7mm Steve Beattie 3D-Printed Class 22

smgee

smgee

Active Member
Greetings fellow Thunderers. I thought I'd start a build thread on a new Steve Beattie Class 22 kit. I'm sure I'll be calling on the WT big brain from time to time...

The kit is predominantly 3D-printed resin, with chassis components in more sturdy FDM. It wasn't hugely expensive at under £190, but not as refined as the JLTRT/MM1 offering, so I'm intrigued to see what can be made from it. This will definitely NOT be a cost-no-object build!

IMG_3837.jpeg

I decided to build a running chassis first. The frame comes in 2 sections, with some locating/reinforcing brass dowels (thick wire) at the joint faces. The faces needed a small amount of tidying, and the holes for the brass dowels needed deepening slightly. The two halves were glued together on a flat surface, up against a straight edge, using some VMS flexible black CA, which is great for seeing how much you've got on your fingers!

IMG_4831.jpeg

IMG_4826.jpeg


Next job, fit the bearings to the bogie frames. This is where I hit my first problem...

The bearings are standard 0.25" / 6.35mm OD, but the holes in the bogie frames are 7mm. I wondered about just glueing them in with the wheels fitted, sat on a flat surface, but they were all over the place and wouldn't stay put.

IMG_4819.jpeg

I found some 7mm OD plastic tube to sleeve down the bearing holes. This was glued in place, the ID opened up fractionally to fit the bearings, and the whole thing checked on a flat surface. Spot on.

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The bearings were glued in and the excess tube cut away.

IMG_4829.jpeg

In case you're wondering, those slots in the cross pieces are for a Delrin chain. We'll be re-visiting those shortly!
 
timbowales

timbowales

Western Thunderer
Steve, those wheels look like disc ones. I was under the impression that Class 22 DH had spoked wheels?

edit: Just checked in BR Main Line Diesels and, yes, spoked wheels!
 
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smgee

smgee

Active Member
Next job, gearbox, motor and Delrin...

In an attempt to keep a lid on costs, I decided to power a single bogie. It shouldn't be a heavy model and won't be pulling huge loads. The Roxey Mouldings 13:1 gearbox is very reasonably priced and I found what I think is the 1833 sold by Taff Vale, but from an alternative source - so under £30 for both.

I've never built an etched gearbox before, but managed to put it together without making too much mess. It seems to be a nice, compact unit, but the worm wheel would not fit on the axle. It's hard to measure the bore accurately with callipers, but it's definitely undersize. Hmm, there seems to be a bit of a theme developing here! Those bearings are just for show and not fixed in yet.

IMG_4918.jpeg

The next problem revealed itself when I took some measurements. The gearbox frame is approx 12.6mm wide, the Delrin sprocket, 7.9mm wide. My calculator says that's 20.5mm. The space within the bogie frame? 19.8mm. Arse.

IMG_4942.jpeg

Of course, I'm conveniently ignoring the bearings, which only make matters worse. The flanges of the gearbox bearings are each 1mm thick, and the bearings in the bogie intrude inside of the frames slightly. They can be filed flush, and I figure I'll have to narrow the Delrin sprocket by 0.8mm or so, but I'm not sure what to do with the gearbox.

With the bearings arranged like this (contrary to the instructions), the worm wheel is spaced to roughly the right place:

IMG_4943.jpeg


So what about turning up some new bearings like this, that are both flush with the frame and space the worm wheel correctly (exact measurements TBD)? I'd welcome the thoughts of the WT Big Brain here!

IMG_4943.jpeg
 
Last edited:
Osgood

Osgood

Western Thunderer
Or you could swap the bearings over to the opposite side so that the flange is on the inside, spaced from the frame by washers to get a snug clearance fit with the gear, then solder the lot up and simply file off the part that protrudes flush with the outside of the frame sides?
 
Overseer

Overseer

Western Thunderer
smgee said:
Next job, gearbox, motor and Delrin...

In an attempt to keep a lid on costs, I decided to power a single bogie. It shouldn't be a heavy model and won't be pulling huge loads. The Roxey Mouldings 13:1 gearbox is very reasonably priced and I found what I think is the 1833 sold by Taff Vale, but from an alternative source - so under £30 for both.

I've never built an etched gearbox before, but managed to put it together without making too much mess. It seems to be a nice, compact unit, but the worm wheel would not fit on the axle. It's hard to measure the bore accurately with callipers, but it's definitely undersize. Hmm, there seems to be a bit of a theme developing here! Those bearings are just for show and not fixed in yet.

View attachment 234479

The next problem revealed itself when I took some measurements. The gearbox frame is approx 12.6mm wide, the Delrin sprocket, 7.9mm wide. My calculator says that's 20.5mm. The space within the bogie frame? 19.8mm. Arse.

View attachment 234492

Of course, I'm conveniently ignoring the bearings, which only make matters worse. The flanges of the gearbox bearings are each 1mm thick, and the bearings in the bogie intrude inside of the frames slightly. They can be filed flush, and I figure I'll have to narrow the Delrin sprocket by 0.8mm or so, but I'm not sure what to do with the gearbox.

With the bearings arranged like this (contrary to the instructions), the worm wheel is spaced to roughly the right place:

View attachment 234497


So what about turning up some new bearings like this, that are both flush with the frame and space the worm wheel correctly (exact measurements TBD)? I'd welcome the thoughts of the WT Big Brain here!

View attachment 234501
Click to expand...
Being lazy, I would just use the gearbox bearings as intended with the larger diameters adjacent to the worm wheel plus space for thin washers, then solder the bearings in place and file off anything protruding on the outside of the gearbox. Achieves the same result as custom turned bearings with no effort.

Narrowing the delrin sprocket should not be a problem. I don't like stressed delrin (can result in splitting) so would make sure it is a sliding fit on the axle and drill and pin with a small piece of wire through the axle.
 
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