Bedtime Story/Something for the Winter?
Posted: Wed, 21 Oct 2009, 9:43 pm
Many years ago, long before we bought our Ansfold, I was following a car towing an old caravan on a dual carriageway in the right-hand lane, approaching a roundabout. I'd just noticed the 'van's offside wheel wobbling, when the wheel came off altogether & the right side of the 'van hit the road! Its folded rear corner-stay made an excellent tarmac planer, digging in & bringing the remains to a shattering halt in the middle of the right-hand lane. I just managed to swerve in time to avoid a very close check of their internal decor!
Not much of a 'story' really, 'cos it actually happened. I was servicing a trailer at work today, & the hub design brought the above to mind.
Trailer & caravan hubs all use adjustable taper roller bearings these days. The adjusting nut cannot be tightened, as this overloads the bearings. The nut is locked with a split pin. When this construction is used on car hubs, there is always a keyed washer behind the nut, so bearing rotation can't be communicated to the hub nut. I don't know of any civilian trailer axles which have this keyed washer; certainly ours have not.
When I overhauled my axle, I drilled out the 9/64" splitpin holes to 11/64" & used a bigger pin. I also opened the pin in the 'aircraft' way, i.e. both legs bent round the nut & tucked in the adjacent castellations. This has a better shearing-resistance.
The accident described was caused by the nut either having been overtightened & the bearings failing through heat, or (more likely) normal rotation of the outer bearing on the stub-axle shearing a weak splitpin.
The 'van was a write-off, & it had taken root in the road in a very dangerous situation. Don't let it happen to you.
Steve Lord
Not much of a 'story' really, 'cos it actually happened. I was servicing a trailer at work today, & the hub design brought the above to mind.
Trailer & caravan hubs all use adjustable taper roller bearings these days. The adjusting nut cannot be tightened, as this overloads the bearings. The nut is locked with a split pin. When this construction is used on car hubs, there is always a keyed washer behind the nut, so bearing rotation can't be communicated to the hub nut. I don't know of any civilian trailer axles which have this keyed washer; certainly ours have not.
When I overhauled my axle, I drilled out the 9/64" splitpin holes to 11/64" & used a bigger pin. I also opened the pin in the 'aircraft' way, i.e. both legs bent round the nut & tucked in the adjacent castellations. This has a better shearing-resistance.
The accident described was caused by the nut either having been overtightened & the bearings failing through heat, or (more likely) normal rotation of the outer bearing on the stub-axle shearing a weak splitpin.
The 'van was a write-off, & it had taken root in the road in a very dangerous situation. Don't let it happen to you.
Steve Lord