A while back I reviewed the DJM J94, and came to the conclusion for me that it was a bit ‘meh’, I know, I know, that sayings ‘so last year’ now! The review is here djm-j94 Since then the model has been sitting on the shelf of doom, but working on a small industrial project I thought it may be time to look at it again. Common with the DJM/Hattons 14XX the J94 has a fully geared chassis, so the coupling rods are only cosmetic. Both types have the unfortunate characteristic of ‘cogging’ under load on a descending gradient. This is the J94 (this one) on a 3% gradient youtubeJ94
This appears to be a common issue, I’ve run seven of these J94’s with the same result. I’ve largely resolved it on my 14XX with some open chassis surgery removing part of the drive train, and replacing the coupling rods 14xx-frustration.
Well I’ve decided to try a similar solution with the J94. Initially I removed the coupling rods to no improvement. Next was to get into the chassis, and like the 14XX before it, the task was squarely in the PITA category. If the end game works I’ll write it up! The heading picture shows the model and four gears, those have been removed from the gear train, so it is a simple worm to tower geared drive system.
So the results so far. Under load downhill with no rods, almost imperceptible cogging, there is still some, and that will be due to the mesh of the worm to the top gear.
Uphill with no rods the loco slips, in the original review the lack of weight was noteworthy for me.
Replacing the rods (with originals) the loco again cogs downhill, they’re rigid rods, and climbs with no problem under load. On the flat there’s no difference to when the model was fully geared. Wheels in all cases are self quartering due to square stub ended axles.
Next job is to replace the rods with prototypical knuckle jointed rods and see if that nips the cogging problem in the bid. I hope it does, overall (apart from the mechanism), the models a reasonable starting point for a detailing and weathering project. If you have a flat earth society layout, I suppose it still is…