Garden Railway Forum

Hi all

Totally new to the forum and narrow gauge trains so I wanted to run what I’ve got in mind past those more experienced than me! I’ve been thinking up the spec of a brushless loco so wanted to check whether this could work before I start to look into local clubs. Only doing it this way round as I already have quite a few of the parts and materials needed to get going so I’d like to start CAD’ing something up sharpish:

• ‘B-B’ wheel & axle layout but only 1 axle at each end being driven by these motors ( https://flipsky.net/products/flipsky-el ... 70kv-1550w ). I already have these so keen to re-use them. I have tried working out how to drive each set of axles with a single motor but the need for some form of suspension makes it difficult.
• Motors running on 12V should mean that each motor produces approx. 500w.
• Assuming 100mm wheels and 5:1 gearing on 12v would produce a top speed of around 7mph. I have the belts and pulleys for this but does seem a little slow. Using fully charged batteries (i.e. 14v) would push the speed to 8.4mph
• As I already have them, I’d use VESC brushless motor speed controllers usually used for electric skateboards. I’d run the motors in sensored mode which is much better for low down torque
• Chassis would be a simple steel box section design. Bodyshell TBC.

Any help or advice would be greatly appreciated.

Cheers
Dan

Outside my realm of experience, but will be really interested to see how it develops. Please keep us informed.

Rik

All sounds good to me logic wise, though I do have to ask, how do you happen to have all the parts, what are they from?

I am very keen to see how this progresses

I have the parts currently in a fighting robot! bit bored of that hobby though.

danjr1 wrote: ↑Wed Jul 21, 2021 4:03 pm • Assuming 100mm wheels and 5:1 gearing on 12v would produce a top speed of around 7mph. I have the belts and pulleys for this but does seem a little slow. Using fully charged batteries (i.e. 14v) would push the speed to 8.4mph

I'd suggest 7mph is plenty fast enough, especially if you plan on carrying passengers on a club track. That is about twice as fast as a comfortable walking pace, probably about a fast jog. It works out to a scale 84mph for a model of a mainline diesel and they have much larger radius curves than miniature railway tracks.

Forty plus years ago, I was involved with a couple of friends in building some 5" gauge battery powered locos and we ran speed trials with the first chassis completed.

I can tell you from personal experience that hooning along at 10mph, with your bum only 3" above the rails, is well into white knuckle territory. We never did find out the max. speed of that chassis, but my friend got it up to 13mph that day and the inner wheels were lifting off the track on the curves.......

The drive train was modified to give a more sedate performance and the finished loco went on to give train rides to many happy young passengers.

If you look up the rtr 5" gauge battery locos made by Maxitrak, you'll find the max. speed is quoted as 6mph (10kph). Which suggests that is the speed range commonly used on club tracks in the UK.

Regards,
Graeme

A decent turn of speed might be useful if any of the "fighting robot" features remain - after you've flipped another loco off the track or sliced it in half, you'll want to get away from its owner pretty sharpish...

Sounds like a fascinating project, do keep us posted,

Andrew.

Thanks guys. Started sketching it up and all seems plausible. Just need to check the minimum radius of the local tracks so I can fix the bogie centre distance to confirm how many batteries I can then fit in.

Andrew wrote: ↑Thu Jul 22, 2021 3:50 pm A decent turn of speed might be useful if any of the "fighting robot" features remain - after you've flipped another loco off the track or sliced it in half, you'll want to get away from its owner pretty sharpish...

My armored railcar is waiting....







Weighs between 40 and 50 kgs.
Strong enough to pull me sitting on the driving truck.
Radio control, 6 channels. Turret can turn, barrel can go up and down, cannon fires, underfloor lighting, horn,....

We had a 5mm plywood mockup of the body. This was used to check if everything fits in. As it was no longer needed, the mockup body was put on the rails and the railcar drove right though it. Result: Matchwood!

Strewth! That's a mean machine

Rik

That is a very cool looking rail tank!

Tiny bit of an update. During my sketching, I started to think whether I could get away with two powered axles on the front bogie then only a single unpowered articulated axle at the rear? Theory being it would increase the proportion of the weight acting upon each driven wheel whilst reducing the rolling resistance from removing an unnecessary axle. Thoughts?

I would power all available axles and put enough weicht on the wheels.
You can have enough motor power but the real limiting factor is traction.

My Prussian P3.1 and my Bavarian PtL 2/2 (known as GLASKASTEN in Germany) have been given a block of lead between the axles, inside the frames,....
Dummy air tanks have also been filled with lead to improve traction.
An unpowered axle means a loss in traction.

Big one has 6 axle-hung motors and lots of weight (length: 1.65m over the buffers):


The first idea was to have the middle axle of each bogie unpowered but this would have limited traction to a great extent.
Traction is never a problem with this loco.

Scrat wrote: ↑Fri Jul 23, 2021 9:01 am As it was no longer needed, the mockup body was put on the rails and the railcar drove right though it. Result: Matchwood!

Found the pictures:

It went right through.



This part was cut by the flanges when the beast ran over it:

making slow progress with the design but have a question. What's better - oilite bushings or ball bearings? Axle RPM is looking like approx. 750rpm