Garden Railway Forum

Ahhh, thanks Peter, but I haven't shown you all the booboo's that I have, or am trying, to put right!

As I said before, I had to make the chassis in two parts because the printer isn't big enough to do it in one. Now, somewhere along the way, I've introduced a 2mm error between the chassis sides and the footplate top which didn't show up until it was all glued together. It isn't catastrophic but putting it right involves a fair few modifications.

philipy wrote: ↑Tue Dec 06, 2022 3:22 pm Ahhh, thanks Peter, but I haven't shown you all the booboo's that I have, or am trying, to put right!

On second thoughts, perhaps I'll have a rethink before placing an order?

Very wise!

This is looking very nice. The detail you are creating looks really good. I will be interested to see how robust the finished locomotive is. I suppose it is all down to the resin - as in finding the one with the right properties. I have successfully used printed connecting rods - so I think all of your valve gear should oscillate convincingly.

And I was about to add metal details to my printed locos!

Trevor

There has been a long hiatus caused by all sorts of non-railway issues, plus the fact that I wasn't very happy with the way my DeWinton was going, so the bits have all sat in a box for the last 4 months. Anyway, a few days ago I forgot about what had gone before and collected together all the individual SketchUp drawings of the components and assembled them into one complete drawing.. stl'd it...sliced it and resin printed it as one complete all-at-the-same-time model. It took 9 hours and this is the result:
The original print actually had the arms of the regulator as well but I accidentally broke them off whilst I was cleaning the supports off.
I left the water tank filler off so that there was a resin drain hole and also didnt include the boiler top and chimney for similar reasons.

That does look good. Resin? Did it require many supports?

Rik

ge_rik wrote: ↑Sat Apr 15, 2023 11:55 am That does look good. Resin? Did it require many supports?

Errrr... just the odd one or two.

Printed it upside down with a raft on the buildplate, so the supports for the visible flat areas ( Footplate, tank top, etc) are hidden underneath and that does look a bit of an uneven mess. I'm never sure how much support to place on a flat surface like that
I did think about taking a pic as it it came off the printer but didn't want resin all over the camera so didn't bother.
This is a Chitubox reconstruction of the sliced file, fwiw:

philipy wrote: ↑Sat Apr 15, 2023 10:39 am Anyway, a few days ago I forgot about what had gone before

First Law of Holes. 'If you find yourself in a hole, stop digging.' I've got a couple of rolling chassis sitting on my bench slowly building up a nice patina.......

Have you worked out how to fit a motor, ESC and batteries in the model? It doesn't look like there's a lot of space to go around.

Graeme

GTB wrote: ↑Sun Apr 16, 2023 12:57 am

Have you worked out how to fit a motor, ESC and batteries in the model? It doesn't look like there's a lot of space to go around.

There is actually a surprising amount of space, as long as I'm not trying to fit in a big Como motor/gearbox.
My original plan was 5xAAA NiMh together with an Rx41c & ancilliary board, which includes an ESC, in the water tank. Then a double transverse shafted N20 gear motor which was left over from the contractors loco, mounted vertically in the boiler and chain drives to both axles.
However that did create challenges with the drive, in that the front axle has the two eccentrics on it. I managed to print a double eccentric with chain sprocket between them, but that means that the drive sprocket on the motor has to be exactly on the loco centre line to line up with the axle sprocket and that gives me a width problem to get another sprocket on the other shaft - it fouls the sideframe. I've tried to put both sprockets on one side of the motor but the shaft isn't really long enough. So at the point where I stoppped, several months ago, I was thinking of keeping it simple and going back to just driving the uncluttered rear axle.

Thinking about it again earlier today, (in bed!), I realised that there is actually just enough room in the coal bunker to get the motor vertically in there, and that then throws up a variety of options: 2xchain drive forward to either one or both axles, spur gears and layshaft to rear axle ( or both, but I'm not sure my drawing skills are up to drawing and printing a bevel gear between the two eccentrics), etc. What this plan does do however is to leave the boiler empty for centre located weight, or, potentially now space for sound - what did a DeWinton sound like? Given that their main business was marine engines, I'd guess it sounded like a 2-cyl. vertical marine engine....now where have I heard that before??
All needs a lot more thought!

Hi Philip
Didn't the de Wintons have fly cranks? Wouldn't that solve your problem of driving the unpowered axle?

Rik

ge_rik wrote: ↑Sun Apr 16, 2023 9:37 am
Didn't the de Wintons have fly cranks? Wouldn't that solve your problem of driving the unpowered axle?

Yes they did, but I'd be concerned about quartering going out ( or getting it in in the first place!), without doing some 'proper engineering'

philipy wrote: ↑Sun Apr 16, 2023 9:54 am

ge_rik wrote: ↑Sun Apr 16, 2023 9:37 am Didn't the de Wintons have fly cranks? Wouldn't that solve your problem of driving the unpowered axle?

Yes they did, but I'd be concerned about quartering going out ( or getting it in in the first place!), without doing some 'proper engineering'

I used fly cranks on my latest motor block - primarily because there wasn't room for Delrin chain and sprockets. Like you I was a bit apprehensive at first, but they turned out to be a lot easier to model in 3D printing than I expected.

Firstly, I decided to use grub screws and square nuts to hold them in place. The smallest I could find on eBay were M2.5. You might be able to find smaller elsewhere

I then drew the fly cranks to accommodate them
I'd hoped that 2mm holes would be sufficient to hold a 2mm crank pin (2mm bolts with Allen key heads - eBay once more) in place, but I found I needed to reinforce the back of the cranks with a locking nut to stop them unscrewing.
The concept of "quartering" is actually quite flexible. Whilst a precise 90 degree angle is probably more essential for a live steam loco, it seems as if there is a lot more leeway for our electrically powered models. As long as the opposite cranks are roughly at 90 degrees but more importantly are aligned with each other on each side, then it works.

Rik

Thanks Rik, thats all interesting and I confess I hadn't thought of that, but its certainly another option to look at.
I've just done a quick look round and I can find M1.6 grub screws and hex nuts, but the smallest square nut I can see are M2. I guess a tiny touch of glue would hold a hex nut in place.

I found that the forces exerted when trying to tighten the grub screws tended to make the necks of my FDM printed fly cranks delaminate, but I found that printing them with 100% infill discouraged this. I've not tried resin printing them as I figured they might be too brittle.

Rik

Very nice!