Garden Railway Forum

Thanks chaps. I thought I was saving myself a lot of work, using the Bachmann chassis, but in the end it would have been quicker and a lot less complicated to have built the chassis from scratch.

We live and learn .....

I'm really pleased with the power those GA25-370 gearmotors can deliver.

Rik

ge_rik wrote: ↑Sat Feb 21, 2026 4:28 pm I thought I was saving myself a lot of work, using the Bachmann chassis, but in the end it would have been quicker and a lot less complicated to have built the chassis from scratch.

Was wondering how long it would take you to come to that conclusion............

I've found that 'Gears and Gear Cutting by Ivan Law',which is Vol. 17 in the Workshop Practice Series published by Special Interest Model Books, is a useful reference when building a mechanism. Widely available, both new and s/h, and cheap by comparison to current book prices.

The first half of the book is the relevant part in our case. The second half is about DIY gearcutting, best avoided unless you want to enter the dark side..........

Graeme

Nice looking loco and an impressive runner Rik. Out of interest, what ratio reduction is the GA25-370 you are using?

Durley wrote: ↑Sun Feb 22, 2026 7:39 am Nice looking loco and an impressive runner Rik. Out of interest, what ratio reduction is the GA25-370 you are using?

I've been using GA25-370 (282RPM) 12v gearmotors from AliExpress. They seem to provide a realistic speed with 1:1 bevel gear transmission for my locos using 3 x 18650 li-ion cells

Rik

I see they are also selling them on eBay under listings for 25GA- 370

This data table in one of the listings might be useful

Voltage Gear ratio no load load Stall speed Current speed Current toqure Current toqure
12V 1:650 5RPM ≤150MA 3RPM ≤70MA 1150gf.cm ≤2.1A 15.4kgf.cm
12V 1:150 10RPM ≤170MA 7RPM ≤100MA 980gf.cm ≤2.1A 14.8kgf.cm
12V 1:150 30RPM ≤170MA 25RPM ≤100MA 770gf.cm ≤2.1A 12.0kgf.cm
12V 1:200 60RPM ≤170MA 51RPM ≤100MA 750gf.cm ≤2.1A 11.8kgf.cm
12V 1:100 100RPM ≤150MA 73RPM ≤185MA 660gf.cm ≤2.1A 10.5kgf.cm
12V 1:50 200RPM ≤180MA 165RPM ≤105MA 580gf.cm ≤2.1A 8.8kgf.cm
12V 1:30 300RPM ≤190MA 254RPM ≤145MA 180gf.cm ≤2.1A 7.8kgf.cm
12V 1:25 400RPM ≤190MA 344RPM ≤145MA 170gf.cm ≤2.1A 7.7kgf.cm
12V 1:20 500RPM ≤190MA 460RPM ≤145MA 150gf.cm ≤2.1A 7.5kgf.cm
12V 1:10 1000RPM ≤190MA 820RPM ≤145MA 88gf.cm ≤2.1A 7.2kgf.cm


Rik
PS I'll leave you to speculate what toqure is .....

ge_rik wrote: ↑Sun Feb 22, 2026 1:12 pm PS I'll leave you to speculate what toqure is .....

Chinglish for torque perhaps................

Maybe it was generated by AI, as the 'toqure' figures don't seem to make sense, like most AI slop.

This link is the data page for the equivalent gearmotors I use. My big diesel is fitted with two of their #3228 12V medium power gearmotors.

https://www.pololu.com/category/115/25d ... gearmotors

Graeme

ge_rik wrote: ↑Tue Jan 27, 2026 11:46 am A bit more progress. Not finished yet, a few more details plus a final rub-down, top coat and varnish. Also, awaiting the delivery of some 18650 cells to do the electrics
DSCI0611.JPG


DSCI0612.JPG


At present, she's very tail-end heavy - the balance point seems to be just ahead of the rear drivers, so I'm going to have to be judicious about where I put the weights. I can't help wondering if the real loco would have been a rocky ride for the crew. She's crying out for two-wheel bogie under the cab, but the original was without.

Rik

I've only just noticed Rik, that it has the smokebox door opening to... the left

tommygander1941 wrote: ↑Mon Mar 09, 2026 4:17 pm

ge_rik wrote: ↑Tue Jan 27, 2026 11:46 am A bit more progress. Not finished yet, a few more details plus a final rub-down, top coat and varnish. Also, awaiting the delivery of some 18650 cells to do the electrics
DSCI0611.JPG


DSCI0612.JPG


At present, she's very tail-end heavy - the balance point seems to be just ahead of the rear drivers, so I'm going to have to be judicious about where I put the weights. I can't help wondering if the real loco would have been a rocky ride for the crew. She's crying out for two-wheel bogie under the cab, but the original was without.

Rik

I've only just noticed Rik, that it has the smokebox door opening to... the left

Oops. No photos of the front of the loco so it was a guess. Maybe a wrong guess.....

Rik

ge_rik wrote: ↑Mon Mar 09, 2026 5:57 pm

tommygander1941 wrote: ↑Mon Mar 09, 2026 4:17 pm

ge_rik wrote: ↑Tue Jan 27, 2026 11:46 am A bit more progress. Not finished yet, a few more details plus a final rub-down, top coat and varnish. Also, awaiting the delivery of some 18650 cells to do the electrics
DSCI0611.JPG


DSCI0612.JPG


At present, she's very tail-end heavy - the balance point seems to be just ahead of the rear drivers, so I'm going to have to be judicious about where I put the weights. I can't help wondering if the real loco would have been a rocky ride for the crew. She's crying out for two-wheel bogie under the cab, but the original was without.

Rik

I've only just noticed Rik, that it has the smokebox door opening to... the left

Oops. No photos of the front of the loco so it was a guess. Maybe a wrong guess.....

Rik

Ah I see, well most of the time locomotives had the door open to the right, seems like a typical Manning Wardle smokebox otherwise. Matthew Murray is a good reference

ge_rik wrote: ↑Mon Mar 09, 2026 5:57 pm Oops. No photos of the front of the loco so it was a guess. Maybe a wrong guess.....

Some John Fowler & Co locos have the hinge on the left, as do their traction engines.

Things are different in the freelance universe......

Maybe the PLR loco needed a heavy overhaul in the late '20s and Manning - Wardle had closed, so Fowlers got the job and it came back with a l/h smokebox.

Graeme

GTB wrote: ↑Tue Mar 10, 2026 1:39 am

ge_rik wrote: ↑Mon Mar 09, 2026 5:57 pm Oops. No photos of the front of the loco so it was a guess. Maybe a wrong guess.....

Some John Fowler & Co locos have the hinge on the left, as do their traction engines.

Things are different in the freelance universe......

Maybe the PLR loco needed a heavy overhaul in the late '20s and Manning - Wardle had closed, so Fowlers got the job and it came back with a l/h smokebox.

Graeme

Thanks Graeme. Good to know there's a possible plausible explanation.

The door was printed as a separate item and when I came to glue it on, it somehow looked better to my mind's eye hinged on the left. I wonder how many front end shots of locos I've seen over the years and never noticed the orientation of the smokebox door hinge. Mind you, I sometimes mistake right and left, something I inherited from my mum.

Rik

Just cast my eyes over my loco collection and found another loco where I'd hinged the smokebox door on the left. My sort-of Naismyth & Wilson (ish) loco based on one which ran on the Schull & Skibbereen Railway.

Darn it! I thought, this is becoming a habit. This too was constructed based on photos.

But..... wait a second! One photo of the original loco shows its smokebox door hinged on the left (unless the photo has been flipped)!

Vindicated (for this loco anyhow).

Rik