0-4-0 GER tram chassis

[Marc Dobson]

I'm scratch building a GER 0-4-0 tram loco for my father's birthday present. Should I spring the chassis of leave it with solid wheel bearings?
Marc

 

[Nigel Cliffe]

I built one a few years ago in 4mm scale (P4) from etches, a re-run of an older kit. I did the chassis with a simple compensation arrangement; one fixed axle, one rocking on a centre pivot, with that axle moving in hornblocks. It was a rod-driven chassis, but no valve gear. A bit of ingenuity got the motor and gearbox inside the boiler/firebox.
DCC decoder and stay-alive below footplate, between the two axles and the gearbox. It runs really well.

 

[Ian@StEnochs]

Mark,

On little 4 wheeled engines, especially slow moving ones, simple compensation is all you need to ensure all wheels touch the rails at the same time and give good current pickup and road holding. A fixed driven axle and the other rocking with a centre pivot. I assume as it’s a Sentinal the wheels will be coupled by chains.

Ian.

 

[Marc Dobson]

It's a "Toby" loco. Drive is through normal rods. It's going to be RC so issues if pick ups don't exist. My S7 version has no compensation at all and runs fine. But the G1 version is still on the drawing board or should I say the chassis is as the top is a 3D print that was already drawn in 7mm and blown up to G1.

 

[David Halfpenny]

It's a "Toby" loco. Drive is through normal rods. It's going to be RC so issues if pick ups don't exist. My S7 version has no compensation at all and runs fine. But the G1 version is still on the drawing board or should I say the chassis is as the top is a 3D print that was already drawn in 7mm and blown up to G1.

It all depends of where your father wants to run it, Marc.
If he wants the flexibility to run on other people's layouts, then compensation is advisable.
If he has a billiard-table indoor layout, you needn't bother David

 

[Marc Dobson]

It's going to be run on a small outside layout. Which is pritty flat. So horn blocks on one end and fixed on the driving axle.
Marc

 

[Nigel Cliffe]

Your alternative to hornblocks is a bearing beam - essentially a coupling rod with wheel-bearing holes. One end around fixed axle (one each side) and other end to carry the floating axle, frames have an oversize slot to allow axle to move. Still requires the centre pivot for the floating axle.

Depending on tools and available materials, it may be simpler.

 

[Marc Dobson]

Sounds good where would I get my hands on some photos so I can draw something up?
Marc

 

[Nigel Cliffe]

If you mean the bearing beam - look at some of the etch designs which Michael Edge produces (Judith Edge brand), he's a regular user of such components in 0-4-0 locos. But, they're trivially simple, start with the outline of a coupling rod, add oversized ends to take a wheel bearing (without altering the hole centres). The width of the part is "whatever fits the space", though I suggest at least the axle diameter wide. Thickness is "whatever material you are using".

 

[Bill Campbell]

Sounds good where would I get my hands on some photos so I can draw something up?
Marc

Hi Marc

Nigel just beat me to it with a mention of the arrangement in the Judith Edge kits. Here is an extract from the instructions for a Barclay Class 06 showing the suspension arms - one each side of the chassis behind the main side frames. Additionally I used a tube sleeve over the compensated axle to reduce friction. For the shorter chassis of your tram with no jackshaft I would reverse the position of the pivot point and place it just to the right of the fixed axle position in the drawing. The part labelled 70 is a retainer to keep the suspension arm against the inside face of the chassis.



Regards.

 

[Marc Dobson]

I have never.built one of mike's kits before. So am I correct in saying the rocking axle has a slot rather than a hole in the frames and the bearing is soldered to the rocking arm? And the rocking arm is then pivoted of a rod running across the frames?
Marc

 

[simond]

Or see here

Post in thread 'OEM workbench'
OEM workbench

 

[Nigel Cliffe]

I was thinking simpler than Marc, arguably simpler than Simon, roughly this:

Fixed axle at right, rocking axle on left. Bar (floating) is attached to a suitable cross-member to provide rocking fixed point for LH axle. The two dumb-bell shaped parts have axle bearings in their round holes, and can move independently of the frames (frames are the transparent rectangles). Slot for LH axle allows LH axle to move freely. If necessary to clear cross-members, the dumb-bell part can be irregular in shape, so long as it holds the wheelbase constant.

 

[Marc Dobson]

That was what I was thinking.
To the drawing board.
Marc

 

[simond]

Thanks Nigel, your approach makes sense for an 0-4-0, my sketch was intended for an 0-4-2 (14xx) so the central pivot is superfluous. I was thinking that the arrangement of axle bearings might help Marc.

 

[Marc Dobson]

Would a cross beam linking the arms benefit anything?

 

[Nigel Cliffe]

Would a cross beam linking the arms benefit anything?

Not really, other than to stop them flopping inwards. They need to be able to move up/down independently (the free end doing the same job as a hornblock), so better to have a simple staple or tab on each frame to stop the wondering inwards, but not to restrict their up/down movement.