Building an 0-4-0 outside frame tank loco

[gregh]

I wanted another small steam loco for my indoor Claymine Branch.
And I thought an outside frame type might be different. So I purchased a Bachmann motor block from a 45t centre cab diesel.

bachmann centrecab motor block (1).JPG (108.41 KiB) Viewed 1956 times

One unforeseen problem is that the wheels are quite large – 41mm dia.
Note the metal ‘ spigot’ on the motor block that sticks up.

So what loco to build? I liked the look of this “Bell” loco, so I started sketching what I could build on that motor block.

Bell Chooch.jpg (129.86 KiB) Viewed 1956 times

BTW, I started this idea in this Topic
https://gardenrails.org/viewtopic.php?f=29&t=14496


The outside frames would need to hide the large wheels, but the motor block height at 41mm (?) above rail was a bit high for a small loco. I decided that the baseplate at 43mm above rail could be partly hidden by the side tanks extending below the baseplate as per the prototype.

Like all my ‘designs’ the body is designed to fit in all the ‘ stuff’ that I need, and to allow access. Not a prototype to scale. I decided the side tanks had to hold three AA cells on each side of the loco. (I had done some tests and found that 6V would give about 25kph scale speed, so the nominal 7V of 6 cells would be enough.)

I purchased a Pololu bidirectional speed controller for use with my usual Hobbyking 2.4GHz receiver. This ESC uses a centred ‘stick’ which is pushed up for forward and down for reverse and has to be held in position. This is OK for the short indoor line. (I could remove the stick spring )
These ESC are only about 10 AUD but their limitation is a max voltage of 8V.

ESC+ Rx.jpg (154.23 KiB) Viewed 1956 times

The esc and Rx are in the boiler front and have to be inserted from the front (smokebox) because of that spigot sticking up. (I cut some of it off)

I make my own sound circuit so I can make it any size to fit anywhere – probably in one of the side tanks. The small speaker will be in the other side tank.

Here is the final design..

component layout.jpg (58.44 KiB) Viewed 1956 times

I had to cut off bits of the existing ‘diesel looking’ frames and springs, so that the new sideframes I make will slide between the wheels and coupling rod+weights.

compare sideframes.jpg (415.03 KiB) Viewed 1956 times

So I finally put knife to plastic and cut out the baseplate from 2mm thick styrene sheet.
(I buy styrene sheet in 5’ x 3’ sheets of 0.5, 1.0, 1.5, and 2.0 mm thicknesses.)

first baseplate(2).jpg (149.22 KiB) Viewed 1956 times

I contact glued two aluminium angles to the motor block ends to support the baseplate and to allow me to screw the whole body onto the block, from underneath.


Then I screwed the baseplate onto the motor block and somewhere I had got my measurements wrong. The baseplate was 51mm above rail – much higher than the planned 43mm and it looked horribly wrong!

to be continued when I figure out how to proceed...................

[GAP]

Greg,
Looks interesting.
Quick question what is the part number for the Pololu?

[ge_rik]

Good start Greg. I have to say it was threads like this of yours on GSC (or GSM as it was then) which got me started scratchbuilding my own locos. You have a lot to answer for .......

Rik

[-steves-]

The only way to lower the footplate is to cut around the motor block and lower everything around it. The issue there is you will lose a lot of internal space for gear. Something with smaller wheels would help as the footplate height is usually limited to the wheel size. Does it have to be that loco for that motor block?

[gregh]

Greg,
Looks interesting.
Quick question what is the part number for the Pololu?

This is where I bought it. Note limited supply!

https://www.ebay.com.au/itm/17616946940 ... %3A3663644

[gregh]

The only way to lower the footplate is to cut around the motor block and lower everything around it. .......

I'm already way down that path........... much testing of clearances to be done.

[-steves-]

Greg,
Looks interesting.
Quick question what is the part number for the Pololu?

This is where I bought it. Note limited supply!

https://www.ebay.com.au/itm/17616946940 ... %3A3663644

I used to use those, they work very well but I eventually got annoyed with the squeal they have at low running. I swapped them all out for Deltang / Micron Radio ESC's and found I got rid of the squeal as well as I needed much less room to fit the gear as the ESC and RX are combined. Along with that I switched to Li-ion batteries and saved a huge amount of room. Might be worth a thought for this loco if you have to drop the footplate as you would only need 2 batteries to get 7.4v.

