What happens if you dont look after your kingpins!!!

Post by **AndrewSkinner** » Wed Oct 24, 2007 9:54 pm

I gues you all know about the kingpins in the morrs and how they can sometimes have a tendancy to just give up! well in my friends mini this is excactly what happened!!!

After the kingpin gave way the mini lost control crashed into the side of another car and then finished up in the gravel!!

see the pics here!

* Lesson * look after your kingpins!!!! lol

http://www.flickr.com/photos/8435833@N0 ... 676417983/

Post by **Matt** » Wed Oct 24, 2007 10:07 pm

Thats one of the balljoints giving up then... :s

Post by **dunketh** » Wed Oct 24, 2007 10:39 pm

I already learnt this lesson the hard way, when a wheel came off my own car!

Luckily I was only moving slowly, pulling in to get petrol at the time.

Post by **bmcecosse** » Wed Oct 24, 2007 11:12 pm

Must have hit something hard to pull BOTH the ball joints out like that! But if the Mini was run too low (although the bump stop is present) then the top joint is articulated further than designed - and as in the pics - it pulls the cap over the ball! I assume then the forces during the accident were sufficient to also wrench the lower joint apart. Poor maintenance (and possibly poor quality parts) don't help.

Post by **AndrewSkinner** » Wed Oct 24, 2007 11:42 pm

I think what also contributed to the probelm was the fact that he was running wider wheels and had large spacers on them all of which increase the load on the steering/suspension unit.

Everything was original (Nothing had been upgraded strengthened) and he liked his fast corners!

It is also his first classic and was not it very good shape when he bought it! the previous owner had done a very dodgy 'restoration' with no maintanence aswell it all added up to that!!!

lol main thing everyone was ok and its all covered by the insurance!
Now i see why youngsters have to pay so much

Post by **MoggyTech** » Thu Oct 25, 2007 12:15 am

Can someone explain to me how/why the Moggy trunnions sometimes fail. I know about regular maintenance like greasing etc. What is confusing me, is it seems to be the lower trunnion that fails? Considering this is screwed onto the kingpin, and then the lower fulcrum pin goes through the trunnion, and sits in a recess on the kingpin, plus the full weight of the front of the car is pushing the kingpin down into the trunnion, so how on earth does the kingpin pop out?

I've also read it seldon happens at speed (thank goodness), and usually when turning at a junction etc. So does something snap, or does the kingpin just do a magic act, and leap out of two inches of trunnion thread?

Glad the young lad is Ok, shame about his Mini

Post by **dunketh** » Thu Oct 25, 2007 10:28 am

Looks like a whole host of factors just added up to a bad result in the case of the mini.
Bad luck exacerbated by everything already mention. Plenty of minis run wide wheels and plenty run 'sat on their belly'.

Can someone explain to me how/why the Moggy trunnions sometimes fail.

Wear. Simple as. The kingpin is constantly rotating against the trunnion collar. Its going to wear it down eventually. Greasing prolongs this but they can't last forever.

the full weight of the front of the car is pushing the kingpin down into the trunnion, so how on earth does the kingpin pop out?

Ahh. but thats incorrect. The full weight of the car is not pushing down on it.
The dampers take some of the load as does the rest of the suspension.
The force that is the 'bad guy' in this equation is the downwards force of the torsion bar. The torsion bar is continually trying to pull the bottom arm downwards towards the road. The only linkage between the bottom arm and the kingpin is that little collar.
Going over a road bump at slow speed can make the car sail 'upwards' with the energy of the impact whilst the torsion bar is still pulling downwards. This is the highest moment of stress where both components are literally trying to pull themselves apart. Coupled with excessive wear its a recipe for disaster.

Of course, properly maintained trunions will never fail as you'd spot the wear before it got to dangerous levels.
(I can't really talk here, I've had one fail

)

Post by **MoggyTech** » Thu Oct 25, 2007 11:11 am

Hi Dunketh

Thanks for the explanation, it kind of makes sense now. Would also explain why it seems to happen at low speed (thankfully.)

Hmm no play in my KP's or trunnions but they have been on there since the last resto in 1997, running 185 tyres on Alloys that are slightly heavier than a standard road wheel.

Post by **dunketh** » Thu Oct 25, 2007 11:16 am

It bugs me that Morris didn't fit a vertical link bar, between the lower arm and the damper arm.

If there was such a bar holding the two arms parallel it would make it impossible for the trunion to separate regardless of how worn the parts were.

Post by **MoggyTech** » Thu Oct 25, 2007 5:19 pm

dunketh wrote:It bugs me that Morris didn't fit a vertical link bar, between the lower arm and the damper arm.

If there was such a bar holding the two arms parallel it would make it impossible for the trunion to separate regardless of how worn the parts were.

Interesting you should say that. I was doing some front end work today, and noticed that the Gas Shocks act like a link bar. With the supension at full stretch, there is only about 1/4 inch of travel left in the Gas Shocks.

As the kingpin has to pull out of the trunnion by a couple of inches, I'm hoping that the shock absorber would limit the travel and prevent collapse?

Of course I will still grease the trunnions every 1,000 miles and check for play etc, but perhaps the shock absorber mod also adds a bit more safety

Post by **rayofleamington** » Thu Oct 25, 2007 5:57 pm

No extra parts needed to prevent total failure ->They could have added a big lip on the back of the brake backplate, that would prevent the trunnion coming off the kingpin if the thread fails - unlike the actual backplate which only prevents you unscrewing it when everything is ok.

They did 'try' to make it more safe by ftting the fulcrum pin into a groove on the torsion bar, however as the groove is only as deep as the threads, it doesn't work if the threads are completely shot

Post by **RogerRust** » Thu Oct 25, 2007 6:34 pm

I understand 9 inch wolseley brakes have this lip feature!!!!

Ha Ha

Post by **MoggyTech** » Thu Oct 25, 2007 6:40 pm

rayofleamington wrote: They did 'try' to make it more safe by ftting the fulcrum pin into a groove on the torsion bar, however as the groove is only as deep as the threads, it doesn't work if the threads are completely shot

Now I am really confused. Do you mean groove in the kingpin? If the fulcrum pin ever meets the torsion bar I will be really worried

Post by **MoggyTech** » Thu Oct 25, 2007 6:42 pm

RogerRust wrote:I understand 9 inch wolseley brakes have this lip feature!!!!

Ha Ha

You know I needed a laugh, and that hit the spot

Wolseley brakes seem to create quite a bit of lip

Post by **d_harris** » Thu Oct 25, 2007 7:51 pm

I think the word is Ouch!

Looks like he did quite a good job of it. At least he is ok though. Thats the main thing

Post by **bmcecosse** » Fri Oct 26, 2007 6:01 pm

Indeed - the bigger backplate of the W (or R) backplates DO stop the kingpin parting company with the trunnion - as do teledampers (I'm sure I have mentioned this in the past) - but a flexible link could be fitted - the rear suspension rebound strap from an MGB springs to mind as a possible candidate.