Highland Railway Drummond 0-4-4T Passenger Tank

The mudguards are secured with M2 x 3 screws



Pivot block next

Paul

 

Mark 1 pivot block, this is the one between the bogie side frames



Currently a M4 hex nut is fitted in the base. A M4 cap screw (length to be determined) is treaded through chassis mount, and a spring (on order, if they have too small an internal diameter for an M4 to pass through then an M3 nut and cap screw may need to be substituted).

The two small holes in the side are taped M2 all the way through. The nuts are there to lock the M2 cap screws used to secure the sides in place. The screws are tensioned to prevent slop but allow the frame sides to pivot.

Atest print will be required to check for alignments and for the location of the plunger spring wires

Looking at the above images, I've just rotated the M4 hex nut through 90 dgrees, to give a bigger amount of thread.



Time to arrange the test prints

Paul

 

Print test setup



Left hand set setup with models raised from the bed by 5mm and supports added at 60% density.

Right hand set rotated 45 degrees in the x axis. half set up with the cosmetic side up, the other with the cosmetic side facing down.

Just need to set the printer up to go and wait an hour or so.

Paul

 

Prints completed

First up the prints paralell to the baseplate.

Mudguard front

Mudguard rear

Pivot block

Side frame outside

Inside

45 degree print angle

Both side frames

Pivot block and mud guards upper face

lower side

These leaving to dry fully before curing. I will then be able to assemble them.

Paul

 

Comparing the two sets of prints, rarely this time the set printed paralell to the base plate turned out the better looking.

However, the spring detail was indistinct, the front face of the mudguard was tto delicate (0.3mm thick) and the fit of the mudguards to the frames was too tight.

I've extruded the springs out by 0.2 mm, increased the front mudguard wall to 0.5 (same as the rear wall) and opened up the clearance on the guards over the frame.



Now as these will not be the final print, I haven't done any cleanup.

The pivot block was tapped M2 - need to reduce the printed hole size as the tap went in too easily, and it needs more meat.

The 2mm ID 5mm OD bearings push into the side frames. The holes for the 1/8 th brass bushes needed opening up with a broach, and will be secured with Loctite, but not on the mockups.

I think with the pivot block I will increase the width to include a hex recess for the locknuts.

How much side play should I allow ?

Currently the frames are just under 25 mm to the outer side and the chassis frames are 26mm over the outside.

I'll work on the modified pivot block in the morning

Paul

 

Thanks Andy

Looking at the last two images

The rear frame was printed at 45 degfrees, with the inner face on the under side. The surface is pock marked and the supports are more visible.
The nearside frame was printed at 0 degrees only the lower has the surface defects.

Looking at the image from above

The rear frame has a matt smmoth appearance, whereas the front frame is glossy, but you can see the layer lines. Which demonstrates the reasoning behind tilting the models to minimise the appearance of layers.

Remember there has been no cleanup, and these resins sand easily.

Hopefully I'll start on the pivot block this afternoon.

Paul

 

Hi Andy

For these I have done, my profile for the Mono X seems to work and the raft seems to giving more success.

I need to perservere with Lychee software, but that can wait for now.

Paul

 

Pivot Block Mk 2

I've increased the width of the block by 4mm to accomodate the two M2 nuts (1.4mm each) plus 0.3 mm per side to take up a little of the slack, the rest will be with 1/8 th washers.

Also added is 4 x retaining screw holes for M2 Self tapers to either clamp the pick spring wire with a washer or fasten down a brass etch on each side that will have the spring wire soldered to it



Using Chitubox to set up the print job.

Support settings
All raised from the base by 5mm
70% Support density

Print settings



I'm printing 4 pivot blocks to allow for brealages, plus two full sets of bogie parts



Estimated 1 hour to print so probably 1h20m to 1h 30m in reality.

Time for a coffee or two

Paul

 

Printed at 1h 3m - I must be getting closer to the actual print settings.

All parts washed now just need to leave them to dry off before curing.

However while still soft I tried to fit the M2 hex nuts - NUTS !! the holes too tight, I tried to help squeeze them in but it cracked the block

While I was at it I drilled out the holes to 1.5mm. Tried fitting a M2 Cap screw and Self tapper both burst the web. I kinda expected this that's why I printed extra. Tried a larger drill / broach / reamer all had similar results.

Pivot block Mk2a was born ......

The hex radius was increased to 2.25 to give 4.5 across the points - actual measurement is 4.1mm.

The lugs were increased in size and we have ...............



and were off to the printer



approx another hour, but I have a zoom meeting this evening so progress update will be later.

Paul

 

Progress made today and a few deliveries

The Mk2a is a success

Assembled - I still have to glue the bearings and nut in place but its together

The 4 retaining screw holes tapped M2.

The 3/8ths tap arrived and the bearing now fits

All my original Chinese ordered bearings have also arrived, ready for the next project.

And the last delivery 100 x 25mm brass panel pins - measuring 1.3mm diameter, these will form the pins for the bogie plunget pickups.

The only downer was when I tried to fit the motor and gears, since the original tests, I thickened the frame sides, now the 46T tooth rubs against frame side

just as well I printed the 28T/41T combination, which will give approx 6):1 final ratio.

Back to working on the chassis to get the bogie mount and then work on the clearances, oh and then were at the etching stages - coupling rods, brake gear and name plates. The stainless steel strip has arrived - another new skill to learn.

Paul

 

I'd spotted that as well, the other side is ok, but as Andy said this is not the final version. Actually this was the 2nd version of the chassis - thicker frame sides and the motor mount built in and additional temp supports to help the build.
I believe the crack occured where a support was on the inside edge of the bearing contact surface, I will need to watch out fot that on the next version.
Of it happens again and everything else is ok then I may add some resin and cure it as a gap filler.

I'm hoping that the third version will be pretty close to being correct, but realistically probably version 4 or 5 are likely to be needed.

Paul

 

Very possibly, did wonder whether I would have been better off with flanged bearings, also wondering if to replace the front bush with a bearing.

Thought I'd better try the mudguard attached using an M2 cap screw

needs a little further cleaning up

Paul

 

Hi Rob

I had thought about it, but wasn't sure where to source axles etc, but is definately doable, even now for the bogie, not sure about the drivers tho'.

Paul