[gregh]

I used to use those, they work very well but I eventually got annoyed with the squeal they have at low running. I swapped them all out for Deltang / Micron Radio ESC's and found I got rid of the squeal as well as I needed much less room to fit the gear as the ESC and RX are combined. Along with that I switched to Li-ion batteries and saved a huge amount of room. Might be worth a thought for this loco if you have to drop the footplate as you would only need 2 batteries to get 7.4v.

A couple of points.
I have more than a two dozen AA cells on hand so no need to buy much more expensive 18650 - and I will have room in the tanks for the six AA.

remembering this is just for indoor use.....

Compare the prices. Hobbyking Rx+ Pololu ESC maybe 35AUD - less than 20GBP. Deltang in UK?? in Australia ?????

Yes the Pololu do make a high pitched PWM noise. A couple of ways to 'mitigate'
1. have a good loud sound system!
2. Always choose a battery voltage just high enough to give you the top speed you want. That way you are usually operating at close to 'full on' where the PWM noise is low or off.

Anyhow, I am still progressing with the build - more dreaming than building, but getting there!

[Old Man Aaron]

You sure know how to pick an interesting prototype. Looking forward to the result, in time.

[gregh]

You sure know how to pick an interesting prototype. Looking forward to the result, in time.

Thanks Aaron - the final thing probably won't look like what I started out to model.

Anyhow, here is the next exciting episode of slow progress.

So after the debacle I decided to cut a big hole in the baseplate to allow it to fit down over the motor block. This weakened the 2mm styrene but luckily the outside frames running the length of the loco have strengthened it.
I also had to pull the glued alum brackets off the block to re-glue them lower them. And all the side tank pieces that I cut out are now wrong size too. Grrrrr.

second baseplate and sideframes.JPG (199.89 KiB) Viewed 1512 times

I used a new (to me) method from YouTube to make ‘ fillet welds’ where 2 pieces of styrene are glued at right angles. The ‘fillet’ is made from Baking Soda powder, then superglue is dripped on. It sets like ‘rock’. But looks pretty ugly.

fillet3.jpg (292.03 KiB) Viewed 1512 times

Then I had to make a ‘bridge’ over the motor block for the boiler to sit on and attach to.

2nd baseplate on motor block.jpg (125.79 KiB) Viewed 1512 times

After much filing I managed to get the new sideframes to clear both the wheels and side rod/weights, but finally I could bench test it with no scraping noise.

Then it was time to solder the six AA cells together and test the whole thing on battery power with the esc and RC, and all OK! – giving 30 scale kph on 7V.

(As a side issue, I had tried to remove the coupling rod and weights to get easier access to the original side frames. I had to ‘dig’ small plastic covers off the axles. The rod+axles are then held on to the axle by screws that seemed to be Loctited on. So I decided to not continue.)

I had a leftover smokebox from a Bachmann Big Hauler and added a bit of 50mm pipe to it using epoxy, for the boiler. Then a 0.5mm styrene ‘wrapper’ around the pipe. The smoke box door is a push fit to allow the electronics to be put in. It will be superglued, epoxy, and styrene glued to the baseplate and ‘bridge’. Still looking for a suitable small dome in my spare parts boxes.

Then I got sidetracked by electronics and programming – figuring out how to get a voltage to represent speed from the ESC H-bridge. I decided to let the sound Picaxe do the subtractions of the two motor contact voltages, but it is not working.

[Andrew]

I used a new (to me) method from YouTube to make ‘ fillet welds’ where 2 pieces of styrene are glued at right angles. The ‘fillet’ is made from Baking Soda powder, then superglue is dripped on. It sets like ‘rock’. But looks pretty ugly.

That sounds like it could be a useful trick, particularly where appearances don't matter, I'll give it a try sometime - thanks!

Looks like it's going to be a fun little loco, looking forward to watching it progress!

Andrew.

[GAP]

I used a new (to me) method from YouTube to make ‘ fillet welds’ where 2 pieces of styrene are glued at right angles. The ‘fillet’ is made from Baking Soda powder, then superglue is dripped on. It sets like ‘rock’. But looks pretty ugly.

