Uprated Trailing Arms

[Boost All The Dollys]

Anything over 250bhp and you'll be looking for a different axle too as that's about the limit of what a Sprint unit can handle.

Im not sure that rose joints won't provide a little too MUCH articulation and force you to adopt a Panhard rod to control axle sideways location adequately.

If I was to be designing such an item (with KISS as my guiding principal) i'd keep the tubular bushes at each end and merely replace the pressed arm with a nice strong bit of tube, a U bracket welded to it to support the shock mount and some sort of drop plate for the ARB if you keep it. The main thing to get rid of, if practical, is the "kick up" at the axle end which introduces the fatal stress point.

Whilst most failures of the originals are probably overload induced, it's by no means exclusive. A couple of years ago, I changed one out that had failed on a 1500 auto, you'd be hard pushed to find one LESS stressed than that! Old age and corrosion were the culprits in that case. The failed trailing arm was only the thin end of the wedge on that car, I don't think i've EVER seen a Dolomite quite so rotten that was still in regular use, nor one with SO many patch repairs! It was scrapped shortly after, as it's chances of another legit MOT were effectively zero.

Steve

It wouldn’t need a pan hard bar as the centre bars provide the lateral movement prevention.

Thinking about it last night and the design you described is what I was thinking would be best.

And wow, that must have been one very shot trailing arm if it failed on that.

I just think that if it’s a known failure point, maybe it should be looked into

[Boost All The Dollys]

After a bit of searching, I found some spherical bearings which would give the necessary articulation to let the trailing arm rotate but it’s still a hard mount without making a new arm, although it may cause a higher direct stress level in the arm due to forces being applied to it being applied instantly rather that gradually with rubber, it would reduce the torsional stresses that appeared to breach the arm coming from the rubber/polybush having a spring effect.

To make the existing arms stronger, maybe plating the arm between the shock mount and the axle mount could reduce the chance of the arm folding up there, maybe plating further up the arm would stop the arm from completely collapsing.

As for the he forces being transferred and breaking other things, the forces aren’t increased by going to hard mounts, they are more instant and probably reduced due to the fact there’s no “spring” forces from the rubber under twisting.

[new to this]

if you wanted to give more strenght you could box in the top edge, but you would need to put in some captive nuts if your going to still use the anti role bar

Dave