Scalefour Forum

I'm assembling a couple of MJT torsion bar CCUs and the instructions say just hold the bearings in with blue tac durng assembly. Anyone have any suggestions as to why the bearings are only held in by pressure, rather than being soldered into the relevant holes?

Seems to be in order to allow the builder to check whether the bearings need any washers or not to get the axles held between the side frames without any slop:

8) Place the axle bearings and the wheel sets in position in the correct
bearing holes (Blu-tack will hold the bearings in place temporarily) and
check that the axles are held with little slop (a fibre washer between the
bearing and side frame should correct this if necessary). Hold the two
side frames together, and in line, with a piece of masking tape. When
you are satisfied that the axles are under the correct tension, solder the
torsion bar to the second side frame, again on the inner face of the outer
edge. The masking tape may now be removed.

From: https://www.dartcastings.co.uk/resource ... ctions.pdf

Not sure I understand this. The position of the side frames is not fixed UNTIL the axles and wheels are set without slop, only then is the p[osition of the side frames fixed by soldering the ends of the torsion bar. The side frames can be moved in as far as is necessary to grip the axles without washers BEFORE their position is fixed. I'm not clear how leaving the bearings loose assists this process as the more fixed elements in the side frames the better as far as accurate positioning is concerned.

I can't help any more with this, sorry, other than to agree with what you say...

I solder the bearings into the side frames before setting the whole thing up (as per the instructions).

An additional comment. I have found that the pop studs used in later (and possible current) CCUs tend to have a square cross section in the male part which prevents smooth rotation of the CCU/bogie. I have filed the square corners with an round escapement file to ease this but more recently changed over to the Brassmasters units which are fitted using a set screw and nut.

Thanks for these inputs. I think will solder the bearings in first. I won't be using pres-studs though.

The press studs on the MJT bogies is not the only issue. We have been this way before, have you read the "Suspension for bogie coaches" thread, the relevant bit starts here