That sounds like it could be a useful trick, particularly where appearances don't matter, I'll give it a try sometime - thanks!

Looks like it's going to be a fun little loco, looking forward to watching it progress!

Andrew.

Wondering if it could be filed down smooth.

[gregh]

There's hundreds of videos on youtube about baking soda and superglue like this one

https://www.youtube.com/watch?v=WKu2mB1BrN0

BUT, my superglue does not instantly soak into the baking soda - more like water drops on dry soil. The superglue just runs off. Would be nice to find if a different superglue works better than the 4 tubes for $3 stuff I use.
It really is rock hard and not easy to file - the pic above shows after I attempted some filing.

If anyone does more experiments how about a separate Topic?

[-steves-]

There's hundreds of videos on youtube about baking soda and superglue like this one

https://www.youtube.com/watch?v=WKu2mB1BrN0

BUT, my superglue does not instantly soak into the baking soda - more like water drops on dry soil. The superglue just runs off. Would be nice to find if a different superglue works better than the 4 tubes for $3 stuff I use.
It really is rock hard and not easy to file - the pic above shows after I attempted some filing.

If anyone does more experiments how about a separate Topic?

Just use a thinner superglue. They come in different viscosities, thin is great for soaking into anything and thick is good for bridge filling. Kicker is also a good way of hardening superglue.

[Peter Butler]

Greg, I'm really surprised that you feel the need to add this mixture. I find that plastikard forms a strong bond if a solvent (eg. EMA Plastic Weld) is used to weld the surfaces together.
Tube glues, or superglue don't have the same effect as they just sit on the surface.

[Andrew]

Greg, I'm really surprised that you feel the need to add this mixture. I find that plastikard forms a strong bond if a solvent (eg. EMA Plastic Weld) is used to weld the surfaces together.
Tube glues, or superglue don't have the same effect as they just sit on the surface.

Personally, I was thinking it might be useful in some applications where I currently use Milliput or similar. The one I'm thinking of, off the top of my head, is securing a bolt inside a (biro tube) brake column, so it can be fixed to a carriage floor. It would probably be easier to put the bolt in, fill with powder and add superglue...

[Peter Butler]

I totally agree with your comment Andrew and I work in a similar way, usually using epoxy adhesive etc... From my experience with attaching plastikard to plastikard using solvent, even on large section such as structures, I have found solvent works well enough on its own.

[-steves-]

I totally agree with your comment Andrew and I work in a similar way, usually using epoxy adhesive etc... From my experience with attaching plastikard to plastikard using solvent, even on large section such as structures, I have found solvent works well enough on its own.

As solvent melts the plastic, it creates a weld rather than a traditional glue. For this reason it is usually stronger on the weld line and it's generally the plastic either side of it that tears.

[Old Man Aaron]

I tried the baking soda on my Simplex a while back, to similar effect. Not for me.

[gregh]

After wasting a week on Picaxe programming, I finally came back to actual modelling.


I found a small dome from some old kitbash and glued and screwed it to the boiler.
I epoxied the boiler to the baseplate, with all the usual hassles of getting it centred on the baseplate, making sure it is level lengthways and that the funnel is vertical.

boiler on base.JPG (217.05 KiB) Viewed 909 times

The firebox backplate is also a push fit like the smokebox, to allow access to the electronics in the boiler.

Then I could start making the side tanks. These had to be ‘deep’ enough for AA cells diameter– ie 16mm internal and they just fitted beside the boiler – for once my measurements worked. They were made from 1mm styrene covered with 0.5mm styrene which had the rivets embossed from the back using a dressmakers tracing tool. I made so many errors in cutting all these out that I began to wonder if I would ever finish this build.

side tank mockup.JPG (277.24 KiB) Viewed 909 times

The batteries ( six AA, NiMH rechargeables) were soldered together – 3 on each side of the loco. As usual I solder directly to the cells.
I have enough space in the tanks to be able to put the sound board in one and the speaker in the other (I hope)

batteries.JPG (244.99 KiB) Viewed 909 times

By now I have the wiring diagram decided ie where things go and how to connect them and hopefully holes in the right place for all the wires.

wiring diagram.jpg (48.94 KiB) Viewed 909 times

Now it’s off for undercoating, so I can do no more work for a few days until it is really dry.
Time to make the sound board..