryharry introduced us to on the previous page fitted and in use in a scratchbuilt frame for a Hudswell Clarke diesel.

hcframes-001.jpg.b6257483e8c3f30036777cb72bd9ef40.jpg

 

HCfin-013.jpg.93899f89f289bda6a64fec676637deb6.jpg

 

One of the type that has the drive shaft under the motor fitted to scratchbuilt frames for a Drewry, driving through 0.4 module spur gears.

image.png.44acd580b69eb1415cb62c849520d5b6.png

 

image.png.6add4984331e34f98bb2e14db73e86e4.png

 

The in line type, fitted to a Craftsman etched brass Class 02 chassis and driving through nylon bevel gears.

image.png.f6c83593ada7a54137c79872a2ef2e6c.png

 

 

 

Edited by Ruston
  • Like 5
Link to post
Share on other sites

Have you seen any failures on the bevel-drive arrangement?   I have a set I was either going to wedge into a Y8 or Johnson 3F.

Edited by AlfaZagato
Punctuation
Link to post
Share on other sites

I have a dozen or so vehicles with plastic bevel gears (0.5 Mod) - non of which have given the slightest problem, also a few locos with smaller bevel gears (brass, loctited on, some epoxied) also with no problems.

My locos use much smaller gearmotors (less powerful) and still perform very well. The vehicles use N20s and need to work hard.

  • Like 3
Link to post
Share on other sites

image.png.c77598124c2db3e4e2dd69235e10f173.png

image.png.8ba84c761796f4114cee452e7ab266d6.png

 

This is a N20 with the output shaft shorter to fit between the axles of a 8`9" emu bogie. I have also done the same using a replica commonwealth bogie. It looks possible to get it in a 8`6" bogie with 12mm wheels.

  • Informative/Useful 1
Link to post
Share on other sites

2 hours ago, Michael Edge said:

Does this run fast enough? I've got some of these contrate gears but they aren't 1:1.

 

This one was timed at 70 mph at top speed using 12.3mm wheels and towing two replica coaches plus a black cat speed wagon. This was using the 1000rpm version. The biggest problem was traction with only one axle powered.

Link to post
Share on other sites

On 17/07/2021 at 14:34, Ruston said:

To add a little more to this thread, here is one of the type that tomparryharry introduced us to on the previous page fitted and in use in a scratchbuilt frame for a Hudswell Clarke diesel.

hcframes-001.jpg.b6257483e8c3f30036777cb72bd9ef40.jpg

 

HCfin-013.jpg.93899f89f289bda6a64fec676637deb6.jpg

 

One of the type that has the drive shaft under the motor fitted to scratchbuilt frames for a Drewry, driving through 0.4 module spur gears.

image.png.44acd580b69eb1415cb62c849520d5b6.png

 

image.png.6add4984331e34f98bb2e14db73e86e4.png

 

The in line type, fitted to a Craftsman etched brass Class 02 chassis and driving through nylon bevel gears.

image.png.f6c83593ada7a54137c79872a2ef2e6c.png

 

 

 

May I ask from where are you sourcing your final drive gears? thanks.

Link to post
Share on other sites

  • 3 weeks later...
On 16/01/2020 at 06:06, Giles said:

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

 

Not really, the only bad thing here is that particular implementation of worm drive. First the diameter of the worm. The worm rubs with a surface speed proportional to 3 times the diameter against the gear teeth, and with those fat worm teeth you risk contact on both sides of the gear tooth (which is not cut for worm drive to boot!) unless you keep it sloppy. And i don't remember those worms having a nice polished surface. Anybody remembering "running in" loco drives? In the hope the gear might polish the worm? Anyway, with the motor shaft the fastest piece in the drive train, this worm maximizes friction.

You need to keep worms as thin as possible and as slippery as possible, with matching, mating gears .

I'm confident you can connect any quality worm drive at any ratio to this n20 successfully.  Should there ever be a need.

 

Sorry,-w

  • Informative/Useful 3
Link to post
Share on other sites

Well, I absolutely agree  (and I genuinely think it's great that you've taken the time to point this out) - this worm and gear (which were sold as Romfords matching set) are highly inefficient - right at the bottom end of the efficiency chart for worm and gears (for all the reasons you've rightly pointed out). A well engineered worm and gear can be very much more efficient - but still not as efficient as other forms of gearing. Escap for instance chose to use bevel gears as their primary drive between motor and Portescap gearbox - partly for space, but certainly for efficiency.

In Practice I find it much more satisfactory to use bevel gears to extract maximum efficiency, particularly when using smaller, less powerful motors than the N20s, where any shortfall shows more readily. My projects in recent years haven't seemingly needed running in, in consequence.

 

(P.s. I needed the 5:1 × 20:1 ratio on this, and couldn't find many options! MKll was a K20 bevel gear solution)

 

Best

 

Giles

  • Like 1
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
 Share

×
×
  • Create New...