Highland Railway Drummond 0-4-4T Passenger Tank

Hi Rob

The previous methods I'd seen for split axle involved using stainless tube, with a piano wire core wrapped with cotton, then smothered in araldite and inserted into the tube. Once set the tube was cut to provide the insulated drive shaft. But wasn't suitable for sqaure shaft wheels (it was for 4mm and Gibson or Sharman wheels).
Thanks for the links, I have reading to do .......

Looking at the chassis, if I use Slaters plunger pick ups I have a few issues. The plastic injected plunger housings to suit etched frames are tapered 3.7 dia at the boss end and 3.1 dia at the other. I would have to replicate the taper, and with holes tending to print slightly undersize would be prone to errors. Therefore I will need to replicate the housing, not an issue, just need to measure up the bits.

And then determine where to put the as the scope is limited for the centre axle due to the motor mount - keeps making split axles more attractive.

OK while all this procrastination was taking place, the mind starts to wander an the kid takes over .... I couldn't resist just seeing how it would look

Even without weight it has a heavy arse, and to get these picks I had to jack the back end up, otherwise it looked like it was trying 0 - 60 in 3 seconds

I knew there was a good reason to print extra pivot blocks

Ok break over - back to work

Paul

 

Well that's several hours I'll not get back

Chassis mods - fitting the plunger pickups, here's the final result



Now what would take so long, well on the center axle at the front side of the axle is the reduction spur gears, and behind the axle is the worm gear and the back of the gearbox.



This involved moving the bearing support for the gearbox back nearly 8mm, and any repair work to clean up the mess that made.

On this version of the chassis I have replaced the front bush with a bearing the same as the rear axle. Comparing the to axles the bearing fitted axle rotates so much more freely.

I will print this one up tomorrow, but I know there will be at least one more version as I have to check the bogie wheel clearences with and without mud guards fitted, and add the brake pivot detail.

Paul

 

Rather than have a print time of 6 to 10 hours, I decided to print hte model paralell to the print bed.



Just a 3 hour print now, and as can be seen a lot of heavy supports, with a lift height of 7mm.
Fingers crossed.
After doing the Slaters plunger pick up mounts, I may be tempted to do the same for the bogies as these will be a very simple modification.

Given how smoothly these bearing move, I'm tempted to make them my standard fitment for 3D printed chassis, but will try the flanged versions as these would be a little easier to secure. Mind you compensation may be fun.

Paul

 

Impressive Rob, it's food for thought for the next loco - which is liable to be a HR Barney, but I have a back log to clear first

While the print is going I started on the brake gear



These'll be fun to print, either 0.7 or 0.9 dia wire use to connect them up.

Paul

 

Stopped the print - the print was peeling off the bed

Unfortunately it takes over 2 hours before you can see the underside of the print base.

I know why - at least I hope I do. I watched a youtube video where they said if the base layers are printed at a cure time more than 5 or 6 times the normalt exposure then you could damage your LCD screen.

My base layer exposure was 40 sec with a standard exposure od 2.4 sec (over 16 x normal exposure). S o I reduced the exposure time to 20 sec still x 8.3 normal exposure, and failed big time.

I've reset the exposure time back to 40s, but also printing a 15 degree print as well



Hi Rob, if I was to get really anal about it they could even move as the have been shaped to match the wheel diameter, actually I could see the advantage to being able to un couple the pull rods and allowing the brakes to swing forward to make wheel removal easier.

3 hours 42 min to go - or 1h 40m until I can see the bottom of the build plate to see if they are attached.

Time to read up on either split axles or inkscape - I need to draw up the coupling rods.

Paul

This will add another hour to the print time, but should also show if it's just too much force required across the whole model at a time.

 

Just done something I rarely do and that was to pause the print, but as its only at layer 95 of 1270 and is still only printing supports I thought it should be ok.



Apart from a load of resin dripping from the prints that pretty much is how it looked.

3h 33m to go, but who's counting

Paul

 

1h 33m to go and Murphy is alive and well, both chassis are looking good from what I can see so far

Were up to layer 779 out of 1270



Fingers crossed


Made a Slaters Plunger pickup version of the bogie side frames



I will modify the pivot block to suit (remove the clamping screw lugs) and adjust the central boss to suit the compression spring to be able to set the ride height, oh I forgot they arrived to day as well.

