Kingpin securing cotter

[Adrian Payne]

Hello All
I am aware that this cotter has to be tight to prevent the kingpin moving in the axle eye.
Question is how tight. If constantly checking there is a risk of over tightening as others have done with halfshaft nuts until they shear.
What torque would you recommend remembering that this is a wasted cotter.
Many thanks.
Adrian.

[Peter Johnson]

My father has always used a high tensile cap head screw which has been machined down for the purpose. Instead of using a round cut out, it has a ramp machined into it. All our collective sevens have the same configuration including two trials cars.

Unfortunately I have no photos. But the high tensile screw gives some confidence because you know that a reasonable torque can be applied.

Peter

[bob46320]

its only a 5/16" BSF nut. I rely on a moderate tap with a hammer from the other side from the nut and apply a moderate torque to the nut. I would not rely on the nut to do all of the work.

[Bob Culver]

In theory the kingpin is supposed to be a good interference fit but often dubious. Very tight cotter can bow pin and make close reamed bushes tight.
I cannot immediately find one but presumably the cross section is not much smaller than the thread root, the weak part. The thread torque applicable the material should apply. The pins are supposed to be HT, presumably about 45 tsi as per ht hardware, but there have been a myriad kits and may be mild steel.. Cap setscews are usually very high tsi.

[Stuart Giles]

its only a 5/16" BSF nut.  I rely on a moderate tap with a hammer from the other side from the nut and apply a moderate torque to the nut. I would not rely on the nut to do all of the work.

Any other way of dealing with this issue is a sure recipe for having the thread strip long before the cotter pulls up really tight against the pin.

I have always kept the Austin style cotter rather than use the ramp type with a home produced cutout in the factory style hollow pin -there isn't much metal there once a cutout has been introduced on a standard pin. if I was using solid pins I would choose the ramp style cotter -but there isn't much room at the base of a Girling stub to install the second grease nipple that this setup needs though.

[Bob Culver]

Broken kingpins are far from uncommon, some brands especially. it is essential no cutouts in the pin. I gather some have used ht chrome plated rod. Other makes use pins not fully hardened. But with these care necessary not to spread the pin and hugely complicate removal. Lester Reader, owner of the Rubber Duck, and later one of NZs most renowned special builders used "silver steel" as supplied for his (low mileage) competition special.