Jump to content
 

Chart Sutton SECR 1914-1923


Recommended Posts

On 21/04/2022 at 19:21, Sophia NSE said:

Wrong livery and some terrible weathering but some T-Cut and a couple of coats of paint have fixed that 

 

 

Weathering was so bad I thought it was on the outside of the plastic box. Good rescue job.

  • Like 3
Link to post
Share on other sites

Looks lovely in the SR green, shame to repaint it but kudos for sticking to the period modelling. Look forward to seeing the completed job.  I remember seeing one of these in the Tonbridge bay at Maidstone West, the L shaped brake handle sticks in my memory - must have been all of 3 y.o. at the time.

  • Like 6
Link to post
Share on other sites

  • 2 weeks later...
  • 2 weeks later...
  • 2 weeks later...
58 minutes ago, Sophia NSE said:

It's an N20 motor

I thought that is what it looked like. I didn't know you could get them so they drive the wheels directly. I use them but with a crown and pinion for the final drive. I must investigate 

  • Like 1
Link to post
Share on other sites

13 hours ago, whart57 said:

I thought that is what it looked like. I didn't know you could get them so they drive the wheels directly. I use them but with a crown and pinion for the final drive. I must investigate 

I am looking at using some of these to drive working model buses. The ones I have got will run on 1.5 volts, but have a 3mm drive shaft at the end which also has a flat on it. I have acquired some bevel gears which also have 3mm holes for the final drive to the bus axle. The only problem is that the final drive shaft is too long, I need to loose about 50% of it and they are made of bloody hard stuff. A saw will not touch it, so I am contemplating a cutting disc in a mini drill, doing a little at a time to avoid it getting hot and damaging the bearing.

All the best

Ray

  • Interesting/Thought-provoking 2
  • Friendly/supportive 1
Link to post
Share on other sites

20 minutes ago, wainwright1 said:

I am looking at using some of these to drive working model buses.

 

 

This is how I've done one.

 

20191020_201153-1.jpg.804e88e9270a96ba5a729b5f5c3a12cb.jpg

 

Admittedly I turned the wheels - with 2mm shaft - on the lathe and then fitted the tyres that were on the original plastic centres. The motor is a nominal 3v job and the power comes from a LIPO battery. It's radio controlled and that all works. It's the other end where I still need to get either a Faller front axle sorted for the wider 4mm scale track or fabricate one that has caused the hiatus in progress.

 

Shortening he drive shaft with a cutting disk works. Slow progress with pauses for cooling down is sensible though on the motors I've worked with the bearings have been brass so are proof to a bit of heat.

 

Sorry to all for the bit off topic here.

Edited by whart57
  • Like 3
  • Craftsmanship/clever 1
Link to post
Share on other sites

17 hours ago, Sophia NSE said:

It's an N20 motor

 

Or more specifically an N20 motor with double shaft. I've found some on Amazon now, but a question. They come in different speeds. I'm guessing the 95-381rpm would be the one for small wheeled locos with the 34-136rpm for large wheels. What do you think?

Link to post
Share on other sites

3 hours ago, whart57 said:

 

This is how I've done one.

 

20191020_201153-1.jpg.804e88e9270a96ba5a729b5f5c3a12cb.jpg

 

Admittedly I turned the wheels - with 2mm shaft - on the lathe and then fitted the tyres that were on the original plastic centres. The motor is a nominal 3v job and the power comes from a LIPO battery. It's radio controlled and that all works. It's the other end where I still need to get either a Faller front axle sorted for the wider 4mm scale track or fabricate one that has caused the hiatus in progress.

 

Shortening he drive shaft with a cutting disk works. Slow progress with pauses for cooling down is sensible though on the motors I've worked with the bearings have been brass so are proof to a bit of heat.

 

Sorry to all for the bit off topic here.

That looks interesting. Where did you get the gears from ?

 

For the steering units, try KKPMO.

"1:87 steering mechanism LKW-POM 20mm axle." Price: £7.00.

This is a bit wider than the Faller units, and it comes in kit form.

Available from DCC Train Automation.

 

All the best

Ray

Link to post
Share on other sites

  • RMweb Gold
1 hour ago, whart57 said:

 

Or more specifically an N20 motor with double shaft. I've found some on Amazon now, but a question. They come in different speeds. I'm guessing the 95-381rpm would be the one for small wheeled locos with the 34-136rpm for large wheels. What do you think?

Rough and ready calculation…

 

With 60” (5’) wheels going at 60 mph, the axle will be revolving at 280 rpm.

with 30” wheels, an axle rpm of 280rpm produces 30 mph.

 

I.e. speed in MPH = driving wheel diameter in inches x 280 rpm.

 

Since engines with larger wheels were designed to go faster, and certainly through most of the 19th century the biggest limitation on speed was driving wheel RPM (due to piston speeds, and the ability of bearings/glands for wheels and cylinders to cope with much above 300 RPM, or probably even close to it in the early days), then you can use one ratio for everything, unless you want something to go particularly slowly (or faster).

 

Also, the speeds quoted are the maximum “no load” speeds, so it is useful - but not essential - to work at about 75% of that most of the time.

 

Long story short, the 381 rpm will work very well for virtually anything, including a bit of high speed running every now and again (a Stirling single at 380 rpm will just about exceed Mallard’s record!) but if you only have a short run and never get up to full throttle, you can always go for something slower.

 

Remember that the driving wheels are used as part of the trade-off between tractive effort and speed on the real thing, so are part of the “gearing” mechanism on the prototype.

 

Also, if you have an independent final drive, then in the unlikely event of a mechanism failure, you can simply replace it with a new one without having to remove the wheels.

  • Like 2
  • Informative/Useful 1
Link to post
Share on other sites

I think the maths is a little awry here.

 

60 mph is one mile per minute, or 5280 feet per minute. The circumference of a 5' diameter wheel is 5 x π or 15.7'. So the rotation speed of a 5' driver at 60 mph is 336 RPM.

 

It's probably more useful to consider 30 mph the top speed of a steam engine of the sort most of us run. So that would be half that or 168 RPM.

 

The loco I have in mind though has 4' drivers and is unlikely to go faster than 25 mph. I think the equations are:

 

RPM = distance covered in minute/circumference of driving wheel or Distance (feet) = RPM x wheel diameter (feet) x π

Distance in feet = Speed (mph) x 5280 / 60 = Speed (mph) x 88

Speed (mph) = RPM x wheel diameter (feet)/28, 28 being approximately 88/π

 

So with 4' drivers 34 RPM equates to 4.8 mph, a brisk walking pace and 136 RPM equates to 19.4 mph. On the faster motor with 4' drivers 95 RPM would equate to 13.5 mph and 381 RPM would equate to 54.4 mph.

 

Now one problem is that scale speed might not be so easily determined. Even so it would seem that 136 RPM is still too low a top speed. However I'm likely to fit DCC or if not use a pulse controlled supply so the bottom RPM could be made slower.

 

I think the 95-381 RPM is the one I want. Do others agree?

  • Informative/Useful 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...