Hopefully between the bogie frame ability to rock fore and aft and the compressin spring enough weight will be transferred forward.

Paul

 

Murphy just loves playing with us (or is that screwing with our minds), see if you print spares Murphy makes them all good, do one at a time and your fair game

Both the paralell and 15 degree and printed without issue.

interestingly there are some printing artifacts at the same height and not aware of anything happenening at the time.

Just need to let them dry properly before curing, and I'd like to get them with a bit more strength before I start to abuse them.

Paul

 

Running the chassis through the Curer sometimes you just have to be a little creative in how to support the print

and I just had to try the bogie mount

Now I need to make some bits for the chassis

Brake mounts



Modified Bogie pivot block for the Slaters Pickup frames - fasteners no longer required, and to recess the spring in to the block



And print up the Rear sand boxes, Slaters compatible bogie side frames, Brake blocks and hangers.

The brake hangers I've tried printing at 45 degrees on edge and flat, and the sandboxes printed paralell to the build plate and at 45 degrees

On the build plate it looks like this



We'll see in an hour and a half.

That'll give me time to drill out the pick up holes and brake mounting holes. Ream out the holes for the bearings and start the drive chain build up.

Will post up progress later.

Paul

 

I've drilled out the brake hanger 0.7, Plunger sockets 1.2 for the rear, and 2.3mm for the front section. Then reamed out the wheel bearing sockets.

The prints completed

Brake levers

And brake shoes

Reamed out the worm shaft bearing holes, and my Loctite arrived, so the bearings have been Loctited in place.

Motor fitted, and a 48mm long, 2mm dia worm shaft cut from stainless steel ground bar.

Now the first issue, I fitted the 41T to the worm shaft, but the plunger pickup sockets blocked the gear getting into place

Got round this by removing the gear from the shaft, threading the shaft through the bearings and worm. I will need to fit some PTFE spacers between the wrom and bearing, and the bearing and 41T spur. The spur gear will be Loctited in place, once all the bits have been added.

That's it for today .....

Paul

 

NUTS !!!!

I snapped the end off one of the plunger pickup sockets



Now I do have a spare chassis - I've beat Murphy again - I know a very brave but stupid comment

But I've spent a fair bit of time getting the chassis this far.

I could just fit the Slaters plastic injection moulded versions, but as stated earlier they are tapered, and without the correct tapered drill or reamer, I would only have point contact, fine for a 20 thou etched chassis, but my chassis is 2.0mm thick.

Ok time to print off some replacement plunger sockets - if I had done thid from the start the gearbox fitment would have been easier as well - lesson learnt for the next loco.
I have done two versions - with and without flange, with a print time of 1h 20m I may as well print a few - 9 of each actually - Murphy I waiting for you.




Print started.

Think I need to stick on the Sandboxes and brake hanger support collars, followed by some black paint to both the main chassis and the bogie.

Paul

 

YES !!! it worked, I drilled out the frame enough to take the new socket. Inserted the flangeless version, and glue in place with some resin, and cured it with a UV nail polish curer.

Now allowing it to harden.

As this loco has been mostly 3D printed, with only wire, bushes, bearings, buffers, fasteners, wheels, motor and worm gears being the extra bit, I just have to try printing the coupling rods.



Now as a test, I am printing these Vertical, horizontal and at 45 degrees



I'll be back

Paul

 

Print completed - all 12 coupling rods were given a 4min cure while still on the supports

Not all were successful

Left hand side top 2 were printed at 45 degrees - 2 of the coupling rod broke when trying to remove the supports

Left hand side bottom 2 were printed flat - again two broke when removing the supports

Right hand side all came off the supports without issue, however the top coupling rod, one of the boss supports had failed so the boss is distorted.

If I need to print these again I will print them verticle, however I will print them upside down, as the bottom edge is bellied, and printing them the correct way up puts the supports on the bellied side, flipping it will put the supports on the flat side, which is easier to file the support marks away.

And the chassis so far

Still need to paint the chassis.

Away to try and earn some brownie points and take SWMBO see the Mother- in-Law.

Back later - if I survive

Paul